Wednesday, September 24, 2008

Using Lego to integrate Mathematics and Science in an Outcomes Based Syllabus



Using Lego to integrate Mathematics and Science in an Outcomes Based Syllabus.
Stephen Norton
QUT



Abstract


Integrated learning has been put forward in curriculum documents as a means
to add meaning and context to mathematics and science learning. However,
few models of practice exist to guide teachers’ in implementing this process.
This paper examines an educational researcher’s and a practicing teacher’s
challenge to use student construction of Lego artefacts as a tool for the
learning of mathematics and science concepts through technology practice. It
was found that the activities afforded opportunities for students to
demonstrate numerous outcomes, that explicit scaffolding was needed by
some students and that some students achieved at outcome levels beyond
those expected of their Year. The findings have implications for the use of
activity in the teaching of mathematics and science where syllabus
documents demand specific outcomes.



Introduction


Papert, (1980) coined "constructionism" and defined it as "Giving children good things to do so that
they can learn by doing much better than before." What Papert had in mind was that children could
learn mathematics effectively by building artefacts and programming simulations. The work of
Vygotsky (1987) and von Glaserfeld, (1987) have further informed the move towards viewing
knowledge as something that individuals construct via interactions with the environment and the
learning paradigm they described was termed "constructivism". Thus, in essence, constructionism is
an extension of constructivism in that like constructivism it emphasises the building of knowledge
structures, but then adds to this that the learner is learning in a context of constructing a public entity
(Papert & Harel, 1991).



The American Association for the Advancement of Science (1993), through Project 2061, actively
promoted the inclusion of technology in the school curriculum and also recommended that technology
could be used as a vehicle for learning science and mathematics. Likewise there has been a shift in
mathematics teaching and learning in the last two decades towards increased emphasis on powerful
ideas associated with mathematical processes (Jones, Langrall, Thorton, & Nisbet, 2002). National
Council of Teachers of Mathematics (NCTM) Standards (2004) has encapsulated this trend world wide
by giving pre-eminence to five process standards: problem solving, reasoning and proof, connections,
communication and representation. This shift in curriculum approach towards communication of
reasoning, contextual problem based learning and integration (both within the subject domain and
across subjects) has found expression in attempts to integrate science and technology with
mathematics. For example, the New Basics curriculum documents (Education Queensland, 2001) has a
strong emphasis on integrated learning. This document encourages teachers to use integrated
community based activities, where the role of the teacher is one of mentoring while students engage in
tasks that are relevant and authentic to the students. Other curriculum documents have recommended
an approach to mathematics teaching and learning that is integrated or transdisciplinary and where the
mathematics is embedded in authentic contexts (e.g., Queensland Studies Authority, 2003). The use of
authentic contexts tends to enable students to develop modelling capacities that need greater
mathematizing and the conceptual use of mathematics (e.g., Nason & Woodruf, 2003).



Part of the reason for the integration of mathematics and science is the perception that falling student
enrolment in "hard sciences" can be attributed to the isolated and fragmented curriculum where
students see these subjects as not relevant (Malcolm, 2002).
McRobbie, Stein, and Ginns (2001) have
suggested that science set in a technological setting is worth examination since technology is part of the
world lived in and experienced by students. Papert and Harel (1991) recommended Lego construction
combined with programming (Lego Robotics) so that students could engage in the building of active
models. In contrast to the view that students ought to construct knowledge, is that students can learn
effectively from direct instruction where the teacher’s primary role is to deliver careful explanations
that take account of cognitive load (e.g., Cooper, 1998; Pollock, Chandler, & Sweller, 2002).



Several studies (e.g., Bergen, 2001; Mauch, 2001, McRobbie, Norton, & Ginns, 2003)
have reported the strong motivational potential and development of problem solving
strategies through working with Lego Robotics. In addition, Levien and Rochefort
(2002) commented on Lego Robotics as a suitable medium to explore engineering
principles with tertiary students. Recent research into Lego Robotics in middle school
years indicates that many opportunities for extracting science and mathematics
principles from technology-based activities are not capitalised on, the science and
mathematics remaining implicit (e.g, McRobbie, Norton & Ginns, 2003). A particular
concern has been teachers’ difficulties in making the links between the technology
activity of Robotics and other syllabus outcomes. McRobbie et al, (2003) also showed
how the programming feature of Lego Robotics had the potential to absorb most of
the students’ problem solving endeavours and thus the science and mathematics
associated with the construction and mechanical operation of the robots became a
secondary concern of both students and teacher.



The mixed results of using Lego Robotics as a medium for the learning of science and
mathematics has prompted this research to investigate the potential of using Lego
construction as a tool to facilitate science and mathematics learning within the context
of technology practice, without programming. Of particular interest was what types
of scaffolding needed in order for students to learn science and mathematics. Thus
this paper focuses on the planning for learning, enacted pedagogies, types of student
outcomes and assessing student learning.


Design and Methods


The method used is participant observation. A rationale for this method is described
by Glesne and Peshkin (1992, p. 39):



Through participant observation, through being part of the social setting – you
will learn first hand how actions of your and others correspond to their words,
see patterns of behaviour, experience the unexpected, as well as the expected,
and develop a quality of trust with others that motives them to tell you what
otherwise they may not.



In this process of participation the researcher and the usual classroom teachers
collaborated in planning, while the researcher taught most of the 2 hours lessons over
a 10 week period as an intervention. Prior to beginning the intervention the researcher
and Jill (main collaborative teacher) matched science outcomes (Queensland School
Curriculum Council, 1999) and mathematics outcomes (Queensland Studies
Authority, 2003) with construction activities related to the "Simple and Powered
Mechanisms" kits (Lego Educational Division, 2003) that were designed to help
students learn engineering concepts. The kits contained a motor, various cogs and
pulleys, various blocks, axles, connecting pieces as well as instruction booklets.



Subjects:


The subjects were 46 Year 7 students in two classes in a State middle school in
Brisbane. The school was a trial school for New Basics Curriculum (Education
Queensland, 2001) that attempts to integrate the teaching of subject domains of
science and mathematics through authentic project based tasks. The classroom
teachers were also part of the study. Jill and Tony (all names are pseudonyms) were

experienced primary school teachers who had a passion for science. Unfortunately,
Tony replaced the original classroom teacher of the second class half way through the
study, thus Jill was more involved in the planning and evaluation and the balance of
evidence reported reflects this situation.



Data collection


The collection of data included a reflective journal written by the researcher and on
going tape-recorded interviews with the teacher and student construction and
presentations as well and digital photographs of artefacts. In addition, the students’
interactions with objects, peers and teachers, student planning and construction of
artefacts, and their explanations of how things worked were recorded on video tape.
Students’ artefacts including their planning sheets, written explanations and their
explanations on written tests were also collected. In the second week of the study the
students were given the task of planning and constructing an artefact that either served
a practical need or modelled a useful product. At the end of the study students
repeated the planning and construction activity. Students’ plans and artefacts were
compared. The students were also given pre-intervention and post-intervention pencil
and paper tests on science and mathematics concepts. Throughout the study the
teachers acted as observers and documented student activity that indicated an outcome
had been met.



Analysis:


A hermeneutic cycle (Guba, & Lincoln, 1994) was employed in developing and
testing assertions as the study progressed. Emerging assertions were discussed with
the teacher and colleagues and tested and refined in the light of further evidence. The
video and audio records of activity and interviews were listened to and key elements
transcribed and categorised according to emerging assertions. Triangulation involved
the use of multiple data sources identified above and this maximised the probability
that emergent assertions were consistent with a variety of data.



In seeking an analytic frame to help the assessment criteria the author used the Payne
and Rathmell (1977) triangle that shows two way interactions between representations
(concrete and pictorial), language and symbolism. To guide the assessment process
the author devised a series of indicators associated with each outcome. For example,
in relation to the mathematics outcome associated with ratio Level 5 "Students
identify and solve multiplication and division problems involving positive rational
numbers, rates, ratios and direct proportions using a range of strategies" (QSA, 2003,
p. 21 the following indicators for ratio were developed:




  • Level 4: Students construct gearing but can not articulate the relationship that
    exists in terms of magnitude (e.g., "The motor is connected to the gears which
    makes the wheels turn"). This statement does not attempt to describe the
    relationships that exist between the gear sizes nor how this effects their
    functioning. In essence the student’s understanding is confined to the concrete
    level and this is reflected in the language used. The statement does not give
    explicit recognition to the concept of ratio.


  • Level 5: Qualitative explanations: Students construct appropriate gearing and
    can explain it in qualitative terms (e.g., "The small driver goes around lots of
    times and this makes the bigger follower go around a few times, this is good
    for power"). In this instance the student was able to articulate the nature of the
    relationship in terms of direction and magnitude but only in a qualitative way.

    There was evidence of stronger understanding of the concrete representation
    and the connections between concrete representation and language reflect this.


  • Level 5: Quantitative explanations: Student has used the gearing and can
    explain it in a quantitative way (e.g., "The drive has 8 teeth, it needs to go
    around 5 times to make the follower with 40 teeth go around once. This is
    good for a tractor to pull loads"). In this example, the connections between
    the material model, language and symbolism are all present and the nature of
    the relationship is accurately described quantitatively. This would indicate
    relational thinking (Skemp, 1978).


  • Level 6: Students have used gearing in a novel problem solving context that
    illustrates understanding and can explain it in a quantitative way. Students
    who use a series of gears to amplify the effect of gearing is one such example
    and can quantity this relationship would be and example of this. Thus,
    construction and explanation illustrate the students can correctly connect the
    representations, language and symbolism associated with ratio concepts.


The mathematics Level 6 indicator above was developed for the outcome statement
Students identify and solve multiplication and division problems involving rational
numbers, rates, ratios and direct and inverse proportions using a range of
computational methods and strategies," (QSA, 2003, p. 22). Similar frameworks
needed to be developed to assess science based thinking.



Results and Analysis


The results are presented as a series of assertions followed by supporting evidence.



Assertion 1: Construction activities give the potential for students to achieve many learning outcomes
in science, mathematics and technology.



In the process of identifying those outcomes that might be developed through the construction activities
the researcher constructed from the Lego plans various levers, pullies, draw bridges, conveyor belts,
drummers, model windscreen wipers, cars, conveyors, merry-go-rounds, turnstile, crane and worm gear
winch. What became apparent was the great amount of mathematics and science understanding
underpinning the construction and explanation of the operation of these artefacts. This work lead to the
identification of syllabus outcomes associated with the Lego activities. In the current Queensland
Syllabuses outcomes are expressed at levels from one to six. One being entry to school level, level 3
outcomes ought to be demonstrated by the end of Year 5, level 4 outcomes at the end of Year 7 and
level 6 outcomes at the end of Year 10. Some focus outcomes are presented in table 1 below. There
were numerous outcomes associates with the activities in the Science Syllabus (Queensland Schools
Curriculum Council, 1999) within the strands of science and society, energy and change over a range
of levels from level 2 to 6. Similarly, in the Mathematics Years 1 to 10 Syllabus (QSA, 2003)
activities were matched to outcomes in the strands of number, patterns and algebra, measurement,
chance and data and space, again across a range of levels. The technology embedded in the activities
was mostly in the strands of technology practice, materials and systems within the Technology Years 1
to 10 Syllabus (QSA, 2003).



Table 1

Sample of syllabus outcomes related to construction activities















Mathematics

Students identify and solve multiplication and division problems involving whole
numbers, decimal fractions, percentages, rates, selecting from a range of
computational methods, strategies and known number facts (Number 4.3).
Students analyse experimental data and compare numerical results with predicted
results to inform judgements about the likelihood of particular outcomes (Chance and
data 4.1).

Science

Students collect and present information about the transfer and transformation of
energy (including potential and kinetic energy, Energy and Change 4.2)

Technology

Students generate design ideas through consultation and communicate these in
detailed design proposal (Technology Practice 4.2)



Clearly, the proposed activities provided a rich opportunity for students to demonstrate achievement of
a number of core learning outcomes identified in the three syllabus documents. The problem for the
researcher and Jill was in deciding how to plan, carry out lessons and assess learning such that
outcomes might be documented. Faced with the almost overwhelming planning task of integrating the
outcomes Jill commented:



I guess I am lucky that I am a fairly experienced teacher and I know a fair bit of
science, other wise you would not know what science was in the construction. I do
not think that everyone has that love of science and maths and it is extremely
important (in order to integrate the two).



That is, Jill considered many teachers would not find it easy to link syllabus outcomes with the
construction activities. She commented on the researcher’s teaching plans with respect to the focus on
particular outcomes.



When I do my planning I specifically think of what major point I want to get across
to my kids? What do I want every child to understand? I have to decide what is
pertinent to Year 7 and at what level do I need them to understand. Then before the
actual lesson can begin you have to recap the information that is needed. This can be
a real problem because not everyone in Year 7 is up the "correct" level. I have to test
them first to see where the gaps are and then I have to teach at a Year 7 level but
scaffold the less able students more. I have to help them with the underpinning
knowledge that is missing.



Both the mathematics and science syllabuses (Queensland Schools Curriculum Council, 1999;
Queensland Studies Authority, 2003) are spiral curriculum documents that assume prerequisite
outcomes have been attained. In fact, it may well be argued that they reflect the notion that
mathematics and science are structured and hierarchical bodies of knowledge. Thus, in the sequencing
of outcomes reflect an image of knowledge consistent with Ernest’s (1991) view of mathematical
knowledge as a set of truths and body of structured knowledge consistent with absolutist images of the
nature of mathematics and usually associated with instructivist (Cooper, 1998; Marsh, 2004) teaching
practices. Essentially the same view was described by Galbraith (1993) as the "conventional
paradigm." This view is in contrast to fallibist images of mathematics and science usually associated
with constructivists pedagogies. For Jill this created a tension. She acknowledged that the way current
syllabus documents were enacted was not motivating many students, but at the same time the structure
of the syllabus needed to be reflected in teaching.



They hated it because they felt that they were no good at it (mathematics), and it was
boring. But, on the other hand, many kids in this group need the structure.
Somewhere along the line they have missed out on the structural approaches to all
the concepts including fractions for example.



This statement reflects her view that many students had experienced predominantly instructivist
pedagogy that fostered a negative image of mathematics and science and affected their ability,
however, at the same time she acknowledged that students had missed explicit structuring that they
needed in order to understand difficult concepts. In attempting to account for the need to provide a
focus for student learning so that essential scaffolding was afforded to students, the researcher and Jill
decided to focus on the concept of ratio that had been identified as challenging (e.g, Lamon, 1995),
and science concepts associated with energy and change. Consequently, the lesson planning and
implementation refected this focus.




Assertion 2: Scaffolding in the form of explicit details was needed for some students to make links
between activities and outcomes.



In the early lessons the researcher adopted a relatively unstructured construtionism approach to teaching,
in that the students were asked to construct various artefacts (e.g., "make me a car that can go fast") and
he attempted to hold class discussions towards the end of the lessons to make explicit the underlying
mathematical and science concepts. This approach was an attempt to have the students demonstrates
level 4 of technology practice and level 5 mathematics explanation of ratio. Lesson observations
indicated that to a considerable degree this approach lead to less able students becoming frustrated and

the class discussions were dominated by the few students who had the prior knowledge to link the
activity of construction explicitly to the science and mathematics. In behavioural terms this was
manifested by a few students engaging in off task behaviour and others expressed bewilderment and
disenchantment as one less able student commented; "I just do not know what is going on." For other
students the activities offered an opportunity for cognitive conflict and rich learning. For example when
exploring levers one student commented:



It does not make sense, I am all muddled up". A see-saw is constructed with a
pivot, load and effort. The pivot is in the middle of the lever, but if it was closer, the
other child would go boong. If it was even, then nothing would happen. If the pivot
was close to a light child it would make an easier effort.



Such a statement illustrates an accounting of proportional thinking and the relationships between
leverage, mass and forces. Jill’s comment on the problem of students having different level of
engagement was:



The good kids understand it, but it (ratio) is a concept that needs to be teased out,
you have to bring it down to simplest terms, you have to have a diagram.



In essence what Jill was recommending was alternative representations (a diagram) to
accompany the concrete material and explicit scaffolding to focus students’ attention to the
links between the material models and the underlying science and mathematics concepts.
The researcher’s diary acknowledged the tension between construction and attempting to
teach to specific outcomes:



It is very difficult to use the Lego to set up the science learning, because you are
always struggling with the conflict of them wanting to build and you wanting to
formalise.



Over the course of the study Jill and the researcher consulted after each lesson and as a result of their
reflections and negotiations the pedagogy enacted by the researcher evolved. For example three weeks
into the project Jill commented:



You need to build in more structure, give them structure, but let them explore as well"The
higher end kids, they can do a lot of investigative work, but some in this group have missed out
so you need to simplify it. I did that with fractions, you know, I brought something in and we
would cut it up, a pie or a cake, whatever.



Following this advice, the author attempted to provide more structure in the lessons. The first 15 to 20
minutes of each lesson was spent clearly defining the purposes of the construction task. For example, if
the task was to explore the nature of ratio by having students design build and explain the gearing of a
tractor this task was made explicit and the students were provided with planning sheets to facilitate
their thinking about ratio. In addition, it was considered that the concept of ratio (pre-requisite
knowledge) ought to be revised in contexts that ought to have been familiar to them such as identifying
the ratio relationship present when there were 2 while balls and 6 green ones. The students were also
asked to reflect on ratios that they were likely to be familiar with in the course of their daily life such as
bicycle gears. Unfortunately, this was a "post activity" thought and the revision of ratio did not occur in
this study.



The author attempted to hold debriefing discussions at the conclusion of each class and this was used as
an opportunity to link the formality of science and mathematics outcomes with the construction
activities. Jill noted that student involvement in classroom discussion was "patchy, that is some
students consistently contributed to class discussion while other appeared disengaged." The author and
Jill agreed that in future investigations each group would be asked to give a class presentation
explaining their artefact and would be graded according to the scientific and mathematical thinking
they demonstrated.



Jill expressed her approval for a mix of board work with standard revision of concepts and practice on
ratio questions and construction of artefacts. While students worked in pairs or in groups of three to
design, make and explain, the author walked between groups and much of his scaffolding was directed
towards eliciting student explanations of their artefacts.



The practice of the formal setting out of mathematical problems was to happen in homework time or in
subsequent non construction lessons. Jill stated that although she believed this ought to happen, over
the life of the study it occurred to a very limited degree, simply because Jill had other curriculum

material to be covered in mathematics and science. This failure to utilise the homework time to support
the learning that occurred during the construction activities was noted by Jill and the author as a factor
that limited the potential to make connections between the activity occurring during the construction
and planning phases and specific outcomes in mathematics and science.



In conclusion, in catering for the needs of different students, teachers needs to be aware of students’
perquisite knowledge and provide the level of scaffolding that different students need in-order to
engage in concept related discussion and to forge the links between the various representations. Such
scaffolding includes clearly setting tasks requirements, class discussions based on student
presentations, a mix of board work and book work, the use of homework to revise concepts and
questioning of students about how their constructions operated. While such an observation has been
noted previously, in the case of technology mediated activities, appropriate scaffolding may take on
additional significance. Put simply there are more opportunities for students to be cognitively
disengaged and more ways to fail to make appropriate links between representations. On the other
hand, it could be argued that when learning within a technology practice setting there are more ways to
be cognitively engaged and more opportunities to make links between representations and thus develop
powerful understandings.




Assertion 3: Year 7 students are expected to achieve outcomes at level 4, but a number achieved at
levels beyond this.



There were two main ways the author attempted to assess and document student
learning. The first was via pencil and paper pre and post-tests on the mathematics and
science concepts under study. Some questions were simply definitions while other
questions required quantitative expressions of proportional reasoning to gain full
marks, for example:



Examine the diagram of pulleys (diagram included in script). If the circumference of pulley A
is 20 cm, the circumference of pulley B is 40 cm and the circumference of pulley C is 10 cm
and pulley B I spun twice, describe how pulleys A and C will spin. Explain why this will
occur.



The correct answer to such question would be an indication that the student understood ratio at level 5
(Quantitative). Other questions were more open, for example, students were given the number of teeth
on various gear cogs and asked to use their knowledge of bicycles to create a matching pair that would
help the bike go fast, and to give a possible explanation that would be correct and complete (level 6).
Scoring was on the basis of correctness and completeness of explanations, and each item was allocated
2 marks. Answers that had correct quantitative responses as well as their explanations were allocated
full marks. The results for the pre-test and post-tests for science and mathematics are presented in
Figures 1 and 2.




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Figure 1: Pre-Post Test Results in Science


f
The box plot gives a visual expression of the pre-test and post-test results for science, the pre-test
results being on the left and the post-test on the right. The box plots indicate that the median and in
particular top 75% of scores improved considerably. A number of students performed poorly in both
pre and post-tests. The paired samples correlation coefficient between pre-test and post-test results was
low, (r(42)=.30, p=.047) indicating that a high score on the pre-test was not a good predictor of
performance on the post-test for science.
Box plots of the mathematics pre-test and post-tests indicated that the scores were
generally higher in the post-test. The pre and post test results indicated that the pretest
score in mathematics was a reasonable predictor of the post-test score, (for
example r(34)=.64, p<.000).




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Figure 2: Pre-Post Test Results in Mathematics



As with science there were some students who improved in their rest results and some who made
minimal improvements on the test.



In the initial construction phase almost all student constructions did not take account of mathematics
principles such as ratio and science associated principles including friction and leverage (the exceptions
being those four groups of boys who had extensive Lego kits at home) and for all groups the
explanations were not connected to science or mathematics principles. For example, a pair of girls
constructed the following helicopter in week 4.




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Figure 3: Week 4 Helicopter



This helicopter has a simple direct drive to one set of blades. Their explanation of the
mechanics was as follows:



The motor makes the propellers go round and they make the helicopter work. The propeller on
the top gives off a large amount of wind and the helicopter nearly flies. The tail is for balance
and it has another propeller attached to it. When the ‘copter’ vibrates this propeller nearly turns
around, we are still re working it.



This description conforms to Level 3 of the Energy and Change strand of the syllabus
"Students understand the effects of forces on the shape, motion and energy of
objects." (Queensland School Curriculum Council, 1999, p. 79) but does not contain
evidence of mathematical outcomes. The figure below is a later construct.




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Figure 4: Week 8 aeroplane



The girls’ second artefact used a series of gears to drive both the propeller blades and
bevel gears to the back wheels of the plane "for taxiing up the runway." While able to
construct in a more sophisticated way their explanations on the working remained one
of describing the cause and effect and they did not try to quantify their explanation
not even to qualify the relationship in terms of more or less turns needed to drive a
following gear. In this regard, the explanation remains at level 3 and certainly the did
not show evidence of attaining level 5 of the number strand "students identify and
solve multiplications and division problems involving positive rational numbers,
rates, ratio and direct proportion" (QSA, 2003, p. 21). That is, it did not attempt to
describe the artefact in terms of rates or ratio and there was no evidence in the
students’ explanations that this concept had been developed over the life of the study.



The motor turns the shaft that turns the propeller, and the middle gear turns the
second propeller, which turns the axle which turns the wheels. The back gear is a
bevel gear. It is pretty slow. If the propellers could go fast it might fly, but it can’t.



The students’ explanation does not account for the science principles that are involved (force, friction,
& energy transformations) and the science outcome remains at Level 3. Thus, while the construct was
mechanically more sophisticated than the helicopter, their explanations of the artefact had not met a
higher outcome indicator.



Other students did account for science principles in their final artefacts. Three boys made a game of
shooting a target.




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Figure 5: Target shooter.



Their written explanation was as follows:



The target practice machine can be motorised or you can make it launch manually,
the missile is made of two small boxes and some teeth that grip onto the gear
connected to the motor. The flat surface allows a missile to slide and if it was
enough velocity it will shoot off and hit the target. The wall at the back stops the
missile as far back as it goes, where the missile stops it’s the fastest it can go.



This statement indicates a level of understanding at the level 4 of the science syllabus "Students
understand that there are different forces which affect the motion, behaviour and energy of objects."
(Queensland School Curriculum Council, 1999, p. 79). Their original explanations of the non
motorised quad chair was rich in a description on how it was made but not how it functioned, thus in
terms of science outcomes their explanation was level 3. The boys did not attempt to describe the
shooter in mathematical terms, they did not discuss the relationship between the diameter of the driver
cog and missile velocity or describe the trajectory in quantitative terms, such reasoning would have
equated to a level 5 outcome (QSA, 2003, p. 25);



Students identify when relationships exist between two sets of data and use functions expressed
in words or symbols, or represented in tables and graphs to describe these relationships that are
linear and express these using equations.



Some students improved markedly in their ability to explain their products in
mathematical terms. In week 2, two female students who had been identified by the
teacher as mathematically very capable had designed a car for all terrain travel. It
featured (Figure 6) the use of a simple pulley system to drive a four wheel drive
"tractor" using a 40 tooth cog gear for rear wheels to "help with grip."




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Figure 6: All terrain car, week 2.



The design illustrates that the students did not understand the relationship between
wheel diameter and circumference. When they tested the car, it would run on a desk
where slippage negated the lack of synchronisation between the front and back
wheels, but would not run on carpet where the front wheels acted as a brake on the
back wheels. In this instance the students did not recognise the significance of the
relationship between the different diameters and the distance each wheel would
travel. The misconceptions the students manifested in terms of circumference, rates,
ratio and direct proportion indicate that the students were operating at with error at
level 3 of the number strand. The critical issue here is they could not apply their
number skills to in this situation. (They had just recently demonstrated computational
competency in the attributes of circles, ratio relationship between diameter and
circumference, in their normal mathematics class. In this regard their mathematical
knowledge might be described as "instrumental" (Skemp, 1978). In contrast their

construction of a tractor in week 8 demonstrated a much better use of the concepts of
ratio (Figure 7).




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Figure 7: Low geared tractor, week 8.



The students’ description of a tractor several weeks later was an excellent display of
mastery of ratio.



The 8 teeth gear on the motor (driver) will turn the 40 teeth gear underneath it, (the
driver) will turn 5 times, then 8 gear on the same bar as the 40 teeth gear will also
turn 5 times, when the 8 gear turns 5 times, the gear with 40 teeth will turn once,
making the 24 teeth gear that is behind the wheel turn around about 1 and ¾ times.



The students were aware that the driver gear had to turn 25 times to effect an outcome of "about 1 and
¾ times," this is remarkably accurate. This explanation is consistent with Level 6 of Number strand
(QSA, 2003, p. 22):



Students identify and solve multiplication and division problems involving rational
numbers, rates, ratios and direct and inverse proportions using a range of
computation methods and strategies.



The students’ abilities to apply the knowledge to unfamiliar contexts indicates an understanding of
ratio as described by Skemp (1978) as relational. The author does not imply that the students could not
do multiplication and division previously, but there is strong evidence in the final product that their
thinking about ratio had progressed and that they could apply this knowledge to authentic situations.



In summary, the degree to which students made progress on pencil and paper tests varied considerably,
as did their demonstration of outcome indicators and they had attained better outcomes in science and
mathematics. Some students demonstrated thinking which indicated that they were achieving at levels
well in advance of what was expected in Year 7.




Assertion 4: Student manifestation of science and mathematics outcomes were
directly related to the technology activities.



Jill commented favourably on the activities as a means of teaching science and
mathematics, for example she stated:



I do believe that they have a far better idea of ratio. I think that the activities really cemented
ratio. The practical application with the gearing that was really good, because they had a
visual as well a practical application and it helped them to put it all together. It was a great
grounding and is going to stand by them for year eight and beyond, they will always recall
this.



Further, Jill noted lack of student motivation in the traditional way mathematics was
taught to this class:



They were very de-motivated in terms of maths. They hated it, because they felt that they
were not good at it. That is why I have adopted a thematic approach.



Jill commented on student motivation over the course of the study:



By and large, with the exception of probably about four people in the class, I believe that each
child valued it. Clearly, to me learning took place. They loved playing with it, you know, the
actual building of it. I think there was a sense of commitment there, the commitment to keep
working for so many weeks.



Clearly, Jill considered that student motivation during the construction activities was a
factor that contributed to their mathematics learning. However, she recommended that
increasing the connections between the activities and outside experiences of the
children such as "thrill rides and roller coasters and computer programs about how
thing work." The importance of linking various representations of the ratio concept
has been noted in research literature (e.g., Ben-Chaim, Fey, Fitzgerald, Benedetto, &
Miller, (1998); Lamon, 1995). Jill further recommended that links between
construction activities and formal mathematics be made.



I would keep them in the same sort of structure because this group needs structure, structure
but let the kids explore and talk as well. You need to make links to board work, to set time
limits, have set class discussion. They need a bit more time to absorb the information and
build the artefacts because some are thinking, "am I doing this right?"



The second teacher, Cameron supported the Jill’s evaluation of students learning and
like Jill he recommended that the links between the activities and formal mathematics
be made more explicit:



It is definitely more hands on (than a normal mathematics lesson) and appeals to a student
who likes to see things in their hands and count gears and so on. But, maybe some students
didn’t see the structure (underlying mathematics concept)"For that to happen maybe some
needed more direction, a bit more board work. Do the ratio with board work and then tell
them, "OK lets apply that knowledge to building with this Lego now."



In summary, both teachers believed that the gains in student achievement of specific mathematics and
science outcomes were mostly related to student engagement with the Lego technologies. Both
teachers also recommend more structure and scaffolding so that students could more readily make the
links between construction and other representations including formal mathematics and science
language and symbols.



Discussion and Conclusions


In the introduction, a rationale for using problem solving and reasoning associated
with personal context was given (e.g., Education Queensland, 2001; Jones et al.,
2002; NCTM, 2004). A number of authors (e.g., McRobbie, Norton & Ginns, 2003)
expressed a concern that the powerful ideas associated with construction activities,
including Lego construction and robotics could remain latent. With this in mind the
author made every effort to make the links between syllabus outcomes and activities
in the planning of lessons. The data presented in assertion 1 indicated that the Lego
construction activities are rich in opportunities to achieve outcomes listed in the
Queensland Mathematics, Science and Technology Syllabuses. In the case of
technology most of the outcomes were associated with the technology practice of
planning, constructing and evaluating artefacts. The study indicated that explicit
links between specific syllabus outcomes and construction activities could be made;
however, making such links was not a trivial task. A major problem for the author
was to recognise the mathematics and science embedded in the activities and to link
these to specific outcomes. The finding that there were so many potential outcomes,
that the author ultimately had to choose a few to make explicit. Thus, in this study
much of the underpinning science was never made explicit in class discussions. This
was reflected in the relatively limited use of science explanations that many students
gave in relation to the functioning of their artefacts, while other students made their
own connections between their constructs and the science that they knew.



Related to the challenge of identifying outcomes was that of assessing the levels of
outcomes, the challenges in identifying student thinking in mathematics been noted
previously (e.g., Gailbraith, 1993). It is a problem when operation within the
educational paradigm of conventional paradigm of scientific enquiry and the
intructivism teaching approaches associated with it. This study indicates that
evaluating student thinking in constructivism paradigms is a difficult task and not
made easier by an outcomes approach to reporting. The task of collecting and
evaluation students thinking associated with their construction and explanations of
their constructs was an ongoing interpretive process that involved the teachers
collecting and recording multiple sources of data. The framework based on the degree
of connections that students made between the different representations of the
mathematics and science concepts presented in the analysis section of Design and
Methods was a useful means to match student explanations and constructs to specific
syllabus outcomes. However, refinement of this tool for use on different outcomes is
needed. The difficulties were compounded by the group nature of the construction
tasks, in particular how was a mark for the group to be allocated to the individuals
within the group?



The results summarised in assertion 2 illustrate that the author and Jill were aware that
there was a danger of key concepts remaining implicit and Jill encouraged the author
to move his pedagogy away from some sort of lassie faire constructionism and
towards "directed constructionism." This was evidenced in her repeated
recommendation for more structure in the lessons. While the pedagogy that Jill was
recommending and the author was attempting to implement was not "traditional
teaching," it had many of the elements of instructivism (Marsh, 2004) including
careful verbal instruction at the beginning of the lesson, orientation of students in
relation to key concepts and expected outcomes and there were to be opportunities to
reinforce via practice. Jill’s concern was most apparent in relation to those students
who struggled to make the links between the construction tasks and the abstraction of
mathematical ideas. The idea that teachers believed that students who struggle need
more direct instruction pedagogy has been noted previously, (e.g., Norton, McRobbie
& Cooper, 2002). To take account of the differing needs of students of different
abilities and with different prerequisite knowledge the author allocated increasing
time to the processes of abstracting mathematics and science principles. While, the
major part of each lesson was still in the context of students working in groups to
design, make and explain their products, teacher intervention increased over the life of
the study. In order to encourage students to make the links between various
representations (e.g., the machines, plans and the formal language of mathematics and
science) the author and Jill agreed to further emphasise student explanations. It was
recommended that each group would present their product and be rated on the quality
of their explanations on how it worked. In this way the author was attempting to add
focus and structure to student discourse. In short, the activities provided ample
opportunity and stimulus for student discussion, the challenge for the teaching team
was how to scaffold the lesson such that the discussion was purposeful.



The results of this study presented in assertion 3 indicate that the use of concrete
materials in the context of design, construction and evaluation activity provides rich
opportunity to connect mathematics and science concepts and to promote the learning
of powerful ideas such as ratio, force and energy transfer. The student results on
pencil and paper tests, the student constructions and explanations indicated that some
students made considerable progress on specific science and mathematics outcomes.
On the other hand other students did not demonstrate improved outcomes. The
teachers’ comments suggested that the learning gains were mostly due to student
involvement in the intervention, rather than some other factor such as maturation or
alternative learning activities. Given the difficulty level of these concepts such has
ratio, (Karplus, Pulos, & Stage, 1998; Resnick & Singer, 1993) and rate (velocity)
such improvement in results supports the suggestions of those authors who
recommend multi representations of mathematics and science concepts, including the
use of manipulative material (e.g., Ben-Chaim, et al. 2002; Lamon, 1995). The results
encourage the adoption of an integrated approach to teaching powerful ideas, as
reflected in reform curriculum documents (e.g., Education Queensland, 2001) and
situated learning contexts (Brown, Collins, & Duguid, 1989). More specifically, the
results support the suggestion that Lego is a very useful manipulative for the learning
of mathematics and science.



The study illustrates that there were challenges in attempting to meet varying student
needs for scaffolding, and these were manifested in difficulties in planning and lesson
conduct. There were also substantial challenges in assessing student progress and to a
degree these remain unresolved. However, the study adds to our capital of
pedagogical knowledge about how the use of tools such as Lego can be used to foster
the kinds of social relationships and engagements with authentic and contextual
problems learning. As noted by Papert (1980) "giving children good things to do" "
can foster powerful learning, but the task of achieving connected learning is by no
means simple. The study also indicates that significant professional development may
be needed to help teachers to plan, conduct and evaluate lessons.

Tuesday, September 23, 2008

How to Build a Lego Robot

How to Build a Lego Robot



Legos are a classic toy for children that encourage creative thinking and help children to learn basic construction skills. Those colorful blocks are a wonderful way to access your own inner child, no matter what your age. Many people can recall building Lego robots as children, but maybe forgot how now they've aged. Follow these steps to help you build a Lego robot and relive the magic of Lego construction.



Instruction


Step 1.

Gather Legos together, if you haven't done anything with Legos in a while visit the store and buy a new set of basic Legos. Look for the Legos especially built for robot construction as it may come with some accessories to aide in your robot making.


Step 2.
Learn the difference between Lego bricks, plates and beams. Decide whether you want your robot to have legs or whether it will work on a wheel or pulley system before construction and if you will use the newest Lego Mindstorm technology to make your robot more technologically advanced..


Step 3.
Look online for a tutorial on how to build specific kinds of Lego robots. Search for a robot template that best fits what your imagination has dreamed and then tweak your robot from that skeleton construction.


Step 4.
Start with the base of your robot, since it will most likely be the most intricate part of your Lego robot. Secure all the pieces so that your robot will stand up to interaction and can support the weight of the rest of the robot. Remember your robot can take car or aircraft shape.


Step 5.
Be creative. Rely on your own sense of judgment about how you want your robot to look. Take a look at some Lego robots you admire and borrow some of the building techniques of those Lego builders. Remember to have fun.

Using Lego Construction to Develop Ratio Understanding



Using Lego Construction to Develop Ratio Understanding.



Stephen Norton

Queensland University of Technology

<sj.norton@qut.edu.au>






This paper examines Year 7 students use and learning of ratio concepts while engaged in
the technology practice of designing, constructing and evaluating simple machines, that
used cogs and pulleys. It was found that most students made considerable progress in
accounting for ratio concepts in their constructions and some constructed sophisticated
machines and provided explicit and quantitative descriptions involving ratio reasoning.
The findings have implications for the study of mathematics in integrated and contextual
settings.





One of the critical questions facing mathematics education today relates to learning
contexts. In particular what kinds of mathematical tools and representations are needed to
promote mathematical learning and how these tools should be used (English, 2002). New
technologies are giving rise to major changes in mathematics education. There are now
numerous opportunities for students and teachers to engage in mathematical experiences
that were scarcely contemplated a decade ago. However, the effective use of new
technologies neither happens automatically, nor will the use of technology lead to
improvements in mathematics learning without changes to the curriculum (Niss, 1999).
Equally important is what pedagogical changes become associated with learning, with new
learning contexts and tools (Kaput & Roschelle, 1999).



In terms of changes in curriculum there has been a shift in the content of mathematics,
the most important shift in the last two decades has been towards increased emphasis on
powerful ideas associated with mathematical processes (Jones, Langrall, Thorton, &
Nisbet, 2002). NCTM Standards (2004) has encapsulated this trend world wide by giving
pre-eminence to five process standards: problem solving, reasoning and proof,
connections, communication and representation. This shift in curriculum approach towards
communication of reasoning and integration, or contextual problem based learning
reasoning has found expression in attempts to integrate science and technology with
mathematics. For example, the New Basics curriculum documents (Education Queensland,
2001) has a strong emphasis on integrated learning. This document encourages teachers to
use integrated community based activities, where the role of the teacher is one of
mentoring while students engage in tasks that are relevant and authentic to the students.
Other curriculum documents have recommended an approach to mathematics teaching and
learning that is integrated or transdisciplinary and were the mathematics is embedded in
authentic contexts (e.g., National Council of Teachers of Mathematics, 2004; Queensland
Studies Authority, 2003). Such tasks tend to enable students to develop modelling
capacities that need greater mathematizing and the conceptual use of mathematics (e.g.,
Nason & Woodruf, 2003).



In the middle school years of mathematics, many topics require ratio reasoning skills. It
is required for example, in applications of percentages, rate, ratio, the study of
trigonometry and proportion applications. Lamon (1995, p. 169) defines ratio "as a
comparative index that conveys the abstract notion of relative magnitude." The difficulties
in teaching ratio are further illustrated by the very small fraction of early adolescents, who
can apply numerical approaches meaningfully in addition, the critical importance of ratio
(and proportional understanding) has been noted previously (e.g., Karplus, Pulos, & Stage,

1983). Resnick and Singe (1993) put forward the hypothesis that early abilities to reason
non numerically about the relations among amounts of physical material, provide the child
with a set of relational schema that eventually apply to numerically quantified material,
and later to numbers as mathematical objects. In the process of teaching ratio it has been
recommended students be given time to explore and discuss authentic ratio and
proportional situations/problems and not to be placed in the situation where
algorithmisation and automatisation clogs the process of insight development (e.g., Ben-
Chaim, Fey, Fitzgerald, Benedetto, & Miller 1998). Thus the purpose of this paper is to
explore the learning of ratio when students design, make and appraise artefacts in which
ratio thinking is embedded.



Approach and Methodology


This paper reports on students learning of ratio concepts within the context of a larger
study involving the integration of mathematics, science and technology syllabus outcomes.
The research approach was one of participatory collaborative action research (Kemmis &
McTaggart, 2000). The researcher established a working relationship with the teachers and
taught most of the 2 hour lessons over a 10 week period. The collection of data included
observations of students’ interactions with objects, peers and teachers, students planned
and constructed artefacts, their explanations of how things worked, and written tests.
Subjects



The subjects were 56 Year 7 students in two classes in a State primary school in
Brisbane. The school was a trial school for New Basics Curriculum (Education
Queensland, 2001) that attempts to integrate the teaching of subject domains of science and
mathematics into authentic project based tasks. The two classroom teachers were also part
of the study. Jill (all names are pseudonyms) was a very experienced primary school
teacher who also had extensive tertiary teaching experience and a passion for science. The
second teacher, Cameron was also experienced in teaching this year level. In addition he
had completed a science degree.



Procedure and Instruments


For most lessons the students worked on constructions in groups of two or three and
the researcher moved between groups facilitating construction of artefacts and encouraging
them to explain their artefacts in terms of science and mathematics principles. In some
lessons, 10 to 15 minutes was spent in whole group discussion of the underlying theories.



Prior to beginning teaching the researcher and Jill matched science outcomes
(Queensland School Curriculum Council, 1999) and mathematics outcomes (Queensland
Studies Authority, 2003) with construction activities related to the "Simple and Powered
Mechanisms" kits (Lego Educational Division, 2003) that were designed to help students
learn engineering concepts. The kits contains a motor, various cogs and pulleys, various
blocks, axles, connecting pieces as well as instruction booklets. In the first half of the
intervention, students constructed artefacts with the assistance of the Lego plans (Lego
Educational Division, 2003). Thereafter they increasingly constructed from their own
plans.



The principal mathematics concepts were; velocity, revolutions, linear measurement,
circumference (with radius, and pi), quantification of gear ratios and quantification of
pulley mechanisms (ratio and proportional reasoning). Combined with the technology and

science outcomes, the intervention covered a considerable range learning outcomes. This
report focuses on student development of ratio.



Prior to the implementation of the study, the students were pre-tested for knowledge
related to ratio and proportional reasoning - mathematics concepts associated with the
planned activities. The pencil and paper tests had 11 questions that examined ratio. Some
questions were simply definitions, for example: "A small car motored across the room.
What is this motion called and what units were used to measure it?" (rate). Further
questions required quantitative expressions of proportional reasoning to gain full marks
for- example:



Examine the diagram of pulleys below. If the circumference of pulley A is 20cm, the circumference
of pulley B is 40cm and the circumference of pulley C is 10cm and pulley B I spun twice, describe
how pulleys A and C will spin. Explain why this will occur.



Other questions were more open, for example, students were given the number of teeth on
various gear cogs and asked to use their knowledge of bicycles to create a matching pair
that would help the bike go fast, and to give a possible explanation that would be correct
and complete. Scoring was on the basis of correctness and completeness of explanations,
and each item was allocated 2 marks. Answers that had correct quantitative responses as
well as their explanations were allocated full marks. In the second week of the study the
students also planned and constructed an artefact that either served a practical need or
modelled a useful product. At the end of the study students repeated the planning and
construction activity, and the science and mathematics tests. Throughout the study the
teachers acted as observers and documented student activity that indicated that outcome
had been meet.



Analysis


The written pre and post test data were converted to percentages. The pre and post tests
are compared using simple paired t tests. Student artefacts were examined for the
application of engineering principles such as leverage and gear ratio that reflected ratio
concepts. In assessing the artefacts and assessing the associated explanations the
descriptions of ratio cited above (Lamon,1995) was used. Thus, student explanations and
constructions were examined with respect to the correctness and completeness in terms of
the application and articulation of ratio principles. Throughout the study students were
asked a number of times to explain their artefacts. A hermeneutic cycle (Guba & Lincoln,
1994) was employed in developing and testing assertions as the study progressed.
Emerging assertions were discussed with the teachers and colleagues and tested and
refined in the light of further evidence. Triangulation involved the use of multiple data
sources identified above and this maximised the probability that emergent assertions were
consistent with a variety of data.



Results


The results are presented as a number of assertions.



Assertion One: Most students improved in their ability to explain science and
mathematics concepts on pencil and paper tests.



Descriptive statistics and mean comparisons are contained in Table 1 below.
Descriptive statistics indicate that the assumption of homogeneity of variance was not
violated. All tests had approximately normal distributions of scores. There was a

significant difference in the mean scores for science as indicated by the paired t test result,
[t(55)=10.26, p < 0.000}, with the students scoring higher on the post-test. A number of
students performed poorly in both pre- and post-tests. A few students made hardly any
progress at all, supporting earlier findings that ratio is a concept that some students find
very difficult to grasp (e.g., Resnick & Singer, 1993).




Table 1

Pre and Post-Test Paired Results on Ratio Questions as Percentage of Total.















Test N Mean SD
Maths pre-test5633.0417.59
Maths post-test5660.59**21.37


**Significance level at p < 0.01





Some students gave correct quantitative answers as well as correct qualitative
explanations. For example students were shown a picture of two meshing cogs- a small one
B and a larger one A, and asked to explain the effect of turning A twice on the smaller gear
B. Some students counted the teeth of the cogs (13 on B and 24 on A) and responded "A
turns 1.846 times while B turns once." Most students responded with qualitative answers
such as "A turns about twice for each turn of B." While these responses take account of the
ratio, a few students gave responses that took account to proportional reasoning to suggest
"B will turn about 4 times to make A turn twice."



The data indicate that most students’ ability to answer pencil and paper tests based on
ratio concepts improved over the course of the study. Still, it is somewhat disappointing
that despite some 16 hours of engagement on construction activities associated with ratio
the mean final score was only about 60%. On the other hand, students are not expected to
demonstrate an understanding of ratio concepts until Level 5 (Queensland Studies
Authority, 2003) which equates to junior secondary school but is often introduced in Year
7. Thus, students who were able to demonstrate an understanding of ratio were operating in
advance of what was expected of them. Further, ratio was not the only focus concepts,
because as noted earlier, science and technology outcomes were also being developed.



Assertion Two: Most students improved in their ability to use and explain ratio and
proportional reasoning in their construction of artefacts.



Selected students described in this discussion are exemplars of those who made
representative gains in ability to use and explain science and mathematics principles
associated with their artefacts. All groups made considerable improvement in the quality of
the plans and constructions they created. Most notable was the use of gearing to effect an
outcome, improved application and explanation of ratio and a better application and
explanation of the mathematical principles inherent in circles and understanding of
velocity. Perhaps the best example is of the pair of girls (Sarah and Mary), who designed
and constructed the car shown in Figure 1 in week two. Sarah explained that this car was
designed for all terrain travel. It featured the use of a simple pulley system to drive a four
wheel drive "tractor" using a 40 tooth cog gear for rear wheels to "help with grip." The
design illustrates that the students did not understand the relationship between wheel
diameter and circumference. When they tested the car, it would run on a desk where
slippage negated the lack of synchronization between the front and back wheels, but would
not run on carpet where the front wheels acted as a brake on the back wheels. Despite
prompting, the girls could not diagnose the problem without explicit scaffolding that

directed them to consider how far each wheel would turn for each revolution of the motor.
In this instance, not only did the students not recognise the significance of the relationship
between the different diameters and the distance each wheel would travel, they assumed
the ratio of front and rear wheel travel was equivalent. Interestingly, the students had very
recently studied the relationship between diameter and circumference, but were unable to
use this knowledge in a novel context, that is, they had instrumental rather than relational
understandings (Skemp, 1987) of this concept.



alisanjaya



In contrast, in week 8 Sarah and Mary had designed the tractor illustrated in Figure 2.
This tractor won a tug of war competition against other student constructed tractors. Sarah
and Mary could now both explain the use of multiple cogs to create an overall gearing ratio
of 15:1. Their diagrammatic explanation of the gearing is seen on the planning sheet below
the tractor in Figure 2. Their written explanation included:



The 8 teeth gear on the motor (driver) will turn the 40 teeth gear underneath it, (the driver) will turn
5 times, then 8 gear on the same bar as the 40 teeth gear will also turn 5 times, when the 8 gear turns
5 times, the gear with 40 teeth will turn once, making the 24 teeth gear that is behind the wheel turn
around about 1 and ¾ times.



The students were aware that the drive had to turn 25 times to effect an outcome of "about
1 and ¾ times." The girls had initially tried to use a 40 tooth cog on the final drive but used
a 24 tooth cog on this model. They used a 24 tooth cog to solve a construction difficulty
(cog matching). Had the girls not used the 24 teeth cog the final ratio would have been
25:1. Clearly, the girls have presented very strong evidence that they had progressed in
their ability to use ratio, and their description of the final ratio-25 is to "about 1 and ¾," is
remarkably accurate. These girls also made considerable advances in their pre and posttests
on ratio and proportion related questions (Sarah, 43% to 77%; Mary, 58 to 84%).
Consistent with the test data, not all students made such gains in their ability to apply and
explain ratio concepts in the construction and explanation of their artefacts. For example,
the boys who constructed the racer in Figure 3 below were able to give a qualitative
explanation for their gearing:



Well the big pulley will go round once, but it will make the driver pulley go round lots and
make the car go really fast.



This explanation demonstrated a qualitative understanding between the diameter and the
circumference of each pulley and the relative circumferences of each pulley.




alisanjaya


Figure 3: Pulley racer.



Even students who made very limited gains in the written test produced products that at
least accounted for 1:1 drive ratios, although they did not make these relationships explicit.
For example, in describing the workings of a 4 wheel drive with all pulleys of 1cm
diameter, the following description was offered:



The motor is connected to the wheels with a rubber band, when the motor makes the first wheels
turn, the others turn and that makes it work.



This statement makes no attempt to describe the relationships that exist between the pulley
sizes nor how this effects their functioning. None the less, the car was functional.



Assertion Three: Most students made gains in their ratio and proportional
reasoning abilities over the life of the study and this was directly related to the
technology activities.



Jill commented favourably on the activities as a means of teaching science and
mathematics, for example she stated:



I do believe that they have a far better idea of ratio. I think that the activities really cemented ratio.
The practical application with the gearing that was really good, because they had a visual as well a
practical application and it helped them to put it all together. It was a great grounding and is going
to stand by them for year eight and beyond, they will always recall this.



Further she noted lack of student motivation in the traditional way mathematics was taught
to this class:



They were very de-motivated in terms of maths. They hated it, because they felt that they were not
good at it. That is why I have adopted a thematic approach.



Jill commented on student motivation:



By and large, with the exception of probably about four people in the class, I believe that each child
valued it. Clearly to me learning took place. They loved playing with it, you know, the actual
building of it. I think there was a sense of commitment there, the commitment to keep working for
so many weeks.



Clearly, Jill considered that student motivation during the construction activities was a
factor that contributed to their mathematics learning. However, she recommended
increasing the connections between the activities and outside experiences of the children
such as "thrill rides and roller coasters and computer programs and about how thing work."
The importance of linking various representations of the ratio concept has been noted in
research literature (e.g., Ben-Chaim et al., 1998; Lamon, 1995). Jill further recommended
that links between construction activities and formal mathematics be made.



I would keep them in the same sort of structure because this group needs structure, structure but let
the kids explore and talk as well. You need to make links to board work, to set time limits, have set

class discussion. They need a bit more time to absorb the information and build the artefacts
because some are thinking, "am I doing this right?"



The second teacher, Cameron, supported Jill’s evaluation of students learning and like
Jill he recommended that the links between the activities and formal mathematics be made
more explicit:



It is definitely more hands on (than a normal mathematics lesson) and appeals to a student who likes
to see things in their hands and count gears and so on. But, maybe some students didn’t see the
structure (underlying mathematics concept)…For that to happen maybe some needed more
direction, a bit more board work. Do the ratio with board work and then tell them, "OK lets apply
that knowledge to building with this Lego now."



Discussion


It has been previously noted that the traditional way that ratio has been taught, lead to a
lack of transferability of that knowledge (e.g., Ben Chaim et al. 1998). This study
demonstrates that use of concrete materials such as Lego offer a mathematically rich
environment where the powerful idea of ratio is used by students in problem solving and
reasoning contexts that have personal meaning to them as has been recommended (e.g.,
Education Queensland, 2001; Jones et al. 2002; NCTM, 2004). The student results on
pencil and paper tests, the student constructions and explanations indicated that the
activities were rich in opportunities to promote the learning of ratio. The teachers’
comments suggested that the learning gains were mostly due to student involvement in the
intervention, rather than some other factor such as maturation or alternative learning
activities. Given the difficulty level of these concepts, (Karplus et al., 1998; Resnick &
Singer, 1993) such an improvement in results supports the suggestions of those authors
who recommend a multi representational of mathematical concepts, including the use of
manipulative material as an approach to teaching ratio (e.g., Ben-Chaim, et al. 2002;
Lamon, 1995). The results also encourage the adoption of an integrated approach to
teaching powerful ideas, as reflected in reform curriculum documents (e.g., Education
Queensland, 2001) and situated learning contexts (Brown, Collins & Duguid, 1989). It
also supports the suggestion that the use of Lego is a very useful manipulative for the
learning of mathematical ideas. A number of authors (e.g., McRobbie, Norton & Ginns,
2003) expressed a concern that the powerful ideas associated with such activities,
including Lego construction and robotics could remain latent. Both classroom teachers in
this study recognised this as a potential issue for some students. The comments of the
teachers indicated that they believed that at least, to some degree, the learning of ratio
could have been better, with more explicit linking of the mathematical ideas and the
construction activities. This was especially recommended for students who struggled to
make the links between the construction tasks and the abstraction of mathematical ideas.
The number of students who did not make ratio a part of their description of their artefacts
supports this suggestion. This study adds to our capital of pedagogical knowledge about
how the use of such tools can foster learning. In particular, it indicates that a clear focus on
specific mathematics outcomes may be necessary. It is recommended that teachers
undertake professional development that includes learning to identify specific mathematics
outcomes inherent in construction activities, and ways of using Lego materials in the
classroom.


CONSTRUCTOPEDIA

A reference work containing articles on different aspects of construction. This is the place to learn all about how things work!


This section is an ideal supplement for teachers using the LEGO Education Science & Technology range of products, helping youngsters understand principles of machines and mechanisms.


Changing Direction Of Pulley Rotation




Main Idea:
Two pulleys connected by a crossed belt turn in opposite directions.

Additional Information:
Two pulleys connected by a straight belt turn in the same direction. If you want the pulleys to turn in opposite directions, you have to cross the belt and make a figure-eight shape. In this model, the belt is crossed so the driver and follower pulleys turn in opposite directions. As in any pulley model, the belt has a small amount of slippage, which keeps the belt loose so it won't break if the wheels are forced to stop.

Compound Belt Drives




Main Idea:
Pulley wheels of two different sizes on the same axle can be connected to other pulley wheels to build more extensive gearing down (and gearing up) arrangements.

Additional Information:
If you need to have even more force or speed than you can get from a two-pulley arrangement, you can combine pulleys and belt drives to create a more extensive gearing combination. In this model, we see another axle and pulley added to gear down to an even greater extent. The first follower wheel turns slowly - the second turns even slower. You can also build larger gearing up arrangements.

Compound Gearing




Main Idea:
Gears of different sizes on the same axle can be connected to other gears to build more extensive gearing down (and gearing up) arrangements.

Additional Information:
Compound gearing gives you the ability to use even more force by adding more gears to the arrangement. You can connect more gears on the same axle to build more complicated arrangements. In this model, we see two separate 5:1 gearing down arrangements, connected to each other by the axle passing through the first 40-tooth gear and the second 8-tooth gear. The first 40-tooth gear turns slowly. The second 40-tooth gear turns even slower. This connection increases the gearing down ratio to 25:1.

Decreasing Pulley Speed




Main Idea:
If you use a small pulley wheel to drive a large pulley wheel, the large one will turn slower.

Additional Information:
With this model, we have a pulley with a small driver wheel and a large follower wheel. It's really hard to make a wheel like the big one turn - it would take a lot of force. But with a smaller wheel, we can use a process called gearing down to help. Gearing down decreases speed but increases force. Since it's easy to turn a small wheel at a fast speed, we use it to move the large one. A small driver wheel makes a large follower wheel turn more slowly. Since this is a pulley model, both wheels turn in the same direction.

Direction Of Pulley Rotation




Main Idea:
Two pulleys connected by a belt turn in the same direction.

Additional Information:
Here we see two wheels connected by a belt. When you turn the driver wheel, the belt causes the follower wheel to turn. This is a pulley system. The two pulley wheels connected this way will turn in the same direction. As in any pulley model, the belt has a small amount of slippage, which keeps the belt loose so it won't break if the wheels are forced to stop.

Direction Of Rotation




Main Idea:
Two gears which are meshed together turn in opposite directions.

Additional Information:
Here we see two gears meshed together. When you mesh two gears, turning the driver gear makes the follower gear turn in the opposite direction.

Gearing Down




Main Idea:
If you use a small gear to drive a large gear, the large one will turn slower.

Additional Information:
Here we see a small driver gear and a large follower. It's really hard to make a gear like the big one turn - we'd have to use a lot of force. But with a smaller gear, we can use a process called gearing down to help us out. Gearing down decreases speed but increases force. Since it's easy to turn a small gear at a fast speed, we use it to move the large one. A small driver gear makes a large follower gear turn more slowly. For this model, five turns of the 8-tooth driver produce one turn of the 40-tooth follower. This ratio of 5:1 is called the gearing down ratio.

Gearing Up




Main Idea:
If you use a large gear to drive a small gear, the small one will turn faster.

Additional Information:
Here we see a large driver gear and a small follower. We can move the small gear pretty fast on our own, but we can use a process called gearing up to move it even faster. Gearing up increases speed, but decreases force. A good example of a gearing-up system in real life is a 10-speed bike - when you shift into 10th gear, you turn a large gear with the pedals, which drives a small gear attached to the rear wheel. For this model, one turn of the 40-tooth driver produce five turns of the 8-tooth follower. This ratio of 1:5 is called the gearing up ratio.

Idler Gearing




Main Idea:
An idler gear is used to make a driver gear and a follower gear turn in the same direction.

Additional Information:
Additional Information:
Sometimes you need to have gears turn in the same direction. Since a driver gear and a follower gear turn in opposite directions, an idler gear is placed in between the two gears. The idler gear rotates in the opposite direction as the driver gear, and the follower gear rotates in the opposite direction of the idler - i.e. the same direction as the driver!

Increasing Pulley Speed




Main Idea:
If you use a large pulley wheel to drive a small pulley wheel, the small one will turn faster.

Additional Information:
Additional Information:
In this pulley model we have a large driver wheel and a small follower. We can move the small wheel pretty fast on our own, but these pulleys use a process called gearing up to move it even faster. Gearing up increases speed, but decreases force. A large driver wheel makes a small follower wheel turn faster. However, unlike gears, in this pulley model both wheels turn in the same direction.

Pulley At An Angle




Main Idea:
A belt drive can be used to change the direction of rotation by 90 degrees.

Additional Information:
If you need to change the direction that an axle is facing, you can place your pulley at an angle. In this model, the driver gear is at a 90 degree angle to the follower. The direction of rotation changes 90 degrees when the driver is turned. The driver pulley and the follower both turn in the same direction. This model also shows a gearing down arrangement, as the driver pulley is smaller than the follower.



source : www.lego.com

LEGO DESIGN


LEGO Design


LEGO Technics are fun to play with and allow the construction of interesting structures, but they are not always easy to use. In fact, it is often quite challenging to build a LEGO device that does not fall apart at the slightest provocation. A well-designed LEGO device should be reliable, compact, and sturdy. If it makes extensive use of gears, the geartrain should be able to rotate cleanly and easily. If it is a structural element, it should hold together squarely and resist falling apart. This chapter discusses some ideas for creating a well-designed LEGO structure, as well as some properties of the LEGO Technic system that may not be obvious at first glance. Keep in mind that sometimes the best way to discover LEGO is to explore, focus on the brick, and try new things.

Fundamental LEGO Lengths







Figure 8.1: The Unit LEGO Brick





LEGO pieces have standard sizes so LEGO structures are usually multiples of those dimensions. The Fundamental LEGO Unit (FLU) refers to the height of a simple brick, and can be expressed in standard units, such as the millimeter: the vertical FLU is 9.6 mm. Interestingly, the ratio between the length or width of a brick and its height is not an integer, but a ratio of two small integers: 6 to 5 (see Figure 8.1).





Figure 8.2: Perfect 2-Unit Vertical LEGO Spacing






The 6:5 ratio, coupled with one-third height flat pieces, allows the creation of vertical spacings that perfectly match unit horizontal spacings, the spacing between the holes in LEGO beams (see Figure 8.2). By using these perfect LEGO spacings, vertical stacks of bricks can be reinforced with cross-beams, forming sturdy structures that should not fall apart.




Figure 8.3: Clamping Two Beams at Perfect Vertical Spacing





Figure 8.3 shows an example of two 8-long LEGO beams (separated by a two-unit perfect spacing) braced at the ends by two 4-long LEGO beams; this structure is extremely sturdy. Other combinations of perfect vertical spacings are possible with the one-third height bricks; in fact, all of them can be computed. Let a represent the number of full-height vertical units and b the number of one-third height vertical units; then the height of a LEGO assembly (in mm) would be




9.6(a + {13}b) (4)



since a full vertical unit is 9.6 mm high.


The length between holes in a LEGO beam is 8 mm, so if c represents the number of horizontal units between the two holes, then the holes are spaced by 8c mm. To find a match of vertical and horizontal spacings, we need to find values of a , b , and c that make these two quantities equal, with the restriction that a , b , and c are integers (since we cannot use fractional pieces of a LEGO:




9.6(a + {13}b) = 8c (5)



which reduces to




2(3a + b) = 5c (6)



The following table lists some solutions to this integer equation: Bracing LEGO structures using perfect vertical spacings is a key method of building a structurally sturdy machine.




Figure 8.3: Clamping Two Beams at Perfect Vertical Spacing































Full Height One-Third Horizontal
Units Units Units
122
314
56
628
8110



LEGO Gearing


Making a good LEGO geartrain is, some may say, an art. However, this art can be learned and having some simple information can make a big difference. One of the first things to notice about LEGO gears is their diameter, which indicates at what spacings they can be meshed together.


The natural units for the sizes of LEGO gears is the horizontal LEGO spacing unit. The following table shows the radii of the various LEGO gears:

























Gear Teeth Gear Radius
(number) (horizontal units)
80.5
161
241.5
402.5




Notice that three of the gears (namely, the 8-tooth, 24-tooth, and 40-tooth) have radii that, when used together in pairs, result in axle spacings that are integer multiples of the fundamental LEGO horizontal unit spacing. For example, the 8-tooth gear may be used with the 24-tooth or the 40-tooth gear, but not the 16-tooth gear.




Figure 8.4: Meshing of an 8-Tooth Gear and a 24-Tooth Gear





Figure 8.4 shows how an 8-tooth gear would mesh with a 24-tooth gear along a LEGO beam. The 16-tooth gears only mesh with each other according to this logic.


Gears may be meshed together at odd diagonals. However, this requires great care, as it is difficult to achieve a spacing that is close enough to the optimal spacing (which can be computed by adding the gears' radii). If the gears are too close, they will bind or operate with high frictional loss; if they are too far apart, they will slip. Figures 8.5 and 8.6 show some (but not all) examples of diagonal gearing that have been tested to work well.




Figure 8.5: Diagonal Meshing of an 8-Tooth Gear and a 16-Tooth Gear









Figure 8.6: Diagonal Meshing of a 16-Tooth Gear and a 24-Tooth Gear





When constructing any gearbox, especially those that involve gears meshing at odd diagonals, it is important to keep in mind that although the LEGO gears are very functional in terms of experimenting with various designs, their performance over time is not ideal. Gears meshing in even the most thoughtfully constructed gearbox may begin to wear, and might have a greater tendency to slip under stress. While it is important to develop a sturdy gearbox, it might be wise to keep its parts accessible in the event that a gear needs to be replaced after the robot has been constructed.


A very high performance geartrain will be necessary for driving a robot. For this type of geartrain, the following rules are suggested:


8-tooth and 24-tooth gears should be used. The 40-tooth gears are also good, if they can be fit in despite their large size.


The worm gear can be used to quickly assemble a good geartrain, although worm gears will cause more power loss due to friction than other types of geartrains.


The axles should be spaced at perfect LEGO spacing, or a close diagonal approximation. This is easy to do if the axles are mounted adjacent on the same beam, or across beams using perfect LEGO spacing.


Each axle should be supported at two points by going through at least two girders or beams. These support girders should be separated from each other. If these two rules are followed, the axles will stay straight and not bind up inside the girders, creating a lot of friction.


When multiple girders support the same axle, these girders should be firmly attached to each other. If they are not perfectly aligned, the same binding problem described above may happen, and the gear train could lose a lot of power.


The axles can bend. Gears should not be dangling at the end of an unsupported axle. Gears should either be put between the girders supporting the axles or very close to the girders on the outside of the girders. Both cases are illustrated on the example gear train. If the gear is two or more LEGO units away from the outside of the girders, problems may arise.


Axles should not fit too tightly. After gears and spacers are put on an axle, the axle should be able to slide back and forth a little bit. It is very easy to lose a lot of power if spacers or gears are pressing up against the girders.



Gear Reduction


Gearing serves two main purposes: transmitting and transforming mechanical energy. For the purposes of a drive train, the gears will change the high speed and low torque of a DC electric motor to the low speed and high torque that is required to move a robot. Experimentation with different gear ratios is important. The gear ratio determines the important tradeoff between speed and torque.


Figure 8.7 illustrates a sample LEGO geartrain that achieves a gear ratio of 243:1 through the use of five ganged pairs of 8-tooth to 24-tooth gear combinations (this gear ratio may be overly high for a robot drive). It is suggested that a copy of this geartrain be built for evaluation -- it is an efficient design and follows the rules presented here.





Figure 8.7: LEGO Gearbox Example








Chain Drives


Use of chain drives requires a fair bit of patience. To find gear spacings that will work for the chain requires a lot of trial and error design. If the chain is too loose, it may skip under heavy load; if it is too tight, it will lose power. Experimentation is required. The chains tend to work better on the larger gears and with fundamental LEGO spacing between the axles. See Appendix A for more information about building a good chain drive.

Differentials




The differential gear is used to help cars turn corners. The differential gear (placed midway between the two wheels) allows one wheel to turn at a greater speed than the other. Even though the wheels may be turning at different speeds, the action of the differential means that the torque generated by the motor is distributed equally between the half-axles upon which the wheels are mounted. Assuming the robot's weight is sufficient and distributed properly, the robot should be able to turn with its drive motors at full power without causing either wheel to slip. In terms of robot construction, this means that one wheel could be completely stalled, while the other would continue to revolve. Because slipping of the wheels is avoided, static friction between the surface and the robot is maintained providing a better translation of rotational force to linear force.


The LEGO kit provided has both simple differential gears as well as two gear differentials. The two gear differentials allow the option of either a 16 tooth or 24 tooth spur gear as the final gear in the drivetrain. The regular differential has a cross between a spur and crown gear with 28 teeth, which requires some creative but not impossible spacing in order to achieve a gear reduction that meshes well.


Though you may decide not to use a differential as a means of transmitting motor force to the drive axles; this does not mean the differential is useless. When placed directly between the wheels of two independently driven drive axles, a differential gear, coupled with a shaft encoder, could potentially be used as a supplementary directional sensor without significantly affecting the operation of the drive wheels. For example, if a vehicle with a differential gear had a drive axle spinning at X revolutions per minute(rpm), the differential housing would be rotating at X rpm as well, so long as the vehicle is moving directly forward or backward. If the vehicle were to pivot about the point exactly in the middle of the drive axles, the differential housing would not rotate, as the bevel gears within the housing would then be operating at full speed. Based on these endpoints and some experimentation, a program could be written to determine the radius of curvature of the vehicle's motion. This method could also be applied to a differential used directly in the drivetrain, but it would be unlikely that the differential housing could be motionless while the drive motor is in action.


Figure 8.8 shows a simple LEGO differential gearbox.






Figure 8.8: A Simple Differential Gear






Testing a Geartrain



Back-driving is a good way to test a geartrain. The motor should be removed (if it is attached) and a wheel placed on the slow output shaft. When the wheel is rotated by hand make all the gears should spin freely. If the geartrain is very well-designed, the gears will continue spinning for a second or two after the output shaft is released.


Low-Force Geartrains


When building geartrains that will transmit only small forces, many of the design rules do not apply. Some of the usual problems may turn out to be advantages. For example, it may be desirable to have a transmission that "slips" when it is stuck, so that the motors do not stall and then a rubber band and pulley drive would be appropriate. The 24-tooth crown gear -- in addition to being perfectly usable as a normal 24-tooth gear -- will function at the intended 90 degree angle, as long as it is only transmitting small forces.


Rack and Pinion Steering


Rack and pinion steering uses a motor to turn a pinion (a LEGO gear), which then shifts a rack (a flat LEGO piece with grooves corresponding to gear tooth spacing) to the right or left. This allows very precise and smooth steering, especially when using a stepper motor. Figures 8.9, 8.10 and 8.11 show the top, side and front views of a simple LEGO steering mechanism that uses a rack and pinion. It is unlikely that this exact structure would be directly applicable to a working robot; however, it should provide a start.




Figure 8.9: Rack and Pinion Steering (Top View)






Figure 8.10: Rack and Pinion Steering (Side View)






Figure 8.11: Rack and Pinion Steering (Front View)






Multi-tasking Motors


At times, a robot may need to perform seven or more different mechanical maneuvers. This can be a problem as each robot is only able to power six different motors. However, there are ways of exploiting motors to perform multiple functions. Obviously, one motor could be used to drive two separate geartrains simultaneously, but then both geartrains are dependent on each other. If one stalls, then they both stall and it's impossible to turn one off without losing the other one.


One possible strategy for multi-tasking motors is to place the axle off center. Now the gear is acting like a cam. The drive train will be intermittently broken as the "camgear" and the drive train come in and out of contact. Figure 8.12 shows an example of a LEGO gear cam. One motor could be used to power two gear trains by setting up a "camgear" to intermittently drive one gear then the other (8.13). This approach would be most practical if a gear needed to repeatedly turn part of a revolution and then retract. The cam would turn the gear a partial revolution and a rubber band could be used to restore the original position. It would be a waste of a motor to turn a short distance forward then reverse over and over, and the motion is bound to be inconsistent. Thus if such a motion is desired, using a cam driven by another gear train can be a useful solution.






Figure 8.12: "Camgear"







Figure 8.13: Cam driving Two Gears Intermittently






Another possibility for multi-tasking a motor would be to use forward and reverse for different functions. It is possible to drive a motor in just one rotational direction and still be able to travel in reverse. The solution is a mechanical transmission. In Figure 8.14 the drive shaft can be made to turn either clockwise or counter-clockwise depending on which of the large gears is being turned by the motor. One way of selecting which large gear is turning is by using a mechanical transmission like the one shown in Figure 8.15. It is useful to note that the same gear reductions may be achieved for the forward and reverse motions by inserting a gear on a free-spinning axle into the gear reduction. The size of the extra gear is immaterial with regards to the gear reduction, so the appropriate gear size would depend only on convenience and a proper meshing distance between gears.



Figure 8.14: Bi-directional Drive Train






Figure 8.15: Mechanical Transmission Prototype





The manual transmission shown in Figure 8.15 is only a prototype. The idea is to be able to use forward and reverse from a single motor for separate tasks. The details of an actual implementation are left up to you. In the setup shown, driving into a wall moves a gear from one gear train to another, perhaps allowing the robot to change direction without changing the direction in which the motor rotates. One problem is how to move forward again. Simply using a rubber band or spring to return to the original gear train, not enough time will have passed to allow the robot to back away from the wall very far. With a bit of ingenuity and mechanical experimentation, it is possible to multi-task motors.



source : www.owlnet.rice.edu