SOLAR-ACTIVE
Schools & Homes Energy Education Project
Resources for Teaching Renewable Energy, Energy Efficiency and Sustainable Development
2-Q SOLAR MODEL CAR
Trouble shooting[‘trial and improvement’]
[Real life application of mathematics and scientific concepts in developing ones’ problem solving skills]
WHY USE THE SOLAR-ACTIVE SOLAR CAR/BOAT EDUCATIONAL RESOURCE KIT?
The solar model car kit was designed so that the builder of the car is encouraged to use their creative and inventive skills through a process of trial and error; experiencing the affects on the performance of the car of any changes they make first hand. As is often said – when something goes ‘wrong’ – learning takes place in the process of finding out why and in creating a solution.[1]
"In the instance of when the solar model car/boat does not work the educational process of trial and error - of serious play – of learning by doing – of investigative learning is working – is successful"[2]
to support our education method; The education method that the car kit it is based on, has been proven to be highly effective in creating enthusiasm in and encouraging invention; to while allowing one to gain knowledge and problem solving skills through crucial to real life application ofScientific, Mathematics, Technology and Engineering concepts.[3] - crucial to embedding sustainability into the heart of family, school, workplace and community life.
The kit is designed so the student very quickly builds a solar car that works – an immediate positive experience – along with a sense of ownership and enjoyment within normal 45/55 minute single lesson time period. The student accomplishes something and has a product to show. The student then makes adjustments bringing in innovation – allowing them independent thinking to affect the performance of the car.
WHAT MAKES SOLAR-ACTIVE CELL BEST FOR TEACHING?
· FLEXIBLE
· WORKS UNDER DIFFUSE LIGHT CONDITIONS
o The output [current and voltage] of the flexible solar cell is ‘good-enough’ to design and conduct controlled experiments under diffuse natural light conditions. Note: The SOLAR-ACTIVE solar cell are now assembled in UK {South Yorkshire and Wales} and features the following:
1. Thin-film amorphous silicon construction - no glass components
2. Flexible, durable, light-weight and waterproof
3. Responds to defuse light on a cloudy/rainy day
4. Output: 1Q-300mA & 1.5V; 2Q–300mA & 3V [*figures are accurate to +/- 10%]
5. Teacher/technical notes/curriculum schedule, student worksheets and experiments [electronic/C-D/paper]
WHAT EFFECTS PERFROMANCE OF THE CAR?
The kit appears simple – and is easy to assemble, however, it is up to the teacher & student to use it to its full potential. For example, built into its design and components used in the front wheel assembly to affect bearing performance and friction, is a visual reminder of key engineering concepts required in the learning of engineering.
The following can be modified to affect performance [e.g. to go straight and with speed] of the car:
a. Adjust angle of solar cell and orientation of cell to light source
b. [ http://www.pluggingintothesun.org.uk/case2.pdf]
c. Adjust horizontal side-to-side play of front assembly axle
d. Make the car go straight
e. Make the car go in circles
GREEN SOLAR MATHS:-
The student will need to cut the straw to the correct length to minimize friction and optimize speed. This task involves both Science and Maths.
Designing and constructing the front axle ‘bearing’ mechanism from a straw provides practical application[4] of maths – The student works out the accurate length to measure and cut the straw. The student sees the relevance of measuring something correctly, as their measurement has a direct effect on the performance of the car. Building a faster car provides a real incentive to get the measurement correct.
This is what you need to take into account to decide the length of the straw to ensure the straw is cut to the correct length.
i. Width of wheel tread
ii. Width of inner wheel protrusion + reducer when using 40/50mm hard coloured plastic wheel
iii. Width of outer reducer when using 40/50mm hard coloured plastic wheel
iv. Leave some side-play
· What is the minimum and maximum play to allow for the car to perform best?
v. Length of exposed axle
· How far will you allow the axle go into the reducer in each wheel?
vi. Diameter of axle
vii. Internal diameter of straw [tight or loose – which is best for speed?]
viii. Cutting tool [you will need to insert something into straw before cutting to keep straw from being crushed and becoming flat].
ix. Width of cell.
WHAT MUST YOU TAKE INTO ACCOUNT IN CONSTRUCTING THE FRONT AXLE BEARING MECHANISM FROM PLASTIC CARD?
1. Decide on placement and size of holes
1. To cut down on horizontal side play a straw can be placed over the exposed axle.
a. Size of holes will be effected by diameter of straw.
b. Measure length of straws to place over the exposed axle.
ii. Decide how to bend card on straight edge.
2. Design and make own wheels
[ http://www.pluggingintothesun.rog.uk/centreofwheel.pdf], to affect:-
a. Effect speed
b. Ability to climb hills
c. Use ping pong ball or another component as a front wheel
3. Gears
a. Change gears for speed
b. to increase torque to climb hills
c. best for weather conditions/intensity of ligh
4. Track surface and condition can also be considered [ and to consider the nature of the track and more. http://www.pluggingintothesun.org.uk/case3.pdf].
a. How the cars are guided on the track i.e. free to move about or attached to a wire
5. Light intensity
a. Reflectors:- on board or hand-held
6. Weight
PROBLEM SOLVING
TThe gearbox motor assembly is designed so that the builder exercises his/her problem solving-forensic skills to diagnose the problem and get the motor working again [the gears meshing correctly and the wheels spinning].
Follow the steps below if the motor is not working (wheels not spinning) or gear box is not running smoothly, when motor is connected to PV cell and PV cell is facing toward a natural light source (The Sun):-
1. Remove rear wheel from lid side (part B) of casing. You may may need to firmly hold axle with a small pliers in order to pull off the wheel.
2. Remove the lid.
3. Remove the rear axle and cog
4. Remove the double gear cog
5. Hold the PV cell toward natural light source. Observe if the pinion gear on the shaft of the motor spins around – if it does it tells you that the PV cell and motor are working but there is friction being casing between the gears cogs and as a result they are not meshing smoothly to turn the wheels.
6. The Aadjustments are necessary asare described on page nine of the assembly instructions.
PACKAGING (TUBE) AND BODY SHELL DESIGN
The solar car kits are sent in a recycled cardboard tubing. The sleeve for the tubing can be customised with logos of the Local Authority, school and sponsors that provide funding for the purchase of training and educational kits. This is also the case for the body shell for the car. Blank templates are available for both the body shell and tube sleeve.
PAGE NINE
Problem: / Checks / Solutions:ENSURE THAT IN ALL GEAR RATIOS THAT THE MOTOR IS FITTED LEVEL INTO CASING A
-Bent axle Þ replace axle
-Gear teeth clogged Þ remove obstructions from within teeth
ratio 3:1
-Small motor shaft pinion gear and double gear not meshing smoothly Þ
adjust position of pinion gear on motor shaft near the top at about 1 mm below tip of shaft
-Right double gear wrong way round Þ
insert double gear on SHORTER RIGHT peg with 8 tooth gear towards bottom of spindle
-Single gear wrong way round Þ
insert flat side towards bottom of LONGER CENTRAL peg
ratio 9:1
-Small motor shaft gear and double gear not meshing smoothly Þ
adjust position of pinion gear 1mm near tip of motor shaft for gear ratio 9:1
-Double gear fitted in error Þ
remove large gear, it is not used in ratio 9:1
ratio 27:1
-Small motor shaft gear and double gear not meshing smoothly Þ
adjust position of pinion gear to BOTTOM of motor shaft for gear ratio 27:1
-Motor shaft gear may be meshing with both double gears : this jams the gearbox Þ
adjust position of motor PINION gear to mesh with ONLY RIGHT double gear cog only.
Car runs backwards / Polarity reversed Þ reverse terminal connections or reverse position of motor OR change gear ratio
Wheels do not turn / the car runs slowly / -Insufficient light intensity at solar cell Þ read 'How much light…' below
-Gear ratio not ideal for conditions Þ change gear ratio higher or lower
or alter diameter of wheels larger or smaller
-High electrical resistance Þ
check soundness of connections between motor plugs and solar terminals
or check for broken motor wires
-Rolling resistance too high Þ
try car on a smooth and level surface or change ratio
-Bent axle at either end Þ
remove axle and check it by rolling on a smooth surface, replace if not straight
-Axles not parallel Þ make adjustments with reference to assembly guide criteria
-Axle tight in bearing at either end Þ
pull wheels along axle and away from bearing to leave some free-play (1-2mm)
-Axle fitted tightly in hole of casing Þ move axle in hole to enlarge hole
[1] “Surveys consistently show that students lean most easily through practical experiments but science has been lately based on books and opinion and the controlled laboratory experiment has been replaced by the field trip” –– ‘Replacing lab time with debate puts pupils off’, by Liz Lightfoot, Education Editor, Telegraph, 11/06/07.
[2] David Garlovsky, TAE
[3] QCA
[4] Note: Children often do not have the opportunity when learning measurement that there are ‘factors’ to take into account. e.g. width of saw when cutting or if they do not measure something correctly.