Peterborough PEO/OACETT/IEEE

2016 Engineering Month Challenge

Final Report

Overview:

The 2016 Engineering Month Challenge event, which is jointly planned and hosted by the

Peterborough PEO/OACETT/IEEE chapters was held on March 2, 2016 in the multi-

purpose room at the Evinrude Centre. This year’s event challenged the students to build

a solar powered car.

The Challenge:

Appendix B contains a copy of the handout that was provided to the students which

outlines the objectives and constraints of the event. The students were given a piece of

foam board to use as a base for their cars, as well as the solar cells, motor and an

assortment of axles, wheels & pulleys. They were also presented with a wide assortment

of miscellaneous materials to use for construction (popsicle sticks, rubber bands,

cardboard, pipe cleaners, hot glue etc….)

Total time given for construction was 2.5 hours, at which point the cars were submitted

for testing. A specially lit track was built which used three, 4 foot long banks of

fluorescent lights to provide enough direct illumination to power the cars. Originally it

was intended to use a ‘guide line’ made from fishing line and a hook on the cars to keep

the cars travelling in a straight line on the track. However this did not work as intended

and during the event some modification were made to add side bumpers to the track

instead. Volunteers also helped ‘nudge’ the cars as they travelled down the track if they

became hung up on the sides.

The goal of the challenge was for the students to design and build a solar powered car

that could traverse the track as quickly as possible.

The main principle of the event was to demonstrate to the students the principle of

conversion of energy - from solar to electrical to mechanical. Each team was given 2

solar cells, and during the introduction to the event they were given a lesson on the

difference output characteristics of the cells in a series or parallel connection, and also the

corresponding difference in performance of a connected electrical motor. They were also

given a brief re-fresher about gear and pulley ratios and mechanical advantage.

Appendix A contains a number of photos from the event.

Attendance:

The event was attended by 95 students in grades 10-12 split into 25teams from: Lakefield

College, St Peter’s, Holy Cross, TAS, St Mary’s, Crestwood and Kenner. Several

schools from Lindsay were also registered for the event, but could not attend due to

weather related bus cancellations the morning of the event.

Approximately 20 volunteers were in attendance to run the event.

There was a special guest speaker at the event, JP Pawliw - president of Generation Solar.

JP gave part of the opening presentation to the students, discussing the solar industry and

the various ways that solar energy can be captured and used.

Results:

For final testing, the cars were set at the starting section of the lit track, with a piece of

cardboard covering the lights directly above the car. When the cardboard was removed

the timer started. Points were given for how fast the cars travelled down the 12 foot track,

as well as how far past the lights they could ‘coast’ and also for written work. Appendix

B has the full details of the scoring.

The scores for the top placed teams were as follows:

1st Place: 98.85 Points: Holy Cross

Ethan Murphy

Maria Conlin

Ronan Sampson

Sarah Cowen

2nd

Place: 97.90 Points: Holy Cross

Maggie Logel

Hannah Trylinski

Jaedon McColl

Katie Cymbaluk

3rd

Place: 97.15 Points: TAS

Michael Bolin

Zack Calderwood

Luke Walsh

Nik Missiios

The Subaru Peterborough Award for the most innovative design was awarded to a team

from St Peter’s:

Julia Mandeljc

Regan Mahoney

Nic Bryenton Laura Connolly

The Cambium Award for the most effective team was awarded to a team from St Peter’s:

Eric vanBrank

Steve Moore

Dan Sullivan

Matt Sheward

Media Coverage:

The local media was contacted prior to the event, and representatives from the

Peterborough Examiner, SNAP and CHEX TV all attended and covered the event.

http://www.thepeterboroughexaminer.com/2016/03/03/holy-cross-secondary-school-

team-wins-annual-engineering-challenge

http://snapd.at/eeusn7.

http://www.chextv.com/2016/03/02/chex-daily-wednesday-march-2-2016/

(starting at 5:08)

http://www.chextv.com/2016/03/03/chex-daily-march-3-2016/

(We were featured in several segments, starting at 1:46 and 18:33)

Funding & Donations

As in past years, we had many generous sponsors who donated towards the event:

- Peterborough IEEE Chapter (trophies – approx. $350)

- Cambium Environmental ($200)

- Canadian Solar (Solar panels for event)

- Costco (drinks & snacks)

- Peterborough Subaru (design innovation trophy)

- Tim Horton’s (coffee and snacks for volunteers)

- Teva Canada (water bottles for give-aways)

- McCloskey International (Tote bags and pens)

- Central Smith (ice cream for snack)

- PrimaIP (juice boxes & snacks for students)

NEMOC also provided subsidized T-shirts for the volunteers, as well as Engineering

Month posters and some small prizes for the students.

NEM 2016 Income & Expense Summary

Expenses Evinrude Centre Rental $ 618.11

Trophies $ 395.33

Food (Kenner) $ 550.00

Building Supplies $ 910.34

Printing Expenses $ 102.80

Debrief Meeting $ 370.68

Total Expenses $ 2844.46

Funding

NEMOC $ 750.00

PVNCCDSB $ 500.00

IEEE $ 395.33

Cambium $ 200.00

OACETT $ 250.00

Total Funding $ 2095.33

Note: The difference between the funding and expenses above was covered by the

budgeted amounts allocated by the Peterborough PEO & IEEE chapters.

Appendix A: Event Photos

Figure 1: Students Working on Their Solar Car

Figure 2: The Completed Cars Prior to Final Testing

Figure 3: The Test Track and Timer

Figure 4: A Successful Run

Figure 5 Event Day Volunteers

Appendix B: Instruction Sheet

Engineering Challenge 2016

Questions and Evaluation

March 2, 2016

Objective

Design and build a solar powered car. Your will test your car on a purpose built lighted track. Your kit provides you with various construction materials as listed below. Marks are given based on the time your car takes to complete the lighted part of the track. You will receive bonus marks for the distance it moves beyond the lighted part of the track. Marks will also be given for your calculations, your diagram and answering some multiple choice questions. Marks can be earned for partial success and for your calculations.

Assignment:

Today you are building a solar powered car to race on a lighted track.

1) Your solar cars will be built using:

solar panels,

motor, pulleys,

wheels,

axles,

13 cm by 15 cm base,

L-brackets,

eye-hook.

The car must meet the following dimensions:

maximum length - 40 cm

maximum width - 20 cm

maximum height -18 cm

2) You must have one (1) eye hook (provided) mounted to the front underside of your car at a maximum height of 2.5 cm above the floor for a string line to pass through on the lighted track.

3) Your car will be marked on how fast (timed) it completes the lighted part of the track and how far (distance) it moves past the lighted part of the track. Both marks will be base on scaled system (to be determined based on the results).

Use the equations to calculate the velocity of an example solar car.

Draw a diagram of your solar car showing dimensions.

Answer the multiple choice questions related to the physics of the solar cars on the reporting sheets. (See reading material included in these instructions.

Competition Rules

Scoring based on:

time to complete 12' lighted part of the track (on a scale)

distance covered past lighted part of the track (on a scale) Starting the car:

your car will be placed on the track by a volunteer with a piece of paper covering the solar cells

When told to do so you will start your car by removing the piece of paper

General Safety Rules

The car will be placed on the track by one or more of the volunteers.

Keep well clear of the test area when testing is going on.

Marking:

# Description Points

1 Car meets all of the required dimensions 10

2 Car makes it to 12' distance 10

Time to complete 12' distance (on a scale) 60

Distance past 12' mark (on a scale) 10

3 Velocity and time Calculations 5

4 Diagram 10

5 Multiple Choice questions 5

Total 110

Timeline:

Activity Start Time

Introduction and Overview 10:00am

Construction Begins 10:30am

Lunch Arrives 12:00pm

Testing Begins 12:30pm

Written Work Submitted – Designs To Be Finalized 12:30pm

Testing ends and Results Announced 2:15pm

Pulley systems

Pulleys are used to change the speed, direction of rotation, or turning force or torque. A

pulley system consists of two pulley wheels each on a shaft, connected by a belt. This

transmits rotary motion and force from the input, or driver shaft, to the output, or

driven shaft.

Figure 5: General Pulley Diagram

If the pulley wheels are different sizes, the smaller one will spin faster than the larger

one. The difference in speed is called the velocity ratio. This is calculated using the

formula:

Velocity ratio = diameter of the driven pulley ÷ diameter of the driver pulley

If you know the velocity ratio and the input speed of a pulley system, you can calculate

the output speed using the formula:

Output speed = input speed ÷ velocity ratio

Worked example Work out the velocity ratio and the output speed of the pulley shown in the diagram

above.

Velocity ratio = 120mm ÷ 40mm = 3

Output speed = 100rpm ÷ 3 = 33.3 rpm

Torque

The velocity ratio of a pulley system also determines the amount of turning force or

torque transmitted from the driver pulley to the driven pulley. The formula is:

output torque = input torque × velocity ratio.

How Electric Motors Work

Magnets

The fundamental driving force behind all electric motors, whether brushed or brushless, AC or DC, is magnetism. We’ve probably all played with magnets at some time or other, and have learned about them in science class in elementary school.

Recall that any magnet has a north pole and a south pole (it just so happens that the earth is a magnet whose poles happen to correspond very roughly to the geographical poles, hence the names for the magnet’s poles). If you take two bar shaped magnets and line them up, they will be attracted to one another if one’s north pole is next to the other’s south pole. If you line them up north to north or south to south, they will repel each other. Opposites attract.

Consider an assembly of three magnets, as shown in Figure 2. The left and right hand magnets are fixed to some surface, and the center magnet is free to rotate about its center.

Figure 6: The central rotating magnet will turn until it is aligned with the two fixed magnets, north pole to

south pole.

Because of the attraction of opposite poles, the center magnet will rotate until it is aligned as in Figure 3.

Figure 7: Once aligned, it will resist being turned further.

Because the magnet has weight, and thus momentum, it would actually overshoot slightly, and then come back, overshoot again, and so on a few times before settling down.

Now, imagine we could work some magnetic magic and swap the center magnet’s north and south poles just as it overshoots the first time, as shown in Figure 4.

Figure 8: If we magically reverse the poles of the central magnet just before it comes to rest, it will keep

turning.

Instead of coming back, it would now be repelled by the fixed magnets, and keep turning so it can align itself in the other direction. Eventually, it would reach the state in Figure 5, which looks suspiciously like Figure 2.

Figure 9: Eventually, it will get back into the position it started from in Figure 1.

If we perform this pole-swapping every time the center magnet just finishes overshooting the aligned position, it would keep turning forever.

The problem is how to perform this feat of magnetic motion.

Electromagnets

The magnets we play with are called permanent magnets. These objects have a fixed magnetic field that’s always there. The poles are fixed relative to one another and relative to the physical magnet.

Another kind of magnet is the electromagnet. In its simplest form, this consists of an iron bar, wrapped in a coil of wire, as in Figure 6.

Figure 10: An electromagnet is just a piece of iron or other magnetic metal with a wire coil wrapped around

it.

By itself it does nothing. However, if you pass an electric current through the wire, a magnetic field is formed in the iron bar, and it becomes a magnet, as in Figure 7.

Figure 11: Applying current in one direction will produce a magnet.

If you turn off the current, it stops being a magnet (that’s a bit of a simplification, since in reality, it ends up remaining a weak magnet, but we needn’t concern ourselves with that for the moment).

So far, the electromagnet already seems quite useful, since we can use it to pick up iron, steel, or nickel objects, carry them somewhere, and then drop them by just turning off the power (wrecking yard cranes do this with entire automobiles).

The really interesting thing about an electromagnet is that its polarity (the location of the north and south poles) depends on the direction of current flow. If we pass the current through in the opposite direction, the electromagnet’s poles will be reversed, as shown in Figure 8.

Figure 12: Applying current in the opposite direction will produce a magnet with opposite polarity.

Eureka!

If we replace the central magnet in our set of three magnets with an electromagnet, as in Figure 9, we have the beginnings of an electric motor.

Figure 13: Replacing the central magnet in Figure 1 with an electromagnet gives us the beginnings of a motor.

Now we have two problems to solve: feeding the current to the rotating electromagnet without the wires getting twisted, and changing the direction of the current at the appropriate time.

Both of these problems are solved using two devices: a split-ring commutator, and a pair of brushes. Figure 10 illustrates these.

Figure 14: By adding a commutator (the semi-circular arcs) and brushes (the wide arrows), we can change the

polarity of the electromagnet as it turns.

The two semicircles are the commutator, and the two arrows are the brushes. The current is applied to the brushes, indicated by the "+" and "-" signs.

With the current as shown, the electromagnet will be repelled by the two permanent magnets, and it will turn clockwise. After it has turned almost half way around, it will be in the state shown in Figure 11.

Figure 15: The magnets are almost aligned, but soon, the polarity will reverse, sending the rotating

electromagnet on its way around once again.

Then, just as the magnet reaches the aligned state, the split in the commutator passes under the brushes, and then the current through the electromagnet reverses, which takes us back to the condition in Figure 10. As a result, the magnet keeps turning. We have a motor!

Connecting Solar Cells in Series or Parallel

Since you will have 2 solar cells to work with to build your car, you need to make a decision on whether to connect them in series or parallel. To illustrate the difference, let’s say that each cell has an output voltage of 0.5 Volts and an output current of 2 Amps.

A series connection puts them in a ‘chain’ or series and results in an increase in the overall output voltage:

Figure 16: Series Connection Example

A parallel connection connects them ‘side by side’ or in parallel, and results in an increase in the overall output current:

Figure 17: Parallel Connection Example

Note that since power is voltage X current (P = V x I), in each case the total power delivered to the motor terminals is the same.

That is: Series: P = V x I = 1V x 2A = 2W Parallel: P = V x I = 0.5V x 4A = 2W

So why does it matter how they are connected then??

It matters because the DC motor you are using will behave differently with the different types of connections.

For a DC motor like this one, the speed is proportional to the voltage, and the torque is proportional to the current. So if you want a higher speed, you need to provide more voltage, and if you want to be able to produce more torque, you need to supply more current.

So as you’re building your car you can experiment with the 2 different connection types to see which one gives the best performance with the design you’ve come up with.