1. Copyright © 2009 by Stan Pope Page 1 Pinewood Derby Performance Design An introduction to making a high performance Pinewood Derby car Copyright 2003, 2009 by Stan Pope, all rights reserved.

2. Copyright © 2009 by Stan Pope Page 2 Part of this presentation is oriented around this idea...

3. Copyright © 2009 by Stan Pope Page 3 Regardless of the lane in which you race, you should race in: The steepest lane, The shortest lane, The smoothest lane, and The slickest lane

4. Copyright © 2009 by Stan Pope Page 4 Then, you will be racing in... The fastest lane!

5. Copyright © 2009 by Stan Pope Page 5 But if you don't get to pick the lane, how do you make sure to get the fastest lane? By what you do to your car! That is why this presentation exists.

6. Copyright © 2009 by Stan Pope Page 6 Modern Track Starting Line Finish Line

7. Copyright © 2009 by Stan Pope Page 7 Race in the Steepest Lane

8. Copyright © 2009 by Stan Pope Page 8 Which car wins? Which car is fastest at the bottom?

9. Copyright © 2009 by Stan Pope Page 9 Why? Gravity! Gravity and the mass of the car create a force along the line of the track. If the track is steeper then more of the gravity force goes to pull the car forward.

10. Copyright © 2009 by Stan Pope Page 10 Car A has farther to fall, so it has more potential energy to turn into speed.

11. Copyright © 2009 by Stan Pope Page 11 How do I make my lane steeper? Physics says that “my lane” is the path followed by my car's center of mass.

12. Copyright © 2009 by Stan Pope Page 12 a b Ha Hb Center of Mass

13. Copyright © 2009 by Stan Pope Page 13 It isn't about weight in the back pushing the car down the track... Or about weight in the front pulling the car down the track. It is about how far the car drops as it goes down the track.

14. Copyright © 2009 by Stan Pope Page 14 The amount of drop determines the amount of “potential energy” that can be turned into speed. With modern tracks, drop increases as center of mass is moved farther back in the car.

15. Copyright © 2009 by Stan Pope Page 15 Make your car as long as rules allow. Locate the center of mass (balance point) as far back as stability allows. “Stability” includes “sticking to the track” and not sliding sideways.

16. Copyright © 2009 by Stan Pope Page 16 This applies to modern tracks which start on a slope and flatten out toward the finish line. This does not apply to older style tracks which have constant slope or which have both increasing slope near the starting line.

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18. Copyright © 2009 by Stan Pope Page 18 Race in the Shortest Lane

19. Copyright © 2009 by Stan Pope Page 19 A B Which car wins?

20. Copyright © 2009 by Stan Pope Page 20 Set axles so that car runs straight and level. Align as required.

21. Copyright © 2009 by Stan Pope Page 21 You may analyze the track and find that raising the CM reduces the distance that it must travel. Right! But this usually fails because the CM is so far from the wheels. You must be on a very smooth track, and your wheels must create very little oscillation.

22. Copyright © 2009 by Stan Pope Page 22 Race in the Smoothest Lane

23. Copyright © 2009 by Stan Pope Page 23 Which car wins?

24. Copyright © 2009 by Stan Pope Page 24 A B C How does the car's center of mass move as these wheels roll?

25. Copyright © 2009 by Stan Pope Page 25 A B Which car handles bumps best?

26. Copyright © 2009 by Stan Pope Page 26  Wheels round  Bore centered and smooth  Tread smooth ‏  Wheelbase extended (but not too much!)‏

27. Copyright © 2009 by Stan Pope Page 27 Race in the Slickest Lane

28. Copyright © 2009 by Stan Pope Page 28 Identify the frictions and losses. Eliminate losses, if possible. Make frictions as small as possible. Move friction to where it hurts least.

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32. Copyright © 2009 by Stan Pope Page 32 Eliminate Loss If allowed, lift a front wheel. If allowed to lift a front wheel, avoid ever spinning it up. Keep most heavily loaded wheels off the rail.

33. Copyright © 2009 by Stan Pope Page 33 Are these criteria always true? Well, no, they aren't. There are some exceptions. However, the exceptions are very few.

34. Copyright © 2009 by Stan Pope Page 34 When aren't these criteria true?  Different track styles  CM too far back  Front wheel too far forward

35. Copyright © 2009 by Stan Pope Page 35 Some Key Steps

36. Copyright © 2009 by Stan Pope Page 36 Preparing Axles

37. Copyright © 2009 by Stan Pope Page 37 To hold nail while filing sholders near nail point

38. Copyright © 2009 by Stan Pope Page 38 Then chuck in drill and clean under nail head.

39. Copyright © 2009 by Stan Pope Page 39 Preparing Wheels

40. Copyright © 2009 by Stan Pope Page 40 A drill press can work as a lathe. Wheel is held in a mandrel and rotated as it is moved past a cutter.

41. Copyright © 2009 by Stan Pope Page 41 Here, the cutter is held in a piece of wood. The cutter assembly is held, by hand, against a guide bar. The cutter is moved gradually closer to a stop block on the guide bar.

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43. Copyright © 2009 by Stan Pope Page 43 Of course, sandpaper against a block of wood can also be used. Make sure the block is square!

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45. Copyright © 2009 by Stan Pope Page 45 Body Preparation Drilling Axle Holes

46. Copyright © 2009 by Stan Pope Page 46 Here is a homemade drill guide to help keep the holes perpendicular to the car body.

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48. Copyright © 2009 by Stan Pope Page 48 Layout car body plan on block. Locate holes. Drill first!

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53. Copyright © 2009 by Stan Pope Page 53 Here is a tool that is supposed to produce perpendicular holes even with a hand drill!

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56. Copyright © 2009 by Stan Pope Page 56 Good Racing!

57. Copyright © 2009 by Stan Pope Page 57 Use of This Presentation Permission is granted... You may use the presentation as-is within your organization. You may add, remove, or alter slides for use within your organization provided that this page is retained and that the original copyright assertion remains on all retained content.

58. Copyright © 2009 by Stan Pope Page 58 Technical Note This presentation was prepared using the “Impress” feature of OpenOffice.org 2.4. OpenOffice is free for individual use through a project supported by Sun Microsystems, Inc. Software is available at http://www.openoffice.org