Upload
austin-blair
View
224
Download
0
Embed Size (px)
Citation preview
Copyright © 2009 by Stan Pope Page 1
Pinewood Derby Performance
DesignAn introduction to
making a high performance
Pinewood Derby car
Copyright 2003, 2009 by Stan Pope, all rights reserved.
Copyright © 2009 by Stan Pope Page 2
Part of this presentation is oriented around this idea ...
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
Copyright © 2009 by Stan Pope Page 4
Then, you will be racing in ... The fastest lane!
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.
Copyright © 2009 by Stan Pope Page 6
Modern Track
Starting Line
Finish Line
Copyright © 2009 by Stan Pope Page 7
Race in the
Steepest Lane
Copyright © 2009 by Stan Pope Page 8
Which car wins?
Which car is fastest at the bottom?
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.
Copyright © 2009 by Stan Pope Page 10
Car A has farther to fall,
so it has more potential energy to turn into speed.
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.
Copyright © 2009 by Stan Pope Page 12
a
b
Ha
Hb
Center of Mass
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.
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.
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.
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.
Copyright © 2009 by Stan Pope Page 17
Copyright © 2009 by Stan Pope Page 18
Race in the
Shortest Lane
Copyright © 2009 by Stan Pope Page 19
A
B
Which car wins?
Copyright © 2009 by Stan Pope Page 20
Set axles so that car runs straight and level.
Align as required.
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.
Copyright © 2009 by Stan Pope Page 22
Race in the
Smoothest Lane
Copyright © 2009 by Stan Pope Page 23
Which car wins?
Copyright © 2009 by Stan Pope Page 24
A
BC
How does the car's center of mass move as these wheels roll?
Copyright © 2009 by Stan Pope Page 25
A
B
Which car handles bumps best?
Copyright © 2009 by Stan Pope Page 26
Wheels roundBore centered and smoothTread smooth Wheelbase extended (but not too much!)
Copyright © 2009 by Stan Pope Page 27
Race in the
Slickest Lane
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.
Copyright © 2009 by Stan Pope Page 29
Copyright © 2009 by Stan Pope Page 30
Copyright © 2009 by Stan Pope Page 31
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.
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.
Copyright © 2009 by Stan Pope Page 34
When aren't these criteria true?
Different track stylesCM too far backFront wheel too far forward
Copyright © 2009 by Stan Pope Page 35
Some Key Steps
Copyright © 2009 by Stan Pope Page 36
Preparing Axles
Copyright © 2009 by Stan Pope Page 37
To hold nail while filing sholders near nail point
Copyright © 2009 by Stan Pope Page 38
Then chuck in drill and clean under nail head.
Copyright © 2009 by Stan Pope Page 39
Preparing Wheels
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.
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.
Copyright © 2009 by Stan Pope Page 42
Copyright © 2009 by Stan Pope Page 43
Of course, sandpaper against ablock of wood can also be used.
Make sure the block is square!
Copyright © 2009 by Stan Pope Page 44
Copyright © 2009 by Stan Pope Page 45
Body Preparation
Drilling Axle Holes
Copyright © 2009 by Stan Pope Page 46
Here is a homemade drill guideto help keep the holes perpendicular to the car body.
Copyright © 2009 by Stan Pope Page 47
Copyright © 2009 by Stan Pope Page 48
Layout car body plan on block.
Locate holes.
Drill first!
Copyright © 2009 by Stan Pope Page 49
Copyright © 2009 by Stan Pope Page 50
Copyright © 2009 by Stan Pope Page 51
Copyright © 2009 by Stan Pope Page 52
Copyright © 2009 by Stan Pope Page 53
Here is a tool that is supposedto produce perpendicular holes even with a hand drill!
Copyright © 2009 by Stan Pope Page 54
Copyright © 2009 by Stan Pope Page 55
Copyright © 2009 by Stan Pope Page 56
Good Racing!
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.
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