Learn to Build A Winner

A Textbook for

High Performance

Pinewood Derby Car

Design and Construction

by

Stan Pope

Morton, Illinois

Copyright 1995, 1999, 2002 © by Stan Pope, All rights reserved.

Forward

Why this book? Like all Cubmasters, I have watched many Pinewood Derby races. Among those races, I have seen cars, propelled only by gravity and the hopes of their builders, dash those hopes as they grind to a halt before reaching the finish line. In my own pack, I have tried to avoid those episodes of disappointment by providing instruction and guidance to the parent-son teams that will build their cars. The content of this guidance has grown from "avoiding the show-stoppers" and "just the basics" to "high performance racing." In subsequent years I extended that teaching to other packs through Roundtable and POW WOW sessions. This book is the next logical step.

The number one show-stopper for a car is "failure at inspection." This means that the car does not conform to the applicable rules of construction. There are no "universal rules" on PWD construction. Find out what your local rules are and follow them, or prepare to explain to your Cub Scout why he can't race today.

Pinewood Derby Cars have much to teach our youth... science, technology, trust, and sportsmanship. They provide an opportunity for a boy and his parent (partner) to build mutual trust and understanding. They are an experimental testbed for science that can be explored even by the youngest scout. The car that does not reach the finish line dashes its builder's immediate hopes and may well prevent him from coming back to try again. On the other hand, some initial successes can spur him on to learn more.

This book identifies and explores important Pinewood Racer performance variables and their relationships. It does not pretend to tell "how to build a winner". Rather, it provides a formula for "learning to build a winner". It doesn't just tell the answers... it tells where and how to look for more of the answers.

To this end, the section on Science teaches the relevant concepts, the section on Woodshop shows some ways to implement the concepts, and the Test at the end provides an opportunity for the serious student to go beyond the sample designs to produce an even more superior race car. If any of these three are skipped, the student is shortchanged.

I. Introduction

II. The Problem

III. Science 101

IV. Woodshop 101

V. Afterward

VI. Addendum - Non-indexed Topics

Angular Inertia of the Car Body
G-forces from Direction Change
Hub Inside Diameter Treatment
Hub Inside Diameter Reduction
Height of Center of Mass Above Wheelbase
Weighted Wheels
Weight Distribution
Distributing Wheel/Axle Frictions
Balancing Axle Frictions
Review of Literature

VII. Change History

VIII. Index

IX. List of Illustrations

X. Test (Don't miss this!)

Introduction

In this book we will first define the "Pinewood Derby Problem". The world has so many "answers for which there are no questions" that, before we make another large pile of answers, let us first decide upon the question. Much of what I have read about Pinewood Derby Car design seems useless because the assumptions were not identified. (The most common omission has been "What kind of track must the Car run on?")

Then we will look at what scientists have discovered. "Science" is all about how the world of objects and forces interrelate with each other. This is the "why" part of the book, which will serve as a guide when we look at the "hows" later. This section tells what is probably important. This presentation is mainly qualitative. If you wish to "quantify", then I refer you to almost any high school physics books.

Next we will explore some "hows". We will look at some of the ways to accomplish what science tells us should be done. This section tries to be very practical. The more difficult techniques are presented in detail. Some "designs" are shown. None look like what you will see at the local stock car races, road races, or even at "Indy", because these designs are some of the "answers" to the "Pinewood Derby Problem".

Then, we will plan for "race day and beyond."

Finally, take the test. It will allow you to apply what you have learned and lead you to even better designs.

Cub Scouts learn best by "doing". It is important that the Cub Scout be actively involved in as much of the process as possible. The role of the adult partner should be as a guide and teacher. I recommend a "hands over hands" approach to the "teaching", especially in using tools. His hands hold the tool... your hands hold his to guide him as he learns its use.