02
03
Pinewood Derby Stories and Photos from Maximum Velocity
04
05
15
16
19
20
21
22
23
24
25
26
27
28
31
32
33
34
Careful work and some basic principles are the keys to making your car streak down the track at top speed. Some key areas that need to be considered when designing and building the ultimate racing machine are: good aerodynamics, maximum weight, proper weight distribution, reduction of friction, reduction of inertia, and proper wheel alignment. Discussing all of these areas would require a book1, so lets focus on one aspect of car building: proper wheel alignment.
Basics of Alignment
Proper wheel alignment basically means that all of the wheels are pointing in exactly the same direction, and sit straight up and down. But of course the wheels do not determine their own direction. Instead, it is the axles that determine whether the wheels will go straight.2
With most car kits proper axle positioning comes from two factors:
Accurate axle slots, and
Straight axles.
Let's look at each of these factors.
Accurate Axle Slots
The axle slots cut into the bottom of the car determine how the axles will mount on the car. So, one of the first steps in building a pinewood derby car is to inspect the slots to see if they are square with the block, and are consistently cut to the same depth. The best way to check if the slots are square to the block is to use a tool called a 'Square'. But if you don't have a square, align the long side of a piece of note book paper with the side of the car and see if each slot aligns with the top of the paper.
The depth of the slot can be measured with a ruler. Check the depth of both slots on the left side and on the right side of the block.
If either slot is not square, or if the slot depth is not the same at all four points then the block needs to be replaced.
Straight Axles
The next factor that must be checked is the straightness of the axles. A simple way to check whether the axles are straight is to insert an axle into the chuck of a drill (point first) and lightly tighten the chuck of the drill. Start the drill (slow speed) and observe the axle. The axle should appear to spin straight, without any side-to-side wobble. Any bent axles should be replaced or straightened with the Pro-Axle Press.3
Adjusting the Alignment
If the axle slots and the axles are all straight and true, then alignment will be greatly simplified. However, other factors (center of gravity of the car, wheels, et al) do have a minor influence on alignment so a slight adjustment will likely be needed. After the car body is completed, attach the wheels and axles and test the alignment by rolling the car on a smooth and flat surface.
Better yet, get a sheet of 1/8 smooth siding material at a home store, put a strip of tape down the middle, block up one end, and put a pillow at the bottom. Use a 'level' to make sure that the board is not tilted to the left or right (many garages and carports are angled to allow water to run off). Then roll the car down the board using the tape strip as a guide to determine if the car rolls straight.
If the car moves more than 1" in an 8 foot distance, then an alignment adjustment is needed. One way to make an adjustment is to remove a front wheel/axle, and EVER-SO-SLIGHTLY bend the axle at the point where it meets the side of the car (clamp the axle in a vise, and LIGHTLY tap the side of the axle with a hammer). Then replace the axle and repeatedly test the alignment and rotate the axle (with a pair of pliers until the car goes straight.
Conclusion
Proper wheel alignment is a critical factor in car performance. Just as we are told that "... strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it."4, so also straight and narrow is the way to victory in a pinewood derby race. I encourage you to take the straight and narrow way to find victory in your life, and to find victory in your pinewood race.
2Wheels do have some effect on alignment. If a wheel is not perfectly round, it will make the car vibrate which will affect the direction of travel. Also, if the wheels are not exactly the same diameter, then the car will not sit straight which also affects the direction of travel. If you want to ensure that all of the wheels are perfectly round and of the same diameter, then a machine lathe can be used to true the wheels. Since most people do not have access to this type of machine, Maximum Velocity has introduced the Pro-Wheel Shaver. The tool is basically an affordable, hand powered lathe for pinewood derby wheels. For more information on the Pro-Wheel Shaver, Please Click Here.