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Pinewood Derby Rail Riding Q&A
What is rail riding?
If a pinewood derby car is aligned to run straight, but the track is not consistently level (very common), the car will contact the center guide rail both with the left wheels and the right wheels. If a raised wheel is used, then the raised wheel will likely contact the guide rail and start spinning. This will cancel any benefit attained from the raised wheel.
To compensate for the unknown condition of the track, the car can be intentionally steered such that the raised wheel does not contact the guide rail. For this discussion, we will assume that the left-front wheel is raised (if the right-front wheel is raised, then everything discussed below is reversed).
Adjust the right-front wheel so that the car drifts to the left - this keeps the left-front wheel from contacting the guide rail. With this drift, and if the rear wheels are aligned to run straight, then only the right-front wheel will contact the guide rail. To ensure that the right-rear wheel stays off the rail, the right-front of the car can be narrowed by 1/16 inch.
Tests show that when this Rail-rider technique is implemented, car performance is consistently faster than straight alignment.
Why does rail riding help?
Two major reasons: (1) The rear wheels of the car carry more weight, so there is a greater speed loss when a rear wheel contacts the guide rail than when a front wheel touches the guide rail. With rail riding, the rear wheels do not contact the guide rail. (2) When a raised front wheel is used, to gain a benefit it must not contact the guide rail and start spinning. Rail riding keeps the raised wheel off of the track.
Our pack does not allow a raised wheel. Can I still rail ride?
Yes, although the benefit is not as great, keeping the rear wheels off of the rail will still provide a performance benefit.
How much should the car drift?
The amount of drift should be 3 to 5 inches over 8 feet.
Must the axles be angled to rail ride?
Although, angled axles are commonly used when rail riding, rail riding itself does not mandate angled axles.
Are there tools to help with rail riding?
Yes, the Pro-Rail Rider Tool
is specifically designed to angle a front axle so that it can be steered. The tool can also be used to angle the other axles if desired. Note that a Pro-Axle Press
is required to use the Pro-Rail Rider tool.
If you do not want to bend an axle, then the desired steering correction can be accomplished by shimming one of the front axles, which will force the car to steer left or right.
Do I need access to a track to implement rail-riding?
No. In fact you can better set the proper drift using an alignment board. An alignment board is created as follows:
First, find a smooth, level surface that is 6 to 8 feet long. A smooth table top or a sheet of MDF (Home Depot, et al) work well.
Next, place a piece of masking tape down the middle of the surface, running from one end to the other. Better, use a marker to draw the center line. Measure accurately to make sure the line is straight and centered.
Raise one end of this ‘test track’ about three inches with books or a piece of wood. Level the test track side to side by rolling a large steel ball (or billiard ball) down the track. Use shims of wood or paper to level the track so that the ball follows the stripe.
Finally, place a pillow at the downhill end. To use the test track, place the car at the uphill end and align the edge of the car with the line. Make sure to place the car exactly even with the line on each test - a slight difference in placement will make a big difference in accuracy.
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