Pinewood Derby Stories and Photos from Maximum Velocity
Rail-Riding - Getting that Extra Speed
By Randy Davis
If you have spent any time on the Internet researching pinewood derby racing, you will have ran across the term "rail-riding". This alignment technique had been used for many years by a select few, but became popular around 2008.(1) The Pro-Rail Rider Tool, the Pro-Axle Bender and other tools were introduced soon after to facilitate the implementation of this technique.
But with all of the tools, videos, and documentation available, I still get many calls from confused car builders about rail-riding. Therefore, the intent of today's article is to organize the many facets of rail-riding in such a way that clarity can be attained.
WHAT IS RAIL RIDING
When a pinewood derby car rolls down the track, it will contact the center guide rail.(2) Each time a wheel contacts the rail, some performance will be lost. Moreover, when a rear wheel contacts the rail, even more performance is lost since the rear wheels carry the majority of the car's weight.
So, the fastest car (all other factors being equal) is one that never touches a guide rail. It would seem then that setting the cars alignment to go straight would be the best bet. This might work if the track was perfectly smooth and level, but we all know that is a pipe dream. All tracks will lean one way or another (and some lean both ways alternately by track section). So, a car that is set to run straight will follow the lean of the track, resulting in contact with one or both wheels on one side of the car.(3) In addition, if the car is a three-wheeler (with a raised, non-spinning wheel) and the raised wheel contacts the rail, the advantage of the raised wheel is lost.
How can we compensate for this? Recognizing that the least amount of loss occurs when the lightest loaded wheel (a front wheel) contacts a rail, if we could set the car's alignment so that a dominant front wheel is the only wheel that contacts the rail (the non-raised wheel for three-wheel cars; your choice of wheels for a four-wheel car), we would achieve the least guide rail losses. This is the basis of rail-riding.