The test ramp has two modes of operation. On one side, the car is constrained only by the side rails. On the other side, the car is constrained by a center rail. This ramp was constructed from a 33 inch long piece of (leftover) 1X8 clear pine checked for trueness (no warp, no twist). Side rails are 1X2 clear pine. The center rail" is a common "promotional give-away" yard stick just over 1/8" thick. Of course, a correctly dimensioned center rail could be used.
Side rails and end rails are screwed to the ramp. Use care that the top and bottom of the end rails are parallel, side to side, with the ramp surface.
An optional improvement is to use 1-1/2" X 1/4" carriage bolts, self-tapped into the tops and bottoms of the end rails, at each end. These can be used to level the low end of the ramp. (Carriage bolts have domed tops for continuous adjustment and a square section under the head that can be used to screw them in or out as needed.)
Longer bolts could be used to raise the top end of the ramp (one in the center of each side), but 1/4" thick wood spacers are more convenient.
The center rail is glued and tacked (1/2" nails) to the ramp.
The end rails should be more than 1X2 in order to provide a positive stop for the cars. The height of the end rail on the Drift Alignment side should allow additional height for a movable scale for measuring drift.
Finish is amber shellac.
Storage is facilitated by addition of an eye screw centered on one end.
Drift Alignment Board
The Drift Alignment Board is used to align the dominant front wheel toe-in and to detect rear wheel friction imbalance.
A movable scale attached to the end of the drift alignment board aids in measuring the path deviation (drift) of the car as it runs down the alignment board.
Rear Wheel Alignment Board
The Rear Wheel Alignment Board is used to align the rear wheels. The influence of individual rear wheels is alternately exaggerated using Bias Weight as described in Aligning Rear Axles of Pinewood Derby Cars.