In a previous article (Volume 4, Issue 6) we discussed how to get the most benefit from three of the Pro-Tools(1): the Pro-Hub Tool, the Pro-Axle Press, and the Pro-Body Tool. This article will continue by discussing the Pro-Bore Polisher, the Pro-Wheel Mandrel, and the Pro-Wheel Shaver XT.
One of the most useful tools in building a pinewood derby car is a Wheel Mandrel. This tool is used to mount a wheel in the chuck of a drill to facilitate polishing the tread.
The Pro-Wheel Mandrel has several features that differentiate it from a standard mandrel:
1. Coned head to improve centering the wheel on the mandrel.
2. Knurled thumbscrew to simplify and speed-up mounting and removing wheels (the standard mandrel requires a flat blade screwdriver to mount and remove wheels).
3. Offset on mandrel body allows mounting of a BSA wheel with the spokes facing the drill. This simplifies polishing the inside edge of the wheel.
For best results when using a mandrel, first square the hub of the wheel on the side which will face the mandrel body. If the inside hub will face the mandrel body, then use the Pro-Hub Tool to square the inside wheel hub. If the outside hub will face the mandrel body, then use the Pro-Outer Hub Shaver to square that surface (BSA wheels only).
Note that the purpose of using a wheel mandrel is to mount a wheel in a drill for sanding and polishing the tread surface. This setup is not intended for ‘truing’. Wheel truing requires a tool with a mounted blade, such as a lathe or the Pro-Wheel Shavers.
PRO-WHEEL SHAVER XT
The Pro-Wheel Shaver XT provides the most cost effective way to create sets of perfectly round wheels from a standard molded wheel. With a little practice, the Pro-Wheel Shaver XT will create wheels that are accurate to one-thousandth (0.001) of an inch. This is generally better than wheels which are trued on hobby lathes, and approaches the quality of wheels trued on computerized lathes.
Why are round wheels so important? As the car travels down the track, out of round wheels cause the axles/car body to rise and fall. At slow speeds this causes very little trouble. But at top speed, the oscillation will cause the car to vibrate (which slows it down) and pull to one side (causing excessive contact with guide rails). Both of these are speed busters.
The Pro-Wheel Shaver XT will not only true the tread surface, but will also true the inside edge of the wheel. The most perfectly aligned cars will still touch the guide rail one or two times on the way down the track. If the inner edge of a wheel is not true, the contact may cause the car to kick away from the rail very quickly. Often this causes the car to begin zigzagging back and forth down the track, greatly diminishing speed. With trued inside edges the guide rail contact is softened resulting in a straighter run.
For best results, make several passes to get all four wheels trued to the same diameter. When changing wheels, to improve accuracy leave the blade at the previous setting and loosen the bolt holding the shaver to the Pro-Hub Tool. Rock the shaver back, remove and replace the wheel, then re-tighten the bolt. This ensures that the wheels are trued to the same diameter and minimizes cross-cuts on the tread (which occur if the wheel is removed without loosening the bolt. If there is not enough ‘play’ to allow the shaver to be rocked, rotate the wheel in the opposite direction while removing.
Make sure to make a final pass on the wheels to remove all possible material. These final turns will remove fine, fuzzy plastic shavings, which improves the finish on the wheel.
The bore on an injection molded wheel typically has pits and bumps which are visible at magnification. These defects will reduce the spin time of the wheel.
The Pro-Bore Polisher is used to polish the wheel bores, resulting in a smooth, virtually defect free bore surface. The polisher uses a pipe cleaner as the polishing brush, and an industrial grade plastic polish as the abrasive. The polisher holds the pipe cleaner stiff and straight, improving the pressure on the wheel bore.
For best results run the drill on a slow speed, and do not put a wheel on the polisher while the drill is spinning. Do not use a Dremel-type tool, as the high RPM can damage the bore.
We wish you the best when using your Pro-Tools. If you have any pinewood derby tips or tricks that you have learned regarding these tools, please send them to me and I will share them in future editions of this newsletter.
(1) The Pro-Tool line, manufactured by DerbyWorx includes:
Pro-Outer Hub Shaver Tool
Pro-Wheel Shaver XT
The Pro-Tools are available at Maximum Velocity.
From Pinewood Derby Times Volume 4, Issue 9
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