Make Your Wheels Round and Your Pinewood Derby Car Fast 

It is best to use a Drill to power the lathe. A corded Dremel with a low speed setting can also work.

The Mini-lathe can be used with the drill to the left of the lathe or with the drill to the right of the lathe.  Use whichever you prefer.

Securing the Mini-lathe and the Drill

Position the drill so that the axis of the drill is parallel to the axis of the lathe axle shaft and at the correct height to accept the nose piece of the drill . Adjust the height of the lathe to match the drill height by removing the thin wood spacer under the lathe and/or add the thin cardboard spacer. 

Four nails are included to prevent the drill from shifting which could bend the axle shaft. When in place, the nails will surround the drill and hold it in place. The drill can be easily removed if needed. To place the nails, use a pencil to mark four positions on the board as shown with the red dots in the above photo.  The marks should be slightly toward the drill so that the nails will have a small outward angle. Remove the drill then pound the nails 1/4 inch into the board at the marks. Position the drill back on the lathe. Bend the nails if needed to provide a secure fit.

Mounting the Wheels

1. Insert one of the shaft collars onto the axle shaft 1 ½ inch from the edge of the axle shaft, locking it in place using the allen wrench to tighten the insert screw. The allen wrench is stored in the end of the lathe just under the red mark. This is to pre-position the wheels in the center of the lathe.

Then insert the following pieces in this order to construct the “mounted wheel assembly”:

1. Rubber washer
2. Rubber grommet
3. Derby car wheel with the back facing the grommet so that the grommet goes over the wheel hub inside the back of the wheel
4. Three more derby car wheels facing in the same direction.
5. Rubber washer
6. Second shaft collar (keep it unlocked)

Insert the mounted wheel assembly into the lathe above the spring wires with the second unlocked shaft collar against a column of the lathe. Position your index and middle fingers on the locked shaft collar, and firmly press the collar toward the unlocked shaft collar. Now set the inset screw on the unlocked shaft collar with the allen wrench to lock the assembly. The wheels should be firmly in place (no wheels freely rotating) on the axle shaft between the shaft collars.

Press the axle shaft down and into the J- channels of the lathe columns. The spring wires will compress the axle shaft once it is set at the tip of the J. Be sure that the axle shaft is at the top (tip) of the J slot in both columns to insure a parallel alignment of the axle shaft to the sliding platform.

Insert the sliding wedge platform into the lathe with the long surface on top. The lathe is now ready for Wheel Balancing (size and circumference) and Tread truing (polishing and removal of surface mold imperfections).

Using the Lathe

Objectives

• Remove any wheel mold defects or imperfections of the wheel tread and to make the wheel circumferences round and of equal size.
• Set the wheel tread flat and parallel to the axis of wheel rotation. This helps to minimize axle friction at the inner and outer aspect of the wheel axle bore and promotes preferential wheel rotation in the center of the wheel axle (not favoring the nail axle head or the wood body of the car), further reducing friction and optimizing wheel performance.

1. Using the wet/dry sandpaper palettes (sandpaper adhered to plastic cards) 320 to 1200 grit, apply water to the sandpaper surface using a finger dipped in a cup of water or a moist cloth. The water minimizes heat transfer to the plastic wheel. A slow speed on the drill also minimizes this heat transfer.
2. Place the 320 grit palette on the top surface of the sliding platform. Now with the bottom of the wheels rotating towards you at slow speed, advance the platform holding the sandpaper palette in place. The projecting tread imperfections will begin to sand first. Continue sanding until no original surface remains on any of the wheel treads. The original surface is shinier than the sanded surface. Note: Some race rules require that some of the original tread must remain on the wheel. In this case, stop when a about a half inch of original tread still exists.
3. Repeat step 2 using the different grits of sandpaper in order from course to fine to further polish the tread. The objective is to remove the mold imperfections so the wheels will be balanced, flat, trued and polished.
4. Additional polishing: Remove the wheels from the Mini-lathe and using either the 800 or 1200 fine grit sandpaper palette, sand the wheel hubs and wheel rims lightly. This will fine polish the rims and the wheel hubs to minimize friction when rim contact is made with the track guide rail or when hub contact is made with the wood body of the car.

Manufacturer: Wynsum Professional Derby Tools LLC