Grand Prix Racing - How To Make A Fast Pinewood Car

Prepare the Wheels

Wheels from different kits have a few important differences. For the most part, they can be prepared in the same way. However, the different types of plastic and the molding processes used dictate that some kit wheels need more work than others. For best results, get access to an electric drill and have some fine sand paper (220 grit) and lintless paper or cloth ready. A hobby knife will be used first.

Remove Flash

Kit wheels most often come with little pieces of plastic still attached from the molding process. Carefully cut this molding flash off, using a hobby knife. Try to get a straight clean cut that is as flat as the rest of the surface. You can carefully plane off slight ridges in the plastic by cutting at a grazing angle. Do not apply much force when cutting at an angle or the knife could slip and cut you. Instead, rock the blade slowly along its edge to move it forward.

BSA: Get help from an adult to cut off the beads from around the outer edge of the Boy Scout wheels. It takes a good grip on the hard plastic wheel and steady thumb action with a hobby knife. The next best thing is to try to sand them off in the next procedure. The rumble you hear from beaded wheels is the sound of increased tread friction!

Round-up Tread

Now, mount each wheel on an axle or mandrel drill attachment as described below. Our purpose is two-fold. First, we want to check the roundness of the wheel and correct gross deviations. Second, it is good to sand the edges of the tread round if they are sharp. The inner edge of the tread will be rubbing the lane median and the outer edge will follow wood grain in the track if left sharp.

In order to sand and polish a wheel's tread:

Get some help in mounting and sanding the wheels with the drill. An improperly mounted axle or mandrel attachment can be dangerous.

  1. If you have a mandrel attachment, mount the wheel using it. Be sure the wheel is centered. If you can't center it, the wheel may be grossly out of round. If you don't have one, wrap a small triangular piece of masking tape around an axle - the point of the tape should extend away from the hub so the wheel can slip on more easily.
  2. Put the wheel on the axle snuggly. The wheel may slip on the tape, so be prepared to re-tape a couple of times until you discover just how much is needed.
  3. Mount in the drill chuck.
  4. If you can, anchor the drill in position with a vise.
  5. Secure 150 to 220 grit sand paper to a flat surface.
  6. Rotate the wheel - the direction won't matter if you polish it as described in the last step.
  7. Carefully press the tread flat on the sand paper. If the wheel slips in the taped axle, try re-taping.
  8. Sand over the outer edge of the tread to round it off.
  9. Sand around the inner edge of the tread to round it off.
  10. Polish the tread and inner edge of the wheel with the lintless cloth or paper. This works especially well with AWANA wheels since the irregularities left from sanding melt back into the soft plastic matrix without deforming the wheel. This melting is highly localized so the wheel is not distorted.
For the Novice
Caution: sanding or polishing for too long a time or with too fast a tool can create enough heat to melt your wheels.

Polish Wheel Bores

For some kit wheels this step is the difference between fast cars and very fast cars. Inspect the wheel bore (the hole the axle goes in) with a high power hand lens (like 10X).

AWANA: Most AWANA wheel bores contain a forest of scrapes and stress flakes left from the molding process.
BSA: BSA wheel bores appear highly polished. A few do sport gross irregularities.

This procedure can leave a mirror polish. Dimples in the bore won't be helped. If there are plastic filaments in dimples, raise that wheel to reduce its impact on speed. Try to get new ones if this happens on more than one or two wheels.

To polish (more accurately - burnish) your wheel bores, you'll need a polished, thin metal rod, awl, or needle-nose tweezer. A polished axle can work if you can get a good enough grip on the two ends with a wheel between. With the right implement, a child can easily do this.

  1. Insert the metal implement (burnisher) into the wheel bore.
  2. Get a good grip on both ends of the burnisher.
  3. Push down and roll the wheel on a flat surface at the same time. The pressure from pushing down and rolling melts the irregularities back into the plastic, even if you don't roll fast or push particularly hard. BSA wheels are harder, so more action is necessary.
  4. Checking with a strong hand lens is recommended, but not required - the bore will be better.

Detailing Lettered Wheels

Some clubs' kit wheels have raised lettering molded on them. This is the time to paint that lettering for a professional racing look. All you need to do is dab a toothpick in a bit of acrylic paint, and carefully touch the top of the lettering with it. Don't let the paint wet the sides of the letters or it will smear. But, if paint goes astray, just tweak it off with the dull edge of a hobby knife.

Some Grand Prix "drivers" prefer to sand off the lettering altogether. Do this if your organization's Grand Prix track does NOT allow enough space between lanes. Wheels from neighboring cars CAN rub together! Aerodynamic drag, however, is NOT a good reason to sand off the lettering. It's effect has yet to be measured!

How To Narrow Your Wheels

Often times, this procedure is disallowed by Grand Prix rules. The reason may be related to safety since many aspiring auto builders may employ dangerous methods to cut the plastic wheels. A slip of wheel under the pressure of a hobby knife could be very painful, possibly with permanent consequences.

You need to exercise care following this procedure. If done properly, your wheels will roll more easily. It will be as if your car only had two wheels! You will need a drill, small saw (coping, hack, drywall, etc.), and a vice. Don't do this procedure unless you use a vice or other holder to keep the saw from slipping. Get your parent or leader to supervise.

Take all precautions when sanding and narrowing your wheel tread.
  1. Wrap a small triangular piece of masking tape around an axle - the point of the tape should extend away from the hub so the wheel can slip on more easily
  2. Fit a wheel on the axle so it is snug but not permanently stuck on the tape. You may need to remove some tape.
  3. Insert the end of the axle into a drill chuck and tighten. Do not put the hub end in a drill chuck.
  4. If possible, clamp the drill in a vice to hold it steady.
  5. Mount the small saw in the grip of the vice or other holder teeth up. Clamp it tight so the saw cannot move. Be careful moving around the saw. If you forget it's there, you can get hurt. I've done that!
  6. Trigger the drill, holding it very steady over the teeth of the saw. The axis of the wheel should be at right angles to the axis of the saw blade. The goal is to make a groove in the tread that can be deepened gradually. Lightly press the wheel into the teeth of the saw at the place you want the tread cut. Care must be taken so it does not race off the blade. Hold it steady if not clamped down!
  7. Stop before you cut all the way through. You don't want the cut plastic to fly and hit someone in the eye or cause you to jump so your hand gets scratched on the blade.
  8. Separate the cut plastic by penetrating the groove with a hobby knife and running it around. It should separate easily. In any event, NEVER force a cut. Make many light passes with the blade instead.
  9. Sand off burrs and polish with fine grit (150 - 200) sand paper as described above.
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Grand Prix Racing - How To Make A Fast Pinewood Car
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