Body Preparation

Once you have designed your car and prepared the wheels and axles, it is time to prepare the body and assemble the car. A lot of what follows is just common-sense carpentry but there are a few things to keep in mind even while creating wood chips.

The one power tool which is really required is a drill press. Otherwise, you will have a hard time getting the axle holes drilled square, and this is essential to having the car run straight and true. If you don't have a drill press, check with your neighbors or ask the high school shop teacher for five minutes on one in the woodworking shop. That's literally all it will take.

Although I have mentioned using a bandsaw to rough-cut the body, you can also use a coping saw and do it all by hand. It's slower but easier on the fingers, since a bandsaw isn't the sort of tool for a Cub Scout age boy to be using. My son and I split the duties on his car at that point. I drilled the axle holes and weight holes and did the rough cut to shape. From there on, sanding and prep of the body was up to him. An oscillating pad sander makes quick work of smoothing out the saw marks but doesn't eat fingers.

Tools and materials you'll need:

  • Safety goggles for both you and your son
  • Drill Press
  • 1/2" brad-point drill bit
  • Brad-point drill bit to fit your weights (for the ones we used, the same 1/2" drill was fine)
  • Combination pilot/clearance/countersink bit for #4 wood screws
  • A piece of 0.040" to 0.062" aluminum, 8" long
  • A piece of 0.015" to 0.030" shim stock, 1" square
  • Band saw (easy way) or coping saw (hard way)
  • Dremel or other motorized tool (optional)
  • Electric sander (easy way) or elbow grease (hard way)
  • Aluminum oxide (dry) sandpaper, 100, 150, 220 grit
  • Paint in your favorite color(s)
  • Extra set of raw axle nails
  • A couple of soft cotton rags
  • Automotive wax

Before you start carving on your block of wood, let's think about what we need to do first! Remember that the axle holes need to be square with the edges of the block and all parallel to each other. That means we will drill holes for the axles before doing anything else. (Just a reminder!)

Steps in the process:

  • Lay out the locations of the axle holes. Remember to locate one of the front holes 1/32" to 1/16" higher than the other three holes, if you are allowed to have only three wheels rolling.
  • Lay out the locations of the weight holes, if you are using my trick of rod stock buried in the body.
  • Lay out the locations of the front axle "steering" holes on the bottom of the block.
  • Lay out the locations of the weight tuning holes on the bottom of the block.
  • Hold the block in the 6" machinist's vise, with the bottom side of the block at the fixed jaw of the vise. Place the 0.062" aluminum under the opposite end of the vise so you tip the vise "up" very slightly. This angles the axles by a similar amount and helps the wheels to run "out" against the nail heads instead of "in" against the body, but doesn't put so much of an angle on them that the wheels look like they're running "cocked." Drill the axle holes, selecting a bit which is provides a tight press fit for the axle nails. (Experiment on a scrap area of the body to find the best fit. If you have access to a machinist's set of numbered drills, the "best fit" is somewhere around a number 40 through 42 drill bit.) Make sure you go deep enough to bottom the nails. (We generally go halfway through from both sides.)
  • Drill the weight holes using a drill bit chosen for a loose fit for the rod stock you'll be using for weights. (Assuming you're using rod stock in the first place.)
  • Drill the "steering" holes up from the bottom of the block and deep enough that they will be exposed top and bottom once you have cut out the body.
  • Drill the countersunk holes into the bottom of the body where you will install the weight tuning screws. Note: We drilled these holes between the first and second weight holes. The only strong requirement for that is that the body be at least 1/2" thick at the point you drill the holes and that you don't hit the rear axles where they come into the body. Take a look at the drawings of our car bodies for details.
  • Now lay out your lines to cut out the body and do your rough cut either with a power (band) saw or by hand.
  • If you are doing additional shaping, now is the time to bring out the Dremel and some sanding drums and go to it. However, leave the areas immediately adjacent to the axle holes nice and flat and square.
  • Sand the body smooth, starting with 100 grit sandpaper on the saw cuts and working down to 220 grit everywhere. Use a sanding block or pad sander on the areas next to the axle holes, again to keep them flat and square.
  • Now prime and paint the car as desired. The extra set of axle nails will come in handy at this point, especially if you are using spray paint or (as we did) an artist's airbrush. By stuffing your axle holes with the spare axles, you prevent building up excess paint in them and making it harder to mount your axles. You will want to build up several coats of paint for a good finish, with light sanding using 220-grit sandpaper between coats to promote adhesion of the next coat.
  • After the paint has had at least 24 hours to dry, you can put a final shine on the body using automotive wax. If you are applying stickers, decals, or other decorations, you should do so before waxing the body or they won't stick properly.