Latest update: 9/16/97
Technical Changes for HTML 3.2 Conformance 12/28/97
Copyright 1995, 1997 © by Stan Pope. All rights reserved.
A. Check your block for squareness. Every one that I have checked has been fine, but if it were off a bit, marking profiles correctly would be difficult. If the error is too much to suit you, pick one side of the block for reference to be used when cutting and drilling (difficult), rework the block (very difficult), or discard the block and try another kit.
When holding the try square gently against the corner of a block, look along the surface of the block, checking for light under the blade of the try square.
B. Check your block for length. Most are slightly longer than 7 inches.
If the block is somewhat too long, compensate when locating holes for axles. (On race day, it is easy to file 1/16" off the front of the car, but it is difficult to move the front wheels back 1/16"!
You may wish to wait until the nose is being shaped before shortening the block.
You should also recheck length after filling the back with lead, in case the lead extends further back than planned.
C. The rear axle location should be approximately 5/8 inches from the rear of the car. Check the actual size of your wheel, after dressing, if you want to cut it closer than this. Ideally, the back of the rear wheels will be even with the back of the car.
Also, watch the size of the lead inserts to assure that they do not extend further back than planned.
D. The front axle location should be approximately 3/4 inches from the front of the car. This gives you a little room to adjust the car's length if "7 inches on race day is shorter than the 7 inches measure your used to build the car." One front axle hole should be about 1/16" higher than the other if your rules permit.
F. Draw profile on each side of the block, carefully marking the location of the axle holes. (Use the bottom of the block as reference plane.)
Mark with "cross hairs" instead of a single dot.
If local rules permit, one for the front wheels should be about 1/16" higher than the other. (This applies to cars which will race on "modern" tracks. A more general statement is that one of the wheels on the lightest end of the car should be 1/16" higher than the other.)
Then carefully drill the axle holes using a #43 drill bit (0.089") to a depth of about 3/4 inches. Every possible care should be taken that the holes are perpendicular to the side of the block and drilled where marked.
A drill press is a must here. Ask around; someone nearby has one and will assist you in usage. This makes later wheel alignment easier/possible.
A few practice runs on scrap wood is a good idea. When beginning to drill a hole, just barely touch the drill to the wood, then check for proper location, adjusting as required.
If slots are being used, locate the hole so that the drill bit just touches the top of the slot... except for that one wheel that will be raised 1/16"! Drill it slightly above the top of the slot! When drilling in the slots, carefully center the drill. Otherwise, the wood will deflect the drill bit and the hole will not be well aligned.
G. Cut the slice of wood off the bottom. Be careful to keep this cut perpendicular to the side of the block.
As always, cut on the "waste side" of your guide lines!
Here, for convenience, I sometimes deviate from my otherwise strict rule of "the Cub Scout builds the whole car"... I will do this cut on a table saw. It is a long, tedious job with a hand saw, and quite a bit to try to remove with a block plane.
The piece can be tacked to a larger piece for safer feeding through the saw. (I have the Cub Scout do that tacking job for me. 1/2" brads are cheap... it doesn't matter if he bends a few of them!)
H. Cut the slice of wood off the top. Be careful to keep this cut perpendicular to the side of the block.
As always, cut on the "waste side" of your guide lines!
Here, for convenience, I sometimes deviate from my otherwise strict rule of "the Cub Scout builds the whole car"... I will do this cut on a table saw. It is a long, tedious job with a hand saw, and quite a bit to try to remove with a block plane.
The piece can be tacked to a larger piece for safer feeding through the saw. (I have the Cub Scout do that tacking job for me. 1/2" brads are cheap... it doesn't matter if he bends a few of them!)
J. Mark the openings, if any, to be cut for weights, etc., on the top or bottom of the car blank. For designs other than "RAIL", the size of some openings will depend on the amount of lead to be inserted, so this is a good time to gather the car body, wheels, axles and supply of lead weights together and weigh them, adjusting the amount of lead to bring the car up to nearly 5 ounces.
For the "RAIL" design, weighing happens after the center has been removed. Rules which require that the "original wheel base be retained" may allow some length to be removed from the rear and added to the front. In that case, see note C.
K. Lead weights may be shaped by pounding them with a "hammer and anvil", just like a blacksmith. To make contoured shapes, flatten an ounce of lead (about 1/32" thick) and shape it by hand. Cut off excess and use trimmings for fill.
L. Shape rounded surfaces with a knife, chisel, plane, or sandpaper.
Complicated wood shapes are difficult for most Cub age boys, so I like to stick with straight lines in the wood.
M. Round (chamfer) the edges, but be careful about affecting the area near the axle holes.
Sandpaper and elbow grease is usually the best bet here.
N. For Design 4 only: Cut two struts about 4" X 1/4" X 1/8". Carefully cut the side rails at about the center of the car. Lay the car out on waxed paper, glue the struts to the side rails so that the length of the car is now 7 inches. Clamp and allow the glue to set, being careful to maintain the axle hole alignment.
If the "cuts were clean", use equal length spacers to help assure that the same amount of length is being added to each side.
I like 5-Minute Epoxy for this because it correlates well with the Cub Scout attention span.
Latest update: 9/16/97
Technical Changes for HTML 3.2 Conformance 12/28/97
Copyright 1995, 1997 © by Stan Pope. All rights reserved.