Page:Popular Science Monthly Volume 88.djvu/309

 Popular Science Monthly

��The weight of the car will determine the size wire to be used in the coil springs; 3/16" for the front springs and 34" for the rear ones is about right for a car in the 2,000 pound class. This is figured for a touring car where five pas- sengers are to be carried. In the case of the roadster the rear springs could be of one size smaller wire. In the case of cars materially heavier the size of the wire should be increased. In order that the springs may carry the load properly they must be made 1" longer than the place they are expected to fill. This means that when they are assembled in the finished shock absorber, they are already under compression. According- ly those for the front absorbers should be 6" and those for the rear springs 7" long. The inside diameter of the springs should be not less than 1^4" in any case.

Those fortunate enough to have ac- cess to a machine shop can wind their own springs if desired, although there will be no great saving as the springs will be made up as ordered by any good spring manufacturer for about twenty- five cents each.

When placing the absorbers on the car they should first have their springs com- pressed and tied down with wire in order that they will not interfere with placing the bolts through. To compress them, use a cabinet clamp or vise.

The entire cost of the absorbers de- scribed was just $3.34 outside of the work.

Key Controls Battery Current

WHERE batteries are placed on bicycles or motorcycles for light- ing purposes, it is a great temptation to mischievous boys to turn the current on, a circumstance which, of course, means a loss of money to the owner of the vehicle. Such happenings can be averted if a lock switch is employed for con- trolling the battery current.

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The batteries should be placed in a metal cylinder, the ends of which are plugged with wooden discs. On one of these discs a small drawer lock is fasten- ed. At one side of the lock — the side from which the bolt emerges when the key is turned — a brass or phosphor- bronze contact spring should be fas- tened.. When the key is turned, the bolt pushes this spring against a brass con- tact, and current flows from the bat- teries to the lamps.

Eliminates Pants' Guards for Bicycle Riders

ACHAT N guard can be made for bicycles which will dispense with the need of pants guards.

A circular piece of stiff metal, having a diameter i'' greater than that of the

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��When the key is withdrawn, the auto-thief or mischievous boy is foiled

��A circular piece of metal protects the trousers from the sprocket gear

large sprocket, should be cut and crimped along the edge. Clamps should be fashioned from heavy steel or iron for the purpose of grasping the spokes of the sprocket. The clamps should be soldered to one face of the protecting disc and holes bored through the two. Machine screws pass throug'. the holes, terminating in tapped holes in similar clamps on the opposite side.

A Try- Square Aid

WHEN using a try-square to deter- mine if stock is true, one cannot remember all the high and low spots. If the edge of the try-square is dipped in lamp black before using, and is then run on the piece, all the high spots will be black while the low places will remain untouched.

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