Page:Popular Science Monthly Volume 91.djvu/576

 Lifting a Car to Stop It

A brake which raises the rear wheels clear off the ground. Of course the car has to stop

���Two flat semi-circular steel shoes placed between the body of the car and the inside of the rear wheel on each side, are pushed down by a lever in such a manner as to lift the rear wheels

��AN unusual type of automobile emer- /"\ gericy -brake stops the car by lifting the rear or power wheels clear off the ground. It consists of two flat semi-circular steel shoes thick at the top and tapering off at the bottom. These are placed be- tween the body of the car and the inside of the rear wheel on each side.

A toothed rack is cut along each edge of the upper side of the shoe, the rack- teeth respectively meshing with the teeth of two ordinary spur-gears slipped loosely over the rear-axle housing and provided with cam-shaped clutches on their facing sides. A collar with reverse cam-shaped clutches is rigidly attached to the axle between each of the two spur gears. Two rollers carried on studs attached to the vehicle frame are employed to contact with the under or bottom side of each steel shoe and keep the racks on its upper face always in mesh with the two loose spur gears.

Either one of the spur gears may be rigidly attached to the turning rear axle by sliding it into contact with the clutch collar. The rotation of the collar revolves the gear in contact with it so that it causes the shoe to be moved down into contact with the ground and lift the rear wheel clear off the road. The friction between the shoe and the ground causes the vehicle to come to a gradual stop without the shock incident to the operation of the

��conventional band brake. When the shoe has been lowered the specified distance, further downward motion is prevented by the teeth of the gear running off those on the rack, the thicker section at the top of the shoe serving as a wedge to hold it in that position.

The lowering of the car-wheels on the ground after a stop, is accomplished by unclutching the first gear from the axle collar and clutching the other one. The same direction of rotation of the axle is made to lift the shoe up off the ground by means of a small gear interposed between the gear in clutch and the rack teeth.

The clutching of either gear with the collar between is secured by means of a longitudinal lever with a double-acting bell crank and pedal on the floorboard of the driver's cab.

Two pedals and two levers are employed, one for each set of loose gears. One pedal is made to suffice for the similar-sized gears on each side of the car by means of a crosswise equalizer at the rear as shown. This assures simultaneous action by each shoe.

Obviously the automobile will come to a comparatively short stop upon the appli- cation of the brake and will not be likely to skid or slide even on a steep grade as long as the steel shoes remain on the ground in their braking position.

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