# Page:Popular Science Monthly Volume 89.djvu/319

Popular Science Monthly

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��Determining Brake Horsepower

THE brake liur^rpowcr ol an ciigiiu.' or motor is often determined i)y means of a friction or proncy brake. Make two wooden iiiocks A and B to fit the face of (he iniiley on the machine to l)e tested. The pieces C and D are fastened to the two iilocks and the whole clamped together by means of the two bolts E and F with the nuts G and // to tighten or loosen the whole. The end of the arm D has an iron eye in it to hook to the spring balance J which is hung from some suital)le sup|)ort. When the pulley is revolving in the direction indi- cated at its best sfieed the nuts G and H are gradually tightened imtil the friction is increased on the pulley and the arm pulls downward with considerable force. This tendency to turn will be indicated upon the spring balance.

The net pull at the balance is obtained by subtracting the net stationary weight of the arm from the indicated weight at the balance when the test is made. This distance is represented as N. The correct speed of the pulley or revolutions per minute must also be known. After all this data h;is been obtained the brake horsepower of the machine can" be calculated by the following formula:

��Brake Horsepower;

��X W RPM

��33,000

— .3.1416

N . Length of arm in leet.

W . Net pull, in pounds, at the spring balance.

RPM. Pulley speed.

This method, simple as it is, will be found of great service in determining, accurately, the brake horsei)ower of a motor or engine. — B. F. Uashiell.

The brake horsepower of a motor can be accurately meas- /y^'\^)i\ ured by means of a simple appar- j (^ p -^ atus such as the one here shown

���Preventing Carriage Bolts from Turning

C.\RRIAGK bolts are generally used in fastening sheet-metal parts such as dust-aprons, mud-guards, etc., to automobile running-boards. While these

/AJuminum Co>-e'rnq

���Wotxf Seen- L^-i

An ordinary wood-screw will prevent bolts from loosening and turning

ha\"c a square shank to pre\ent them from turning in the wood, if the running- board is of soft material the bolts are liable to cut away the wood surrounding the .square shank and make it ditticult to either remove or apply the nut. This is not a serious matter if the bolt head is exposed so it can be held by wedging, or if it has been provided with a screw- driver slot before assembling. When the running-board is covered with lin- oleum, which is nearly always shellacked in place, or aluminum matting, which is held by small screws and binding-strips, it is difficult to get at the bolt head. The usual installation, shown at A, can be improved materially by following the scheme shown at B. This can al.so be used if the bolt has been installed and the square shank has turned. A i/8-in. or 5 32-in. drill hole is made in the bolt head and a suital^le wood-screw inserted and firmly set into the wood, as at B. This is insurance against the head turn- ing and prevents an upward movement of the bolt when an attempt is made to screw on the nut. — Victor W. Page.

��W

��A Celluloid Flashlight

HKX a ruby light is not availa- ble for developing photographic prints an ordinary flashlight will serve the purpose. Remo\'e the lens and fit a disk of red celluloid in its place. Turn on the light and the celluloid will redden it, protecting the negatives from direct light.— C. Id. Miixi-k.

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