TO CALCULATE THE THICKNESS OF METAL FOR CYLIN DERS FOR HYDRAULIC PRESSES.

RULE:-Multiply the constant number given below for the material of which the cylinder is to be made by the pressure in tons per square inch, and by half the internal diameter of the cylinder.

EXAMPLE:-A 10-inch cylinder is to bear a pressure of 3 tons per square inch; what must be its thickness in cast iron ?

EXAMPLE:-A steel cylinder of 5 inches internal diameter is to bear a pressure of 35 tons per square inch; what must be its thickness? 0.6 × 35=2·10 × 2·5 = (Ans.) 5.25, or 51⁄2 inches.

TO CALCULATE THE WEIGHT OF RIMS FOR FLY WHEELS.

F Constant force in pounds, or mean force on

S

piston;

Stroke in feet;

W = Weight in pounds of fly wheel;

x=Radius of center of gyration in feet;
n=No. of revolutions per minute;
f=·05.

Multiply the area of the cylinder by the mean pressure on the piston in lbs. per square inch, by the stroke in feet, and by 500, and divide by the product of the number of revolutions per minute, multiplied by the radius of the fly wheel, measured at the inside of the rim.

Metal to heat and cool without loss of size or alteration of shape, must contain 9 parts of copper and 1 of aluminium.

ESTIMATING WEIGHT OF CASTINGS FROM THE WEIGHT OF THE PATTERN.

In presenting a table wherefrom to estimate the weight of a casting from the weight of the pattern, it must be understood that the calculation is only approximate; and in all cases in which there are core prints or battens to sustain the pattern, or other extraneous parts which exist upon the pattern and not upon the casting, the weight

of these parts must be estimated, or calculated, and deducted from the weight of the pattern.

TABLE

Of the Weight of Copper Bolts, from to 21 in. Diameter, and Ï1⁄2 inches long.

Of the Weight of a Lineal Foot of Cast Iron Pipes, in lbs., from 1 inch to

*NOTE:-These weights do not include any allowance for spigot and

faucet ends.

The above table is found to be of great use in making out correct estimates of cast iron pipes. For instance, suppose it is required to know the weight of a range of pipes, 324 feet long, 8 inches diam