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Discharge in cubic feet per second multiplied by 375 gallons per minute.

Discharge in cubic feet per second multiplied by 2400 tons per day of 24 hours.

miles per hour.

feet per minute.
yards per minute.

Velocity in feet per second multiplied by '68 Velocity in feet per second multiplied by 60 Velocity in feet per second multiplied by 20 Pressure of water in lbs. per square foot = head in feet multiplied by 62.32.

Head of water in feet = pressure of water in lbs. per square foot multiplied by 016.

Discharge of Sewers.-The discharge of sewage pipes is less than that of water pipes, the flow being retarded by the rough surface of the pipes caused by deposit. Mr. Blackwell's rules given above will apply to sewage pipes by using a constant of 2·8, instead of 2.3 used for water pipes.

Hydraulic Press. To find the pressure on the ram of the press in tons.-Rule: Multiply the area in square inches, of the press ram, by the length of the pump handle, from the fulcrum to the point the force is applied, in feet, and multiply the product by the force in lbs. applied to the handle, and call the result A. Next multiply the area in square inches, of the pump-plunger, by the distance in feet, between the fulcrum and the centre of the pump-plunger, and multiply the product by 2240, and call the result B.; then divide the result A. by the result B., and the quotient will be the pressure in tons on the ram.

Thickness of Metal for Hydraulic-Press Cylinders.-Cast-iron cylinders for hydraulic presses are generally made in thickness to onehalf the diameter of the ram for a working permanent strain of 2 tons per square inch. Barlow's Rule for the bursting pressure of thick cylinders is: -multiply the cohesive strength of the metal in tons per square inch by the thickness of metal in inches, and divide the result by the sum of the internal radius of the pipe, and the thickness of metal in inches. For the thickness of metal it is:-multiply the internal radius of the pipe in inches, by the internal bursting pressure in tons per square inch, and divide the product, by the quotient of the internal pressure, in tons per square inch of section, subtracted from the cohesive strength of the metal, in tons per square inch.

Example: A hydraulic-press cylinder of cast-iron 5 inches thick, with ram 10 inches diameter, cohesive strength of metal 7 tons, would 7 tons x 5 inches thickness of metal burst with = 5 inch radius + 5 inches thickness of metal 3 tons. The bursting pressure should have by the last rule, a thickness of 5 inch radius x 3'5 tons bursting pressure metal 3'5 tons-7 tons cohesive strength of metal for finding the cohesive strength required for a given pressure is—add the

= 5 inches.

The rule

internal radius in inches of the pipe to the thickness of the metal in inches; multiply the result by the internal pressure in tons per square inch, and divide the product by the thickness of metal.

Taking the above example, the cohesive strength would be.

5 in. rad. + 5 in. thickness of metal × 35 tons internal bursting pressure 5 inches thickness of metal

= 7 tons.

The Accumulator.-The accumulator is used for storing the pressure of water, for working hydraulic cranes and machines. It consists of a long cast-iron cylinder, fitted at the top with a stuffing box and gland, through which a solid ram works; at the bottom of the cylinder are two pipes, one of which is connected to a pump, and the other to a hydraulic machine. On the top of the ram a cross head is fixed, which supports an annular cylinder, loaded with scrap-iron. The pump forces water into the cylinder, which raises the ram, and so long as the ram is upheld, the pressure of the water in the cylinder, and pipes connected to it, will be determined by the area of the ram, and the load upon it.

To find the pressure in pounds per square inch on the water in an accumulator: Rule, add the weight in pounds of the ram to the weight in pounds of the cross head and weighted cylinder, and divide the sum by the area of the ram in square inches.

The usual working pressure of hydraulic cranes is 700 lbs. per square inch, and of other hydraulic machines from 1500 lbs. to 2000 lbs. per square inch.

Pipe Coverings.-The loss of heat and power by radiation of heat from steam pipes is considerable, but it may be reduced to a minimum by clothing the pipes with a good non-conducting material, such as hair felt, which-being light and fibrous-is a good confiner of air. Organic substances are good non-conductors, but they should be protected from charring by encasing the pipes with tin-plate, so as to form a inch air space round the pipe, the air in which makes an efficient insulator of heat.

Steam Saved by Non-Conducting Coverings for Steam Pipes, relatively to the bare pipes, Each composition being wrapped twice round with paper, with an outside cover of double wrapped canvas painted with two coats of paint. Total thickness of each covering 1 inches.

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SECTION III.

MILLWORK: SHAFTING, GEARING,

PULLEYS, ETC.

SECTION III.

MILLWORK: SHAFTING,

PULLEYS, ETC.

GEARING,

TOOTHED WHEEL GEARING.

Wheel-Gearing.-Where motion has to be transmitted with precision, toothed wheel gearing must be used. The teeth should be so formed that the wheels will work together with the smallest amount of friction, and work smoothly and uniformly with a constantly equal power and with comparatively little noise, in the same manner as if two plain cylinders were rolling upon each other by the friction of their own pitch circles. As a wheel acts as a lever of a length represented by its radius, the leverage is governed by the diameter; but in making calculations, the number of teeth

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is used instead of the diameter. As fine-pitch wheels have a smoother and more uniform action than coarse ones, the pitch should always be made as fine as possible, consistent with the power transmitted. In calculating gearing, the diameter of the pitch-circle is taken as the diameter of the wheel, and when the wheels are properly in gear their pitch-circles meet and roll upon each other.

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