To find area of a circle, multiply square of diameter by .7854; or multiply radius (one-half diameter) by circumference, and divide product by 2 (see Table XXT) To find the surface of a ball, multiply square of diameter by 3.1416.
To find side of a square approximately equal in area to a given circle, multiply diameter by .8862.
To find cubic inches in a ball, multiply cube of diameter by .5236.
Doubling the diameter of a pipe increases its capacity four times.
Double riveting is from 16 to 20 per cent stronger than single.
A concrete block 8x8x16 in. is the equivalent of 14 brick. See also page 300.
One ton of coal is equivalent to two cords of wood for steam purposes.
There are nine square feet of heating sur face to each square foot of grate surface.
A cubic foot of water weighs lbs.
Each nominal horse-power of a boiler re quires 30 to 35 lbs. of water per hour.
To sharpen dull files, lay them in diluted sul phuric acid until they are eaten deep enough.
A horse-power is equivalent to raising 33,000 lbs. one ft. per minute, or 550 lbs. one ft. per second.
The average consumption of coal for steam boilers is 12 lbs. per hour for each sq. ft. of grate surface.
To find the pressure in pounds per square inch of a column of water, multiply the height of the column in feet by .434.
Steam rising from water at its boiling point (212 degrees) has a pressure equal to the atmos phere (14.7 lbs. to the square inch).
One-sixth of tensile strength of plate, multi plied by thickness of plate and divided by one half the diameter of boiler, gives safe working pressure for tubular boilers. For marine boil ers add 20 per cent for drilled holes.
No plate or bars of either steel or iron should be worked at a black or blue heat (say about 500°) ; the material will stand far more strain either red hot or cold, while at an intermediate point great risks will be run, and possibly strains produced which result in rupture later on.
One thousand shingles, laid four inches to the weather, will cover one hundred square feet of surface, and five lbs. of shingle nails will fasten
them on.
One-fifth more siding and flooring is needed than the number of square feet of surface to be covered, because of the lap in siding and flooring.
One thousand laths will cover seventy yards of surface, and eleven pounds of lath nails will nail them on.
Eight bushels of good lime, sixteen bushels of sand, and one bushel of hair will make enough good mortar to plaster 100 square yards.
One cord of stone, three bushels of lime, and a cubic yard of sand will lay one hundred cubic feet of wall.
Cement one bushel, and sand two bushels, will cover square yards, one inch thick; 41/2 square yards inch thick; or square yards inch thick.
One bushel of cement and one bushel of sand will cover square yards one inch thick; 3 square yards inch thick; or square yards inch thick.
One bushel of anthracite coal weighs from 75 to 80 lbs. One bushel of bituminous coal weighs from 70 to 75 lbs. One bushel of coke weighs 32 lbs. A pound of anthracite coal con tains 14,500 heat units.
To find approximately the amount of paint required to cover a given surface, divide the number of square feet of surface by 200. The result will be the number of gallons of liquid paint required to give two coats. Or divide by 18, and the result will be the number of pounds of pure ground white lead required to give three coats.
Weight of Materials. The approximate weight per cubic foot of materials commonly used in construction is as follows: Bronze 552 Copper 550 Iron, cast 450 Iron, wrought 480 Lead 712 Steel, structural 490 Cedar 23 Chestnut 41 Cypress 29 Fir 32 Hemlock 25 Oak, white 50 Pine, white 24 Pine, yellow 35 Spruce 25 Asphalt 130 Blue stone 160 Brick in lime 120 Brick in cement 130 Cement, Portland 90 Concrete 150 Gneiss 160 Granite 165 Gravel 120 Limestone 170 Marble 165 Sandstone 145 Slate 170 Terra-Cotta 110 Tile 115 Weight of a bag of natural cement, about 94 lbs.
Weight of a bag of Portland cement, 94 Bag A bbl. of natural cement=3 bags, and weighs about 282 lbs.