L.B., of Wis.--We would be glad to assist you but the data you furnish are not sufficient. The accurate solution of such a problem involves the higher mathematics.
A.H.M.--All animal and mineral oils are destructive to rubber. Linseed oil will not dissolve it. Oils should not be allowed to get on rubber belting.
T.W.J., of Pa.--For your rollers try some emery mixed in a solution of gum shellac in good alcohol.
E.B., of Mass.--The patent can be corrected by reissue.
J.M.T., of Ind.--To find the proper area for a safety valve port, when the evaporating surface is properly proportioned to the engine power, multiply the square of the diameter of the piston in inches by the speed in feet of the piston per minute, and divide the product by 375 times the pressure on the boiler per square inch. Having decided upon the length of the lever, the distance of the valve stem from the fulcrum, and the point from which the weight will be suspended, the weight necessary will be found by multiplying the area of the valve port in inches into the pressure per square inch in the boiler in pounds, and this product into the distance of the center of the valve stem from the fulcrum in inches, and dividing the product thus obtained by the distance from the fulcrum to the point of suspension of the weight in inches. The quotient will give the weight in pounds.
A.K.S., of Ohio.--The inclination of the poles of a planet to the plane of its orbit, determines its zones and also its seasons. The inclination of the earth's axis is twenty-three and one half degrees. This places the tropics the same distance each side of the equator, and the polar circles the same distance from the poles. The torrid zone is therefore forty-seven degrees wide, and the temperate zones each forty-three degrees wide. As the planets vary in their inclination of their axis to the planes of their orbits, it follows that their zones and seasons differ from those of the earth.
W.H.C., of Texas.--The teeth of a circular wood saw to be driven by foot-power, should be not larger than those of the ordinary hand crosscut. The fly-wheel ought to have a rim weighing from eighty to one hundred pounds, and it should be, for a 12-inch saw, not less than a foot in diameter. It should be placed on the saw arbor. The belt should not run on the fly-wheel, but on a special pulley, and the treadle and crank motion should be so adjusted that the foot will move through an arc of from 10 to 12 inches.
A.H.B., of Pa.--We advise you to use a battery in coating the small gray castings, of which you write, with copper. It will be all the more satisfactory in the end. The best polishing material to put in with them in the tumbler we think would be leather cuttings and sweepings. They will not need returning to the tumbler after being coppered. We recommend you to get "Byrne's Practical Metalworkers Assistant," published by Henry Carey Baird, Philadelphia.
J.H.G., of Tenn.--Don't put oil in your boiler to prevent incrustation. It will not probably do any good, and it will cause much foaming, while besides that it is a waste of heat, it is injurious to engines.
S.S.R., of Tenn.--No ammoniacal engines are, so far as we are aware, running in this country.