CONSTRUCTION OP MACHINES.

229

Chap. 11.]

p. 41. These circles are to be described with a radius,whose length is from the centre of the joint gudgeons G fto the centre of the pulley 39; and the posts must be setup, so that the centre of the circle will be the centre of, the gudgeon G; then the gears will be always right, al-though the elevator rises and falls to suit the ship or tide.The top of those circular rabbets ought to be so fixed,that the lower end of the elevator may hang near thewall. This may be regulated by fixing the centre of thegudgeon G. The length of these rabbets is regulated bythe distance the vessel is to rise and fall, to allow the ele-vator to swing clear of the vessel when light, at high wa-ter. The best way to make the circular rabbets is, todress two pieces of 2 inch plank for each rabbet, of theright circle, and to pin them to the posts, at such a dis-tance, leaving the rabbet between them.

When the gate and elevator are completed, and triedtogether, the gate hung in its rabbets, and played up anddown, then the elevator may be raised by the same powerthat is to raise and lower it, as described, Art. 94.

ARTICLE 96.

OP THE MEAL ELEVATOR.

Little need be said of the manner of constructing themeal elevator, after what has been said in Art. 90, ex-cept giving the dimensions. Make the pulleys 3A inchesthick, and 18 inches diameter. Give them no more than20 revolutions in a minute. Make the strap 3^ incheswide, of good, pliant, white harness leather; make buck-ets either of wood or sheet-iron, to hold about half a pinteach; put one for every foot of the strap; make the casestight, especially round the upper pulley, slanting muchat bottom, so that the meal which falls out of the buckets,may be guided into tbe descending case. Let it lean alittle, that it may discharge the better. The spout thatconveys the meal from the elevator to the hopper-boy,should not have much more than 45 degrees descent,