228 CONSTRUCTION OF MACHINES. [Chap. 11.

turn the spout by. In crane spouts for meal, it is some-times best to let the lower board reach to, and rest onthe floor. If the elevator-cases and crane spout be wellfixed, there can neither grain nor meal escape, or bewasted, that enters the elevator, until it comes out at theend of the crane-spout again.

Of an Elevator to elevate Wheat from a Ship’s Hold*

Make the elevator complete (as it appears 35—*39,Plate VIII.) on the ground, and raise it to its place af-terwards. The pulleys are to be both fixed in theirplaces and cased; and the blocks that the gudgeon of thetipper pulley is to run in, are to be riveted fast to thecase-boards of the pulley, and these case-boards screwedto the strap-cases by long screws, reaching through thecase-boards edgeways. Both sides of the pulley-case arcfastened by one set of screws. On the outside of theseblocks, round the centre of the gudgeons, are circularknobs, 6 inches diameter, and 3 inches long, strongly ri-veted, to keep them from splitting off, because, by theseknobs the whole weight of the elevator is to hang. Inthe moveable frame 40, o o, o o, are these blocks withtheir knobs, which are let into the pieces of the frameBCrs. The gudgeons of the upper pulley p passthrough these knobs and play in them. Their use is tobear the weight of the elevator that hangs by them; thegudgeons, by this means, bear only the weight of thestrap and its load, as is the case with other elevators.Their being circular gives the elevator liberty to swingout from the wall to the hold of the ship.

The frame 40 is made as follows: the top piece A E is9 by 8 inches, strongly tenoned into the side pieces A Dand B C with double tenons, which side pieces are 8 by^6. The piece r s is put in with a tenon, 3 inches thick,which is dove-tailed, keyed, and draw-pinned, withan iron pin, so that it can easily be taken out. In eachside piece AD and B C there is a row of cogs, set in acircle, that are to play in circular rabbets in the posts

• See the description of this elevator in Art. 90.