Nov. 1, 1885.] 



KNOWLEDGE 



25 



long. Near one end cut a half-inch square hole, one 

 end of the spindle being reduced to fit it, a pin being 

 passed through the spindle to prevent the handle 

 working oif. The other end of the strip of wood should 

 also be furnished with a half-inch hole to carry the 

 handle proper, which should be well fitted, the portion 

 passing through the strip being at least an inch long, so 

 that a piu or nail may be inserted to prevent the handle 

 falling out. The disadvantage of this arrangement is 

 (hat the handle itself does not rotate as it revolves, or, in 

 other words, the hand has to slip over it in driving. 

 A much better plan, therefore, is to make a metal 

 handle. This may be done by procuring first a piece 

 of quarter-inch sheet-iron five inches long, an inch wide 

 at one end, tapering down to about five-eighths at the 

 other end. In the wide end drill a hole, and then file 

 out a square hole to fit a corresponding square end pro- 

 duced on the spindle. Nest take a piece of quarter-inch 

 iron rod, about five and a half inches long. Produce 

 shoulders by filing a little of the metal away from each end 

 for a distance of tive-eighths or three-quarters of an inch at 

 one end (A), and an eighth to three-sixteenths of an inch at 



the other end (B). Put a metal washer over the end A, 

 the hole in it being onlj- large enoiigh to allow it to pass 

 over the reduced portion of the iron rod. Then drill and 

 file a hole iu the narrow end of the strip of sheet-iron, to 

 fit on to the end B of the iron rod. Next place a washer 

 to the protruding portion of B (so that there is a washer 

 on each side of the hole in thestriji), then with a hr.mmer 

 well rivet the rod and external washer together, so r^s to 

 grip the strip tightly. A wooden handle with a hole 

 bored through it from end to end (such as a small 

 skipping-rope handle) is next provided, the hole being a 

 trifle larger than the iron rod over which it is to be 

 passsd, and a washer similar to those previously referred 

 to rivetted on to the end of the rod. The wooden handle 

 may then be grasped in the hand when working the 

 machine, as it will pass easily over its iron axis, and .so 

 save any risk of injuring the hand, or unduly straining 

 the apparatus. 



Let us next turn to the base. The cylinder measures 

 seven inches in length ; the projections A B are each 

 about an inch long ; half-an-ineh clearance must be left 

 between A and B and the respective supports. Allow- 

 ing, also, three-quarters of an inch for each upright, 



the total length of the base must be eleven and 

 a-half inches. The breadth should, for reasons pre- 

 sently apparent, be about the same. The thickness of 

 the material should be not less than three- quai'ters of an 

 inch. The supports should be secured to the base as 

 rigidly as possible. The best plan is to dovetail them. 

 They should be cut from sound stuff three-quarters of an 

 inch thick, and should be thi-ee inches wide at the bottom, 

 tapering upwards to two inches or thereabouts — the total 

 length being eight inches or more, and the shape similar 

 to that shown in Fig. 3. With a tenon-saw and keen 

 chisel, the lower portion should be shaped as at D D. 

 Holes should be bored with a centre-bit at C, six inches 

 from E, the diameter being about an eighth of an inch 

 greater than the diameter of the spindle carrying the 

 cylinder. In one of the holes a piece of brass tubing 

 should be inserted, the internal diameter being such as to 

 allow the spindle to revolve easily, but not loosely. The 

 hole in the wood, it is apparent, must be of such a 

 diameter as to cause the tube to fit as nearly as 

 possible to prevent it slipping out. Should there be 

 a tendency to so slip, the tube can be kept in 

 position bj- indenting each end into the wood, after 

 it has been placed in position. The other upright, 

 after having been bored, should bo sawn across, the saw- 

 cut passing through the centre of the hole, as shown 

 by the dotted line, A B. A piece of brass tubing, similar 

 to the one already used, should then be sawn in two, 

 longitudinally, and one of the parts placed iu each half 

 of the hole divided by the saw. A single small screw 

 will be sufficient to keep the half-cylinders of brass in 

 position, care being taken, however, to well countersink 

 the screw-hole, and to file off any burr or asperity of any 

 kind that may be left, which, if not removed, would 

 ultimately tend to destroy the spindle. The brasses 

 having been fitted, the upper portion of the support is 

 ready for receiving the spindle and then being screwed 

 down, as at S S, to the main portion. The ends of the 

 base should next be cut, so that the upright supports may 

 fit as closely as jiossible. If there is the slightest ten- 

 dency to loo.seness, means should be taken to overcome or 

 prevent it. The readiest plan is to screw the uprights 

 to the base at F F. The cj'linder may now be threaded 

 on the spindle, placed iu position, and balanced. It is 

 likely that the spindle will not tit both the apertures 

 tightly. If so, the intervening space may be fitted 

 with thin wedges of wood, or even cork, care being 

 taken that the cylinder revolves truly and is not given to 

 wobbling. Any orifices remaining should be filled up. 

 This may be done with sealing-wax, or with plaster of 

 Paris coated with a film of sealing-wax or varnish. 

 It is better to fill up in this way than to force 

 in unduly a number of wedges, there being in the 

 latter case a considerable risk of fracturing the 

 cylinder. Should it transpire that the adhesion of 

 the cement is insufficient to overcome the tendency of 

 the spindle to run roimd without the cylinder, notches 

 may be filed across the ends of the projections (A B, Fig. 2) 

 ancl filled with the cement. This will be quite sufficient 

 for such a machine as the one under consideration. The 

 end faces of the cylineler should be coated with ceiling- 

 wax varnish for insulating purposes, that is to |jrevent 

 the electricity escaping from the surface of the cylinder 

 to earth by wa\- of the handle. The varnish may be made 

 b}- dissolving 'jood sealing-wax in methj-lateel S]iirits, or 

 shellac varnish may be made in a similar way, and a red 

 colour imparted by the addition of a small quantity of 

 vermilion. The rubber, or that portion which j reduces 

 the friction with the glass, is easily made. Procure 



