The fly wheel driven by the foot, attached to the lathe as part of the machine, now offers abundance of power for all ordinary turning, and renders the workman generally independent of assistance. Although so slowly adopted by the turners, it was early employed in other handicrafts. In addition to the grindstone with crank and treadle turned by the foot of the workman, reproduced in the third volume of this work; the Gem engraver is also found in the trades collection of Schopper, and the same artist is drawn by Felibien. In both illustrations, they employ foot wheels the axes of which extend across the frames of their lathes; the treadles are jointed under the heel of the artist, and are set in motion by a small movement of the ankle joint, insufficient to disturb the quiescent position of the body, any movement in which would introduce a most serious difficulty in so minute and delicate an art. The same apparatus, of which the modern form will be found pages 1349- 1363, Vol. III., continues to be used without material alteration, except in the occasional introduction of an intermediate axis with a second pair of pulleys to increase the velocity.
The exclusive or even general use of the foot wheel for the lathe, was probably considerably retarded, first, by the very simple and economic nature of the pole lathe, and then, by imperfections in the construction and in the manner in which the employment of the wheel was first attempted. In its earlier application, the wheel was always accompanied by the spring bow or pole in the same lathe, fig. 21; and in working, the preference appears to have been generally given to the reciprocal instead of the continuous motion; doubtless from the inefficiency and the difficulty experienced in using the original foot wheels.
The foot wheel was at first made from a flat piece of wood, a cord passing from its cranked winch handle to the treadle; and the spring having been always placed above the lathe, the same position was selected for the wheel. An exception is found in Moxon, who places the fly wheel beneath the lathe, arranged somewhat after the modern manner; but Plunder recommends that the wheel should be placed, above, below, or at the side of the lathe, as may be found most convenient to the work and the dimensions of the workroom. The wheel in fig. 21, is fixed above, being mounted in an adjustable frame supported upon joists inserted in the wall; the frame was raised or lowered by a wooden screw, to place the driving band on or off the work or to accommodate its length. The inaccessible position of the wheel to the workman, to start or check its revolutions, constantly necessary in examining the progress of the work, and the elasticity of the long cord, were among other objections to this arrangement. The foot wheel fig. 32, is copied from that given by Plumier, to be used beneath the bearers; it was mounted upon distinct standards, that it might be removed whenever the work was set in motion by the spring bow. This wheel is described as of two pieces of wood of different diameters attached to each other, the larger, to obtain momentum, having a plain edge, the smaller with a groove for the band. The axis of the wheel was raised and lowered to adjust the length of the driving band, by wooden wedges passing through mortises in the two uprights ; and, when the wheel was used, the one foot of the frame was temporarily fixed to one foot of the lathe by pieces of wood, and metal pins. The back of the treadle was attached to the pin of the winch handle by a short leather loop, its opposite end having a metal eye to be placed on a hook fixed to the inner side of the lathe standard; the other half of the treadle was for the foot, and the two were loosely jointed together by a pin and nut.
The same author describes another and yet more temporary mode of attachment for the foot wheel, fig. 33, that of hanging it directly to the bearers. The axis of the wheel was fixed to a broad upright piece of wood, which was carried upon the face of a longer similar piece, fixed to the bearers by a transverse wedge, somewhat after the same manner as the popit heads. The adjustment for the length of the driving band was obtained by a tenon fixing in a long mortise by means of a wooden wedge.
The elasticity of the treadle cord, the small diameter and the slight weight of these driving wheels, and the friction of their bearings, all tended to impede their continuous revolution; improvement was sought by weighting the wheel with metal plates, while to obtain a smoother action the workman is directed, when possible, to make the length of the foot treadle some ten or twelve times that of the "elbow" or crank. The best results as to power that could be obtained however, must still have contrasted very unfavourably with the strong and simple action of the pole and bow. Subsequently the fly wheel, unaltered in form and material but increased in size, was attached to the upright of the lathe in the manner described and shown by Bergeron, fig. 34. A straight rod with a stud here replaces the curved crank, but the leathern thong, the flat edge to the wheel, and the screw adjustment were still retained.
Nevertheless, at the same period, the more elaborate portable lathes described by this author, 1816, were still provided with both the bow and the wheel, separately mounted. The wheel, of rather small size, together with an elaborate apparatus of screw adjustments to regulate the tension of the band, was placed above the level of the workman's head, upon the top of a slight pedestal erected on the backboard of the lathe. The pedestal being frequently elaborately ornamented as a column of one of the architectural orders. The wheel was thus within reach of the hand, but want of stability was now added to its other defects, Foot wheels made entirely of wood, although still occasionally met with, are insufficient to overcome the resistance in turning ordinary large work, even when they are weighted near the circumference to increase their momentum. The arms and center, or these and the rim of the wheel, were next cast as one piece in iron, and a wooden tire was attached, in which the grooves for the band were turned when the wheel was mounted in its place. The axis was also extended to a fixed intermediate standard, bent as a crank, and made to revolve upon fixed centers instead of running in bearings, greatly reducing the friction; while the elastic thong was exchanged for a rigid metal rod, formed into a hook to embrace the crank pin, with its lower end attached to the treadle. Ultimately, the axis was extended throughout the length of the frame, the entire wheel was cast in iron and the flat edge and screw adjustment were abandoned; the tension of the band being effected by the simple expedient of forming the edge of the wheel into three or four grooves of slightly decreasing diameter side by side, the band being tightened or slackened by shifting it from one groove to the next.
Moxon, page 179, gives such distinct directions as to the mode of using the foot wheel of his time, that it would be difficult to find clearer or more vigorous language in which to place it before the reader; he says:
"Of the Treddle Wheel."
"This is a Wheel made of a round Board about two Foot "and an half Diameter, conveniently to stand under the "Cheeks of the Lathe. It also has a Groove on its Edge for "the String to run in; it hath an Iron Axis with a Crook or "Crank at one end: And on the Crook is slipped the Noose of "a Leather Thong, which having its other end fastened to a "Treddle, does, by keeping exact time in Treads, carry it "swiftly about without intermission.
"But the length of the Thong must be so fitted, that when "the Wheel stands still, and the Crook at the end of the Axis "hangs downwards, the end of the Treddle to which the Thong "is fastened may hang about two or three inches off the "ground: For then, giving the Wheel a small turn with the "Hand, till the Crook rises to the highest, and passes a little "beyond it; if just then (I say) the Workman gives a quick "Tread upon the Treddle to bring the Crook down again with "a jerk, that Tread will set it in motion for several revolu-"tions; and then, if he observes to make his next Tread, just "when the Crook comes about again to the same position, it "will continue the motion, and cause of the motion, and keep "the Wheel always running the same way, if he punctually "makes his Treads."