There are two great faults in the model. First is the lack of an adequate bearing for the barrel to turn on. There is only one very short bearing a long way removed from the point of engagement between the pinion and internal gear, and no adequate support is given the barrel, with the result that it tends to deflect from the ideal or true position and to bind. This condition is aggravated by the fact that the ring gear was made by cutting its teeth on an angle to the axis around which it is to revolve, using only a saw of appropriate width. The teeth were then rounded-up to form by hand in a separate operation which by its very nature means that the teeth are not exactly alike. This lack of uniformity of the ring gear coupled with an entirely inadequate bearing for the barrel contributes to rather erratic transfer of power. These irregular teeth would not, of course, be a factor in factory-made watches where suitable machinery would be available for the work.
[Illustration: Figure 2.--PATENT DRAWING OF THE HOPKINS WATCH. The mainspring barrel _E_, of a very large diameter in proportion to the diameter of the watch, occupies nearly the full diameter of the movement. The spring itself, narrower and much longer than usual, is made in the patent model by riveting two ordinary springs together end to end. Over this barrel and attached to the stationary frame of the watch is placed a large thin ring A, cut on its inner diameter with 120 teeth. Near its edge the barrel E carries a stud _g_ on which runs a pinion of 10 in mesh with the ring gear _A_. On this pinion is a wheel of 80 driving a pinion of 6 on the escape-wheel arbor. The 15-tooth escape wheel locks on a spring detent and gives impulse to the balance in one direction only, being a conventional chronometer escapement. The intermediate wheel and pinion, balance wheel, and balance cock have been adapted from a Swiss bar movement of the time.]
The second fault is in the ratio between the time of one revolution and the number of revolutions necessary for a day's run. Three turns of the spring are, of course, required to run the watch for an hour, since the barrel and train revolve three times in that length of time. If we choose to have the watch run for 30 hours on a winding, and this leaves but a small safety factor, then we see that this will require 90 turns of the main spring, a manifest impossibility in view of the space available.[5]