The patent model of Jason R. Hopkins' revolving watch, now in the U. S.
National Museum,[4] was not the first in which the entire train
revolved but it was a very novel conception intended to reduce greatly
the number of parts usually associated with any watch. This may be seen
from figures 2 and 3, where everything shown inside the ring gear
revolves slowly as the main spring runs down. This spring is prevented
from running down at its own speed by the train pinion seen in mesh with
the ring gear. Through this pinion motion is imparted to the escape wheel
and balance, where the rate of the watch is controlled. The balance,
being planted at the center of revolution, travels around its own axis,
as in the tourbillon, at the speed with which the entire train revolves
around the barrel arbor. This arbor turns only during winding. No dial or
dial gearing is shown in the patent or exists in the patent model. The
patent merely says, casually, "By means of dial wheels the motion of the
barrel may be communicated to hands and the time indicated in the usual
manner." No fine finish or jeweling has been lavished on the model, the
only jewels present being in the balance cock which was utilized as it
came from its original watch with only minor modification to the shape of
its foot. Apparently the balance wheel itself is also a relic of the same
or a similar conventional watch. There is no jeweling in the escapement
or on the other end of the balance staff. In spite of this the model runs
very actively and will overbank if wound up very far. The beat of the
escapement is two per second and the movement revolves once in 20
minutes.
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]
[Illustration: Figure 3.--ORIGINAL PATENT MODEL OF THE HOPKINS WATCH,
U. S. Patent 161513, July 20, 1875, now in the U. S. National Museum
(_cat. no._ 309025).]
[Illustration: Figure 4.--DRAWING FROM U. S. PATENT 165831, showing
Hopkins' first design improvement, an arbor for the barrel and train to
turn on and the balance displaced from center.]
Probably no attempt was made to produce a finished and practical watch at
this time, although Hopkins, the inventor, was an actual watchmaker as
well as a retail jeweler, with premises virtually in the shadow of the
Patent Office. He was a native of Maine[6] and had been established in
Washington since 1863, or perhaps some time in 1862.[7]
[Illustration: Figure 5.--HOPKINS' BALANCE ARRESTING DEVICE, the subject
of U. S. patent 165830. This and the device illustrated in figure 4
originally were submitted together to the Patent Office on June 9, 1875,
and later were divided into two patents.]
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[4] Cat. no. 309025; U. S. patent 161513, July 20, 1875.
[5] Those who have seen the Waterbury watch, which developed
from this design, may be drawn to the conclusion that
this explains why it took so long to wind the Waterbury.
Such is not really the case; in the Waterbury the
winding wheel (which is on the outer rim of the barrel)
was nearly as large as the inside diameter of the case
while the pinion engaging with it was of only nominal
diameter. This meant that one turn of the winding crown
wound the barrel a much smaller fraction of a revolution
than in a watch of conventional design.
[6] District of Columbia death record 145,013.
[7] Hopkins is not in the _Washington and Georgetown
directory_ of 1860 or 1862, and 1861 was not available
to check. Starting with 1863 he is listed each year
through 1871. Starting with 1872 Boyd's _Directory of
the District of Columbia_ lists Hopkins as a resident
each year (including 1902, the year of his death at 84
years) except 1877, when he was out of the city in
connection with the exploitation of his rotary watch
patents. Carl W. Drepperd, _American clocks and
clockmakers_ (Garden City, N.Y., 1947), in referring to
Hopkins, says, "Lincoln, Me. 1840's-1850's: Bangor, Me.,
to 1862. Inventor of the Auburndale Watch. Also
manufactured pianos and clock cases."