After an acid dip to remove the scale on the sheet brass, followed by a dip in lacquer, to prevent further tarnish, the wheels are riveted on the pinions in a specially constructed jig which keeps them central during the riveting and when finished the truth of every wheel and its pinions and pivots are all tested before they are put into the clocks. The total waste on all processes in making wheels and pinions is from two to five per cent, so that it will readily be seen that accuracy is demanded by the inspectors. European writers have often found fault with nearly everything else about the Yankee clock, but they all unite in agreeing that the cutting and centering of wheels, pinions and pivots (and the depthing) are perfect, while the clocks of Germany, France, Switzerland and England (particularly France) leave much to be desired in this respect; and much of the reputation of the Yankee clock in Europe comes from the fact that it will run under conditions which would stop those of European make.
We give herewith a table of clock trains as usually manufactured, from which lost wheels and pinions may be easily identified by counting the teeth of wheels and pinions which remain in the movement and referring to the table. It will also assist in getting the lengths of missing pendulums by counting the trains and referring to the corresponding length of pendulums. Thus, with 84 teeth in the center wheel, 70 in the third, 30 in the escape and 7-leaf pinions, the clock is 120 beat and requires a pendulum 9.78 inches from the bottom of suspension to the center of the bob.
To Calculate Clock Trains.—Britten gives the following rule: Divide the number of pendulum vibrations per hour by twice the number of escape wheel teeth; the quotient will be the number of turns of escape wheel per hour. Multiply this quotient by the number of escape pinion teeth, and divide the product by the number of third wheel. This quotient will be the number of times the teeth of third wheel pinion must be contained in center wheel.
Clock Trains and Lengths of Pendulums.
| Wheels | Pinions | Escape wheel | Vibrations of Pendulum —Min. | Length of Pendulum in Inches |
|---|---|---|---|---|
| 120 90 75 | 10 10 9 | Double | *30 | 156.56 |
| 3 legged | ||||
| 120 90 90 | 10 9 9 | Do. | *40 | 88.07 |
| 128 120 | 16 | 30 | 60 | 39.14 |
| 112 105 | 14 | 30 | 60 | 39.14 |
| 96 90 | 12 | 30 | 60 | 39.14 |
| 80 75 | 10 | 30 | 60 | 39.14 |
| 64 60 | 8 | 30 | 60 | 39.14 |
| 68 64 | 8 | 30 | 68 | 30.49 |
| 70 64 | 8 | 30 | 70 | 28.75 |
| 72 64 | 8 | 30 | 72 | 27.17 |
| 75 60 | 8 | 32 | 75 | 25.05 |
| 72 65 | 8 | 32 | 78 | 23.15 |
| 75 64 | 8 | 32 | 80 | 22.01 |
| 84 64 | 8 | 30 | 84 | 19.97 |
| 86 64 | 8 | 30 | 86 | 19.06 |
| 88 64 | 8 | 30 | 88 | 18.19 |
| 84 78 | 7 | 20 | 89.1 | 17.72 |
| 80 72 | 8 | 30 | 90 | 17.39 |
| 84 78 | 7 | 21 | 93.6 | 16.08 |
| 94 64 | 8 | 30 | 94 | 15.94 |
| 84 78 | 8 | 28 | 95.5 | 15.45 |
| 108 100 | 12 & 10 | 32 | 96 | 15.28 |
| 84 84 | 9 & 8 | 30 | 98 | 14.66 |
| 84 78 | 7 | 22 | 98 | 14.66 |
| 84 78 | 8 | 29 | 98.9 | 14.41 |
| 80 80 | 8 | 30 | 100 | 14.09 |
| 85 72 | 8 | 32 | 102 | 13.54 |
| 84 78 | 8 | 30 | 102.4 | 13.44 |
| 84 78 | 7 | 23 | 102.5 | 13.4 |
| 105 100 | 10 | 30 | 105 | 12.78 |
| 84 78 | 8 | 31 | 105.8 | 12.59 |
| 84 78 | 7 | 24 | 107 | 12.3 |
| 96 72 | 8 | 30 | 108 | 12.08 |
| 84 78 | 8 | 32 | 109.2 | 11.82 |
| 88 80 | 8 | 30 | 110 | 11.64 |
| 84 77 | 7 | 25 | 110 | 11.64 |
| 84 78 | 7 | 25 | 111.4 | 11.35 |
| 84 80 | 8 | 32 | 112 | 11.22 |
| 84 78 | 8 | 33 | 112.6 | 11.11 |
| 96 76 | 8 | 30 | 114 | 10.82 |
| 115 100 | 10 | 30 | 115 | 10.65 |
| 84 78 | 7 | 26 | 115.9 | 10.49 |
| 96 80 | 8 | 30 | 120 | 9.78 |
| 84 70 | 7 | 30 | 120 | 9.78 |
| 84 78 | 7 | 27 | 120.3 | 9.73 |
| 90 84 | 8 | 31 | 122 | 9.46 |
| 84 78 | 7 | 28 | 124.8 | 9.02 |
| 100 80 | 8 | 30 | 125 | 9.01 |
| 90 84 | 8 | 32 | 126 | 8.87 |
| 100 96 | 10 | 40 | 128 | 8.59 |
| 84 78 | 7 | 29 | 129.3 | 8.42 |
| 100 78 | 8 | 32 | 130 | 8.34 |
| 84 77 | 7 | 30 | 132 | 8.08 |
| 84 78 | 7 | 30 | 133.7 | 7.9 |
| 90 90 | 8 | 32 | 135 | 7.73 |
| 84 78 | 7 | 31 | 138.2 | 7.38 |
| 84 80 | 8 | 40 | 140 | 7.18 |
| 120 71 | 8 | 32 | 142 | 6.99 |
| 84 78 | 7 | 32 | 142.6 | 6.93 |
| 100 87 | 8 | 32 | 145 | 6.69 |
| 84 78 | 7 | 33 | 147.1 | 6.5 |
| 100 96 | 8 | 30 | 150 | 6.26 |
| 84 78 | 7 | 34 | 151.6 | 6.1 |
| 96 95 | 8 | 32 | 152 | 6.09 |
| 84 77 | 7 | 35 | 154 | 5.94 |
| 104 96 | 8 | 30 | 156 | 5.78 |
| 84 78 | 7 | 35 | 156 | 5.78 |
| 120 96 | 9 & 8 | 30 | 160 | 5.5 |
| 84 78 | 7 | 36 | 160.5 | 5.47 |
| 84 78 | 7 | 37 | 164.9 | 5.15 |
| 132 100 | 9 & 8 | 27 | 165 | 5.17 |
| 84 78 | 7 | 38 | 169.4 | 4.88 |
| 128 102 | 8 | 25 | 170 | 4.87 |
| 84 78 | 7 | 39 | 173.8 | 4.65 |
| 36 36 35 | 6 | 25 | 175 | 4.6 |
| 84 77 | 7 | 40 | 176 | 4.55 |
| 84 78 | 7 | 40 | 178.3 | 4.43 |
| 45 36 36 | 6 | 20 | 180 | 4.35 |
| 47 36 36 | 6 | 20 | 188 | 3.99 |
*These are good examples of turret clock trains; the great wheel (120 teeth) makes in both instances a rotation in three hours. From this wheel the hands are to be driven. This may be done by means of a pinion of 40 gearing with the great wheel, or a pair of bevel wheels bearing the same proportion to each other (three to one) may be used, the larger one being fixed to the great wheel arbor. The arrangement would in each case depend upon the number and position of the dials. The double three-legged gravity escape wheel moves through 60° at each beat, and therefore to apply the rule given for calculating clock trains it must be treated as an escape wheel of three teeth.
Take a pendulum vibrating 5,400 times an hour, escape wheel of 30, pinions of 8, and third wheel of 72. Then 5,400 ÷ 60 = 90. And 90 × 8 ÷ 72 = 10. That is, the center wheel must have ten times as many teeth as the third wheel pinion, or ten times 8 = 80.
The center pinion and great wheel need not be considered in connection with the rest of the train, but only in relation to the fall of the weight, or turns of mainspring, as the case may be. Divide the fall of the weight (or twice the fall, if double cord and pulley are used) by the circumference of the barrel (taken at the center of the cord); the quotient will be the number of turns the barrel must make. Take this number as a divisor, and the number of turns made by the center wheel during the period from winding to winding as the dividend; the quotient will be the number of times the center pinion must be contained in the great wheel. Or if the numbers of the great wheel and center pinion and the fall of the weight are fixed, to find the circumference of the barrel, divide the number of turns of the center wheel by the proportion between the center pinion and the great wheel; take the quotient obtained as a divisor, and the fall of the weight as a dividend (or twice the fall if the pulley is used), and the quotient will be the circumference of the barrel. To take an ordinary regulator or 8-day clock as an example—192 (number of turns of center pinion in 8 days) ÷ 12 (proportion between center pinion and barrel wheel) = 16 (number of turns of barrel). Then if the fall of the cord = 40 inches, 40 × 2 ÷ 16 = 5, which would be circumference of barrel at the center of the cord.
If the numbers of the wheels are given, the vibrations per hour of the pendulum may be obtained by dividing the product of the wheel teeth multiplied together by the product of the pinions multiplied together, and dividing the quotient by twice the number of escape wheel teeth.
The numbers generally used by clock makers for clocks with less than half-second pendulum are center wheel 84, gearing with a pinion of 7; third wheel 78, gearing with a pinion of 7.