Train
The train of a watch or clock is the wheels and pinions through which the motive power is transmitted to the escapement. The names of the various parts in a going barrel are the barrel, which takes the place of the first or great wheel, the second wheel, which has been given the name of center wheel because it occupies a central position in the plate of the movement. Following the center wheel is the third, fourth and fifth wheels respectively, the latter one being known as the escape wheel. The pinions are known by the same name as the respective wheels which are mounted upon them. It is desirable to have the size of the train as large as possible, preserving a systematical proportion between the first and last of the train, that is one wheel should be no larger than the one immediately preceding it, the general rule being to have each succeeding wheel smaller. The center wheel makes a revolution in one hour, and it is from this that the number of vibrations are reckoned. The number of vibrations per hour may be found by multiplying together the number of teeth in the center, third and fourth wheels and multiplying this product by twice the number of teeth in the escape wheel and dividing this last product by the product of the number of leaves in the third, fourth and escape pinions. In watches showing seconds the proportion between the center and fourth wheels must be as one to sixty, because it is this pinion that carries the seconds hand. This formula for determining the vibrations applies equally well to any of the escapements, whether watch or clock. The mainspring should develop enough turns to run the timepiece at least thirty hours. The train of a watch may be tested by sharpening a piece of pegwood and with it pressing on the end of the pinion pivot into which the wheel depths, when its condition may be judged. All other things being equal, the train having the largest wheels and pinions with the greatest number of teeth and leaves, will transmit the motive power most uniformly and with the least friction. In the finest trains, the wheels should be poised, or at least very near it, this item being the more important as we approach the escapement.