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Mr. DENISON ON TURRET-CLOCK REMONTOIRS. 



but without success, from evident defects in its construction, the clock sometimes failing to wind 

 it up, which of course need no more happen with a spring than a gravity remontoir. It seems 

 also to have been applied to a peculiar kind of escapement ; which was trying two experiments 

 at once, — always an unscientific proceeding. 



The obvious mode of applying a spring remontoir is to make the pinion of the escape-wheel 

 ride upon the axis instead of being fixed to it, and to connect the pinion and the wheel by a 

 spiral spring. Then if the pinion is turned (say) a quarter round by the train at intervals, 

 the wheel will be driven through a quarter of a revolution by the force of the spring only. 

 This is the plan I find described for the French spring remontoir, and a similar one has been 

 proposed by Mr. Airy, only to be wound up at every beat by means of a double escape-wheel and 

 pallets, and the principle of it was applied to a chronometer many years ago. But if nothing 

 more than this is done, the escape-wheel axis will have to turn within the pinion, as in a socket 

 with considerable pressure and friction upon it, which will probably be worse than the ordinary 

 friction of the train. The method I propose therefore is, to make the pinion (a brass lantern- 

 pinion, having the inner end of the spiral spring attached to it) ride upon a steel pin fixed to 

 the frame in the same line as the axis of the escape-wheel, and having in its end (or rather 

 in a piece of brass screwed on to its end) the pivot hole for the escape-wheel axis. The outer 

 end of the spring is to take hold of what I believe is called a dog (the shape of which will be 

 best described by the drawing), which screws on to the escape-wheel axis (the screw also acting 

 as a connterpoise), so that the tension of the spring can be adjusted to make the pendulum swing 

 as far as is required. It is evident that the wheel will thus be driven by the spring without 

 any friction. 



The mode of letting off the train at intervals, adopted in the 

 Exchange Clock and the above-mentioned Clock by Reid, is by fixing 

 two or more sets of long teeth on spikes in two or more planes on the 

 broad rim of a wheel on the same axis as the wheel which drives the 

 escape-wheel pinion ; and notches are cut nearly half through the escape- 

 wheel axis over each set of spikes, which will let a spike pass through 

 whenever the corresponding notch is in its lowest position ; and the 

 driving wheel is then stopped by one of the other set of spikes coming 

 against the axis in a place where the corresponding notch is not yet in a 

 position to let that spike pass. The objection to this is, that the spikes 

 strike the axis with considerable force, and also press on it pretty heavily 

 when at rest, which causes additional friction and requires a stronger 

 maintaining power than would otherwise be necessary. The blow against 

 the axis it is already proposed to diminish by a fly, to restrain the 

 velocity of the train when it is let off; and a fly is now used in the 

 French remontoirs ; where however it is much less needed, for they are 

 let off by pins raising a lever just like a common striking part ; and it 

 does not signify how hard the lever is struck. But this plan also is 

 objectionable because of the friction and loss of power in the escape- 

 wheel in raising such a lever, which is much more than would be due 

 to the pressure of the same lever, if only exerting a dead pressure on the 

 axis until it slips through a notch. 



I propose to use a fly, but more for the sake of diminishing the pres- 

 sure on the escape-wheel axis than of diminishing the velocity of the 

 train ; which is immaterial, except so far as it effects the escape-wheel. 

 The two letting-off pins are to be one at each end of the fly ; and if the 



radius of the fly is equal to the diameter of the driving wheel, and the r j • ^ r^ ,■ j 



•' ^ o ' End viev) of Cyltnder. 



