1GS 



HOROLOGY. 



Turret 

 Clocks. 



no adequate weight of hammer can be raised, and hence 

 , a sufficiency of sound cannot be obtained from the bell. 

 It has been said that the weight of the hammer for this 

 purpose should be 5 pounds weight forevery 1 00 pounds 

 in the bell. Turret clocks in general must either have 

 their bells too large for this proportion, or the clocks 

 have not been made to raise a heavy enough hammer. 

 The arm of the hammer when at rest, should hardly 

 make an angle of elevation above 20 degrees, or 24 at 

 most ; and in order to get as much mass of matter in 

 the hammer head, the tail by which it is raised should 

 be pretty long, and give a rise from the bell as little as 

 possible. But this distance of rise from the bell must de- 

 pend, among other things, on the length of the arm, 

 and on the angle or length raised by the pin wheel and 

 hammer tail. 



It was formerly proposed to fix on the fore bar the 

 mall dial, to which the minute hand is set at, when 

 setting those of the principal dials ; but it matters not 

 .whether a dial is fixed and the minute hand is move- 

 able, or the minute hand is fixed and the dial moveable. 

 Suppose that, by means of three small and short brass 

 pillars, fixed inside of the bevelled wheel, we now screw 

 on the tops of them a light round dial, having the mi- 

 nute divisions and figures on it, and the minute index 

 fixed to the fore bar, we can here make the bevelled 

 wheel be turned about, till the minute index points to 

 the proper minute. This mode will, besides, allow us 

 to have more conveniently three sets of dial work, that 

 is, two by the bevelled wheels, whose arbors are laid 

 horizontal, and the third by connecting it with the 

 socket of the first or front bevelled wheel. 



Where turret clocks are of a large size, and have very 

 heavy weights applied to the barrels, they require much 

 force and strength to wind them up. In order to re- 

 medy this, an apparatus of much the same nature as 

 that which is commonly applied to cranes has been 

 used. This consists of a wheel, with rather strong 

 and coarse teeth, fixed on the barrel end, opposite to 

 that where the great wheel is. A pinion of any num- 

 ber, on whose arbor is a square to receive the winding 

 up key, is attached to the clock frame, by means of a 

 cock, &c. so as to pitch with the wheel on the barrel 

 end ; and by this means, a considerable weight can be 

 raised with ease, requiring much less exertion, but 

 more time than when the winding up was performed 

 by the barrel arbor. The clock in the town-house of 

 Paris is wound up in this manner, which is represented 

 in the drawing of Vick's clock, Plate CCC. Fig. 1. 

 The size of the wheels and strength of teeth, may be 

 regulated according to the weight to be wound up. 

 The weight of the going part is in all cases light, when 

 compared with that which is necessary for the stri- 

 king part, in most of these clocks. Besides the advan. 

 tage of winding up a heavy weight with ease, this me- 

 thod has another, which is, that the barrel arbor pivots 

 can be used, either in conducting the hands, dischar- 

 ging the quarter and striking parts, or turning count 

 wheels, &c. The old way of the division of the hours 

 striking by the count wheels and locking plate, and 

 locking on the hoop wheel, does not yield in inge- 

 nuity to any thing which has been since introduced in 

 its place by modern clockmakers. The only greatohjec- 

 tion to the old way, was the trouble of making the clock 

 strike a round of eleven hours, when the striking of the 

 hour corresponding with the hands, took place from 

 any accidental discharge. It may not be out of its 

 place to observe here, that the application of the cord 

 or rope for the weight should be on that side of the bar- 



rel which lies next to the pinion into which the great Astronomi. 

 wheel acts, especially in turret clocks, as this relieves calClocks. 

 the barrel pivots of a great degree of friction, which '"""V" 111 ' 

 they would otherwise undergo were the course of the 

 rope and weight on the opposite side. 



CHAP. XIV. 



On the Method of fitting up Astronomical Clocks. 



ALTHOUGH the example of calculation which we hare 0" 

 given for the different parts of a turret clock, is appli- U P astro (> - 

 cable to any clock ; yet, in order to make the calculation " 

 more familiar and easy, we shall apply it to an astro- 

 nomical clock, intended to go 32 days without winding 

 up, performing the computation in the most rigid man- 

 ner, as these clocks ought to be made as perfect as pos- 

 sible in all their parts. 



From the inside bottom of the intended case to the 

 under side of the seat board, is supposed to be 4 feet 107 

 inches, the seat board one inch thick, and the distance 

 from the upper side of it to the centre of the dial 3.125 

 inches, or 3^- inches. From these, to obtain a proper 

 diameter for the barrel, which is to have sixteen turns 

 on it, we propose that the length taken up by the pul- 

 ley and weight shall not exceed 6 inches, and that the 

 weight shall be about lOlb. or perhaps even less. Four 

 feet 10.7 inches diminished by 6 inches, will be 4 feet 

 4.7 inches, and this doubled will be 8 feet 9-4 inches; 

 which divided by 16, the number of turns proposed for 

 the barrel, we shall have 1054 tenths of inches, which di- 

 vided by 16, will give 65.875 tenths for one turn round 

 the barrel. From this, to find the diameter of the barrel, 

 say as 355 is to 113, so is 65.875 to the diameter requi- 

 red, which will be found to be 2.0968 inches. The 

 diameter given here for the barrel must be lessened by 

 a diameter of the gut. The diameter of the gut, which 

 we had 24 years at a month clock, and which carried a 

 weight of 24lbs. was .045 of an inch ; it might have even 

 supported it much longer, but a different weight was af- 

 terwards hung on. It is very thick gut at .080 of an inch, 

 and .060 of an inch is about the diameter of common sized 

 gut, which we shall take for our estimate in the diame- 

 ter of the barrel; then 2.0968 inches minus .060 of an 

 inch, will give for the true diameter of the barrel 2.0368 

 inches. The diameter might be kept even a little lar- 

 ger than this, since the cutting of the screw upon the 

 barrel for the gut to ride in will lessen it a little. The 

 depth of the screw cannot be much more or less than 

 .020 of an inch, at which we shall take it; 2.0368 + .020 

 will then make the diameter of the barrel 2.0568 inches. 

 It is more than 4O years ago since we proposed that the 

 trade in general should adopt for all their work gages, 

 inches and the lowest subdivisions of an inch. Had 

 this been done, it would have made all the communica- 

 tions between the different branches of the art extremely 

 simple and easy ; and yet however simple this may ap. 

 pear, it has never been done. It must be observed, that 

 every branch, suchas movement- maker, enameller, glass- 

 maker, spring-maker, verge-maker, &c. have all their 

 own gages, no one of which corresponds with that of 

 his neighbour's, and all these gages have numbers ap- 

 plied to them. On what these numbers are founded, 

 it would puzzle very much both the makers and owners 

 of the gages to tell. 



To get the length of the barrel between the ends, let 

 us take the diameter of the gut at .080 of an inch, in or- 

 der to allow freedom between the turns on winding 

 3 



