HOROLOGY. 



165 



Tumt 10. If we take the ratio of the pin wheel of (>i to its 

 Outs* diameter 9.9 inches, then the tumbler wheel of K) would 

 ~~f~~ have its diamett i - lies, the teeth would then be 



of the same si*e or strength with those of the pin wheel ; 

 but this is not requisite, as they will bear to be consi- 

 derably diminished in size, anil if the diameter of the 

 tumbler wheel is nearly :..', inches, the teeth will be 

 sufficiently strong. In this striking part there is no fly 

 wheel and pinion. 



The locking of the striking part of turret clocks re- 

 quires safe and good mechanism. That which limd- 

 ley used is very ingenious, and was adopted in the 

 clock made fur St Andrew's Church in Edinburgh ; 

 yet, from foulness of oil or dirt, it is liable to misgive, 

 and in attempting to rectify ic, the ignorance or care 

 l*ami* of workmen i* apt to increase the evil. The 

 nicety of this locking lies in the pins of the count- 

 wheel, whose office is to raise up the locking-lifter, and 

 pass it at the same time. The locking which is here 

 proposed, is by means of two pins or detent* on the 

 t! y pinion arbor, one of which is for locking on, and 

 the other iaa detainer while the striking is on warning. 

 In this motion work, we have a rack, having teeth on 

 the inside as well as on the outside ; the tumbler raises 

 the rack by mean* of the inside teeth, the rack-catch 

 act* by those on the outside, and is concentric with 

 the hour lifting arm, or that which discharges the 

 uriking ; but both move freely and independently of 

 each other. When the rack is on the lifting of the last 

 tooth by the tumbler, a pin which i* in the rack carries 

 forward the end of a lever or arm. Concentric with 

 this ana, and fixed with it, another arm present* it- 

 self (at the same instant when the pin in the rack ha* 

 carried the ami forward) to a pin or detent on the fly 

 pinion arbor, and here the striking is locked. The pin 

 m the minute wheel, on raising up the hour lifting 

 raise* at the same time the rack catch, and conseqt 

 )y allows the rack to fall, and the pin from the fly pi* 

 nion arbor, which before this was locked, get* " 

 gaged ; and here the striking would go improperly on, 

 bat another arm, which i* connected with the hour- 

 sifting arm, priaimU itself to the other detent on the 

 fly pmion arbor, and detain* it till such time a* the 



heel. 



lifting arm drop* off from the pin in the minute w 

 and then the striking being at liberty goes on, ar 

 again locked when the pin in the rack is math to i 

 one of the locking ana* forward. This locking i* sure 

 and safe, and very easily *T*na1*d. 



The pin* of the p>n- wheel ought t* be pretty stoat, 

 and one half of their ^iliii^noald becataway.a. 

 tail to drop of freely, ceaemg 

 r of the force of the weight. 



The diameters of the wheels and the length of the Turret 

 barrels being determined, we may thence fix upon the ^ ^ 

 length and breadth of the clock frame, which is pro- 

 posed to be rectangular, and the wheels lying all 

 nearly in a horizontal position, making it of such di- 

 mensions as not to pinch any part of the work, nor 

 yet to have a superabundance of room. Beginning, 

 then, with the going part : The great wheel being 

 15.2 inches in diameter, and having 120 teeth, and the 

 pinion which it drives 10, we know that the distance 

 of their centres will be 8.08 1 , or 8. 1 inches nearly. We 

 also know, that in the case of the second wheel of ~.C> 

 inches in diameter, and 60 teeth, driving the third 

 wheel pinion of 10, the distance of their centres must 

 be 4.273 inches. In like manner, we get the distance 

 of the centres of the third wheel, and swing-wheel. 

 The diameter of the third wheel is 5 5OO inches ; the 

 swing-wheel pinion being 10, we have for the distance of 

 their centres, 3.158 inches. By taking these distances, 

 and adding them together, with the semi-diameters of 

 the great and swing-wheels, we shall have thespace that 

 would be required to contain the going part. 



Inches. 

 From the centre of the great wheel to that of 



the second wheel, 8.081 



From the centre of the second wheel to that 



of the third wheel 4.273 



From the centre of the third wheel to that of 



the swing-wheel 3.158 



The semiJaameter of the swing wheel, . . 2.5 

 The s*rnMheje*T of the great wheel, . . 7.6 



Inches, 25.612 



So that it require* 2 feet, 1 inch, 6 tenths, and a very 

 little more, to contain the going pan. 



By proceeding in the same manner, we shall find the 

 distance of the centre* of the wheels in the striking 

 parts to be a* follow* : 



I ncke*. 

 From the centre of the great wheel to that of 



the pin wheel, 8.1875 



From the centre of the pin wheel to that of 



the tumbler wheel 5.6815 



From the centre of the tumbler wheel to that 



of the fly pinion, 3.2541 



Semi diameter of tumbler wheel ii.75 



Ditto of the great wheel, 7.6 



a* to allow the 

 a* little 



tail may be so rnaeUiia.nl that it begins 



which it 



The 



to raise the hammer head when the lever by 

 act* i* at its maximum length, the bead having then a 

 more haraontal position than when it i* afterw.nl. 

 raised up. The principle laid down here of the striking, 

 Ac. was adopted and put in eujratian in the two tur- 

 ret clocks which were made by Mr Reid for the royal 

 burgh of Annan, and which are not equalled by any 

 turret clocks in the island. The frame of these clocks 

 i* so coMtracted, and the wheel* so disposed, that .ny 

 wheel can be separattly lifted out of the frame, without 

 either taking it to piece*, or removing any of the other 



To which add the 



required for the 



27.4734 



Give* for inches, 53.0854 



The length, then, required to contain the going and 

 striking parts is about 4 feet 5 inches, being the inside 

 length or the frame. 



The width inside of the frame, depends on the length 

 of the barrels, the thickne** of the ends, and nt' ih< 

 great wheel*, &c. The striking barrel being the long- 

 est, we must take the length given for it, which was 

 determined to be 0.25 inches between the ends. Allow 

 one quarter of an inch or so for the thickness of the 

 plain end, and half an inch for that of the ratchet end, 

 and about a- 4th* of an inch or so for the thickness of 

 the great wheel, these being l./i inch, which, added to 

 the length of the barrel, makes 10 7o inches. Tl. 

 wheel is supposed to run behind the great wheel, hav- 

 ing a proper freedom between them, the |.in-. > lirt- 

 ing the hammer tail being on the opposite i<le of the 

 pin wheel, and the plain barrel end having a sufficient 



