1C6 



HOROLOGY. 



Turret 

 Gtedu 



freedom of the front bar of the clock frame. We shall 

 his freedom about .3 of an inch, and as much 

 for the freedom of pin wheel and great wheel ; the 

 thickness of the pin wheel about .4 of an inch, o r a ve- 

 ry little more ; the height of the pins from the surface 

 of the pin wheel about .6 or .7 of an inch. 



Inches. 

 The length of the barrel, with its additions, 



was, 10.75 



Freedom of plain barrel end, 3 



Ditto of great and pin wheels, .3 



Thickness of pin wheel, .45 



Height of pin wheel pins, 7 



And take the distance of their tops from the side 



bar of the frame at 1.25^ 



Inches, 19.7T 



By this it appears that the distance between the bars 

 of the frame inside, will require to be 13.75 inches. 

 The side bars, one on each side of the frame, are of 

 forged iron, about four inches in breadth, and .4 of 

 an inch thick, having at the ends a sort of thickness 

 left there, so as to form a shoulder, and beyond the 

 shoulders are tenons, not quite so thick nor so broad 

 as the bars themselves ; these tenons about 4.5 or .5 

 inches long, are fitted into a rectangular hole, in the 

 cast iron part of the frame, which compose the ends 

 of it. The ends of the tenons are sometimes form- 

 ed into two screws, each having nuts to bind them 

 against the shoulders, and with the cast iron ends : or 

 having sometimes slits in them to receive a strong iron 

 wedge to bind the shoulders; either of them will do 

 very well. The length from shoulder to shoulder of 

 the side bars need not lie quite so much as that which 

 has been allowed for containing the going and striking 

 wheels. If this length is 4 feet 4 inches, it will be 

 sufficient; the space given by the cast-iron frame ends 

 will more than compensate what has been deducted 

 from the calculated length. The cast-iron ends are 

 composed of two sorts of pillars, connected by a rec- 

 tangular bar, near 5 inches broad, and about half an 

 inch thick ; the length of the rectangular bar such as 

 to allow the side bars, when the tenons are into the 

 square part of the pillars, and in the rectangular hole 

 which is made there to receive the tenons, that the in- 

 side of the side bars shall be only distant from one 

 another 13-75 inches. The middle part of the pillars 

 is a square of about 3 inches, and 6 inches long ; the 

 upper and lower ends of the pillars are turned into 

 such a figure or shape, as the taste or fancy of the 

 artist may suggest. The middle of the rectangular 

 hole which receives the tenons, may be distant from 

 the lower end of the pillar about 12 inches; the top of 

 the upper end may be equally distant. This frame, if 

 constructed in the manner which has been directed, 

 will be found to be strong, firm, and stiff, and very 

 handy and convenient, while going about the making 

 of the clock. Should it be thought that the side bars 

 from their length may yield a little, a foot can easily 

 be attached to each, near to the middle of the bar, or 

 any other convenient place. 



Nothing about a turret clock requires more skill and 

 ingenuity, than to construct properly the wheel work 

 lor setting off and carrying the hands to the different 

 dials, more especially if there are more than two. 

 The wheels for this purpose should be as few in num- 

 ber as possible, having the least allowable shake be- 

 tween the teeth, and a sufficiency of freedom in the 

 end shakes of the arbors, and in the conducting rods. 



Turret clocks with four dials and hour and minute Turret 

 }IMH!S to each were formerly but very seldom made. Clocks. 

 The town clock of Edinburgh has four dials, with hour s "" T""" 1 

 and minute hands to each, which we put to it in the 

 year 1 795. It is an excellent specimen of this sort of 

 mechanism. Hooke's joint has been found very useful 

 in the conducting rods for the dial work ; but where 

 any oblique direction is given to the rods, Hooke's 

 joint will make the hand rather to go irregular, making 

 the hand more forward at one part, and more behind 

 at another than it ought to be. In large turret clocks 

 which have minute and hour hands, the wind and wea- 

 ther give a very severe trial to the dial-work and 

 wheels, and such clocks are in general very much ex- 

 posed to such trials. In the clock which we have 

 been planning, the second wheel pinion making one 

 revolution in an hour, is that which must conduct 

 the dial work. Let that pivot of it which comes through 

 the fore side bar be left pretty thick, and prolonged 

 three or four inches beyond the bar outside. Two 

 ways have been adopted to prevent the hands from 

 changing their place by any force or violence, arising 

 from winds or any other cause. One of them consist- 

 ed of a pretty stiff or strong circular spring, keyed on 

 behind the minute wheel ; the other consisted in put- 

 ting on the minute wheel arbor, a wheel with square 

 or unrounded off teeth, into which teeth a click from 

 the conducting wheel passed into the space or spaces. 

 We propose to adopt the first of these two methods 

 at present. On the thick pivot of the second wheel 

 pinion, outside of the front bar, let a square be 

 made of .3 of an inch long; on this let the square 

 socket of the circular spring be well fitted, and the 

 side or angle marked to correspond, so as to know 

 at all times that which it has been originally fitted to : 

 this spring may either be of steel or brass, and the 

 diameter equal to that of the minute wheel less by 

 the teeth. From the square part of the pivot let this 

 arbor be turned down, but hardly more than what is 

 necessary to form an arbor nearly cylindrical ; the 

 square sides must not be completely turned out, other- 

 wise this might render the arbor too small. The dia- 

 meter of the minute wheel may be about 4.5 inches, 

 and cut into 40 teeth ; on the same socket with the 

 minute wheel, let there be a bevelled wheel of 5.5 

 inches in diameter, and having 50 teeth, the distance 

 of the back of the bevelled wheel from the nearest side 

 of the minute wheel being about half an inch, or .6 of 

 an inch. This space is to allow the hour lifting arm to 

 come in between them, so that the lifting pin in the mi- 

 nute wheel may freely get hold of it ; the whole length 

 or height of the socket may be about 3, or 3.5 inches, 

 and turns on the cylindrical part, or arbor of the pro- 

 longed pivot. Two other bevelled wheels of the same 

 number and diameter as the other are cocked on the 

 front bar, so as to pitch with the first ; their arbors are 

 disposed horizontally, and at right angles to the socket 

 of the first bevelled wheel, so that they may be connected 

 with the dial wheels on the two opposite dials, whose 

 wheel and minute hands they will conduct. Over the 

 first bevelled wheel, and pretty near the inside of it, is 

 placed a round brass dial, having minute divisions and 

 figures on it. A minute hand on the socket, having a 

 collet against them pinned by the end of the arbor, 

 will keep the minute wheel tight on the arbor by 

 means of the spring behind it. When there are four 

 dials, then in place of the two wheels, with their arbors 

 horizontally placed, let there be one arbor placed per- 

 pendicularly, on which are fixed two bevelled wheels, 



