128 APPLICATION OF CHAINS. 



common way) totally unnecessary; the pullies are in 

 consequence brought closer together, the angle of the 

 ♦ fall from block to block considerably diminished ; and 



the friction against the plates entirely avoided. Brass 

 guards, with grooves opposite to those in the pullies, 

 are riveted to the blocks, to prevent the chain getting out 

 of its birth from any accidental circumstance. This 

 method of working chains I first put in practice for 

 ^Vanouss"c- Messrs. T. W. and B. Botfield, at these works in July 

 tloas. last; and it is applied in the working of cranes capable 



of purchasing from ten to fifteen tons ; in the working of 

 the governor balls of steam-engines constructed by Messrsr. 

 Boulton and Watt, and in the raising of coal and ore from 

 the mines, for which purposes ropes had before been solely 

 used at this manufactory. In all cases it has {performed 

 with the utmost safety, uniformity, and flexibility; so 

 much so that the prejudices of our workmen against 

 chains are entirely done away, and they hoist the hea- 

 viest articles with more ease, and as great confidence of 

 safety as they would with the best ropes. 

 The method is The same method is applicable, at a trifling expense, 

 iroduced. *^' ^^ ^^^ machines at present worked by ropes, or by chains, 

 in the usual way ; and all the common chains now in 

 use, may be applied to it with equal facility. 

 Experiments. With a view of ascertaining the relative flexibility of 

 ropes and chains, I wedged an iron pulley, thirty-one and 

 a half inches in diameter, on the spindle of the pinion of a 

 crane of the following description, viz. 



Barrel, 30 inches diameter ; 

 Wheel, 64 teeth; 

 Pinion, 8 ditto ; 



Top block, with three pullies of 12 inches diame- 

 ter; 

 Bottom block, with 2 ditto, ditto. 



A chain ap- To the large pulley I attached a small rope, for the 

 plied in this purpose of suspending the weights in the hoisting of the 

 morc^flexTblf different loads, and the results were as follow : 

 and easy iu its The 



work than a 

 rope. 



