Improved Crane and Flexible Chains. 253 



\ V A still greater obstruction to the uniformity of its motion, 

 is the tendency which the chain has to iriake a double coil 

 as it approaches the middle of the barrel and crosses its cen- 

 tre, and that of the pulleys at right angles, by means of 

 which the chain is frequently broken by the sudden jerk 

 caused bv the upper coil slipping off the undermost. 



It is to these causes that all the accidents that occur to 

 workmen and machinery from the failure of chains may be 

 attributed (bad iron excepted), and which form the sole ob- 

 jection to their becoming a general substitute for ropes. 



As a preventive to these evils, I have grooves cast in iron 

 pulleys, of sufficient dimensions to receive the lower circum- 

 ferences of the links of the chain, which work vertically ; 

 those which work horizontally and form the gudgeon pari of 

 the chain (if we may be allowed the expression), bearing 

 upon each bide of the grooves. 



The barrels are also of cast iron, with spiral grooves of the 

 same dimensions, at such distance from each other as to ad- 

 mit the chain to bed without the danger of a double coil ; by 

 these means the links are retained at right angles with each 

 other, the only position for free and uniform motion. 



The links of the chains are made as short as possible, for 

 the purpose of increasing their flexibility, and they are 

 reefed perfectly free from twist, in the pulleys, and on the 

 barrels, for the same reason. 



When applied in blocks, the grooves in the pulleys prevent 

 the different falls of the chain from coming in contact, and 

 render plates between them (as in the common way) totally- 

 unnecessary ; the pulleys are in consequence brought closer 

 together, the angle of the fall from block to block consider- 

 ably diminished, and the friction against the plates entirely 

 avoided. Brass guards, with grooves opposite to those in 

 the pulleys, arc riveted to the blocks, to prevent the chain 

 getting out of its birth from any accidental circumstance, 

 '[his method of working chains I first put in practice for 

 Messrs. T. W. and B. Botlield, at these works, in July last ; 

 and it is applied in the working of cranes capable of purchas- 

 ing from ten to fifteen tons 5 in the working of the governor 

 fcal's of steam-engines constructed bv Messrs. Boulton and 



Watt, 



