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XXXIX. Description of an Improved Crane and Flex'dL: 

 Chains. By Mr. Gilbert Gilpin, of Old Park Iron- 

 Jf'urks,?iear Snifhat *. 



JlIavi.vg discovered a method of wording chains' of fh£ 

 common construction, over pulleys, in all directions, more 1 , 

 safe and flexible than the best hempen ropes, and at the sarafi 

 time equally uniform, I have sent, for the inspection of the 

 Society for the encouragement of arts, manufactures, and 

 commerce, a full-sized pulley in wood, and apiece of a 

 chain, together with a model of a crane, exhibiting its man- 

 ner of application. 



From its simplicity of form, and facility of manufacture, 

 the common chain, formed of bvW links,' has been in use 

 from the earliest ages ', and that it did not answer every pur"* 

 pose of a hempen rope, in working over pulleys, was not 

 owing to its peculiar form, but from an error in the appli- 

 cation. 



Every chain of this nature has a twist in hfclf,' arising 

 from a depression given by the hammer to each link in the 

 welding t ', and this circumstance, so trifling in appearance, 

 is not so m its effects, and it has in consequence a perpetual 

 tendency (even when reefed perfectly straight in pulleys, and 

 on the barrels of cranes) to assume a spiral form, which a 

 plain cylindrical barrel, and the common pulleys with semi- 

 circular groove's, are not in the least calculated to prevent. 

 Hence the alternate links of the chain, in coiling round a 

 barrel, or working over pullevs, form obtuse angles in as- 

 suming the spiral form, bearin^iipon the lower parts of their 

 circumferences, and forming as it were two levers, which 

 wrench open and crush each other in proportion to th'c 

 weight suspended, as well as prevent the freedom of motion 

 in the links themselves, and thereby load the chain with aoV 

 ditional friction. 



* From Transactions of Society ttfArts, he. ipoS. The silver medal of tTie 

 society and 80 guineas were voted to Mr. Gilpin for this invention ; and. 

 models of the crane and chain are reserved in the Society's Repository, for th; 

 inspection of the public. 



| The twist may be seenby holding the piece of the chain by one end, and 

 viewing the links edgewavs as it hangs down. 



A still 



