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XLIII. Description of an improved Crane for IVharfs. Bif 

 Mr. Robert Hm^ljujuot, ofBasford, near Nottingham. 



Jb onry guineas were voted to Mr. Hall, by the Society for 

 the Encouragement of Arts, &c., for his ingenious inven- 

 tion of a mtthod to expand a set of bars parallel to the axis 

 of a crane, by which means the velocity of the rope in 

 raisins^ weights may be increased or diminished in propor- 

 tion to the load to be raised. 



A description and engraving of this crane are given in the 

 twelfth volume of the Society's Transactions, from which 

 we have drawn up the following account of it; 



The ends of the reel (fig. I and 5. Plate IV.) consist each 

 of two flat plates or circular pieces, shown separately in 

 iTg. 2 and 3. These circular plates form the two ends of 

 the reel, and are held fast on the spindle or axis by pins 

 passed through its ends, of which one may be seen at a, 

 tig. 2, and another in the end shown in fig* 3. The outer 

 circular plate (fig. 3.) of each end of the reel has a spiral 

 groove cut in it, as shown at b, and the inner circles have 

 each eight mortices cut quite through them, as shown at c, 

 lig. 2. (seen partly also in iig. 1 and 5.) The outer plates 

 have also an iron tube, d, )nade fast to them by means of a 

 tlange or collar, and the screws, ee, fig. 2. 



When the parts are all joined, (as shown in fig. 1.) the 

 axis f passes througli the tube d, and thus the ends are 

 connected. In fixing the cross bars, two of which are 

 shown detached in fig. 4, the parts g,'^' slide in the mor- 

 tices c of the inner circular plates, and the small ends or 

 tenons h,h go fairly through the inner and enter the spiral 

 grooves of the outer plates. 



The inner and outer circular plates are locked together by 

 a catch (/, fig. I, 2, and 6.) the stationaiy part of which is 

 made fast to the inner plate (see fig. 2), while the catch it- 

 self, by means of a spnnof, is kept in a notch on the edge 

 of the outer p'ate. When the diameter of the reel is to be 

 enlarged or diminished, it is effected by bringing the reel 

 round to the position shown in fig. 6, when a hook, k, is 

 put into a hole, /, which keeps the iimer circular plate in 

 that position till the adjustment is made by lifting the catch 

 from the notch of the outer end-plate far enough to be kept 

 disengaged by the hook ^, before mentioned, being thrust 

 quite through the hole I: the handle m being then turned, 

 the outer plat"? only is carried round, and the tenons or 

 small ends of the cross bars (being prevented from being- 

 carried 



