<)8 TATTKKX MAKFNG 



the pulley rim is to be f inch, this, with the allowance of -J inch 

 for turning out the inside of the iron ring, makes the inside diam- 

 eter of the wooden pattern 23 inches, and the thickness of the 

 wooden rim |f inch, all shrinkage- rule measurements. 



This wooden-ring pattern must be built up on a chuck, as 

 described for the 20-inch X 6-inch pulley, the segments, six in num- 

 ber for each layer, fitted, glued, and clamped with three hand screws 

 to each segment until a width of 6-| inches is reached. 



It is then turned to the above dimensions, without <i:nj draft, 

 and sent to the foundry, where it may be used for obtaining an iron 

 rim of any required width by first ramming the sand about the 

 pattern, partly drawing it, and then ramming again to a new level. 



The casting thus obtained is then turned to the dimensions 

 called for by an ordinary pattern; that is to say, the shrinkage-rule 

 measurements would leave it 23J inches in diameter on the inside 

 and 24 inches on the outside, permitting a final finishing of the 

 outside of the rim of the pulley to a diameter of 24 inches. When 

 this is done, two f -inch holes should be drilled near one edge of the 

 rim and diametrically opposite each other, into which hooks may 

 be inserted for drawing the pattern. This rim should also be 

 turned straight and without any draft. 



The arms are usually made with a wooden pattern, which has 

 a dowel-pin hole on each side at the center for attaching the hubs 

 that are loose, the object being to change their length and diame- 

 ter to suit the width of the rim and the diameter of the shaft upon 

 which the pulley is likely to be placed. 



The arms of all pulleys should be straight because of the 

 greater strength given to the pulley as a whole, the driving and 

 resisting power being at least one-third greater than in a pulley of 

 the same dimensions having curved arms. Curved and shaped 

 arms of all kinds are now used only for ornamental purposes and 

 for very light work. 



The arms should be six in number, except for very small 

 pulleys, when five and even four are often used. The dimensions 

 of the arms vary greatly, depending on the purpose for which 

 the pulley is to be used, and the weight of the machinery to be 

 driven. 



