Page:Sheet Metal Drafting.djvu/76

62 is 14" and the surface area is 14×8.377=117 sq. in. (nearly). One square foot or 144 sq. in. of No. 24 galvanized iron weighs 1.156 lb. Therefore, 117 sq. in. would equal of 1.156 or 1.136 lb. (Ans.)

The table given below shows the weight in pounds per square foot of the gages of metal in common use in the shop.

Problem 13P.—How much would a 90°, 7" elbow weigh if made from No. 22 galvanized iron? Elbow to have standard radius but to be "peened."

Problem 13Q.—What would be the weight of a 90°, 8" elbow having a throat radius of 8" and made of No. 20 black iron?

Note.—When the throat radius is less than standard, add one-half of the diameter of the big end to get the center line radius.

Problem 13R.—How large a piece of iron would be required to make a 75°, 10" diameter, standard blow pipe elbow of eight pieces? Add ¾", for a lap on each piece, to the length of the center line radius.