Practical Carriage Building
Compiled by M.T. Richardson, Vol.1. 1891
To Find Length of Fifth-Wheel Before Bending
Some people have a practice of making a bushel of preparation to arrive at one gill of product. I have noticed a number of times how some blacksmiths go to work to find out how much iron it takes to turn a fifth wheel of a certain diameter. Long problems in figures have been shown, all of which would require more time to decipher than to cut the piece from the bar, and turn and weld and fit the wheel. It is an easy thing to do if one goes at it right.
First, with a compass, strike the outside diameter of the circle, as per circle A of the illustration. Then strike the inside diameter of the circle, as per circle C. Next strike a circle midway between the two, as per circle B. Take a thin piece of band iron, lead, or harness leather and start at X and end at X, by following circle B, and you get the exact length at which to cut off the piece, allowing enough for lapping and welding. The outer part of the iron elongates and the inner circle contracts in bending, but no change occurs at the center line. The whole business of laying out the circle and getting the measurement usually occupies from three to five minutes, and I never make a mistake.óBy IRON DOCTOR.