Practical Carriage Building
Compiled by M.T. Richardson, Vol.1. 1891
Shortening of Bent Beds
The propensity of a bent piece of wood to shorten the cord of the arc is a peculiarity observed by body makers in using bent bottom sides; also by carriage part makers in working out bent bottom and top beds. No information, however, has been given as to what extent bent pieces are thus changed, and therefore data relating to the subject may prove to be of interest to others, as it was to me.
A carriage part maker a few days since brought to me a finished bed that he had worked out a day or two previously, and it had shortened in the way to which I allude. The bed was of ash, coarse, straight grain, and the form fibers of the average for good timber. The bed originally was five inches deep, being of the usual thickness—about two inches. It had been made to finish the full depth of the bed. The two ends were dressed horizontally on the dotted line B, as shown by Fig. 209, with the distance from B to B four and a half inches. The distance from A to A was thirty-seven inches.
When brought to me the distance A A measured thirty-six and five-eighths inches, showing that the bed had shortened three-eighths inch, and the distance B and B had increased from four and a half inches to four and eleven-sixteenths inches. The horizontal line B of the bed had not changed materially. One end was perfectly straight, while the other had changed slightly. Let D be supposed to be the end that had changed. By placing a straightedge against this face, it was found that it failed to touch the face D by about one-eighth inch. Owing to the fact that but one end had changed from the horizontal, the inference was drawn that the change was due more than anything else to the nat¬ural inclination of timber to spring.—By Jeff Potter.