Purpose
The coupled driving wheels on steam locomotives (often simply called "drivers") were held in a straight line by the locomotive's frame. The flanges of the drivers were spaced a bit closer than the rail gauge, and they could still fit between the rails when tracking through a mild curve. At some degree of curvature, though, the flanges on the center driver would begin to bind in the curve. The farther apart were the front and rear drivers, the less track curvature the locomotive could negotiate. One solution was to make the center driver(s) without flanges on the tires. The other solution was to allow at least one of the axles (often the front driver) to move lateral to the frame, and such designs incorporated various devices to permit this motion.
Read more about this topic: Lateral Motion Device
Famous quotes containing the word purpose:
“... my one aim and concentrated purpose shall be and is to show that women can learn, can reason, can compete with men in the grand fields of literature and science ... that a woman can be a woman and a true one without having all her time engrossed by dress and society.”
—M. Carey Thomas (1857–1935)
“Science and art, or by the same token, poetry and prose differ from one another like a journey and an excursion. The purpose of the journey is its goal, the purpose of an excursion is the process.”
—Franz Grillparzer (1791–1872)
“I think the worst thing this nation could do for humanity would be to leave any uncertainty as to our will, our purpose and our capacity to carry out our purpose.”
—Hubert H. Humphrey (1911–1978)