Wheel Diameter, Wheel Width, and Tandem Wheels
The outer diameter of a caster wheel affects how easy it is for the caster to be able to move across rough or irregular surfaces. Large diameter caster wheels are able to bridge wide gaps where a small caster would fall inside and get stuck, such as the gap in the floor between an elevator door and the elevator car.
However, the larger diameter a caster wheel, the higher or wider the caster support arm must be. Either the base of a low-hanging object must be lifted higher above the wheels, or the casters must hang out to the sides straddling the low-hanging supported object. Large diameter swivel casters also typically need much more room to rotate the vertical shaft than a small caster.
Load capacity may be increased by using wider wheels with more ground contact area. However, when rotating a wide swivel caster in-place, the center part of the wheel-to-ground contact patch rotates slower than the regions further out to the sides. This difference in rotation speed across the base of the wheel contact patch causes wide wheels to resist rotation around the swivel, and this resistance increases as weight loading increases.
An alternate way to increase load capacity while limiting swivel-rotation resistance is to use multiple narrow wheels in tandem on the same wheel axis. Each wheel has a comparatively narrower ground contact patch than a single wide wheel, so there is less resistance to turning in place on the swivel.
Read more about this topic: Caster
Famous quotes containing the words wheel, tandem and/or wheels:
“The wheel and the brake have different duties, but also one in common: to hurt one another.”
—Friedrich Nietzsche (1844–1900)
“The Cad is the entire epitome, the complete blossom and fruit in one, of what we are told is an age of culture. Behold him in the vélodrome as he yells insanely after his kind as they tear along on their tandem machines in a match, and then ask yourself candidly, O my reader, if any age before this in all the centuries of earth ever produced any creature so utterly low and loathsome, so physically, mentally, individually, and collectively hideous?”
—Ouida [Marie Louise De La Ramée] (1839–1908)
“Let a man find himself, in distinction from others, on top of two wheels with a chain—at least in a poor country like Russia—and his vanity begins to swell out like his tyres. In America it takes an automobile to produce this effect.”
—Leon Trotsky (1879–1940)