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The wagon-wheel effect (alternatively called stagecoach-wheel effect) is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. The wheel can appear to rotate more slowly than the true rotation, it can appear stationary, or it can appear to rotate in the opposite direction from the true rotation ...
Wheels can also lose traction when surface conditions reduce available traction such as on snow and ice. As an open differential delivers only enough torque to cause the "weakest" wheel to spin, if one drive wheel is stationary on a low traction surface (mud, ice, etc.), the deliverable torque is limited to the traction available on it.
When traveling in a straight line, where one wheel starts to slip (and spin faster than the wheel with traction), torque is reduced to the slipping wheel (Trq 2 ) and provided to the slower wheel (Trq 1 ). In the case when the vehicle is turning and neither wheel is slipping, the inside wheel will be turning slower than the outside wheel.
It accounts for the "wagon-wheel effect", so-called because in video, spoked wheels (such as on horse-drawn wagons) sometimes appear to be turning backwards. A strobe fountain, a stream of water droplets falling at regular intervals lit with a strobe light , is an example of the stroboscopic effect being applied to a cyclic motion that is not ...
The greatest effort is required from a locomotive when starting. At this time, if the engineer applies too much power to the wheels (i.e., for a steam locomotive, the engineer opens the regulator too far) the turning force applied to the wheel will greatly exceed the opposing friction force affected by the surface of the rail, and the wheel will turn without being able to move the train forward.
The main advantage is that the driver does not need to leave the vehicle to connect the wheels to the axle. The disadvantage with this system is that most designs require the vehicle to move some distance (usually a whole wheel turn, often going backwards) after engaging the hubs in order for the hubs to engage or disengage.
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The stroboscopic effect makes each seem to be a single animated object. By allowing the rotation speed to be slightly out of synchronization with the strobe, the animated objects can be made to appear to also move slowly forwards or backwards, according to how much faster or slower each rotation is than the corresponding series of strobe flashes.