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tysonmarconi
08-20-2014, 12:07 PM
I was wondering why many casters I see have a horizontal offset that, at minimum is equal to the radius of the wheel. I understand that the amount of force required to turn the wheel will go up, and the pivot velocity will increase. Is there a fundamental reason why many mass manufacturers choose to go with larger offsets? I'd like to minimize the offset due to space constraints.

tician
08-20-2014, 02:59 PM
Basic answer is that if you do not offset the center of the wheel from the center of caster rotation (if the two axes of rotation intersect), the wheel will simply skid sideways instead of changing direction of travel when moving forward then pushed sideways. The larger the offset, the easier it is for the wheel to turn to the direction the caster mount is being moved but it also increases the torque on the caster bearing (increases cost) and increases in-place skidding/swerving of the the wheel (increases tread wear) during low speed maneuvering and/or rapid/complete direction changes.

There are ball casters in smaller sizes, omni-wheels can work in some larger situations, and you can make your own ball caster using 3+ omni-wheels equally spaced on top a large sphere.