I had an idea for a motorized caster yesterday and spent some time making a model of it. Up until now I haven't found a motorized caster or thought of one that I think would be small enough and powerful enough for a VR shoe. But this one might be.
It's 1.375in tall and 1.5in wide, so small enough.
The wheel on the bottom is tilted. It rolls on the side that is horizontal. The very top spur gear is used to turn the whole caster to set the direction. The lower spur gear is used to turn the upper bevel gear, which turns the slanted bevel gear, which turns the wheel. So lock the direction and turn the lower spur gear to move the caster in the locked direction.
It uses a few needle roller thrust bearings, a 6mm bearing, and a 6mm bent screw.
These are a few test pieces of the bevel gears.
I'm thinking that 2-4 of these could be put on a VR shoe under the heel, with 2 more under the ball of the foot and 2 more under the toes. The casters could be coupled together by belts so that 1 or 2 powerful motors could be used to drive them, and 1 or 2 smaller motors could be used to rotate them.
I'd like to allow the VR shoe to bend at the ball of the foot. The issue is that the casters on both sides of the bend couldn't be coupled by belts. The belt would bend and get stretched when the user bends the VR shoe. A possible resolution to this would be to have two spherical gears, one on each side of the bend. The spherical gears could have groves in them to create teeth. When the VR shoe is bent, the gears will still be in contact, with one gear moving along the other and the teeth of one gear sliding in the grooves of the other.