Solcar
10 kW
Here's an idea for a freewheeling roller. It ought to be doable in plastic since the forces at the tire are only 1/10 those of a hub-mounted freewheeled system like on a standard mid-drive.
The roller is in 2 pieces, side by side. The sides operate on simple bearings, there aren't any one way bearings that require locking to the shaft. This way, a small motor drives a pulley or sprocket via a belt or plastic chain on one of the sides, with the pulley or sprocket on the motor being smaller so that it gains mechanical advantage. With the motor off, the other side can freewheel, but once the rotational speed of the driven side exceeds the side on the tire, then the freewheel mechanism can lock and both turn at the speed of the driven side.
The mounting is done on the ends of the roller assy shaft, and are solidly attached with no bearings needed there. Only the bearings for each roller side are needed.
The locking mechanism should probably be paws attached to one side that go under the other side against saw teeth. Alternately, the paws could be on the side of one roller piece, with the saw teeth being on the side of the other so that they mate sideways, though dirt's more a consideration in this case, I think. It should also be possible to use a Bendix type of locking mechanism between the two sides.
The two pieces shouldn't be too hard to make with a 3D printer, which I don't have though.
The roller is in 2 pieces, side by side. The sides operate on simple bearings, there aren't any one way bearings that require locking to the shaft. This way, a small motor drives a pulley or sprocket via a belt or plastic chain on one of the sides, with the pulley or sprocket on the motor being smaller so that it gains mechanical advantage. With the motor off, the other side can freewheel, but once the rotational speed of the driven side exceeds the side on the tire, then the freewheel mechanism can lock and both turn at the speed of the driven side.
The mounting is done on the ends of the roller assy shaft, and are solidly attached with no bearings needed there. Only the bearings for each roller side are needed.
The locking mechanism should probably be paws attached to one side that go under the other side against saw teeth. Alternately, the paws could be on the side of one roller piece, with the saw teeth being on the side of the other so that they mate sideways, though dirt's more a consideration in this case, I think. It should also be possible to use a Bendix type of locking mechanism between the two sides.
The two pieces shouldn't be too hard to make with a 3D printer, which I don't have though.
