I have two parallel shafts, 3 millimetres in diameter and offset by 8 millimetres, both anchored in surrounding housing by ball bearings. When one shaft is rotated (via gear), I want the other shaft to rotate with it. I have less than a cubic centimetre of space between the shafts in which to place the coupling mechanism.
So far I have been using a stiff orthodontic elastic looped around high-friction rollers fixed onto the shafts. However, this introduces backlash, resistance, and unpredictability.
A timing belt would work well but the pitch length would have to be no greater than 1.07", which is smaller than any timing belt I can find on the market.
Any suggestions for coupling these shafts precisely in a space- and preferably cost-efficient way?
Edit: I believe the offset is too large for Oldham coupling. Here's an image of the shafts without surrounding housing: