I am designing a robot for industrial use. I am currently using a worm drive gearbox that drives the rotation using a V-belt system. To permit the end user to disengage the drive mechanism, and move the equipment by hand, there is a clutch-like mechanism that adjusts tension on the V-belt. So, when the v-belt is slack, they can move it by hand.
However, this design also means that the encoder I have on the motor is not going to help me after the user has made use of the clutch. So, I need an encoder on the main shaft of the equipment. Currently, I have a 5-sensor Single Track Grey Code system that gives me 12deg of resolution. https://en.wikipedia.org/wiki/Gray_code#Single-track_Gray_code
However, ideally I would like much better resolution. So, I am trying to work a commercial absolute encoder into the system. I have a hollow shaft that is 1 1/4" Dia, and a solid shaft that is 2" Dia. Here is one that can adapt to various shafts, http://www.mouser.com/ds/2/670/amt20-534922.pdf
But, its max is an 8mm shaft. And since my 1 1/4" Dia. shaft is hollow to allow for wiring to go though, I can't just make a adapter at the end.
So, I think I need to use a timing belt connection to tie the large shaft to the small shaft of an encoder. But, this is proving to be a challenge as well. The timing belt pulleys I find, that are for narrow belts, do not come with large bore sizes. At Martin Sprocket, their timing belt pulleys that can handle my Shafts are for 1/2" belts, and the pulley is 1 3/8" Thick. I don't have much space to fit this, and this is a bit tight for my space. I also would prefer a thinner belt, so hopefully my encoder can just take the pulley without any special effort to support the force of the belt and weight of the pulley.
Any suggestions for a source for timing belt pulleys for narrow belts, but for up to a 2" dia shaft? Or alternatively, a different method of putting an encoder on a shaft, but not on the end?
Thanks for any ideas,