Hi Kstan,

Thanks for your comments. Since my first mail I've done a bit more research and it looks as if it is possible to buy just the stepper motors (without gearboxes) with the dual shafts which are required to fit the encoders. In summary the most expensive motor with gearbox costs around £63, the motor on its own around £24. It looks as if most motors are available as dual shaft versions and I don't see why I can't retrofit them. The down side is that these motors will probably not have the additional holes required to bolt on the encoders (not insurmountable). I also read a posting from Chris which said that the improvements provided by the encoders (for an AR2 to AR3 upgrade) were probably not worth the expense. If I buy the AR3 motor/gearbox set and the six encoders I estimated this to be around £350 on-cost.

Based on this I think I will just upgrade the 3D printed covers and wiring. Where I need to do some work is on the J5 movement as in my arm this has a lot of slop in its movement. I probably need to have a better way of tensioning the drive to this joint . It may be possible to provide feedback just for this joint which would be a cost effective improvement.

Thanks, Keith