Mathew J. Newton wrote:

I am hoping some kind and able soul out there with a lathe and/or milling
machine might be able to help me out here....
The following diagram shows roughly what I am doing from a mechanical
perspective:
http://www.newtonnet.co.uk/permanent/feederdiagram.png


Can't help you with the machining (perhaps a quiet word with a local
technical college tutor/techy teacher at the local high school).

I would imagine a 'weak link' would be required rather than stalling the
motor,and possibly setting fire to the place, the weak link would 'give'
so it was fairly easy to replace perhaps the coupler with the two grub
screws could be made to be easily (relatively) broken so you could just
replace that rather than the shaft, the motor or one of the rubber vanes.