I think I'm in a bit of trouble here, I don't understand any of that :-|

I have kind of copied the original design including the number of teeth used on each pulley. The designer uses a 70t reduction pulley which I hadto change to 72t, other than that I have sourced exactly the same pulley and shaft sizes.

I'd like to use r&p if I was being honest with myself but it all seems to be very expensive which is a shame.

Thanks very much for your excellent response, hopefully if I stare at it long enough i might understand it lol