Cant help thinking of my ex-girlfriend now... One christmas she put on over 2 stone in weight... Then tried to startve herself slim but after a couple of days kept whining on about feeling hollow...

Whether she was full, or hollow, there was definite sagging in the middle.. And it did take a huge amount more force to get her moving...!!

All this interesting stuff about hollow lead screws aside, I think i had better check the real critical aspect to this.. Cost! Had originally thought of dual drive rack & pinion, which would have allowed less powerful motors (was looking at http://www.oriental-motor.co.uk/uk/s...r=1240&sgid=72 which is a mechmate european recommended motor), but the rack itself look expensive.. If anyone can point me to good sources for R&P, and I am assuming Zapp is as cheap as anyone on lead screws and ballnuts..?

Better get my calculator out and work out some prices..

Steve.