Ballscrew design and 12vdc rpm and torque calculations help required

[rjsutton]

Hi John
you are nearly correct
the "chair is actually lifted by the 2 grab handles ( these are bolted to the substructure of the chair and when they use a hoist the bracket hooks these) i have 2 fold out arms off the fork that have channels made in them that go under the round grab rails. A simple sliding plate then slips down to "lock" the handles to the machine.
this is lifted bu the fork plate and then it moves back into the car . As soon as the chair is back about 200mm the wheels actually roll on the sliding plate so the weight is really off the arms then. the whole plate -forklift etc rolls back inside a separate subframe. The reason being the main plate needs to move out of the car first ( it goes out 400mm with a linear actuator mounted below) so it clears bumpers-towbars etc
then the chair is moved out the full 900mm and lowered to ground. This way its only the weight of the chair thats lifted vertically not the plate etc as well
also you can park the chair first as the arms come out and down to pick it up. If it was on a plate then that would have to be in place first obviously .
I think its bloody ingenious ( but i would wouldn't I ) :)
the complete size is 1000 wide x 900 deep x 740 high which will slip between most suv type vehicles wheel arches and fit in the boot height. I drive a new CRV and it fits in there ( or will) when finished.The fork lift caused problems as ive reversed the chain-sprocket arrangement to only need 325mm to lift the fork-chair 650mm so it doubles the force required to lift it.tried 2x 4kn actuators which failed miserably . changed to a direct chain and sprocket drive thru a reduction box which could lift the moon. anyway im waffling
thanks for your interest
Richard