11-13-2012, 06:08 PM
(11-13-2012, 04:35 PM)doubleboost Wrote: I have seen gas struts used to reduce the load on the screw (tail gate struts)
John
John,
Thanks for the response. I've also see gas struts used successfully.
I dismissed them as (a) not being adjustable and (b) the weight involved seemed to be outside of the gas strut ... even multiple gas struts ... envelope.
I have also seen successful air cylinder implementations similar to diagram 2.
I guess my apprehension is centered around using the ball screw as both the "screw" and the "rod".
It seems to me that in diagram 2 the load is shared between the cylinder rod and the ball screw ... i.e. if the total table weight is 600 lbs and the cylinder is able to provide 400 lbs of force then the ball screw and ball nut will only see 200 lbs of downward force from the table to the nut and zero force below the nut.
And again, in my mind, in diagram 3 the ball nut only sees 200 lbs of downward force because the lower half of the screw is being pushed up by 400 pounds from the piston, but the part of the ball screw above the ball nut see the entire 600 lbs of force and part below the ball nut sees 400 pounds from the piston in the "anti-gravity" direction.
But now that I write it down the ball screw is not seeing any more force above the screw than it would have if there was no assist at all so why worry about it.
Yes, my head hurts.
Arvid