The old man wants to put a 'dumbwaiter' into the barn so he can get
'stuff' up to the second story easier, he's getting old (79) and walking up
stairs is getting harder so I've been kicking plans around and want to see
if anyone could help with a detail I haven't worked out yet. I'd like to
make it that the 'dumbwaiter' gets locked in place when on the second
floor, was thinking of something like pawls on the guide tracks that the
carriage would click by so if the 'dumbwaiters' hydraulics would fail then
there would be no way for it to fall. This way if you are loading a couple
of hundred pounds on it it can't suddenly drop taking your arms, legs or
feet with it, although since I'm planning on hydraulics it would take a
really big failure of the cylinder to get that fast a drop. What I'd like
to do is make it that the 'dumbwaiter' would have to be raised a few inches
before going down to disengage the pawls but I'm not sure how to go about
designing it to do this. I could do it with a solenoid but I think that
adds another failure point and would rather have it be all mechanical in
nature. I'm not worried about a failure while ascending or decending since
the failure mode would be a slow descent as the fluids bleed out, so I
don't need pawls all the way up the guide rails just at the 2nd floor.
Anyone ever seen something like this and could point me in the right
direction??

Just remember this is a for a 'dumbwaiter' not an elevator, I don't want
the nanny's out there panicing about giving advice or suggestions for an
elevator and I'm not looking for designs just an idea how I might go about
making a pawl that can be disengaged by raising a platform higher. I just
want to add as many layers of protection as I can.

I've got some general designs on paper and as soon as I flesh it out a bit
more I'll start crunching numbers for loading and stress for beem sizing
and such. I plan on over building the 'dumbwaiter' but not stupidly
overbuilding it

Bill