Check out an extension ladder.


"Steve W." wrote in message
...
Bill wrote:
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

Sounds like the pawls they have on many auto lifts. Basically an over
center cam pawl. When the lift passes them they rotate up and when it
clears they drop back. To retract them the lift I have has a simple bar
that has pins that engage slots on these pawls. Pull the release cable and
raise the lift and they retract.

--
Steve W.
Near Cooperstown, New York

Life is not like a box of chocolates
it's more like a jar of jalapenos-
what you do today could burn your ass tomorrow!