Bill wrote in
. 97.142:

I guess I was too smart for my own good I was trying to avoid the
official use of the word elevator so I was using the word dumbwaiter in
quotes to try to get my point across. There have been a few discussions
in the past about home elevators and mostly what came across was the
belief that no one but a 'professional' engineer should consider
designing one and people were derided for suggesting that they were going
to do it.

The 'dumbwaiter' in question will be 3 foot by 3 foot, 7 foot high and
have a carrying capacity of 500 pounds. (Nuddge, nuddge, wink, wink, say
no more, say no more....)

Most of the problems that people had with the idea of a home made
elevator was of using a winch to move the carriage up and down. None of
the designs had a good failure mode or means of stopping the carriage
from dropping 8 feet or so either with someone in it or the drop
happening when someone would be entering the carriage.

Since I'll be using a hydraulic cylinder to do the lifting I'm
eliminating the majority of that problem, hydraulics having a 'soft'
failure basically just lowering the carriage slowly if there would be a
pump failure, control failure or hose failure. What I'd like to do is
add an additional layer of safety in that I'd like to make it impossible
for the carriage to fall at all when on the upper floor even if the
entire bottom of the cylinder would be sheared off (for the life of me I
can't figure out how this would happen but....)

I've been thinking about it a bit more and I'm leaning toward something
like this.

The carriage comes up past a spring loaded pawl that is pushed out of the
way until the carriage gets past, then it snaps down again in a locked
position where the carriage cannot drop past but whould rest on the pawl.
To get the carriage down the system would have to raise the carriage up
an inch or so where to of the carriage would push against a lever that
would unlock the pawls and allow them to swing down. Once the pawls are
unlocked the carriage could be lowered past them to the ground reseting
the locking mechanism for the next lift. With it all mechanical I wont
have to worry about relays or solenoids or other complicated systems
failing and as long as we inspect the unit a few times a year I wouldn't
be worried about wear and tear negating the safety feature.

Now I just have to design it


Bill