Re: Need speed switch for DIY funicular/hillside elevator

[astutesolutions@xxxxxxxxxxxxx]

Thanks Dave.  Each cable is rated at 8,000 lbs and the cart is 1,000
lbs fully loaded on a 29 degree slope, so yes, 2 cables is way
overkill, but since our wheels were on round pipe we thought it would
also be beneficial to have the alternate cable to prevent listing from
one side or the other as the cable changed positions on the drum.

We originally were going to use the other drum as a counterweight, but
we discovered our motor and gearbox powered everything so easily with
no strain (even the lights in the house don't flicker when it starts,
like my HVAC compressor does), so we went with the 2 cable design.  We
weren't as concerned of overloading a single cable as much as we were
long therm exposure to the elements and constant use.  I guess a wear
break was a larger concern.  So, IMO, I disagree with it being a design
flaw, although it may be over designed.

I do agree with the KISS methodology however and having it constantly
inspected.

We did have the drum assembly professionaly built by machinists that
build drums as part of their business.  My dad, who designed and
contracted out the metal work insisted on using that supplier instead
of a normal machine shop, and I fully agreed.

A winch solution may be a solution for something like this, but it
wouldn't make sense to scrap what I have already to solve for a
scenario that should be unlikely, but not impossible to happen.
Thanks.  Jeff
Dave Houston wrote:
> I didn't say they were _all_ Goldbergian.
>
> I spent about 20 years in the machine tool industry where safety was a prime
> concern. It was always my philosophy that safety, like quality, is something
> you design in from the beginning of the process rather than something you
> paste on at the end of the process. Another thing I strongly believe is that
> the possibility of catastrophic failure grows geometrically with design
> complexity so - KISS. We had a machine that had to overcome gravity to
> operate and I always figured that, should gravity fail, trial lawyers and
> product liability suits would be the least of our concerns.
>
> If a cable snaps, it's likely to decapitate an occupant (or occupants) of
> the tram so a broken cable is unacceptable and having redundant cables is,
> IMO, a serious design flaw. I think a single, adequately over-sized cable,
> driven by a large diameter drum and inspected regularly (on a rigid
> schedule) is better.
>
> The drum then becomes the single failure point where you need protection
> and, as I already stated, you will likely find winch manufacturers have
> already dealt with preventing runaways.
>
> astutesolutions@xxxxxxxxxxxxx wrote:
>
> >I don't think that all the suggestions are necessarily goldbergian.
> >There are 2 possibilities, stop it at the head unit (at drums) or stop
> >it at the cart.  Each offers its challenges, but not impossible.  Its
> >just a balance between what I can actually build, and what will take
> >the least amount of maintenance.
>
>
> http://davehouston.net
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