Re: Need speed switch for DIY funicular/hillside elevator

[Frank Olson <Use_the_email_links@xxxxxxxxxxxxxxxxxxxxxx>]

astutesolutions@xxxxxxxxxxxxx wrote:
>>Elevators often have a brake that is held off by the cable tension where
>>it attaches to the cab.  you can do the same thing, the cable attachment
>>holds open a brake that would grab the rails.  If the cable breaks or
>>loses all tension the brakes grab.  Even if the cable slacks, there
>>should still be tension at the cart attachment point.  This is totally
>>automatic, no user input.
>>
>>--
>>Free men own guns - www.geocities/CapitolHill/5357/
>
>
> Nick, I undestand what you are saying.  I suppose you just have to be
> there to see it, but the cable is quarter inch aircraft cable and is
> pretty stiff.  It is long too, over 150 feet.  When that cart goes down
> in a freespool condition (drums rotating freely) it will be dragging
> that cable down with it.  As it drags it down there is going to be some
> tension there because the drums/spools have some inherent resistance
> until they build up speed.  Even when the cart goes down, the cable
> sags in between the supports some.  I guess what I'm trying to say is
> that I don't know an easy way to indicate that tension drop.
>
> In the event that both the cables snap, this would work beautifully,
> but both would have to break at the same time, and each one is rated
> for about 7,000 lbs.  Thanks!
>


What you need to do is rent yourself a "cable load meter".  Attach to
one of the cables right at the cart.  Go "up" and "down" a couple of
times and then move it to the second cable.  Repeat the process.  You
should be able to confirm that there is tension in the cables regardless
of whether you perceive they're going "slack".  If this is the case,
using Doug's idea would be the simplest solution for you.