Re: Need speed switch for DIY funicular/hillside elevator

["Robert L Bass" <robertbass1@xxxxxxxxxxx>]

<astutesolutions@xxxxxxxxxxxxx> wrote in message news:1162305387.636509.139790@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Thanks Robert.  Yes, I'm thinking more and more of a solution like
> this, but I'm not as concerned of a breaking cable as I am the
> freespool event.  Each cable is rated at 8,000 lbs.  The cart fully
> loaded would be around 1,000 lbs at 29 degree slope.  At this slope,
> the load would be about 500 lbs per cable which is 1/16 the max load of
> a single cable.  So if one cable were to fray and break, the other can
> handle the load easily.  I have them going through pulleys, but there
> is also a backup attachment to the cart, so if one cable breaks it will
> still have an attachment to the other cable.
>
> But, it is possible I think to have the 3rd cable as you mention with a
> springed arm of some sort that would "grab" the cable if the tension of
> the primary cables released.  I suppose I could adjust this "trigger
> point" by adding additional springs such that the trigger tension was
> almost to the point of catching.  If I were to set it up such that the
> trigger locked and wouldn't let go, I'd run the risk of someone
> jostling the cart when they get on, releasing some tension and
> triggering the lock.  Perhaps a scaled approach that the less tension
> the greater the "grab" would work, if that makes sense.

Actually, I was thinking that you could use one or both of the main cables to operate the brake.  The third cable idea was from
another gentleman.  Given what you've said about the weight, slope and cable strength, I seriously doubt you'll have a broken cable
issue.  If you use the operating cables to keep the brake pulley / lever taught, the weight of the tram will keep anyone from
jostling the cable off the pulley.  You can use a catcher (U-shaped cover) above the pulley so that the cable is trapped at the top
if this is still a concern.

The main reason I like this idea (really from Doug's suggestion) is it's simple.  It require no electronics and no electrical power
to operate.  Also, you could easily build in an over-ride to allow the tram to descend in the event of an erroneous safety system
deployment or a single cable failure.  A manual lever could be operated to allow you to walk the tram down the hill.

--

Regards,
Robert L Bass

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