Brake method needed for hillside lift

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(this is a repost from comp.home.automation).  Thanks.

My dad and I built a homemade hill lift (in Europe refered to as
funiculars) in Eastern Tennessee.  You can see a working demonstration
and picture of it at:

http://www.funimag.com/photoblog/index.php/20061026/a-do-it-yourself -...


The tram works fine, but I am trying to figure out some kind of simple
safety mechanism in the event that the spools break loose from the
gearbox or shaft and start rotating freely.  Since my wife and kids
ride this thing, I'd like some kind of backup solution in the event of
major catastrophe.  We are using 2 cables instead of one even though
one can handle 5 times the max load, and we have a braking motor to
stop, but both of those would be moot if the spool spins out of
control.

I am thinking of having some way of measuring the outfeed speed of the
cable (or spool) and have some emergency brake apply if a limit is
exceeded.

Any suggestions?  I thought about putting fan blades at end shaft of
the spool to have air slow it down, but that would be a little
unsightly.  I'm looking for a simple solution, one preferably without a

computer since this is outdoors and needs to be functional 100% of the
time.

Thanks in advance.
Jeff


Re: Brake method needed for hillside lift


The simplest way would be to wrap and connect the cable to (a spring
loaded?) spool under the carriage that would allow a lever to drop down on
some type of stops affixed to the tracks so that if the cable ever became
slack it would drop down and engage on one of the stops.
I remember this method being used on larger garage doors as a safety in case
the counterbalance failed.
Let me know if this makes no sense verbally and I'll sketch it out for
you....


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Re: Brake method needed for hillside lift



Gemini wrote:
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Yes, this makes sense but the only problem is detecting the slack.
Since the angle is 30 degrees and travels about 150 feet, the cable
naturally has slack when going down.  It rests on the support a bit as
the cart pulls it down.  Also, in a freespool event where the cable
drums are moving freely, there wouldn't be enough slack to react on.

One one of the other boards (comp.home.automation) a suggestion was
made to hook up the drums to an air compressor (without the electric
motor) such that it would have resistance at higher speeds.

Thanks for the suggestion!


Re: Brake method needed for hillside lift


This might be a bit complicated, but a centrifugal brake should do the job.
Ideally, the brake engages if the drum starts spinning.
As the brake slows the drum, it eases up a bit, allowing a safe descent.  ISTR
they use something like this on the tram at a ski
lodge in NH.

Thinking it up was easy.  Engineering it is outside my skill set.  :^)

--

Regards,
Robert L Bass

=============================>
Bass Home Electronics
941-866-1100
4883 Fallcrest Circle
Sarasota Florida 34233
http://www.bassburglaralarms.com
=============================>

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Re: Brake method needed for hillside lift



Robert L Bass wrote:
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Yes, a centrifugal brake or something similar to it is what we need.
Finding an easy way to do it is what I'm struggling with.  Thanks!


Re: Brake method needed for hillside lift


How about a clutch off of a go-cart or such. A gear on the cable spools and
a short chain to the gear that is already on the go-cart clutch assembly.
The normally "driven" portion of the clutch would be mounted stationary.
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Re: Brake method needed for hillside lift


I'll check some oline sites for those.  That would be heavier duty than
a bicycle setup. Thanks!
Gemini wrote:
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Re: Brake method needed for hillside lift


Gemini, that may be the best answer.  It appears to be like a
centrifugal brake almost.  I could get a go-cart transmission setup
with the brake partially engaged.  When the speed gets up to the clutch
engage speed it would have brakes applied, assuming the brake pad
didn't slow it down enough for the clutch to disengage causing a
drop-grab-drop-grab effect.

Gemini wrote:
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