Need speed switch for DIY funicular/hillside elevator
astutes...@earthlink.net
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-funicular/
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. I'll take any flames in stride on this point. I realize that
this group is about computer automation, but its the only one similar
to this kind of project I could find :-)
Thanks in advance.
Jeff
Doug
up or down, can you fix a spring loaded brake to the car that is held off by
the tension of the cable?.
Doug
--
<astutes...@earthlink.net> wrote in message
news:1162061065.4...@b28g2000cwb.googlegroups.com...
Frank Olson
I like Doug's idea of the automatic brake. I also think you should put
solid sides on it to keep people from "dangling their legs" through the
railing like I observed in one of the movies. I also think you should
employ some sort of gate, permanently mount the controller and
incorporate a safety switch that would prevent the device from moving
with the gate open.
astutes...@earthlink.net
> I like Doug's idea of the automatic brake. I also think you should put
> solid sides on it to keep people from "dangling their legs" through the
> railing like I observed in one of the movies. I also think you should
> employ some sort of gate, permanently mount the controller and
> incorporate a safety switch that would prevent the device from moving
> with the gate open.
Yes, all good points.
Solid sides, yes. The vid was from the weekend we first got it done.
I plan on finishing it with side pickets such as a deck. I also need
to put the rail back up on the deck with a gate so we can keep small
kiddies or dogs from falling off. I can put a limit switch to prevent
it from running when open on the main deck, but don't really have a
good solution for that on the cart since it is wireless. I think it
will eventually be more of an education thing. The legs dangling
although not prefered was actually not too worrisome at that point
since the front of the cart is 4 feet off the ground. But eventually
the sides would prevent that.
As to the slack, I was originally thinking of something like that, but
with the cable being so heavy, there is actually much slack midway down
in the cable when it is descending, and there will be even more once I
increase the speed of it (variable speed controller). That would work
well in the event of the cable snapped, but that is pretty unlikely
having 2 wires snap at the same time.
In the event of a free spool, there are 2 places I could slow it down.
Either up top at the spool with some kind of cable grapple, or on the
cart assuming a I had a fixed cable running from top to bottom that the
cart straddled and ran through some eyebolt/pulley scenario.
The trick is, how to determine when it is going fast. I almost need
some kind of centrigal device on the cart or at the spool that cuts a
cord or triggers something when it gets going too fast. I don't have
to worry about a a false alarm start surge because the motor controller
ramps up the speed when starting.
Thanks!
Dave Houston
activate if the spool starts turning too fast.
Could you adapt this idea?
http://www.msha.gov/S&HINFO/TECHRPT/HOIST/PAPER5.HTM
astutes...@earthlink.net wrote:
http://www.davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
roZetta-...@yahoogroups.com
astutes...@earthlink.net
Dave Houston wrote:
> If I understand correctly, you want something that will automatically
> activate if the spool starts turning too fast.
>
> Could you adapt this idea?
>
> http://www.msha.gov/S&HINFO/TECHRPT/HOIST/PAPER5.HTM
>
> astutes...@earthlink.net wrote:
>
Dave, yes, that is helpful. It demonstrates many techniques I can use.
Althoug I'm still limited as to how to build a similar system myself,
it should give me some more terms to google to see if there is an off
the shelf solution I may be able to adapt.
I especially liked the rope brake discussions. Although their solution
used compressed air, I could use some kind of spring powered mechanism
(on cart) to clamp down on a fixed cable that runs from top to bottom.
I'm still at a loss though as to how to easily trigger it on the speed,
although obviously a simple solution may be out of my reach.
Thanks for the link!
Jeff
Dave Houston
http://en.wikipedia.org/wiki/Dynamometer
One possibility would be a small air compressor that would be driven by the
spool shaft with a discharge to the atmosphere through a fixed orifice. At
slow speed there would be little resistance but as the speed increases the
resistance increases, slowing the spool. You want to be sure that everything
is sized to be safe - you don't want the compressor or any associated pipes
to burst. You might even let the discharge drive a whistle to warm anyone
nearby.
astutes...@earthlink.net wrote:
astutes...@earthlink.net
Dave Houston wrote:
> Look here also for other general ideas...
>
> http://en.wikipedia.org/wiki/Dynamometer
>
> One possibility would be a small air compressor that would be driven by the
> spool shaft with a discharge to the atmosphere through a fixed orifice. At
> slow speed there would be little resistance but as the speed increases the
> resistance increases, slowing the spool. You want to be sure that everything
> is sized to be safe - you don't want the compressor or any associated pipes
> to burst. You might even let the discharge drive a whistle to warm anyone
> nearby.
Yes, something like that could work.
At the end of the drums is part of the 1.25" diamater shaft that
sticks out. I could increase the torque on it by using 2 different
gears (large one on shaft, smaller on compressor) connected with a
chain to increase the rotational speed.
When going downhill, even if it was in resistance mode, the motor would
overpower the slowdown, but in a freespool situation it could slow it
down as desired.
It would be nice if it was able to only apply torque in one direction
like a bicycle wheel. I wouldn't want it to torque on the trip up, but
just on the trip down. I suppose I could use a bicycle setup for
exactly that purpose, but I think my dad would scoff at the
non-industrial sizing of it, lol.
Robert L Bass
A centrifugal brake should do the job. Ideally, the brake engages as the drum starts spinning fast. As the brake slows the drum, it
eases up a bit, allowing a safe descent. ISTR they used something like this on the tram at a ski lodge in NH.
--
Regards,
Robert L Bass
=============================>
Bass Home Electronics
941-866-1100
4883 Fallcrest Circle
Sarasota · Florida · 34233
http://www.bassburglaralarms.com
=============================>
ABLE_1
Don't know if this has been suggested but here goes.
In your desire to keep this a simple system to control a loss of cable or
drum think about this.
Since it appears that your tram is straight on an incline you could affix a
single cable between the rails from end to end. This would be under your
tram. On the tram bottom have it pass thru a spring loaded clamp apparatus
that would have a pivot lever with a protrusion thru the floor. This
protrusion would have a foot pedal mounted on top. The operation would be
that a passenger would just stand on the pedal which would release the clamp
on the cable thus allowing the tram to move. If a disaster should happen it
would a matter of lifting your foot and the clamp would stop the tram.
Also your drive motor would or should have either a slip clutch or a
overload trip to protect the rest of the system. With all in place you
could use it to help stop and hold at the other positions you have
indicated.
In some applications it is called a Dead Mans Stick or Switch. Such as on a
train or trolley.
It may not work exactly as described above but it may start the seeds to
grow.
Good luck and great job.
Les
<astutes...@earthlink.net> wrote in message
news:1162061065.4...@b28g2000cwb.googlegroups.com...
astutes...@earthlink.net
thought of, the only problem is that the deadman switch wouldn't work
because part of the design is that there is a call button at the top
and bottom to recall the cart in the event it is at the opposite end.
It was also suggested that a mechanism such as this could release when
the cable tension was released, but due to the stiffness of the cable
and how the cable is already somewhat slack when the cart travels down,
it makes it hard to set up the trigger, with the exception of if both
of the "pull" cables broke.
I do think that the fixed cable is about the only way the cart could
have something to "grab" onto similar to the method you describe.
Grabbing the rails would be difficult because the sides are circular
(pipe) and there are angle iron pieces that extend beyond the plum part
of the pipe leaving less than half of the pipe to grab.
What would be nice is if there was a way to have a pulley mechanism on
the cart that spun a cog or something such as a pnuematic pump that the
faster it went it applies more force to say a brake caliper that would
grab the fixed cable, as suggested by Doug earlier.
Thanks!
Jeff
B Fuhrmann
>> If I understand correctly, you want something that will automatically
>> activate if the spool starts turning too fast.
>>
>> Could you adapt this idea?
>>
>> http://www.msha.gov/S&HINFO/TECHRPT/HOIST/PAPER5.HTM
Jeff wrote ...
> Dave, yes, that is helpful. It demonstrates many techniques I can use.
> Althoug I'm still limited as to how to build a similar system myself,
> it should give me some more terms to google to see if there is an off
> the shelf solution I may be able to adapt.
>
> I especially liked the rope brake discussions. Although their solution
> used compressed air, I could use some kind of spring powered mechanism
> (on cart) to clamp down on a fixed cable that runs from top to bottom.
> I'm still at a loss though as to how to easily trigger it on the speed,
> although obviously a simple solution may be out of my reach.
Instead of an air compressor you could use spring loaded brake blocks that
are released by a trigger. If properly designed, a trigger and sear
assembly takes almost no force on the trigger to release the object.
For tripping the trigger, you could use a centrifugal governor design like
the speed regulators on early steam and gas engines
www.physics.montana.edu/demonstrations/video/1_mechanics/demos/centrifugalgovernor.html
http://www.gyroscope.com/d.asp?product=WOODGOV
Have a pulley that is driven by the cable spin the governor and you can have
the weights hit the trigger to clamp the brakes on.
Since you intend this system to be used rarely and only in an emergency,
simpler is likely to be more reliable.
I expect that most of it's use will be in testing that it works reliably.
If you choose your brake materials well and adjust the clamping force, you
can walk the line between stopping so fast that the people on board are
injured from the impact and being so slow that they don't stop.
If you want to get fancier, you could use the regulator in it's original
method to adjust a control lever that controls the braking force.
"Robert L Bass" wrote ...
> A centrifugal brake should do the job. Ideally, the brake engages as the
drum starts spinning fast. As the brake slows the drum, it
> eases up a bit, allowing a safe descent. ISTR they used something like
> this on the tram at a ski lodge in NH.
You might be able to do this inexpensively by using centrifugal clutch from
a go cart. Instead of connecting between the drive and driven system, you
could connect it to the cable (requires a good grip between the pulley and
the cable) and a resistance element. As the clutch spins, it locks up and
the resistance element comes into effect.
The advantage of this would be that the car would never come to a stop and
would return people to the bottom of the hill.
The disadvantage is that it could be difficult to adjust this system to
limit the speed so that the car is moving slow enough when it gets to the
bottom.
---
Based on this being rarely used safety device. I like the idea of simple,
even if it requires that people get off part way up the hill.
Bill Fuhrmann
--
Bill Fuhrmann
astutes...@earthlink.net
> > A centrifugal brake should do the job. Ideally, the brake engages as the
> drum starts spinning fast. As the brake slows the drum, it
> > eases up a bit, allowing a safe descent. ISTR they used something like
> > this on the tram at a ski lodge in NH.
>
> You might be able to do this inexpensively by using centrifugal clutch from
> a go cart. Instead of connecting between the drive and driven system, you
> could connect it to the cable (requires a good grip between the pulley and
> the cable) and a resistance element. As the clutch spins, it locks up and
> the resistance element comes into effect.
> The advantage of this would be that the car would never come to a stop and
> would return people to the bottom of the hill.
> The disadvantage is that it could be difficult to adjust this system to
> limit the speed so that the car is moving slow enough when it gets to the
> bottom.
>
> ---
>
> Based on this being rarely used safety device. I like the idea of simple,
> even if it requires that people get off part way up the hill.
>
> Bill Fuhrmann
>
Yes, something like this might work. The spring/lock cable grap could
be held in the open mode almost like a mousetrap with a little force
that is easily triggered provided it could be done so that no jostling
or sharp inpact would force it to snap.
Another thought along a similar lines is to have two brake pads pushing
on the cable with a spring applying the force (like an emergency brake
on car?). A fulcrum weight could hold the tension off of the spring
keeping open and something like that centrifugal governor could lift up
on the weight at higher speeds. Cool. Thanks!
Dave Houston
>It would be nice if it was able to only apply torque in one direction
>like a bicycle wheel. I wouldn't want it to torque on the trip up, but
>just on the trip down. I suppose I could use a bicycle setup for
>exactly that purpose, but I think my dad would scoff at the
>non-industrial sizing of it, lol.
I think what you want is something which loads the shaft in proprtion to the
speed so that at normal climbing speed there would be minimal load while at
the higher speed of a runaway, it would create a maximum load, slowing the
descent. It may prove that an air compressor is inadequate but I think you
understand the general idea.
I do not like any of the friction-based suggestions. I think they present
maintenance problems and will, themselves, be prone to catastrophic failure.
You want something that requires little maintenance and is fundamentally
failsafe.
Also, I don't like anything that's passenger operated since it might carry
someone unfamiliar with its operation.
I really have no idea how big an electric motor needs to be to act as a
brake when it is generating electricity into a resistive load (as shown in
the first link I cited) but, individual motors on the wheels of the tramcar
might be another possibility.
BTW, I can just remember (actually, these days it's more a matter of
remembering remembering) when the Mount Adams Incline still operated in
Cincinnati. It was a little larger than your funicular, being designed to
carry streetcars. There were 4-5 funiculars in Cincinnati. The bottom of the
last link, below, has links to photos of the others.
http://en.wikipedia.org/wiki/Mount_Adams_Incline
http://www.cincinnati-transit.net/incline-mtadams.html
http://www.cincinnati-transit.net/incline-mtadams2.html
http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
roZetta-...@yahoogroups.com
ABLE_1
It does get a bit challenging does it not. Diverting from the simple a bit
you could consider this.
Since you have already made the wireless for control of the unit could you
then incorporate a solenoid on the deadman switch that would override the
foot pedal for a one-time trip. This could be set up in relay logic that
would respond off a momentary push button at either end. Once the tram
reached its new position it would trip a limit switch and return all
functions to normal. It would require that some power on the tram but this
could be accomplished with a battery with some indicator when the battery
gets low.
I can see some problems since this will not be 100% fool proof. (or idiot
proof as some would say) but you can do some rigorous training of family an
friends since this is not for public use.
Good luck,
Les
<astutes...@earthlink.net> wrote in message
news:1162098544.8...@h48g2000cwc.googlegroups.com...
Frank Olson
What you really need is a "third rail". You could then install a set of
brake calipers on the cart to act as an emergency stop.
astutes...@earthlink.net
Dave Houston wrote:
> I think what you want is something which loads the shaft in proprtion to the
> speed so that at normal climbing speed there would be minimal load while at
> the higher speed of a runaway, it would create a maximum load, slowing the
> descent. It may prove that an air compressor is inadequate but I think you
> understand the general idea.
>
> I do not like any of the friction-based suggestions. I think they present
> maintenance problems and will, themselves, be prone to catastrophic failure.
> You want something that requires little maintenance and is fundamentally
> failsafe.
Although I think the speed governor with a brake pad on a fixed cable
would be the better solution in terms of noise and reliability, it
would be harder to implement than a direct drive to an air compressor.
But the AC would be noisy (pap-pap-pap-hssss). Either would require
periodic maintenance I suppose.
>
> Also, I don't like anything that's passenger operated since it might carry
> someone unfamiliar with its operation.
>
Agreed.
> I really have no idea how big an electric motor needs to be to act as a
> brake when it is generating electricity into a resistive load (as shown in
> the first link I cited) but, individual motors on the wheels of the tramcar
> might be another possibility.
That would require a battery to energize the stator (I think) and I
don't want to have any electronics (other than the remote) on the cart.
Besides, those wheels took me the whole weekend to get right, I don't
want to touch them again if I can help it, lol.
Les wrote:
> Jeff,
>
> It does get a bit challenging does it not. Diverting from the simple a bit
> you could consider this.
>
> Since you have already made the wireless for control of the unit could you
> then incorporate a solenoid on the deadman switch that would override the
> foot pedal for a one-time trip. This could be set up in relay logic that
> would respond off a momentary push button at either end. Once the tram
> reached its new position it would trip a limit switch and return all
> functions to normal. It would require that some power on the tram but this
> could be accomplished with a battery with some indicator when the battery
> gets low.
Yes, that is a bit more complex. I would have to have a battery on
there and keep it charged which would pose its own problems for
maintenance.
One whimsical solution, perhaps I should have a parachute pull a cotter
pin, lol. If I could count on the wind not pulling it on a windy day.
astutes...@earthlink.net
Frank Olson wrote:
>
> What you really need is a "third rail". You could then install a set of
> brake calipers on the cart to act as an emergency stop.
Yes, this is sort of what we were talking about with a fixed center
cable. The trick is how to get the brake caliper to determine when to
grab
Dave Houston
>> I really have no idea how big an electric motor needs to be to act as a
>> brake when it is generating electricity into a resistive load (as shown in
>> the first link I cited) but, individual motors on the wheels of the tramcar
>> might be another possibility.
>
>That would require a battery to energize the stator (I think) and I
>don't want to have any electronics (other than the remote) on the cart.
> Besides, those wheels took me the whole weekend to get right, I don't
>want to touch them again if I can help it, lol.
I don't think so. A permanent magnet DC motor will act like a generator when
driven. The question is what size is needed.
Dave Houston
>One whimsical solution, perhaps I should have a parachute pull a cotter
>pin, lol. If I could count on the wind not pulling it on a windy day.
Bungeeeeeee!
Marc_F_Hult
On 28 Oct 2006 11:44:25 -0700, astutes...@earthlink.net wrote in message
<1162061065.4...@b28g2000cwb.googlegroups.com>:
>I am thinking of having some way of measuring the outfeed speed of the
On 28 Oct 2006 12:42:24 -0700, astutes...@earthlink.net wrote in message
<1162064544.7...@f16g2000cwb.googlegroups.com>:
>The trick is, how to determine when it is going fast. I almost need
>some kind of centrigal device on the cart or at the spool
On 28 Oct 2006 13:55:15 -0700, astutes...@earthlink.net wrote in message
<1162068915....@e3g2000cwe.googlegroups.com>:
>I'm still at a loss though as to how to easily trigger it on the speed,
>although obviously a simple solution may be out of my reach.
As far as I can tell, you didn't get an answer to the question you raised
above despite all the posts ....
It would be straight-forward to make a sensor that would determine the
rotational speed of the cable capstan(s) and provide a safe/not-safe (go/
no-go) signal.
One way would be with one or more small magnets attached to the rim of the
capstan, a hall-effect sensor that would sense the magnet and produce a pulse
every time a magnet passed by, a frequency-to-voltage converter which might
be a single IC like http://cache.national.com/ds/LM/LM2907.pdf or a charge
pump made from a cheap op amp http://cache.national.com/ds/LM/LM324.pdf and
a capacitor-resistor network , and a simple comparator
http://cache.national.com/ds/LM/LM339.pdf (or an op-amp used as a comparator)
to compare the measured voltage with a threshold set with a potentiometer or
resistance divider. This c/would cost less than $10 to make with parts from
Radio Shack. Sounds more complicated than it is.
What you do with the go/no-go signal would be a 'nuther matter.
HTH ... Marc
Marc_F_Hult
www.ECOntrol.org
B Fuhrmann
> remembering remembering) when the Mount Adams Incline still operated in
> Cincinnati. It was a little larger than your funicular, being designed to
> carry streetcars. There were 4-5 funiculars in Cincinnati. The bottom of
> the
> last link, below, has links to photos of the others.
Here are links to the two operating inclines in Pittsburgh.
http://en.wikipedia.org/wiki/Duquesne_Incline
http://en.wikipedia.org/wiki/Monongahela_Incline
You can probably find more pictures by searching on "Monongahela Incline" or
"Duquesne Incline" outside of wikipedia.
I have ridden on the Duquesne Incline and it is a fun ride. It operates
both as a tourist ride and part of the transit system.
Pittsburgh needed them because it is in the top of the Y where the
Monongahela and the Allegheny rivers join. There are two tall bluffs on the
outsides of the Y which makes it almost impossible to get to the city from
the sides or bottom unless you use in incline or a tunnel.
--
Bill Fuhrmann
B Fuhrmann
> Yes, something like this might work. The spring/lock cable grap could
> be held in the open mode almost like a mousetrap with a little force
> that is easily triggered provided it could be done so that no jostling
> or sharp inpact would force it to snap.
>
> Another thought along a similar lines is to have two brake pads pushing
> on the cable with a spring applying the force (like an emergency brake
> on car?). A fulcrum weight could hold the tension off of the spring
> keeping open and something like that centrifugal governor could lift up
> on the weight at higher speeds. Cool. Thanks!
The problem with the second solution is that a mechanical failure causes the
brake to release.
There is a chance of this with version 1 but fewer.
A second item that should be considered is that a fault should shut off the
drive motor and not allow it to be restarted by the standard controls at the
ends. This is similar to automated machinery controls.
Since you have controls at each end, there should be wires in the circuit
that can be opened to shut down the system.
The mousetrap (I like that analogy better) opens the circuit until it is
mechanically reset.
Your control switches should be wired so that they have to be pressed AFTER
the mouse trap is reset before the car can move again.
DO NOT reset the mouse trap until after the cable is back on the capstan
and/or have a way to lock out the power to the circuits at the capstan end.
If this was an industrial control, the lock out would be mandatory. At home
it depends on where the mouse trap is and how safe you want to be. I
recommend having it.
Another part of the circuit should be a timer that shuts off the system if
the motor is running past the time the car should be at the other end. This
will shut down the system if the cable comes loose at a time when anything
prevents the car from making the trip or a limit switch at the end fails.
This control should also not be overridden by the normal start buttons.
Bill Fuhrmann
Marc_F_Hult
wrote in message <mj9ak21mn3jsgvqiv...@4ax.com>:
I looked at your pictures from which it seems that the diameter of the spool
of the remaining cables would vary significantly with amount of cable played
out. So to keep the signal linear with respect to revolutions per minute, one
could mount the magnet(s)on idler pulley(s).
... Marc
Marc_F_Hult
www.ECOntrol.org
ABLE_1
maintain some functionality in life. Well then it hit me. Why re-invent
the wheel. Since these funiculars have been in operation all over the world
for quite some time, I thought that it would be good to look at what the big
guys are doing. My hope is that Jeff has already looked into this at some
point in time. It might prove beneficial if some of the companies were
contacted to get some input of what safety system they use on their
equipment.
This link is for a number of manufactures
http://www.funimag.com/Funimag-Manufacturers.htm
And this one talks about there safety features
http://www.accumar.com/safety.html
Again Good Luck,
Les
<astutes...@earthlink.net> wrote in message
news:1162061065.4...@b28g2000cwb.googlegroups.com...
Robert L Bass
> all over the world for quite some time, I thought
I had the same thought but about smaller operations I've seen. Most here know that I have a second home in Brazil. In our city
there is a wealthy neighborhood with deluxe condos overlooking the Bahia do Todos os Santos (Bay of All Saints). The condos are all
situated on a high bluff, some 30 meters above the bay. Most have funiculars or trams for the residents to get down to their yachts
(it's the nicest part of town:)).
When I go back next February we will be visiting family in the area. I'll find an opportunity to take some pictures if I can. Even
if the OP's project is done by then it might be interesting to see what (if any) safety measures have been implemented.
ABLE_1
"Robert L Bass" <rober...@comcast.net> wrote in message
news:eoKdnSVUHe4p1NjY...@comcast.com...
astutes...@earthlink.net
them yet.
Les, yes, I tried to check, even looked at some of the others that sold
kits for hillside lifts and they only wanted to sell the whole package,
not their speed regulators.
Bill has a good point about shutting the system down if the "mousetrap"
is triggered. This is very possible because there is an emergency
cutoff switch near the spool (not shown, recently added) and if that
circuit is opened, the whole system shuts down. A jumper in series
with the switch could shut it down if pulled.
Someone on another board made an interesting suggestion. He mentioned
a go cart clutch. When I looked into it, the go cart clutch (GCC)
activates when the rotational speed gets up using a centrifugal setup.
See: http://www.gokartsupply.com/clutches.htm
So here's what I'm thinking. On the end of the spool, have a large
sprocket that drives a chain to a smaller sprocket. The smaller
sprocket is hooked up to a go cart transmission (centrifugal clutch)
that is underneath the drum units. The gearing would mulitply the
spin. At high speed rotation, the clutch engages and the wheel turns
and yanks the mousetrap and pulls out a jumper that opens the emergency
stop button (motor shutoff). Then it would take a manual reset to
unlock, but if its spinning freely something major is wrong such as a
broken coupling or a broken shaft inside the gearbox.
Dave Houston
simple safety mechanism in the event that the spools break loose from the
concern.
I'm confused. I thought it was "something major is wrong such as a
broken coupling or a broken shaft inside the gearbox" that was the primary
concern.
astutes...@earthlink.net wrote:
>So here's what I'm thinking. On the end of the spool, have a large
>sprocket that drives a chain to a smaller sprocket. The smaller
>sprocket is hooked up to a go cart transmission (centrifugal clutch)
>that is underneath the drum units. The gearing would mulitply the
>spin. At high speed rotation, the clutch engages and the wheel turns
>and yanks the mousetrap and pulls out a jumper that opens the emergency
>stop button (motor shutoff). Then it would take a manual reset to
>unlock, but if its spinning freely something major is wrong such as a
>broken coupling or a broken shaft inside the gearbox.
Nick Hull
astutes...@earthlink.net wrote:
> Les, thanks. The fixed cable with a spring clamp is something I
> thought of, the only problem is that the deadman switch wouldn't work
> because part of the design is that there is a call button at the top
> and bottom to recall the cart in the event it is at the opposite end.
The spring clamp would work fine, as long as you lock it open when you
leave the cart. You don't need much of a safety when the cart is empty,
only when people are inside, and then it would be a 'deadman' clamp.
--
Free men own guns - www.geocities/CapitolHill/5357/
Nick Hull
astutes...@earthlink.net 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.
astutes...@earthlink.net
condition is a minor concern, but I'm sure its possible may have
implied that by accident. I quickly scanned earlier posts and missed
it. If its the quoted text below I must be missing it. In any event
here is what I probably meant: The system itself is way oversized for
what it does. I think the likelihood of a freespool condition is
minor, but its the one remaining possibility that could result in the
cart running out of control, so in that sense its the major concern.
If one drum breaks off, the other will hold. If one cable brakes, the
other cable will hold. If the coupling breaks or the gear shaft goes,
it could freespool and turn the cart into a poorly designed
rollercoaster. Sorry for the confusion.
astutes...@earthlink.net
>
> 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!
astutes...@earthlink.net
That would work, but I would have to depend on my kids to set the clamp
when they get off and hope they remember to unset it when they get on.
I would be afraid that it would get set open and not thought about, or
even worse, locked at the bottom (brake on) and someone at top hits the
recall button and has the cart connection point ripped out. Or on the
opposite situation where its locked at the top and the cart is called
down and the cable unspools up top.
astutes...@earthlink.net
astutes...@earthlink.net wrote:
> So here's what I'm thinking. On the end of the spool, have a large
> sprocket that drives a chain to a smaller sprocket. The smaller
> sprocket is hooked up to a go cart transmission (centrifugal clutch)
> that is underneath the drum units. The gearing would mulitply the
> spin. At high speed rotation, the clutch engages and the wheel turns
> and yanks the mousetrap and pulls out a jumper that opens the emergency
> stop button (motor shutoff). Then it would take a manual reset to
> unlock, but if its spinning freely something major is wrong such as a
> broken coupling or a broken shaft inside the gearbox.
>
Researching this I'm not sure it would work. Most of those clutches
activate at around 3500 RPM, and by my calculations the drums are
moving at 23 rpm (2 minute trip for 142 feet on a 12 inch drum) and
perhaps as fast as 30-50 RPM when I increase the VFD motor speed. The
largest gear I can find has 112 teeth, and the clutch has 10 (drum
clutch ration of 11.2) That would give me a max "regular" RPM of 560
RPM on the clutch. By the time the thing got up to full speed it would
be going too fast.
Additional gears could be added to multiply this, but I'm wondering if
it would put too much torque on the gear to increase the drum/clutch
ratio to 60, but I don't know gears that well.
Doug
against" the cable that will hold the brakes off, it doesn't matter if the
cable is sagging in the middle, its still holding the car and the brakes
will be held off.
It could be as simple as the cable passing through a correctly rated coil
spring at the car and attached to a lever that will hold off the brake, when
the cable is attached to the spools and the spools are winding or unwinding
normally the weight of the car will compress the spring and release the
brake, if the spools are unwinding uncontrollably or the cable is broken
then there will be nothing for the car to "pull against" and the spring
would expand and the brakes will no longer be held off.
Doug
<astutes...@earthlink.net> wrote in message
news:1162217574.7...@f16g2000cwb.googlegroups.com...
Frank Olson
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.
astutes...@earthlink.net
>
> 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.
A little background first: Each cable attaches to a cable eyelet that
attaches to a large U-bolt on the respective side near the low side of
the cart. On that there is an individual 6 foot stretch of cable that
connects near the uphill side of each cable and is joined by 2 pulleys
that are connected to the lowside U-bolts mentioned. They "eyelet"
portion of the cable is slack (by about 6") in between the where the
pulley cable connects. This allows the tension to be spread evenly,
and by keeping the eyelets there, they act as a buffer if one of the
cables break. Before, I didn't have the pulley section and the cable
tension varied, and it was difficult to adjust. Adding the 6 foot
section distributed the load.
So, for both cables there is a common tension point which is anywhere
along that pulley'd section. I suppose I could add a spring oriented
solution that applied pressure to a brake caliper (go karts have these)
to a fixed cable. Initially there wouldn't be much friction to slow
the cart down, but as the cart did start to slow and removed tension
from the main cables, the spring would be more dominant and would apply
full force to it. Even if it doesn't stop it but slows that might be
sufficient. And I could always add more calipers like this:
http://www.mfgsupply.com/m/c/218070A.html?id=m6EMrXok
I would just need to play with how much tension actually would be
needed to trigger it. Hmm.... something to think about.
Bra
they'd be much better off in the long run if they just walked up and
down the hill. then you could spend your time on something important.
Dave Houston
raise/lower the tram. I'm sure the manufacturers have seen similar
applications and have addressed the safety aspects. In any event, it should
be much easier to slow and stop the rotating drum of the winch than it will
be to design and maintain any of the Goldbergian suggestions you've gotten
here.
http://www.torkwinch.com/index-2.html
Robert L Bass
> raise/lower the tram.
That's not a solution. If the cable breaks the tram will still come down fast.
I'm sure the manufacturers have seen similar
> applications and have addressed the safety aspects. In any event, it should
> be much easier to slow and stop the rotating drum of the winch than it will
> be to design and maintain any of the Goldbergian suggestions you've gotten
> here.
Demeaning the efforts of others doesn't make your suggestion more useful.
ABLE_1
astutes...@earthlink.net
The current set up is SOOO much better than a motorized winch. I
haven't gone into much detail about it, but is being driven by a 5 HP 3
phase VFD (variable frequency drive). It is driven by a $1,500 motor
controller that is programmable to vary the ramp up and ramp down
speeds as well as taking switch (wired and remote) inputs to trigger
events. The whole setup was designed for over 5,000 lbs (with the
exception of the rails and cart) and should never have a failure event,
but I'm not so naive to assume it would never happen.
We are just trying to eliminate all possible forseen sources of
failure, and the most catastrophic I can think of besides the cart
falling over is a main shaft break causing a freespool. The drums are
secured with 3 bearings on solid steel pillow blocks, so I don't think
if the shaft breaks the drums would fall off. Of course another source
of failure would be a cable break, so we had 2 setup instead of just
one.
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.
G. Morgan
<royboy...@somewhere.net> wrote:
> Excuse me??? I resemble that remark!!!
Sit there and rotate, you winch!
--
-Graham
(remove the double e's to email)
rhamer
I hve found reading this thread most enjoyable and commend you on your
work to date.
I am slightly confused as to what particular problem you are trying to
solve, although I guess it all falls under the general heading of
"Saving your passengers from running out of control down the hill"
I think you have to decide where the reasonable points of failure are
and accept that other potential points are ruled out due to good
design. This will then determine where and how you need to provide the
appropriate braking mechanism.
Already you have decided that a single cable is an unacceptable single
point of failure and so you have duplicated it. Given that each cable
is rated at many times the actual load I would consider that 2
simultaneously broken cables to be such a small possibility that it
could be safely ignored (however I have not seen such things as the
attachment points at top & cart). Consider the chairlift as an example
of a single cable design.
From what I have read here so far, I would think that your major area
of concern is in motor or the coupling between the motor & drums. I’m
also assuming that the anchoring of the motor & drums is designed to be
solid under any sort of reasonable conditions, much like you don’t think
your whole house is going to slide down the hill, because it has been
designed no to, so doing the same with the motor would not be too much
of an engineering challenge.
So in my opinion the part you are lacking is the over speed detection
and braking of the drums.
I would consider solving the problem by having a third outboard disk or
drum (like a car disk or drum brake) that has shoes that are held off
electrically (either directly or indirectly via hydraulics) I would
then pulse count the rotation of the drum to calculate the speed and in
the event of over speed set the brakes. Correct operation of the pulse
counting could be verified during the first couple of seconds of
operation otherwise the brakes should be applied. You could probably
source most of the bits using the anti locking brake system off a car.
I would also provide some form of dampening on the cable, probably in
the form of a small car coil spring, rigged up in line, with the cable
ends passing through it so it is working in compression. This will stop
the cable from potentially whipping should the braking be a bit sudden.
Anyway, just my thoughts.
Cheers
Rohan
--
rhamer
'HAMFIELD' (http://www.hamfield.com.au)
Industry Supplier of Automation Solutions
for the Home and Small Business.
Authorised 'CQC' (http://www.charmedquark.com) Integrator Partner.
Robert L Bass
uphill side of the tram. The arm would need a hydraulic or spring-loaded strut to draw it up toward the tram. Slack feeding out
beneath the tram goes up over the pulley.
The arm mechanically holds open a brake as long as it is stretched down, where it will always remain if there is tension on the
cable. If the cable breaks the arm swings up, activating the brake. The can either be on a third cable or on the wheels. A cable
brake should be easier to implement than wheel brakes, but the end result is the same.
The advantage to Doug's idea (as I perceive it) is that it is simple, requires no electronics and should be easy to maintain. Trial
and error should quickly yield the amount of tension required to operate the arm and the brake.
Note about safety factors. When "flying" live actors or moving loads above a stage, I would select equipment rated to hold 10 times
the static weight of the load. This would allow me enough margin of safety to stop a load even as it gained momentum before
reaching the end of the safety cable. On a slope the load doesn't gain momentum as quickly as on a deadfall. However, depending on
how quickly your safety system detects a failure and engages and the slope of the rails, the tram could accelerate, perhaps to the
point of failure of the emergency braking system. Not knowing the weight of the tram, number of people who will be riding at one
time, slope of the hill, etc., I can't say how strong is strong enough. It sounds as though you've given this careful
consideration, but double-checking your calculations is never a bad idea.
Dave Houston
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.
astutes...@earthlink.net 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.
astutes...@earthlink.net
the situation. What you speak of would be a good solution if there was
an easy way to determine the overspeed condition without any expensive
electronics or hydraulics.
The dampening of the cable is something I hadn't considered, but is a
potential risk. I'm hoping that since there aren't extreme loads on
the cables (500 lbs per cable at 30 degrees) that the whiplash effect
would be minimized, but I could be wrong.
Thanks!
Jeff
astutes...@earthlink.net
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.
astutes...@earthlink.net
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
>Consider the chairlift as an example of a single cable design.
And consider that most funiculars have dual trams connected to each other by
a single cable that passes through a pulley (capstan) at the top end of the
ramp. As one tram climbs, the other descends. The weight of the riders is
probably minimal compared to the weight of the trams so the design is
inherently safe with the weight of the ascending tram limiting the velocity
of the descending tram.
Jon Woellhaf
the top of the ramp unrestrained?
astutes...@earthlink.net
is set at half speed. When I get more time (its not my fulltime
residence have to travel 5 hours to work on it) I want to crank up the
speed to near full speed which should be a little over 2 ft/sec. The
trick is that I have to adjust the start and stop microswitches to keep
it from crashing to the bottom or the top with the increased speed.
So, I would assume 3 ft/sec would be considered the "out of control"
condition. Since the drum is 12" diameter (3.14 circumference) that
would be about 60 rpm.
Dave Houston
>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
Well, given that you now want something to paste on to your design, add a
heavy flywheel to the drum.
astutes...@earthlink.net
Problem with that is that it would increase the coast time of the cart
going down. Currently its about 3 feet when the "normal stop" command
is sent.
But something on a similar vain that could work is something with a
constant drag like the air compressor idea that was suggested, or even
a squirrel cage fan underneath the drums if geared with a bicycle
chain. The motor could overpower the additional going down
Robert L Bass
<astutes...@earthlink.net> wrote in message news:1162305387.6...@b28g2000cwb.googlegroups.com...
> 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.
astutes...@earthlink.net
Robert L Bass wrote:
>
> 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.
>
Robert, what you said about Doug's idea makes complete sense. I was
initially thinking of something like this pre-construction, but the
cable rigidity discouraged the concept. But That was when I was
thinking of assuming there would be total loss of tension and gravity
would "flip the switch" so to speak.
To describe the way the cable is mounted, imagine the floor lifted off
as you are on the cart facing down hill. You would see a cable under
your left foot going to the down hill corner, to a pulley, then over to
the side pulley on the right and then back under your right foot. So
in a sense, the cable makes a large "U" (upside down that is). If I
were to add a center pulley such that it made a "W" attached to a
spring, I could as you and Doug say, use springs and the cart's weight
to adjust to the condition of freespool or just normal use such that a
small loss in tension could grab onto the cable.
Another benefit to it is that I could use this method to hold the cart
in place as I work on it, although I would probably count on a little
more than just the grapple.
The trick will be to come up with a method to grab the wire. I've
thought of an eyebolt with a spring (like a valve spring) to grab it in
sheer, or perhaps a rod with two pins that torques and binds the cable.
I think the best would be a go kart brake. They are mechanical (non
hydraulic) and have a lever built in. I would probably need to wear a
groove in the pads to increase the surface area.
Robert L Bass
--
Regards,
Robert L Bass
=============================>
Bass Home Electronics
941-866-1100
4883 Fallcrest Circle
Sarasota · Florida · 34233
http://www.bassburglaralarms.com
=============================>
> The trick will be to come up with a method to grab the wire. I've
Jon Woellhaf
<astutes...@earthlink.net> wrote in message
news:1162311550.0...@f16g2000cwb.googlegroups.com...
astutes...@earthlink.net
you mean by terminal velocity the maximum speed it would reach on a
runaway condition, I don't have a clue.
Jon Woellhaf
news:1162403122.4...@e3g2000cwe.googlegroups.com...
> No, that would be the speed at which I would assume its a runaway. If
> you mean by terminal velocity the maximum speed it would reach on a
> runaway condition, I don't have a clue.
Yes, I mean the maximum speed during a runaway condition -- like if both
cables failed.
I believe you said the vertical distance is 70 feet. That means the maximum
speed the cart could reach is 46 mph, discounting rolling friction and air
resistance -- if I remember my freshman physics correctly. Accounting for
rolling friction and air resistance, I estimate the terminal speed would be
no more than 40 mph.
That's probably too fast for my initial idea of a passive emergency
deceleration system to work. I was thinking of a net across the bottom of
the track held by bungee cords attached to posts or trees.
I think an engineer could design a water filled coaxial tube shock absorber
that would safely decelerate a runaway cart. You'd have to add track beyond
the normal lower platform. It looks like there's room.
A simpler solution is to add track all the way to the water with a level or
slightly inclined runout portion and just let the runaway cart and occupants
get launched into the lake. <g>
Really cool device, by the way.
Jon
