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By Evan Sanders
From Westminster, CO
Feb 26, 2013
Flaming Pumpkin

I'm looking for a little bit of help on a design I've been working on. No this is not some senior project or whatever, it's something I've been working on for about 4 months for my own personal benefit.

The design is for a lead climbing auto belay device for climbing gyms. I've got the design and even began putting together a prototype (not nearly done yet), but I'm struggling with the braking system.

So the idea is to use a hydraulic braking system similar to what a car has with disc brakes (I'm actually going to use one for my prototype if I can figure things out). My question is would it be possible to control the force of that hydraulic brake based upon a max set rpm? So if you can visualize a rope wrapped around a cylinder with a disc brake, the rope would be able to uncoil with no resistance while the climber was on the wall. However if the climber were to fall, as soon as the cylinder was uncoiling at, say, 45 rpm (I don't actually know if this is the exact rpm, but imagine it's correct), the system would brake just enough to where the speed of rotation would continue to be 45 rpm no matter how much force was trying to uncoil the rope. The braking system needs to be variable though because of the difference in climbers' weights, and possibly for pumped climbers trying to clip really quickly. I've already obtained a sensor for the prototype, it's one of the same sensors we use at my work for high speed fatigue testing.

So any thoughts? A hydraulic system may not work as it might take up too much space, but I don't know that's why I'm asking.


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By frankstoneline
Feb 26, 2013



I think this is what you're looking for.


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By Evan Sanders
From Westminster, CO
Feb 26, 2013
Flaming Pumpkin

frankstoneline wrote:
I think this is what you're looking for.


These are not the droids I'm looking for.


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By Tony B
From Around Boulder, CO
Feb 26, 2013
Got Milk? How about forearm pump? Tony leads "Alan Nelson's Bulging Belly" (5.10, X) on the Lost and Found Flatiron. Belayer is Mark Ruocco. Photo by Bill Wright, 10/06.

The force of a damper will be proportional to the velocity.
en.wikipedia.org/wiki/Damping

You would/could use the equivalent of a rotational dashpot.
You'd need a secondary system that is fail-safe at a higher volocity, IE a hardstop throwout mechanism that would overcome a spring @ RPM > X.


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By frankstoneline
Feb 26, 2013

Seems like you'd want it to do 2 things, first catch, then lower. if the lower is controlled by a remote, all it has to do is lock in a fashion that doesnt smash the climbers ankles. seems like you could use some algorithm to define an increase of pressure between pads and rotors to "soften" the catch. then once the rotor is locked the climber could hit a button and you would have a second algorithm in which the pad relaxed off the rotor until a certain rpm was achieved and then maintained.

note: I'm no engineer (that was probably obvious)


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By jake 356
From worcester
Feb 26, 2013

Hydraulic centrifical clutch? Used on some machines, not sure if you would develop high enough speeds to engage though.


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By Tony B
From Around Boulder, CO
Feb 26, 2013
Got Milk? How about forearm pump? Tony leads "Alan Nelson's Bulging Belly" (5.10, X) on the Lost and Found Flatiron. Belayer is Mark Ruocco. Photo by Bill Wright, 10/06.

jake 356 wrote:
Hydraulic centrifical clutch? Used on some machines, not sure if you would develop high enough speeds to engage though.

Gear it down... then the flywheel gets high revs.
Basically an elevator drum.

With a viscous fluid damper though, on the OD edge, you'd get F/T ~bV^2, so your speed would be nearly the same for various climber weights and top out at a modest speed.

I would wager that is how existing systems work.


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By 20 kN
From Hawaii
Feb 26, 2013

Evan Sanders wrote:
I'm looking for a little bit of help on a design I've been working on. No this is not some senior project or whatever, it's something I've been working on for about 4 months for my own personal benefit. The design is for a lead climbing auto belay device for climbing gyms. I've got the design and even began putting together a prototype (not nearly done yet), but I'm struggling with the braking system. So the idea is to use a hydraulic braking system similar to what a car has with disc brakes (I'm actually going to use one for my prototype if I can figure things out). My question is would it be possible to control the force of that hydraulic brake based upon a max set rpm? So if you can visualize a rope wrapped around a cylinder with a disc brake, the rope would be able to uncoil with no resistance while the climber was on the wall. However if the climber were to fall, as soon as the cylinder was uncoiling at, say, 45 rpm (I don't actually know if this is the exact rpm, but imagine it's correct), the system would brake just enough to where the speed of rotation would continue to be 45 rpm no matter how much force was trying to uncoil the rope. The braking system needs to be variable though because of the difference in climbers' weights, and possibly for pumped climbers trying to clip really quickly. I've already obtained a sensor for the prototype, it's one of the same sensors we use at my work for high speed fatigue testing. So any thoughts? A hydraulic system may not work as it might take up too much space, but I don't know that's why I'm asking.

You could try a centrifugal clutch. The Silent Partner uses one, and that it is designed to provide the function you are seeking. I like Tony B's idea.


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By jake 356
From worcester
Feb 26, 2013

Tony- haha ya forgot about that. Good call


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By Evan Sanders
From Westminster, CO
Feb 26, 2013
Flaming Pumpkin

Tony B wrote:
Gear it down... then the flywheel gets high revs. Basically an elevator drum. With a viscous fluid damper though, on the OD edge, you'd get F/T ~bV^2, so your speed would be nearly the same for various climber weights and top out at a modest speed. I would wager that is how existing systems work.


Good call. Way more convenient than what I was thinking.

I'd probably just have a small motor to run it in reverse once the climb is completed. With a centrifugal clutch though set to "X" rpms, which would obviously pretty slow, I would wonder if it would force the rewinding of the rope to be the same speed.


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By Jim Titt
From Germany
Feb 26, 2013

I started my career as a hydraulic designer and use a fair amount daily. Give anything hydraulic a few weeks in the chalk dust of a climbing wall and it will look like a donut at best and more likely resemble a creature from the slime lagoon.


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By Tony B
From Around Boulder, CO
Feb 26, 2013
Got Milk? How about forearm pump? Tony leads "Alan Nelson's Bulging Belly" (5.10, X) on the Lost and Found Flatiron. Belayer is Mark Ruocco. Photo by Bill Wright, 10/06.

Jim Titt wrote:
I started my career as a hydraulic designer and use a fair amount daily. Give anything hydraulic a few weeks in the chalk dust of a climbing wall and it will look like a donut at best and more likely resemble a creature from the slime lagoon.

Depends on how you design and seal it.
Disk drive motors are all fluid bearings and spin continuously at 5400-15000 RPM for 5+ years.


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By trr2ke
From Cookeville, Tennessee
Feb 26, 2013

Like others said, I would do: gear reduction to lower your torque/flywheel for dampening/centrifugal breaking on the flywheel.


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By Crag Dweller
From New York, NY
Feb 26, 2013
My navigator keeps me from getting lost

It's been a long time since I've put any thought into engineering equations but...

Have you considered an air brake? Picture a spinning wheel with blades on it. Housed blades for safety, of course.

As the speed increases, so does wind resistance. You could even get fancy and design it so that as speed increases, the force is used extend the braking blades further to create more resistance.

Not the direction you're headed but maybe that thought will spark some ideas....


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By doak
From boulder, co
Feb 26, 2013
Drinking with Moses

Interesting idea. Few thoughts:

1)I'm assuming that it would be mounted on the ground, it would need to be low profile and padded so you didn't mess yourself up if you landed on it.

2)Would the climber need to change their clipping style, or do you have an idea for feeding out slack? Seems like it would be a real challenge to avoid short roping the climber. The alternative is to set the routes so that it's natural to clip at your waist.

3)The lower part of routes is always the most demanding on the belayer, but higher up the belayer can keep a bit of slack in the system.

4)On an auto-belay, the reel tension is pulling up on a climber. For a lead auto-belay, the reel tension is pulling *down* on a climber. I don't like being pulled up, but i enjoy being pulled down even less.

5)What about on over-hanging routes where you want a bit of slack to keep from swinging into the wall?

Hmmm, the more I think about it, the more challenging it appears compared to an auto-belay. To me, the main drawback of an auto-belay isn't that it doesn't replicate the lead experience, it's that it fails on steep walls.

Figure out a top-mounted fail-proof mechanism that can protect steep walls, and I think you've got a product. Actually, I was at a bouldering comp where they protected a highball with a pole-vault foam pad, it was like deep water soloing... that might be the solution.

Sorry, I'm drunk and sleep deprived. I'll quit rambling now.


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By Evan Sanders
From Westminster, CO
Feb 26, 2013
Flaming Pumpkin

Crag Dweller wrote:
It's been a long time since I've put any thought into engineering equations but... Have you considered an air brake? Picture a spinning wheel with blades on it. Housed blades for safety, of course. As the speed increases, so does wind resistance. You could even get fancy and design it so that as speed increases, the force is used extend the braking blades further to create more resistance. Not the direction you're headed but maybe that thought will spark some ideas....


I think the difficulty with that would be the braking blade would have to be decently large, increasing the drag of the climb.

I also considered an electromagnetic brake, so if the rotation of the spool were to hit "x" rpms, it would trigger a switch activating a battery. Not sure if that might be simpler of more difficult.


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By Evan Sanders
From Westminster, CO
Feb 26, 2013
Flaming Pumpkin

doak wrote:
Interesting idea. Few thoughts: 1)I'm assuming that it would be mounted on the ground, it would need to be low profile and padded so you didn't mess yourself up if you landed on it. 2)Would the climber need to change their clipping style, or do you have an idea for feeding out slack? Seems like it would be a real challenge to avoid short roping the climber. The alternative is to set the routes so that it's natural to clip at your waist. 3)The lower part of routes is always the most demanding on the belayer, but higher up the belayer can keep a bit of slack in the system. 4)On an auto-belay, the reel tension is pulling up on a climber. For a lead auto-belay, the reel tension is pulling *down* on a climber. I don't like being pulled up, but i enjoy being pulled down even less. 5)What about on over-hanging routes where you want a bit of slack to keep from swinging into the wall? Hmmm, the more I think about it, the more challenging it appears compared to an auto-belay. To me, the main drawback of an auto-belay isn't that it doesn't replicate the lead experience, it's that it fails on steep walls. Figure out a top-mounted fail-proof mechanism that can protect steep walls, and I think you've got a product. Actually, I was at a bouldering comp where they protected a highball with a pole-vault foam pad, it was like deep water soloing... that might be the solution. Sorry, I'm drunk and sleep deprived. I'll quit rambling now.



1) It would probably be pressed up against the climbing wall (or as close as possible), definitely on the ground

2) The spool would be free to rotate and the brake disengaged until the speed of the rotation of the spool hit a certain rpm. This rpm would preferably be higher than the speed you need to pull slack up to clip. The only problem I foresee is if someone is really pumped and tried to yank the rope really quickly.

3 and 4) Good point. There would be a little bit of pulling down, but not like the force that pulls up on a top auto belay. That force is because of a spring recoiling the rob/webbing, the spool is free rotate. So if you climbed a little and then sat back slightly, there would be slack in the system. There would be no spring to autorecoil.

5) If you wanted slack you could pull out slack with one hand. Like I said before there would be no spring recoil.


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By Evan Sanders
From Westminster, CO
Feb 26, 2013
Flaming Pumpkin

Also, about the centrifugal clutch, I like the idea of using it as a redundant fail safe, but I'd like the system to be able to lower a climber not just lock up. Otherwise you could just use a Silent Partner.


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By amarius
Feb 26, 2013

Inductive braking might be simpler, there are automatic belay devices that use it already.
en.wikipedia.org/wiki/Eddy_current_brake


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By Evan Sanders
From Westminster, CO
Feb 26, 2013
Flaming Pumpkin

amarius wrote:
Inductive braking might be simpler, there are automatic belay devices that use it already. en.wikipedia.org/wiki/Eddy_current_brake



auto belay "design"
auto belay "design"



That was actually my first "design" (see above photo, i drew it up because I didn't think it was worth the time to do it on a CAD program). I think it would be the easiest and probably best, however I didn't pursue it because I have a sneaking suspicion it's too close to a TruBlue copyright. The picture is the spool and rope, with a magnet on a hinge. In the left picture it is disengaged, the right picture is after a sensor detects "x" rpms, triggering the magnet over a larger disc, slowing the descent.


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By amarius
Feb 27, 2013

Copyright - that is a really good point. I haven't seen the patent, can't comment what they patented.
Anyways, I am more interested in engineering - you arm idea is cool, what if you make it moveable by centrifugal device - just to keep things steam punk. Or, perhaps, some sort of "smart/click up" and such activated arm?


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By jake 356
From worcester
Feb 27, 2013

Maby look into a design similar to what a seatbelt in a car uses. Almost a velocity driven ratchet.


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By climbnplay
Mar 18, 2013

i'd be curious to see how you would address the problem of someone falling...say just before the 3rd clip, where it's high enough to get hurt but do you have enough time to engage a brake system to not deck? the margin of play is very small in instances like this, no?


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By kilonot
Mar 18, 2013

How about an autobelay that takes the energy generated during descent and feeds that back into the grid to reduce the electrical bill? =P


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