UKC

Anyone have any idea how much weight does an auto belay pull whilst the climber is climbing up the wall?

Less or more than a kilo?

Get a fishing scale and attach it to one to find out? I'd have thought it's quite a bit more than 1kg...

a good question. seems to be quite a few kilos to me as I can climb a grade or two higher on autobelay.

I'd be curious too, but dont thi k its that much.  Also there are times you're climbing that the device is catching up and bearing no weight 

Good question, I 'll try and fine out.

They use a coil spring so I would expect the more you pay them out the more tension would be on the spring and the more pulling force it would generate. For accuracy you would need multiple readings up the wall. 

You could easily check using one of those little spring balances you use for weighing a suitcase. 

Just remember to remove it before you set off upwards...

I don't have a value. I would expect it is negligible, given that tension is only felt when stationary, once the climber moves upwards any tension is lost. So assistance when resting but none whilst climbing. 

Do you mean a watchmakers style coil spring? Abit like this one : https://www.made-in-china.com/showroom/springisanart/product-detailtXWxTkFM...  In which case actually the tension is pretty much even through the range of non stressed acceptable motion. To me this would be the obvious way it would work, much like an auto recoil hose unit in workshops which use this type of spring. A coil spring is normally either a standard compression spring or extension spring and I don't really see how that would work, but yes if that were the case then the tension rate would vary through the motion... happy to be proven wrong?

How is tension lost? The only way tension would be lost is if the tape doesn't recoil at all and the spring would be doing absolutely nothing...

I compensate for the assistance given by the auto belay by adding an equivalent amount of weight. I drop the right amount of potatoes down the back of my Ron Hills. 

If you jump while in an ascending lift, while you're in the air the lift is no longer propelling you upwards.

(Warning: we could be getting dangerously close to planes and treadmills territory!)

Haha - maybe I shouldn't have said tension - the spring is still recoiling if you dyno and retracting the tape so it's still doing work...

Speaking as a climber whose progress is definitely impeded by "fear of failure", amid the myriad of training tools available, I think there could be a place for an autobelay with a small, adjustable "assist" mode, it would be like one of those partners that gives you a tight rope on routes that he/she has wanted the belay, wanted their gear back, but knows deep down there's no chance you'll get up unassisted.

Obviously they would be strictly for training use, and anyone caught running around shouting that they had just climbed 7b using one would be publicly ridiculed on UKC and other such media outlets.

I'm not a spring expert but I do know that the recoil air hoses we use at work get harder to pull the hose out the more hose is deployed. They also wind in faster if you have the full 10 meters extended than they do if you only pull the first couple of meters out. 

Other than the mechanism used to control the decent rate I would think the winding spring is the same sort of idea 

17 replies and nobody yet mentioned that weight is measured in Newtons, not kg. 

https://images.app.goo.gl/wownghc6bZKKRpwTA

haha ! I almost did by linking o a constant force spiral spring...

TruBlue autobelays have a minimum weight limit of 10kg (or 98N if you prefer).

You could infer from this that a weight of less than 10kg (or at least significantly less) wouldn't be sufficient to overcome the coil spring and it therefore provides a "pull" of getting on for 10kg.

On the other hand that does seem like a lot so perhaps the minimum 10kg is just an arbitrary figure?

Bloke at the wall, so it must be true, today said, 2.2 kg.

I could easily hold the belay device with one finger, I'd guessed 2kg before then bloke told me what is was.

In my experience a bag of oven chips can be more easily moulded to the anatomy.

The easiest way to discover this is to use an auto belay. 

When you are stationary there is tension to your harness, giving you some (minimal) assistance. As you start to move, your velocity is greater than the recoil velocity of the auto belay, you will feel the slack at your harness. At the end of your move the tape catches up, offering assistance once more. For the majority of each climbing move there is no assistance from the auto belay. 

I'd think that the word assistance should be quoted. My experience is that the "assistance" of a pull is more of a hindrance than a help, a bit like an over-keen belayer on top rope who likes to give you a reassurance tug just as you get your finest point of balance, just when you don't want it.

Took me a year to train my son that the aim was not to try and drag me up the wall

Watch/clock springs don't provide constant torque but something pretty close over much of their expansion range. There is another arrangement with the spring unwinding from one spindle onto an adjacent one that does provide near as damnit constant torque and they're available in motor/autobelay sizes. 

Jk

That's likely more to do with the bulky hose coming off the reel, reducing its radius as you go, a (near) constant torque spring under those conditions will deliver an increasing force as the hose unrolls and the lever arm reduces quite dramatically. Same effect occurs with rolled tape of course but likely to a much lesser extent assuming the drum is big by comparison with the tape thickness.

jk

the 10kg, is to enable the braking mechanism (magnetic force) to engage / start working. You need a certain amount of speed in the mechanism to create the eddy currents used to slow you down.

I blame Weight Watchers. I wrote to them suggesting 'Mass Monitors' would be more appropriate but never heard back.

Good point, I never considered that. It probably drops from a diameter of about 450mm to about 300mm once unwound. 

This is what I love about this forum, the diverse range of the people who read and comment on here. As the saying goes every day is a school day. 

Right. Definitive answer.

I've just tried it on three different TrueBlue autobelays and it stopped going up with 2 x 2 litre containers of milk and 900ml of water in a bottle.

Quick Google of the weight of milk and I can confirm that it's 5kg near as damn it.

P.S. Couldn't be arsed to try it at different webbing extensions. This was 8 metres from the casing.

My physics might be a bit rusty but ignoring air resistance all objects fall at the same speed, 1kg 10kg or 100kg doesn't matter, so surely the minimum force is to overcome the internal resistance of the device rather than to generate sufficient speed?

The force downwards isn't the same for 1kg, 10kg of 100kg, is it, otherwise you could hold  100kg in you hand as easily as 1kg.

Since the force turns a rotor in the device, the harder you pull then quicker it turns, the quicker it turns ( or tries to ) the more breaking effect you get.

From a manufacturer, though, it's not much help

Hi Krikoman,

Thanks for reaching out.  What a great question!  Perfect Descent auto belays are designed with the intent of not assisting the climber.  Obviously, there will be a tiny bit of pull since the lanyard is under light tension to retract back into the unit, but it is very minimal.  The answer to this question would differ between the Direct Drive or the Speed Drive units.  The Direct Drives have a retraction rate of 2ft/second and the Speed Drives have a retraction rate of 15ft/second.  The answer to your question would also differ on the length of the lanyard (28',40', 53'), since the retraction spring would be under more tension if it is working with a longer lanyard.  The weight of the connection point (are you using a steel carabiner, aluminum carabiner, or dual connections?) would also have an effect on this answer.  Are you asking about one particular auto belay unit type?

To answer the second part of your question, any perceivable pull would be a bit stronger as you are standing at the bottom of a climb, where the retraction spring is fully engaged.  As you climb up, the retraction spring is under less and less tension, so that pull would minimize even further.

The easiest way to answer your question without having a specific unit's quantifiable "pull" handy is that we are entrusted to be the International Federation of Sport Climbing (IFSC's) sole auto belay supplier, and the Perfect Descent manufacturer has put a lot of effort into ensuring that your question is a non-issue.  Hope this helps!

Thank you,

Ruthie Lile

Technical Sales & Support

Aerial Adventure Technologies, LLC

They can't even spell aluminium right!!!

I've checked the speed climbing rules and it gives you all sorts of info, how accurate the timer needs to be, how much angle the overhang is and it's tolerances, the approved auto belay manufacturer, but nowt about the auto belay pull force!

There's three different levels of pull force in the autobelays at Ratho.  The Perfect Descent ones on the speed wall don't pull upwards as hard and give a much bouncier fall than the TrueBlue ones.  But it also seems like there's different calibrations on the TrueBlue because some have a much harder pull upwards than others.

Hi All, the Lady from the IFCSs auto belay supplier has got back to me with further info.

Hi Krikoman,

I asked around about this a bit more and here's some additional info:

- the Direct Drive and Speed Drive units actually have the same pull force, but the other factors (lanyard length and connection weight) would still affect the pull force

- IFSC accepts an absolute maximum pull force of 5 kg (about 11 lbs) for any units.  That maximum pull force could be felt at the bottom of the climb, as I mentioned, and it would minimize as you climbed up the wall since the retraction spring is under less tension as you climb.

So @Oceanrower was correct, and they should receive the prize money.

At times, not enough!

I WIN!!!!!!!!!! 

So if I'm on an a plane at the front and jump up will I travel backwards??

Do I need to wear my lucky underpants to aid survival of impending aviation catastrophe?

Relative to what and is the aircraft accelerating? In the cruise the basic answer is 'no'.

jk

That's speed climbing autobelays though, which retract a lot faster than normal ones. Even a static-climbing old traddie sloth like me can easily outclimb a normal autobelay and have to wait for it to catch up to avoid too much slack.

It's both, the speed of retraction has little to do with the pulling force, which was what the OP was about.

When you are climbing you will negate the pull for it, I think the idea behind the OP was how much "help" do you get out of one, so you're trying to make a hard move and the AB is supporting you by how much; max. 5kg

I think we should share, since I did all the donkey work, to prove you right. I'll keep an eye on the post.

If you're on the outside, almost certainly, yes!

It's always worth wearing lucky underpants.

Wouldn't the route setter / grader enjoy the same benefit from the autobelay when testing and grade accordingly.

Hmm. But I had to lug a load of milk bottles around.

That's far more donkey work than sending an email!

🤔

How much weight would an autobelay pull if an autobelay could pull weight?

And do autobelays work inside a plane on an escalator?

Only vertical escalators.

Measured one of them at our local wall with  a spring balance; 5kg.