4 Slackline Pulleys Compared 

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I just typed over all the results into a spreadsheet, and calculated the obtained mechanical advantages and the corresponding efficiencies (relative to the theoretical figures). Let me know if you need the data. The results are scattered a bit - at least in part, this is likely due to the varying geometry, as others have observed - but a short summary of the efficiencies would be: SMC pulleys: in the 50 % range, drops to 40 % with two staggered 3:1 multipliers. Slackline Brothers: about 50 %. Raed BLNC 5:1: 60 to 65 %. Rollex 3:1: around 40 %. Rollex 7:1 and 9:1: around 45 %. I'd also like to point out that you have installed the Raed BLNC pulley system in an unusual orientation: the unit with the brake is usually attached to the anchor, not the weblock. Funny thing is, installing it the way you did actually gives a 6:1 instead of a 5:1, but at a cost. One drawback is that it might be harder to release the brake if it's on the moving end. The other drawback is that by adding a multiplier on the last strand, you get a 14:1. Had you installed the pulleys the other way around, you would have gotten a 15:1.

There are a lot of comments to make. I have a friend who designs pulleys for a living and he informs me that there efficiency is different with each different rope, under different loads, and at different rates of pull. This makes labratory testing difficult to relate to real world use. Bravo for doing practical real-world testing. In your first system, with your big SMC pulleys, the wild card is grigr, which is much less efficient than the rest of the system, and is located initially at the worst possible location. The friction has more effect the closer it is to the pulley. Those SMC pulleys were originally intended to be used with a progress capture prussik located at the first turn around, it would be much more efficient used in that manner. I think a lot of your variations that you saw during this test was related to how the grigri varies in friction depending how much load it has on it, and it was being loaded differently with various multipliers. Another variable that is hard to quantify is what angle you were pulling at. It looked like you were off to the side pulling, probably to avoid the tripod with the camera looking at the dyno. The angle that you pull at can potentially have a large effect on the forces in several ways, and it is complicated to quantify. I think this explains why that elegant little pulley set-up is so good, it has been set up so it's components are arranged in an optimum manner. It's an impressive device. The last system you showed illustrates the advantages of using fewer components in order to minimize friction. I appreciate the elegant symplicity of that approach. Those pulleys are probably also more efficient than they look, since the greatest factor of pulley efficiency is the ratio of the shiv diameter to cordage diameter, and using the webbing means the cordage diameter is tiny.

Thanks for another great video!! The first 3-rollex setup you show is not a 5:1 but a 9:1, which explains why the 7:1 afterwards wasn't able to increase line tension.

I’m an arborist in northeast Pennsylvania. Your gear tests and pulley system data is very interesting and helpful. Thank you very much.

I don't think the rope is supposed to go through the hole of the SBI break @15:00. There are some videos showing how to use a multiplier with them too! Great video!

You run really nice tests! Wonder what are the forces involved in a climbing self rescue cenario using pulleys systems (3:1, 5:1, 7:1...)

Andy Lewis used to have RU-vid videos showing the use of the Slackline Brothers pulleys. Andy always had the brake at the anchor. He also did not put the rope through the brake arm. Instead, he used a carabiner through the eye of the brake arm to release the brake using a multiplier by passing the rope through the carabiner which also added some control friction during release. . I believe that Andy's setup was better than what you demonstrated and might give better results. It is definitely more convenient. However, I don't remember if he was able to reengage the brake if the webbing was really stretchy or long.

I think the reason you aren't able to pull with as much force when the multiplier is higher is because more of the energy going into the system comes from your movement rather than force at any given point in time. _(In physics, "work" is defined as force times distance.)_ It's kind of like the difference between running with 50lb on your back and walking with 150lb; as long as you run at least 3× faster than you walk, you're doing more "work" running with 50lbs. A totally different way to look at it is that when the rope moves too quickly, you have a hard time planting both feet on the ground and getting your core into the pull.

So when you pull really hard, when you throw your body into the dynamometer in your hand, you cause a spike of force in the system giving you a really high pull weight at the hand, 1kn or so, that is not translated through the entire system at the same rate to the dynamometer at the other end. The stretch of the rope and webbing over 50 meters of material acts as a shock absorber. So, on a 9 to 1 system with 1kn on the one end, you should get 9kn at the other end minus whatever your friction loss is, but you won’t get that by jerking on the rope. You have to apply a slow and sustained amount of energy on the end of the rope to get an accurate reading at the other end. Also, I noticed you were pulling at some pretty sharp angles, especially when you were working with the really short system. The harder the angle you pull, the less effective your pull. You have to pull 180 degrees against the pulley to get the most out of it. If you pull 45 degrees less than 180, so 135 degrees, you loose 25% of your energy right from the start. I’m not a slack liner, I just love playing with rigging and stuff. I pulled a tree out of my yard this year with a 150 to 1 system just for fun. The come-a-long would have been so much easier. Something you should look into is the ‘Niftylift’ block and tackle system. It’s a super light weight and highly efficient 5 to 1 block and tackle that weighs less than 1 pound and is 90% efficient. It’s made by a retired engineer who wanted to keep busy and make some money on the side. Any way, thanks for showing off your gadgets, that’s good stuff.

maybe you can pull with less force with higher multiplication because the point from wich you pull is lower and lower to the ground, and that matters because if the point of pulling is higher up you can basicly put yor entire body weight on the rope, but if its lower down its harder to pull without your feet sliping on the grass. just my theory and i can see many flaws within it, so if anyone can expand on it that would be swell

thanks Ryan!

interesting, what setup would you consider having for occasional pulling of stuck car by hand ?

Have you considered trying a yacht tackle block? Those things have assloads of multiplication, meant for super high force and stainless steel. Sure probably way top much for a day of fun. But if you're doing any permanent / semi permanent setups it might be good

Nice work 💯

Can you do this test again and get Brian Shaw or Eddie Hall to pull .

With your roller system: The setup you tested before your "7:1" setup is actually a 9:1. It's a 3:1 multiplied with a 3:1 = 9:1. I'm not sure what mechanical advantage your "7:1" setup gives, because the way the forces work is a bit confusing at first glance. If you were to place 2 rollers at the soft shackle and 1 onto your line lock, then run 2 strands through that one (like a primitive setup), you'd have a 15:1.

You may be pulling with all your strength and body weight, but the other side of the LineScale is still only gonna see the easiest side of your pulley multipliers....I'm not an expert on the line scales but I think it's only measuring the outward force when both sides are engaged. So we know the the 3:1, 5:1, 9:1, etc. let you get more work for less energy. Especially this nifty pulley system that inches closer together as you pull, it gradually gets more efficient as they get closer together( less drag and less weight from the ropes)...This is just me taking a guess at why it's not going up as you add more tension..I'm far from a psychics expert lol.

I can't help it so interesting. But I always had the mindset that it was a purchase. If you had a 9:1 than you would haul 9ft of rope to purchase 1ft of heave. Not so much as to tension. That's what ratcheting pulleys do. Or a ratcheting strap. Right on.

I didn't know Grigri was strong enough to progress capture! Though perhaps it not being a pully adds lots of friction? I was using a micro traxion at the end of my pully system but it was almost impossible to unlock with a lot of tension. Gona try that setup asap! 🤙

Everybody is saying don’t high line on a ratchet, wouldn’t it be fine if you backed it up ? Still in learning stage it just seems way easier

SBI for the win!

great video :) i would try to pull only directly in line with your sackline, because you „loose“ a lot of force in the other direction when pulling at an angle as you did

the reason why you were pulling over 1 kn some of the time and only .3kn others is because you where pulling down hill on the 1kn and up hill only getting .3

You can't reach 1kN with the pulley, because at the strand you are pulling with 1 kN there ist now the pulley that pulls 1kN. But you only have to pull 1/2 of that force. And you have walked much more at the 1kN strand then the pulley does.

6:30 that was a 45:1 5:1x3:1x3:1

Hey Ryan I got one for you. What advantage do you get if you combine a primitive type tensioning system with the Buckingham method? In other words use a soft release and run the tail of the soft release through your line slide that is clipped to your snatch.

I think it all has to do with the peak force on the tail end being just a momentary spike of energy that doesn’t have time to travel through the system to the dynamometer. A very slow and steady pull would probably be more accurate.

Nice neck

You poor hands. Next time tie something to the Dyna! Interesting video!