Wiser Precision Pynch Pulleys

[Marshfly]

Tiny diameter pulleys with small diameter cordage is going to be virtually impossible to move significant weight with. Just physics at work.
And pulling a wrapped raft off with these and tiny cordage? LOL. No. Not remotely.

 

[MaraviaDave]

I setup a 2:1 and 3:1 in a block and tackle setup using good quality 550 paracord. I was pulling down to lift a load of 50lbs (rove to disadvantage) just like I would to hang quarters.

Using my bow scale the load (dumb bells) measured 48-50lbs without mechanical advantage. In a 3:1 setup I had to get the rope tension to ~43-45lbs before I could lift the load. Once suspended the rope tension was almost exactly 16lbs as you'd expect. To lower the load the rope tension gets to nearly 0lbs before it starts to lower.

In a single pulley lift (no mech advantage) the rope tension hit a staggering ~70lbs before I could get the 50lb load to lift. This is with nearly 180 degree wrap.

I also tested 75lb load lift in a 3:1 setup and felt like I could barely get it off the ground even with a t-handle. Rope tension hit ~66lbs before it came off the ground.

My findings align with this website which shows throwing a line over a 0.5" diameter carabiner with no sheave provide ~54% efficiency. I think due to the small size of the Pynch Pulley ball bearing you end up with a similar result.

Pulley size and rope stretch — Alpinesavvy

Pulley diameter and rope stretch do affect your hauling efficiency. It’s more relevant to mountain rescue teams and big wall climbers than to alpine climbers.

www.alpinesavvy.com

You entirely missed the main point of the article you referenced in your post. Which was discussing rope stretch, and its effect on hauling efficiency, having more of an adverse impact than pulley diameter. Followed by discussing the different types of ropes used in various climbing disciplines. Specifically, static and dynamic ropes.

The 550 paracord you used for your test, would be considered a significant step below the rope types mentioned in the article, from an elongation/stretch perspective. The mil-spec requirements for paracord indicate a stretch of greater than 30%.

Yes, I know WP mentions 550 paracord in their product description. Which I think is a mistake.

If you want a more suitable rope for use with the Pynch pulley…..I’d look at something in the 3 mm size range, made from Dyneema SK75 or SK78. This would give you a rope with essentially no stretch and more load strength than the pulleys themselves.

Repeat your tests and you’ll see that your original test only proved that 550 paracord is the wrong choice for the application.

 

[MaraviaDave]

Ultraglide Bear Line

Our Reflective Ultraglide bear line was specifically designed to be used as a bear bagging line. It is Ultra Strong, Ultra Slick, Ultra Light and Ultra Tough. Our cord is made using Dyneema SK75 which is one of the slickest, strongest and lightest weight fibers ever created. Unlike other...

www.lawsonequipment.com

Here’s what I’m using with the Pynch pulleys. (3.5 mm size, 4 pulleys)

 

[BackcountryNC]

You entirely missed the main point of the article you referenced in your post. Which was discussing rope stretch based on the different types of ropes used in various climbing disciplines. The 550 paracord you used for your test, would be considered a significant step below the rope types mentioned in the article, from an elongation/stretch perspective.

Yes, I know WP mentions 550 paracord in their product description. Which I think is a mistake.

If you want a more suitable rope for use with the Pynch pulley…..I’d look at something in the 3 mm size range, made from Dyneema SK75 or SK78. This would give you a rope with essentially no stretch and more load strength than the pulleys themselves.

Repeat your tests and you’ll see that your original test only proved that 550 paracord is the wrong choice for the application.

I don't think I missed the point.

The first graphic shows the efficiency of various pulleys using the same 1/2" static rope. Slung over a carabiner produces very low efficiency (53%) and using a 3.75" diameter sheave produces up to ~91% efficiency.

The second graphic compares steel and rope types and their efficiencies. The static rope using the 3.75" sheave shows ~91% efficiency which matches the first graphic.

I'm actually going to test some low stretch rope this weekend. Likely New England Spyder Line. If I see things improve dramatically I may still keep these. As others have commented my hope to get high efficiency from these might have been too wishful.

As an aside how does that Lawson Bear Line hold knots? It seems like a great option to potentially pair with these or other low weight pulleys.

 

[BLJ]

Ultraglide Bear Line

Our Reflective Ultraglide bear line was specifically designed to be used as a bear bagging line. It is Ultra Strong, Ultra Slick, Ultra Light and Ultra Tough. Our cord is made using Dyneema SK75 which is one of the slickest, strongest and lightest weight fibers ever created. Unlike other...

www.lawsonequipment.com

Here’s what I’m using with the Pynch pulleys. (3.5 mm size, 4 pulleys)

Has this system seemed to be efficient for you?

 

[MaraviaDave]

Has this system seemed to be efficient for you?

Yes, the Lawson Equipment 3.5mm Ultraglide Bear Line, paired with 4 Pynch Pulleys, seem to be a well balanced combination.

I haven’t done any efficiency testing, with the setup, using a weight scale. However, I have quite a bit of experience setting up and using pulley systems, for both river and glacier rescue, during training / practice scenarios. Along with a number of actual field rescues.

Subjectively, this pulley/rope combination seems to be really good….especially considering the size and weight.

The rope is slick (moves through the pulleys easily), has almost no stretch (very efficient transfer of force), and has a nice feel to it (stiff enough it doesn’t tangle easily…yet holds knots well).

I’m looking forward to using the system, on this year’s moose hunt, to flip/roll a bull over while field processing. As opposed to the yearly moose wrestling matches, we’ve had in the past!!

 

[BLJ]

Thanks @MaraviaDave.
I’m going to have to look into this a little more.

 

[BackcountryNC]

I tested some different rope tonight. Unfortunately all I could get my hands on this week was some 1/8" hollow braid Dyneema. I figured it would be 'close enough' to 7/64" max Dyneema diameter recommended by Wiser but it ended up having really high friction in the Pynch pulleys. I would not recommend it. See my attached photo showing fraying of the Dyneema.

I did compare lifting 50lbs in a 1:1 and 3:1 setup with paracord and the Dyneema. I tested some cheap 1.5" diameter pulleys and found rope tension to be within 1-2lbs with both ropes. It didn't seem like the paracord rope stretch was impacting efficiency.

Finally, I ran the paracord through the pulley eyelet (like you'd use a carabiner in place of an actual pulley). The eyelet diameter is very nearly identical to the Pynch Pulley ball bearing size (I'm guessing 7/32" diameter). Photo for reference. In both 1:1 and 3:1 setups the rope tension was the same running either Pynch pulleys OR through the pulley eyelet. Results showed ~50% efficiency.

@MaraviaDave if you are using a solid core rope with very low friction jacket the results might be better. A scale would tell for sure.

I think I'm going to purchase some lightweight 30mm diameter pulleys from the sailing community like the Harken carbo air series or the Ronstan orbit series. They seem to weigh 1-1.5oz each, have decent working loads and have ball bearings for higher efficiency.

 

[camelcluch]

All this to lift something? I am way to dumb to figure out all the smart stuff involved. I can work out and lift the 90# elk quarter or a 130# moose quarter. Maybe I’m too dumb to know I shouldn’t be lifting heavy stuff. Pisses me off that all my teachers were right. Thanks Rokslide!

 

[idcuda]

There's this option, too. https://packapull.com/

Out of the Boise area.

 

[jth7186]

There's this option, too. https://packapull.com/

Out of the Boise area.

Thank you for posting.

 

[Voyageur]

Yes, the Lawson Equipment 3.5mm Ultraglide Bear Line, paired with 4 Pynch Pulleys, seem to be a well balanced combination.

I haven’t done any efficiency testing, with the setup, using a weight scale. However, I have quite a bit of experience setting up and using pulley systems, for both river and glacier rescue, during training / practice scenarios. Along with a number of actual field rescues.

Subjectively, this pulley/rope combination seems to be really good….especially considering the size and weight.

The rope is slick (moves through the pulleys easily), has almost no stretch (very efficient transfer of force), and has a nice feel to it (stiff enough it doesn’t tangle easily…yet holds knots well).

I’m looking forward to using the system, on this year’s moose hunt, to flip/roll a bull over while field processing. As opposed to the yearly moose wrestling matches, we’ve had in the past!!

Have you had a chance to use your pulley system in the field?

 

[0815]

This morning I set up a 3:1 with a single block and a double block from Ronstan and 1/8" Amsteel blue rope.

Series 20 Ball Bearing Lashing Orbit Block™

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www.ronstan.com

and

Series 20 Orbit Block™, Double Lashing

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www.ronstan.com

Anchor point was the carabiner where my game joist hangs on the bottom of the garage truss.
I first tried with a pressured air canister weighing 12.29#. The scale registered around 4.2#.
Went over to the house and got the backpack. Backpack is loaded with a sleeping bag and a 60# sandbag.
I pulled it up with the pulley and had the scale between pulley and backpack. Backpack registered at 72.49#.
I then made a pull loop as far up as I could reach on the pull end to hook the scale to and pulled on the scale handle. The scale was upside down but when the load was lifted, the scale was showing right around 24.8#. It was nice and easy to lift.
But you will need a suitable amount of rope., but the 1/8" Amsteel was pretty good to handle even without a pull handle. With a pull handle probably real easy.

I have not tried the Wiser Precision Pulleys, but the Ronstans linked above are a great product in my opinion.
I would not try these with Paracord 550. Way too much stretch and that defeats the purpose.
Historically pulleys where outfitted with hemp rope which has very little stretch for a natural fiber rope.

 

[Vrybusy]

The Harken pulleys work very well. Extremely small and well built. I've used a pulley set up with amsteel/dyneema rope in the mountain whitetail woods for several years now. As mentioned above 550 has too much stretch and is not efficient. The pulley system works very well and can lift a significant amount of weight without issue.

 

[0815]

The Harken and the Ronstans are imho almost identical. Both are designed for sailing/boating and are available in different sizes. The Harken 18mm should be almost the same same as the Ronstan 20mm.
It seems the Ronstan has a little better working load and higher break strength and is a little cheaper than the Harken 18mm. The Harken may be a gram or two lighter, which cannot be verified by giving the weight in oz.
Should be given in grams or in grains for these small weights.
The advantage with the Ronstan or Harken is the use of a wider amount of rope diameters. This makes them more versatile than the Pynch Pulleys in my opinion.