Ultralight Block and Tackle (a neat product and a DIY Hack)

[JAG]

I listened to a recent podcast that mentioned the PynchPulley from Wiser Precision. These ultralight pulleys are very nice. With them, you can lift a lot of weight with a fraction of the effort.

I almost pulled the trigger and thought, what about a motorbike chain as an alternative, DIY hack? Here are my two set-ups, one with 4:1 and the other with 6:1 (the other half of the 6:1 pulleys were in the garage). I tack-welded the 4:1 pulleys to keep them straight, but I don't think this is really necessary.



I researched the breaking strength of a single link of 410 motorbike chain, but all I could find was statistics for the entire chain. To the garage. I stressed the cord with two clamps to test the strength of the chain link and could not get enough weight to break the cord or a single link. This would be helpful to lift an elk up a short cliff or out from underneath a log.



6:1 pulley mechanical advantage: for every 1 pound of force applied, you can lift 6 pounds of weight. With a 700-pound load (entire elk), you would need to apply approximately 116.67 pounds. My 6:1 pulley system is going in my kill kit in case I have an elk under a log or down a short cliff.

A 4:1 pulley mechanical advantage; with a 200-pound load (bone-in quarters and backstraps), you would only need to apply 50 pounds.

I have 2mm Dyneema (440 pound tensile strength) and 550 paracord (550 lb tensile strength). For the attachment points of the load, I doubled the Dyneema for 880 tensile strength, but the weight on each of the pulley's will be considerably lower than 440 pounds each.

 

[elkduds]

 

[JAG]

This is a much easier-to-make solution than the chain, but doesn’t have the benefit of the reduced friction that the rollers offer.

It’s good to see how the chain links are smooth enough to work.

 

[elkduds]

This is a much easier-to-make solution than the chain, but doesn’t have the benefit of the reduced friction that the rollers offer.

It’s good to see how the chain links are smooth enough to work.

It is small, light and good for hoisting deer-sized game, elk quarters, nothing heavier. I carry one in a ziploc. Not as robust as yours, though.

 

[Rogerdoger]

I just was looking at these, I like the idea of the dirt bike chain, save me some cash!

 

[Syoungs]

I like the bike chain idea.
Ill probably end up just getting the pack a pull system with some dyneema rope as its easy, But i may play with the chain idea to make some for my buddies, or redundant systems!

 

[JAG]

This is a cry-once-buy-once aspect of the project.

100' of 550 paracord (4mm diameter) does the job for around $12. However, it really starts to stretch and lose efficiency. In my nonscientific test with the two clamps and short orange paracord (photo above), it stretched at least 2 inches before I couldn't crank it anymore. This is a lot of stretch from about 3' of paracord and efficiency loss if pulling 20-50' of cord. Some of it was the knots tightening, but like I said- 'non-scientific'.

I won't use the 2mm Dyneema (green cord in the photo) as a pull cord through the pulleys for two reasons, 1) it's expensive and 2) it looks just small enough that heavy weight could get it pinched in between the roller/bushing connection to the inner plate.

If you want next-level performance with nearly zero stretch and superior tensile strength, get 3.5mm or 4mm thick Dyneema. One site has a 100' roll of 3.5mm Dyneema for $54.

Other items: $14 for 410 motorbike chain (has a bushing, roller, and a pin for low friction)
Angle Grinder: $25-$75 on Amazon to cut the chain plates and round over the burrs.