I have a wide variety of types of cordage I would like to test for load bearing capabilities. I am looking for ideas on how to test this without a laboratory. If anyone knows of a good piece of equipment, please let me know. I found a machine that can do it, but it measures in tons, and I need to measure in small increments, from zero to about 1000 pounds (US). The unit of measure is not important as it all can be converted, but the range is essential.

I am not worried about testing without knots as I will always be using the cordage with knots, and I feel this is actually a more accurate measure for practical applications.

I thought about using a car and a strong stationary base as an anchor, I just need to find the piece of equipment to measure the amount of tension. I have also thought about a jack or hydraulic lift, but they either don't have a gauge for measuring or they don't measure in small enough increments.

This forum has always been good for discussing ideas such as this, and I look forward to any and all thoughts on the matter. No idea would be too crazy for the discussion. Thanks.

I will enjoy this thread.

Yes, indeed. Clearly the tension will build to unbearable levels....


Come on Montanero! You didn't really expect help from the likes of us, did you?

Just don't stretch the truth about the results.

In the absence of any helpful suggestions, I will be forced to hang the stuff and put weights on it. I think I will run into problems when I approach the limits of some of the cordage. The Technora claims 950 pounds, and I don't have nearly enough weights for that. I am not sure my rack will hold that much anyway. I will definitely find the limits of several of the components that I have at hand.

Didn't I see the Myth Busters do this with tanks? The gauge displayed the maximum load after it broke. I can't find any such gauges on the internet though.

I have a wide variety of cords: 550 Milspec, 550 commercial, a variety of kevlar thicknesses, technora in 400 and 950, Spectra, and the usual hardware store selection of twines, strings, and ropes.

I would just like to see how strong each really is, and then find the best strength to volume ratio. It is also about really understanding the limits of your gear.

Humor is expected, and even welcome. My fingers and toes would appreciate a better option than hanging weights on it though.

this sounds like a really hi tec project.the stuff you would need would be found in a testing lab.outside of finding a spring scale that handles 100's if not 1000's of pounds and attaching the rope and pulling with a car and watching the results i can't think of any sort of home made gizmo.i would not want to be the guy watching the spring scale when the line busted!!!


i used this old spring scale when i was deer hunting years ago.
it go's up to 500 pounds,more or less.

Joking aside, you might want to do some web searching on field testing of climbing anchors. Folks who do that sort of thing seem to use some combination of hydraulic device for an steady, even, slowly incrementing pull. For the actual measurement they use a various devices called a "load cell" or "pull gauge". Might cost a couple of $K to buy it all, but maybe you can rent or borrow? You also might try to find a college engineering department who will let you do it in a lab as a project by your boy scouts?

Good luck. We are all pulling for you!

I'd use weights from a weight set. Back when I had a home weight set, I could stack 350 pounds on there. The weights would tell me how much tension is on the rope. I'd also try to simulate a knot-less rope, as much as that's possible. Round turns around a large diameter pipe would simulate the no-knot. My old weight set had a weightlifting cage. So, I'd rig the pipe to the cage somehow.

Anything higher than 350 pounds, then I'd take the manufacturer's word for it. At that weight, you're messing with a dangerous amount of tension (not worth risking serious injury). Then, I'd multiply the manufacturer's posted limit by 2/3, and use that as my working max. For example, If the manufacturer says the break strength is 900 pounds without a knot, then I wouldn't push a Bowline past 600 pounds (900 x 2/3).

On the other hand, if I put some fishing-type knot in the rope (which would be a huge knot in regular rope), then I might use that rope at a higher tension than 600 pounds if I absolutely needed to do so.

A few things to consider...

Unfortunately, the results of your test won't really provide meaningful information over the manufacturer's posted limit (assuming the rope is in good condition). Think about it. In the real world, how much tension do you really know you're putting on the line? Plus, on a real job, you're going to subject the rope to shock loading, the effect of which cannot be predicted by a slow load test. You can only make a rough guess, at best, about the effects of a shock load. Personally, I'm more concerned about breaks due to shock loading, rather than breaks due to slow loading. I figure a break due to a shock load is much more likely.

The physics of the rope materials has a lot to do with how the rope responds to a shock load. For example, nylon is quite stretchy. So, a nylon rope will be able to handle a shock load better then a hemp rope for example.

Also, if you bring your rope to its breaking limit, then you have weakened that rope. It's kind of like the Heisenberg uncertainty principle. The closer you get to understanding what you're testing, you inevitably CHANGE what you're testing. So, how does your test give you information about the rope sitting over there on your shelf? It really doesn't. The rope you just tested could have had a random imperfection, or perhaps something is not right with your testing setup. This goes back to the manufacturer's posted limit being the best rough estimate you have.

I do it by comparison.

I take a web/rope of known strength and attach it to the cord in question and then chain with a logging chain to a very large tree (blocked to prevent damage to the tree) and my tow hook on my truck and then slowly pull until something fails.

If the tow hook pulls off--- you have some strong 550 cord.