Mythbusters did this with interwoven phone books, some sort of tension scale and an APC. I don't think you are going to find that kind of scale here in Fayetteville, but one never knows.

Try calling around to some of the machine shops and see if they have one. Failing that, call a local gym and ask if you can use a lot of weights for a short term at their facility.

Good luck

A 55 Gal. drum will hold about 450 Lbs. You could string up the empty drum and start filling it. Note the level of water as you go until it breaks. Fill the drum from a platform beside it so no body parts can get under the drum. Water is about 8.3 Lbs. I think.
Good luck.

The manufacturers of the cord/ropes will provide reasonably accurate breaking strain forces for their cords/ropes especially where there is a safety issue.

Breaking strain forces are not the be and end all of manufacturing cords and ropes. There are elongation, dynamic loading, creep, environmental specifications as well. i.e. Mil spec Paracord being nylon has a 30% minimum elongation specification before breaking etc.

https://en.wikipedia.org/wiki/Parachute_cord

There are many types of paracord with a wide range of breaking load forces.

Dyneema cord/ropes will have a much higher breaking strain forces and improved minimum elongations etc.

Kingfisher evolution race 4mm Cord have a breaking strain of 720 Kg or 1580 lbs. i.e. 3x MIL-C-5040H 550 type III cord.

http://yachtropes.co.uk/race.php

Are you intending to do some emergency abseiling? Using paracord is probably not a good idea!

http://www.youtube.com/watch?v=OeF-Vcq2g5Y

I am more concerned with the cords I find that do not have manufacturer information. I find the 550 in the surplus stores and the other types of cord on line. It is as much about checking the veracity of marketing claims as it is knowing about different types of cord. I find some at good prices, but I would like to verify their claims to a reasonable degree. I was just looking for techniques for doing so.

It seems that if you're looking to verify manufacturer claims, then maybe you need to look into how manufacturers rate their ropes. Does 500 lbs mean static tension, holding indefinitely? Or does it mean a one foot drop with 500 lbs attached?

It seems like anything involving more than a few hundred pounds could be very dangerous. I started thinking about how I'd design a tester, and then I thought, hey, someone's probably done that. Lo and behold:

http://www.youtube.com/watch?v=JVRI45AXOHA

It seems that the company (http://admet.com) sells a bunch of testing machines. Buying one of these is probably the best thing to do, though it may not be the cheapest.

If you can work with metal, you may be able to make a similar tester with gears.

If only approximate testing of the strength of cordage is required, then you can make your own test rig fairly easily.

Obtain a short length of substantial RSJ or timber, and support each end of this on a small pier or column of bricks or concrete blocks.

Attach the sample to be tested to this support, and attach weights to the sample until it fails.

To avoid danger from the end of the tested cord whipping around, or from the weights falling, arange such that the weight will only fall an inch or so.

A suitable weight up to about a ton is an IBC of known empty weight. Suspend this from the sample, and fill with water from a safe distance by use of a garden hose.
Either measure the volume of water added by a water meter, or use a container with markings as to volume.

With a little ingenuity, other methods can be devised. Use of a water container that can be emptied or filled remotely has much to commend it as no close approach during testing is needed.

How you apply the force depends on what you want to measure. Do you want to test a static load or a dynamic load?

A static load requires you to slowly and gently add weight and you are measuring a weight.
A dynamic load, depends on what kind of dynamic load you want to test. But you test with a force, so newtons instead weights.

Anyone know the aprox. strength of jute? I am curious about replacing some of my synthetic cord on shelters with jute. Need something with a strength of about 80 lbs. Wondering what diameter would be needed.

The only tool you really need is a set of max recording spring scales in the ranges (at 50% of full scale) that you need. You can get by without them by using an increasable load (the water barrel or weight plates suggested above). You need something to provide the load, but many good ideas have been recommended for that. The way you use it will certainly depend on the information you need. There are standards for testing that will make the information consistant. NFPA, UIAA, ASTM, CEN and many others have their testing protocols. In order to understand and compare strength you need to know how the rated strength is obtained.

Safe working load may vary from 25% of the breaking strength for non-critical situations to about 7% (15:1 ratio per NFPA) for supporting humans (climbers have traditionally used a 10:1 safety factor). Knots can reduce breaking strength by as much as 50% or as little as 15 or 20%.

Respectfully,

Jerry

If you are looking for a natural fibre rope/cord to replace synthetic paracord then hemp would be a better bet with a higher breaking strain over Jute.

A 5mm braided Hemp rope/cord has a 190kg breaking strain.

http://www.jaderope.co.uk/natural-hemp-rope-5mm-braided.html