Break Test: Locked Brummel

[moray]

The locked Brummel is a very peculiar creature. It has characteristics of both a knot and a splice and seems to confuse just about everybody, myself included. It is never used by itself (see picture below); the tail, often much longer than the one shown, is stuffed into the rope to make a proper buried splice. Since the Brummel can't come apart or unroll like a knot, it offers absolute protection against a splice that comes apart--the eye is still there, still holding the load, because of the Brummel.

How good is this protection? How does the Brummel behave when it is pulled to failure?

The photo shows my test Brummel tied in 5/16 inch Samson Tenex Tec. This rope has a published average break strength of 4700 lbs. The tail is 3.5 inches long and tightly taped at the end to make sure the Brummel would break before the tail could unravel. At the other end of the test piece I spliced an ordinary eye with a tapered bury.

Even though I was certain the Brummel would break long before the splice, I needed baseline data for comparison: I needed to know the break strength of a similar piece of rope with two ordinary splices but no Brummels. Altogether I did 4 tests: 2 break tests on control ropes, and 2 break tests on Brummels.

 

[moray]

All four test ropes came from a single piece of new Tenex. The results, in pounds, are as follows:

Controls: 4400 4460
Brummels: 2742 2594

The first picture shows the first Brummel test at 1004 lbs. tension. It has already become so tightly knotted that it is nearly unrecognizable as a Brummel. It only gets worse from there.

The first strands snapped at 2742 lbs, which I took to be the point of failure. Interestingly, most of the strands are still intact. The second Brummel test followed this exact same pattern. Note also that strands have broken on BOTH sides of the Brummel. Considering that the eye side of the Brummel has the load split between the two legs, it seems remarkable that anything would break on that side. Again, both Brummels showed this same pattern of failure.

The controls broke, as expected, at the very end of one or the other of the two buries.

The last photo is a closeup of the first Brummel test after more pulling had broken most of the remaining strands. The tension never again rose to 2742 lbs, and I did not bother to break the last few strands. Note in the photo the broken strands on BOTH sides of the Brummel.

 

[canopyboy]

Awesome, simply awesome. Having just done some brummels, I appreciate it. Do you have any intention of doing a buried brummel with a 6" tapered bury like you would do on an eye-to-eye? They all claim the taper is very important because otherwise it breaks at the end of the bury. I would also like to see how a double (or triple) fisherman's knot holds up, since that is usually the alternative to a brummel in an eye-to-eye.

 

[Tree Pig]

Awesome, simply awesome. Having just done some brummels, I appreciate it. Do you have any intention of doing a buried brummel with a 6" tapered bury like you would do on an eye-to-eye? They all claim the taper is very important because otherwise it breaks at the end of the bury. I would also like to see how a double (or triple) fisherman's knot holds up, since that is usually the alternative to a brummel in an eye-to-eye.

+1 for seeing how the double fisherman's will do

 

[moray]

...Do you have any intention of doing a buried brummel with a 6" tapered bury like you would do on an eye-to-eye? They all claim the taper is very important because otherwise it breaks at the end of the bury. I would also like to see how a double (or triple) fisherman's knot holds up, since that is usually the alternative to a brummel in an eye-to-eye.

As far as I know, it always breaks at the end of the bury, taper or not. I probably should test one normal eye-to-eye sling with Brummels, though I am quite sure it will break at the end of the bury, and since the splice won't pull apart, the Brummel will never deploy.

Good suggestion about the knots. I have 100 ft of 5/16 Tenex on order. This should be enough for about 25 experiments of various sorts, so I am open to suggestions. One obvious one is to tie an overhand knot right in the middle of a sling. It can't roll out; it can only break. Strengthwise will it be worse than a Brummel?

 

[ddhlakebound]

Nice work Moray.

Keep it up, this is a goldmine of learning info, and much appreciated.

I too would like to see a double and triple fishermans tested to failure.

Have you thought of publishing these tests in book form later on? I'd buy.

Anyway....thanks for the effort, expense, and knowledge that you're sharing with us.