Saturday, 6 June 2009

Dyneema is strong...very strong

The DMM Torque nuts are almost ready for release and have been going through the final stages of testing and certification.

I was surprised to discover that the Torque Nuts have been designed to reach their breaking strengths and then break in two different ways. The smaller nuts reach their rated strength of 14kN and then it is the dyneema webbing that breaks.

However the two largest sizes have been designed so that it is the metal chock that breaks/deforms - in this way the weight of the chock can be kept to a minimum. The 8mm dyneema webbing is actually stronger than the extruded aluminium nut!

The image to the left show a Torque nut that has been tested and was deformed by the webbing - the dyneema webbing was perfectly fine and was then seperately tested before breaking at 24kN.

In another test the dyneema actually pulled through the top holes in the nut at 17kN!

Apparently one of the key processes to getting the nut to behave in this way is machining very smooth radiuses on all the edges of the internal holes.

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