Saturday, 22 August 2009

DMM Torque Nuts - Why they work better...

There was an interesting conversation going on at DMM the other day about the new Torque nuts and about why they worked better than other large hexcentric nuts. The following is from a letter that the Torque nut designer, Graham Desroy, sent to Toby at UKC. Toby is reviewing the nuts.

"When I started the project I started with a blank canvass with the objective of designing a large nut to compete with the Wild Country Rockcentrics.

Obviously being old and having worked for Troll and HB prior to DMM I have gained a few pointers on the way. Interestingly my old Chouinard Hexentrics worked very well in the camming orientation with good expansion. The HB Quadratics despite looking somewhat odd offered an even better expansion in the camming orientation - Hugh was a very clever designer. The Wild Country Rockcentrics however scored because they looked a more attractive shape even though they didn't/don't perform as well.

The reason for this is that Wild Country changed the angles on the side and introduced a more continuously curved shape, especially on the convex sides. By doing this you lose an important pivot point from which the cam action is instigated.

What the Torque nuts achieve is a combination curves and pivot points which allow the nut to cam correctly. Also by carefully calculating the relative side angles the expansion range is increased. The result is a nut that not only looks good but maximises the camming expansion - this is especially noticeable in horizontal placements.

Attached is a spreadsheet which has the relevant measured data concerning the camming expansion and total range of each nut for Torque nuts and Rockcentrics. You will notice that Torque nuts have a significantly better camming expansion than Rockcentrics and also that our camming expansions overlap between sizes; Rockcentrics don't.

Also we achieve this in four sizes whereas Rockcentrics require 5 sizes.

The other major design advances are the trough in the upper face to protect the webbing.

Also the double slinging (Patent Pending) which allows the Torque nuts to be 'shorter' on the gear rack when 'doubled' compared to Rockcentrics, yet longer when extended into the 'single' sling mode. This not only makes the nut easier to carry but also saves on a quickdraw when extended. Following a trip to the Lewis sea cliffs last week I am just increasing the hole diameters very slightly as I speak as I want to improve the 'running' of the sling through the nut, - hence your sample set may be less smooth than future ones.

As regards strength we have rated all the Torque nuts at 14kn, whether the nut is used 'single' or 'double'. This is very conservative, some of the sizes are considerably stronger - it's all to do with wall thickness related to nut size and distances between the holes."

There is more information on placing climbing protection on my site:

1 comment:

Toby - Northern Light Blog said...

Should I get worried that you've read all my other emails as well!? :-)

I'm enjoying using the Torque nuts, the slings are a great design - although I haven't need to place them in horizontal cracks much yet so haven't fully tested out the camming possibilities.

Keep up the great work with all the excellent and clear gear articles, and best wishes from Helsinki!

Toby.