UKC

i sometimes climb short routes alone, protected by a petzl ascender on a fixed top-rope. i have always been slightly nervous when the ascender moves around onto the sides of the (HMS) krab. more recently i have been using a belaymaster krab - the one with the plastic clamp gizmo which locks the sleeve closed. this is better as the top corners are squarer, and the ascender hardly ever moves around them. rarely it does happen though, and it looks quite alarming.

1. should i be concerned?
2. is there a better krab that i could use?

In reply to helix: you could try using a maillon instead of a crab- bit more awkward to connect to the harness but no issues about cross loading.

In reply to helix: i would say dont use an ascender as if you shock load it it could tear through the rope because of the teeth,
either that or a clever troll device is available

In reply to gear boy:

http://en.petzl.com/ProduitsServices/B17B18ASCBASB17500%20080798.pdf

Bottom of page 2

An ascender is fine used with just a krab between the device and the harness as there is no room for a shock load.

Use an oval krab not an hms.

In reply to helix: Elastic bands are useful for holding krabs in the correct orientation.

In reply to gear boy: I would agree with Gear Boy, despite the very short distance you may come on to the ascender from, the teeth are pretty agressive, and maybe it would be best to buy a shunt just in case.....

In reply to alan wilson: why don't you get a job with Petzl. You obviously know more than they do, maybe you could correct thier instructions for them!!

thanks guys.

i have used elastic bands and tape before but they seem to rip off too easily. re tearing the rope, i cant quite see that happening, i am using a fairly sturdy static rope (a sandstone rope). perhaps an oval krab is the answer.

In reply to helix: A karabiner can withstand a cross-load of 7kn or higher. A comparable load to what I think you will be doing would be a top roping fall which will exert roughly a 2kn force or less on the top anchors.

Even in a lead fall it is rare to exceed 7kn. Therefore I wouldn't worry about it if I were you!

In reply to Craig Geddes:An HMS is bad because it may move as it is loaded and therefore incorrectly load the ascender.

In reply to styman: Loading the ascender wrong is a different matter - sorry. I had assumed that the post was about the loading of the biner.