26 May 2012

Crampons: do they break?

Black Diamond have posted an excellent article on crampons - it talks about choosing materials, eg. stainless steel vs chromoly steel vs aluminium, and about fatigue testing, and selecting the right crampons for your boot and your activity.

A few years ago they started using stainless steel instead of chromoly steel. Both chromoly and stainless contain chromium as an alloying element, but chromoly contains less than 1% chromium, whereas stainless steel contains at least 10.5%. This means that chromoly rusts more easily than stainless. There are also other material property differences. Ultimately they decided that stainless was better suited to the task as they found it was more wear resistant, didn't pick up as much snow when walking, and didn't rust as much.

They also refer to a BMC leaflet about care and mainteneance - the interesting point which is confirmed by their tests, is that if you have flexible boots you should wear flexible crampons, and stiff crampons for stiff boots. In their tests the fatigue life of crampons was reduced by roughly up to 80% when there was a mismatch between crampons and boots. If you have soft boots make sure you replace those rigid steel cross bars in your crampons with a flexible one, it could increase the lifespan of your crampons considerably!

Image from Black Diamond article

20 May 2012

Are knotted Dyneema® slings good for climbing?

DMM have carried out some very interesting static load and drop-tower tests to find out the strength of knotted Dyneema® slings.  Dyneema® is normally found in stitched slings - DMM wanted to find out how slings would fare if made by tying your own knot in a piece of  Dyneema® from a reel.

As the DMM article mentions, Dyneema® is actually just a brand name for Ultra-high-molecular-weight polyethylene (wikipedia) which is a type of polythene (wikipedia) which has very long molecules, which makes it stronger and tougher than polythene with shorter chained molecules. The size of the molecules is key because polythene with shorter molecules will have massively different mechanical properties.

Dyneema® also has a relatively low melting point (between 144 and 152C) and also has a 'low' coefficient of friction. DMM suggests that heat in the knot during dynamic testing could explain why the knotted sling failed at significantly lower loads than the sewn slings. DMM believes this is supported by the result that frozen and wet knotted slings were stronger than dry ones - perhaps suggesting that the water/ice in the knot helps to reduce heat build up.

Based on the results of the tests, DMM strongly recommend against using knotted  Dyneema® slings as they consistently failed at lower loads compared to sewn counterparts.

Take a look at the full article here. The video gives a good overview.

Image from DMM article

12 May 2012

Bosavi headlamp on kickstarter

Bosavi is a nifty looking headlamp featured on the kickstarter fundraising website, it is rechargeable with a lithium battery. It appears to be similar in a lot of ways to the Petzl Tikka headlamps when used with a rechargeable Core battery, but there a few interesting differences. It is smaller and lighter than the Tikka XP2 with a Core battery (the most comparable Petzl lamp), the packaging for the lamp is designed to turn into an origami lantern, and it has a bike adapter for fitting to a bicycle handlebar.

It has very similar lighting modes (red light for night vision, diffuse white light, two levels of high brightness spot light, strobe safety light, and a high intensity 110 lumen boost mode) to the Tikka XP2, similar brightness on the normal mode (both 60 lumen), similar battery life (70 hours on low setting for Bosavi, ~80 hours for Tikka XP2 on low).

So far it is fairing well on kickstarter - as of 12 May 2012, after around 10 days it has raised roughly $18,000 of its $20,000 target, and there is still 35 days to go. It seems a given that it will raise its target - and quite likely that it will raise significantly more. The minimum amount you need to pay in order to receive one of the lamps is $65 (+$15 for international shipping). It is also likely that UK residents will pay significant import/postal costs, in the past I have been charged £20 for an $80 item from the US.

Video from Bosavi kickstarter page

11 May 2012

BMC Helmet campaign and helmet booklet

Since the beginning of the year The British Mountaineering Council has been running a helmet awareness campaign to "challenge views on helmets, and to encourage you to re-examine your reasons for wearing one or not". They have produced a booklet on helmets to help people make an informed decision.

The BMC emphasizes that in climbing and mountaineering it's important for each individual to make their own decisions when it comes to deciding what risks are personally acceptable.

Image from BMC website