Failure point on Micro nuts

Where/how do they fail? Is it just too much force on too small an area of rock? The metal wire must be rated for more than 2kn, it’s the same metal, so what’s the weak point aside from the higher likelihood of having the rock fall apart?

Been a long time since I have whipped on micro nuts but given their size and the material (often brass) they can deform easily with small contact areas. Seems I remember the wire shearing/pulling through some. 

Deforming metal, breaking wire, crushing rock

Rock broke, 2 out of 2.

https://www.ukhillwalking.com/forums/gear/imp'srp's_or_dmm_peanutsmirco_wallnuts-366366

Copied from the link above, the short answer from what i understand is: the wire gage determines the rating (in a perfect placement in strong rock the wire itself is the limiting factor for strength). But the surface area of the nut on the rock and the rock strength will affect whether or not the placement fails due to the wire breaking, the rock breaking, or the placement popping.

Duncan,

I should just clarify a couple of points which are becoming a bit of an urban myth.

Small soldered nuts are generally stronger than the equivalent size of swaged nut because you can get a wider diameter wire into the head of the nut, not because soldering creates a stronger join or because it removes a tight bend as the wire goes around the top of the nut. This advantage decreases as the head size increases.

Thus use a 2.00mm wire and you can get circa 4-5kN out of a nut, but if you can use a 2.5mm wire you can get 7 - 8kN.

This is where the IMPS/Brass Offsets/RP's win in sizes 1+ 2 - on an IMP/RP size 2 you can get a 2.00mm wire in a miniscule head and achieve 5kn. A swaged nut of the same size (Wallnut 0) has to use 1.5mm wire and the strength drops to 2+kN.

However jump up slightly in head size and you can get 2.00mm wire into a swaged head. The Wallnut 0.5 uses 2.00mm wire and is only very slightly wider than a IMP/RP 2 and is conservatively rated at 4kN. In a real world situation it is as/almost as strong as an IMP/RP 2

On IMPS/Brass Offsets/RP size 3 the advantage is further decreased because you can't get a 2.5mm wire into the base of the head, but on the Wallnut 0.75 the head is now big enough to take a 2.50mm wire when swaged and also has plenty of metal to stop it pulling through placements. Thus the Wallnut 0.75 (same width as a IMP/RP 3) going forward will use 2.50mm wire and be conservatively rated 6kN - stronger than an IMP/RP 3.

There is a table of micro nut strengths/dimensions at  rockclimbingcompany.co.uk/L…;in the Nuts and Slings section for fellow gear freaks.

It also needs to be remembered that the swaged micro nuts (i.e. DMM Micro Wallnuts) offer greater, surface contact which is an important consideration as a common mechanism for failure in real life is the nut pulling through the placement. Once again the devil is in the detail - using a tougher 7075 aluminium alloy nut as on the DMM Micro Wallnuts gives extra holding power compared to a softer 6000 series alloy.

Add to this the fact that standard steel wire as used on swaged nuts generally has a higher tensile strength than the stainless steel wire that must be used on soldered nuts.

On the other side of the coin IMPs/RPs and Brass Offsets will fit where the wider swaged alloy nuts won't go....

Each nut has its own strengths and weaknesses and the key thing is to understand them.

There is no perfect micro wire although an IMP/RP 2 comes pretty close; but a micro wire rack that includes IMP/RPs 2, 3 and 4, Brass Offsets 2, 3 and 4 plus Micro Wallnuts 0.5 and 0.75 is a really good starting point.

I hope that helps a bit

Simon

DMM

Aluminum micro nuts (or any nut that is not brazed like brassies) fail at the bend on top of the stopper. The tight bend weakens the cable, and is its weakest point. Brassies of smaller sizes will be stronger because the wire is swaged then soldered or brazed, alleviating the weak point in the system. Cams also will break at the thumb loop as the bend in the wire creates the weakest part in the system

The nuts i have seen failed because of the rock disintegrating.

Thanks for all the responses. I totally understand rock failing but 2kn really isn’t a large amount of force. It’s odd to think you can’t make a wire stronger than that in today’s day and age. I understand the bend in the wire compounding the force, but there’s so many strong material out there, if it’s just the metal wire preventing them from being stronger is there not a market for a slightly more expensive material to create stronger micros? It’s got to be possible, I understand maybe not being economical but I’d expect an option if it’s something that simple to make the placements stronger. My cams at 6kn vs 8kn vs 12kn don’t make much of a difference to me, but 2 vs 5kn is a big difference in usability

Zachary Zwickwrote:

Thanks for all the responses. I totally understand rock failing but 2kn really isn’t a large amount of force. It’s odd to think you can’t make a wire stronger than that in today’s day and age. I understand the bend in the wire compounding the force, but there’s so many strong material out there, if it’s just the metal wire preventing them from being stronger is there not a market for a slightly more expensive material to create stronger micros? It’s got to be possible, I understand maybe not being economical but I’d expect an option if it’s something that simple to make the placements stronger. My cams at 6kn vs 8kn vs 12kn don’t make much of a difference to me, but 2 vs 5kn is a big difference in usability

2Kn is the force in line with the nut (usually down).  As the nut is driven down, the force exerted on the rock is much higher due to the small surface area.  You can nerd out on the science on Youtube but if you've ever done any masonry with real stone, you can beat on most of it with an 8lb hammer and it'll have a few chips come off, but that spear head chisel will go through it like butter.  

See if the HighNotToHighline dudez have been breaking these. If anything it's wonderful entertainment when you're... uh: altered.

I saw a lot of pro but nothing with nuts. Regular or micro. Maybe I could ask them. It’d be an interesting test for different sizes ignoring rock quality. I wouldn’t be surprised to see them hold hugely higher than rated forces

I’ve had a couple blow on me and both were because of the wire breaking (both in good Eldo/flatiron sandstone). The failure point (in both instances) was below the nut on the cable. I suspect in a spot where the cable could run against the edge of the crack. I should note both were fixed though and likely had been there for a few years

Zachary Zwickwrote:

I saw a lot of pro but nothing with nuts. Regular or micro. Maybe I could as them. It’d be an interesting test for different sizes ignoring rock quality. I wouldn’t be surprised to see them hold hugely higher than rated forces

Hmm, makes sense - as who would build a highline anchor with nuts. But hopefully they'll get to it. SOMEONE SEND THEM SOME NUTS TO BREAK!

A friend once excitedly told me how he’d discovered how little force you actually put on pieces once you have enough rope out. He went on to put up many hard routes featuring micro gear.

Getting hung up on gear stats is common, my first rope was an 11mil monster because I didn’t understand how fall ratings worked.

Play around with micro nuts, learn the strengths and weaknesses. Personal experience is your best resource.

And don’t go taking high factor whips in consequential terrain if the only thing keeping you off the ground is the smallest brassie on your rack, obviously!

Long Rangerwrote:

See if the HighNotToHighline dudez have been breaking these. If anything it's wonderful entertainment when you're... uh: altered.

They did a episode on ball nuts.  The smallest kept busting the rock.  The others broke wires.

Zachary Zwickwrote:

I saw a lot of pro but nothing with nuts. Regular or micro. Maybe I could as them. It’d be an interesting test for different sizes ignoring rock quality. I wouldn’t be surprised to see them hold hugely higher than rated forces

A strange concept, the manufacturers have already tested them.

Jim Tittwrote:

A strange concept, the manufacturers have already tested them.

True of course. But there’s a lot of reasons why you’d stick to a lower official rating. The amount of force I’d tell someone they can 110% put on it, vs what most of the non-aid placements would be of “I hope this holds because it’d make it a nicer fall but I won’t die either way placements. At least that’s how I’d hope they’re being used. 

Long Rangerwrote:

Hmm, makes sense - as who would build a highline anchor with nuts. But hopefully they'll get to it. 

They started out doing big wall climbing videos as well and the guy who runs the channel has a video about big wall tips so I’m sure micronut placements would be interesting to them too.

Zachary Zwickwrote:

True of course. But there’s a lot of reasons why you’d stick to a lower official rating. The amount of force I’d tell someone they can 110% put on it, vs what most of the non-aid placements would be of “I hope this holds because it’d make it a nicer fall but I won’t die either way placements. At least that’s how I’d hope they’re being used. 

The manufacturers send them for independent testing, they could chose to use a lower rating than they actually achieve but there's no reason why they should or would, bigger numbers sell better.

Zachary Zwickwrote:

They started out doing big wall climbing videos as well and the guy who runs the channel has a video about big wall tips so I’m sure micronut placements would be interesting to them too.

I think they did one w/hooks. someone send these guys some micronuts!