Minimal Cost Stainless Rap Anchor

Dang Eli, again coming through with solid advice. I'll test the rope twisting before placing the anchor. I like vertically aligned anchors - seems superior in most scenarios. 

Jim - these are sweet. I'll have to get a few. Though the website use of the term strain instead of strength is worrisome since strain is a dimensionless measure of deformation and nothing directly to do with strength. 

Jim do you need to use a 10mm drill bit with those bolts?

http://team-tough.com/product/10mm-x-80mm-mechanical-wedge-bolt/

bttrrtRock wrote:

Jim - these are sweet. I'll have to get a few. Though the website use of the term strain instead of strength is worrisome since strain is a dimensionless measure of deformation and nothing directly to do with strength. 

I can pretty much guarantee you that Jim knows quite a bit more about engineering than you do.  I think the word strain is used differently by the Brits.

Got it, never-mind. The answer is yes.

http://team-tough.com/bolt-drill-hole-sizes/

Ken, I don't think Jim would have taken my comment as a threat to his engineering knowledge but rather a correct description of inaccuracy on the website he referenced. 

For future reference however I am a practicing mechanical engineer and have practical knowledge and experience regarding stress, strain, breaking strength, yield strength, working load limits, modulus, fatigue, corrosion, welding, stress concentrations, manufacturing defects, quality control testing and well... engineering. And I'm glad Jim is vocal about many of these subjects.  

bttrrtRock wrote:

Jim - these are sweet. I'll have to get a few. Though the website use of the term strain instead of strength is worrisome since strain is a dimensionless measure of deformation and nothing directly to do with strength. 

Well yes, it´s strictly innacurate but colloquially we use it all the time. Nobody has complained before!

Jonathan Awerbuch wrote:

Jim do you need to use a 10mm drill bit with those bolts?

http://team-tough.com/product/10mm-x-80mm-mechanical-wedge-bolt/

I could be wrong but I recall reading that the difference between 10mm and 3/8" was so small that it didn't make a difference. The point was that the allowable tolerance of diameter above or below 10mm was greater than the difference between 10mm and 3/8". 

The logic was that, if that small of a size difference mattered, then you would find 3/8" bolts that wouldn't fit into hole drilled by a 3/8" bit. Jim, you got any info on this?

eli poss wrote:

I could be wrong but I recall reading that the difference between 10mm and 3/8" was so small that it didn't make a difference. The point was that the allowable tolerance of diameter above or below 10mm was greater than the difference between 10mm and 3/8". 

The logic was that, if that small of a size difference mattered, then you would find 3/8" bolts that wouldn't fit into hole drilled by a 3/8" bit. Jim, you got any info on this?

You are wrong.  Forcing a 10mm wedge anchor into a 9.5mm (3/8") hole  is a good way to damage the clip and embed it into the cone enough to prevent adequate expansion.  

You might "get by" with it in most cases with a new bit in soft rock, but it is a problem and irresponsible. In hard rock or with an old bit, you have a very high probability of this issue.  It's sketchy. I think this was the cause of a much discussed pulled wedge bolt issue at the New a few years ago.

Jim - sounds like a cultural misunderstanding that only a geek like me would misconstrue. I do harbor a bit of distrust regarding strength qualifications, validations and quality control testing so the usage stood out to me as suspicious. Thanks for the recommendation. 

dnoB ekiM wrote:

You are wrong.  Forcing a 10mm wedge anchor into a 9.5mm (3/8") hole  is a good way to damage the clip and embed it into the cone enough to prevent adequate expansion.  

You might "get by" with it in most cases with a new bit in soft rock, but it is a problem and irresponsible. In hard rock or with an old bit, you have a very high probability of this issue.  It's sketchy. I think this was the cause of a much discussed pulled wedge bolt issue at the New a few years ago.

Good info to repeat -- this is what I've heard as well. What is a good source for 10 mm SDS+ bits?

Mike Slavens wrote:

-304 vs 316, UIAA is recommending 316 as a minimum.  If you're going to pay for SS maybe just get 316

Just to clarify...  Yes, the UIAA is recommending 316 over 304.  

One reason is that 316 generally has better corrosion resistance than 304, but that difference may not be significant for climbing bolts.  More field data is needed.  Secondly, 316 is cheaper in Europe because their construction industry standardized on it a long time ago.   

On this continent, the industry standardized on 304 and therefore 304 is usually much cheaper than 316.   And in most climbing situations you'd be hard pressed to see a difference in the rate of corrosion between the two.

For these reasons, the Access Fund recommends 304 stainless.

eli poss wrote:

I could be wrong but I recall reading that the difference between 10mm and 3/8" was so small that it didn't make a difference. The point was that the allowable tolerance of diameter above or below 10mm was greater than the difference between 10mm and 3/8". 

The logic was that, if that small of a size difference mattered, then you would find 3/8" bolts that wouldn't fit into hole drilled by a 3/8" bit. Jim, you got any info on this?

I´ve no experience whatsoever with 3/8" rock anchors, Europe has been metric since the 1970´s.

However the "logic" is wrong, all nominal 3/8" bolts will fit in all holes drilled by a 3/8" bit as the smallest size of bit is 0.390" and the shaft of a 3/8" bolt is also undersize.

For 10mm bolts the drill measures 10.6mm and the bolt shaft is 9.8mm.

Personally I can´t imagine you could ever get a 10mm bolt into a 3/8" hole unless you were just driving it into sandstone in which case you didn´t need to drill a hole in the first place..

Put one of Titt's hangers on top bolt and a regular CT/Fixe hanger and quicklink on bottom bolt.

(2) SS 3/8" x 3 wedge  $2ea

(1) SS Titt Hanger $4

(1) SS Climbtech Hanger $3

(1) SS 5/16 QL $4

Total Anchor: $15

Jim Titt wrote:

I´ve no experience whatsoever with 3/8" rock anchors, Europe has been metric since the 1970´s.

However the "logic" is wrong, all nominal 3/8" bolts will fit in all holes drilled by a 3/8" bit as the smallest size of bit is 0.390" and the shaft of a 3/8" bolt is also undersize.

For 10mm bolts the drill measures 10.6mm and the bolt shaft is 9.8mm.

Personally I can´t imagine you could ever get a 10mm bolt into a 3/8" hole unless you were just driving it into sandstone in which case you didn´t need to drill a hole in the first place..

Cool thanks for the correction. So a 10mm bolt won't work in a 3/8" hole, but what about the other way around? Work with a sleeve bolt but not a wedge bolt? Neither?

eli poss wrote:

Cool thanks for the correction. So a 10mm bolt won't work in a 3/8" hole, but what about the other way around? Work with a sleeve bolt but not a wedge bolt? Neither?

Curiously enough I was asked this last week by a customer in Brazil who was mistakenly given a load of 3/8" wedge bolts under the impression they were 10mm. Never having seen a 3/8th bolt (apart from the ones I´ve clipped in the USA) it´s something I´ve no experience with but would imagine the results could be disastrous.

bttrrtRock wrote:

17.7 kN in shear and 12.2 kN in tension. Seems pretty solid for vertical or less than  vertical bolts eh? 

More like total garbage. That's half the UIAA minimum strength requirement of 25kN shear and 20kN tension and well under what a quality 3/8" bolt will hold. The Hilti KWIK 3 3/8" wedge bolt is rated for 35kN tension and 22kN shear. However, as Greg said the stainless steel version will put you back in the Power-Bolt model, not the Power-Bolt+ model, and the Power-Bolts are much, much stronger (and better).

At the end of the day if you want a quality stainless steel anchor there is an entry barrier and there is really no way to get it priced any lower while still maintaining a minimum standard of quality. Your cheapest bet for a stainless anchor that is solid and wont twist the rope is going to be the vertical anchor. They come in a few different forms including the option that Jason Todd posted.

bttrrtRock wrote:

~ Cost

304 Stainless 3/8 Power Bolt $4 

Stainless Fixe Hanger $3

316 Stainless 3/16" link $2

316 Stainless 5/16" chainlink $1

Total Rapstation = $20

Would you rap on two of these? Why or why not?

Those chains need to meet to a single point otherwise they are going to twist the absolute shit out of the rope when lowering. It's a huge inconvenience and major ghetto rigging to use an anchor like that. If you're looking to save on material costs use the European-style vertical anchor. Also, 3/16" is too small. The minimum diameter you should use is 5/16".

eli poss wrote:

I could be wrong but I recall reading that the difference between 10mm and 3/8" was so small that it didn't make a difference. The point was that the allowable tolerance of diameter above or below 10mm was greater than the difference between 10mm and 3/8". 

The logic was that, if that small of a size difference mattered, then you would find 3/8" bolts that wouldn't fit into hole drilled by a 3/8" bit. Jim, you got any info on this?

You need to use the correct drill bit. 10mm bit for a 10mm anchor and 3/8" bit for a 3/8" anchor. I've seen people bend over 10mm bolts trying to get them into 3/8" holes and I've seen 12mm anchors pull out by hand when placed in 1/2" holes. The tolerances on expansion bolts are somewhat tight and the hole size is critical to the performance of the bolt. As Jim mentioned, bolts are able to work with small tolerances between different bit manufacturers, but using a different size all together is unacceptable.

Regarding finding 10mm bits, they are pretty easy to find. Do a Google search. There are plenty of places that sell them including Amazon, eBay and just about everywhere else. Petzl and Fixe both sell them although they can be found cheaper elsewhere.

More like total garbage.

Just for clarification - I picked the worst case concrete strength scenario in the chart (2500psi = 17.2N/mm^2 = not the strongest rock). In any 8000psi concrete the listed tension strength for PB+ is 19.7kN and for shear is 17.7kN.

Not saying they meet UIAA, not saying they aren't worse than other options - just saying based on strength ratings "total garbage" is likely not accurate - though I'd be open to a evidence or experienced based argument. 

On another note: Thanks for all the info and opinions folks. Hopefully the snow here holds off so I can get back out there!

20 kN wrote:

More like total garbage. That's half the UIAA minimum strength requirement of 25kN shear and 20kN tension and well under what a quality 3/8" bolt will hold. The Hilti KWIK 3 3/8" wedge bolt is rated for 35kN tension and 22kN shear.

Why would the strength requirement be different in tension than in shear? Especially when the 20kN figure puts the bolt weaker than the 22kN requirement for biners and slings. Or perhaps the better question is why do quickdraws have to hold 22kN if the bolt it's clipped to holds less and any gear or pin it could be clipped to will also hold less?

eli poss wrote:

Why would the strength requirement be different in tension than in shear? Especially when the 20kN figure puts the bolt weaker than the 22kN requirement for biners and slings. Or perhaps the better question is why do quickdraws have to hold 22kN if the bolt it's clipped to holds less and any gear or pin it could be clipped to will also hold less?

It´s kinda logical but on the other hand fairly irrelevant. Basically it´s impossible to visualise a scenario where a climber could possibly take a full-on FF2 onto a bolt installed vertically under a roof. The standards are partly based on theory but also partly on what works in practice, we know that gear that holds x doesn´t usually fail in normal use, if failures are seen the standards guys jerk it up a bit to x+ something.

The actual numbers (25kN) are basically chosen to remove 8mm bolts from use as they don´t achieve this and are known historically not to be trusted.

Wedge bolts actually hold the same in every direction in (good) rock as the loading is different the one used in the construction certification tests.