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Russ Walling
Social climber
Bishop, Ca.
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Feb 27, 2003 - 01:04pm PT
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>>Maybe we should define failure rate. Did the collared bolts break at a significantly lower force? >>
Ok... I'll define it. Set A (collared) all broke at the junction. Failure rate 100%.
Set B (threaded) I remember universal massive bending before failure, but with enough force, all broke. Failure rate 100%
That being said, I use the the threaded ones.
>>I try to place them so that the threads are buried and the collar is well seated in the hole. I don’t know how much this helps with respect to leverage on the specified weak point, i.e. the collar/thread junction, but I do see your point.>>
A spot of theory: I tend to think the damage is done while driving the rivet into the hole. Something happens at the junction to weaken that point. The collar area is more rigid than the threads, and during the pounding there is deformation at the junction that severely weakens the rivet. That junction is subject to a force concentration that it never recovers from.
>>A fully threaded bolt will bend evenly in an arch as where a collared bolt will be more rigid and snap at the junction. Based on what I have chopped, this appears to be true.>>
Ok... you have seen it in action, and we have tried to describe why it happens. Fact: the collared ones break at the junction. Threaded ones bend plenty.
>>I still think that machine bolt rivets with a smooth collar are better. >>
Hmmmmm...... is this because of the threads "cutting" theory on rivet hangers (still unproven) or you just like dicey rivets?
>>But then again, I never give up… >>
Maybe you should..... you said it yourself, "The collared ones broke a the junction".
Side note: The force needed to break any of these is probably well above any load we put on them under normal use. So, unless you are ripping onto rivets, either one should work well over its lifetime. I am more worried about rivets coming out of the hole than I am about them shearing off or cutting the rivet hanger. YMMV
Russ
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mike hartley
climber
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Feb 27, 2003 - 02:24pm PT
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"Outside of rivets, what options exist for hand drilled belay or protection bolts that can be placed in a reasonable amount of time?"
Outside of a chunk of metal or bat hooks (not for belays of course!) the only option I know of is a removable bolt. The 1/4" ones require a very shallow hole that is quick to drill - not that much deeper than a bat hook hole. No worries about degradation over time either. I've only tested the 3/8" (not 1/2") ones and they are quite strong even in straight pullout (~2000 lbs in less than ideal granite). I know that's what I'd use instead of a rivet ladder.
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jbur
climber
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Feb 27, 2003 - 02:39pm PT
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What about stainless vs. grade 5 machine bolts? Anyone done any testing about the strength difference?
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Minerals
Social climber
The Deli
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“Ok... I'll define it. Set A (collared) all broke at the junction. Failure rate 100%.
Set B (threaded) I remember universal massive bending before failure, but with enough force, all broke. Failure rate 100%”
So, they all broke. What does that tell us? How did their strengths compare? Was one type stronger than the other? If they are both about the same strength, yet deform and break differently, then what is the difference between the two types, other than possible cable cut-age? (This problem is negated by the use of RP hangers (which are much stronger than cable rivet hangers and won’t pop off the rivet when clipped with a biner)). Hey Russ, how about manufacturing keyhole hangers? The RPs are spendy and the Pika ones suck.
The following info is from testing done by John Middendorf, Jim Bridwell, and others. I’m not sure of the exact year but the copy I have is stapled to a copy of John’s bolting article which appeared in the February 1988 issue of Climbing.
5/16” Machine Bolts, coarse thread,
Shear Tests:
Placed snug to hanger:
Grade 5, 1 ¼”, SMC 3/8” hanger, Rawl # 14 bit – 3781 lbs., pulled out.
Grade 2, 1 ¼”, SMC 3/8” hanger, Rawl # 14 bit – 2754 lbs., sheared.
Grade 5, 3/4”, SMC 3/8” hanger, Rawl # 14 bit – 2729 lbs., pulled out.
Grade 5, 3/4”, RP keyhole hanger, Rawl # 14 bit – 2493 lbs., pulled out, hanger deformed.
Placed ½ way in:
Grade 5, 1 ¼”, SMC 3/8” hanger, ¼” bit – 2617 lbs., pulled out.
Grade 5, 1 ¼”, SMC 3/8” hanger, ¼” bit, threads mashed – 1489 lbs., pulled out.
Comments-
“Unbelievable”
I presume that the bolts tested were the fully threaded type, but I’m not sure; nothing is specified. John later told me that he thought that the collared bolts are a better idea. My partners and I have used this type of rivet extensively, including at belays. Some of my solo belays consist of a 3/8” bolt and a 5/16” machine bolt rivet.
“A spot of theory: I tend to think the damage is done while driving the rivet into the hole. Something happens at the junction to weaken that point. The collar area is more rigid than the threads, and during the pounding there is deformation at the junction that severely weakens the rivet. That junction is subject to a force concentration that it never recovers from.”
Agreed. Metal fatigue. Over-driving a rivet can weaken it. To chop a rivet of this type, I have to wail on the thing and bend it back and forth several times before it snaps. If the placement is less than ideal, the bolts will pull out, rather than snap.
“>>I still think that machine bolt rivets with a smooth collar are better. >>
Hmmmmm...... is this because of the threads "cutting" theory on rivet hangers (still unproven)…”
Yes. I will test this ‘theory’ next time I do some testing. Have you had a chance to test it?
“…or you just like dicey rivets?”
Yes and no. I think Zamac or Zmac (whichever) rivets are garbage but 5/16” machine bolts are bomber for their intended purpose and are much easier and quicker to place than other bolts, while drilling on the lead (aid climbing). I guess it comes down to style – only 5/16” rivets on lead; anything goes at belays (be it good or bad).
“>>But then again, I never give up… >>
Maybe you should..... you said it yourself, "The collared ones broke a the junction".”
Failure mode is irrelevant if the two bolt types are of equal strength (i.e. placement strength).
I’ll try to write up some of my test results.
jbur wrote:
“What about stainless vs. grade 5 machine bolts? Anyone done any testing about the strength difference?”
Stainless rivets were used on the FA of Tribal Rite. While cleaning one of the ladder pitches, Kirk pulled out a rivet with his fingers. Cool. The hole has since been filled with a 3/8” bolt. Either the hole/bit size was incorrect or the metal type didn't work properly.
I’m not sure if stainless alloys have the appropriate strength/deformational characteristics to be used as a hammer-in rivet. Anyone know? The 1/4" buttonhead may be a better idea for long-term use, due to the spring action inherent to their design, but require more effort and time to place - something that a climber may not be willing to expend.
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Russ Walling
Social climber
Bishop, Ca.
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>Failure mode is irrelevant if the two bolt types are of equal strength. >
Maybe I'm not clear enough....
I say the smooth collared rivets are weaker ie: break easier, than the all thread models.
I do not have a giant sample set analysis, dnyomometer failure testing, or a 900 page thesis on this. This is from personal experience, half ass testing, and hearsay.
At some point I'll set up some test stuff to find out for sure.
Whaddya think about testing these scenarios:
threaded machine bolt, hanger
threaded machine bolt, rivet hanger
threaded machine bolt, tie off
unthreaded machine bolt, hanger
unthreaded machine bolt, rivet hanger
unthreaded machine bolt, tie off
Machine bolt grade 8, same as above
Rawl buttonhead
Only going to test shear. Maybe 3 of each set. Test to failure.
Russ
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Minerals
Social climber
The Deli
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That sounds like a good idea. Maybe throw some Fixe 5/16” buttonheads in for the hell of it.
What type of testing equipment to you have, or will you have? I’d be psyched to help out with the testing if possible.
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WBraun
climber
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Hey Russ
I'll bring the Le Mans over with trunk full beer and we'll yard out bolts all day with a slack rope tied to the bumper like the old days back in C4, eh? WB
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Russ Walling
Social climber
Bishop, Ca.
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As you know Werner.... all my test data is based on the LeMans tests. Love that car.....!
Russ
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Minerals
Social climber
The Deli
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Yeah, I've heard about these tests in the old days. Wasn't Cosgrove involved? Do you measure the strength of the bolt by how far past the car the bolt flies; i.e. the bolt strength is directly proportional to the distance traveled? Can't believe you never broke a rear windshield...
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Slabby D
Trad climber
B'ham WA
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This thread is extremely informative. Thanks for all the good info. Still interested in all the options for hand drilling anchors on alpine rock.
A relatively-local shop sells Hilti 1/4" x 1 3/4" expansion bolts as rock pro. Hilti website how no strength data unfortunately. Anyone have any opinions/experience with Hilti hardwear? How about 1/4" expansion bolts in general? Thanks.
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Minerals
Social climber
The Deli
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Considering the fact that 1/4" expansion bolts may be threaded, they will be weaker than a solid 1/4" buttonhead.
Like Russ said, 1/4" x 1 1/2" buttonhead. Period.
A 1/4" sleeve expansion bolt will have a bolt with a diameter of something between 1/8" and 3/16" - sounds like Harding's old 3/16" bolts. Yikes!!!
Also, buttonheads can be pulled (i.e. replacement); threaded expansion bolts cannot.
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