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Banquo
Trad climber
Morgan Hill, CA (Mo' Hill)
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Topic Author's Reply - Oct 28, 2010 - 09:49am PT
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Good morning knuckleheads!
Some have expressed surprise at the strength if the 1/4" SS wedge anchor but it doesn't seem unexpected to me because of how strong granite is. PLEASE NOTE that my quarried piece has not weathered and may be stronger than what you would typically find in the wild.
Anchor strength is limited by the bolt strength or the stone strength. The values published by bolt manufacturers are based on concrete strengths, usually compression strengths of 2000 to 4000 psi. This is typical construction concrete. High strength concrete can be 10,000 psi.
The tensile strength is also of interest. Engineers seldom test for the tensile strength of concrete because we generally assume it is zero in anticipation of cracks (did I tell you I sometimes teach design of concrete structures?). It is sometimes measured using a small beam (I've done this a few times) but the test is usually more trouble than it is worth. A more common cylinder splitting test results in the "Modulus of Rupture" (I've done this many times, it's cool how it works) which is larger than but related to the tensile strength. In actual practice, engineers usually just estimate the modulus of rupture as being the square root of the compressive strength times something between 3 and 8. I think the ACI code suggests 7.5(fc')^0.5 which results in:
Modulus of rupture for 2000 psi concrete 335 psi
Modulus of rupture for 4000 psi concrete 474 psi
Granite is a different material, good granite is much stronger than concrete and can have very high tensile properties. After doing a little research, I found a very cool old book in which the state of Wisconsin published material properties of stone from various quarries. Google "On the building and ornamental stones of Wisconsin" By Ernest Robertson Buckley, Wisconsin Geological and Natural History Survey, 1898. PDF versions available. On pages 390 and 391 they list the crushing strength of quite a few granite samples. They also tested a few for modulus of rupture with results on page 396.
Quarry granite compression strength 15,000 to 47,700 psi
Quarry granite modulus of rupture 2,700 to 3,900 psi
This indicates that for granite, the modulus of rupture is something like 300 to 500 times the square root of the compression strength. Granite is proportionally much stronger in tension that concrete.
I hypothesize that the shear strength of a split shank buttonhead will be very high since they are hardened steel. Greg Barnes sent me a few and when my load cell is ready, I'll publish some results.
You guys quit hypothesizing regarding topics about which you are ignorant.
"People who know only a little do not understand
how little they know and are therefore prone to error."
Alexander Pope.
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Steve Grossman
Trad climber
Seattle, WA
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Oct 28, 2010 - 11:35am PT
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The issue with split shaft anchors used in climbing applications isn't their strength when newly placed. They are plenty strong enough out of the box. Once water and time enter the equation then strength begins to diminish as the heavily stressed metal at the split point corrodes and fractures due to hydrogen embrittlement and other deletarious forms of accelerated oxidation.
Tortured metal does not make for good and lasting anchors. Use stainless steel and do everyone a favor!
As mentioned upthread, try your best to select a fastener that yields a bearing cross section that matches the hole diameter especially at the point of applied load from the hanger.
Greg- are you guys still using wedge anchors as the bolt of choice for your activities?
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bhilden
Trad climber
Mountain View, CA
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Oct 28, 2010 - 01:29pm PT
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Greg can answer Steve's question directly, but the bolts Greg sends me for my ASCA rebolting work have always been 5-piece Rawl (now called Power) bolts.
Bruce
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Majid_S
Mountain climber
Bay Area , California
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Oct 28, 2010 - 09:19pm PT
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The angle iron act as lever and its obvious that the red head will come out like that. why not try it with a real hanger and see what happens
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Greg Barnes
climber
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Oct 28, 2010 - 10:51pm PT
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Greg- are you guys still using wedge anchors as the bolt of choice for your activities? No, we haven't used stud/wedge bolts in many years (with rare exceptions). They are not removable for future rebolters. I'd say about 90% of our bolt use is 5-piece (Power-Bolts) in various sizes and lengths, 5% Fixe Triplex, and 5% glue-ins.
We do sometimes use 1/4 x 1.5" buttonheads plus washers for rivet replacement on walls. "Too bomber" is an occasional complaint, but they are removable.
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Clint Cummins
Trad climber
SF Bay area, CA
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Oct 29, 2010 - 12:20am PT
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Dan,
Sorry if my post suggested I was skeptical about the strength of the 1/4" SS wedge bolt you tested. What I meant was that I was pleased that you had informed me that there was 1/4" SS which was good! I had not previously heard of anything 1/4" SS that was very strong, so it is helpful to know about this option. (Although I drill 3/8" for my own climbs and for replacement, and recognize that drilling 1/4" splitshaft on lead and replacing with 3/8" is also good).
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cragnshag
Social climber
san joser
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Oct 29, 2010 - 12:59am PT
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OK professor, get out your hammerdrill. I've got plenty more 316 SS 1/4" wedgies for you to test. Better they get some use in your experiments than collect dust in my garage. I don't foresee any remote big walls in my future before little buddy hits grade school age... I'll bring some by on may way home from work.
Make sure to make the lip of the hole is a little cratered to simulate hand drilling on weathered rock. I bet they are stronger like this (combo shear and tension when bolt bends slightly at the lip) than with a sharp lipped hole where shear would be predominant. I took a picture of a newer button head (recycled, of course!) alongside the wedgie to give folks an idea of just how tiny these bolts are.
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Steve Grossman
Trad climber
Seattle, WA
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Oct 29, 2010 - 12:23pm PT
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Concrete screws are right out...don't even go there.
Greg- Glad to hear that you guys are not using wedge anchors anymore. I have another fastener system that may interest you that is much cheaper than Powers 5 piece. I have a small amount of testing still to perform myself.
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Banquo
Trad climber
Morgan Hill, CA (Mo' Hill)
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Topic Author's Reply - Oct 29, 2010 - 04:24pm PT
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Bad day of testing today.
Greg Barnes sent me some 1/4" anchors of various types to test and I got a 5000 lb load cell working so I thought I'd goof off and test a few. I decided to quit hand drilling since none of you offered to come over and make holes so I got out my old roto-hammmer. It's a little big for a 1/4" hole but I figured it would at least go fast. I set it up and drilled a hole - it was like drilling in wood. took all of about 30 seconds. I started a second hole and my bit skittered on the face and blew out the carbide. I don't have another 1/4" bit so resigned myself to one test for today.
I picked a 1/-1/4" button head and whacked it in with my hammer. The surface of the stone flaked and spalled a bit and I trapped some rock junk between the plate and the face of the rock. Oh well, so it goes.
I loaded it up but my test fixture failed before I actually popped the anchor but the anchor was loose in the hole and I pulled it out with my fingers.
I also bent the SS shackle just enough to make it worthless, there goes another 4 bucks. I've been spending too much on shackles, threaded rod, drill bits, coupler nuts and load cell accessories. I am pretty sure I won't be turning a profit on this project.
Anyway, I got to 2715 lbs.
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Minerals
Social climber
The Deli
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Oct 31, 2010 - 01:57pm PT
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2,715 lbs from a shorty and people still bitch about quarters???
Cool testing, Banquo! In the last photo, did the bolt begin to crack, on the convex side of the bend? How about testing the 1.5” length? And, how about testing some of the Fixe 8mm crap bolts (or do we really want to know…)?
As was mentioned earlier, testing the bolts with a real bolt hanger seems more appropriate. Also, it’s a good idea to “pre-crater” a quarter-inch hole before hammering in a buttonhead. I use the pick end of my hammer to flare out the hole a little. This helps to prevent any cratering and accumulation of rock chips behind the hanger during bolt placement.
Too bad you’re not just across town… I’d come over and drill holes in that block all day long for ya… with a real drill bit! ;) Keep up the good work! Thanks!
Re. ASCA and those wedge bolts that I hate so much… We actually placed a few stainless shorties this year, as replacements for Bachar taper bolts. It is easy to remove the taper bolt itself, but then the soft sleeve is stuck at the bottom of the hole, which would require power to remove. So we just tapped the sleeve to the bottom of the hole and then placed the wedge bolt. No, it’s not removable, but we were able to reuse the original holes. A stainless 5-piece would have required a new hole, so why not utilize the existing hole while we can? Someone can drill a new hole in 100 or 200 years.
(Hey Al Dude, One-Armed Bandit has been replaced…)
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Clint Cummins
Trad climber
SF Bay area, CA
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Oct 31, 2010 - 02:12pm PT
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Bryan,
> It is easy to remove the taper bolt itself, but then the soft sleeve is stuck at the bottom of the hole, which would require power to remove.
Just like the Star-Dryvins, I believe you should be able to remove the lead sleeve with a lag screw.
But I'm not sure - I have done it many times for the Star-Dryvin, but not yet for a taper bolt.
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Minerals
Social climber
The Deli
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Oct 31, 2010 - 02:25pm PT
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Good idea, Clint. I had some lag bolts that Greg gave to me in order to remove the lower sleeve on a 6-piece bolt but I had no luck with this method. It might work better with something soft like the taper bolt sleeve – have to give that a try. Thanks!
I think we need to get with Theron to design a specific sleeve puller for the 6-piece bolts. I have yet to get the lower sleeve out on one of those longer bolts. Damn power drills…
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Thorgon
Big Wall climber
Sedro Woolley, WA
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Oct 31, 2010 - 02:36pm PT
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Bruce~
The hole is actually bigger than 3/8" and the the cap screw is 3/8" and using stainless steel cap screw makes for a great set up. If I can dig out my old hand drill I will post a picture. It is basically a piece of solid steel round stock with a 3/8" tap in one end where you place a 3/8" stud with a locking nut. Then you attach the Red Head and tap and turn till your calves burn! I used this set up on one of my FA's in North Caroliina at Stone Mtn., then the Carolina Climbers Coalition came through four years later and removed all the hangers on my bolts and placed SS bolts next to them, really made a mess! I understand that they wanted the routes to be safe, but it seemed like a waste of my efforts to place good bolts in the first place! Do not get me wrong CCC has made climbing safer in the South for years, I just wonder about a better way to replace self drilled anchors!
I am drifting, hope that explains the Red Head self drillers I used in the early 90's. So the question is can the hole be reused instead of just filling it with glue & granite dust? Anyone? You can drill out the center cone, but I never have measured the I.D. of the hole to see what size it is, could you drill deeper and place a SS expansion bolt, no b/c then the top of the hole would be to big, glue-in? I don't know? Like I said it is the best set-up I have ever seen for hand drilling, but the replacement issue has always bothered me. This self-drill set-up may have good wilderness back country applications?
By the way, I was using hardened steel (machine grade V, I believe) hex head cap screws in North Carolina, it was the early 90's and no one was using SS at Stone Mtn at that time! I also used Lock-tite and silcone under the hanger, which I think helps on friction routes b/c water tends to fill the holes.
Thor
GREAT THREAD! BOLTS, YEEHAW.....
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Steve Grossman
Trad climber
Seattle, WA
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Oct 31, 2010 - 10:48pm PT
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Time to pass the hat...the man is spending all his shekels on shackles! LOL
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Thorgon
Big Wall climber
Sedro Woolley, WA
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Oct 31, 2010 - 11:07pm PT
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I could send $10.00.... Better cause than the TV Evangelist!! LOL
Thor
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bhilden
Trad climber
Mountain View, CA
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Thor(gon),
your are not scoring any points with me with your explanation. As you state, you have to drill a hole larger than 3/8" to insert a 3/8" threaded cap screw. That is a lot of extra work for a 3/8" bolt. Why?
Another issue is that threading something, unless it is done correctly, adds a weakness to the stock which is threaded. If you look at the photos of the Simpson wedge anchors in this discussion, you will notice that the threads are not cut into the stock. The threads are on the outside of a round piece of stock so there is no chance of adding a stress riser.
Cut threads, on the other hand, add a stress riser to the stock and weaken the screw. All the cap screws I have seen use cut threads.
So, you have to drill a hole larger than 3/8" to be able to insert a cap screw with cut threads. That's two strikes in my book.
The third strike is that, in my experience, it takes more than one self-drill anchor to drill one hole. That's a lot of waste and weight.
Bruce
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Thorgon
Big Wall climber
Sedro Woolley, WA
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Bruce,
It has been my experience that hand drilling sucks no matter what drill you use. But that is how I was raised, ground-up hand drill, I have a Bosch but only use it for replacing bad bolts! I have replaced a lot of bolts and can tell you that if the hole is over-sized the whole operation is a shame (which I am sure you know). The upper bolts on Yankee Go Home Stone Mtn NC were "replaced" by an old timer and we ended up with spinners! When I went to replace them a second time it only took one or two taps with the hammer to remove the "new" bolts because the hole was oversized. I have used every hand drill that is available and I like the Red Head system for remote routes! However, I think it is a non-issue because I checked the Red Head website and they don't sell the self drive anymore. So let's just forget the entire issue!
Back to your regularly scheduled program: "Tested two 1/4" anchor"!!!
Thor
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Clint Cummins
Trad climber
SF Bay area, CA
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Cool old gear, Thor. Hand drilling is not too bad with the SDS carbide tip drills. The Petzl RocPec SDS holder is also a lot lighter than the self-drill setup in your photo. :-)
I agree, it sucks if somebody tries to replace your bolts, but does a bad job and they end up worse than the originals!
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Thorgon
Big Wall climber
Sedro Woolley, WA
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Clint,
Hell yeah the SDS's are nice, I started with a star drive masonary drill and still have the scars on my calves to prove it! Three hours on one hole at one 5.9 friction stance, then I gave up but my calves cramped so bad I still have the bruises! My dad had a Bosch Bulldog that he would not let me use, actually I wouldn't have used it anyway, but we decided to call the route "Father Knows Best"!! That was about 1990' then I got a bunch of the old 5.10 drills with the double straight flute and they worked o.k and I finished the route on my 27th birthday! But once the corners chipped off of the 5.10 drills you were dead in the water! My best time is still 1/2 hour and that was when I was doing it all the time and not just typing about it on a computer! LOL
It was that 1/4"x 1 1/4" deep hole to 3/8" x 2 1/4" deep hole transition of the early 90's that took some getting used to for sure! The 1/4"ers you could just bang out and slam in a Button Head and move on, but to drill 2 1/4" of 3/8's in GRANITE, then you were a working man!!!
Send On,
Thor
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Salamanizer
Trad climber
The land of Fruits & Nuts!
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This is all some really cool info. I'd really like to see more of this kind of testing.
If money is an issue to keep the testing going I'm sure Supertopo can help out with that. I'd be willing to donate some SS SMC hangers, Metolius SS hangers, 1/4" x 1 1/4" button heads and even a bit of cash.
I also have some 1/4" x 2" "spikes" that I'd like to see tested. I've had alot of people tell me those are total crap. But in my (limited) experience pulling them, they have been the hardest 1/4 in bolt to remove.
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SuperTopo on the Web
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