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Hexciter
Jan 12, 2010, 10:36 AM
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While surfing over net, I read comment for cam physics on limestone in forum of DCU Rock Climbing Club.
- CAMMING ANGLES -
Basically avoid Black Diamond Camalots if you
ever plan on climbing on limestone. All camming devices use the basic
logarithmic camming angle of 12.75 Degrees from normal except Black Diamond! Camalots are designed to give a larger expansion range per device, to do this they use a different camming angle that diverts the force of a fall more downwards and less outwards (towards the crack walls) (and they use 2 axels). this means that camalots will pull, Rip, pop-out much more easily on rock with lower coeficents of friction - e.g. limestone. All friends require extra care when being placed on limestone but camalots even more so and should be avoided. they work well on sandstone and granite though. And if you dont want to climb on limestone you're missing out!
Source is:
https://www.redbrick.dcu.ie/~climbing/phpBB3/viewtopic.php f=6&t=225&st=0&sk=t&sd=a&sid=c7f78c4ed5f4c431b2b9683510ccb960&start=15
He made a mistake that camming angle of Friend should be 13.75 degree as patented by Jardine, not 12.75.
What's your opinion? Does it make so much difference?
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sungam
Jan 12, 2010, 11:09 AM
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WC - 13.75
CCH - 16
Metolius - 13.25 (I believe)
BD c4 - 14.5
(really) old c4's - 14.97
OP link cams - 13.5
DMM 4cu - 13.75
Trango flex cams - 14
These are not definitely true, just what I picked up from websites. Anyways, you can see there is a large range of camming angles used, with aliens having the highest and metolius cams having the lowest. If anyone sees an error in my list, feel free to correct.
Edit to add trango and DMM.
(This post was edited by sungam on Jan 12, 2010, 11:21 AM)
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granite_grrl
Jan 12, 2010, 12:38 PM
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My opinion: I don't trust any cam in a parallel sided crack in limestone. BD might be the worst, but I wouldn't expect much from any brand. When I place a cam in limestone I am looking for scoops or some sort of other constriction to place them in, but most of the time I'm happier with a hex.
Here's the story of the hubby meatdeacking: http://www.rockclimbing.com/...ssy%20talus;#1708704
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j_ung
Jan 12, 2010, 1:54 PM
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^
+1 on that. Slick rock scares the hell out of me.
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camhead
Jan 12, 2010, 2:02 PM
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LIMESTONE WANTS BOLTS!
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kennoyce
Jan 12, 2010, 2:55 PM
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Sungam's post looks spot on to me. Aliens certainly do have the largest camming angle and would be the most likely to pull in limestone, and of course metolius has the smallest camming angle and might possibly hold in limestone all though I wouldn't count on it.
As Camhead said, limestone needs bolts. One time I was sport climbing on limestone with a noob who was asking me about trad climbing. I happened to have a small rack in my bag that I had forgotten to take out, so I proceded to place a DMM 4CU (13.75 degree cam angle) in a nice parallel crack at medium expansion range. I wanted to show the noob how a cam works so I gave it a but of a tug only to watch it rip right out of the crack. Needless to say, I don't think it convinced him that trad climbing is indeed safe. Moral of the story is that cams in parallel sided limestone = R/X.
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atlnq9
Jan 12, 2010, 6:40 PM
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Metolius Fat cams are what you want. Larger surface areas touching the rock.
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geezergecko
Jan 12, 2010, 7:40 PM
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Aw nuts! 
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guangzhou
Jan 13, 2010, 12:38 AM
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I climb and place cams in limestone a lot. Placements in limestone come down to experience, like any other placement.
I prefer nuts and hexes in limestone, but that is true of any rock. I use what ever gear works for that specific placement.
My two cents.
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guangzhou
Jan 14, 2010, 6:02 AM
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climboard wrote: camhead wrote: LIMESTONE WANTS BOLTS! I'm all for keeping bolts to a minimum on most rock but after climbing Rockies limestone I agree with this!
I have to agree, every cliff has different needs when it ocmes to protection. Some limestone is suitable for gear lines, others need bolts.
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patto
Jan 11, 2011, 10:32 PM
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sungam wrote: BD c4 - 14.5
I seem to remember C4s being 15. A quick google is non conclusive with many saying 15 and many saying 14.5.
I seem to remember adatesman measuring the cam angle and calculating it to be 15.
atlnq9 wrote: Metolius Fat cams are what you want. Larger surface areas touching the rock.
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rtwilli4
Jan 12, 2011, 1:32 AM
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patto wrote: atlnq9 wrote: Metolius Fat cams are what you want. Larger surface areas touching the rock. That wont help except in the case of rock crushing. More surface area does not mean more friction!
I'm no scientist but it would seem that more surface area would mean just that... more friction. Am I wrong?
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guangzhou
Jan 12, 2011, 2:57 AM
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rtwilli4 wrote: patto wrote: atlnq9 wrote: Metolius Fat cams are what you want. Larger surface areas touching the rock. That wont help except in the case of rock crushing. More surface area does not mean more friction! I'm no scientist but it would seem that more surface area would mean just that... more friction. Am I wrong?
In this case you're wrong. With cams, more surface is only part of the issues. Hardness of the material plays a bigg role on the holding strength of the cam too.
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patto
Jan 12, 2011, 3:09 AM
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rtwilli4 wrote: I'm no scientist but it would seem that more surface area would mean just that... more friction. Am I wrong?
It can get more complicated in other cases though. Ice skates use low surface area for lower friction. Whereas skis use large surface area for lower friction.
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rtwilli4
Jan 12, 2011, 4:20 AM
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I've had just a bit too much Beam to be thinking about all that :)
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uni_jim
Jan 12, 2011, 4:56 AM
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Hexciter wrote: While surfing over net, I read comment for cam physics on limestone in forum of DCU Rock Climbing Club. - CAMMING ANGLES - Basically avoid Black Diamond Camalots if you ever plan on climbing on limestone. All camming devices use the basic logarithmic camming angle of 12.75 Degrees from normal except Black Diamond! Camalots are designed to give a larger expansion range per device, to do this they use a different camming angle that diverts the force of a fall more downwards and less outwards (towards the crack walls) (and they use 2 axels). this means that camalots will pull, Rip, pop-out much more easily on rock with lower coeficents of friction - e.g. limestone. All friends require extra care when being placed on limestone but camalots even more so and should be avoided. they work well on sandstone and granite though. And if you dont want to climb on limestone you're missing out! Source is: https://www.redbrick.dcu.ie/~climbing/phpBB3/viewtopic.php f=6&t=225&st=0&sk=t&sd=a&sid=c7f78c4ed5f4c431b2b9683510ccb960&start=15 He made a mistake that camming angle of Friend should be 13.75 degree as patented by Jardine, not 12.75. What's your opinion? Does it make so much difference?
Get out of the lab.
Limestone, in my experience, almost never will give you a "perfect" parallel crack. You will have pods or edges that you can use to your advantage, turning your cam into a nut with an expansion range. Learn how to use these and the cam angle won't make a lick of difference. I have fallen on cams in limestone, and not one has pulled. You just gotta learn how to use em!
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billcoe_
Jan 12, 2011, 7:39 PM
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I'm calling bullshit that Limestone has a lower coefficient of friction than granite, or probably sandstone as well. It's true that Metolius cams have a better angle for holding and sticking, but really, where are all these BD cams ripping out of rock stories?
BTW, the Totems are pretty respectable and have a claimed better holding angle than other cams (claimed), anyone try them on Limestone?
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granite_grrl
Jan 13, 2011, 12:34 AM
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camhead wrote: billcoe_ wrote: I'm calling bullshit that Limestone has a lower coefficient of friction than granite, or probably sandstone as well. It's true that Metolius cams have a better angle for holding and sticking, but really, where are all these BD cams ripping out of rock stories? Granitegirl linked a story just above in this thread. Also, Goran Kropp's death in 2002 involved pulling out at least two camalots from a parallel sided basalt crack.
Chossmonkey still has the scars on his ass from that experience.
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bearbreeder
Jan 13, 2011, 4:55 AM
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if there's a good stance i like to place a nut or tricam wherever i can ... allows me to save the cams for the harder parts ... less likely to pull IMO as well
a set of 0.25-2 tricams sit on a single biner on my harness all the time
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Hexciter
Jan 13, 2011, 10:15 AM
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I have been just considering Totemcams has a better value in the limestone. The parallel cracks is good for regular cams are rare. The limestone gear have very different priorities that used in the granite. No cam abuse. The best is balanced mix of what is available, in my opinion.
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billcoe_
Jan 13, 2011, 2:58 PM
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camhead wrote: Granitegirl linked a story just above in this thread.
Thanks Camhead! I need to click links:-) Scary stuff. Does anyone know if the cams track out, like in softer sandstone, or if it's that the rock really has less friction coeffecient?
BTW, do NOT run out and get the dmm cams. Damn near identical to the BDs on the business end and cam angle with one tragic exception that might kill ya in softer rock: the cam lobes are ever skinnier! I suppose that they did that to shave a fraction of an oz off, but they could have hot forge stamped it so that the business part of the lobe was flared, and larger. Except that would have cost more. I have great respect for DMM, but feel they kicked this out the door before it was prime time.
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kennoyce
Jan 13, 2011, 5:25 PM
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billcoe_ wrote: camhead wrote: Granitegirl linked a story just above in this thread. Thanks Camhead! I need to click links:-) Scary stuff. Does anyone know if the cams track out, like in softer sandstone, or if it's that the rock really has less friction coeffecient? BTW, do NOT run out and get the dmm cams. Damn near identical to the BDs on the business end and cam angle with one tragic exception that might kill ya in softer rock: the cam lobes are ever skinnier! I suppose that they did that to shave a fraction of an oz off, but they could have hot forge stamped it so that the business part of the lobe was flared, and larger. Except that would have cost more. I have great respect for DMM, but feel they kicked this out the door before it was prime time.
Cams don't track out of limestone like they do in soft sandstone, generally when they pull it is because the rock has a much lower coefficient of friction. Limestone is mostly calcium carbonate which is very slick. I don't know if you've climbed much sandstone in the desert, but if you have, the slick white buildup in some places on the rock is calcite which is also calcium carbonate. Limestone can be that slick especially if it gets polished.
Cams can hold in limestone, but unless they are in a pod, I wouldn't count on them.
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