How do Horizontally placed Cams Work?


Original Post
Randomdiscourse · · Unknown Hometown · Joined Sep 2015 · Points: 0

For the past year, I've been exploring a potential weakness in the model that describes how Cams (SLCD's or Spring Loaded Camming Devies) work. This past fall I encountered a situation where this problem could have a very real effect.

I'd be interesting in getting some others take on this. I put together a video that summarizes what I've been exploring and the event in question.

https://youtu.be/hp6upPAj4nQ

EDIT: Changed the title of the post

AndySalo · · Unknown Hometown · Joined Mar 2016 · Points: 0

Can you clarify exactly what happens in the go pro footage? Did you break a hold in the runout and fall on the number 1? And it pulled during flight?

Randomdiscourse · · Unknown Hometown · Joined Sep 2015 · Points: 0

Fortunately, I didn't fall on the placement in the video though I did fall on a #1 that was placed later. The rock that came off I broke off with my foot when I impacted the wall at the end of the fall.

Full video is here: youtu.be/gTH_4IIIY4w

Charlie Proctor · · Somerville, MA · Joined Apr 2016 · Points: 40

Thanks for bringing this up and doing a little scientific analysis. Unfortunately I think your method of splitting the force vector into outward and downward forces and subtracting the downward force from the normal force of the upper lobes doesn't really tell the whole story. I do think you're onto something with the double axles. If you look at 6:20 in the video you can see that when the stem is pointed down, the upper lobes are bearing weight on the equivalent of an outwardly-flared crack which results in a reduced camming angle while the lower lobes do the opposite. This change seems to be far more apparent with the double-axle cam than the single axle.

In terms of real world application, I will be skeptical of shallow horizontal placement. If the placement is deep enough relative to its width, the stem can't rotate much past horizontal and none of this is a problem.

jason.cre · · Unknown Hometown · Joined Aug 2014 · Points: 10

Some bro took a secret video of some other bro who works at bentgate placing various cam in a shallow horizontal placement on a hangboard. During this scientific testing, all the cams blew except totem.

The Bentgate employee also got very angry about the secret video.

Jayson Nissen · · Corvallis, OR · Joined Aug 2013 · Points: 273

Very thought provoking.

Did you try to pull single stem cams out of your crack simulator?

Have you thought about gluing some stone tiles to the inside of your simulator to get a better approximation? I would guess that the shape and deformations of the crack are a major factor.

It would be nice to make up a little chart of the minimum crack depth for each cam. It looks like your crack is adjustable so then you could test your chart.

It also seems like the force you are applying to the cam is much greater than the force that would be applied by a rope. Perhaps you could simulate it by using a dynamic material to apply the force to the cam.

What happens if you just slowly apply the force to the cam?

Do you think that the top lobes are the failure points?

Jake wander · · Unknown Hometown · Joined Aug 2014 · Points: 165
Jayson Nissen wrote:Very thought provoking. Did you try to pull single stem cams out of your crack simulator? Have you thought about gluing some stone tiles to the inside of your simulator to get a better approximation? I would guess that the shape and deformations of the crack are a major factor. It would be nice to make up a little chart of the minimum crack depth for each cam. It looks like your crack is adjustable so then you could test your chart. It also seems like the force you are applying to the cam is much greater than the force that would be applied by a rope. Perhaps you could simulate it by using a dynamic material to apply the force to the cam. What happens if you just slowly apply the force to the cam? Do you think that the top lobes are the failure points?
how do you figure he is pulling down with more force than a fall would create when a rope is included? even small falls can easily put hundreds of pounds of force onto the top piece, but lets just be conservative and say, after rope stretch, your fall only puts body weight on the piece which 160lbs (for me). if he put a pulley where the cam is and tied a rope to 160lbs on the ground then fed the rope up through the pulley and pulled on the rope just like he was pulling on the cam, the 160 lbs would not come off the ground.
Brassmonkey · · Unknown Hometown · Joined Jan 2012 · Points: 115

In regards to protecting Carbs, you can place 2 yellows in that slot if you want, and you can get 2 good micro cams shortly after in slots after that. I never found a necessary 25 foot runout up there as others say.

Single axle for shallow horizontals when possible is all I have to add otherwise.

Ted Pinson · · Chicago, IL · Joined Jul 2014 · Points: 190

So I guess I must be missing something, because I don't see why 1) there was any surprise that the piece pulled in simulation or 2) this therefore means all cams will NEVER work in horizontals. When I saw the climber pull out a red C4 for a horizontal placement and remark "wow, this placement is really tipped out," my first thought was not "bomber!" C4s have very rigid stems which makes them awful for this kind of placement. This is what totems (or Tricams) are for, people!

slim · · Unknown Hometown · Joined Dec 2004 · Points: 1,005
Charlie P wrote:Thanks for bringing this up and doing a little scientific analysis. Unfortunately I think your method of splitting the force vector into outward and downward forces and subtracting the downward force from the normal force of the upper lobes doesn't really tell the whole story. I do think you're onto something with the double axles. If you look at 6:20 in the video you can see that when the stem is pointed down, the upper lobes are bearing weight on the equivalent of an outwardly-flared crack which results in a reduced camming angle while the lower lobes do the opposite. This change seems to be far more apparent with the double-axle cam than the single axle. In terms of real world application, I will be skeptical of shallow horizontal placement. If the placement is deep enough relative to its width, the stem can't rotate much past horizontal and none of this is a problem.
i think both of these things play an important part. even with a single axle cam, if the net total vertical force combined with friction isn't enough to meet the demands of the horizontal force, it's going slip.

the double axle doesn't help matters because the torsion about the connection between the stem and the housing (basically between the two axles) will cause the axles to move. the top one will move 'forward' which is going to affect the camming angle in a bad way (which is a good observation by Charlie P).

with both of these things acting together on a double axle cam, it is a pretty bad combo.
eli poss · · Durango, Co · Joined May 2014 · Points: 456

Just another reason to use tri-cams

Ted Pinson · · Chicago, IL · Joined Jul 2014 · Points: 190

Especially pink ones.

Gunkiemike · · Unknown Hometown · Joined Jul 2009 · Points: 2,755
jason.cre wrote:Some bro took a secret video of some other bro who works at bentgate placing various cam in a shallow horizontal placement on a hangboard. During this scientific testing, all the cams blew except totem. The Bentgate employee also got very angry about the secret video.
IIRC at least one of the other cams subsequently held in the hangboard slot when the anodizing was sanded off the lobe faces (that being the only signif. difference in the DMM cam that worked in the "test").
r m · · Unknown Hometown · Joined Apr 2015 · Points: 0

Thanks for the quality post - I had never seriously considered the impact of stem angle in horizontals.

Don Ferris · · Eldorado Springs · Joined Nov 2012 · Points: 175
jason.cre wrote:Some bro took a secret video of some other bro who works at bentgate placing various cam in a shallow horizontal placement on a hangboard. During this scientific testing, all the cams blew except totem. The Bentgate employee also got very angry about the secret video.
The video wasn't secret. He knew he was being filmed as I asked to film him as he pulled the cams cams out one by one finishing with the totem. He was upset he found it on mountain project...we talked it out without issue. Also, it wasn't a horizontal placment. It was 15* off vertical at most. That situation was quite different than this one. That situation was a lack of friction as a result of camming angle and/or surface finish of the lobes (allegedly).

Gunkiemike wrote: IIRC at least one of the other cams subsequently held in the hangboard slot when the anodizing was sanded off the lobe faces (that being the only signif. difference in the DMM cam that worked in the "test").
At least in the video I posted, none of the other cams held more than a than a tug before being pulled. The metolius ultralight resisted momentarily. I also (not in the video) inserted and pulled a well used x4, which lead me to believe it was more than just surface finish.

I've played with shallow horizontal placements with various cams and one thing I always notice is as the stem is bends over the edge, regardless of brand, the trigger is pulled back. This could lead to the lobes retracting enough to break contact with the rock.
Dave Carey · · Morrison, CO · Joined Apr 2011 · Points: 120

Excellent post...thanks for sharing...I would not have thought about this.

Dustin Stotser · · Springfield, MO · Joined May 2014 · Points: 363
Don Ferris wrote:I've played with shallow horizontal placements with various cams and one thing I always notice is as the stem is bends over the edge, regardless of brand, the trigger is pulled back. This could lead to the lobes retracting enough to break contact with the rock.
I've noticed this as well and initially thought that is where the OP was going to go with it.
RockinOut · · NY, NY · Joined May 2010 · Points: 100

If horizontal placements weren't safe people would be decking left and right at the gunks.

s.price · · PS,CO · Joined Dec 2010 · Points: 1,348

Title should read cams instead of pro. Many of us can place passive gear in a horizontal that is bomber. And tri cams rule in this type of placement.

Totems if you wanna pull a trigger.

Matt Desenberg · · North Berwick, ME · Joined Dec 2007 · Points: 150

Thanks for posting this, more knowledge is always good. In terms of real world application, I think the geometry of the crack could come into play (both positively and negatively in relation to the placement) vs. the perfectly milled crack you used in your demo, but you make some great points, especially regarding the single vs. double axles. A good reminder to consider fall directions and forces on a piece, regardless of it being a cam, nut, etc.

Cheers, this is one of the best contributions I've seen in a while. Curious, how did you replicate the exact width of the crack, and therefore, cam angle in your test?

Matt

patto · · Unknown Hometown · Joined Jul 2012 · Points: 25

Good post.

Probably not new information for those who have lived and breathed the technicalities of cams but that is probably a minority. Cam operation relies on a stem angle close to perpendicular. Anything that isn't this and you are entering complexities that can cause a failure to hold.

Given that close to half my placements of cams are horizontal placements, I'm not too fussed. I've fallen on them and test pulls are a matter of routine.

Guideline #1: Don't be a jerk.

Post a Reply

Log In to Reply