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nah000

climber
now/here
Jun 30, 2017 - 07:49pm PT
fivethirty already made most of my follow up point for me... but to mostly duplicate:

nope. i've never met either cam maker, either.

as small scale makers, i have the deepest respect for what both guys are accomplishing. it is no small feat.

and Tom is of course free to say whatever he wants, however he wants... not that it matters, but i even appreciate Tom's concerns and am in agreement that those concerns, given the current stage of testing for the merlin cams, are entirely legit.

however, i'm also just being direct, that the way he is recently going about his questioning [by calling them pusher pieces and making comments about the design principles that may or may not have been involved] only makes me lose respect for him and his position...

but i get those same comments don't bother a bunch of you and that's all good too...

just don't, necessarily, expect me to shut my yap, just 'cause you find my opinion annoying...

[and Alexey, if you're referring to my post as passive aggressive, i don't think you know what those words mean: i said exactly what i think directly to Tom...]
karabin museum

Trad climber
phoenix, az
Jun 30, 2017 - 08:27pm PT

JoeSimo - here is a #36 cam. Actually named a Mastadon 000



edavidso

Trad climber
Oakland, CA
Jun 30, 2017 - 09:59pm PT
Tom raises some good points and I think I've already addressed most of them in this thread already - see posts #85, 89, 184, and 186 if interested (and cam pull testing in #211). Unfortunately, I do not have any additional testing data to add at this time.

As far as I know, all cams are rated only for the direction of pull along the axis of the stem. All cams (except maybe some micros) will fail at a much lower load than rated if loaded off-axis and not allowed to rotate. The pamphlet that comes with cams admonishes you not to do this but doesn't give an off-axis load rating. Clint pointed out that link cams are notoriously bad for off-axis loading, for example. As pointed out, larger cams are more susceptible to off-axis loading. Have VG's been tested in a load frame in an off-axis condition? How was this accomplished and what were the results? It is not an easy test to perform or standardize since you actually have to trap and prevent the cam from rotating into its preferred orientation. I think this is very rarely done on even commercially produced cams. Key takeaway - if you want to prevent off-axis loading, please take care to place cams so that they are either aligned in the direction of pull or can rotate to that position.

I am not trying to compete with VG's on strength. When I originally designed these cams, I wanted them to have a strength similar to that of commercially available cams, have the greatest range possible, lightest achievable weight, and be easy to use. The trigger lock was an added feature. As a result, they have about the same strength as a commercial cam, are 65% the weight of a VG9, have an entire extra inch of range vs a VG9, and operate like a smaller cam (single stem with narrow, two-finger trigger). Hopefully they will also stand up to the test of time. The one area where the Merlin #8 will also certainly be stronger and safer than a VG9 is in the crack range from 9-10 inches. I am sure Tom makes a great product and has been doing so for years. Everyone can make their own choice.
Tom

Big Wall climber
San Luis Obispo CA
Jul 1, 2017 - 01:31pm PT
Thanks for posting up Erick.


I have not been talking about off-axis loading of incorrectly placed cams. The buckling failure of the lobes occurs even if the cam is perfectly placed in a perfect testing frame, and is perfectly loaded in the ideal direction.

A big cam under load experiences surprisingly large lateral forces on the lobes, which will deflect and eventually bend them sideways (if the sling, stem and axles don't fail first). No off-axis loading of the cam is required for the lobes to deflect, bend sideways and buckle.

The reason is that the lobes are loaded in compression between the point of contact and the axle. When the lobes deflect to one side slightly, because the cam is not 100% rigid, the compressive force has a lateral component, perpendicular to the contact point-to-axle line. As the force on the lobe increases, the lobe deflects more and bends, which increases the perpendicular force component, which bends the lobe even more, which increases the perpendicular force even more, which bends it more, and so on.

To put it another way, even under proper orientation and proper loading of a big cam, the lobes will buckle under the high compression forces. This is analogous to a long, thin column loaded axially, which will deflect sideways near the middle. No off-axis loading is necessary to buckle the thin column, and no off-axis loading is necessary to buckle the lobes of a big cam.

In the real world, irregular crack surfaces will induce higher lateral force components, compared to a testing frame. A testing frame presents the ideal environment to minimize the lateral forces on the cam lobes; any deviation from that environment will increase the lateral forces, and cause the cam lobes to buckle at a lower load.


Again, no off-axis loading is required for a big cam's lobes to fold sideways and buckle. And no off-axis loading is necessary for a big cam to fail at a load that is considerably less than what is obtained in a laboratory using a testing frame.


EDIT:

Earlier when I spoke of off-axis loading of the lobes, I was talking about the out-of-plane, lateral loads that are perpendicular to the contact point-to-axle line. Those out-of-plane loads are components of the compression forces in the lobes, and are not due to incorrectly placing or loading the cam. They occur no matter how carefully the cam is placed and loaded.

I apologize for not being more clear, regarding the nomenclature.

edavidso

Trad climber
Oakland, CA
Jul 2, 2017 - 10:46pm PT
Tom, thanks for clearing up what you were talking about. I figured you were talking about off-axis loads since those were the terms you were using. Buckling, is indeed a different failure mode though the end result looks the same. I have also mentioned buckling as a failure mode in my previous posts. Buckling is as you've described - the sudden, catastrophic failure of a compression member subjected to nothing but axial loading. The critical buckling load will be lower if subject to eccentric loading (e.g. axial load is applied at edge of lobe instead of center of lobe and therefore causes a small bending moment) or any off-axis force that causes a bending moment (I believe these would be the lateral loads you talk about).

I have designed these cams specifically to resist buckling. They are not the same as the Camalot design where the lobes have a fair amount of play out-of-plane. In the Merlin design on each side there are two lobes that sit right next to each other separated by small spacer washers. The other lobes are trapped on the outside by the dogbone shaped endcap and the inner lobes are trapped on the inside by a step in the axles or control horns. This architecture is not possible with the Camalots because the springs get in the way; the springs on the Merlin are all internal to the sets of lobes. So there is very little play in the Merlin lobes out-of-plane. What further resists buckling is the double axle design since the lobes are trapped in their plane on both axles. This has the effect of reducing the "length" of the compression member. This helps quite a bit since buckling load goes as the inverse square of length.

My load frame, itself, does nothing to resist buckling. When I do fail a cam in buckling, which I expect to be the first failure mode in a 9" crack, I will post the video and results. I'm probably not far from buckling one in the 8" crack either at a load at or above 12 kN. I agree that real world loading conditions are rarely ideal as they are in a load frame but this is how all cams are tested and rated. I believe the main culprit in cams failing earlier than they should is off-axis loads. These cannot always be avoided but good placements can prevent the worst of the off-axis loads.
Tom

Big Wall climber
San Luis Obispo CA
Jul 3, 2017 - 02:39am PT
Erick,

You are right on it.

That dog-bone that rides along the cam lobe, which will suppress outward lateral deflection of the lobes, is brilliant.

But, inward deflection needs to be addressed.

Test.


JUST DO IT.



Break one, in a wide testing frame, and see what happens. Don't use a webbing sling. JUST DO IT.


Load a Merlin cam until the lobes bend, buckle and fold sideways, and report the results.


And, then it will be easier for people to decide if they want a VG piece that can pull a truck out of the mud, or Merlin piece that is strong enough for a great rock climbing experience.

Matt's

climber
Jul 3, 2017 - 08:14am PT
And, then it will be easier for people to decide if they want a VG piece that can pull a truck out of the mud, or Merlin piece that is strong enough for a great rock climbing experience.

Tom, you really are backing yourself into a corner here!!
Late Starter

Social climber
NA
Jul 3, 2017 - 08:51am PT
Perception..I'm not seeing any corners. In fact, it seems pretty civil, and with good constructive banter/discussion.

MAYBE it's that YOU'D like to perceive there being an issue?
JoeSimo

Trad climber
Bay Area, CA
Jul 5, 2017 - 11:31am PT
Hi Tom. I've been reading through this post a bit and was a bit confused by some of your posts so I corrected them below to what you probably meant to say:

"Merlin is another large cam for those crazies that like to climb off-width. It has some really innovative ideas and I tip my hat to it's creator for his obvious engineering prowess. I think both VG and Merlin have their advantages and disadvantages but truth be told both cams are great and only add to the wonder of climbing. I know Erick and I don't do this for profit and only do it out of true love of the sport and to give something back to the climbing community. So in that spirit I say again good work brother! I am impressed"

There Ftfy
Alexey

climber
San Jose, CA
Jul 5, 2017 - 11:49am PT
nicely done JoeSimo!
Tom

Big Wall climber
San Luis Obispo CA
Jul 17, 2017 - 04:44pm PT
With all this conversation about the safety of self-made cams, I totally forgot to mention this story I heard in 1983:

Some guys from Australia made their own cams, but they used the wrong spiral profile. Instead of an exponential/logarithmic spiral, they used some other type of spiral, which did not have the equal-camming-angle property, which is unique to the Exp/Log spiral. Those Aussie cams would not hold properly, and the word got out, around the Valley, that they were unsafe.


That was the first time that I became aware that it was possible to make cams that would not be safe. Cams look simple enough, especially the small ones, but there are myriad details that have to be addressed and taken into account.

BD's recent/prior quality control problems with making cams in China is a testament to that statement.



As an aside, my AutoCAD program will not generate an Exp/Log spiral, only an Archimedes spiral. My Microstation CAD program will generate a proper Exp/Log spiral from its parameters.

My guess is the Australian guys in 1983 trusted their computer to get the spiral right, which is not usually a good idea.



thebravecowboy

climber
The Good Places
Jul 19, 2017 - 05:07pm PT
BLUEBLOCR

Social climber
joshua tree
Jul 20, 2017 - 09:44pm PT
Got mine today‼️Very prompt. Thank You Erick..and to your helpers?
I think it would pull my VW out of the mud! HaHaaaa.
But gosh dang it is soooooooo LIGHT😎


Cheers Merlinrockgear@gmail🐡
Largo

Sport climber
The Big Wide Open Face
Jul 21, 2017 - 08:28am PT
Makes my mouth water looking at these fantastic gadgets, and remembering back to my early days in the valley, when we had to work our way up the grades which involved a lot of trembling up the wide sections of climbs with little to no pro at all. Before tube chocks and long before cams, even citizen testpieces like Midterm, Vendetta, Twilight Zone, Right side of the Hourglass, left side of the Slack, Right side of Absolutely Free, Ahab, Center route of the Slack, The Cleft, LA Chimney, Crack of Doom, even Sacherer Cracker, all had wide stuff you basically had to run out. Easy stuff like Chingando was okay because, as we used to say, your knee was the protection, because a good knee lock was unlikely to just blow out. But those were exciting times.

After a few initial efforts of scaring myself stiff, I wouldn't go up on one of those hard wide routes unless I felt like I could solo it. Keeps your learning curve pretty flat.

These tools make it a much saner game, and probably saved more than a few lives. Strange and fantastic how a personal piece of gear, like a well-worn big cam, is a talisman to our past.
jerome.stmichel

Trad climber
Montreal, QC
Jul 31, 2017 - 09:47am PT
Hey guys,

I would be interested in getting a merlin 8.

Cheers,

Jérôme

j e r o m e . s t m i c h e l at m e . c o m
grover

climber
Castlegar BC
Aug 10, 2017 - 02:44pm PT

What a piece!

Stoked to have it for another go at this.....


And hopefully less of this!


Thanks Erick.
Gnome Ofthe Diabase

climber
Out Of Bed
Aug 11, 2017 - 01:24pm PT
Boo hoo, I still have big wide dreams!

all I got for fathers day was cheap glass from China
OlympicMtnBoy

climber
Seattle
Aug 11, 2017 - 02:44pm PT
Waiting to put mine to use too. Beautiful metalwork! The sling could be prettier though, what do you test those to Erick?
Jaybro

Social climber
Wolf City, Wyoming
Aug 11, 2017 - 02:58pm PT
Taking mine to Vedauwoo on Monday.!
Khoi

climber
Vancouver, BC
Aug 12, 2017 - 02:08am PT
Erick,

I'd like to buy an entire set once they are available. In the mean time, I guess it'll just be the 2 larger pieces.

That was the first time that I became aware that it was possible to make cams that would not be safe. Cams look simple enough, especially the small ones, but there are myriad details that have to be addressed and taken into account.

BD's recent/prior quality control problems with making cams in China is a testament to that statement.

Tom, that is incorrect.

In the roughly 10 years that BD operated that factory of theirs in China there were ZERO recalls.

It was after BD shut down that factory and moved production to a factory in Utah that we saw the flood of recalls, all of which came from their American factory - save for the recalled slings... I think those came from a factory in Mexico.

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