Cold Steel Tri-Ad Lock: The New Strongman?

C

Confederate

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Sep 5, 2005
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Having seen how Cold Steel's Tri-Ad lock, designed by Andrew Demco, I'm wondering if it's the new strong man in folding locks and if there's anything stronger. The knife is a bit too big and heavy, even for me, but the Blade Blog has given the lock a good write-up:

This is one heavy duty mechanism. It took some force for me to open the Rajah up, but once she was open there was no question she was staying open until the same force was applied to close it. "If you get a regular folder and go to chopping I guarantee you it's going to wobble," said Cold Steel president Lynn Thompson.

Well, this thing ain't gonna wobble.

Thompson, an avid wild game hunter, told us an interesting story about a hunting trip he was on in Australia in 1994 when one of his guides used the back of a folding knife blade to break the legs of an animal they'd killed. Thompson noticed how the guide used the knife, noting how possible it was for the blade to close right on the hand.

Lock strength is something Thompson and Cold Steel has focused on ever since.

"One thing I'm always worried about is the blade folding on your hand," Thompson said.

With the Tri-Ad lock that is one thing you don't have to worry about.

DSC_6796.JPG


With all the talk about CS stealing other people's designs, it made me think of that great line in Paper Moon. When Ryan O'Neal asked Tatum if she knew what "scruples" meant, she replied, "No, I don't know what it is but if you've got 'em, it's a sure bet they belong to somebody else!" In this case I think it's safe to say that the lock is closely related to the standard lock back, but made a good deal stronger. But is it the strongest?
 
Thanks for the diagram, always wonder how it differs from a normal lockback.

Any of you guys familiar with steel structural engineering? Not too difficult to calc the theoretical strength of the lock.
 
I dunno, the Ram lock on their Pocket Bushman is pretty dang tough. The only thing that i could see going wrong with that set up is that it is literally a spring that drives the Ram lock into position. If that gives out, then the ram could be disengaged pretty easily, i think.

I really like lockbacks. They are simple to use, and if manufactured correctly, they should be pretty resistant to folding up on you. That said, I don't see how a good frame lock isn't one of the best locking systems for a folding knife.

I guess it comes down to the fact that I personally would never use the spine of a folder to try and break bone. Seems like an "askin' for it" situation.:foot:
 
Seems to me the pin would have to be sheared for that to happen. As I see it, the design allows for the lock up to become stronger over time, not weaker. As it is, it appears to be about as strong as a folding knife can be. For a massive folder like the Rajah, it's kind of like having a fixed knife in one's pocket. (Yeah, yeah, we've heard that before with CRKT, but this time it looks fairly resistant.) I can't see how it would fail except through extreme use; maybe too extreme for most people to dish out.
 
That lock looks pretty good, for for simply being a lockback with a stop pin. I'm curious as to how knives with that lock will do over time, with wear.

I wonder how long it'll be till we see a lockback/linerlock combo? Somebody somewhere has got to have already tried one out. I wonder if they called it the dyad lock?:D

Regards,
3G
 
Cotherion said:
Any of you guys familiar with steel structural engineering? Not too difficult to calc the theoretical strength of the lock.
Click to expand...

Unless you know the direction of force that will be used to break it, and already know which part will break first, it would not be easy at all to calculate this theoretically. Assuming we don't know all that, a theoretical calculation worthy of review would require hours building a FEA (Finite Element Analysis) model. And a real world test would be better in every way.

"Rocker hole has extra space" slightly weakens the design from a pure strength perspective.

Though it may be slightly stronger than a std lockback with one pin through the rocker, unless you've broken pins or ripped pins out of the frame on previous lock-backs you have owned, you'll never know. Easiest way to increase strength of lock would be just increase the diameter of the rocker pin (and increase frame strength with thicker frame).
 
I'd say CS has come out with a genuinely original design (more specifically, Mr Dembco) and they should get credit for that. I've held the Rajah II and that thing is a beast and quite comfortable. I still just can't grasp how this design actually makes the lockback stronger, but many others seem to be able to see it so I'll take everyone's word for it until we get some real world examples demonstrating it.

HOWEVER, I don't care what kind of lock you have, spinewhacking a folder unprotected to break an animal's legs is pure idiocy.
 
Confederate said:
But is it the strongest?
Click to expand...

Confederate:

I wouldn't say this is the strongest lock mechanism, but is does potentially improve on the lockback design.

Take a look at any framelock, linerlock, axislock, rollinglock, etc and you'll notice they all use a stop-pin to halt the blade in the open position (keep the blade from "opening" further,) as well as the "lock" to keep it from closing.

Before this "triad" lock, lockbacks used the lock (which is secured by a single pin) to do this job, as well as keeping it from closing. (The lock did both jobs.)

Basically the Tri-ad potentially spreads out stresses to 2 points (like most other locks) instead of the "normal" lockback's 1.

This is an improvement if all pins on all knives were the same size.

However, like another posted stated, you don't see many lockbacks with a sheared pin.....
 
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Broos said:
Unless you know the direction of force that will be used to break it, and already know which part will break first, it would not be easy at all to calculate this theoretically. Assuming we don't know all that, a theoretical calculation worthy of review would require hours building a FEA (Finite Element Analysis) model. And a real world test would be better in every way.

"Rocker hole has extra space" slightly weakens the design from a pure strength perspective.

Though it may be slightly stronger than a std lockback with one pin through the rocker, unless you've broken pins or ripped pins out of the frame on previous lock-backs you have owned, you'll never know. Easiest way to increase strength of lock would be just increase the diameter of the rocker pin (and increase frame strength with thicker frame).
Click to expand...

Yeah, it's definitely easier and more realistic to just load it up till it fails. I've read in a non-US website that when they tested many knifelocks till failure the lockback rarely failed by shearing of the rocker pin.It's normally the shearing of the itty bitty section of the blade where the lockback's 'teeth' catches on to. If we were to open up a lockback knife and view the blade area especially where the lockbar contacts the opened blade, you'll see the itty bitty steel in question.

By the way, I opened up my two Cara Caras earlier just to have a better idea of how the whole set up looks like and luckily I found that one of my lockbar was not settling in fully! In opened position the contact section (where there will be shearing) was only 1/3 of the way. A few minutes of fiddling with a file (must not be careful not to remove too much steel) I managed to get it to lock with 100% contact.
 
Don't see too many jungle folk using folding slashers, choppers or axes - wonder why?

If you're gonna need a blade the size of the Rajah then an extra 5" of handle ain't gonna make that much difference so may as well go with a fixed blade.
 
the tri-ad lock is much more than just a strong lock, its also a very durable lock. I have some good video of tests we did in my shop you all may enjoy. I'll try to post it . Also, most "well made" modern lock backs fail at the rocker pivot first ,that is, if the rocker stays locked in the blade tang. You would all be stunned by how poorly many other designs do in strength and toughness tests
 
Cotherion said:
I've read in a non-US website that when they tested many knifelocks till failure the lockback rarely failed by shearing of the rocker pin.It's normally the shearing of the itty bitty section of the blade where the lockback's 'teeth' catches on to.
Click to expand...
Interesting - I was thinking that or the pin would go first.

It would be interesting to see a lock test - would you make efforts to keep the knife from twisting as it fails - I would think this would be a typical failure mode for gradual loading to failure (?). Do you apply force up (cutting) or down (closing). Or spine wack test? I just might put my money on the lockback, too. The only folders I've ever broke were many years ago, by throwing them as a kid.
 
many lock backs that I have seen break in weight tests , fail at there "blade tang notch" or the "rocker neck" but this is usually because of improper h.treat and/or no stress reliefs.
 
Like my daddy always says, the strength of a ___ (fill up item. Knife for example?) is the strength of the weakest part. I've found many instances where it may not be true but it is interesting to ponder.

DemkoKnives you designed this lock? I've always imagined the stress transfer of a lockback is to my rocker lock (during cutting) and old paranoid me always imagined wear and tear in that area. I like this design, It'll have the same cutting strength like most folders plus at failure (for cutting type loads) the stop pin AND the rocker lock will resist the forces. Am I correct with this guess :) I intend to get one soon. I've been eyeing the American Lawman but is it with the Tri-ad?

Keep the innovations/inventions coming... I need me a new knife!
 
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