How strong is the folder going to be?

C

Cliff Stamp

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Recently I had a look at the lock on my Cold Steel Vaquero Grande and the blade unlocked under moderate force about 150 +/- 25 lbs (<a href="http://www.bladeforums.com/ubb/Forum3/HTML/001557.html">reference thread</a>). What was more of a problem however was that the handle started to come apart right away, long before I reached 150 lbs.

Sometime ago, Sal Glesser stated that when they started looking at lock strength they thought 600 in.lbs would be a good torque standard for heavy folders. It turned out that this was too high for most and they reduced it to 450 in.lbs for their heavy use folder (Military).

I commented then to Sal that even 600 in.lbs didn't seem like a large torque to me (depending on the size of the folder of course) and I was very surprised that the higer quality folders had problems taking that level of stress.

Anyway this got me to thinking about the Busse Combat folder. I realize that since it is not in production obviously exact spec's cannot be given, however what are the rough design goals? Are there levels set such as the 450 in.lbs of Spyderco?

Input from members would be interesting as well. How strong would you like it to be both up/down as well as side to side and of course violent impacts (stabs / strikes).

Should you be able to do a full power stabs into hardwood without fear of unlocking? How about a full power contact from a stick (broom handle size) on the spine? What about prying?

-Cliff


[This message has been edited by Cliff Stamp (edited 04-05-2000).]
 
The single "field" test I am aware of for lock strength was when the prototype was used in the following manner:

The handle was placed under the frame of a Hummer vehicle, while the blade was locked in a jack receiver and the Hummer was jacked off the ground...

The current design characteristics of the folder would prevent the handle from coming apart, as it is one piece. So the test here was lock strength solely, and it passed with flying colors...I suspect Jerry could add more here.

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Exactly what is the delay with the folder? If satisfactory prototype has been tested, why can't production begin? Is it going to be made in house or contracted out?

Bill
 
Ok, so it'll hold the weight of a jacked up Hummer
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So, what about locking it on the bumper in a vertical position and throwing a chain on it and doing a little tug of war with another Hummer? (that would be one hell of a promo!)

"Yours in any and every war"
 
I would think that a frame lock, "A la Sebenza or Mission MPF" would be the strongest possible lock. Is this the type of lock used in the design of the Busse Folder? or is there another style being used (axis, rekat, etc.).
 
I frequently see posts on Lock Strength and I am always left with the same question:

How strong does a Lock really need to be?

My personal opinion is that the lock needs to be strong enough that the Locked Knife is knocked out of my hand before the lock fails. No more, No less.

The problem that I have is how do you measure that limit. I have an idea but I need to ask a question first.

Is it a reasonable assumption that a lock will support a higher Static Load than Impact Load?



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AKTI Member No. A000370
 
Impact loads can cause failures because of low toughness whereas slowly applied loads tend to measure strength / compression resistance. As an example, lay a file on the floor and start putting weights on top of it. Nothing will happen as all you are doing is trying to compress the file. Now take a hammer and hit it lightly. You can easily break the file into pieces. Or put a file in a vice and try to snap it. A 3/16" file is fairly strong and will take a decent amount of force before it breaks. Now take another 3/16" file and put it in the vice and take a swing at it with a metal rod. You can break the file in pieces easily. However these are not really the relevant issues for folders under impacts as the steel used should be far tougher than what is in a file. The pins, lock facing etc., should all be very tough material easily capable of resisting fracture.

So assuming no sudden fractures, what is the difference beween a slowly applied load and an impact? Well a normal person can easily lift a fifty pound steel plate, however drop one from the top of your house and try to stop it just before it hits the ground. When an object is moving, not only do you need to apply the force of its weight to stop it from accelerating, you also need to apply an extra force to reduce its velocity to zero. The amount of this force increases with the square of its velocity and decreases with the distance you chose to stop it in. This is why, for example, when catching a baseball you let the ball move your arm back.

-Cliff

[This message has been edited by Cliff Stamp (edited 04-07-2000).]
 
The locking mechanism which holds the SRBs (Solid Rocket Boosters) for the Space Shuttle while on the pad were considered and tested. Jerry's new lock was put in place of the mechanism on several launches and they held so good that the shuttle was not able to leave the launch pad. Jerry had fully expected the locks to give way under 1.5 million punds of thrust but they even held at the 7.5 million pounds of thrust the shuttle produces. Small thermonuclear charges were used to disengage the locks on several missions and this explains the "Nuclear Tough" theme to Jerry's knives
wink.gif


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Mike--
That's a very nice demonstration of Cliff's lesson. The Busse lock held at 7.5 million lbs. of thrust, yet disengaged readily with just a small nuclear charge. And Jerry says he can do all this in a folder that weighs under 25 pounds. Now that's impact!

You guys make me feel old. When I was field dressing and butchering my first deer back in the 1950's, my dad told me, "Son, be careful when you push on the back of a pocketknife--it can close up and cut you." Taking his advice and after working on hundreds of animals, I'll admit I've had a few close calls, but never got more than a scratch--and that's with slip joints!
I think the nice little liner locks built into today's folders are just peachy, but I still take extra care whenever I push on the back of a folder blade--and would suggest doing so even on the strongest lock made. If they're built to fold, they're gonna fold--and not always when you're ready.
 
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