Strength of Rolling lock?

Status
Not open for further replies.
C

Cliff Stamp

BANNED
Joined
Oct 5, 1998
Messages
17,562
In the following post in the main forum :

http://www.bladeforums.com/ubb/Forum54/HTML/000126.html

A Rolling lock is subjected to thrusts of about 200 lbs of force on the handle which functionally damages the blade. After that the handle is struck with a rubber mallet a few times and now the lock then fails the spine whack test and is unstable.

The rolling lock is advertized to take over 1000 in.lbs of torque without breaking, however at what point does the lock get damaged and develop play and or become unstable? From the above thread it appears that this sets in at a much lower torque, maybe about 400 in.lbs. Is this the expected behavior?

-Cliff
 
Cliff
The best I can tell you is look in the old Spyderco forum doing a search under Lock Strength. The unscientific method your relating to means less the nothing. I belive after striking it with a mallet they were retested. I am not going to cover the same ground over and over.
Three other companies have tested the lock with the same specs.
Bob Taylor


------------------
Some days it's not worth chewing through the restraints and escaping.
 
Bob, you are missing the point, I am not disputing the 1000 in.lbs statistic. My question is at what torque does the lock become functinally damaged, and have you examined it under sudden impacts not slowly applied loads (which are unrealistic but do give impressive looking numbers).

There have now been two cases where the Rolling lock failed before the Axis. Steve Harvey did it hitting both with a stick and you called it a fluke. Frank/Rage did it by just leaning on it and then hitting it with a mallet and you called it unscientific. In neither case would you clearly state the expected behavior of the lock except to repeat the 1000 in.lbs number.


Here it is as plain as I can make it - if I buy a Rolling Lock folder from REKAT and vice it and thrust on the handle will the knife get damaged or not? There is no way I can reach 1000 in.lbs of torque by hand, so the critical question is at what point does the lock become unstable? What about sudden jarring impacts - if I hit the blade with a broom handle and it collapses is this normal behavior or not?

-Cliff
 
Cliff

With Steve Harvey. We asked Steve to return the knife and it was a QC problem which could have been fixed. A batch of blades got switched. Steve thinks it was the lever I don't, we goofed. Warren Thomas beat a first generation Rolling Lock to death on a curb including using a three foot pipe. and yes it failed after a while. How does putting a knife in a vise and beating on it relate to the real world? I have no desire in spending time and energy like I don't care if my Oldsmobile can withstand a TOW missle hit.It simpley dosn't relate to the real world.

Bob Taylor

------------------
Some days it's not worth chewing through the restraints and escaping.
 
Bob :

How does putting a knife in a vise and beating on it relate to the real world?
Click to expand...

It simulates a field stress in a controlled situation allowing for repeatability and most of all safety. If I want to use a blade for heavy chopping I don't just go out and do it. If the blade is not capable of handling the stress the edge could fracture badly and a piece of it could fly out and hit someone including myself or I could lose control of the swing etc. . I generally try to avoid things like that so I will put stress on the edge in a controlled manner and if it holds up then I will go out and chop with it (or whatever).

You are advertizing the Rolling Lock with a 1000 in.lbs of torque needed for a failure, and yet if someone leans on it and it fails you are making excuses about "unscientific" behavior and its not real world stress. That is irrelevant. If the lock was stable and could not be damaged until 1000 in.lbs of force was exerted on it, me pushing on it would not do anything to it at all, as I can't do a pushdown with 500 lbs . It would be very nice if I could, but I can't. So why would you have any reservations about stating the expected behavior?

As for impacts, off center hard thrusts into rigid targets will generate torques on the blade and be very similar to the stress the lock will feel if it was to be hit while in a vice as would a backhand cut that are interrupted or strikes that are blocked and lots of other things. The vice just makes it far safer as the worse that can happen if that the lock fails suddenly and the handle bounces off of the floor. If you tested the lock by doing hard thrusts and the blade suffered drastic failure a piece of it could go flying. Worse could happen if you tried some of the other expected stresses.

-Cliff


[This message has been edited by Cliff Stamp (edited 04-03-2000).]
 
Cliff
How many angles can dance on the head of a pin? I can’t answerer what I can’t examine. I asked Frank aka Rage to return the knife as was Steve Harvey asked to return the knife so with out input I am baffled. Excuses where did I post an excuse? I can’t fix what someone won’t return. I belive I said we goofed. How is that making an excuse? I don’t remember who did it but one person taped a Carnivore to a bat and whacked it against a tree unscientific? I would say so but do you see us touting it? At the same time you only dwell on the negative that bat test was unexpected shock and the knife held all others failed. With franks test the variables are numerous. Where was the pressure applied, at what distance from the pivot etc. etc. The reason Spyderco built their machine was to answerer these question with a baseline and consistent testing. On our end the questions are What generation carnivore was it? What lock was in it (batch number) what was the hardness of that lock? Should it have done what Frank says it did NO! Why, I don’t have the slightest idea nor will I ever without looking and doing a post mortem. As for testing we have beat a number of knives to death far beyond what is reasonable and prudent. Would I feel comfortable stabbing with a Rolling Lock you bet.

Bob Taylor


------------------
Some days it's not worth chewing through the restraints and escaping.
 
See...here's where I have to side with Bob.

The Carnivore, Pat Crawford rolling locks and the Sifu are personal defense folders. Based on my own handling of the knife, studying the design while the piece is 100% disassembled, doing pressure tests involving spine wacks and trying to push it closed and studying the test results of Frank and others, I feel my Sifu's lock is not going to fail in a fight.

If I used it as a daily wilderness survival tool, I doubt it would hold up for all that long, although in a pinch I wouldn't be totally screwed with it.

But that ain't why I bought it, and I very much doubt that's the market. In addition to lock strength, the release is in a place unlikely to be accidently triggered (Axis also fares well there) and the overall ergos and SIZE are what I need.

Upshot: if you could prove to me that the lock strength and overall durability on an Axis is double that of my Sifu (and I seriously doubt it's that much better), all you're going to get from me is a yawn. REKAT's folders aren't about "wilderness survival", they're "streetfighters", and the priorities are a lot different. Busse is about to enter the "super-tough-folder-sweepstakes", but even if they do a 5.5" or even 6" blade, if the smoothness of presentation or grip ergos or other "feel" issues aren't there, it's not going to supplant my Sifu as prime work-compatible carry.

God forbid I should ever have to pull a knife on somebody. I've done it once, I came real close another time. If I do, I want something that will pass "feel and confidence" back up along my arm, translating into a little grin of "well this is screwed, but at least I prepared right". I want the enemy to SEE that, and go dead inside before festivities even begin.

That's what a REKAT folder means to me. How many times I can slam it into a teak log isn't issue #1.

Sorry that got long-winded. It ain't easy putting this into words. Cliff, this isn't meant as a slur on you - having somebody around who specializes in studying and reporting "raw toughness" is VALUABLE, I'm damned glad to have you around and there's good reasons you're held in high esteem - by me and a whole lotta others. But in this case, I think YOUR prime focus isn't the prime focus of these knives.

---------------------

Now Bob...while I have your attention
smile.gif
how do I go about getting a few replacement grip screws? A couple of mine were tweaked a little from the factory...not bad, just cosmetic stuff. I could also use one replacement "grip barrel nut" thingie. At some point "ol' number 1" is going to get a facelift and I want to have these small parts ready.

Jim
 
Spyderco has a machine to test a lock's strength under Static Loads.

I believe that it would be fairly straight forward to build a machine that would test a lock's strength under impact loads by building a frame that would allow different amounts of weight to be dropped 24" striking a point X inches from the pivot with the knife blade secured in a vise.

While I am all for Scientific Tests showing the Static and Impact Loads that a lock can withstand I am left with what I believe is an important question.

What relevance do the numbers really have above a certain point?

If it is impossible for me to hold onto the knife at a certain load, does it matter if lock can withstand 150%, 200% or 1000% of that load? In all three cases the knife has been removed from my hand well before the lock fails.

Has anyone done any testing to determine the limits of the human hand to hold onto a knife under static and impact load conditions?



------------------
AKTI Member No. A000370
 
Bob :

Should it have done what Frank says it did NO!
Click to expand...

Excellent, that was the question I wanted answered.

I can t answerer what I can t examine
Click to expand...

I can understand you here, I do not think it is fair to post possibly damaging information without allowing the maker to examine the product for verification. I feel very strongly about this.

Jim :

If I used it as a daily wilderness survival tool
Click to expand...

That part about chopping wasn't referring to the one of REKAT folders, it was just illustrating the principle involved.

SDouglas, those are important points. Grip stability varies greatly from person to person and would have to be spec'ed by the individual.

-Cliff
 
who cares if it's non functional at 400 600 or 1000! i don't ! i just know it's not going to fail me !besides if we are going to get picky!! what knife was tested ?? in their specs i don't think
bob rates all his models at 1000 !!all i know or care about is i like the knife!!
 
I would like to see this kind of question taken more seriously. I'm not panicked by Frank's report; it hasn't convinced me the lock is likely to fail in use, but I would like to see manufacturers show some interest in explorations of the outer limits of their products and and discuss experiments done outside the factory seriously ... dismissing them with words like "unscientific," "means less than nothing," "unrealistic," "I have no desire to spend the time and energy," etc.... that is not the attitude I would like to see. If some tests apply more stress than we would expect to in use, isn't it worth a little time and energy to establish that your knife is overbuilt and can take substantially more stress than expected in use?

Sheesh -- what if Ferrari dismissed all tests of their cars at over 55 miles per hour as unrealistic and not worth spending time and energy on? Are REKAT knives Ferraris or Hyundais???

I can understand your frustration at not having the opportunity to examine the knife that was tested, at least not yet ... I'm afraid that frustration is making you come across like you think you have something to hide and you're trying to cover up ... I'm afraid that's the impression some people are going to get from reading this thread so far.


How about some details on the tests REKAT and Spyderco have done? How much force was applied, how far from the pivot, at what angle? What was the failure mode?

I hope it's clear I'm not casting aspersions on the lock; I'm not saying it's weak -- I'd like to investigate just how strong it is. I think it's worth some time and energy to discover that.

-Cougar Allen :{)
--------------------------------------
This post is not merely the author's opinions; it is the trrrrrruth. This post is intended to cause dissension and unrest and upset people, and ultimately drive them mad. Please do not misinterpret my intentions in posting this.


[This message has been edited by Cougar Allen (edited 04-05-2000).]
 
Cougar :

I'm not panicked by Frank's report; it hasn't convinced me the lock is likely to fail in use
Click to expand...

What is far more important to me than the report is how it is reacted to. Because of the way Bob has responded to this incident, I have little confidence in the lock nor in my ability to do an evaluation of it and be covered, one or the other is obviously necessary before I would feel comfortable with one. It still hasn't been made clear what the functional stability limit is.


I would like to see manufacturers show some interest in explorations of the outer limits of their products and and discuss experiments done outside the factory seriously
Click to expand...

Lots of them do, but unfortunately lots of them don't. The question is, why would you have a problem with being clear and open about the abilities of your product? The only reasons I can think of are either (a) you don't know what its performance is in that particular area, or (b) you want to hype it. Neither appeals to me, but (a) is alright if the maker will deal with you exploring it in a sensible manner.

... dismissing them with words like "unscientific,"
Click to expand...

If there is anything that sets off a red flag with me it is this term. It is constanly used incorrectly and in fact most that use it get scientific principles wrong in the critism. As an example relevant to this thread, Bob Taylor's error analysis in the following thread :

http://www.bladeforums.com/ubb/Forum1/HTML/001940-2.html

Where Bob you conclude a simple experiment has an 8000% uncertainty. This is not even physically sensible. It would mean for example that I could take a blade and do one run cutting cardboard and reach say 1000 cm before some predetermined blunting condition was reached and then resharpen and the next time it could take 80 000 cm. Needless to say that analysis is wrong and variances don't combine in that manner.

If you want to get a feel for how variances combine you don't need to study statistics, just do something and record the results. Go out and buy 20 pieces of 2x4 and chop through them each a few times. Record the number of chops you took each time and have a look at the scatter. Or anything else, it doesn't really matter. You will find that you get very consistent average results (larger the sample the better). There will be far less variation from mean to mean than from cut to cut.

How about some details on the tests REKAT and Spyderco have done? How much force was applied, how far from the pivot, at what angle? What was the failure mode?
Click to expand...

I did some searches for this but cannot find the exact numbers. What I do remember is that the torque was over 1000 in.lbs and applied at 2.4 cm from the pivot.

-Cliff
 
All our tests to date have confirmed Spidercos numbers of 1000 in.lbs. Torque whether it’s statistic or impact. In impact tests the same parts fail the same way at same amount of force. What was dun was convert the 1000 in.lbs torque to a statistic load at a given distends from the pivot then convert that figure to ft.lbs of energy the drop a given weight a given distends. What we found was on mater how force was applied it took the same amount to break the lock. Multiple impacts showed the more times you hit it less force per blow was needed to do damage to the knife. We did not do any tests to find a sustained impact the lock would take do to the number of knifes and time it would take to do such testing.
At what point does the lock get damaged and develop play and or become unstable? 1000 in.lbs is near the upper limit the lock will take if repeatedly stress the lock at this point it will at some time fail. It’s like running an engine at the red line it will do it but its not going to last for long.
In franks post he says his weight is 216 lbs. put that 4-in. from the pivot and we get 864 in.lbs. torque that’s easy to figure. What’s not and why we say they’re not unscientific is how fast did he accelerate his weight onto the knife do the numbers and you’ll find it don’t take much and you go from under 1000 in.lbs to well over and did accelerate himself the same for each thrust and the same for each knife. Same goes for the hammer. If he repeated the tests today they may or may not come out the same way.
So where dose leave us and more impotently where dose leave our customers the max torque figure is what the knife industry uses to rate lock strength it may not be the best but it dose give a good reference to compare to. More people understand what torque is and how it relates to lock strength than foot pounds of energy (ft.lbs) or pounds per square inch (psi.) at the lock face, run the numbers on that one if you want to see a big number.
 
Bob :

At what point does the lock get damaged and develop play and or become unstable? 1000 in.lbs is near the upper limit the lock will take if repeatedly stress the lock at this point it will at some time fail.
Click to expand...

So does this mean that the lock can handle stresses below this without fear of failure? To be specific and reference another material property, metals have fatigue limits below which failure will not occur. Is 1000 in.lbs the low level limit for the rolling lock?

In franks post he says his weight is 216 lbs. put that 4-in. from the pivot and we get 864 in.lbs. torque that s easy to figure.
Click to expand...

Which is true and why I asked him where he was applying the force. However is it even possible to exert the force on the pin at that distance. The handle is only 5" long and isn't the pivot inside the handle?

What s not and why we say they re not unscientific is how fast did he accelerate his weight onto the knife
Click to expand...

Which is why I asked him to do some thrusts and estimate the force he was using.

you ll find it don t take much and you go from under 1000 in.lbs to well over
Click to expand...

So are you saying that the behavior of the lock was to be expected? This is contradicting what Bob Taylor stated in the above post.

If he repeated the tests today they may or may not come out the same way.
Click to expand...

That is always possible. I am sure he wouldn't have a problem with repeating them however if you supplied the blades.

More people understand what torque is and how it relates to lock strength than foot pounds of energy (ft.lbs) or pounds per square inch (psi.) at the lock face
Click to expand...

The problem I have with the way REKAT describes the lock strength is that at times it is very misleading. For example on the following page :

http://www.rekat.com/pockethobbit.html

The REKAT Pocket Hobbit redefines lock strength by taking over 1000 pounds on its' Rolling Lock without failure.
Click to expand...

On the Spyderco forum Sal comments that they applied a force at 2.4" from the pivot. Using this and the above description the lock would break at 2400 in.lbs, well out of the range of human ability.

If you are going to quote numbers you should be careful to be consistent. There should also be a detailed description on your webpage (which should be the main reference point) of the test and more importantly what it means in regards to lock strength/durability.

You have commented in the above how a normal personal can easily exceed the strength of the Rolling Lock by thrusting on it. I ask you the following question - how many people reading the above quoted description of the Pocket Hobbit would assume that was possible. It seems very misleading to me.

-Cliff

 
The only things I can offer to this thread is my personal expierences with the rolling lock, which I'm not satified at all.

I purchased an escalator at the Blade Show last year and have had it on my hip almost everyday since. When I invest in a supposedly quality knife I would never use it for anything other than it's intended purpose. Which mean this knife was used for NOTHING other than what was intended in Bram Frank's design, which was almost all in the closed posistion anyway.

First of all, almost every rolling lock I've ever seen outside of the showroom developed problems. A buddy's of mine has completed failed, even the most minute of movement will cause the lock to disengage. I believe this to be a problem with the spring.

Every rolling lock eventually develops an annoying rattling, like something is coming loose within the lock, this can't possibly help the strength.

My escalator has a black-T finish, which it is starting to shed like a lizard (another story entirely). There are places that the blade is in contact with the pins, and rubs while opening and closing. I noticed that one side of the blade has ALLOT more friction taking place that the other, which leads me to belive that there is uneven contact with the retaining pin while locked into the open posistion. So I think that when under stress this would cause failure at a weaker pressure.

Not to mention the questionable forging. I already stated that this knife was NOT abused. The tip of my blade snapped, there was NO BENDING, NO FLEX, NO GIVE, just a snap. A very CLEAN snap at that, almost brittle. You can see pictures here:
http://images.honesty.com/cgi-bin/honesty-image/3931838/escalator_full.jpg
http://images.honesty.com/cgi-bin/honesty-image/3934295/escalator_tip2.jpg

And also, there are parts of the handle that don't exactly line up. There are too many thing going wrong with my knife, and everyone else's to be a one time occurance, so I haven't tried to have it fixed, and have written it off. Unfortunatly this is the first and last knife I will buy from this dealer. There are other knives that can do the things Bram Frank intended with his design.

So why worry about the lock when the very metal of the blade will give out?

Driscoll



[This message has been edited by Driscoll (edited 04-07-2000).]
 
Driscoll, I think I can answer a few things here. The rattling is most likely due to the stop pin rather than the lock itself. That's been covered here before and has no real bearing on the strength as it still passes through both liners.

If your buddy's lock is not right, tell him to send it in, REKAT has fixed every other problem that comes up here in the forums. Bob Taylor has been interested in seeing locks that fail, so he can analyze them and see what happened.

As far as general workings of the knife, the Rolling Lock has never been claimed to be buttery smooth out of the box. It was made for strength, so a little smoothness of operation was sacrificed in comparison to many other lock designs. As for slightly misaligned surfaces on the handles, this is a production knife, not a custom. I still haven't handled a factory knife with liners and scales that line up perfectly.

I can't answer the complaints of the Black-T or the tip breaking, that's for someone else, although the tip had to have been subjected to some kind of impact or pressure. Steel doesn't just break off randomly, if it did, skyscrapers wouldn't last too long.

If you are completely unsatisfied, email me and I'll see if I can take it off your hands.
 
It's good to hear that the rattling in my Escalator is probably not weaking the lock, I'm still annoyed that it is doing something that it isn't supposed to do and wasn't doing when I bought it.

I understand that the design of the rolling lock won't allow completely smooth operation, and I admit that I was impressed with the locks functioning when I first handled one. But once again there is a noticable difference in it's performance. Now that the lock has been opened and closed for a year now you can see cleary the uneven contact with the blade. One side gets far more friction than the other

My buddy's Escalator is one of the orginal handmade ones, and displays the same problems with it's manufacture. We've both discussed sending them in for repair, I don't know he'll do. My Cold Steel Voyager is an example of a knife that lines up perfectly with it's liner in the open posistion, I'm still impressed after years of use in the Marine Corps. Spyderco is another example of well made knives. Here are a few examples.

http://www.bladeforums.com/ubb/Forum52/HTML/000077.html
http://www.bladeforums.com/ubb/Forum35/HTML/000288.html


I know for a fact that my Escalator never IMPACTED anything, and has never cut anything other than very soft items such as string in order to test it's edge. I agree that skyscrapers wouldn't last if steel broke off randomly. Which is why they put care and consideration in the making of the steel used to build them, if this wasn't the case they would snap in the wind and fall to the ground, just like any other poorly made metal product.

Thanks for all the info!

Driscoll


[This message has been edited by Driscoll (edited 04-08-2000).]
 
Just a couple points here...

Driscoll, Cold Steel Voyagers don't have liners to line up with - they are lock backs.

Second, if you are unwilling to send a defective product back for the manufacturer to repair or replace, then that leads us to 1 of 2 conclusions - either the product isn't that bad, or you don't care about having it fixed.

A statement like
"A buddy's of mine has completed failed, even the most minute of movement will cause the lock to disengage. I believe this to be a problem with the spring.
Click to expand...
is pretty serious. A knife like that is completely unsafe to use - if it was mine, it'd be back in the mail immediately.

Finally, about the questionable forging, how did the tip break off? Was it from impact, like when I broke the tip on my Blue Native by it slamming into the floor, or were you cutting some Swiss cheese with it?

Vague comments and allegations aren't what a company needs to fix any problems it may or may not have. You need to provide details, and if at all possible, the product itself so that it can be analyzed, repaired, or replaced. They can't fix the problem if they don't know exactly what the problem is.

Spark

------------------
Kevin Jon Schlossberg
SysOp and Administrator for BladeForums.com

Insert witty quip here
 
Status
Not open for further replies.
Back
Top