Umnumzaan fails spine whack? (not my vid)

A spine wack tests the lock in one mode of failure.

A locking knife should stay locked open when exposed to a reasonable force spine wack regardless of whether one cuts with the spine of a blade. Arguments of whether a knife is used in such a manner are of no import.

The refrigerator stabbing was teeth gritting - gloves should have been worn.
 
What mode of failure? The full speed reverse slash against a hard object? I think not.

High speed impacts are not a viable test. Elementary physics of intended application.
 
I can think of a lot of things to put in a fridge. A knife blade is not on the list. :)

Spine whacks. They serve two purposes, but remember, the whack is a tap, not a slam.

First, this will test if a lock is seriously defective, the kind that will fail in proper use because it simply isn't engaging well enough.

But second, and much more importantly, a light spine whack can actually help a new liner or frame lock to set properly.
 
I think that the Polish tests show what I long suspected - if you want to stab fridges (or steel drums or cars) then you should buy a really good fixed blade, not a folder! I believe that there are some Khukuri knives from Himalayan Imports that are fully capable of stabbing cars & steel drums with no damage (maybe some blunting) so that is the sort of thing to get for your standard fridge stabbing tasks that so many of us need to do.

I think I'll keep my folder to light duties like always and reserve the harsher tasks to my fixed blades (usually chopping & batoning rather than fridge stabbing).
 
In most of the "tests" Ive seen posted, the knife is slammed at high speed. I don't see that as a logical test at all.

I do agree with seating the lock, but too much pressure can damage any lock, especially a lockback.
 
I believe the ideal knife for stabbing a fridge is a stiletto, a needle blade with a large guard. Khukris are better suited for chopping up old fridges than for stabbing them. Now a Chris Reeve Aviator ... that might rip through a fridge door nicely.

WWLTD? What would Lynn Thompson do?
 
I find it interesting that these posts, both here and in the Reeve forum come from people with either a low post count or joined to post this.
As it was stated earlier, when you want to kill a refrigerator, any idiot knows that you must use the proper tool..(knife, gunfight and all that)..All kidding aside, if you have not read the post on the Reeve forum in it's entirety, then go ahead and do so. The information that is presented in the thread helps to understand some of the conditions present during this test and the conclusion (or lack thereof) of said test. Read it for yourself.
 
J_Curd said:
What mode of failure? The full speed reverse slash against a hard object? I think not.

High speed impacts are not a viable test. Elementary physics of intended application.
Click to expand...

And what "Elementary physics of intended application" would these be?

And what "intended application" for that matter?

And how does you're "elementary physics" explain the common failure of a liner lock when stabbed into a common cardboard box to start a cut?

And the spine wacks in the videos were hardly that forcefull nor, apparently, was the refrigerator stabbing putting much force on the blade to close, else the lock failure would have been evident then.
 
J_Curd said:
High speed impacts are not a viable test. Elementary physics of intended application.
Click to expand...


Actually in many cases dynamic load testing is also as common as static load testing. Though I get your point that a folder isn't expected to experience a large whack on the spine but many things happen in reality.

I've got a CRKT M16 which failed on me cause after cutting my box I was to hasty in putting it back on the table. It hit the bottom of my table and somehow it closed on me. I'd admit I was a bit impatient in opening the USPS box for my new blade :p

I don't approve of kungfu whacks and prefer moderate taps myself but I cannot disregard the use of dynamic testing on folders.

Many a cases in my line of work we dynamic test (impact type) because the static tests (like maintained or increasing load type) is not practical. How many people have a compressive machine or tensile test machine so we'll have to make do with the side of a table :)
 
steelhog said:
I had a similar issue with my umnumzaan. If I opend it softly the lock would slide but still close because the ball would roll. I just made sure to open it with a little force. Not a big issue.
Click to expand...

the ball does not 'roll' it slides, if you were not fully compressing the o-rings its possible that the lock bar was not in its proper location on the tang for maximum strength.
 
By the way guys, I remember since I read the "umnum test in Poland" thread that the Umnum lock was hyper-extended.

Hyper extending throws all normal assumptions for framelock outta whack (gettit :)). I remember when I was much younger I hyper extended my shallot lock cause it looked like it was in too deep. I wanted to increase the lock wear life. I ended up compromising it severely. Though it looked like my shallot's lockbar was engaged, it failed at finger whacks. Almost like a slip joint. Later when I took it apart (again) and increased the tension of the lock, I whacked (still young! Remember!) on the side of my table (with taped blade and with glove) and it passed! Miracle!

Therefore, do not underestimate the severity of hyper extension of framelocks.

PS: Evident that the lock was hyper extended in the Polish vid is because before the whacks he/she (not sure in the polish site's pictures) hyper extends the lock to show the ceramic ball in the lock tip. To pull back enough until the ball can be seen is definitely hyper extension.
 
I figure the ball is a nice touch for a gentleman's knife, but on a work knife it's just another potential failure point.
 
65535 said:
I figure the ball is a nice touch for a gentleman's knife, but on a work knife it's just another potential failure point.
Click to expand...

that ball is stronger than any type of metal to metal contact in that same application!;)
 
orthogonal1 said:
And what "Elementary physics of intended application" would these be?

I believe that J Curd was suggesting that in normal use, the main force vectors on the knife as a system, are downward on the handle and downward on the blade, with a vector force on the stop pin.

And what "intended application" for that matter?

I would guess that he means that you use a knife to cut things.

And how does you're "elementary physics" explain the common failure of a liner lock when stabbed into a common cardboard box to start a cut?

This sounds like a non-sequitur. Liner lock failure in a well made knife is far from common when the knife is used as intended. See below for additional information.

And the spine wacks in the videos were hardly that forcefull nor, apparently, was the refrigerator stabbing putting much force on the blade to close, else the lock failure would have been evident then.
Click to expand...

Assuming the act of stabbing the fridge was a straight line force along the longitudinal axis of the knife, we should expect that the stop pin, the pivot and the lock bar will equally absorb the impact force. However, if you examine the video, the individual in question prises the blade from the fridge by placing downward force on the handle. Due to the fact that the steel of the fridge has effectively wedged the blade, the pivot now acts to shift the force towards the spine of the blade and directly on the lockbar rather than the stop pin. This extreme pressure on the lock bar was repeated as many times as you see knife punctures. No lock mechanism on a folding knife is designed for that degree of stress. At that point, the damage was done. We have no knowledge as to how the knife performed under a 'spine whack' in that vid as none were performed. For all we know, the lock failed when he pulled the knife out of the fridge while off camera. As well, for all we know, he stabbed the knife into the fridge repeatedly off camera or otherwise abused the knife before the vid of the 'spine whack' failure.

I feel that after such abuse as was illustrated, it would be inappropriate to condemn any folder or lock mechanism. The actions simply exceeded the design criteria.
 
A.P.F. said:
Assuming the act of stabbing the fridge was a straight line force along the longitudinal axis of the knife, we should expect that the stop pin, the pivot and the lock bar will equally absorb the impact force. However, if you examine the video, the individual in question prises the blade from the fridge by placing downward force on the handle. Due to the fact that the steel of the fridge has effectively wedged the blade, the pivot now acts to shift the force towards the spine of the blade and directly on the lockbar rather than the stop pin. This extreme pressure on the lock bar was repeated as many times as you see knife punctures. No lock mechanism on a folding knife is designed for that degree of stress. At that point, the damage was done. We have no knowledge as to how the knife performed under a 'spine whack' in that vid as none were performed. For all we know, the lock failed when he pulled the knife out of the fridge while off camera. As well, for all we know, he stabbed the knife into the fridge repeatedly off camera or otherwise abused the knife before the vid of the 'spine whack'
failure.

I feel that after such abuse as was illustrated, it would be inappropriate to condemn any folder or lock mechanism. The actions simply exceeded the design criteria.
Click to expand...

Besides all this, you also need to consider the photo of the reviewer overextending the lockbar and weakening it's engagement which the reviewer posted before this video in his complete review.The OP in this thread has left out critical info. He has posted the most devastating info to CRK and neglected to post the full story of this review.

This thread is an obvious attempt to incite a negative response towards either CRK or the Umnum. In short, we have trolling here, IMO.
 
picture1gv.jpg
 
It looked to me like the knife had no trouble with the fridge stabbing. I think that shows it capable and strong enough to handle something you might have to do in a emergency. (no not stab a fridge, just stab with force into something that's not soft)
I've seen liner-locks fail the spine whack just as easily and they didn't show any problem otherwise. One I had would give when I hit it easy on my arm. I thought the vibration was letting it shake off the tang and slip past. Another of the same model wouldn't fail and it's lock would just get tighter to the opposite side. Neither knife ever failed under normal use. Those were both cheaper knives and I don't even consider spine whacking with the higher dollar ones I own. It just seems a bit abusive to me, as well as something that stresses a folder's blade/lock in a manner that it's not used.
 
I apologize if i come off as a troll, but that was certainly not my intention. Thank you to those who showed me the link to the thread in the CR forum. I searched for topics including Umnumzaan lock failure and spine whack/test but could not find that thread. It just surprised me because i saw the Umnum as a beefier sebenza that could take harder use? Not that i'm saying it cannot for it could just be that specific knife itself that could have been faulty. I mean no disrespect to CR in any way shape or form. My next purchase will be an Umnumzaan.
 
Chris Reeve Knives have posted in the other thread asking that the knife in question be sent to them for inspection. They are aware of the video and to prevent further speculations have asked to see the knife to determine the reason for failure. I personally trust the manufacturer and won't let one test affect my decisions.
 
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