What makes the Manix lock so strong?

B

bk400

Joined
Nov 1, 2005
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Looking for a bit of a physics lesson here....I understand why the thick steel liners and wide lock bar make the lock difficult to disengage by torquing the blade (imagine locking the blade in a vice and twisting the handle). But why is it strong at withstanding edge to spine pressure?
 
The engineering behind a 200#/in lockback is probably a piece of closely held intellectual property of Spyderco. I don't think that they will publically annouce to their competitors (who read this forum) how to duplicate the Manix and Chinook lock. ;) Just a thought.
 
"The engineering behind a 200#/in lockback is probably a piece of closely held intellectual property"

Just buy one and take it apart and compare to other lockbacks.

200 lbs/inch - per inch of what? Handle length? I've wondered about these units. As locks inhibit rotatation about an axis, I figured a unit of torque (moment, couple, whatever) would be more appropriate - i.e. lb.ft.
 
per inch of blade length. the chinook will hang about 800 pounds from the blade with the handle in a vice. In r&d the knife breaking machine at spyderco jumped around on the floor like an overloaded washing machine rather than break the knife, if I remember accurately. Carlos will correct my fool self if I'm wrong.:foot:
 
Michael Cook said:
per inch of blade length. the chinook will hang about 800 pounds from the blade with the handle in a vice. In r&d the knife breaking machine at spyderco jumped around on the floor like an overloaded washing machine rather than break the knife, if I remember accurately. Carlos will correct my fool self if I'm wrong.:foot:
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I heard the same story.

I'll second the opinion that this information is proprietary.

That's like asking to be a fly on the wall in a R and D meeting. :p

It's a great question, but I think we'll be left speculating.
 
See, that doesn't make sense.

So, the same lock with a 2 inch blade would be weaker, as only 400lbs would be applied.

No, don't buy it.

I think the units should be as a torque - i.e. __lb. ft. So many pounds applied at a distance from the pivot.
 
The exact methods used to acheive the desired results are almost certainly proprietary, but Sal has shared the "basic physics" with us on more than one occasion.

He has said repeatedly that a properly constructed and maintained front lock, unless defective, will never fail at the lock. They fail when one of the two pivots, either blade or lockbar either shears or bends and tears its way free from the handle.

Since with Spyderco we can take "properly constructed" as a given, that would lead one to think that the size and quality of pivot material, and the thickness and strength of steel liners when present (as is the case with the Manix) would be the major factors in lock strength.

Another major point he has often made is that, for obvious reasons, it is more desirable to have a "graceful" faliure, the type that occurs when things first bend and stretch then pop apart, rather than a sudden catastrophic one, as occurs when a part suddenly "snaps".
 
orthogonal1 said:
So, the same lock with a 2 inch blade would be weaker, as only 400lbs would be applied.

No, don't buy it.
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But they don't build a shorter bladed knife with exactly the same lock.

Besides, these numbers are not the actual lock strength, just standards that the lock must exceed. If the locks were built exactly the same, they would likely have approximately the same strength. However, if the blades were different lengths, they would be tested to two different standards.

Here's a post by Sal from the Spyderco.com Forum that explains the testing and standards:

Sal said:
First of all, Spyderco has set up our own in-house standards on lock strength to provide our own parameters for manufacturing.

We have established an in house test that breaks knives and records the break. We get a graph and numerical results of the break.

A knife is put into a vise and a probe applies pressure to the handle. The distance from the pivot pin to the probe is measured in inches. This is the leverage arm. If the probe takes 100 lbs of pressure to break the lock and the probe is 3 inches from the pivot, then the amount of force is measured as; "3 inches times 100 lbs equals 300 inch lbs of force to break the lock (or blade or ?).

We then established a standard for our own knives. We decided that we would use the inch lbs of force to break the lock times the length of the blade to establish thresh holds.

25 inch/lbs of force for every inch of blade length would be considered a "light duty service". That means that a 2" blade needs to hold 50 inch/lbs of force to meet the "light duty service" requirement.

50 inch/lbs of force per inch of blade would be "medium duty service". This means that a 2" blade times 50 inch/lbs of force equals a minimum of 100 inch/lbs of force to break the lock.

"heavy duty service" is 100 inch/lbs of force per inch of blade is required to break the lock. This means that a 2" blade times 100 inch/lbs of force equals 200 inch/lbs of force is required to break the lock.


MBC is 200 inch/lbs of force is required for every inch of blade length to break the lock. This means that a 2" blade times 200 inch/lbs of force equals 400 inch/lbs of force is required to break the lock.

This is not intended for any other knife companies or custom makers. It is our own standard that we test to with every model in every shipment or run in our own facility.

I hope that helps.

sal
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Sounds like a measurement of torque to me. Applying a known force, a known distance away from a pivot. A foot pound is the amount of torque produced when you apply a one pound of force one foot from a pivot point. Spyderco is applying a force in pounds to a blade, at a distance measured in inches.


Bruceter
 
It's not magic, or even proprietary. I think any knife company that wanted to make stronger more reliable knives can do so. Material choice, thickness, heat treat and geometries.

Basically you break it, measure and study the break, increase strength where the break occured until goal is reached. Ideally all of the parts are relatively close in ultimate strength.

There are some very good locks out there. Spyderco isn't the only company that pays attention to these details.

sal
 
The Deacon said:
He has said repeatedly that a properly constructed and maintained front lock, unless defective, will never fail at the lock. They fail when one of the two pivots, either blade or lockbar either shears or bends and tears its way free from the handle.
Click to expand...

Or - I'm just saying - when you get crud in the lock and it fails to engage at full strength. Now that's not a destructive failure - the knife will be fine when you clean it out - but it will make the lock fail to engage.

I mention it because it's the only kind of lock failure I (or most of us, I'm pretty sure) have ever actually experienced in a Spyderco front lock.

What I'm not sure of, on a personal note, is why I started many years ago with lockbacks - Schrade, Case, Spyderco - then decided when linerlocks came out that they MUST be better and stopped buying lockbacks for years. Now lockbacks are on the list of locks I buy, and linerlocks aren't.
 
Joshua J. said:
Originally posted by 4 s ter


What about the mini-Manix?
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I'm pretty sure Spyderco engineers the "Mini" knives from the ground up, so while the lock type is the same as the normal Manix, the geometry may be different. What can be counted on is the fact that the lock will work the best for that knife. I guess I'm trying to say that each lock is different to some extent for each model.
 
I vaguely remember from Material Mechanics labs (in eng. school), we deformed/broke steel rods, plates, and discs by applying loads longitudinally, transversly, and using rotation (torque), and measured the force required to do so. There are standard ways to test deformation and failure strength of almost any manmade object. I'm sure the R&D guys at Spyderco and other knifemakers have developed tests to determine (and consequently make a choice) as to what will be the weakest feature in any knife whether it be the pivot, lock, or blade steel from various directional forces. The Manix lock strength is legendary and I'm sure the engineers intended it that way.
 
Actually, the Manix (& 83mm) locks spun off of the Keating Chinook.

James wanted a very strong lock to support reverse (edge out) grip passing so a great deal of engineering and re-engineering went into the Chinook lock.

We had demand for a dop point version so Eric designed the Manix and he based the lock engineering on the Chinook.

sal
 
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