Recently we had a thread discussing a proposed Chinook IV.
I and several others said one could not improve on the present folding Chinook II or III, and, if one needed to address anything, only the folding aspect of the Chinook represented any area for improvement; and, so, in that line, several of us suggested a fixed blade Chinook IV, and that would remove the weak place of the folder (sideloads on the hinge, and not axial forces that put compression or tension loads on the lock).
The Chinook folder has perhaps the strongest lock of any of the factory production Martial Blade Craft folders, and thus, the knife has as its only weaknesses the minimal amount of blade material surrounding the hinge pin, and the levering loads placed on the hinge pin and liners with any bending side loads.
A fixed blade bypasses all of this.
Still, what if, for the next folding Chinook, the Chinook V, we attempted to address not only the lock (irrespective its acknowledged robustness), but the hinge pin, the liners in the bolster area, and the pivot hole of the blade and its surrounding area.
Why would we do this?
Well, the folding aspect, and the dimensions of the Chinook, sure make it easy to carry in practical social situtations.
If we could retain the folding aspect of the Chinook, and make it even stronger, almost to the level of a fixed blade knife, then, gentlemen, we would have something.
Not that we don't already have something.
By that I mean, what design qualities make the Chinook worth all this effort?
Please go to the following links by right-clicking on them and opening them in another Tab or Window:
http://www.newgraham.com/detail.aspx?ID=6330
http://www.cutleryscience.com/reviews/chinook_II.html
These sites will give the reader two pictures of the Chinook in profile, for examination and analysis.
First, take a piece of printer paper and, with the paper above the Chinook, line up one end of a straight edge of the paper with the middle hole of the three screw holes in the butt end of the grip, intended for the screws that hold the clip in place; and, put the other end of the same straight edge of the paper on the point of the blade.
Please note that the middle portion of the straight edge of the paper held up against the picture, as described above, goes smack dab right through the center of the hinge pin.
This puts the point right on line with the grip, like the point of an ice pick.
Ice Pick - good.
Notice the amount of razor sharp belly the Chinook has below the line of the paper?
Hm.
Now, move the paper so the edge goes through the point of the blade; the point of the finger choil in the forward part of the grip, RIGHT BELOW THE HINGE PIN; and the point of the butt, where the little finger goes, right below the most rearward silver fastener.
Note that the point of the blade, the point of the choil, and the point of the butt all line up on one line, maybe with the point of the choil coming down a little below the line of the paper.
Notice also, though, and most importantly, HOW MUCH BELLY still sticks out, below the line of the paper.
Notice how much aggressive, curved saber razor edge we have sticking out into space, below the line of ice pick thrust.
Ice Pick - good.
Razor - good.
Ice Pick and Razor together - better.
Now, notice how the swedge carries the thickness and strength of the blade so far out to the point.
Also notice the upward curve of the swedge, even though the point does not "trail," nor extend above the ice pick thrust line.
Also note, that because of the upward curve and unsharpened nature of the swedge, in an underhand stab, pulling upwards, the curve of the swedge will not only force the blade deeper for no more effort, it will also force the index finger deeper into the choil, thus minimizing the probability, or even making it impossible, for the hand to slide forward onto the blade.
In other words, the harder one stabs, the more secure the grip.
Conversely, imagine the Chinook held in the reverse, Ice Pick, or Mexican carry grip (edge out), and used to stab overhand, such as into the face or down into the collar bone and throat.
In this case, the same curved and unsharpened swedge will force the blade deeper for the same effort, and it will drive the pinky deeper into the finger choil, so that the hand will not slide down on the blade, no matter how much force the user applies.
Absolutely brilliant.
Could Sal Glesser and James Keating possibly have designed these attributes into the knife without realizing it, such as geniuses often do in music and art, not realizing what great things they've done until critics surprise them with acclaim?
So, how would one make the hinge area of the Chinook stronger?
Perhaps if one started with a liner as thick as the present liner and scale together (or maybe even 1.5 times as thick), and then machined away the portion of the liner behind the bolster area, and thus made an integral liner/bolster.
One would put scales on the portion of the handle behind what would then appear as bolsters, but would actually remain an integral part of the liners.
Then, one could machine a countersink into the bolster, down to the thickness of the original liner.
Then, one would make the hinge pin two parts, one which slipped in from one side and had a threaded hole drilled into the pin portion; and, the other, which would have have an externally-threaded pin that would screw into the the threaded hole of the other pin.
The respective heads of the pins would have a larger diameter than the pins, and would have a cone shape corresponding to the countersinks in each bolster, and this would spread the load path over a larger area, out into the bolsters, and back through the pins to the other side.
Since, for strength and load path sharing, the two halves of the hinge pin would require applied torque during assembly, the hinge pins, and the pivot hole in the blade, would require a shim, or collar, or compression ring to keep the torque applied to two halves of the hinge pin from compressing the liner/bolsters down on the blade and keeping it from moving freely.
Perhaps a bearing race, or a plain bearing bushing pressed into the blade pivot hole?
Then, one would need to put a little extra metal around the pivot hole of the blade.
This sounds the most difficult to acheive, to me: it would seem to me Spyderco would not have removed any steel from this area that they didn't have to absolutely remove to get the lock to function as elegantly as it does.
In fact, I don't think Spyderco can add any metal in this area.
Therefore, how about adding a small extension on to the front of the liner/bolster, so that the liner/bolster goes as far forward on the blade as the bottom of the "CPM S30V" of the logo.
This doesn't represent much, maybe an eighth of an inch, but leverages add up, and this would give the blade more lateral support in front of the hinge, and require less strength from the metal surrounding the pivot pin hole.
Could Spyderco make some incremental gains on the lock?
Some subtlety of engineeiring here or there?
I doubt it.
Engineers have fully understood these aspects of mechanical design for over a hundred years.
So, in a Chinook V, I would put my energies into an integral liner/bolster; a countersink in the bolster; a flanged two-part pin; and a pressed-in plain-bearing spacer.
I would not change the style of lock, as I believe this lock represents the strongest all-around lock, all things considered, for a folding knife.
My goal would involve placing the blade half-length into a vise, and, placing a side load on the handle, getting the blade to fail before the hinge fails.
This seems doable.
I don't know if one could do it and still market it in Spyderco's price range.
If it would only add $25 to the knife, I think people would want it, especially if anyone explained the knife's virtues to them.
I and several others said one could not improve on the present folding Chinook II or III, and, if one needed to address anything, only the folding aspect of the Chinook represented any area for improvement; and, so, in that line, several of us suggested a fixed blade Chinook IV, and that would remove the weak place of the folder (sideloads on the hinge, and not axial forces that put compression or tension loads on the lock).
The Chinook folder has perhaps the strongest lock of any of the factory production Martial Blade Craft folders, and thus, the knife has as its only weaknesses the minimal amount of blade material surrounding the hinge pin, and the levering loads placed on the hinge pin and liners with any bending side loads.
A fixed blade bypasses all of this.
Still, what if, for the next folding Chinook, the Chinook V, we attempted to address not only the lock (irrespective its acknowledged robustness), but the hinge pin, the liners in the bolster area, and the pivot hole of the blade and its surrounding area.
Why would we do this?
Well, the folding aspect, and the dimensions of the Chinook, sure make it easy to carry in practical social situtations.
If we could retain the folding aspect of the Chinook, and make it even stronger, almost to the level of a fixed blade knife, then, gentlemen, we would have something.
Not that we don't already have something.
By that I mean, what design qualities make the Chinook worth all this effort?
Please go to the following links by right-clicking on them and opening them in another Tab or Window:
http://www.newgraham.com/detail.aspx?ID=6330
http://www.cutleryscience.com/reviews/chinook_II.html
These sites will give the reader two pictures of the Chinook in profile, for examination and analysis.
First, take a piece of printer paper and, with the paper above the Chinook, line up one end of a straight edge of the paper with the middle hole of the three screw holes in the butt end of the grip, intended for the screws that hold the clip in place; and, put the other end of the same straight edge of the paper on the point of the blade.
Please note that the middle portion of the straight edge of the paper held up against the picture, as described above, goes smack dab right through the center of the hinge pin.
This puts the point right on line with the grip, like the point of an ice pick.
Ice Pick - good.
Notice the amount of razor sharp belly the Chinook has below the line of the paper?
Hm.
Now, move the paper so the edge goes through the point of the blade; the point of the finger choil in the forward part of the grip, RIGHT BELOW THE HINGE PIN; and the point of the butt, where the little finger goes, right below the most rearward silver fastener.
Note that the point of the blade, the point of the choil, and the point of the butt all line up on one line, maybe with the point of the choil coming down a little below the line of the paper.
Notice also, though, and most importantly, HOW MUCH BELLY still sticks out, below the line of the paper.
Notice how much aggressive, curved saber razor edge we have sticking out into space, below the line of ice pick thrust.
Ice Pick - good.
Razor - good.
Ice Pick and Razor together - better.
Now, notice how the swedge carries the thickness and strength of the blade so far out to the point.
Also notice the upward curve of the swedge, even though the point does not "trail," nor extend above the ice pick thrust line.
Also note, that because of the upward curve and unsharpened nature of the swedge, in an underhand stab, pulling upwards, the curve of the swedge will not only force the blade deeper for no more effort, it will also force the index finger deeper into the choil, thus minimizing the probability, or even making it impossible, for the hand to slide forward onto the blade.
In other words, the harder one stabs, the more secure the grip.
Conversely, imagine the Chinook held in the reverse, Ice Pick, or Mexican carry grip (edge out), and used to stab overhand, such as into the face or down into the collar bone and throat.
In this case, the same curved and unsharpened swedge will force the blade deeper for the same effort, and it will drive the pinky deeper into the finger choil, so that the hand will not slide down on the blade, no matter how much force the user applies.
Absolutely brilliant.
Could Sal Glesser and James Keating possibly have designed these attributes into the knife without realizing it, such as geniuses often do in music and art, not realizing what great things they've done until critics surprise them with acclaim?
So, how would one make the hinge area of the Chinook stronger?
Perhaps if one started with a liner as thick as the present liner and scale together (or maybe even 1.5 times as thick), and then machined away the portion of the liner behind the bolster area, and thus made an integral liner/bolster.
One would put scales on the portion of the handle behind what would then appear as bolsters, but would actually remain an integral part of the liners.
Then, one could machine a countersink into the bolster, down to the thickness of the original liner.
Then, one would make the hinge pin two parts, one which slipped in from one side and had a threaded hole drilled into the pin portion; and, the other, which would have have an externally-threaded pin that would screw into the the threaded hole of the other pin.
The respective heads of the pins would have a larger diameter than the pins, and would have a cone shape corresponding to the countersinks in each bolster, and this would spread the load path over a larger area, out into the bolsters, and back through the pins to the other side.
Since, for strength and load path sharing, the two halves of the hinge pin would require applied torque during assembly, the hinge pins, and the pivot hole in the blade, would require a shim, or collar, or compression ring to keep the torque applied to two halves of the hinge pin from compressing the liner/bolsters down on the blade and keeping it from moving freely.
Perhaps a bearing race, or a plain bearing bushing pressed into the blade pivot hole?
Then, one would need to put a little extra metal around the pivot hole of the blade.
This sounds the most difficult to acheive, to me: it would seem to me Spyderco would not have removed any steel from this area that they didn't have to absolutely remove to get the lock to function as elegantly as it does.
In fact, I don't think Spyderco can add any metal in this area.
Therefore, how about adding a small extension on to the front of the liner/bolster, so that the liner/bolster goes as far forward on the blade as the bottom of the "CPM S30V" of the logo.
This doesn't represent much, maybe an eighth of an inch, but leverages add up, and this would give the blade more lateral support in front of the hinge, and require less strength from the metal surrounding the pivot pin hole.
Could Spyderco make some incremental gains on the lock?
Some subtlety of engineeiring here or there?
I doubt it.
Engineers have fully understood these aspects of mechanical design for over a hundred years.
So, in a Chinook V, I would put my energies into an integral liner/bolster; a countersink in the bolster; a flanged two-part pin; and a pressed-in plain-bearing spacer.
I would not change the style of lock, as I believe this lock represents the strongest all-around lock, all things considered, for a folding knife.
My goal would involve placing the blade half-length into a vise, and, placing a side load on the handle, getting the blade to fail before the hinge fails.
This seems doable.
I don't know if one could do it and still market it in Spyderco's price range.
If it would only add $25 to the knife, I think people would want it, especially if anyone explained the knife's virtues to them.
