The Bears' Den--Shirogorov Showcase

Cylindrical rollers will have some sliding. Tapered rollers are designed to have uniform rolling along their length, but this requires that they run on a conical surface. You would not be able to drop in taper roller bearings into flat scales and a flat blade surface.


Like this...
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Count me in as someone who has wondered about the mechanics involved with roller bearings. They make perfect sense from a continuous load-bearing point-of-view in an axial configuration, I.E. wrapped around a shaft, but are definitely a bit more problematic to consider used in a radial application, such as thrust bearings in a knife pivot, which is our subject here. They could be tapered in such a way that each roller would move the same number of rotations at both the inboard and outboard ends as they swept through their required arc of movement. This, of course, would require that the surfaces they interface with be milled to match their taper, which I do not believe to be the case with the inside of liner/underlay washer or the blade tang. As Officer's Match Officer's Match and @Sharp & Fiery have noted, using cylindrical instead of conical rollers would require some sort of gliding or other accommodation in order to function.

I did a bit of math in order to wrap my head around this, as geometry has always been at the core of my approach to my carpentry, building, and sheetmetal fabrication vocations. (I think it's the German, mad scientist part of my DNA. :rolleyes:). Anyway, I used "Havoc" "Havoc" 's very clear overhead shot of his digital caliper 5/8" measurement of the roller bearing race as a starting point, converting to mm's, printing the image, and scaling the dimensions of the various components--roller length, roller diameter, and the diameter of rotation both at the inboard and outboard edges of the rollers. Scaling a pic isn't all that accurate, but it's close enough in this case for argument and puts us in the right ballpark (or knife block).

Without breaking down all the numbers, figuring that the blade has to move about 180 degrees, or about a half-circle, to open or close, I calculated that the inboard edge of the rollers in the race in question have to spin about 4.125 rotations in their travel and the outboard edge needs rotate about 5.374 times to cover that greater distance. Clearly a conflict and one that seems to indicate the need for some "gliding" as has been mentioned earlier.

The thing to consider here, though, is that the bearing races holding the rollers are not themselves fixed. I think what is happening in the pivot is that the rollers both spin and the bearing races rotate somewhat according to the difference in travel required at the inboard and outboard ends of the rollers. There are probably some physical complications in this that could better be calculated by an engineer, the product of these being some increased friction within the assemblies as the rollers still may glide somewhat over blade and washer surfaces as well as bind somewhat within the races.

This could account for Havoc's observations about the blade with SRRBs not free-dropping like in the MRBS incarnation of his F3. I can see where the knife would feel much more "solid" with the rollers than the BBs, as that's the point of the different bearing system anyway, isn't it? Not sure about the "opening faster" part as my SRBs F95T seems to open faster than my MRBS F95R, the former with less contact area and the latter with more. The MRBS does feel more solid, though, and smoother too. I wonder if Havoc's F3R with MRRBS feels smoother.

Well that's certainly a wall of text. Hope it doesn't put y'all to sleep halfway through. :p
 
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ChazzyP, I'm certainly not an engineer, but I'll proffer a theory. I'll call it the "burnout theory" - as in roasting your tires off the line. Once the traction is broken, it is fairly easy to keep the tires spinning. Since it seems that the rollers need to "break traction" in order to for the blade to rotate, it could be why Havoc discerned the quicker action, vs the MRBS spinning BB's maintaining more "traction" to the blade, relatively speaking. With the rollers, as soon as it starts moving, it's free to fly.
 
Didn’t realize my whim to change the MRBS to SRRBS would turn out to be quite the adventure in Blade Forums for us all, lol.

For the next few months I will report back with anything I feel that changes with this SRRBS setup. Keep in mind this is my non-empirical observation. Can’t see the roller bearings moving so it’s based on feel and tactical observation.

I do think the roller bearing shift in the race when the blade is engaged to flip (move). The race allows for some lateral movement so I think the roller bearings move into a “Caddy Corner” within the race which allow for them to spin.

But like ChazzyP ChazzyP clearly stated and even with the caddy corner shift there would still be a slight difference from inner and outer rotation.

ChazzyP ChazzyP I completely agree that the SRBS is the fastest and smoothest. I don’t have one on hand and completely forgot about them. Thanks for the reminder.

BUT, I do in fact like the feel of the SRRBS, if that helps ;)

I also agree with Officer's Match Officer's Match observation in that these roller bearings act almost like washers allowing the blade to glide across there surface but offer less resistance as they can still roll ever so slightly.

My take is that the SRRBS act like a Bronze washer/bearing hybrid.

Basically the SRRBS is just another innovation in the knife industry to set its maker apart from others in the feild.

We would have to go to the source (Shirogorov) and get his rational.
 
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Another factor to consider in this SRRBS vs. MRBS is the stability of the blade once open. The roller bearing have significantly more surface area in contact with the area of the blade surrounding the pivot as opposed to a very small point of contact in the case of ball bearings. This would also explain the advantage of SRBS vs. MRBS as having additional rows of bearings wouldn't contribute to faster or smoother deployment but MRBS would offer a wider range of contact with the area of the blade surrounding the pivot thus decreasing any lateral blade play when being used.

At the other forum, Shiro's rep posted strength testing of three knives, one with a single row of bearings, one with a single row of rollers and the other with two rows of rollers. Each was progressively stronger than the previous type.
 
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I also agree with Officer's Match Officer's Match observation in that these roller bearings act almost like washers allowing the blade to glide across there surface but offer less resistance as they can still roll ever so slightly.

My take is that the SRRBS act like a Bronze washer/bearing hybrid.

Now THAT is an interesting thought, one that might just prompt me to try a MRBS model so I can replicate your experiment.
 
There's certainly a lot going on here with these roller bearings with their free-spinning races, them sliding or gliding, OM's "burnout theory", and Havoc equating that with the rollers acting as washers (a notion that finds favor with me). With all the bearing pivot flipper knives I have, some of my very fastest and smoothest opening knives have thumb studs or Spydie holes and run on washers.

And just because we always need more Shiro pics and someone a few posts back thought there wasn't enough love for F3's here (which is indeed not the case) I'll throw in these two of my Python I shot last week and posted on another thread today.

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I'm a little stuck here, CPP CPP , as I showed my F95T back a few on TRfromMT TRfromMT 's Turtle Thursday, my F95R on last week's F Series Friday, and my F3 Python yesterday, well, just for the hell of it. I do have some pics not shown here left over from my 3 weeks with the F95NL World Tour knife last June, so here's a couple those.

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I'll make sure to get some fresh Shiro pics for M390 Monday, Tabargan Tuesday, and Won-Eleven Wednesday coming up. :p

EDIT: As y'all are aware I'm non-sectarian, I do have something else in my pocket for FrameLock Friday.
 
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I know this is not Shiro related, per se, but there is a connection... this is inspired by what I imagine a set of Pero scales must feel like. I'm doing this for one of my personal knives, in ironwood.

This will become a dedicated kitchen knife, and I like faceted handles in this application. They keep the knife from spinning like a top if you bump it. Safer (in my mind) when you lay the knife down.

The Pero gave me the idea.

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So, I pocketed my Hati this morning for M390 Monday, but picked up a Russian cousin at my PO around mid-day, purchased in an "off-books" PM'd transaction with one of our good members here. As you can see it's a long one with a 4.1", S125V, orange peel finish blade and milled out titanium handle slabs. It's the Sigma by Andrey Biryukov.

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picked up some oem micarta scales for my f3, they are superior to the g10. They also make the knife feel more its price point
 
Since christening a few new Shiro days last week and posting my Hati on M390 Monday alongside my new Andrey Biryukov Sigma which I've been carrying since, I figured I'd better at least get my 111 out for Won-Eleven Wednesday. That led to getting out my longest Russian blades and taking some side-by-sides for comparison's sake. Longer than my 95's--Hati, Turtle, and F95R--are, of course, the 111, 100NS Tabargan, Cheburkov Voron, and the new kid, the Sigma.

Measuring from the most forward prominence of each of their handles, the 100NS comes in at 102 mm--longer than named-- and the Sigma at 103, making both of those clearly subordinate to the other two. Surprisingly, my 111 comes up short of its name at just 109, though another mm would have its tip hitting the rearward curl of the backspacer. The Voron takes the prize for length at 112 mm.

None of this is meant to diminish my appreciation for any of these knives as they each have attributes that make them all favorites in their own way. I've always liked big knives and am reminded of the old off-color joke, paraphrased in knifely terms as in, "It's not how big your blade is but how you use it, though I've never heard a guy with a big knife say that."

On its name day, still a lotta love for the 111....

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