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  1. #41
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    Re revolver cylinder gap, when you need something like a piston or turbine shaft seal, a common solution is to cut grooves in one of the parts, making a "labyrinth seal". Doing a search requires patience because there are so many types of seals. The type I am referring to has grooves in one part, working against a smooth surface on the other part. I wonder if cutting grooves in the end of a revolver barrel could reduce leakage. You don't have much width to work with in most revolvers, so the grooves would have to be narrow. Opposing grooves in the cylinder, making a longer path, might also help.

    These are non contact seals so the cylinder gap can be retained.

    Bill

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    Quote Originally Posted by 9100 View Post
    Re revolver cylinder gap, when you need something like a piston or turbine shaft seal, a common solution is to cut grooves in one of the parts, making a "labyrinth seal". Doing a search requires patience because there are so many types of seals. The type I am referring to has grooves in one part, working against a smooth surface on the other part. I wonder if cutting grooves in the end of a revolver barrel could reduce leakage. You don't have much width to work with in most revolvers, so the grooves would have to be narrow. Opposing grooves in the cylinder, making a longer path, might also help.

    These are non contact seals so the cylinder gap can be retained.

    Bill
    The problem with interlocking groves and lands would be rotating the cylinder for the next shot.

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    Quote Originally Posted by gappmast View Post
    The problem with interlocking groves and lands would be rotating the cylinder for the next shot.
    They don't interlock. They stay where they are with the same clearance but the surface of one or both is grooved to produce turbulence that reduces the flow.
    Look at figure 10 in this patent I got for a jet engine thrust vectoring system, see the grooves marked 236. The piston doesn't touch the cylinder wall, making a very low friction unit and the grooves greatly reduce the leakage.

    US20030070417A1 - Apparatus and method for thrust vector control
    - Google Patents


    Bill

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    Quote Originally Posted by 9100 View Post
    Re revolver cylinder gap, when you need something like a piston or turbine shaft seal, a common solution is to cut grooves in one of the parts, making a "labyrinth seal". Doing a search requires patience because there are so many types of seals. The type I am referring to has grooves in one part, working against a smooth surface on the other part. I wonder if cutting grooves in the end of a revolver barrel could reduce leakage. You don't have much width to work with in most revolvers, so the grooves would have to be narrow. Opposing grooves in the cylinder, making a longer path, might also help.

    These are non contact seals so the cylinder gap can be retained.
    What are the typical gaps and pressure differentials for a labyrinth seal?

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    Quote Originally Posted by 9100 View Post
    Re revolver cylinder gap, when you need something like a piston or turbine shaft seal, a common solution is to cut grooves in one of the parts, making a "labyrinth seal". Doing a search requires patience because there are so many types of seals. The type I am referring to has grooves in one part, working against a smooth surface on the other part. I wonder if cutting grooves in the end of a revolver barrel could reduce leakage. You don't have much width to work with in most revolvers, so the grooves would have to be narrow. Opposing grooves in the cylinder, making a longer path, might also help.

    These are non contact seals so the cylinder gap can be retained.

    Bill
    Wrong way entirely to do the job. A better way to close the "flash gap" was invented, tested, produced in volume.

    It worked well enough to be copied, and more than once: The revolver it was predominantly applied to was no less reliable for it, didn't require tedious hand fitting.

    It became a bit of a legend for being VERY reliable, also easily maintained.

    Excerpt:
    In Russian service, it was known for its extreme sturdiness and ability to withstand abuse. As one former Imperial Russian officer stated, "if anything went wrong with the M1895, you could fix it with a hammer".
    Nagant M1895 - Wikipedia

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    As to the pressure gradient, obviously the pressure will be distributed across the row of vanes. I suspect that you will have a series of choked nozzles, but at the temperature and pressure in the revolver gap, I have no idea of what Mach one will be except that it will be much faster than 1000 FPS.

    Where is Prandtl when we need him?

    I am aware of the Nagant revolver but that system could not readily be applied to an existing design.

    One that could was made for our military, one of the spook branches.

    The requirement was for a suppressed pistol that would not leave brass lying around. It used a frame for a larger caliber that left more wall thickness in the cylinder, I think a .38 in a .45 frame. The cylinder was bored for the smaller caliber except for the front end and the counterbores were fitted with composition sleeves that had enough clearance to move. Gas pressure pushed them against the barrel to make a seal and when the pressure dropped off, it allowed the cylinder to turn.

    Bill

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    I have never accepted the Nagant gas seal theory.....and I have owned them ....IMHO ,the system allowed a very cheap and effective way to exactly align cylinder chamber to barrel leade.....in other words ,no matter how shaky the cylinder lock was ,the gun did not shave lead as so many other revolvers do when a bit worn....Webley always went by the theory that a revolver generated all necessary velocity before the bullet entered the bore....but a Webley velocity generally was around 600fps ,or even less in blackpowder loadings.And they did extensive research on ideal velocities.

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    Quote Originally Posted by 9100 View Post
    As to the pressure gradient, obviously the pressure will be distributed across the row of vanes. I suspect that you will have a series of choked nozzles, but at the temperature and pressure in the revolver gap, I have no idea of what Mach one will be except that it will be much faster than 1000 FPS.

    Where is Prandtl when we need him?

    I am aware of the Nagant revolver but that system could not readily be applied to an existing design.

    One that could was made for our military, one of the spook branches.

    The requirement was for a suppressed pistol that would not leave brass lying around. It used a frame for a larger caliber that left more wall thickness in the cylinder, I think a .38 in a .45 frame. The cylinder was bored for the smaller caliber except for the front end and the counterbores were fitted with composition sleeves that had enough clearance to move. Gas pressure pushed them against the barrel to make a seal and when the pressure dropped off, it allowed the cylinder to turn.

    Bill
    Prandtl-Meyer number does not apply. I never had need of his other work. There's no need HERE, either. You may as well have a go at improving the design of a Dinosaur's teeth. They just don't seem to be the threat to their neigbours they once were.



    Meanwhile .. the Nagant IS an "existing design" in and of itself. Already. Since 1895.

    It WAS utilized with silencers. By the other side's "spook branches".

    The technology worked for a lot more than 100 years, It still DOES!

    The Nagant didn't require dificult manufacturing techniques. It is generally regarded as requiring LESS precise machining and fitting than other wheelguns, not more.

    Could it be improved upon? Surely, it COULD.

    But as there was not, and IS not any serious barrier to moving the cylinder a skosh fore and aft, it delivered well-enough. Cheap, cheerful, could be "fixed with a hammer".

    WHY do we not bother to improve that? Not a lot of need, is there?
    Love wheelguns or not, the MAIN reason is that the "revolver" just doesn't happen to be the ONLY way to build a repeating handgun.

    Sometimes a better way to solve a problem is to not HAVE the problem to begin with?

    Pick your favourite - or even "wished for" - wheelgun as subject for a solution to "be applied to an existing design".

    I assure you that I can solve the cylinder-barrel "flash gap" problem in under two hours with no mathematics any more complicated than "grocery store arithmetic".

    It just isn't that complicated. Nor terribly costly. No exotic materials nor convoluted machining nor other space-age sealing materials nor techniques required.

    All I need is a specific wheelgun make, model, and cartridge chambering - so I can research some starting and ending numbers.

    Try me.

    Suppertime "back East". "Slow food" cook, here. Catch you in an hour or so?


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    Quote Originally Posted by 9100 View Post
    They don't interlock. They stay where they are with the same clearance but the surface of one or both is grooved to produce turbulence that reduces the flow.
    Look at figure 10 in this patent I got for a jet engine thrust vectoring system, see the grooves marked 236. The piston doesn't touch the cylinder wall, making a very low friction unit and the grooves greatly reduce the leakage.

    US20030070417A1 - Apparatus and method for thrust vector control
    - Google Patents


    Bill
    interesting if you do a search for labyrinth seals they show prints where they don't touch but interlock

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    Maybe to easiest way is to let it leak and add more powder to make up for the leak.

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    Quote Originally Posted by gappmast View Post
    interesting if you do a search for labyrinth seals they show prints where they don't touch but interlock
    I looked for something that illustrated my suggestion and found everything else. Linking to the patent was the quick way out. Nicola Tesla made configurations with the grooves angled so they restricted flow more in one direction. SU carburettors use grooves just like mine on their throat control pistons. It isn't original with me.

    Bill

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    Re Nagant revolvers, if they are so great and easy to make, how come no one else has copied them?

    Bill

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    Quote Originally Posted by 9100 View Post
    They don't interlock. They stay where they are with the same clearance but the surface of one or both is grooved to produce turbulence that reduces the flow.
    Look at figure 10 in this patent I got for a jet engine thrust vectoring system, see the grooves marked 236. The piston doesn't touch the cylinder wall, making a very low friction unit and the grooves greatly reduce the leakage.

    US20030070417A1 - Apparatus and method for thrust vector control
    - Google Patents


    Bill

    I can't really make that visible. How ever I work regularly with labyrinth seals on turbine engines. They do indeed comes in varieties with and without "interlocking" grooves. The interlocking groove type is called "packing" and found between stages of a steam turbine. The idea is to minimize the leakage between stages. Those without are commonly found in steam glands and oil seals. Each groove has a hole where the fluid being controlled flows away from the shaft. In oil seals the oil thus captured flows to the tank. Steam glands have a extraction pump which puts a vacuum to those grooves and the resulting mixture of air and steam is expelled to the atmosphere. When you see a power plant and notice a faint plume from the turbine building this the extraction plume. Labyrinth seals work on 2 principles. 1. the tortuous path for the fluid. 2. the centrifugal force of the shaft throwing the fluid outward to the female grooves. There is no centrifugal force in a revolver so scratch that one. Without an extraction system the seal would lose the same amount of gas slower.

    Your description of the drawing sound a lot like a hydraulic valve. The pressure keeps the spool centered and the leakage flows back to the tank, or in this case, the atmosphere. In those situations leakage is the objective and without it the assembly will not work.

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    Quote Originally Posted by thermite View Post
    Wrong way entirely to do the job. A better way to close the "flash gap" was invented, tested, produced in volume.

    It worked well enough to be copied, and more than once: The revolver it was predominantly applied to was no less reliable for it, didn't require tedious hand fitting.

    It became a bit of a legend for being VERY reliable, also easily maintained.

    Excerpt:


    Nagant M1895 - Wikipedia
    Just put a couple more tenths of powder in the case.

    Sent from my Pixel 2 using Tapatalk

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    Quote Originally Posted by pat_j0nes View Post
    Just put a couple more tenths of powder in the case.

    Sent from my Pixel 2 using Tapatalk
    This contributes to flame cutting, and creates unsafe pressures in the cylinder.

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    Quote Originally Posted by 9100 View Post
    Re Nagant revolvers, if they are so great and easy to make, how come no one else has copied them?

    Bill
    They were copied, even improved upon, but never mind. The need was vanishing whilst originals were still plentiful.

    Cap'n Obvious hat on. The usual reason for marginalization of revolvers in general, military and more police use each passing year the evidence.

    Semi-Auto pistols and - for military use, and/or/also "machine pistols" - replaced revolvers in general. Civilian market as well, over a hundred years, and still trending.

    That's my "two hour solution", BTW.

    The time it takes me to identify which semi-auto and chambering meets or exceeds the performance of your specific choice of wheelgun & cartridge, locate and price the replacement.

    No more "flash gap" atall.

    Whether one trades or sells the wheelgun, mounts it in a museum case, keeps it for nostalgia and fun of historical re-enactment, enjoys all that, or uses it as a prop in a stage play or movie is considered a "sunk cost".

    Or an "avoided" cost for those who haven't made that monetary outlay to begin with.

    Nobody MINDS if that's yer choice any more than cares what you choose for shoes, undershorts, chewing gum, toothbrush bristle stiffness, type and temperature of beverages, make and colour of yer car, or lack thereof. Personal choice is your call.

    Pragmatism and economics, not "religion", has driven a different choice for the majority market.

    I did say "grocery store arithmetic"?


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    Wow, this went way off track and into lala land talking about everything else other than what the OP asked. Great job at integrating "assassins", "Naggant's", what ever this is "Suppertime "back East". "Slow food" cook, here. Catch you in an hour or so?"


    Back to the discussion of barrel lengths and velocity.....

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    Quote Originally Posted by drom68 View Post
    Back to the discussion of barrel lengths and velocity.....
    Well yah know...what with barrel length, choice of primer and propellants, jacket material, fits to throating and forcing cones, choice of lubes or plating, if any, etc - already done to death and documented all over the entire planet, 150 years and more?

    Got's to entertain those who are too lazy to READ all that was done and is still part of the "normal" set of data collected when new stuff comes along, yah?

    If entertaining the lazy is the only thing for amusement, we could maybe "discuss" choice of wooden revolver cylinders vs rubber ones, or ponder barrels made of plastic, magnesium, stir-fried horse-turd, cryogenically treated Jello, or stress-releived peanut-butter instead of steel?

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    Quote Originally Posted by drom68 View Post
    Wow, this went way off track and into lala land talking about everything else other than what the OP asked. Great job at integrating "assassins", "Naggant's", what ever this is "Suppertime "back East". "Slow food" cook, here. Catch you in an hour or so?"


    Back to the discussion of barrel lengths and velocity.....
    I think discussion of leakage is within the boundaries of the original question. Automatics are increasingly used against people because they are soft targets. With the exception of the Wildey, which has mixed reviews, when people want to make something effective against grizzly bears, they use revolvers. S&W could have done anything they wanted to when they designed the .500. In that service, anything that reduces flash will increase velocity where penetration to a vital organ is the name of the game.

    My final statement about Nagants- besides moving the cylinder, you need to have a recoil plate at least the size of the cartridge base that moves forward and is locked securely enough to withstand the entire recoil every shot. You are not going to make a few mods to a Colt or S&W and accomplish that.

    Bill

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    Quote Originally Posted by 9100 View Post
    I think discussion of leakage is within the boundaries of the original question. Automatics are increasingly used against people because they are soft targets. With the exception of the Wildey, which has mixed reviews, when people want to make something effective against grizzly bears, they use revolvers. S&W could have done anything they wanted to when they designed the .500. In that service, anything that reduces flash will increase velocity where penetration to a vital organ is the name of the game.

    My final statement about Nagants- besides moving the cylinder, you need to have a recoil plate at least the size of the cartridge base that moves forward and is locked securely enough to withstand the entire recoil every shot. You are not going to make a few mods to a Colt or S&W and accomplish that.

    Bill
    No, nor bother to be in the same room with those antiques, either. But we can easily "accomplish" the damnedest of silly arguments ABOUT it, and probably 'forever".

    "Wildey?" No need.

    Before brown bears, Alaska, had grokked humans as wise to avoid risks (bears are right smart, and rather GOOD at the business of surviving to make more bears - avoiding trouble a normal part of that).

    A pioneer road location party, ALCAN highway, early summer of '42 entered a natural clearing on horseback. Hungry bear entered from the other side, figured horses were a meal, charged "gerade aus".

    All but one member of the party scattered to either side. One Sergeant's horse reared, exited stage wotever, having dumped his rider spraddle-legged on his ass, bear oncoming, directly.

    Colt government, 1911A1, modest FMJ issue ammo was all he had.

    While the rest of the party was trying to get paniced horses under control and unlimber horse-holstered 1903-A3 Springfields, .30-06? The lootenant, OIC, kept shouting to the Sergeant he was "Firing too fast!".

    Old Esquimo guide checks the carcass of that bear, found every single round of two full magazines but two rounds not fired had played a part in dismantling that poor bear's skull from its as-issued condition. .45 ACP isn't REALLY a pussycat, close up and personal, after all.

    Leftenant? Maybe next time YOU should fire "too fast" also?
    Wasn't a BAD thing the Sergeant was the established Regimental pistol champion.

    One round off a Wildey or Linebaugh? Good for you..

    But when it's an EMERGENCY? I'm good with a magazine or two instead.

    Yah want to hunt Brownies for SPORT? Use bare hands, stone axe, bone spear, or flint knife like you were meant to do, 30,000 years before pesky humans started cheating.

    Fair is fair. Bear can't even GRIP a wheelgun or samurai sword, let alone wear boxing gloves, his side of the "sport".



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