How to calculate hoop stress

[Hannibalbarca]

How do you calculate hoop stress in an open system like a suppressor and how do you take into account gas volume as two different rounds with x load and x barrel length may have the same muzzle pressure but one may have twice the gas volume.

[fishman]

You really can't

[ECCO Machine]

You really can't

This.

You also really don't need to; a suppressor is not a barrel, and some housing expansion changes nothing.

I suppose it would be necessary to figure it out to a degree if you were trying to design the lightest can possible from scratch in vacuum, but fortunately, you have over 100 years worth of development and an internet full of the requisite information, which means you don't have to figure it out for yourself.

[Hannibalbarca]

You really can't

This.

You also really don't need to; a suppressor is not a barrel, and some housing expansion changes nothing.

I suppose it would be necessary to figure it out to a degree if you were trying to design the lightest can possible from scratch in vacuum, but fortunately, you have over 100 years worth of development and an internet full of the requisite information, which means you don't have to figure it out for yourself.

But how can you design a can with a certain safety factor without knowing this especially if it’s for rapid fire with very hot ammo? Theyll heat up and lose strength quite a bit. Now if I had 17-4 heat treated stainless I wouldn’t worry but I only have 304 stainless and grade 9 ti.
I also have 300 rum which I believe has muzzle pressures of 15k psi.
Another thing, for something like 308 I’m not sure if I can have say less than one inch of spacer, 24 barrel, using heavy bullets but also hit ammo.

It seems like knowing the hoop stresss that will occur in a given can with x muzzle pressure and gas volume is really important to know if you don’t want to blow your van up, either from one shot or from heating up too much and blowing it up.

[fishman]

Copy an industry can. They have bet high safety factors.

Dont use Ti for high pressure rapid fire

[Hannibalbarca]

Copy an industry can. They have bet high safety factors.

Dont use Ti for high pressure rapid fire

Not in the budget, I’d have to get 17-4 stainless hollowed out into tube. Currently it’s 304 and I just need to know what sort of hoop stress will be produced so that I can figure out what the safety factor will be and make sure it’s also acceptable at higher than room temps.
The 304 are the apogee tubes.

[fishman]

So put a 17-4 spacer in the blast chamber and call it a day

[ECCO Machine]

Dont use Ti for high pressure rapid fire

I do. I've run my .049" wall and .070" wall Ti tube 17-4 baffle cans on my full auto 13" .308, multiple successive mags. I actually melted a heat treated 8620 steel taper mount brake, which caused a baffle strike, and the tube still had enough integrity for everything to hold together, even with a bullet going through the entire stack and end cap.

[Hannibalbarca]

Dont use Ti for high pressure rapid fire

I do. I've run my .049" wall and .070" wall Ti tube 17-4 baffle cans on my full auto 13" .308, multiple successive mags. I actually melted a heat treated 8620 steel taper mount brake, which caused a baffle strike, and the tube still had enough integrity for everything to hold together, even with a bullet going through the entire stack and end cap.

Dimension? Spacer size? What sort of loads?

[fishman]

Dont use Ti for high pressure rapid fire

I do. I've run my .049" wall and .070" wall Ti tube 17-4 baffle cans on my full auto 13" .308, multiple successive mags. I actually melted a heat treated 8620 steel taper mount brake, which caused a baffle strike, and the tube still had enough integrity for everything to hold together, even with a bullet going through the entire stack and end cap.

Am I correct in assuming that your spacers are NOT titanium

[ECCO Machine]

Dimension? Spacer size? What sort of loads?

Don't use spacers; the spacing is set by the machined skirt on the baffle itself.

The cans are 1.5" OD, between 7.5" and 9" in length.

No special loads, just 147 or 150 gr. ball. But lots of heat and pressure with the 13" barrel, probably as much as if not more than a 24" 300 mag.

The failure of that brake that caused the strike was the result of going too thin; my brakes are a chamber type, and that one had a .650" ID with a .750" OD, 12 .190" ports in a helix with a .375 hole at the front that is "clovered" (3 radiused angled notches 120° apart). I quit using the 8620, doing only heat treated 17-4 with .600" ID and .800" OD. Have had no issues with the thicker walls.

Am I correct in assuming that your spacers are NOT titanium

Like I said, I don't use spacers. But the blast chamber is nothing but the Ti sleeve. The female taper mount is 17-4, threaded into the tube, 28 pitch on the .049 wall, 24 pitch on the .070 wall. The welded baffle stack is welded to front cap, threads in from the front. Between the front of the taper mount and the rear of the baffle stack, there is 3" of just Ti housing.

I'd love to show you, but don't currently have photo hosting since Photobucket's cash grab, and most other boards have internal hosting I use.

Ti weakens more than heat treated 17-4 at temperature, but it's still not weak.

[fishman]

Dont use Ti for high pressure rapid fire

I do. I've run my .049" wall and .070" wall Ti tube 17-4 baffle cans on my full auto 13" .308, multiple successive mags. I actually melted a heat treated 8620 steel taper mount brake, which caused a baffle strike, and the tube still had enough integrity for everything to hold together, even with a bullet going through the entire stack and end cap.

Dimension? Spacer size? What sort of loads?

Like I said. You'll have to reference industry cans or builds on here.

What do you want the can to be capable of?

[Hannibalbarca]

Dimension? Spacer size? What sort of loads?

Don't use spacers; the spacing is set by the machined skirt on the baffle itself.

The cans are 1.5" OD, between 7.5" and 9" in length.

No special loads, just 147 or 150 gr. ball. But lots of heat and pressure with the 13" barrel, probably as much as if not more than a 24" 300 mag.

The failure of that brake that caused the strike was the result of going too thin; my brakes are a chamber type, and that one had a .650" ID with a .750" OD, 12 .190" ports in a helix with a .375 hole at the front that is "clovered" (3 radiused angled notches 120° apart). I quit using the 8620, doing only heat treated 17-4 with .600" ID and .800" OD. Have had no issues with the thicker walls.

Am I correct in assuming that your spacers are NOT titanium

Like I said, I don't use spacers. But the blast chamber is nothing but the Ti sleeve. The female taper mount is 17-4, threaded into the tube, 28 pitch on the .049 wall, 24 pitch on the .070 wall. The welded baffle stack is welded to front cap, threads in from the front. Between the front of the taper mount and the rear of the baffle stack, there is 3" of just Ti housing.

I'd love to show you, but don't currently have photo hosting since Photobucket's cash grab, and most other boards have internal hosting I use.

Ti weakens more than heat treated 17-4 at temperature, but it's still not weak.

What’s the blasts chamber size?

[Hannibalbarca]

I do. I've run my .049" wall and .070" wall Ti tube 17-4 baffle cans on my full auto 13" .308, multiple successive mags. I actually melted a heat treated 8620 steel taper mount brake, which caused a baffle strike, and the tube still had enough integrity for everything to hold together, even with a bullet going through the entire stack and end cap.

Dimension? Spacer size? What sort of loads?

Like I said. You'll have to reference industry cans or builds on here.

What do you want the can to be capable of?

300 Remington ultra magnum using hot loads with medium to high length projectiles with a 26 barrel
308 Winchester using hot near max loads with mostly high length projectiles with some 150 grain short ones with a 24 barrel
45-70 500 grain 1500 FPS 20 inch barrel
458 socom subs and underwood ammo binary trigger
9mm binary trigger +p+ loads 5.2 barrel
460 Rowland hot loads 255 grain 6.61 barrel
10.5 binary trigger 556 with hot varmint loads
20 556 same loads and binary trigger
7.62x39 10.5 binary trigger golden tiger ammo

Everything but the 9mm and 460 Rowland is 304 stainless and 17-4 cones and the pistols are grade 9 ti with the first 3 baffles being 17-4 and rest grade 5 ti. The 460 Rowland can might also be used on 458 socom with an appropriate sized spacer.

[ECCO Machine]

What’s the blasts chamber size?

It varies a little depending on which model suppressor. My bases for the taper lock brakes thread into the tube .750", and the rear edge of the cone of first baffle is 2.25"-2.5" from the rear of the can, since the brakes occupy the first 2". The length of the cone from the square edge that becomes the skirt varies depending on cone angle and bore size, but the portion of bare tube that forms the blast chamber ends up being 2.5" to 3".

Obviously the brakes change the way the gasses hit the tube in the blast chamber, but nevertheless, the gr. 9 Ti has held up just fine under pretty extreme testing. the Ti was starting to change color from the heat when that strike (more than a strike, really, as it bored a hole through 10 baffles and the end cap, all heat treated 17-4) happened.

[Hannibalbarca]

What’s the blasts chamber size?

It varies a little depending on which model suppressor. My bases for the taper lock brakes thread into the tube .750", and the rear edge of the cone of first baffle is 2.25"-2.5" from the rear of the can, since the brakes occupy the first 2". The length of the cone from the square edge that becomes the skirt varies depending on cone angle and bore size, but the portion of bare tube that forms the blast chamber ends up being 2.5" to 3".

Obviously the brakes change the way the gasses hit the tube in the blast chamber, but nevertheless, the gr. 9 Ti has held up just fine under pretty extreme testing. the Ti was starting to change color from the heat when that strike (more than a strike, really, as it bored a hole through 10 baffles and the end cap, all heat treated 17-4) happened.

What sort of ammo were you running? Because max Saami ammo for 308 Winchester is around 13000-14000 psi for muzzle pressure at 16 inches. And I imagine that brake directed a lot of heat and gas towards certain section of the walls.

How did it go through 10 heat treated baffles? That would be like half an inch of hardened steel plus whatever the cap is made from and it’s all spaced and not homogenous and 308 from a 13 barrel doesn’t have that great of a velocity.
Is 17-4 just really brittle?

[ECCO Machine]

What sort of ammo were you running? Because max Saami ammo for 308 Winchester is around 13000-14000 psi for muzzle pressure at 16 inches. And I imagine that brake directed a lot of heat and gas towards certain section of the walls.

How did it go through 10 heat treated baffles? That would be like half an inch of hardened steel plus whatever the cap is made from and it’s all spaced and not homogenous and 308 from a 13 barrel doesn’t have that great of a velocity.
Is 17-4 just really brittle?

ZQI, Perfecta, Tula ball.

How? Velocity. That's right at the muzzle, and even with a 13" tube, they're moving 2,550-2,600 FPS. Those baffles were .035" thick, the end cap .080", so yeah, that's .430" of steel total. But try pushing a pencil through 13 sheets of paper that are together, then push it through 10 that are spaced apart plus 3 together and tell me which takes less effort.

[Hannibalbarca]

What sort of ammo were you running? Because max Saami ammo for 308 Winchester is around 13000-14000 psi for muzzle pressure at 16 inches. And I imagine that brake directed a lot of heat and gas towards certain section of the walls.

How did it go through 10 heat treated baffles? That would be like half an inch of hardened steel plus whatever the cap is made from and it’s all spaced and not homogenous and 308 from a 13 barrel doesn’t have that great of a velocity.
Is 17-4 just really brittle?

ZQI, Perfecta, Tula ball.

How? Velocity. That's right at the muzzle, and even with a 13" tube, they're moving 2,550-2,600 FPS. Those baffles were .035" thick, the end cap .080", so yeah, that's .430" of steel total. But try pushing a pencil through 13 sheets of paper that are together, then push it through 10 that are spaced apart plus 3 together and tell me which takes less effort.

Well I thought that the bullet would start to deflect and hit an angle and making every successful pass through take more and more velocity.

[ECCO Machine]

Well I thought that the bullet would start to deflect and hit an angle and making every successful pass through take more and more velocity.

Of course it slows down with each impact, but it's still quite different to punch through multiple spaced layers adding up to a given thickness than a homogeneous piece equal to the aggregate.

[Hannibalbarca]

Well I thought that the bullet would start to deflect and hit an angle and making every successful pass through take more and more velocity.

Of course it slows down with each impact, but it's still quite different to punch through multiple spaced layers adding up to a given thickness than a homogeneous piece equal to the aggregate.

Well I thought that in the space between it would angle off center and hit the next baffle an angle increasingly away from 90 degrees as it passes through baffle after baffle.
https://en.m.wikipedia.org/wiki/Spaced_armour

[ECCO Machine]

Well I thought that in the space between it would angle off center and hit the next baffle an angle increasingly away from 90 degrees as it passes through baffle after baffle.
https://en.m.wikipedia.org/wiki/Spaced_armour

What bullets do when they hit things can be quite unpredictable; they don't always behave the way models or common sense suggest they should. Ever shoot at something through an angled automobile windshield? You'd think the angle would deflect the nose of the bullet upward, but they actually tend to nose down and hit below the point of aim on the target behind the glass.

Now, it happened on full auto, so I can't say for sure that another round didn't start to mangle the baffles, but I can tell you that it was very distinctive when it happened, and the rifle stopped running.

I'll snap a photo of it tomorrow and upload to imgur, now that I have an account. It'll be difficult to see inside, especially the way the blast baffle got deformed trying to knock the stack out, but the bullet hole through the end cap is telling.