Thoughts on my design pls

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StoatWithToast
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Thoughts on my design pls

Post by StoatWithToast » Sat Apr 30, 2016 11:03 am

Hey,

Been lurking here, reading up.
Please have a look at my first design, for a 22LR with subs, 3D printed in plastic (prototype in ABS).
Barrel fixing is 1/2 UNF (20 tpi) as that seems to be the way its done in Europe, which seems really odd to me, but hey ho.

The main baffle is printed in one piece and is a take on the K-baffle, but with the changes suggested in that thread about air-gun suppressor design (also 3D printed) - as it's 3D printed, it'd be hard to machine the design.
Also, as it is 3D printed in plastic, some issues arise (other than just heat management) - how to print it strong enough and how to print it at all. It also means I have some unused space filled with plastic instead of controlling the gas expansion.
This ended up with me putting the whole lot into a tube. I have another design with this tube having shaped cross-section spirals in for marginally more expansion space and allowing direct contract with the pressure containing tube.
It also means it can be tough to print normal mono-block cores with supports between baffles going to the limits of the ID tube tolerance as those all need support too and aren't that strong when the print layers are perpendicular to the bore of the gun.

The thread is the barrel end of the tube. This screws into the blast baffle (max height I can print is 5") which is the last pic - basically a thick (for strength) button baffle, but with circular waves on the surface. That itself threads into a barrel connection and end cap.

All fits inside of a tube to contain the pressure and the screw fitments keep the separate tube locked together and locked to the tube. Biggest risk is the layers delaminating and the far end being pushed off.
Early tests seem to be good, but not got a video of it in use yet or a proper dB meter to check it.

Cleaning is a PITA but powder solvent looks like it is ok on Nylon and ABS so I may just have to be very liberal with in / have a tall jar filled with it and submerge the baffles in it to clean it for now.

Perspective views of a cut-away
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Image
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Side view
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Blast baffle
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Capt. Link.
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Re: Thoughts on my design pls

Post by Capt. Link. » Sat Apr 30, 2016 1:03 pm

While its not a requirement adding your country helps avoid the legal questions that will arise on a largely American web page.
The performance is what counts not what others may think of the design.As you have already built it what are your impressions and on what hosts.
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!

quietoldfart
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Re: Thoughts on my design pls

Post by quietoldfart » Sat Apr 30, 2016 2:02 pm

I'm a bit confused - is the prototype in ABS or is ABS the finished suppressor material? Or both? ABS has a rather low melting point. Easily burned with even a match or candle flame. Rimfire ammunition, even relatively low powered types, generate considerable heat in the blast chamber and beyond for several baffles. At the very least I'd expect to see the sharp edges on those blast baffle steps to burn and start falling apart within a hundred rounds or less. Even in a metal alloy, such knife edges on a blast baffle seem ill advised, likely to round over with use, but only up to a point at which the remaining rounded steps might be fine.

The adherence to the inside cone shape seems to create an unnecessary bulkiness in the baffles at some points. Why not open out the expansion volume, leaving only the thickness necessary for strength? Of course if this is in ABS... I suppose you'll need all that material to prevent the whole thing from collapsing forward. But if that's the case then I'd go further to suggest the wall thickness of the noses on those baffle faces is too small, likely to fail as well, besides presenting too long a core 'tube' space which prevents outward expansion of pressure. Shortening the noses somewhat should help with suppression efficiency.

There seems not to be any sort of notching or cross-bore venting cut into the noses of the baffle faces. Providing routes for gas escape is not the same as 'working' the gases. If this were a modified K design, there should be a scoop in each face at the entry point to push pressure across the bore, not just a passive receptacle for gas to flow incidentally.

StoatWithToast
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Re: Thoughts on my design pls

Post by StoatWithToast » Tue May 03, 2016 7:57 am

Hey - thanks for the replies.

This is just the prototype, but has been printed in ABS.
The current blast baffle is hard to check on as there's no holes in the printed tube on the current version, but I'll add the spiral slots & holes back in. That should also allow more gas to contact the metal pressure containing tube and dissipate the heat better.

Noted on the nose lengths - they are only there are they seem integral on the K's - I'll remove them and print a new one to compare.

Not sure how well it comes across in the pictures, but the design has a spiral on the scoop faces that converge on a scoop that should act like a mudguard on a bike and directs the gas directly across the centre holes. The far side of that also has a counter spiral, but the closeness of the baffles and the geometry means there's still an excess of material that side which I see no easy way to design out.

The way it has been modelled is to have a blank tube rotated round for the rough baffle shape then the complex geometry has been removed and the corners radiused.

I think a better way would have been to design a single baffle then replicate the finished article out as needed then link together as needed.

I did see an oval mono-block core, but it looked like it had no real turbulence drivers in the design.

Traditional style mono-cores also seem to have a lot more FRP and I need this unit to be quiet from the first to the last round. It's also on a bolt action rifle so most of the rounds come through like the first anyway :)

Cheers,

Dave
Last edited by StoatWithToast on Tue May 03, 2016 9:38 am, edited 1 time in total.

StoatWithToast
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Re: Thoughts on my design pls

Post by StoatWithToast » Tue May 03, 2016 9:34 am

Forgot to say - my first few efforts were separate cone baffles, but making them lock became a problem - a design aim is to not have to machine the outer tube at all - only have 3D printed parts and a (captive) metal nut to fix to the muzzle.

I then looked at something akin to a Tesla one-way-valve, but with a straight line to the exit - making it far less efficient to the point of being useless.

I can print with the layer plane parallel to the bore to make printing more traditional style mono-cores easier, but the connecting threads will not come out nearly as sharp so I may need a different locking solution... not a bad idea anyway as the mating thread parts take up a lot of extra diameter inside the tube.

Hopefully I get back to the range in later May to do some video of it in action - I'll probably try to take several main baffle and blast baffle units with me for comparison - will have to use my phone for the reading though - and the local range can get loud so not the easiest place to test.

I'll probably make a test rig (spud launcher type thing) with as consistent as I can get it bang so I can have a better control to test them on. Obviously not the same as no round going through too, but much less time needed to evaluate a design before I modify it.

Also, I'm shooting in various places in Europe, so no NFA / Stamp Duty / Form 1 / USA based issues (one of the very odd quirks I find with gun ownership in the US!)

DanielWilson
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Re: Thoughts on my design pls

Post by DanielWilson » Tue May 10, 2016 1:38 pm

StoatWithToast wrote: Also, I'm shooting in various places in Europe, so no NFA / Stamp Duty / Form 1 / USA based issues (one of the very odd quirks I find with gun ownership in the US!)
Odd quirks, indeed. We have far more liberty than you on the firearm and far less on the suppressor.

DanielWilson
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Re: Thoughts on my design pls

Post by DanielWilson » Tue May 10, 2016 1:39 pm

What material will your final product be made of? My very limited machining knowledge does not show me a way to build that design on a lathe, milling machine, etc.

a_canadian
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Re: Thoughts on my design pls

Post by a_canadian » Tue May 10, 2016 1:46 pm

He's been talking about printing it. Metal powders for the finished product seem likely, though prototyping is in plastics.

DanielWilson
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Re: Thoughts on my design pls

Post by DanielWilson » Tue May 10, 2016 11:00 pm

Aha, I wasn't sure printing in metal would be an option. Strong enough for the pressure ... since we're talking rimfire?

a_canadian
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Re: Thoughts on my design pls

Post by a_canadian » Tue May 10, 2016 11:19 pm

There's a company in New Zealand making printed suppressors for .308“ and such. Looking for a US manufacturer last time I saw the guy around here. Can't recall the name, but the finished product looked insanely high quality. Reported to have excellent suppression too. And strength was a thing he talked about. Stronger than a welded can of similar weight. Ah, here's something. Member name is ODL and some of his work can be seen here:

viewtopic.php?t=110068

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