My suppressor design

[daPhoosa]

Hi all,

With the possibility of MN getting legal suppressors, I've started designing one.



Here are the major design points:

• For a 300 Blackout 8.5" barrel (subs and supers)
  Direct thread
  Expected material: 17-4 PH SS
  OAL 6"
  OD: 1.625"
  Split blast chamber to partially shield the outer tube (prevent the initial expansion wave from transfering noise by directly contacting the outer wall)
  Each baffle has 3x offset radial turbulence ports, alternating spin direction each baffle
  Expected weight 12.5oz
  5x baffles + end cap
  Baffle spacing decreases when approaching the end cap
  Perforated spacing skirts allow hot gasses to contact the outer tube to increase cooling while also inducing turbulence

I want to keep this light and short since it will be attached to an AR pistol (eventually SBR), while also getting reasonable noise reduction. I also hope it has reasonably low back pressure to minimize reverse gassing.

Let me know if you have any thoughts or questions. In a best case scenario I've got a long wait until I have to finalize the design (and it's possible our governor will break my heart...), so I have plenty of time to make changes and adjustments.

For reference this was entirely designed in OnShape and rendered in Solidworks.

~Phillip

[T-Rex]

Hello Phillip. I'll give you an A for design and ingenuity and we'll move on from there

Sorry the text seems small, it's dependent on the original image size.

[doubloon]

It is pretty.

Nice feedback trex, all I could come up with was the void and the size of the "mouse holes". Didn't even notice the holes in the end cap.

[daviscustom]

Beautifully rendered, but your design seems to be all about turbulence and not enough about catching and slowing down the gas that is trying to get out. Your cones are pretty shallow and full of holes too....not sure the turbulence alone will do it. If you are flush with cash and machine time I would be curious to hear how it does, but if it were mine I would make some changes. I'll be curious to hear everyone's suggestions.

If it were mine I would extend the outer blast chamber toward the back of the can and utilize the wasted space in the back as a space for the threaded mount. Port that tube behind the blast cone so it acts as a muzzle brake, make the cones deeper, port the outer shrouds only at the front edge (at the base of each cone), and extend the cone on the endcap back way farther....and loose the extra weight around the cone in the endcap.

Oh and loose the extra holes in the front cap.

[ghostdog662]

The first quarter has a serious amount of wasted volume.

[daPhoosa]

Thanks for the input guys, I appreciate it!

Here's some answers and clarifications:

Why is there a "bump" here?
The ID of each end of the outer tube is threaded. The bump is a reinforcement so if I drop the tube during cleaning it is less likely to deform and make re-assembly impossible. There is also a less obvious increase in diameter over the threads to compensate for the loss of strength due to the material removed by the threads.

Use smaller holes here to trap/slow gas movement.
I've shrunk them. Still thinking about what a reasonable size/number is.

Not sure this area is large enough to be useful.
The intention with that geometry is to give the spacing skirt a very very small amount of flex so that baffle stack growth due to heat does not cause excessive stress to the outer tube. I maybe over thinking this problem and a simpler option would be fine.

I don't think this skirt angle will server any purpose with those large holes in the side.
My main intention with the skirt is to act as an spacer. The angle and holes are intended to make it lighter while also allowing the gasses to flow against the outer tube and cool off. I wanted to avoid a spacer that insulates and reduces the effective internal volume.

Why are there holes in the end cap?
I'm really not sure what I want the end cap to look like right now so I drew this quickly to have something to start with. The holes were to reduce back pressure.

Looks quite thick for subsequent baffles.
Agreed. Fixed.

Remove (turbulence ports) from 1st baffle to promote rearward gas movement.
Removed, although I'm still thinking about this. I might just make them really small. I'm currently stuck on the idea of using "jets" to disrupt and introduce turbulence in to the central gas flow, so I'm struggling with dropping them entirely.

Are you planning a thread mount or other?
That surface is 5/8-24 threads for a 30 cal barrel (300 blackout). I've just been too lazy to model threads into the surface.

What is the purpose of this void?
Weight and length savings. Pushing the rear tube threads back like that allows me to use the space over the barrel threads for my secondary expansion chamber while reducing the overall length by .44" and dropping 2oz of weight (compared to placing the rear tube threads over the barrel threads). Weight and length minimization are high on my priorities list. In this case If i move the rear tube threads to the traditional location over the barrel threads I gain ~2% more usable internal volume but increase my weight by 2oz (a 17% increase in weight). I'm not convinced this is a good trade off for MY priorities.
I'm still thinking about it, there may be a way to get the space without adding as much weight (without designing something that is un-machinable).

Here's a screen shot with a section of barrel "threaded" into it (outer tube removed):

Sorry I don't have a cross section view as OnShape doesn't yet support section views of assemblies. If I was at work I'd send it over to solidworks, but I'm at home right now.

...your design seems to be all about turbulence and not enough about catching and slowing down the gas that is trying to get out.
I'm not sure these ideas are mutually exclusive. Turbulent flow will tend to have a harder time exiting the suppressor, effectively catching and slowing the gas. Part of my theory with this design is that any time I can get the flow to run into it's self, it is using up energy and slowing down. With this in mind, the radial turbulence ports are intended to both disrupt the central gas column and impart rotation to it. Each baffle then alternates the direction of rotation to try to get the flows to become as turbulent as possible. This might be a bunch of silly talk, but for now I want to stick to it while evaluating any ideas that could work better.

Overall, I know this design is not traditional. At this moment I'm not incline to just copy another design and run with it. The input so far has been awesome and I appreciate the thought in time people have put into their feedback.

Regards,

Phillip

[gunny50]

I do think it is a nice design, would make ports in connector bigger than last model.
Gas needs enough space to flow true to fill secondary room around your connector.
In regards to holes in spacer.
Make size not to big and keep close to the end, where they meet with the next baffle.
Gas will than fill the secondary space and have a longer way back thrue your frustration coned nose. Make sure that ports in spacer are NOT in line with the ports in your frustration nose.
These cross jet ports need pressure to work to a optimum.

With regards to threading your connector and having maximum volume, there are tools that allow machining under the rim / threaded portion. They are also used for front machining when you need an O-ring on front plane. I will check tool number in my lathe drawers.



Gunny

[daviscustom]

...your design seems to be all about turbulence and not enough about catching and slowing down the gas that is trying to get out.
I'm not sure these ideas are mutually exclusive. Turbulent flow will tend to have a harder time exiting the suppressor, effectively catching and slowing the gas. Part of my theory with this design is that any time I can get the flow to run into it's self, it is using up energy and slowing down. With this in mind, the radial turbulence ports are intended to both disrupt the central gas column and impart rotation to it. Each baffle then alternates the direction of rotation to try to get the flows to become as turbulent as possible. This might be a bunch of silly talk, but for now I want to stick to it while evaluating any ideas that could work better.

Didn't intend to say they were mutually exclusive. I was referring to the balance between the two being a little heavy towards turbulence (in my estimation). Sounds like Gunny and I are on the same page on the porting of the outer skirts....shrink the ports and move them to the front edge of the bell to create a cavity for the gas to be trapped more....as the gas comes off the cone it will go through the ports and backwards to fill that space. If you don't want to do the muzzle brake, I think I would put more ports around the front of that blast cone to reduce back pressure and make better use of that outer blast chamber.

It isn't entirely about flow, there is an initial momentary pressurization that will try to fill every space in the can....then the release as the pressure pulse subsides and the gas starts trying to get out.....give it lots of places to fill, and then make the path back out as long and turbulent as possible.

[T-Rex]

Thanks for the input guys, I appreciate it!

Here's some answers and clarifications:

Why is there a "bump" here?
The ID of each end of the outer tube is threaded. The bump is a reinforcement so if I drop the tube during cleaning it is less likely to deform and make re-assembly impossible. There is also a less obvious increase in diameter over the threads to compensate for the loss of strength due to the material removed by the threads.
Personally, I wouldn't waste machining time, worrying about this. After you harden that 17-4, you'll need to reinforce the floor you drop it on. Also, you'll need to machine that tube from solid bar. This lets you make the rear thread area have a thicker wall to compensate for the threads, while a thinner wall moving forward. The front threads will be fine, structurally wise.

Use smaller holes here to trap/slow gas movement.
I've shrunk them. Still thinking about what a reasonable size/number is.
Small. Pressure will get the gas in there. Small holes will trap it longer.

Not sure this area is large enough to be useful.
The intention with that geometry is to give the spacing skirt a very very small amount of flex so that baffle stack growth due to heat does not cause excessive stress to the outer tube. I maybe over thinking this problem and a simpler option would be fine.
Over-thinking. Spacers are used in the majority of suppressors, w/o known issues you are pondering. Line it up, so the spacer does that job, w/ less machine time.

I don't think this skirt angle will server any purpose with those large holes in the side.
My main intention with the skirt is to act as an spacer. The angle and holes are intended to make it lighter while also allowing the gasses to flow against the outer tube and cool off. I wanted to avoid a spacer that insulates and reduces the effective internal volume.
An angle requires more material. If your going to use giant holes, to reduce weight, do it on a thin, "tube" spacer. They can get progressively thinner towards the end cap. Worried about weight? Think Ti.

Why are there holes in the end cap?
I'm really not sure what I want the end cap to look like right now so I drew this quickly to have something to start with. The holes were to reduce back pressure.
Back pressure is keeping the gas in the can. Not too sure your design is going to have as much as you think.

Looks quite thick for subsequent baffles.
Agreed. Fixed.

Remove (turbulence ports) from 1st baffle to promote rearward gas movement.
Removed, although I'm still thinking about this. I might just make them really small. I'm currently stuck on the idea of using "jets" to disrupt and introduce turbulence in to the central gas flow, so I'm struggling with dropping them entirely.
Your Blast Baffle is there to control that initial release of pressure/gases. You want it to stop them from moving forward. Let it scoop the gases rearward. Not too sure these ports are going to perform as you wish or have that great an effect.
1. You could use Bernoulli to calculate the pressure loss, but my thought is the extra holes could actually increase pressure, by increasing flow, inside the next baffle cavity.
2. The thin wall just won't create as much of a redirection or turbulence you are planning. I would recommend a wall of, at least, 50% the hole radius, to have a greater effect. Adding material is not the way we want to go.

Are you planning a thread mount or other?
That surface is 5/8-24 threads for a 30 cal barrel (300 blackout). I've just been too lazy to model threads into the surface.
I know the feeling

What is the purpose of this void?
Weight and length savings. Pushing the rear tube threads back like that allows me to use the space over the barrel threads for my secondary expansion chamber while reducing the overall length by .44" and dropping 2oz of weight (compared to placing the rear tube threads over the barrel threads). Weight and length minimization are high on my priorities list. In this case If i move the rear tube threads to the traditional location over the barrel threads I gain ~2% more usable internal volume but increase my weight by 2oz (a 17% increase in weight). I'm not convinced this is a good trade off for MY priorities.
I'm still thinking about it, there may be a way to get the space without adding as much weight (without designing something that is un-machinable).
You don't need as many threads as you think. Your proposed bast chamber will be 2 point, where it meets the first baffle/outer tube and the distal threads. You could get away with .2-.3" of threads, especially meeting a shoulder. A trepan or "scoop" could remove plenty of material, in this area.


Regards,

Phillip

-Tom

[Bendersquint]

Interesting design that something incredibly similar has been done before, you are going to run into a legal issue as this would fall under the Omega patent and would be illegal to make without permission from the patent holder.

[Capt. Link.]

Interesting design that something incredibly similar has been done before, you are going to run into a legal issue as this would fall under the Omega patent and would be illegal to make without permission from the patent holder.

http://www.google.com/patents/US6575074


Almost every design is a variation of the Finn design.
Please educate the community on how this falls under patent infringement with the Omega.

[daPhoosa]

Interesting design that something incredibly similar has been done before, you are going to run into a legal issue as this would fall under the Omega patent and would be illegal to make without permission from the patent holder.

You might need to clarify this. After reading the Omega patent, I don't think I have anything to worry about. My major design elements are listed in their prior art section.

[sillycon]

Interesting design that something incredibly similar has been done before, you are going to run into a legal issue as this would fall under the Omega patent and would be illegal to make without permission from the patent holder.

I don't think SiCo is going to sue someone over a single Form 1 can with a design the individual came up with on his own.

If it were a business, well, maybe they'd sue, maybe they wouldn't. Even if they did, it'd probably settle out of court as there likely isn't enough money to make a full-on battle worthwhile for either party. Diminishing returns and all that, you know?

[Capt. Link.]

I would not test the very gracious Mr Gaddini in his right to sue.He has in the past granted permission by just asking.His design is a excellent one and worthwhile.
A simple ported cone design will out perform your design as drawn and modification of your design as suggested could be infringement .I hope you don't get your heart broken but depending on a politician is never a good bet.
-CL

[daPhoosa]

Well, I may have to ask permission then before I make chips. We'll see what my design looks like by the time I get (if I get) my Form 1 back.

Ok, I've been convinced. I have dropped radial turbulence ports on the cones. If I clip the cones, is there a consensus as to whether a single clip or multiple clips makes a difference?

Additional changes:
* Shortened all of the skirts enough to add an additional baffle bringing the count to 6.
* Removed the large weight reducing holes in the skirts
* Added holes in the skirt face closest to the next baffle to allow the area of the between the skirt and outer tube to become and additional expansion chamber.
* Increased the cone lengths on each baffle







These changes bring the expected weight to 13oz. I am strongly considering making the last 4 baffles from Ti. That would save ~2oz. Would it make sense to do 2x 17-4SS, 2x 6-4 Ti and 2x 7075-T6 (hard coat)? Would the wear on the Al baffles be too high even though they are the last ones in the stack (remember this is for 300Blk, not 300WM). I don't expect it to ever be used on an full auto upper and I'll probably shoot 500-1000 rounds per year. It's possible I'd test it on an 556 upper with full length barrel for kicks an giggles, but I doubt it would see many rounds.

Additional responses/notes:
I am aware of trepan tools and how they could be used in this type of situation. I am also designing around the limitations of the CNC machines I have available to me.

The thread length for the outer tube is 0.25". The picture may make it look like more, but it's really pretty short.

The profile on the OD of the outer tube is trivial to machine and probably the least time consuming part of this entire project. I've grown to like the look of the bumps on the ends and will probably keep them even if they're not needed.

The through diameter of the first baffle is 0.340" and each subsequent baffle is 0.004" larger than the previous. Is this typical/ reasonable? I can hold a high degree of precision in machining the parts, but the threads on the barrel and adjacent shoulder are a bit of an unknown.

Thanks again for the comments and suggestions.

Regards,

Phillip

[Fulmen]

Honestly, this topic of patent infringement always annoys me.

First off, how will they ever know? And do you really think a patent holder that stumbled over this thread would take the time to track down the posters identity and drag him to court? Do you really think that would be worth the time, effort and cost of litigation? Can anybody come up with an example of this ever happening?

Secondly I have to challenge the premise that an amateur is obligated to check prior patents every time they make something. It's just not possible, nor is it a reasonable demand.
I know these cases are somewhat different as we tend to study commercial products for ideas, but most designs are fairly simple in principal and relies on general principles for silencers. Honestly, when was the last time anybody saw something truly new and unique in this field?

[T-Rex]

daPhoosa

It's a neat design, but you're still stuck between a cone and a K. If you moved the skirt of the spacer out to meet the tube, you'd be able to profile a longer cone. I think this would be the largest improvement. Regardless of how you plan to disrupt the gas flow, increasing your cone size will strip it from the centerline, guaranteed.

The distal "cup" portion s still goofy looking , but won't affect performance.

I have yet to taper my bore-line. I do a visual inspection, with final fitment.

In the end, you're only down $200 and the cost of material, if you're dissatisfied.

[Rich V]

Others have already commented on the design shortcomings.

My thought, how are you going to machine the complex shapes of these baffles? If you don't have access to a decent CNC work center you will not be making them as rendered in your drawing.

[daPhoosa]

Others have already commented on the design shortcomings.

My thought, how are you going to machine the complex shapes of these baffles? If you don't have access to a decent CNC work center you will not be making them as rendered in your drawing.

I have access to some nice CNC machines. These parts are designed specifically for the machines, tooling and software that is available to me. Making parts that look exactly like the pictures will take little effort.

I have a background as both a machinist and mechanical engineer. When I design parts, manufacturability is the first thing I worry about. If it is impossible to make, it doesn't matter how well you think it will function (or how pretty it is).

[Rich V]

Others have already commented on the design shortcomings.

My thought, how are you going to machine the complex shapes of these baffles? If you don't have access to a decent CNC work center you will not be making them as rendered in your drawing.

I have access to some nice CNC machines. These parts are designed specifically for the machines, tooling and software that is available to me. Making parts that look exactly like the pictures will take little effort.

I have a background as both a machinist and mechanical engineer. When I design parts, manufacturability is the first thing I worry about. If it is impossible to make, it doesn't matter how well you think it will function (or how pretty it is).

I'm jealous
My stuff is decidedly old school manual machines.
Carry on sir!

[daPhoosa]

daPhoosa

It's a neat design, but you're still stuck between a cone and a K. If you moved the skirt of the spacer out to meet the tube, you'd be able to profile a longer cone. I think this would be the largest improvement. Regardless of how you plan to disrupt the gas flow, increasing your cone size will strip it from the centerline, guaranteed.

The distal "cup" portion s still goofy looking , but won't affect performance.

I have yet to taper my bore-line. I do a visual inspection, with final fitment.

In the end, you're only down $200 and the cost of material, if you're dissatisfied.

My cone length is only a little shorter than 60deg cones inside an 1.5OD tube with spacers. I don't have the sharp inside corner next to the tube ID that straight cones have, but I doubt that feature is of much value. I can easily make the cones longer, I'm just trying to figure out where good enough is. It is rather a bummer that baffles are a one shot deal.

I almost removed the cup feature, but I liked the way it gives slightly more room for the holes leading to the secondary chambers.

[BearTHIS]

Honestly, this topic of patent infringement always annoys me.

First off, how will they ever know? And do you really think a patent holder that stumbled over this thread would take the time to track down the posters identity and drag him to court? Do you really think that would be worth the time, effort and cost of litigation? Can anybody come up with an example of this ever happening?

Secondly I have to challenge the premise that an amateur is obligated to check prior patents every time they make something. It's just not possible, nor is it a reasonable demand.
I know these cases are somewhat different as we tend to study commercial products for ideas, but most designs are fairly simple in principal and relies on general principles for silencers. Honestly, when was the last time anybody saw something truly new and unique in this field?

Consider me firmly in this camp. Most IP lawyers I know will be honest that they are often times guessing on potential court rulings, chances of things even be infringing, or the likelyhood of a potential competitor to their client litigating the matter... They still get paid. If they aren't all that sure of what is/will be ruled or litigated it's hard to take internet non-lawyers seriously on this matter of an individual making a can for personal use in an industry that is small potatoes in the everyday world.

[daviscustom]

The sweet spot on the porting of those bells may require a little trial and error, but it looks more like something I would be interested in trying, not exactly what I envisioned, but an interesting solution. Even if you end up erring on the side of too much porting, it would still leave you with a long path for the gas to travel forward and then backward to get to the bore as long as your porting is confined to that flat portion of the bell.

I agree, stretching the cone length seems like a good idea.....traps a larger volume in front of the bore hole and makes that larger volume have to travel further backwards to get out...probably would harness more pressure to push out into those secondary chambers too.

I would stretch out the cone on the front cap too.....could be a simple tube to create as much volume as possible....less pressure in the can as you move forward so larger volumes will allow more expansion from the boreline....nice big gaping cavity to swallow up what makes it to the front of the can.

You could weld the can and do away with all the threads and the extra weight you are wanting to loose.....if you have to make it serviceable you could probably get everything out with just a threaded front cap and a threaded rod to push out the baffles (pushing from the barrel mount).....with it being 17-4 you should be able to use nasty solvents to break up any crud that builds up.

[daPhoosa]

Update:

* Increased cone lengths
* Clipped cones
* Added wrench flats on barrel mount
* Added hole pattern on end cap to allow for tightening/loosening with special tool
* Added Sierra 220 Match king for reference ('cause nothing says a design is legit like a section view that catches the bullet flying through...)

[daPhoosa]

I've now got an end cap I'm basically OK with. Still thinking about what I want the end cap to do, but this design should be reasonable at reducing gas flow rate.

All of the baffles will be compressed by a total of 0.005" when the end cap is in place. This should hold the baffles solidly in place.







Made completely from 17-4PH this should weight 13oz. I am considering making the end cap and five baffles from 6-4Ti (Outer tube, blast baffle and blast chamber/barrel mount would still be hardened 17-4PH). This would bring the weight down to slightly over 10oz. With the 8.5" barrel I already have, the combined weight will be less than an average 16" barrel with A2 while also being three inches shorter. If I am going to SBR my pistol lower, I want it to still feel like a SBR even with the suppressor attached.