Design Testing On The Cheap

Fudmottin · Post by **Fudmottin** » Sat Mar 07, 2009 5:49 pm

I'm assuming not all F1 Silencer builders will take the safe route with a standard design. Or they might wish to test several of the standard designs to see what seems to work better.

The problem with F1 is you can't build a bunch of suppressors to see which one works best. You are stuck with one suppressor per tax stamp and that is that.

So the only way to test a design is by using some kind of model. An ideal model would probably involve blasting a puff of high pressure air into a plastic mock up of your design and measuring the pressure at the exit aperture. Unfortunately you don't see what's going on inside the model.

A computer model would be pretty nice. You can get it to render visualizations for you. However, what the computer model says will happen and what actually does happen may be entirely different things. Also the software might be rather pricey which cuts into the whole saving money idea behind an F1 can.

I'm working out a test concept that is essentially an analog computer. It has some limitations of course. I'll talk about those after the sketch of the testing platform I drew.

The general idea is to cause water to drop through a pipe under gravity and exit into a chamber that simulates the cross section of the suppressor tube. The water should be a colored saline solution to facilitate visualization and simulate the increased pressure in the flow.

The water in the table should be held at a constant depth. Outlet holes or something to allow it to spill out would be a good idea. The depth of the water will represent pressure since water is incompressible unlike air.

This is a 2D modeler, not 3D. Not all designs can be modeled. For example, cone and delta baffles will look the same. Also a slug should probably be drawn through the tube to simulate a bullet wake when the water in the reservoir is released. It would also be a rather good idea to use a video camera to record the results of a test so you can play back in slow motion.

Anyway, this is basically an idea stolen from a middle school earth science class and adapted for a specific purpose. It should do a reasonable job simulating the Newtonian Mechanics of a fluid flow within limitations.

Any ideas on the usefulness of this thing or how to improve it?

Selectedmarksman · Post by **Selectedmarksman** » Sat Mar 07, 2009 5:58 pm

Or you could use the fluid dynamics simulator built into SolidWorks. Computer aided 3d modeling of your design and virtual 'testing' to boot.

Fudmottin · Post by **Fudmottin** » Sat Mar 07, 2009 7:39 pm

I could only find academic pricing for solidworks and no OS X version.

Am I expected to be a mechanical engineer and machinist to build an F1 can?

sonanth · Post by **sonanth** » Sat Mar 07, 2009 11:27 pm

Fudmottin wrote:Am I expected to be a mechanical engineer and machinist to build an F1 can?

Yep.

RavenArmament · Post by **RavenArmament** » Sun Mar 08, 2009 11:18 am

Solidworks is Windows only, no Mac (I have a Mini).

I bought a cheap Walmart $300 PC for my R&D machinist to run SW in. There's TurboCAD for Mac, but it isn't as sophisticated as SW.

Neil · Post by **Neil** » Sun Mar 08, 2009 11:36 am

Without going out of my way to be too harsh, let me just say a water model would be totally worthless. Gas is compressible. Water, for all practical purposes, is not. Suppressors work by alternately expanding and compressing the gas. The idea is to "waste" as much energy as possible, dropping the pressure before the gas exits the suppressor.

jjgow · Post by **jjgow** » Sun Mar 08, 2009 12:11 pm

If it's too complicated to buy Windows for $90 and install it on your computer, it'll probably be too complicated for you to operate any sort of machinery.

RavenArmament · Post by **RavenArmament** » Sun Mar 08, 2009 3:21 pm

Where can you find a full copy of Windows for $90? I've only seen them for $200.

Fudmottin · Post by **Fudmottin** » Sun Mar 08, 2009 6:49 pm

Turn the gas back on itself.
Make it work against itself.

I didn't expect to get flamed for this one.

CKOD · Post by **CKOD** » Sun Mar 08, 2009 6:50 pm

freakshow10mm wrote:Where can you find a full copy of Windows for $90? I've only seen them for $200.

Not 90, but
http://www.newegg.com/Product/Product.a ... 6832116515
for $140,

Once you expand to CNC work I'm pretty sure things will be easier to have a PC.

RavenArmament · Post by **RavenArmament** » Sun Mar 08, 2009 7:43 pm

Well, I'll be. Thanks. Been looking for a cheapie version for my Mac Mini. I got a cheapie PC for CAD software. Going to build a dedicated computer for the CAD/CAM/CNC outfit. Deciding between a big ass "laptop" or a standard PC tower.

And I was told earlier in life all the neat design programs were for Mac.

Right now I'm playing around with Dolphin but am looking into SW. I'll probably go with MasterCAM as the CAM package.

Fudmottin · Post by **Fudmottin** » Sun Mar 08, 2009 11:39 pm

All the good stuff is for iPhone now

Bits · Post by **Bits** » Mon Mar 09, 2009 9:16 am

freakshow10mm wrote:Going to build a dedicated computer for the CAD/CAM/CNC outfit. Deciding between a big ass "laptop" or a standard PC tower.

I'd recommend a tower (mini or otherwise, doesn't have to be huge). If you're going to have this machine in a shop environment, you'll want a machine that runs as cool as possible (read: lots of fans), and when the bearings start to squeal you'll want to be able to replace them. Drives and memory are generally cheaper, too.

pneumagger · Post by **pneumagger** » Mon Mar 09, 2009 10:17 am

if it's for a PC that will see little or no internet connectivity, I'd just pirate XP and Solidworks.
Heck, if we're pirating stuff, might as well well go for ProE and Vista.

mactool · Post by **mactool** » Mon Mar 09, 2009 10:56 am

dont go for ProE, It causes Tourettes syndrom, belive me IÂ´ve been there. I was banned from church

I would recomend Cocreate soliddesign, og Siemens NX4

BoilingLeadBath · Post by **BoilingLeadBath** » Mon Mar 09, 2009 2:01 pm

Does cosmo flow works do dynamic situations? I note that the student version (That's all I have access to) only does static situations.

Suppressors, as evidenced by the heavy dependence upon volume, are reliant upon the dynamic nature of the flow inside them - and if cosmo can't do dynamic situations, it could give you misleading results.

********

Oh, by the way, given the ratio between muzzle and atmospheric pressure... I don't think you'll need to fill the test-tray with water prior to the test for reasonably accurate results.

Fudmottin · Post by **Fudmottin** » Mon Mar 09, 2009 2:52 pm

You make a good point about the pressure difference. And if I don't use water to start out, there is no reason for walls around the table. The water could be allowed to just run off since the atmosphere is not going to gain any pressure from a few grains of gas being added to it.

My hope for the water table is that it would represent a slow motion approximation of the fluid flow. The reason I had water to start out with is so that I would have water hitting water.

Since SW with Cosmo is so highly recommended, I expect the water table could be simulated. It would be much easier to compare the results against a water table than to compare against a real suppressor.

The suppressor is a far more complex situation than the water table. It would require more CPU cycles to emulate in a virtual environment. If SW can replicate the water table, I would have more confidence in it replicating the suppressor. If it can't, well, I would have less.

If someone would care to model it, I would love to know how long it takes for a barrel that is 16" long x 30 caliber to return to atmospheric pressure after the bullet clears the barrel and a 10gr charge of powder was used. A good charge for 300 Whisper would be 15gr of powder. Subsonic loads would use 8-12 depending on bullet weight (and bearing surface).

Post by **silencertalk** » Mon Mar 09, 2009 3:09 pm

CKOD wrote:
freakshow10mm wrote:Where can you find a full copy of Windows for $90? I've only seen them for $200.
Not 90, but
http://www.newegg.com/Product/Product.a ... 6832116515
for $140,

Once you expand to CNC work I'm pretty sure things will be easier to have a PC.

http://www.newegg.com/Product/Product.a ... 6832116511

RavenArmament · Post by **RavenArmament** » Mon Mar 09, 2009 10:43 pm

Hot damn, thanks Mr. Silvers!

Bits · Post by **Bits** » Tue Mar 10, 2009 6:41 am

Nota Bene: the first link was for XP Pro, the second link is for XP Home. Subtle differences between the two, the most irksome of which is that XP Home doesn't support multiple processors (multi-core yes, multi-proc no). That's not usually a show-stopper, but you said you were building a machine for CAD work, and so multi-proc support may be a consideration.

Additional info: http://www.winsupersite.com/showcase/wi ... me_pro.asp