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First post and first gun- 6mm SML (Small Munitions Launcher)

Built a miniature cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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First post and first gun- 6mm SML (Small Munitions Launcher)

Unread postAuthor: julktyl » Sun Nov 22, 2009 5:18 pm

Hey everyone, this is my very first attempt at a pneumatic cannon so I decided to start small and make a mini. First, I will list the specs for the 6mm SML:

Projectile - 6mm, .20g plastic airsoft BB
Barrel - 5 in. steel brake line
Piston - 1/2" steel rod attached to 1/8" section of pencil eraser (sealing face)
Chamber - 3" section of 1-1/2" dia. Sch. 40 PVC pipe
Filling valve - 1/4" quick connect
Firing valve - Air blow gun
Piston housing and the rest of the gun - 1/4" brass pipe fittings

Overall, the SML cost less than $15 to build. The only things I had to buy were all of the brass fittings and the brake line, the other things were laying around in my dad's garage.

Next on the agenda:
- laser sight (the octagonal shape of the piston is perfect for attachments)
- custom paint job
- more ergonomic hand grip/trigger
- stand for stationary use

I have yet to test the SML and will hopefully be able to tonight or tomorrow. As soon as I figure out if it will work I'll post demonstration video with damage. More pictures are soon to come as well.

Questions/comments/constructive criticism are always welcome.
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SML with pen for scale
Last edited by julktyl on Sun Nov 22, 2009 7:48 pm, edited 2 times in total.
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Unread postAuthor: maverik94 » Sun Nov 22, 2009 5:29 pm

cool, I like it. It is simple yet effective. Have you modded the blogun for efficiency?
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Unread postAuthor: POLAND_SPUD » Sun Nov 22, 2009 5:30 pm

wow that's pretty cool.... nice first build

you probably are aware that it would be better to use all metal chamber and use high pressures, right ?
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Unread postAuthor: julktyl » Sun Nov 22, 2009 5:37 pm

maverik94 wrote:cool, I like it. It is simple yet effective. Have you modded the blogun for efficiency?


No I haven't, I was unaware that you could. I'll have to check into that.

POLAND_SPUD wrote:wow that's pretty cool.... nice first build

you probably are aware that it would be better to use all metal chamber and use high pressures, right ?


I thought about that at first but couldn't find any kind of metal tubing. What do you suggest using for a metal chamber?

Thanks for the comments :)
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Unread postAuthor: jackssmirkingrevenge » Sun Nov 22, 2009 5:45 pm

Not bad for a first effort but agreed with the above suggestion that for smaller calibres, a smaller high pressure chamber would be much better in terms of performance Case in point ;)
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Unread postAuthor: POLAND_SPUD » Sun Nov 22, 2009 5:51 pm

it's all about the pressures you can generate... with a fridge compressor you could sacrifice chamber volume for pressure and still get better performance

so even a length of 1/2" 3/4" iron pipe would be ok or copper pipe if you are concerned with weight
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Unread postAuthor: julktyl » Sun Nov 22, 2009 7:01 pm

Ok, so I've been running some calculations...

The pen gun that jackssmirkingrevenge made has a chamber volume of approx .5 cubic inches without anything in it but with the stuff you have in it it would be less than that (assuming the length is about 10 in. and the inside diameter is about 1/4 in.)

The PVC chamber on the SML is about 6.1 cubic inches based on a length of 3 in. and an inside diameter of 1.61 in.

I thought about it for a bit and the answer was so simple, the gun itself is big enough to be the chamber, assuming the pressure rating is high enough, which I think it is.

So, with some modifications, here is the new version, minus the barrel.
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New SML
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Unread postAuthor: jmadden91 » Sun Nov 22, 2009 7:19 pm

Looks great, now grab yourself a Shock Pump and get 300psi into her :thumbleft:
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Unread postAuthor: Techie » Sun Nov 22, 2009 7:24 pm

no damage pics? video? and i dont think your going to be doing much with a chamber that small, but before coming t a conclusion, how much pressure can you generate?
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Unread postAuthor: roboman » Sun Nov 22, 2009 7:33 pm

Very nice! I've always liked minis...

<sarcasm>
It's a small arms launcher? Does that mean it launches other weapons? :roll:
</sarcasm>
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ilovetoblowthingsup wrote: The yellow/orange back fits super snugly, very nice in fact, but the head does not fit.
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Unread postAuthor: julktyl » Sun Nov 22, 2009 7:40 pm

jmadden91 wrote:Looks great, now grab yourself a Shock Pump and get 300psi into her


That's another thing I was wondering, maybe the quick connect isn't the way to go... I might put a schrader valve on instead. But suppose I didn't, would a regular air compressor be able to pump 300-400 psi into the quick connect?

Techie wrote:no damage pics? video? and i dont think your going to be doing much with a chamber that small, but before coming t a conclusion, how much pressure can you generate?


julktyl wrote:I have yet to test the SAL and will hopefully be able to tonight or tomorrow. As soon as I figure out if it will work I'll post demonstration video with damage. More pictures are soon to come as well.


According to the data collected from Burnt Latke's Chamber to Barrel Ratio Tests (granted, he uses spuds and not airsoft BBs), the optimal chamber volume for my barrel (~.2262 cubic in.) would be between ~.13572-.18096 cubic in. Currently, the volume of my chamber is ~.5 cubic in., which well exceeds that. The volume of jackssmirkingrevenge's pen gun chamber is less than .5 cubic in. and has been tested at 400 psi.

EDIT: roboman, maybe I should change the name haha. How does SL (Small Munitions Launcher) sound?
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Last edited by julktyl on Sun Nov 22, 2009 7:47 pm, edited 1 time in total.
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Unread postAuthor: roboman » Sun Nov 22, 2009 7:47 pm

julktyl wrote:But suppose I didn't, would a regular air compressor be able to pump 300-400 psi into the quick connect?


No. That is, I'm assuming you're talking about a normal shop air compressor. If you get a fridge compressor, that's a totally different story.
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ilovetoblowthingsup wrote: The yellow/orange back fits super snugly, very nice in fact, but the head does not fit.
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Unread postAuthor: jmadden91 » Sun Nov 22, 2009 7:48 pm

julktyl wrote:That's another thing I was wondering, maybe the quick connect isn't the way to go... I might put a schrader valve on instead. But suppose I didn't, would a regular air compressor be able to pump 300-400 psi into the quick connect?


A regular air compressor will get you about 100-130psi that sort of range. If you want to use the quick connect I suggest you get a fridge compressor hooked up. That will pump to around ~ 500psi and do so through a quick connect. Here is the thread on Fridge Compressor's

http://www.spudfiles.com/forums/my-compressor-300-psi-and-more-much-more-d-t11866.html

Edit: Beaten :roll:
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Unread postAuthor: julktyl » Sun Nov 22, 2009 7:56 pm

Ok so a schrader valve is definitely the way to go then for simplicity and cost. I'll look more into finding a shock pump, thanks for the links too.
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Unread postAuthor: Techie » Mon Nov 23, 2009 5:04 pm

julktyl wrote:
I have yet to test the SAL and will hopefully be able to tonight or tomorrow. As soon as I figure out if it will work I'll post demonstration video with damage. More pictures are soon to come as well.


My bad :oops:
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