Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 71 users online :: 5 registered, 0 hidden and 66 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

New pneumatic - would like some advice on build and GGDT

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
Sponsored 
  • Author
    Message

New pneumatic - would like some advice on build and GGDT

Unread postAuthor: Mercwear » Wed Aug 25, 2010 10:52 pm

Hello,
I have been reading the site for a while and am in the process of building my 2nd pneumatic cannon. I have been using GGDT to run some tests and want to make sure I am using the application correctly. The image below gives a brief overview of my build and a screenshot with what (I think) is a correct GGDT input and output.

Image

My primary concern is the size of my chamber, I think it’s too small but when I use GGDT to increase my chamber volume it only gives me a slight performance bump. I am going for distance when I shoot and my ammo will be potatos.

Any guidance you can give me on the build is appreciated.
Thanks
  • 0


Mercwear
Private
Private
 
Posts: 5
Joined: Tue Aug 24, 2010 3:44 pm
Reputation: 0

Unread postAuthor: MrCrowley » Wed Aug 25, 2010 11:16 pm

Sprinkler valve data should be (according to those at Spudtech):

Cv: 6 (you have it on efficiency, you need to change this back to 'Cv')
Seat Diameter: 1.1"
Piston Diameter: 1.8"
Piston Mass: 0.8oz
Vent diameter: 0.15" (0.2" if your blowgun is modified for extra flow).

Also, your projectile should also be 2" in diameter (same as your barrel), not sure why you only have it as 1.56". Even if you're using a sabot, put the diameter as 2".
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: Mercwear » Thu Aug 26, 2010 6:53 am

Thanks for the reply MrCrowley - what are your thoughts on the size of the pressure chamber?
  • 0


Mercwear
Private
Private
 
Posts: 5
Joined: Tue Aug 24, 2010 3:44 pm
Reputation: 0

Unread postAuthor: Gun Freak » Thu Aug 26, 2010 6:55 am

I say don't use steel on the tank. Use 1.5" pvc, it can take 150 psi.
  • 0

OG Anti-Hybrid
One man's trash is a true Spudder's treasure!
Golf Ball Cannon "Superna"M16 BBMGPengunHammer Valve Airsoft SniperHigh Pressure .22 Coax
Holy Shat!
User avatar
Gun Freak
Lieutenant General
Lieutenant General
 
Posts: 4969
Joined: Mon Jan 25, 2010 4:38 pm
Location: Florida
Country: United States (us)
Reputation: 11

Unread postAuthor: Mercwear » Thu Aug 26, 2010 8:55 am

Gun Freak wrote:I say don't use steel on the tank. Use 1.5" pvc, it can take 150 psi.


I like the safety of steel.. I will shoot this thing off around several people (some are kids) and I just cant compromise on safety. My first pnumatic was pvc and held up to 150 just fine but there is always that off chance that it could blow up (I had it wrapped in steel mesh and duct tape but that would only slow down the shards of PVC, not stop them).

I would love to hear your thoughts on chamber size given what I am going to use this gun for (distance of potato). If I need to increase the chamber size to 2' pipe (1 foot) I can do that.

Thanks for the reply gun freak!
  • 0


Mercwear
Private
Private
 
Posts: 5
Joined: Tue Aug 24, 2010 3:44 pm
Reputation: 0

Unread postAuthor: Gun Freak » Thu Aug 26, 2010 9:08 am

Well if your primary ammo is potatoes, don't use a 2" barrel. I think that is too big. Try a 1.5" barrel about 3 feet long ( or more, but I suggested shorter because you already have a short barrel in the design) with a spud cutter on the end. For the chamber I would suggest two feet of 2" PVC or similar (metal is you want). Just play around with the numbers in GGDT and see what the smallest chamber you can use with a good fps is.
  • 0

OG Anti-Hybrid
One man's trash is a true Spudder's treasure!
Golf Ball Cannon "Superna"M16 BBMGPengunHammer Valve Airsoft SniperHigh Pressure .22 Coax
Holy Shat!
User avatar
Gun Freak
Lieutenant General
Lieutenant General
 
Posts: 4969
Joined: Mon Jan 25, 2010 4:38 pm
Location: Florida
Country: United States (us)
Reputation: 11

Unread postAuthor: Technician1002 » Thu Aug 26, 2010 9:57 am

2 inch is OK of you use what they call "Bakers" in the US. They are large. They are the spuds used for baked spuds and french fries. This is why most fries are longer than your average spud.

They work great in a 2 inch barrel, are larger with more mass so they fly farther.

Regular spuds from the supermarket are too small for a 2 inch barrel.

In my location with lots of apples, I shoot many more apples than spuds. I use the free ones that have fallen off the trees.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Sponsored

Sponsor
 


Unread postAuthor: Mercwear » Fri Aug 27, 2010 8:23 am

MrCrowley wrote:Sprinkler valve data should be (according to those at Spudtech):

Cv: 6 (you have it on efficiency, you need to change this back to 'Cv')
Seat Diameter: 1.1"
Piston Diameter: 1.8"
Piston Mass: 0.8oz
Vent diameter: 0.15" (0.2" if your blowgun is modified for extra flow).


MrCowley,

Where did you get this info? I looked at spudtech but could not find any specifics on my valve.

Thanks
  • 0


Mercwear
Private
Private
 
Posts: 5
Joined: Tue Aug 24, 2010 3:44 pm
Reputation: 0

Unread postAuthor: Ragnarok » Fri Aug 27, 2010 10:00 am

Mercwear wrote:Where did you get this info? I looked at spudtech but could not find any specifics on my valve.

The old Spudtech forum. The current Spudtech site, no longer having a forum, is unlikely to include any of that kind of data.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: Technician1002 » Fri Aug 27, 2010 11:39 am

Some other common sprinkler valves are listed on the GGDT site. They list the specs for a 1 inch Orbit watermaster which is close to the rainbird.

http://thehalls-in-bfe.com/GGDT/
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: Mercwear » Fri Aug 27, 2010 2:00 pm

Thanks again for the replies.. I am going to stick with a 1.5 x 12in steel chamber for now and just up the PSI to around 150 to get 200+fps out of the gun =)
  • 0


Mercwear
Private
Private
 
Posts: 5
Joined: Tue Aug 24, 2010 3:44 pm
Reputation: 0

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'