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 84 users online :: 5 registered, 0 hidden and 79 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

My first cannon. Looking for any tips for improvement.

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

My first cannon. Looking for any tips for improvement.

Unread postAuthor: mlz3000 » Sat Oct 23, 2010 5:41 pm

I build my first cannon last weekend, and I'm pretty happy with its performance, I was just anything I did that could be pretty easily improved upon for this cannon, or anything I could do better this time.



The barrel is 3' of 2.5" PVC (for firing tennis balls)

The chamber is 1' of 4" PVC with a shrader valve, pressure meter, and 125 PSI blow off valve tapped in.

The valve is a 1" sprinkler valve with a blow gun tapped in as the pilot valve.

I have two main concerns:

1) The barrel has greater volume than the chamber. I'm pretty sure that this is a problem, but I don't know if I should shorten the barrel, or lengthen the chamber. Because I pump the cannon by hand, I don't want to make the chamber too much bigger than it currently is.

2) I don't know what kind of pressure the tapped in fittings can handle. So far I have been taking it to 100PSI, do you think that is safe? Is there some sort of glue I should put on them to make it more safe?

Any other comments/ tips are more than welcome!
  • 0

Attachments
CAKE I.jpg
Sorry about the image quality, I took the pic with my phone.
User avatar
mlz3000
Corporal
Corporal
 
Posts: 69
Joined: Sat Oct 23, 2010 4:55 pm
Reputation: 0

Unread postAuthor: Gun Freak » Sat Oct 23, 2010 5:48 pm

Well, it looks like all your fittings are pressure rated. Good start.
Good valve also. Modded sprinklers can have good power, but with your barrel size, I think a larger porting valve would be way better. Maybe a 1.5" porting piston valve. I know you won't upgrade, just saying it would be better.
Barrel is only 3 feet, could be longer (5 or 6 feet).
Chamber should be bigger. Twice the size I'd say.
You tapped into a single layer. That is a big no-no. You should always use two layers.
You pretty much made the same mistakes most people make on their first. More research could have prevented this, but it is fine. At 100 psi, it is a little dangerous. I say keep it 80 and under (despite the bad performance).
Overall, it is not bad for a first. Slap a smaller barrel on and shoot some golf balls or something for fun. Maybe even smaller for better FPS.
  • 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: Lockednloaded » Sat Oct 23, 2010 6:02 pm

Good for a first, but that end cap cannot be pressure rated. Pressure rated end caps are domed, your rarely see flat surfaces on pressure tanks. a 1.5" SV would be a great power increaser, and I know a place where you could get one for cheap if you PM me about it.
  • 0

I love lamp
User avatar
Lockednloaded
Major General
Major General
 
Posts: 1558
Joined: Thu Sep 03, 2009 9:38 pm
Location: Texas, USA
Reputation: 0

Unread postAuthor: mlz3000 » Sat Oct 23, 2010 6:03 pm

Thanks!

Gun Freak wrote:You tapped into a single layer. That is a big no-no. You should always use two layers. "


What do you mean by that? Should I have tapped them in where the cap went over the pipe?

Is that the only reason I should keep it below 100PSI? I would be willing to replace the chamber with a 2x as big one to increase performance and so that I could tap in the fittings safely.

Gun Freak wrote:I think a larger porting valve would be way better. Maybe a 1.5" porting piston valve.


Would you mind linking me to instructions on how to build such a valve? I'm still trying to find my way around the site, and It's a bit overwhelming. :oops:
  • 0

User avatar
mlz3000
Corporal
Corporal
 
Posts: 69
Joined: Sat Oct 23, 2010 4:55 pm
Reputation: 0

Unread postAuthor: MrCrowley » Sat Oct 23, 2010 6:37 pm

What do you mean by that? Should I have tapped them in where the cap went over the pipe?

Yup, that's right. Though like said above, your end cap is not rated for pressure and should be replaced. Read this article:
http://www.spudfiles.com/spud_wiki/inde ... sure_rated

I would increase the barrel length before increasing the chamber. Your valve is restricting flow a lot, like mentioned above, a larger valve would help. Read this topic to learn about piston valves, though you are still starting out so you may want to pace yourself. Piston valves can be quite difficult the first time you make them.
  • 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: mlz3000 » Sun Oct 24, 2010 12:29 am

Oh, wow, I didn't realize that the cap was not pressure rated, thanks!

I guess I need to build a new chamber...

When I do, should I go ahead and make it larger? Is it not really necessary because of the flow of the valve?

With volume constant, is a longer, lower diameter chamber or shorter, higher diameter chamber better? Or does that not really make a difference?
  • 0

User avatar
mlz3000
Corporal
Corporal
 
Posts: 69
Joined: Sat Oct 23, 2010 4:55 pm
Reputation: 0

Unread postAuthor: Hubb » Sun Oct 24, 2010 6:42 am

When I make a pneumatic, I try to go for at least a 1:1 ratio (that is, the chamber volume and barrel volume are the same). This really isn't a set-in-stone rule, but it seems to work out.

As far as the chamber goes, I've not really noticed a difference either way. It does matter in a combustion, but the air flow through a pneumatic is a bit different. I'd say go with what you are comfortable with. If you keep it an inline version, it may be better suited to go with a short, fat chamber rather than a thin, long one (for comfort reasons).

As far as the valve goes, even though I am a fan of the sprinkler valve (you can check out the document I made in the Hubb Library, which is recommended), everyone is right. Sprinkler valves are excellent starter valves, but piston valves have much performance increase. I suggest learning as much as you can about the sprinkler valve before starting a piston valve. That way, when you do upgrade to a piston, you will already know a lot of the basics.

I do believe you will find this community rather friendly, and there is lot to be learned from here. Check out the SpudWiki and the search (advanced; not quick search). And welcome to Spudfiles.
  • 0

User avatar
Hubb
Major General
Major General
 
Posts: 2390
Joined: Mon May 28, 2007 8:39 am
Location: South Georgia
Reputation: 2

Sponsored

Sponsor
 


Unread postAuthor: Technician1002 » Sun Oct 24, 2010 9:31 am

When hand pumping a chamber doubling the chamber size does mean twice the effort to pump it up. There is a major advantage to a small chamber when hand pumping a cannon.

A 4 inch diameter chamber 1 foot long is much larger than my Marshmallow cannon which is less then 4 inch by about 7 inch. It does just fine with a 3 foot long tennis ball barrel.

My chamber will fit inside a 4 inch ABS barrel.

I was even able to get decent hang times with tennis balls with a 7 foot long tennis ball barrel. It is true it would fail to launch at lower pressure as there was not enough expansion to eject the ball.

For a hand pumped tennis ball launcher, a 1 foot long 4 inch chamber is fine. Larger is too much work to be fun anymore.

The largest cannon that is worth hand pumping is my ABS cannon. The larger steel tank cannon is too much of a workout to get decent pressure.

If you could possibly get a 1.5 inch sprinkler valve the improved flow will be worth the effort.

Sweet size for hand pumped tennis ball launcher.
Image
  • 0

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

Unread postAuthor: Hubb » Sun Oct 24, 2010 12:16 pm

That's not fair, Tech. You're using a QDV and not a sprinkler valve. :D
  • 0

User avatar
Hubb
Major General
Major General
 
Posts: 2390
Joined: Mon May 28, 2007 8:39 am
Location: South Georgia
Reputation: 2

Unread postAuthor: Technician1002 » Sun Oct 24, 2010 12:48 pm

A 1.5 inch sprinkler valve should closely match a 1 inch QDV.. It is why I recommended it.
  • 0

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

Unread postAuthor: mlz3000 » Sun Oct 24, 2010 2:40 pm

Wow, thanks for all the help! :)

Is a 1.5" sprinkler valve something I might find at Home Depot, or is it a harder to find item?

Also, for future reference, next time I make a post like this, should it go in this topic, or is the cannon showcase page more appropriate?
  • 0

User avatar
mlz3000
Corporal
Corporal
 
Posts: 69
Joined: Sat Oct 23, 2010 4:55 pm
Reputation: 0

Unread postAuthor: Gun Freak » Sun Oct 24, 2010 2:43 pm

mlz3000 wrote:Is a 1.5" sprinkler valve something I might find at Home Depot, or is it a harder to find item?

They aren't normally availible at Home Depot. Most of the time you find them online or you get lucky and find them in a store.

Also, for future reference, next time I make a post like this, should it go in this topic, or is the cannon showcase page more appropriate?

The showcase.
  • 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

Re: My first cannon. Looking for any tips for improvement.

Unread postAuthor: jackssmirkingrevenge » Sun Oct 24, 2010 10:27 pm

mlz3000 wrote:The barrel has greater volume than the chamber. I'm pretty sure that this is a problem, but I don't know if I should shorten the barrel, or lengthen the chamber. Because I pump the cannon by hand, I don't want to make the chamber too much bigger than it currently is.


Only by around 17%, which is acceptable for the pressures you're using, going with a longer barrel will give you better performance and a quieter shot for no extra pumping effort.

As to upgrading your valve, why not go straight for a 2"? Not too expensive and it will give you 178% the flow of a 1.5" ;)
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: mlz3000 » Sun Oct 24, 2010 11:28 pm

I'm thinking I'll just make do with the current valve until I have done enough research to feel comfortable building my own piston valve.

For when I build the CAKE II (It will be the same as the CAKE I except without those dangerous design errors :oops: ) If I keep the same valve, what length of 1.5" pipe would be a good barrel for launching golf balls? 7 ft gives me a ~ 1:1 ratio, would that be a good length?

Any clue what kind of range I would get out of that?
  • 0

User avatar
mlz3000
Corporal
Corporal
 
Posts: 69
Joined: Sat Oct 23, 2010 4:55 pm
Reputation: 0

Unread postAuthor: Technician1002 » Sun Oct 24, 2010 11:39 pm

Shhhh.. I wanted him to match my little launcher, not beat it.. :shock:

With your current valve and a golf ball barrel, you can model it in GGDT. Some of the common sprinkler valves are listed on the GGDT site with the valve values to plug in.

Look here for the data.
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

Next

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'