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 82 users online :: 2 registered, 0 hidden and 80 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

I need help with plans

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

I need help with plans

Unread postAuthor: Pilgor » Sat Feb 02, 2008 4:33 pm

My friend just built a dual chambered pneumatic spud cannon. It looked good so i was about to use his plans. but then his gun blow up. He was using pressure rated sch 40 pvc. does anyone here having any safe dual chambered pneumatic potato guns.
and do not ask to see the plans i have because i have deleted them and so has my friend.

thanks alot in advanced.
  • 0

User avatar
Pilgor
Corporal
Corporal
 
Posts: 67
Joined: Sat Feb 02, 2008 4:25 pm
Location: Timmins,Ontario
Reputation: 0

Unread postAuthor: bigbob12345 » Sat Feb 02, 2008 4:43 pm

Your friend was probably using sch40 pressure rated pipe but his fittings were dwv thats why it exploded. Did he use bell reducers?Because they are almost all the time dwv.Just use your friends design but use pressure rated fittings. It is sometimes hard to find pressure rated fittings above 2in so if you cant find them buy them from mcmaster http://www.mcmaster.com/
  • 0

User avatar
bigbob12345
Major General
Major General
 
Posts: 1516
Joined: Sat Dec 01, 2007 9:13 am
Location: Mercer Island,Washington
Reputation: 0

Unread postAuthor: MrCrowley » Sat Feb 02, 2008 4:47 pm

Just a warning, Sch 40 doesn't mean it's pressure rated. It's a thickness rating, not a pressure rating.

What you need to look for is 'NSF-PW' on the pipe or fittings, which is always pressure rated.
  • 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: schmanman » Sat Feb 02, 2008 5:01 pm

MrCrowley wrote:Just a warning, Sch 40 doesn't mean it's pressure rated. It's a thickness rating, not a pressure rating.

What you need to look for is 'NSF-PW' on the pipe or fittings, which is always pressure rated.


I love it how crowley knows more about our plumbing system than most americans do.

I find it humorous. :P
  • 0

Last edited by schmanman on Sat Feb 02, 2008 5:10 pm, edited 1 time in total.
Persistence is a measure of faith in yourself
User avatar
schmanman
Major General
Major General
 
Posts: 1685
Joined: Sat Mar 25, 2006 12:28 pm
Location: Michigan,U.S.A
Country: United States (us)
Reputation: 0

Unread postAuthor: hi » Sat Feb 02, 2008 5:06 pm

either that or you over pressurized it. just because 2'' pipe is rated for 280 psi doesnt mean you can take it to 280 psi. in fact its not safe to do much more that 150 psi in my opinion. it could also be that he had faulty weld joints, or maybe the pipe was defective... it could be anything. if you do it right then that sort of thing wont happen.
  • 0

"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
User avatar
hi
Major General
Major General
 
Posts: 1619
Joined: Thu Feb 01, 2007 9:28 pm
Reputation: 0

Unread postAuthor: BrianMigs » Sat Feb 02, 2008 5:10 pm

what does a bell reducer look like? and how can some people on here tell if certain parts are dwv, especially if its all ready painted over?
  • 0


BrianMigs
Specialist
Specialist
 
Posts: 42
Joined: Sat Jan 26, 2008 1:23 pm
Reputation: 0

Unread postAuthor: MrCrowley » Sat Feb 02, 2008 5:17 pm

schmanman wrote:
MrCrowley wrote:Just a warning, Sch 40 doesn't mean it's pressure rated. It's a thickness rating, not a pressure rating.

What you need to look for is 'NSF-PW' on the pipe or fittings, which is always pressure rated.


I love it how crowley knows more about our plumbing system than most americans do.

I find it humorous. :P


I get it from you guys, so you better be right :)

'Spose it's like a language, and you just pick it up as you go.

And it's very handy if you speak the native language of the country you reside in, if you know what I mean.


Some guy at a hardware store yesterday was trying to sell me this crappy car compressor, he said he used it on forklift tyres, which are (according to him) very high pressure.

I ask how high it pumps, (while catching a glimpse of '250PSI' written on the box) and he said, 'oh about 300BAR'.

I just started laughing and asked if he knew his BAR and PSI, he said he did and kept saying forklift tyres are very high pressure. Then I told him 300BAR is about 4500psi, which you need hydraulic fittings for and i'd like to see a plastic pump get 1/10th that.

It still had no effect on him, he must not realise how high of a pressure 4500psi is, and the box of the pump had '250PSI' written about 10x all over it.
  • 0

Last edited by MrCrowley on Sat Feb 02, 2008 5:27 pm, edited 2 times in total.
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

Sponsored

Sponsor
 


Unread postAuthor: schmanman » Sat Feb 02, 2008 5:17 pm

from the structure of the part. the sockets are not as deep, the reducers are entirely different, and the walls of said part are much thinner.
  • 0

Persistence is a measure of faith in yourself
User avatar
schmanman
Major General
Major General
 
Posts: 1685
Joined: Sat Mar 25, 2006 12:28 pm
Location: Michigan,U.S.A
Country: United States (us)
Reputation: 0

Unread postAuthor: pizlo » Sat Feb 02, 2008 5:23 pm

To be safe you could spend a bit more and go metal. I don't think anyone here has ever seed a metal spud gun explode.
  • 0

User avatar
pizlo
Brigadier General
Brigadier General
 
Posts: 783
Joined: Fri Dec 22, 2006 7:27 pm
Reputation: 0

Unread postAuthor: hi » Sat Feb 02, 2008 5:23 pm

you can tell because DWV parts have their own shape that pressure rated parts do not come in, and vis versa.

also, dont put a lot of stress or strain on the fittings because fittings are usually the weakest link in a cannon, even if they are pressure rated, so putting stress on them makes it that much more likely to fail.
  • 0

"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
User avatar
hi
Major General
Major General
 
Posts: 1619
Joined: Thu Feb 01, 2007 9:28 pm
Reputation: 0

Unread postAuthor: MrCrowley » Sat Feb 02, 2008 5:26 pm

BrianMigs wrote:what does a bell reducer look like? and how can some people on here tell if certain parts are dwv, especially if its all ready painted over?


This is a bell reducer:
Image

If a part is DWV, it should only say DWV and maybe Sch 40 on the fitting/pipe.

On fittings the writing is usually raised and can be read once painted over, with pipe, if you have enough layers of paint you probably can't read it.

Don't Worry about identifying DWV pipe and fittings, more pressure rated fittings.

To find out if a fitting is pressure rated, it should have 'NSF-PW' and it may also have Sch 40 (or 80,120 etc) on it. IIRC American fittings don't have a pressure rating on them, but if they have NSF-PW, you're okay, it will be rated.

For pipe, it should have 'NSF-PW Sch 40 (or 80,120, etc) XXXPSI @73F'

XXXPSI, is the pressure rating, it changes depending on the Schedule rating and the diameter of the pipe. The pipe may have a different temperature rating, but the most common say '@73F'.

The pipe may also have 'DWV" written on it, as long as the pipe has a pressure rating, e.g '300PSI @73F' you're okay.

If it doesn't have 'NSF-PW' or pressure rating, chances are it's DWV.

Edit:

This is a PRESSURE RATED PVC 90* bend:
Image

This is a DWV PVC 90* bend, non-pressure rated:
Image

As you can see, the difference is very obvious.

You can get fittings that look DWV, but I doubt you will find them at Home Depot or Lowes, usually they're only found online.
  • 0

Last edited by MrCrowley on Sat Feb 02, 2008 5:29 pm, edited 1 time in total.
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: pizlo » Sat Feb 02, 2008 5:29 pm

MrCrowley wrote:
BrianMigs wrote:what does a bell reducer look like? and how can some people on here tell if certain parts are dwv, especially if its all ready painted over?


This is a bell reducer:
Image

If a part is DWV, it should only say DWV and maybe Sch 40 on the fitting/pipe.

On fittings the writing is usually raised and can be read once painted over, with pipe, if you have enough layers of paint you probably can't read it.

Don't Worry about identifying DWV pipe and fittings, more pressure rated fittings.

To find out if a fitting is pressure rated, it should have 'NSF-PW' and it may also have Sch 40 (or 80,120 etc) on it. IIRC American fittings don't have a pressure rating on them, but if they have NSF-PW, you're okay, it will be rated.

For pipe, it should have 'NSF-PW Sch 40 (or 80,120, etc) XXXPSI @73F'

XXXPSI, is the pressure rating, it changes depending on the Schedule rating and the diameter of the pipe. The pipe may have a different temperature rating, but the most common say '@73F'.

The pipe may also have 'DWV" written on it, as long as the pipe has a pressure rating, e.g '300PSI @73F' you're okay.

If it doesn't have 'NSF-PW' or pressure rating, chances are it's DWV.


This man speaks the truth. we should compile all of this and everything else he has ever said into a "bible"and make newbs read it.
  • 0

User avatar
pizlo
Brigadier General
Brigadier General
 
Posts: 783
Joined: Fri Dec 22, 2006 7:27 pm
Reputation: 0

Unread postAuthor: BrianMigs » Sat Feb 02, 2008 5:30 pm

Hey whaddya know, I have a 3" to 1" bell reducer on my cannon, crap. LOL

I have taken it up to 70PSI multiplt times, do I have a ticking time bomb?

I am going to go check all my fittings on my gun, they are all sch40 though, that I am sure of. Cheers
  • 0


BrianMigs
Specialist
Specialist
 
Posts: 42
Joined: Sat Jan 26, 2008 1:23 pm
Reputation: 0

Unread postAuthor: MrCrowley » Sat Feb 02, 2008 5:34 pm

BrianMigs wrote:I am going to go check all my fittings on my gun, they are all sch40 though, that I am sure of. Cheers


Still doesn't matter, what you need is the 'NSF-PW' on the fittings and 'NSF-PW' and/or a pressure rating in PSI on the pipe.

Probably not a ticking time bomb, but I wouldn't trust it personally, you never know when it could blow.
  • 0

Last edited by MrCrowley on Sat Feb 02, 2008 5:37 pm, edited 1 time in total.
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: bigbob12345 » Sat Feb 02, 2008 5:35 pm

You dont really have a ticking time bomb but try not to use it above 60psi even then it is dangerous I would recomend sawing off the bell reducer and replacing it with a bushing.
  • 0

User avatar
bigbob12345
Major General
Major General
 
Posts: 1516
Joined: Sat Dec 01, 2007 9:13 am
Location: Mercer Island,Washington
Reputation: 0

Next

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Yahoo [Bot]

Reputation System ©'