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

In total there are 78 users online :: 3 registered, 0 hidden and 75 guests

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

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

The Team
Global Moderators
global_moderators.png CS

Barlow's formula

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
  • Author

Barlow's formula

Unread postAuthor: DYI » Fri Apr 25, 2008 6:35 pm

Just a quick question, but I believe I'm doing something wrong here.

Using Barlow's formula, I ended up with a burst pressure of ~4300psig for a 4" Schedule XXS pipe made of plumbing grade steel. As far as I know, that's closer to the rated pressure of 4" Schedule XXS than to the burst pressure.

Can someone else who knows what they're doing try this and see what answer they come up with?
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
Lieutenant General
Lieutenant General
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: clide » Fri Apr 25, 2008 7:22 pm

I don't really see much that could go wrong with that equation. What value did you use for material strength? In order to get ~4300 psi bursting pressure for 4" XXS I need to use a material strength of around 10000 psi, which is pretty darn low for steel.
  • 0

Last edited by clide on Fri Apr 25, 2008 7:26 pm, edited 1 time in total.
<a href="http://gbcannon.com" target="_blank"><img src="http://gbcannon.com/pics/misc/pixel.png" border="0"></a>latest update - debut of the cardapult

Donating Member
Donating Member
Posts: 785
Joined: Sun Mar 06, 2005 3:06 am
Location: Oklahoma, USA
Reputation: 0

Unread postAuthor: pat123 » Fri Apr 25, 2008 7:24 pm


X = laminate wall thickness required (in)
P = operating pressure (psi)
D = inside diameter of pipe (in)
γ = design stress (psi)

Is this the one you used?
  • 0

User avatar
Posts: 514
Joined: Sat Dec 23, 2006 10:08 pm
Location: S.C.
Reputation: 0

Unread postAuthor: Larda » Fri Apr 25, 2008 7:58 pm

If i'm not wrong a 100mm OD (4") pipe with 5mm (0,2") thick walls made of S355JR with tensile strength of 600N/mm2 (87000psi) will have a burst pressure of 600bar (8700psi)
  • 0

Push to test... Release to detonate.
User avatar
Donating Member
Donating Member
Posts: 119
Joined: Wed Jul 18, 2007 7:52 am
Location: Sweden
Reputation: 0

Unread postAuthor: SpudFarm » Sat Apr 26, 2008 8:29 am

Larda got it to the line..

BTW is that the pipe you was going to use for my hybrid?
  • 0

"Made in France"
- A spud gun insurance.
User avatar
Donating Member
Donating Member
Posts: 2563
Joined: Sat Nov 04, 2006 9:39 am
Location: Norway Trondheim area
Reputation: 0

Unread postAuthor: cdheller » Sat Apr 26, 2008 1:49 pm

I'm not coming up with any of the above answers .

using online calculator at

http://www.engineersedge.com/calculator ... t_calc.htm

Engineers Edge Design & Engineering Resources
OD (in) 4.50 (in)
Wall (in) .674 (in)
Material Strength 35000 (psi)
Safety Factor (working) 2 See Above

Calculated Working Pressure 7500
Calculated Bursting/Yield Pressure 15000

that was far enough of everyone else's numbers I looked up pipe charts to see what the #*&@.

using published charts at
http://www.engineeringtoolbox.com/steel ... -d_43.html
answer is about the same

Double Extra Strong Wrought Steel Pipes - XXS
Pipe Dimension
(inches) Double Extra Strong - XXS
Bursting Pressure
(psi) Working Pressure
1/2 28000 3500
3/4 23460 2930
1 21780 2720
1 1/4 18400 2300
1 1/2 16840 2110
2 14680 1840
2 1/2 15355 1920
3 13710 1710
3 1/2 15900 1990
4 14965 1870
5 13475 1690

I may be ignorant of what thickness you have .
the closest sch to X.X.strong pipe is sch.160, but not same.
  • 0

User avatar
Donating Member
Donating Member
Posts: 126
Joined: Wed Oct 05, 2005 5:30 pm
Location: Austin Texas
Reputation: 0

Return to Construction Materials/Ammo Discussion

Who is online

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

Reputation System ©'