What kind of pressure are we dealing with?

Bogie · January 28, 2008, 12:20 PM

I'm getting ready to craft a run of black powder golfball mortars. Just wondering how thick I need to make the walls...

mykeal · January 28, 2008, 02:38 PM

Kind of depends on the material you're planning to use.

Bogie · January 28, 2008, 02:45 PM

Well, that sorta depends on the kind of pressure that we're gonna be dealing with, doesn't it?

Hawg · January 28, 2008, 06:27 PM

The breech should have a wall thickness of at least the bore diameter which in your case would be about 1.75 inch. Drawn Over Mandrel (DOM) seamless steel is the usual choice. The breech plug should be threaded in place, no welding. The plug should extend at least the bore diameter into the bore and more is better.

Bogie · January 29, 2008, 12:28 PM

So it's really that much pressure? Is it a fast spike, or what does the curve look like?

Hawg · January 29, 2008, 08:27 PM

I don't have a graph I can show you, maybe somebody else does. BP is an explosive not a propellant so it would be IMHO a sharp spike. The recommended charge for a golf ball mortar or cannon is 40 - 60 grs.

Bogie · January 30, 2008, 08:31 PM

I checked a local place. They don't carry DOM over about 0.625, but he's looking into stuff for me.

Hawg · January 30, 2008, 10:54 PM

You might go to a scrapyard and find a piece of heavy shaft like a cylinder ram and have it bored.

Bogie · January 30, 2008, 10:58 PM

Oh we can bore it... (access to full machine shop).

My machinist bud's a little busy, so I'm trying to source the pieces to make a few of these little toys...

FORE!

W. C. Quantrill · February 12, 2008, 02:34 PM

Hey Mississippi---

You used an axle out from under a box car the last time didnt you?

Hawg · February 12, 2008, 03:04 PM

Quote:

Hey Mississippi---

You used an axle out from under a box car the last time didnt you?

Actually no, those are cast.

W. C. Quantrill · February 12, 2008, 03:50 PM

Hawg · February 12, 2008, 08:16 PM

W.C. Quantrill. Good one. You had me goin.

W. C. Quantrill · February 18, 2008, 10:07 PM

Chamber pressures in the Springfield .45-70 runs 24,000 to 28,000. Chamber pressure in the .45 Colt ran around 12,000 to 15,000.

70 grains under a golfball aint gonna get that wicked. I have a 1-1/2" cannon that I shoot 2 ounces in. It shoots a 2# ball. I suspect that it is getting some measureable pressure. It will poke a hole thru a car body at a quarter of a mile. Your golf ball will not create enough resistance to build that much pressure.

You would be wise to begin with some high pressure seamless tubing. It is very common in oil field and gas field operations. Then, build around it. The oil field tubing is pressure tested to 10,000 psi. It is often referred to as upset tubing. It also telescope fits as it has a 1/4" wall thickness. 1-1/2" slip fits in 2" fits in 2-1/2" which will press fit in 3". You build strength fast with it.

Golf balls are strictly regulated to be exactly 1.68" in diameter, and 1.62 ounces in weight. If you started with 1.5" upset tubing, it would be necessary to bore or hone it about ten thousandths to get the ball to go in. (0.010 of thickness off the inside all the way around creates 0.020 increase in diameter.)

January 28, 2008, 12:20 PM	#1
Bogie Senior Member Join Date: June 5, 2000 Location: Job hunting on the road... Posts: 3,827	What kind of pressure are we dealing with? I'm getting ready to craft a run of black powder golfball mortars. Just wondering how thick I need to make the walls... __________________ Job hunting, but helping a friend out at www.vikingmachineusa.com - and learning the finer aspects of becoming a precision machinist. And making the world's greatest bottle openers!

January 28, 2008, 02:45 PM	#3
Bogie Senior Member Join Date: June 5, 2000 Location: Job hunting on the road... Posts: 3,827	Well, that sorta depends on the kind of pressure that we're gonna be dealing with, doesn't it? __________________ Job hunting, but helping a friend out at www.vikingmachineusa.com - and learning the finer aspects of becoming a precision machinist. And making the world's greatest bottle openers!

January 29, 2008, 12:28 PM	#5
Bogie Senior Member Join Date: June 5, 2000 Location: Job hunting on the road... Posts: 3,827	So it's really that much pressure? Is it a fast spike, or what does the curve look like? __________________ Job hunting, but helping a friend out at www.vikingmachineusa.com - and learning the finer aspects of becoming a precision machinist. And making the world's greatest bottle openers!

January 30, 2008, 08:31 PM	#7
Bogie Senior Member Join Date: June 5, 2000 Location: Job hunting on the road... Posts: 3,827	I checked a local place. They don't carry DOM over about 0.625, but he's looking into stuff for me. __________________ Job hunting, but helping a friend out at www.vikingmachineusa.com - and learning the finer aspects of becoming a precision machinist. And making the world's greatest bottle openers!

January 30, 2008, 10:58 PM	#9
Bogie Senior Member Join Date: June 5, 2000 Location: Job hunting on the road... Posts: 3,827	Oh we can bore it... (access to full machine shop). My machinist bud's a little busy, so I'm trying to source the pieces to make a few of these little toys... FORE! __________________ Job hunting, but helping a friend out at www.vikingmachineusa.com - and learning the finer aspects of becoming a precision machinist. And making the world's greatest bottle openers!

January 28, 2008, 02:38 PM	#2
mykeal Senior Member Join Date: October 8, 2006 Location: Northern Michigan Posts: 2,772	Kind of depends on the material you're planning to use.

January 28, 2008, 06:27 PM	#4
Hawg Senior Member Join Date: September 8, 2007 Location: Mississippi Posts: 16,188	The breech should have a wall thickness of at least the bore diameter which in your case would be about 1.75 inch. Drawn Over Mandrel (DOM) seamless steel is the usual choice. The breech plug should be threaded in place, no welding. The plug should extend at least the bore diameter into the bore and more is better.

January 29, 2008, 08:27 PM	#6
Hawg Senior Member Join Date: September 8, 2007 Location: Mississippi Posts: 16,188	I don't have a graph I can show you, maybe somebody else does. BP is an explosive not a propellant so it would be IMHO a sharp spike. The recommended charge for a golf ball mortar or cannon is 40 - 60 grs.

January 30, 2008, 10:54 PM	#8
Hawg Senior Member Join Date: September 8, 2007 Location: Mississippi Posts: 16,188	You might go to a scrapyard and find a piece of heavy shaft like a cylinder ram and have it bored.

February 12, 2008, 02:34 PM	#10
W. C. Quantrill Senior Member Join Date: February 11, 2008 Location: No Man's Land Posts: 354	Hey Mississippi--- You used an axle out from under a box car the last time didnt you? __________________ NRA Life Whittington Center Life

February 12, 2008, 03:50 PM	#12
W. C. Quantrill Senior Member Join Date: February 11, 2008 Location: No Man's Land Posts: 354	__________________ NRA Life Whittington Center Life

February 12, 2008, 08:16 PM	#13
Hawg Senior Member Join Date: September 8, 2007 Location: Mississippi Posts: 16,188	W.C. Quantrill. Good one. You had me goin.

February 18, 2008, 10:07 PM	#14
W. C. Quantrill Senior Member Join Date: February 11, 2008 Location: No Man's Land Posts: 354	Chamber pressures in the Springfield .45-70 runs 24,000 to 28,000. Chamber pressure in the .45 Colt ran around 12,000 to 15,000. 70 grains under a golfball aint gonna get that wicked. I have a 1-1/2" cannon that I shoot 2 ounces in. It shoots a 2# ball. I suspect that it is getting some measureable pressure. It will poke a hole thru a car body at a quarter of a mile. Your golf ball will not create enough resistance to build that much pressure. You would be wise to begin with some high pressure seamless tubing. It is very common in oil field and gas field operations. Then, build around it. The oil field tubing is pressure tested to 10,000 psi. It is often referred to as upset tubing. It also telescope fits as it has a 1/4" wall thickness. 1-1/2" slip fits in 2" fits in 2-1/2" which will press fit in 3". You build strength fast with it. Golf balls are strictly regulated to be exactly 1.68" in diameter, and 1.62 ounces in weight. If you started with 1.5" upset tubing, it would be necessary to bore or hone it about ten thousandths to get the ball to go in. (0.010 of thickness off the inside all the way around creates 0.020 increase in diameter.) __________________ NRA Life Whittington Center Life

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