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Author Topic: Vent Placement  (Read 579 times)

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Offline Farmer Dean

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Vent Placement
« on: March 14, 2007, 12:21:47 PM »
On my yet to arrive 1841 Six Pounder, I have a question about where to place the vent hole. It has a 3 1/2" bore. Using formulas from this Forum my maximum charge should be no more than 7oz.

If I start out test firing this cannon at half rate (3 or 4oz.) in that 3 1/2" bore how pancake thin does the charge become? More importantly is there a rule out thumb on how for from the back of the breach the vent hole should be placed? My guess is that it's pretty important the the fuse is into powder!   ;D
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Offline GGaskill

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Re: Vent Placement
« Reply #1 on: March 14, 2007, 12:26:02 PM »
You want to put the touch hole (vent) as far back as possible commensurate with actually entering the powder bag.  Experiments were conducted in the mid-19th century that showed that maximum velocity was achieved when the vent was at the rear of the charge and minimum velocity when at the front of the charge.
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GG
“If you're not a liberal at 20, you have no heart; if you're not a conservative at 40, you have no brain.”--Winston Churchill

Offline Artilleryman

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Re: Vent Placement
« Reply #2 on: March 14, 2007, 01:00:22 PM »
Don't forget to calculate in the diameter of the vent piece.
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Norm Gibson, 1st SC Vol., ACWSA

Offline powder2burn

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Re: Vent Placement
« Reply #3 on: March 14, 2007, 01:49:52 PM »
If I had that question I would ask the person or the company I was purchasing the tube from where they would recommend placement of the vent hole.  It would also be helpful if you would describe the make, model, manufacturer of the tube (cannon barrell)

FRED>>>>>>>>>>>>>>>>>>>>>>>>
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Offline Farmer Dean

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Re: Vent Placement
« Reply #4 on: March 14, 2007, 03:07:59 PM »
Thanks Fred, I'll do that. It's a Hern Model 1841 Six Pounder. 65" long, 3 1/2 bore. I thought for the same liability reasons that they do not sell a vented barrel, they might not even be able to make a recomendation. Just because they make them it doesn't necessarily mean that they know how to fire them. I was hoping to hear from someone with a similar size barrel. Not having ever wraped a charge before, I have no idea how big of a package you end up with.

So far I'm guessing that if you allow 1/4" for 6 plys of tin foil, and you want the vent as far to the rear of the barrel as possible, that would place the vent about 1/2" in from the breach plug.
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Offline powder2burn

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Re: Vent Placement
« Reply #5 on: March 14, 2007, 04:27:31 PM »
Herns mortars have a vent hole area marked out in the casting on where to drill the vent hole. Call and talk with Hern's and I bet you can glean a lot of info from them that they don't print.
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Offline Farmer Dean

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Re: Vent Placement
« Reply #6 on: March 14, 2007, 04:56:17 PM »
pb: you're right. I'll call them first - that would be the easiest way. Gez, if I did everything the easiest way the first time, I wouldn't have anything to do. Thanks for pointing me back in the right direction. Dean.
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