3" Coehorn Mortar with Powder Chamber - Graybeard Outdoors
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post #1 of 16 (permalink) Old 04-03-2019, 12:36 PM Thread Starter
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Default 3" Coehorn Mortar with Powder Chamber

Working with the Machine shop on a new liner option. Give me any input; hanging out on this forum piqued my interest and I sketched this up before spring break last.
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post #2 of 16 (permalink) Old 04-03-2019, 05:02 PM
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Jack,
I like it. What does it do to the price?

Ralph M. Reese
St. Augustine, FL
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post #3 of 16 (permalink) Old 04-03-2019, 05:48 PM Thread Starter
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"drawing" is out to the machine shop as we speak. I can't believe that it will be a large change from machining the concave breach plug for the standard 3" liners we run.

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post #4 of 16 (permalink) Old 04-03-2019, 08:25 PM
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Jack, the weather is going to cooperate this weekend and I plan on shooting my 3" with the concave bore for the first time. It'll take a bit more powder then your new design but hey, more powder means more smoke and thunder. Isn't this why we do this in the first place?

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post #5 of 16 (permalink) Old 04-04-2019, 01:42 AM
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If you increased the diameter of the stern part of the plug to be the same as the liner, it would simplify drilling/reaming of the bore. It would also get some support from the tube.

GG
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post #6 of 16 (permalink) Old 04-04-2019, 07:06 AM
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George it is the liner for a casting.
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post #7 of 16 (permalink) Old 04-05-2019, 03:20 AM
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I realize that. The bore of the casting has to be a close fit with the liner or the liner is carrying all the load. By making the plug OD the same as the liner OD, the hole in the casting can be a single diameter instead of stepped. I would leave a short section for the weld at liner ID but make the remaining part of the plug that is out of the bore liner the same diameter as the OD of the liner.


I can add a drawing if there is interest.

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post #8 of 16 (permalink) Old 04-05-2019, 07:19 AM
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Post a picture, George. Pictures are alsways good.

I didn't/ don't understand your comment about drilling and reaming as this liner is the core for a casting.

But thinking about what you are saying, I have to wonder if a straight liner exterior would resist warpage better than a stepped liner from the heat of the molten metal when it is poured around the liner.
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post #9 of 16 (permalink) Old 04-05-2019, 03:40 PM
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I think he means the barrel is cast around the liner, not drilled and inserted after casting.
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post #10 of 16 (permalink) Old 04-05-2019, 06:43 PM
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Quote:
Originally Posted by GGaskill View Post
If you increased the diameter of the stern part of the plug to be the same as the liner, it would simplify drilling/reaming of the bore. It would also get some support from the tube.
George has a great idea. Adding a machined shoulder to the breach plug. The shoulder would be in the place shown as “weld” in Jacks drawing. Now the breach has more support, better alignment and becomes the same diameter as the liner. Use a heat shrink fit and weld at the seam?

Edit. As I re-read earlier posts, George had a different thought at the liner to breach plug interface. Sorry for the confusion. If the liner and plug could be threaded, that would be perfect. Applaud Jack for adding a powder chamber to his mortars. Adds both strength and efficiency.

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