1/3 scale Coehorn project. - Graybeard Outdoors
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post #1 of 40 (permalink) Old 07-07-2019, 03:21 PM Thread Starter
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Default 1/3 scale Coehorn project.

Actually this is a them, as I'm building a pair. One to keep and one as a gift for a friend.

I'd never built a mortar before when I started my first golfball project, so I just looked at my piece of stock and said "It will be this big." Turns out it was seriously overbuilt, with a chamber that could almost put a GB into low earth orbit. But it's been a lot of fun.




Over the years and other mortar projects of varying calibers, I've come back around to the golfball. This time in a more compact package.








I've had this on the boards for awhile now (a long while), and I've had the steel blanks sawed for months. I didn't want to start a thread until I had actually done something.

A few days ago I went to the shop and turned and faced one end of each. Then went back this morning and bored and chambered the first tube. It will probably be next weekend before I can get back up there to bore the other one.






In the meantime I will start making handle parts and assembling my soldering fixture.

I bought 3/16" brass flat for the handles, the brass rod I already had.




I will be constructing a bed for mine, the other will be sent with all the instructions and measurements and he can take it from there.

.

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Last edited by Terry C.; 07-07-2019 at 03:41 PM.
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post #2 of 40 (permalink) Old 07-10-2019, 12:10 PM
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Nice work on your projects current and past. I admire your metal skills so I will follow this closely.

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post #3 of 40 (permalink) Old 07-10-2019, 12:35 PM
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Great looking project!

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post #4 of 40 (permalink) Old 07-13-2019, 04:36 PM Thread Starter
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Moving forward . . .




Ready to turn them around and work on the breech end.

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post #5 of 40 (permalink) Old 07-15-2019, 12:03 PM Thread Starter
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Time to start center punching brass (handle brackets) and aluminum (soldering fixture) for drilling . . .




My printer ran out of ink and of course Walmart was out of the one I needed. I ordered online, so that delayed this for a few days.

If push had come to shove I could have scribed this all out, but the printed labels are easier on the old eyes.

.

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Last edited by Terry C.; 07-15-2019 at 12:42 PM.
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post #6 of 40 (permalink) Old 07-15-2019, 12:41 PM Thread Starter
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Also used some heavier stock and printed my template for shaping the breech . . .



(There was a typo on the template, I edited it out of the pic. The original file has been corrected)

I don't often bare my soul, it's ugly and tends to frighten people.

Last edited by Terry C.; 07-16-2019 at 12:22 AM.
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post #7 of 40 (permalink) Old 07-15-2019, 09:33 PM Thread Starter
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Soldering fixture . . .





Mocked up with stacked brass washers (roughly the thickness of the brass flat) and a scrap piece of brass rod.


Basically a variation of the fixture I used on the poolball mortar, on a smaller scale. For size comparison, both bases were cut from the same 1/4" x 1-1/2" aluminum flat bar, the smaller one is about 1/4" shorter . . .



.

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Last edited by Terry C.; 07-17-2019 at 07:50 AM.
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post #8 of 40 (permalink) Old 07-16-2019, 04:43 PM Thread Starter
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Chopped up and ready to stack and shape, not closely since the sanding pad on my angle grinder would make quick work of the excess . . .




Uh, Houston we have a problem ... my angle grinder took a large and probably irreparable dump partway through the shaping.

I somewhat cleaned up what was close on the diamond hone but the radius around the 3/16" hole (which I was going to do last) is still pretty much untouched.

Stuck here until I can either repair the grinder (doubtful, fire and smoke from the front end is usually a death rattle) or get another one . . .


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post #9 of 40 (permalink) Old 07-16-2019, 05:16 PM
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Looks great!

Handi Rifles: 35 Whelen, 45-70 UH SS, 22-250 UV, 25-06 UH, 30-30, 7-08, 223, 308 Survivor
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post #10 of 40 (permalink) Old 07-17-2019, 03:10 PM Thread Starter
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Turned out the grinder as not as bad as I thought, wire rubbed through and shorted out against the armature. Probably my fault as I think I left it too slack when I had to repair the cord awhile back. I was more careful reassembling it this time.

Back on track.

Here is the soldering fixture disassembled for a final cleaning and deburring . . .




And reassembled next to the fixture I used for the poolball mortar . . .




And finally mocked up with a couple of the brass handle brackets . . .




Next step, bend some round stock.

Hope to get the breech profiled on at least one (hopefully both) of the mortars this weekend.

.

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