Author Topic: Group buy-group pour, bronze 24 PDR Coehorn golf ball mortar (Read 28236 times)

RocklockI · « **Reply #180 on:** October 26, 2011, 06:33:02 AM »

CW ,GOW ,
The word investment means 'surrounded ,protected' Just like a banking investment .

The wax positive is invested with either a powdered type like plaster of Parris OR like the founderies that use a shell investment is is made up of a serries of dipping in very thin slip to get all detail.
Then sucsecive coats in ever thickening investment ,till it is ready for the burn out .
Then the bronze is poured in .

Gary

btw the pics are at a bit of an angle as they look abit pointed ,but they are just right .

RocklockI · « **Reply #181 on:** October 26, 2011, 08:52:05 AM »

Dave ,you are correct if this works then they will be easier to make the next one.

That is the point ,there will be no mold ,as I decided I wasn't going to try a whole new aspect of learning and dealing with pro mold makers and their ways ....

The bronze art guys are abit high strung....unlike myself of course !

Plus no mold parting lines to clean up b4 casting . Cleaner all the way around .

So each one will be hand turned on the lathe .

Gary

GGaskill · « **Reply #182 on:** October 26, 2011, 09:55:46 AM »

So each one will be hand turned on the lathe.

Sounds like it is time for the CNC lathe.

RocklockI · « **Reply #183 on:** October 26, 2011, 06:42:29 PM »

RocklockI · « **Reply #184 on:** October 29, 2011, 12:42:04 PM »

Yesterdays work went well . Here #2

Bore

Gary

GGaskill · « **Reply #185 on:** October 29, 2011, 12:59:00 PM »

Are we going to add rimbases?

RocklockI · « **Reply #186 on:** October 29, 2011, 01:40:09 PM »

Yes and they were added today .
Gary

GGaskill · « **Reply #187 on:** October 29, 2011, 02:30:34 PM »

Great.

RocklockI · « **Reply #188 on:** November 30, 2011, 11:50:16 AM »

Hello all I got THE call today that the mortar was ready ! It looks real good are here are first photos .

I'll clean her up abit and get her off to Douglas .

The foundery says they think they can cast these flaw free .

I will order some more wax and start making some and we'll see how it goes . No firm price yet as it isn't done yet .
Gary

GGaskill · « **Reply #189 on:** November 30, 2011, 12:03:22 PM »

Did they check the bore with a golf ball?

Spuddy · « **Reply #190 on:** November 30, 2011, 12:41:13 PM »

Ahhh Rocklock is back. Looking good Gary.

flagman1776 · « **Reply #191 on:** November 30, 2011, 12:44:34 PM »

Looking very good.
Thankyou for all your efforts & keeping us posted.

Cannoneer · « **Reply #192 on:** November 30, 2011, 02:34:08 PM »

It looks fine, Rocklock. Were the bore and chamber cast around a core on this one?

RocklockI · « **Reply #193 on:** November 30, 2011, 03:57:44 PM »

Thanks , yes Geroge it is Golf ball certified .

Tim ,I've been around but have had some other hobbies that I have been pursuing .

Flagman you are welcome !

Cannoneer the bore and chamber where cast in place . More pics tomorrow IF I can get to Seacoast . Big snow is predicted ..... But you know how they lie !

Gary

GGaskill · « **Reply #194 on:** November 30, 2011, 04:45:42 PM »

Were the bore and chamber cast around a core on this one?

Not a core in the sand casting style, but the investment was inside the pattern and formed the cavity. The wax pattern gets melted out of the investment, which is fired hard to make the mould; then the liquid metal is poured into the cavity where the wax was.

Mike H. · « **Reply #195 on:** November 30, 2011, 09:30:59 PM »

That looks real nice. Do you have a shot down the bore with it well lit?

Cannoneer · « **Reply #196 on:** November 30, 2011, 10:10:59 PM »

You're right GG, for some reason I was thinking about sand casting, probably because of the other current 'casting' thread on the TN foundry.

What I was really curious about is how the bore and chamber turned out with this foundry, the first place didn't do too well. Will any work need to be done on it, or is the bore/chamber pretty much good to go right from the foundry?

GGaskill · « **Reply #197 on:** December 01, 2011, 10:56:37 AM »

I think it is the same foundry, just a little more careful in cleaning the casting this time. And a less complicated pattern, too.

flagman1776 · « **Reply #198 on:** December 01, 2011, 11:06:15 AM »

I believe reply #119 indicates a move to a second foundry. If there's been something since, I'm not seeing it posted.

RocklockI · « **Reply #199 on:** December 01, 2011, 01:35:48 PM »

This is the new foundery close to home . The first one was from Cody it was battered but is 'usable' it was the test piece .

I switched to the foundery in Loveland as I had worked with them in the past . They had cracked investment upon burn out so it was lost wax of the bad kind .
The chamber on this one needs boring out as it has a layer of bronze (at least) plugging it .

The foundery is learning . Hopfully plugged chambers will an not be systematic

The bore is fine . We had a masive snow storm last night and today (maybe 4 inches

)

I'll get to Seacoast and finish it up tomorrow .

Gary

seacoastartillery · « **Reply #200 on:** December 01, 2011, 03:27:16 PM »

Hey Gary, without even looking at it, I am willing to bet you that the unconventional shape of the chamber (i.e., Cylindrical) was the problem here. Think about it. Looking at reply #184, you can see how small the investment entry hole is. If you decide to improve this condition, a simple change in the shape of your wax drilling, spade drill to a Gomer Chamber shape would allow easier entry for the investment material, because a cone shape with the large end up would facilitate it. See the line drawings below for a clear comparison of the two styles of chamber.

I'm speculating here, but I would almost bet that you will find solid bronze below the point of intersection between the Ball Seat and the Chamber Mouth. This means that there was an air bubble below that point, when there should have been solid investment material.

Tracy

The cylindrical shape you have. These section drawings are from Gibbon's Artillery Manual. We bought ours in 1973 and it's a great addition to any artilleryman's library.

The traditional Gomer shape, (conical) which the original Coehorn and many other mortars had for easier loading and fewer cracked and disintegrated shells.

RocklockI · « **Reply #201 on:** December 01, 2011, 05:21:39 PM »

That would probably help ,it might be why they were invented .

Double D · « **Reply #202 on:** December 01, 2011, 05:30:35 PM »

It also is the type of this mortar had. Didn't my drawing have this type chamber?

Cannoneer · « **Reply #203 on:** December 02, 2011, 06:29:08 AM »

The original U.S. 24-pdr Coehorn mortars had 'Gomer' chambers.

Here's one of the drawings that DD previously posted.

Drawing posted by GGaskill some time ago.

seacoastartillery · « **Reply #204 on:** December 02, 2011, 08:42:59 AM »

Boy oh boy, I think you are going to love it Double D. It's really nice looking and the finish is just about perfect! Mr bronze and Mike are discussing how to set it up for perfect chamber drilling right now. Oh my, sounds like it's time to leave the shop. Very loud discussions are occurring now. EEEEK. I hear two air nozzles shooting end mill tubes now. I guess who ever has fewer welts on his head wins the argument! Don't worry DD, when they actually start running the mill, they will be in agreement.

Well maybe?

We will update after the machining is complete.

Tracy

Double D · « **Reply #205 on:** December 02, 2011, 09:24:11 AM »

Quote from: RocklockI on November 30, 2011, 11:50:16 AM

Hello all I got THE call today that the mortar was ready ! It looks real good are here are first photos .

I'll clean her up abit and get her off to Douglas .

The foundery says they think they can cast these flaw free .

I will order some more wax and start making some and we'll see how it goes . No firm price yet as it isn't done yet .
Gary

I missed this....it's coming to me. Kool! For some reason, I didn't realize that. I thought this was Gary working the project for everyone. I thought mine was history when the investment broke at Cody!!!

Now I am excited...thanks Gary!!!

Cat Whisperer · « **Reply #206 on:** December 02, 2011, 01:13:43 PM »

How about a SWAG estimate guess on price?

50 cents
100 $
1000$

RocklockI · « **Reply #207 on:** December 02, 2011, 01:34:04 PM »

Wow I acually made one !

Doug has insisted on a .178" vent so he can use the straw quills .
Here are both sides

Down the muzzle shot ,the bronze blockage was solid ,

Gary

GGaskill · « **Reply #208 on:** December 02, 2011, 01:52:49 PM »

Down the muzzle shot; the bronze blockage was solid.

Gives you an excuse to drill with a ball nose end mill.

Double D · « **Reply #209 on:** December 02, 2011, 02:33:20 PM »

Of course .178 diameter. Standard over the counter green cannon fuse is 1/8. Quills are 4mm. Standard fare and their no reason for smaller, none.

Poll

I would buy...

Author Topic: Group buy-group pour, bronze 24 PDR Coehorn golf ball mortar (Read 28236 times)