Author Topic: Building a Bronze Rodman Gun (Read 2043 times)

shooter2 · « **on:** July 13, 2011, 01:13:05 AM »

The original idea was to make a Bronze Cannon at about 1/10 scale. I had been introduced to a retired Foundryman who made paper weights like small Brass anvils etc. He was happy to make something a bit bigger and a bit different. He needed Brass and I had lots (10 gallon Bucket of cartridge brass saved over the years) and he could provide Naval Bronze for the cannon. He needed a pattern, so I had a woodworking friend make a wood pattern 5% oversize based on the drawing of the 10 inch Rodman Gun in "The Big Guns". The estimate was the finished casting would weigh about 11 kilograms (25 pounds).

The first photo is of the Foundryman preparing the sand around the wood pattern.

The next photos are of the pattern in the mold and the molding box ready for the bronze.

shooter2 · « **Reply #1 on:** July 13, 2011, 01:23:07 AM »

The smelting of the Bronze and the pour were something special, he had bought a new crucible especially for the pour and was very enthusiastic about the project. I was just happy to be getting a free casting.

shooter2 · « **Reply #2 on:** July 13, 2011, 01:37:02 AM »

After about 24 hours of cooling I had a casting covered in molten sand. I had not expected this, I imagined a semi clean almost finished item. Then the hard work started, getting the sand off and shaping the casting. The sand had moved during the pour and the casting was slightly flat instead of perfectly round. The following photos are of the steps to get the casting up to standard.

shooter2 · « **Reply #3 on:** July 13, 2011, 01:39:50 AM »

That's enough for tonight (morning your time). I will continue the post tomorrow showing the construction of the carriage and I beam rails along with boring the tube and the finished product.

keep well
shooter2

Mike H. · « **Reply #4 on:** July 13, 2011, 02:19:17 AM »

Terrific project at an even better price! Please keep posting pics of the build. Thanks.

Artilleryman · « **Reply #5 on:** July 13, 2011, 03:49:33 AM »

Very interesting, thanks for sharing.

Double D · « **Reply #6 on:** July 13, 2011, 04:44:02 AM »

I don't know much about casting meta,l but a I know a little bit about the history of casting cannon and how they did it and why. Cannons were cast muzzle up with a large head so impurities floated to the top and would be near the muzzle and and center line and away from the breech.

Others can comment on your alloy which I don't think is right.

Since you pour was from the breech end I wouldn't suggest you consider shooting this gun.

Don't be discouraged, in fact be encouraged...you are doing something we all would like to do. Others her can give you some additional tips. Don't give up go for it!!! Great project!

Cat Whisperer · « **Reply #7 on:** July 13, 2011, 05:25:54 AM »

COOL project -

of the details - I really like the clamp for the rough casting in the lathe!

Keep the pix coming! They're fascinating and educational!

DaveSB · « **Reply #8 on:** July 13, 2011, 06:24:07 AM »

You could always sleeve the bore with 4140.

RocklockI · « **Reply #9 on:** July 13, 2011, 07:00:18 AM »

Shooter 2 good work !

I don't know much about sand casting ,but anyone that can melt copper/bronze is off to a good start .

Have you though about Lost Wax Casting ? It has some big advantages . You could take that same positive and and build a silicone mold then pour as many 'waxes' as you want .

Good luck with it !

Gary

shooter2 · « **Reply #10 on:** July 13, 2011, 02:06:52 PM »

DD,
In discussions with the Foundryman we considered which way up (Breech or Muzzle) and I pointed out the historical records as well. I was guided by the content expert who told me that the relatively small size would work better with the larger part (breech) at the top and a bulbous sprue which ended up weighing about 3 pounds would be the receptacle for impurities. He was part right, it poured well and most but not all impurities ended up in the sprue which I cut off with an Angle Grinder. The Bronze was actually composed of old Fire Department hose fittings which he had copious quantities of. The material was consistent in quality and composition. No worries about firing it, Australian Laws (Queensland) make it difficult to get it registered as a firing device so it may remain decorative on the dining room table for the forseeable future. My goal was to make something bigger than I usually do and learn some new skills, not necessarily come up with a firing cannon.

Rocklock 1,
Don't know much about Wax casting but it would have to be cleaner than the sand we used. Next time.

Shooter2

GGaskill · « **Reply #11 on:** July 13, 2011, 02:14:23 PM »

Here is a link to a thread about casting a half scale mountain howitzer. Mine were poured vertically with the breech down and with a progressive fill such that hot metal was being added to the top of cavity as the cavity filled with the shrink head being the last part that was filled.

shooter2 · « **Reply #12 on:** July 13, 2011, 08:24:17 PM »

GGaskil,
Interesting thread, did you end up getting the barrel lined or did it stay in its natural state?

Cat Whisperer,
The wood blocks were an expedient measure that turned out much better than I could have hoped. The barrel was mounted between centres but I had nothing big enough to hold and drive the breech end. My biggest lathe dog barely contained the muzzle end after smoothing. The hardwood gave an excellent grip, was kind to the Bronze material in that it did not dent it and was easy to balance for a good and safe turning. The bolts that hold it together were all thread rod cut off as necessary. When you are out in the bush, you use what you have.

Now, onto the next section of the build.

shooter2

shooter2 · « **Reply #13 on:** July 13, 2011, 08:42:16 PM »

After turning the barrel to shape and giving it a bit of polish with sandpaper I turned my attention to the trunnions. I mounted the barrel on the milling machine and used an indexing head to align the trunnions vertically. When satisfied it was as straight and level as I could make it I used my boring head to cut the trunnions. My light bulb moment came when I realised I could turn the cutter to the inside and run the boring head in reverse, effectively giving me a left hand cutter without the machining. Of course this only works if your boring head has a lock to stop it unscrewing during the cut. Unfortunately I cannot locate photos of this phase.

The next series of photos show the final polishing of the barrel and the start of the carriage construction. The carriage is based on a William Green plan for a front pintle mount that was originally meant for a 9 inch Dahlgren Gun. I made some modifications as I went along to make up for the large scale and for things I did not have. The material is Mild Steel 3/8 inch thickness cut to shape freehand on a band saw and then ground and filed to final shape.

The trunnion diameters were reduced from an as cast 31mm to 23 mm. The side plates were drilled first and then cut to allow a half round recess for the trunnions.

shooter2 · « **Reply #14 on:** July 13, 2011, 08:58:52 PM »

The area between the trunnions was finished the old fashioned way - files, successively finer sand paper and lots of swearing.

The boring of the barrel was delayed for some time as I did not have a 3/4 inch (19.08 mm) drill bit of sufficient length or the money to buy one in Australia. I had quotes for up to $300 for an 18 inch 3/4 inch drill bit from suppliers in Melbourne and Sydney. Luck was on my side with the re-valuation of the Aussie dollar against the Greenback. I ended up ordering from ENCO in the States the 18 inch bit, a 1/2 inch 18 inch bit, a 1/2 inch 12 inch bit and hundreds of machine screws I have needed for years in 3mm, 4mm, 8-32 and 8mm along with taps and dies - all delivered to my local country post office in 8 days for less than $300.

The following photos show the 1/2 inch bit followed by a 9 inch 19mm bit I had on hand and finally the 18 inch 3/4 inch bit.

Making the most of the lathe bed!

shooter2 · « **Reply #15 on:** July 13, 2011, 09:12:10 PM »

Switching to the milling machine, I made my I beams from scratch using 20mm square mild steel bars that I had in my scrap bin. I made some basic calculations and squared the beams up with a 32 mm cutter. I then used a 1/2 inch cutter in passes of less than 0.5 mm to create the beams. The bars were clamped directly to the table with three clamps that were applied and released as the cutter was brought along manually. At no time was the bar clamped by less than two clamps and there were no incidents of movement during the process. I was worried about stress being introduced into the beams by the cutting but when released from the table there was no discernible movement or twisting.

shooter2 · « **Reply #16 on:** July 13, 2011, 09:27:11 PM »

You may have noticed in the last photo of the previous post the carriage is welded together. I had considered machine screws or rivets but in the end my impatience won out and I welded the parts together. No real problems were encountered in this process, the plate was thick enough not to warp and by using clamps and taking my time (eventually) I had a reasonably square and straight cannon carriage. Just to be sure I skimmed the bottom with the mill to make it absolutely smooth and flat. It was out less than 10 thou across the whole bottom.

The final part of the puzzle were the slots at the back of the barrel and a method of locking the barrel into position using the slots. I made up a device I called a ladder that had cross pins with a 3 mm gap between each pin and 9.5mm across. It was made from 3/8 steel and locked onto the carriage with machine screws from underneath. The slots were cut into the breech end of the barrel using a 3mm cutter in a horizontal mill. The slots are 12mm across and have 3mm spacing between each one. To lock the barrel to the ladder I used a slitting saw on the mill to cut a device out of 12mm square bar I call a Key. The photo tells the story, it works brilliantly.

shooter2 · « **Reply #17 on:** July 13, 2011, 10:03:06 PM »

The last thing to do is show the finished product. I painted the beams and carriage using a Killrust Flat Black spray can with the top of the beams masked off to keep them a natural steel colour as that is where the carriage would run if it was ever used. I added 1/2 inch brass strips to the sides and fixed them to carriage using 1/8 brass rivets. The rivet holes are blind and 3.1 mm in diameter, 1/8 is 3.18mm so there is considerable tension holding them in. The support for the trunnion is turned from 60mm brass bar and also riveted on. It was an afterthought that saved me having the trunnions overhang or my being forced to trim them back.

I realise this cannon and carriage are not perfectly authentic, after all who ever heard of a Bronze Rodman Gun? The carriage was made up as I went along to the standard that I always work to, it made me happy. My goal was to learn how to do some new things and to have a finished product I could be proud of. I feel I have achieved what I set out to do and the next cannon may be more authentic and detailed. However I do not think I will aspire to the level of Mike and Tracy and make everything from scratch. I am hoping my upcoming Cannon Viewing World Trip will give me enough information and material to keep me going in my future retirement when I will finally have enough time to do everything I have planned or not, who knows.

Anyway, for your enjoyment it is my pleasure to present the only Bronze 10 inch Rodman Gun in captivity.

shooter2 · « **Reply #18 on:** July 13, 2011, 10:10:59 PM »

Just some last detail photos I had.

Cat Whisperer · « **Reply #19 on:** July 14, 2011, 01:54:29 AM »

WOW!

There is but one word that screams out - CALENDAR!

What a master piece - and thanks for documenting the process!

Mike H. · « **Reply #20 on:** July 14, 2011, 02:52:09 AM »

Very nice work!!!

Zulu · « **Reply #21 on:** July 14, 2011, 03:51:26 AM »

I wish it was sitting on my desk!

Zulu

seacoastartillery · « **Reply #22 on:** July 14, 2011, 04:18:11 AM »

Shooter2, What a superb job you have done. I agree with Cat Whisperer; your Bronze Rodman is an excellent contender for a GBO Calendar slot. Guys, you have absolutely no excuse for not posting in-process pics now! This gentleman from OZ has accomplished, not only the build, but the photo documentation with logical perfection.

Love it, love it, love it! What a beauty!!

Tracy and Mike

Ex 49'er · « **Reply #23 on:** July 14, 2011, 05:27:51 AM »

Simply Beautiful and Amazing work!!!!!!!!

Congrats on the Kewpie.

RocklockI · « **Reply #24 on:** July 14, 2011, 07:10:02 AM »

Wow what a beauty

! Good job certainly worth a kewpi !

Zulu · « **Reply #25 on:** July 14, 2011, 11:13:19 AM »

Shooter2,
You said you cut the metal for the carriage on a band saw. Was this a vertical saw? The Seacoast boys, Mike and Tracy, have said that their band saw is one of the most used tools in their shop.
What kind is yours?
Does anyone think a metal cutting band saw blade would work in a wood cutting band saw? I tried it once and it didn't do so well on 1/8" plate. My saw uses a 93 1/2" blade. I really need to be able to cut steel like that. It would open up new avenues for my carriages.
Zulu

armorer77 · « **Reply #26 on:** July 14, 2011, 11:27:35 AM »

Most wood cutting band saws move way too fast to cut metal . Cuts great for a few seconds , then burns up the blade . Ed

projector · « **Reply #27 on:** July 14, 2011, 11:30:21 AM »

Nice work Shooter2!

Quote from: Zulu on July 14, 2011, 11:13:19 AM

Shooter2,
You said you cut the metal for the carriage on a band saw. Was this a vertical saw? The Seacoast boys, Mike and Tracy, have said that their band saw is one of the most used tools in their shop.
What kind is yours?
Does anyone think a metal cutting band saw blade would work in a wood cutting band saw? I tried it once and it didn't do so well on 1/8" plate. My saw uses a 93 1/2" blade. I really need to be able to cut steel like that. It would open up new avenues for my carriages.
Zulu

Zulu,

With cutting steel you really need even pressure and cutting oil to lubricate the blade. I'm sure you're a stickler on keeping oil away from you wood working tools. We have a horizontal band saw at work that works well and is very accurate. They do take up space though. I have used a metal cutting blade in a chop saw with decent results.

rifleshooter2 · « **Reply #28 on:** July 14, 2011, 11:43:21 AM »

Wow thats a nice piece. Well done!

shooter2 · « **Reply #29 on:** July 14, 2011, 11:45:50 AM »

First up, WOW, thank you so much for the kind words. It is great to hear such things from a group of people I consider to be the experts in the field. And a Kewpie doll is just too much, the icing on the cake. Thank you again.

Zulu,
The bandsaw I use is a basic metal cutting bandsaw that is convertible from horizontal to vertical, maximum material width 6 inches. It cost me less than $300 on sale. Bandsaws of this type I have seen advertised in US machine suppliers like Grizzly. I believe the problems you experienced with the wood bandsaw may relate to blade speed. Wood saws often move too fast to be controlable with metal. I keep mine on the middle pulleys and I cut the sideplates in the vertical position on a plate I added to the saw to increase rigidity. The favoured blade is a 14 tooth per inch type. It is slow going and requires the patience of Job at times but the results are worth it.

I would not be without a bandsaw, horizontal or vertical. After my lathe and drill press it gets by far the most use in the workshop. As an aside, I have put wood blades (6 teeth per inch) on it and it cuts wood very happily with the speed increased by changing the pulleys.

shooter 2