Author Topic: 1026 or 4140 for 1.75" howitzer (Read 1280 times)

accuratemike · « **on:** February 28, 2006, 10:56:20 AM »

Hello ! This is my first post. Great (!) forum guys, I've lurked a few days and skimmed 22 pages of posts. Too much good info ! I'm looking to build a golf ball howitzer. My plan is to use a chunk of 4"od x 1.125" w seamless. The barrel would be 4" at the breech and taper to 3 1/2" at the muzzle. About 18" of tube and 21 5/8" long overall. (Kind of like a chubbier version of Gunsmoke's Golf Ball Field Cannon) I want to do a threaded and welded chamber/breech plug. Probably will weld the trunions in as well. I want to start calling around for a piece of tube and have a question before I begin. I noticed that the venerable Wisconsin Mountain Howitzer builder used 1026 for his project. I have also seen a lot of 4140 used and lauded. Knowing the general specs and construction techniques, would I be better off going one way or the other ? I don't have deep-hole drilling capability at the home shop (at least not 1.75"x18"), so I will be welding. I understand that the 4140 may present more of a challenge to weld, will I NEED it (4140)? Can I use dissimilar metal for plug/plate/trunions or will I need 4140 for all of it ? Since 18" of something this size will likely be a drop, I may need to take what I can find. Would either/or (1026/4140) be suitable ? Anything else (within reason) I should know ? I am a machinist (mostly automotive) working in a well equipped shop. I want to do this in my home (hobby shop) as much as I can, but anything is possible. Thanks in advance for your input, this is a super site. I bounced around the web for a couple of weeks before I found you folks. More here in two days.
MIKE

Sorry for going long

Work stuff: http://www.accuratepower.com/Machine
A home thing: http://www.accuratepower.com/Torch

Cat Whisperer · « **Reply #1 on:** February 28, 2006, 12:31:06 PM »

Welcome!

Looks like you do your homework.

A mild steel would do just fine for golf balls. Shooting iron or concrete at high velocities (read much higher pressure) may be in another league.

The advantages of being able to weld a mild steel easily vs the preheat and slow cooling and VERY good welding techniques are obvious.

Double D · « **Reply #2 on:** February 28, 2006, 12:39:54 PM »

Use the 4140 it cheaper than 1085. If it's take what you can gett make sure all the metal is th same composition.

Use the same material for trunnions and breech plug. Consider threading and pinning with a set screw the breech plug much like found in a muzzleloading rifle. You can then pull the breech plug for maintenance.

Oh yeah with a gun this robust make your self a slug mould an shoot lead or zinc slugs.

GGaskill · « **Reply #3 on:** February 28, 2006, 12:54:37 PM »

4140 is gross overkill for a golf ball howitzer. The shot has so little mass that you couldn't get the pressure up high enough for the extra strength of 4140 to come into play. Even if using denser shot (like lead [one lb] or zinc), I would use 1018 (plain cold rolled mild steel) which is easily weldable.

If you are going to thread the breech, I would not weld the breech plug, as being able to remove it will make cleaning and sponging much easier and allow a more thorough job to be done. Just have at least an inch of threads (two inches would be better.) Put some grease or non-hardening gasket sealer on the threads to keep the fouling out.

Assuming you can find a piece of 4 x 1 1/8 wall seamless, remember that the hole is not as round as a drilled hole.

accuratemike · « **Reply #4 on:** February 28, 2006, 04:54:45 PM »

Thanks ! I think I have an idea what I will start looking for anyhow. I may want to occasionally send a pound skyward, I'll keep the pressures in mind. I do have welding equipment at home, but I also know my limitations. I have a "Certified Nuclear Plant Weld Inspector" welder buddy, if I need him. I'll keep the same material notion in mind as well (Wisconsin Howitzer Builder used 1018 & 1026, mostly just wondering after I saw that). I had thought about removable plugs, I guess that means a removable back plate as well. I'd have to re-think that a little bit. (Zipping things together with a few beads would be faster/easier, I'll have to factor in the years of use & maintenance vs. hours in the shop) I lean twords robust ( I always liked the look of the H&R 10ga slug gun too.) I considered threading the breech to avoid the BIG "J Weld" shown on the Wisconsin site. I was looking at the description/picture of how to thread & weld liners for the basic idea. I assume that the weld in these is only there to keep the plug screwed in (or substitute the setscrew method). At the shop we usually shoot for 1-1 1/2 diameters worth of thread engagement (minimum). I'll likely try to achieve this. My lathe threading skills are "OK", I can see wasting a plug or two looking for a good fit, but only one chunk of barrel, wish me luck (skill). One nearby supplier (Tubular Steel) showed a few 1.75" id tubes in my range, I just wanted to sound like I knew what I was after, before I called. OD can be worked around a bit, the design is not etched in stone (just ACad), I'll see what I can get. As far as ID finish, we have a Sunnen rigid hone at the shop. I may be able to use it. I don't think we have an 18" mandrel though, I may have to work from both ends. Or, I might look at adapting the cylinder head cam align boring tool to finish the bore. I just wanted to avoid having to bore a 1/4" from 1 1/2" id stock (if I can). Thanks for your input, it is GREATLY appreciated. MIKE

PS check out the Cat compressor mount at the bottom of this page. Kind of mortar-esque, eh ?
http://www.accuratepower.com/Machine/fabrication.html

Double D · « **Reply #5 on:** February 28, 2006, 05:18:08 PM »

With a removable breech plug there is no back plate. The cascabal is part of the plug.

The plug should be machined much like a Mauser rifle with the face of the plug fitting against a breech plug seat in the barrel. That seals the bore. The Reinforce on the cascable does not touch the back of the barrel being about .002 off like in the Mauser rifle. Simple allen set screw in the bottom of the barrel keeps the plug from turning if it were to come loose.

George says 4140 is overkill...ain't no such thing in cannons. But 1018 and 1025 are just fine.

Cat Whisperer · « **Reply #6 on:** February 28, 2006, 05:25:49 PM »

accuratemike -

I've heard about those folks that weld up the nuclear stuff - always talked about with reverence and awe. That's exactly what you want for welding on a cannon or mortar!

Cat Whisperer · « **Reply #7 on:** March 01, 2006, 01:22:39 AM »

I agree with DD - it doesn't hurt to overbuild when it comes to safety.

Let me just add that 4130 and 4140 are VERY similar and on the edge of what's considered weldable. 4130 is better and more commonly used where welding is needed. Strenght of both can be tremendously increased by heat treating, but then you run into the tradeoff of gaining strength and also gaining brittleness in the process. Look at the famous situtation with early serial number Springfield rifles.

Low carbon steels revolutionized the cannon making industry in the 1800's. So much better than anything cast. It's well worth the hour or so reading about it. Perhaps considered as 'just plain old CRS' they still work well today with good designs and prudent loading.

Let me emphasize keeping all three in mind: choice of material, good design (form, dimensions and clearances) and prudent loading.

accuratemike · « **Reply #8 on:** March 01, 2006, 06:24:51 AM »

How about Hot Rolled vs Cold Rolled ? Wisconsin Howitzer Builder used Hot Rolled. You guys have mentioned Cold Rolled. Preferences ? Thanks (in advance). MIKE

GGaskill · « **Reply #9 on:** March 01, 2006, 08:30:46 AM »

Hot rolling shapes the steel while it is soft so there are no residual stresses in the material. This is both good and bad, as the metal does not move when machined but it is somewhat lower in strength for similar alloys (hot rolled mild steel is usually 1020 versus the 1018 of cold rolled.)

Cold rolling work hardens the metal which makes it somewhat stronger but leaves lots of residual stress in the material. Depending on how much and what type of machining is done, the metal can warp slightly. Whether this matters depends on tolerances and other things related to precision. In smoothbore cannon making, it usually is not important as the machining is symmetrical and the tolerances are loose.

Hot rolled is usually significantly less expensive than cold rolled.

Something else you might consider (from the "Planning a sodacan mortar seeking comments on my tube design" post)--"Seems like people aren't really concerned about making accurate models at first but later on they wish they had." You could make a 1/2 scale mountain howitzer from a piece of steel the size of which you have been describing.

accuratemike · « **Reply #10 on:** March 01, 2006, 12:06:42 PM »

Thanks. I think I understand. The first place I called actually had exactly the size chunk I was looking for. 4"od x 1.125"w x 18" 1026 CR seamless. Too bad it was very expensive. Minimum purchace, cutting charge etc. . My next door neighbor (work) is huge pipe fab shop. I think I'll take a walk over tomorrow and see what they may have laying around and/or what the piece would cost them. I suspect that their volume goes a long way in this field. At least I know that I can find this stuff.
As far as scale, I started by scaling a Mountain howitzer to 1/2 and thinking along those lines. The taper is a hitch though. I really want to build this barrel at home. I don't have tapering at home. The lathes at work could knock it out, but it is a work vs. home thing. This will be my first "large" cannon and I am working tword a goal of a full-scale piece. The rub is which conflict. My eldest son is a drummer in a Revolutionary fife & drum corps. We are all SAR's and the whole thing goes back to my Father's interest in the Revolution and our family's part in it. So, for me, scale is of earlier artillery. Most of these have more ornate castings that will be challenging to do on a lathe. I did see the Revolutionary howitzer (Hern's), but I'm not in love. I have nowhere to go with a 1/2 scale piece, and it won't end up being a smaller version of something I eventually want to build larger.
So this one is relegated to a home project for fun, as a toe in the water to what I may do. As such, I was going to go Parrot-esque (ala Gunsmoke) with two basic diameters, and the size of a 1/2 scale Mountain Howitzer (that I have always admired, Mountain Howitzers ARE cool).
I also have two big-lathe owning friends that are watching this keenly. Both wanting to build replica, full scale barrels. You never know where we may end up.
Thanks for ALL of your insight. I thought that not sounding stupid on the phone would help to lower my costs, not so far (but I'm not done). Enjoy, MIKE

CU_Cannon · « **Reply #11 on:** March 01, 2006, 12:43:03 PM »

IÂ’m a big fan of mountain howitzers. At some point I will build one, perhaps full scale but most likely half scale. Mortars are a good place to start as well. They require less material than a cannon and beds are easer to construct than carriages. I like the high arc of the projectile.

Welcome to the board and keep up posted.

You can delete your duplicate posts by clicking the x in the upper right corner of your post. I have problems with multiple posts all the time.

guardsgunner · « **Reply #12 on:** March 01, 2006, 01:20:56 PM »

accuratemike,
With you interest in early stuff, you may want to take a kook at a thread back a page or so about the Daniel King Howitzer. It is a small gun about the same size as a half scale mt howitzer.

GGaskill · « **Reply #13 on:** March 01, 2006, 10:02:35 PM »

I also have two big-lathe owning friends that are watching this keenly. Both wanting to build replica, full scale barrels.

To build a full scale barrel, particularly if you have to drill it, requires a really long lathe. Almost twice the length of the barrel. Plus a really long drill.

accuratemike · « **Reply #14 on:** March 02, 2006, 05:39:47 AM »

I have looked at the Daniel King threads, it is nice to have a goal. Page 2 wouldn't load last night, I'll try again now. Thanks.
My big-lathe buddies have 'em with 10'+ beds. Our "big" lathe here (at the shop) is ~60". At home I have a "little" lathe. I am helping a friend convert his "big" lathe to CNC. He needs it for better metric threading of big tubes (makes hydraulic equipment and cylinders), I like the idea of radius, ball, taper etc. He is one of the folks with some cannon interest as well. His drilling/boring gear is actually too big for my golf-ball aspirations. That's why these guys are leaning twords large scale. I thought I'd get things rolling. Once they see a firing or two, I hope they get the bug.
MIKE

GGaskill · « **Reply #15 on:** March 02, 2006, 10:35:12 AM »

The taper is a hitch though. I really want to build this barrel at home. I don't have tapering at home.

If you mean your home machine doesn't have a taper attachment, that shouldn't matter. On all of the barrels I have turned, I have done the taper using the tailstock offset method (most of them, and all the mountain howitzers) or a variation on the "count the clunks" method (essentially machining a series of increasing or decreasing diameter cylinders and finishing with a lathe file.)

accuratemike · « **Reply #16 on:** March 02, 2006, 11:21:12 AM »

Ok, OK. You got me. Sure, I can taper by either of those methods. I guess I should have said "I want this to be easy" (so there is a chance I'll finish it). If the metal turns out to be expensive enough, I may have to go scale due to the size of the investment. Wouldn't want to turn a silk purse into a sow's ear. I could be made quite cheeky with just function though. Enjoy, MIKE