anyone ever make a cannon out of 4130 tubular steel

[gassaway]

doing a cannon in 4130 tubular 1" bore stepped gun 32 inches long back end is 3" in diamter. plan on tapping back end for screw out plug. anyone have anything simular. Im thinking of a 1890 looking pack gun love to see some pic and get advise

[Double D]

Is 4130  welded tube or seamless?

[tnmike55]

Here is one such cannon made out of 4140 seamless tubing. Before you ask a 33 1/2 " drop with a 7 inch OD and 1 1/4" walls  cost
530 bucks here in NC.

 http://www.buckstix.com/HowitzerTools.htm

[tnmike55]

The cannon in  the link was actually made of 1026 HR seamless. 4140 would be considerably stronger and somewhat more expensive than 1026.  Either material would work.

[gassaway]

wall around my breach are 1" and bore is 1 " it is stepped to 1/4"  last 8 inches do you think it would be safe with say max charge of 300 FG? and yes it is seamless tubing 4130

new at this so lotta questions

[Double D]

Following the safety guidlines we practice on this board your breech walls are think enough. The breech plug should be the same thickness minimum als.

Your load exceeds safe load recomendations. See our post at the top of the board titled Safe loads and cannon plans.    You will find the recommend safe load for 1 inch bore is about 180-190 grains of  Cannon grade.  It is recommended that you reduce your load substantially from that and work up not exceeding that, and especially if you are going to use Fg  and lead balls.

[gassaway]

thing tapping rear for 1 1/8 plug is sufficeint? gives me .125 on threads to grab?  what tpi would you reccomend?   12? say 1 1/2 inch on thread back there   thanks for info on powder

[GGaskill]

Think tapping rear for 1 1/8 plug is sufficient?

What thread pitch are you planning to use?  Cutting threads that large into a deep hole is a serious challenge using a tap; it would be much better to thread in a lathe since the threads will be concentric with the bore.

[gassaway]

some where between 7 to 12 threads per inch (tpi)

[GGaskill]

The minor diameter for a standard 1 1/8-7 thread is about .939" (this is from calculation as I don't have a sheet for this handy).  I would prefer that the minor diameter be at least 1".  A non-standard thread of 1 1/8-8 should give you that, especially as one can do almost anything he wants when using non-standard items.  But you will have to make the pieces yourself.

If you aren't intending to make a breech loader, you could bore the breech area round, and shrink fit a solid plug and weld around the back end.

[Cat Whisperer]

tnmike55 -

Welcome to the board!

Looking at his diagram with the breech plug welded where it is good.  

Let's review a few principles:
4130 is weldable (by CERTIFIED welders - must be preheated to specific temperature and cooled slowly).
4140 is just past where it should be welded.  (Crack formation is very possible with 4130 and 4140).

Note that you MUST protect the junction open to powder pressures from corrosion - by shrink fitting (Heat the tube and insert the plug, let cool) otherwise you will have long-term corrosion issues - cracking.

Threading will loose 1/2 the strength by virtue of cutting the threads - stress risers.  Finer threads are generall considered stronger.  (Also more problematic in manufacture.)

Thrust pressure to the rear is a function of inside pressure and the area on the back surface inside the powder chamber.  Smaller diameter chamber smaller area.

Doing it right is essential as knowing that you did something wrong is right after the catestrophic failure.

Follow the rules-of-thumb that have been established successfully by AAA and N-SSA for their cannons used in competition - they've been proven over the years.

[tnmike55]

 Let me say straight off the bat that I am no black powder cannon expert.

I have welded quite a bit of 4140 and never had a crack failure. Some of the welded assemblies I worked on were power hammer forging dies subjected to severe duty.  In this case the 4140 was preheated to 400F , and MIG welded to a 1018 steel plate. The entire assembly was brought to 1800F in a gas forge and quenched in Parks AA quench oil. It was then tempered at 400F for two hours. Some of these dies have been used to forge round balls on the end of 2 inch square stock and have not cracked or even distorted after thousands and thousands of blows. 

Even with this experience I think the use of 1026 on a cannon barrel would be easier. 4140 is harder to deal during welding and is subject to work hardening which can lead to cracks. I dont think its additional strength is really necessary in a black powder cannon.

The only drawback to seamless tubing is expense. It aint cheap.

[Cat Whisperer]

tnmike55 -
Sounds like you've got a grip on welding!  I respect the experience of a similar applicaiton - repetitive hammerings.

Consider the analogy of the cost of a motor cycle helmate - if you have a $1 head get a $1 helmate, if your head is worth more get something better.

The mortar in my avitar is 4140 - turned from a solid billet.  Overkill, yes.  Would I do it again, no, I'd use 1018 or 1026.
(I got a good deal in a trade for a computer plotter to a machine shop for the mortar built to my spec.)

[gassaway]

no im planning on it being a breach loader did civil war cannon crew when younger never a fan of raming home a charge. heard a few horror stories. definitly a breachloader