One Inch Bore Mountain Howitzer

[The Jeff]

Hello all. I must admit I lurk more than I post, but I do read this board daily. I'm also not much of a machinist, I know just enough to be dangerous.

Anyway, inspired by the "Shooting the 1 inch bore" post, I decided I'd attempt a 1" bore mountain howitzer. While the mountain howitzer really isn't my favorite kind of cannon, they definitely have grown on me while researching/building mine. Also I think they're about as long as my lathe can handle.

I started Monday afternoon with a 1-11/16" piece of 1018. I drilled out the chamber with a 3/8" bit. It should be more like .45", but unfortunately I don't have a bit long enough in that size. But I can always come back and enlarge it. Next I drilled the bore with a 63/64" bit. It's pretty rough, but I tell myself that I drilled it undersize so it can be cleaned up to 1". 

Sorry, I forgot to take pictures.


Tuesday I started working on the outside. Like I said, I'm no machinist. I measured from the muzzle and marked off various points where the diameter changed and went at it. This involved quite a bit of squinting, measuring, and praying. I've been told real machinists can use those numbers and tick marks on the handles to figure out where they are.


My patented muzzle swell allows the gunner to fire magnum loads without fear of the normally thinner muzzle splitting.


Today I drilled the vent and finished up the outside. I'm pretty sure that all small drill bits and taps have secretly sworn an oath to break on me. But today after about 5 minutes of sweating bullets, copious amounts of oil, and frequently stopping to clean off the chips I managed to get the 1/16" vent done.

Tapering the barrel was pretty tough too. I took the muzzle down to the right size and then tried to even it out back to the recessed part over the chamber. Again I've been told real machinists can do it a little more accurately than by eye.

With that done, I started filing and sanding everything. There's still a bunch of lines on the barrel that need to be worked out, but that'll be for tomorrow.


The patented double knob allows for a finer degree of control when moving the tube around with block and tackle

Jeff

[GGaskill]

Looks nice so far.  How are you going to attach the trunnions?

[Cannoneer]

You're doing great; what type of carriage are you planning?

[The Jeff]

This evening I got the trunnions roughed out. They started life as a 15/16" chunk of 1018 so they should weld fine to the barrel, although I still need to figure out the best way to notch the rimbase end to fit around the tube.

Looks nice so far.  How are you going to attach the trunnions?

As best I can tell, I'll only have about .2 inches of wall thickness under the trunnions. I doubt I can do any sort of threading so I'll probably just weld them on. Most likely I'll put a small pin in the center of the trunnions that will fit into a shallow hole on the tube for locating them accurately. I do need to figure out the easiest way to notch the trunnions though. My metal working equipment is pretty limited.

You're doing great; what type of carriage are you planning?

I'm not sure. The pack carriage looks easiest to build, but the prairie carriage looks better I think. I've found more detailed plans for the 1st model prairie carriage, so I'll probably go for that one.

Jeff

[GGaskill]

The ones I have made and been associated with the making of have put flats on the sides of the barrels where the trunnions go and then welded the trunnions in place.  Depends on wall thickness as to how deep the flats can be.  But they have never been deeper than just getting the edge of the rimbase flush with the tube.

[rludwig]

One method for making the trunnion pieces is to turn the rimbases on a single piece separated at the final distance. Then drill a pilot hole at the exact center and cut the  curve with a hole saw that matches the OD of the barrel at the attachment point. It will be necessary to cut from both sides and use a slow speed and feed with lots of lubrication. I was able to do this with a drill press. The ridge left in the middle when the parts separated was removed with files and a chamfer around the edges was done to increase the penetration of the weld.

[GGaskill]

My problem with curving the rimbases to fit is that it leaves them really thin in the area of highest stress.  A recess makes them thicker.

[armorer77]

I use an end mill and inset them into the barrel . Filling any gaps , top and bottom with weld . Armorer77

[The Jeff]

Thanks for the suggestions for attaching the trunnions! I haven't done much with it today except smooth up the barrel.

I did draw up the ideas below just to try and get a better idea of how to secure the trunnions. It's funny how after I drew them I checked this thread and saw they were the same as a lot of your ideas. Anyway, Option B was my original intention, but I'm leaning more to Option D now. I don't have a milling machine or end mills, but I think I could do it with a file.



On another note, how much powder do you think would be appropriate? As it stands now my powder chamber holds about 38 grains of FFF, which is pretty close to a scale 1/2 pound load.
3500 grains * .2165^3 = 35.5 grains.

[GGaskill]

Option D would be OK if there is not too much air between the edge of the rimbase and the tube.  Don't want to melt the edge of the rimbase all the way up.

[The Jeff]

Today I realized I'd marked the center of the trunnions in the wrong spot. They were about a quarter of an inch too far back. Glad I caught that before doing too much work. Anyway, I moved the vertical mark to the right spot and used this setup to find the horizontal mark. Probably not the most accurate but it was about all I could think of.



Next I drilled a shallow hole for a stud on the center of the trunnions to slip into and filed a shallow notch in the barrel.



Welding will have to wait until Monday, but here's everything assembled.

[The Jeff]

Drilling the bore left it pretty rough and I've kind of been dreading smoothing out the inside because I wasn't sure how to do it. I'm pretty new to metal working and haven't built up the equipment/tools/knowledge that many of you have. My first thought was sandpaper wrapped around a stick, but that took ages and didn't seem to do much. Then I decided I needed a reamer of some sort.

About 30 minutes later I'd built this:



It's a closet dowel taken down to just slip in the drilled bore, a square notch cut into one end to hold a piece of tool steel, and two screws to control the height. I wasn't very optimistic about it working, but I tried it anyway. I was really amazed at how well it worked, even though it was just cobbled together. At least I thought it worked well in my limited experience. After a few hours I had the bore up to exactly one inch. It still has some of the deeper ruts from drilling, but a lot better by far.

Tomorrow I'll try to weld the trunnions during my lunch break and hopefully test fire!

[Cat Whisperer]

I always admire folks that get the job done with what they have!

There's always the next project to make improvements on.

[The Jeff]

Well today I got the trunnions welded on during my lunch break! They look pretty bad, but I can clean that up with files later. I tried to get more weld on there than I needed so I can file them down and form the rimbases. I also plugged up a dent near the touch hole that was a result of careless hammering earlier. I used a center punch to make a divot for my 1/16" bit, but I hit it with a light hammer and the punch bounced off and hit again just beside the first divot. Next time I'll take Mike and Tracy's advice about using a heavy hammer!


Here it is, splatter and all.

And click here for a video of it's first shot! I used 38 grains FFF and 1 ounce of bird shot. I set a thin piece of plywood out in front of it and a few of the #7 pellets embedded themselves into the wood. Eventually I'll have to make some real canister loads. And that carriage is not the final product. 

I always admire folks that get the job done with what they have!

There's always the next project to make improvements on.

People sure aren't kidding when they say making cannons is addictive, This one isn't finished and I've already got plans for the next.  At least I'll know a bit more about what not to do.

Hi Jeff
Nice barrel Can you silver solder them with grade 5 silver if you need some i'll send a stick it hold really great great barrel AMG

I appreciate the offer, but I've already welded them on! Thanks though.

[little seacoast]

Love the video, the bark and recoil are really neat.  You can lay serious siege to a ground hog or two with that.

[The Jeff]

I've been a bit busy lately, but I'm still plugging away on this project. So far I've gotten the trail, axle, and cheeks cut out. They're made from some maple that came from a tree I cut down a few years ago. The cheeks are a bit too big, so I'll need to cut them down some. I'd like to have the carriage at least functional for the ring in the spring shoot, but that'll depend on how hard the wheels are to make. Most likely I'll make the wheels a hexagon and then cut the curve with a router.

[Cat Whisperer]

Take that last picture and inset a picture of it firing in the upper left corner and put it up for the calendar!

[Cat Whisperer]

Love the video, the bark and recoil are really neat.  You can lay serious siege to a ground hog or two with that.

Pete  -   I have challanged, in previous years, to post pix of woodchucks killed by cannons.  Not yet seen any. 

[The Jeff]

Love the video, the bark and recoil are really neat.  You can lay serious siege to a ground hog or two with that.

Pete  -   I have challanged, in previous years, to post pix of woodchucks killed by cannons.  Not yet seen any.

Believe me, the thought has crossed my mind, but I'm not sure how well it'd fly. I recall a big to-do about that guy's page about hunting deer with a mountain howitzer, although I'm almost positive it was fiction.

But who knows, spring is around the corner and muzzle loaders and electrical ignition systems are legal here in Virginia. 

[little seacoast]

There is a fat old woodchuck down below the orchard that I've considered terminating ( he climbs my pear tree and eats the fruit) but I guess he's safe since he's a homeplace critter. Same deal with the small covey of quail that run the place.

[GGaskill]

If you still would like to have a .45 chamber, the bore is now big enough for an ordinary drill extension for the 29/64" drill.

[Cat Whisperer]

If you still would like to have a .45 chamber, the bore is now big enough for an ordinary drill extension for the 29/64" drill.

Good observation.  I have a 29/64" drill bushing that I use to size .45 cal cast bullets.

[dominick]

There is a fat old woodchuck down below the orchard that I've considered terminating ( he climbs my pear tree and eats the fruit) but I guess he's safe since he's a homeplace critter. Same deal with the small covey of quail that run the place.

You can just yell at him like the Geico commercial.  " hey woodchuck! quit chuckin my wood!" 

[The Jeff]

I cut the notch in the axletree for the axle which is a stainless shaft I salvaged from a broken printer about 6 years ago. I knew it'd come in handy someday! It's still a bit long and the ends need to be thinned down, but I'll do that once the wheels are built. I also notched the trail for the axletree and drilled the holes for the strap underneath.



I also started a practice wheel from pine. I want to make sure these things are within my abilities before I go cutting up my maple into little bits of firewood.  Please don't go looking too closely at the picture below, Zulu.

[Zulu]

I watch with great interest!
Zulu