Author Topic: No-Lathe Mortar... Part 2 - PICS OF THE FINISHED PRODUCT ON P2 (Read 3724 times)

Cat Whisperer · « **Reply #30 on:** June 16, 2007, 07:40:56 AM »

StealthyBlagga -

You did the right thing - it will also be easier to clean and have less ability to keep burning embers inside.

Now, let's see your "..." welding. After you've ground it to the right profile of course.

Rickk · « **Reply #31 on:** June 16, 2007, 12:49:21 PM »

Weld first pass to hold it together. Grind smooth. Go over it again to fix the holes and make it look pretty.

Your weld surface area is huge, and the force is all in compression, so you should be fine.

If you are going to paint it, you can use JB weld to pretty up the weld area prior to painting.

StealthyBlagga · « **Reply #32 on:** June 16, 2007, 06:32:56 PM »

Here is the barrel before painting... as you can see, I'm relying on the paint to cover up a multitude of sins

.

Hopefully I'll have the base built, and the entire mortar finished this week.

Cannonmaker · « **Reply #33 on:** June 16, 2007, 06:56:58 PM »

My shop is well equiped with hand and power tools and I do not know what tools you may have. To clean up my weld I use a thin cut air tool then a air tool using the 2" or 3" Scottbright abrasive pads. Thoes are the ones which screw in to a disk. I am not good at remembering al the proper names. This methoud will remove the weld quite fast. ---put it on, grind it off, put more on, grind it off--- the end product, well worth the effert.

StealthyBlagga, it look good, keep up the good work.

Rick

Terry C. · « **Reply #34 on:** June 16, 2007, 07:52:26 PM »

Rick, you are thinking of the Roloc pads.

They are the neatest thing since sliced bread, we use them a lot in our shop.

We only buy the 3M brand. We use them on dirty, rusty, and often greasy surfaces and under these conditions only the 3M give decent results.

Cannonmaker · « **Reply #35 on:** June 16, 2007, 08:50:09 PM »

Terry C. I stand corrected, they are the 3M pads. when I weld Alumiun I perfer them for cleaning before the weld. They are great.

Rick

Cat Whisperer · « **Reply #36 on:** June 17, 2007, 01:56:35 AM »

Stealthy B -

It's lookin' GOOD! Golf ball launcher on steroids!

If you are going to paint it, might want to consider having it sand-blasted. I leave most of mine in-the-white, so I can use the wire brush to clean them up.

Rickk · « **Reply #37 on:** June 17, 2007, 04:22:12 AM »

The weld looks fairly nice in the picture. If it is rougher than you wish, mix up some JB and smear it over the surface with your finger.

If you are painting it, no one will ever know.

To be perfectly honest, even if you did not paint it, JB tends to blend in well with aged steel.

jeeper1 · « **Reply #38 on:** June 17, 2007, 05:14:37 AM »

The longest lasting job I ever had was a hand finisher position in a Aerospace machine shop. I couldn't even begin to guess how many Roloc discs and cylinders I used up in the 8+ years there. That's where I learned about, made and used tiajuana hones.

StealthyBlagga · « **Reply #39 on:** June 21, 2007, 12:52:47 PM »

OK guys, here is a photo of the finished product. I hope to test fire it at the weekend.

Next question: I plan to chronograph various loads so as to calculate what charge is needed for different distances. Can I use regular ballistics software to calculate the trajectory, or is there somewhere I can get mortar-specific data ? In case its not clear from my earlier posts, this mortar shoots 0.73" lead musket balls.

jeeper1 · « **Reply #40 on:** June 21, 2007, 01:58:12 PM »

Looks great.

Cat Whisperer · « **Reply #41 on:** June 21, 2007, 02:14:38 PM »

There are SO MANY variables, you'll find shooting and measuring will be your best bet.

Measure the powder.

Take a level with you to ensure repeatability.

Record keeping will be your friend.

Rickk · « **Reply #42 on:** June 21, 2007, 02:36:04 PM »

You can get a magnetic angle measuring thingy at Home Depot. Stick it to the muzzle and set it for 45 degrees.... less variables when fired at that angle.

If you were shooting heavy (lead) balls, due to the slow velocity and heavy weight the balistic coefficient isn't really in the picture and a simple excel spreadsheet that ignores drag will predict distance verses time in flight or velocity verses distance farily accurately. All you really need is a stopwatch to measure velocity and distance and maximum height if you can hear it impact. I have that spreadsheet someplace... if you want it I can find it.

For a golf ball the ballistic coefficient is definitely in the picture. From what I gather, a golf ball is a complex thingy to understand. Cat Whisperer is giving you a better suggestion than I could possibly give.

rifleshooter2 · « **Reply #43 on:** June 21, 2007, 03:57:45 PM »

Nice job. Your hooked for sure now

Andy

EL Caz 66 · « **Reply #44 on:** June 21, 2007, 04:18:23 PM »

Nice Job, let us know your results.. fire & smoke video would be nice..

Tropico · « **Reply #45 on:** June 21, 2007, 04:45:34 PM »

I been just sort of hanging back watching this thing develop..., I wasn't to sure what you were going to do for a carriage and all .,but you turned out out a true to form Confederate Mortar right down to the carriage . Bravo !

it looks buffed !

StealthyBlagga · « **Reply #46 on:** June 21, 2007, 04:55:30 PM »

Quote from: Cat Whisperer on June 21, 2007, 02:14:38 PM

There are SO MANY variables, you'll find shooting and measuring will be your best bet.

Thanks for the advice. I'm open to this approach - how do you guys typically keep track of where the shot actually goes ? I'm not sure I'll be able to spot the "splash" from a .73" musket ball. Any suggestions would be great.

lance · « **Reply #47 on:** June 21, 2007, 04:59:30 PM »

good looking mortar, you know this stuff is habit forming..............

GGaskill · « **Reply #48 on:** June 21, 2007, 05:25:54 PM »

Can I use regular ballistics software to calculate the trajectory, or is there somewhere I can get mortar-specific data ?

No, regular ballistics software is designed for flat trajectories and conventional bullets. In fact, once a round projectile gets over 9/16" in diameter, it does not act in predictable ways.

I know of no mortar-specific data; you will be best served by collecting and recording firing data. Be sure to record wind velocity.

doubleduece · « **Reply #49 on:** June 21, 2007, 05:28:02 PM »

Good job. Looks nice!
What kind of barstock did you end up using for this?

Rickk · « **Reply #50 on:** June 22, 2007, 12:18:35 AM »

I zoned out and forgot that you were not building a golf ball mortar, but rather a 73 cal.

My spreadsheet would indeed work if you can hear it touch down, but keep the charges light as 73 cal is pretty easy to make go a long ways.

Something like 10 grains of 2F would be a good place to start. Really light loads may produce erratic ignition. That is somewhat a function of where your fuse enters the chamber. 10 grains is pretty light but it is much safer to start small and work up.

StealthyBlagga · « **Reply #51 on:** June 22, 2007, 12:15:47 PM »

Quote from: doubleduece on June 21, 2007, 05:28:02 PM

Good job. Looks nice!
What kind of barstock did you end up using for this?

My kids and I built it from scratch, using stuff I had laying around plus some steel remnants bought from a local scrap yard. In total, the steel cost me probably $20 (I had to buy a minimum of 1ft of each size), the engine paint another $10, and I needed to buy a 3/4" drill bit @$20 to bore the barrel (I already had a 1/2" bit for the powder chamber).

We did everything with hand tools, plus a drill press (a lathe would be better, but I don't have one), a TIG welder and - of course - a Dremel

. Because I did not feel confident about drilling a long hole that was true, I stayed with a traditional muzzle-loading mortar design (i.e. a short 2-caliber barrel length with a powder chamber). The drawing below shows the final barrel design I used.

The main manufacturing steps were:

- Chop barrel (2" hot-rolled steel bar stock) to desired length.
- Check the barrel for squareness, then tack weld it upright to a 1/4" plate (to hold the barrel securely in place while it is drilled). Clamp the plate to the drill press.
- Mark center of barrel with a center punch. Drill a pilot hole and confirm concentricity.
- Drill 1/2" hole to the depth of the powder chamber. Lubricate liberally and go slow. Finish with a radiused bit to eliminate stress point in the bottom of the powder chamber.
- Drill 3/4" hole to the depth of the bore. Lubricate liberally and go slow.
- Drill touch hole. Countersink the outside for easy fuse insertion.
- Polish the bore with fine abrasive cloth on a mandrel as needed.
- Remove the barrel from the base plate (grind away the tack welds)
- Cut and file the trunnion rod to mate with the back of the barrel. Weld in place (go slow - avoid overheating the barrel).
- Clean up and paint the barrel assembly.
- Build base with quick release trunion retainers. Drill from the side with 3/4 drill, then chisel out the unwanted wood. Inlet for barrel using a Dremel. Stain and varnish.

Here are some photos of the steps:

Cutting the barrel:

Drilling the bore (note barrel welded to plate, which is clamped to drill press):

Set up to weld the trunnion to the back of the barrel:

Complete barrel assembly before painting:

Overall, I'm pretty happy with the results (I'll be REALLY happy if it holds together when I test fire it). I hope you find this helpful.

Rickk · « **Reply #52 on:** June 22, 2007, 12:26:26 PM »

Aaaaarrrggg... the pain of a hack saw

When a buddy of mine let me use his chop saw I ran to Home Depot and bought one for myself. One of the best thngs I ever bought. If you have a welder, the next thing to get is a chop saw. Father's day has past... maybe time to start leaving hints for Christmas

Back to the barrel, it looks awesome. If I can find a hunka steel that size I might make one for myself

In fact, I just bought a 1" drill bit for my carronade construction... maybe I can use it for somethign else afterwords.

GGaskill · « **Reply #53 on:** June 22, 2007, 12:34:40 PM »

I'll be REALLY happy if it holds together when I test fire it.

As long as you use a reasonable amount of black powder and did at least a half asss welding job (and it looks much better than that), you have nothing to worry about.

StealthyBlagga · « **Reply #54 on:** June 24, 2007, 07:22:26 PM »

Well, it held together with up to 35 grains of FG: Video. Note that the mortar is mounted in an ugly jig that allows the barrel to aim horizontally because I was test firing in a pistol bay and did not want the projectile to escape the berm, plus I was running each shot over a chronograph. If the readings can be believed, I got up to 304fps with the 586 grain musket balls I was using.