The Design, Const. and Shooting of a 9-Inch, "BIG THUMPER", MORTAR, cont.

[seacoastartillery]

    We at Seacoast Artillery would like to extend our heartfelt thanks to Matt for his hard and long work in getting the forums including GBO Mortar and Cannon back to normal.  Thank you, Matt!!  Mike and Tracy

  I thought about this project quite a bit yesterday and I decided that I would need some help with the lathe work.  You see we don’t have a huge steady rest and the OD of the proposed tube is 10.25” in diameter.  Our steady rest will only hold 8” dia. tubes or rounds.  Mike has fast and efficient ways to make end caps for the larger sized tubes, one with a protruding journal for driving via the lathe chuck and the other one has a center drilled center for tailstock  holding via a live-center.  These tools make it so much easier to turn the OD.  I spoke to him and he said,  “You get in there and simplify that bed design and then we will talk”.  He also said, I’m balking at the timber baulks in the bed.  I have a better use for that white oak.  It is needlessly complex because of the small size of the timbers.”  I reminded him that I was using only snap, crackle and pop white oak from our first misadventure with purchasing that very difficult to kiln dry, wood.   

     We searched the country for a supplier of dried white oak in thicknesses over two inches.  We thought we had found a good one in Michigan.  WRONG!!   Anyway, $900 and 5 months later we had our wood delivered.  We hauled it into Mike’s basement where our woodworking shop was.  There were a few minor splits in several of the sticks, but we thought that was normal. WRONG AGAIN!!  So we jointed and planed 3 of the 3X3x40” pcs.  That’s when the Cereal Commercial noises started. The wood in those 3 pcs. started making noticeable noises as it constantly fissured, cracked, bowed, twisted and split.  We learned later that the fellow we hired to cut and dry our wood didn’t have a clue and heated it way beyond what was proper.  The wood was loaded with internal cracks and collapsed cells from too rapid drying.  We had $900 worth of junk wood. 

    So, I began a re-design and came up with another bed of much simpler design and stronger too and trouble-free.  It weighs only 55 pounds too a reduction of 20 pounds over the white oak design.  We can afford to buy grade 8 bolts too as they are only 3.50” long in this design.     This new bed will be ugly looking but, who cares!  It will be buried just like the old wood design. We still need a fusing or quill idea, as the chamber piece will be 6 to 8” underground.  I dislike business clichés, but we really need some ”out of the container”  thinking here.  We need ideas.  See and enlarge the drawing below.   

Tracy and Mike



The new drawing shows changes to the bed bringing it forward, mindful of the KISS principle and leaving behind the needlessly complex oak timbers.




Mike was correct, he did have some 8" Channel Iron in his backyard, 24" long.  It's buried in snow now, but this is Colorado, 3 days from now the snow will be gone and the channel available.



 

[GGaskill]

Is that bed is going to be one piece of 8" channel crossed over one other piece or one piece crossed over three pieces welded (or otherwise connected) together in a 24" x 24" configuration?  And I think you should have the closed side of the channel facing the dirt so it doesn't embed itself.

Assuming you are planning to load with loose powder, this buried design is crying out for electrical ignition.  I have some nichrome wire I can send you if you don't have any.

[Cannon Cocker]

This is an idea for getting fire to the powder in a buried powder chamber.  Bear with me on this first part.  It helps expain the concept better.

My Whitworth is designed to use only friction primers.  It shoots fire down a 4 inch axial vent then through a 50 thousandths hole in the back of a shell casing and never misfires.  However, in order to be able to watch the target impact in my spotting scope (which I can't do while pulling a lanyard), I use a "fused primer".  I make these by inserting cannon fuse about a half an inch into a 5/32" brass tube and then crimp it with a hammer.  I then fill up the open end of the tube with Fg and tamp it down lightly with something about the diameter of coat hanger wire.  The powder grains compress enough so that they won't fall out, but I put a piece of masking tape over the end just in case.  Just before firing the gun I pull off the tape and insert the primer in the vent.  The crimp or hammer flattened part of the primer is larger than the vent so when I press it in it sticks tight.  This is important because it gives more force to the flame than if the primer were loose because it would lose some of its energy ejecting itself upon ignition.
 
 One of the above mentioned fused brass primers is inserted into a holder which is attached to (and and directs flame down) a thin copper tube which leads directly to the vent of the chamber.  The copper tubing would be held up and out of the earth that is packed around the base of the gun leaving the holder available for primer insertion.  I have no doubt that there would be sufficient flame, and I think it could be used possibly 20 times before needing to be cleaned, which could be done with pipe cleaners. 

[seacoastartillery]

   II have looked at the problem of lighting a powder charge in a mortar which has a buried powder chamber from all different angles except one.  I recall one of those things my father always told me,  "Face your problems squarely, son, face your problems squarely."  So, I thought, how would I go about doing that here?  If it's "your problem", what does that mean?  It means, I believe, that you will provide the answer and it must be revolutionary, different and probably not accepted by your circle of friends or relatives.  I pondered all that some more and last night, I had an epiphany.  An answer came to me suddenly.  I sat bolt upright in bed and leaned over to the pen and scratch pad on my night stand and wrote:   "Quill goes in axially" by the light of my cell phone. 
 
      Since you can't get access from the bottom, because it's deeply buried, I must have been thinking top of the powder chamber.  Then I remember the key that jolted me awake.  It was an image of a continuous axis coincident with the bore axis leading into the chamber top and this image was green and had a fabric look to it with a lacquer coating, just like a fuse.  If that is the case and I'm sure it was, then the fuse went directly through the center of the projectile too, along it's central axis. 
 
      Caboose Hobbies came to mind as a source of 7/32" ID brass or aluminum tube.  They have any size you are thinking of and only about half are on the online inventory.  Back to Broomfield again with the goods, I headed to the shop where the popcorn tins and all the tools were.  The top would be wide open to receive the concrete, but the bottom would need a hole punched to accept the .015" wall, 1/4" OD brass tube.  Found a 5/16" drill rod,cut 4 inches off, turned 3/8" of it to .260" dia., faced it and c'sunk it out to the edge with a #3 centerdrill.  I had my punch, now I needed a piece of 2x4 for can support, no luck, so I grabbed one of Mike's 2x2s for target backer support.  He winds about 18" of soft iron wire around the end to keep them from shattering as the pointy ends are driven into the prairie hard pan.
 
     A photo shows how the tube and tin are configured.  Tomorrow I will try one out to see if we can communicate fire along the 10" brass tube to a small charge under the tin, (in the chamber so to speak).  The quill is an old one made in 2011, but should work OK.  We will see.  15" of quill should go up in 1/100 second.

     This is a fused quill inside a 10" brass tube lying along the projectile axis.  The tube, at the bottom, only sticks out 1/4", not enough to puncture the 8 oz. powder cartridge, six wraps of aluminum foil. It is epoxied at the bottom and held at the top with iron wire. 





 
 
 
t]

 
Is that bed is going to be one piece of 8" channel crossed over one other piece or one piece crossed over three pieces welded (or otherwise connected) together in a 24" x 24" configuration?  And I think you should have the closed side of the channel facing the dirt so it doesn't embed itself.

 Assuming you are planning to load with loose powder, this buried design is crying out for electrical ignition.  I have some nichrome wire I can send you if you don't have any.
 

 
 
      The bed is to be two pcs. of 8" x 24" Channel Iron in a cross config.  The hollow side is down so the flat is toward the Chamber Bottom and bolted solidly through both Channel pcs.  I did forget the 1/2" x 1/2" welded, anti spread bars, 8" long, which are welded to the bottom Channel on it's broad, flat side adjacent to the ends of the two sides of the top channel.  These keep the ends from spreading out upon recoil of the piece.





 
      The loose powder was such a pain to load in the Coffee can mortar, that we are sticking with aluminum foil cartridges, however I would love to try electric ignition on a few overload experiments we have planned for our 1" sleeves we are making.  PM sent.  Thank you, George.
















 
 
 

 This is an idea for getting fire to the powder in a buried powder chamber.  Bear with me on this first part.  It helps explain the concept better.


 My Whitworth is designed to use only friction primers.  It shoots fire down a 4 inch axial vent then through a 50 thousandths hole in the back of a shell casing and never misfires.  However, in order to be able to watch the target impact in my spotting scope (which I can't do while pulling a lanyard), I use a "fused primer".  I make these by inserting cannon fuse about a half an inch into a 5/32" brass tube and then crimp it with a hammer.  I then fill up the open end of the tube with Fg and tamp it down lightly with something about the diameter of coat hanger wire.  The powder grains compress enough so that they won't fall out, but I put a piece of masking tape over the end just in case.  Just before firing the gun I pull off the tape and insert the primer in the vent.  The crimp or hammer flattened part of the primer is larger than the vent so when I press it in it sticks tight.  This is important because it gives more force to the flame than if the primer were loose because it would lose some of its energy ejecting itself upon ignition.

 
  One of the above mentioned fused brass primers is inserted into a holder which is attached to (and and directs flame down) a thin copper tube which leads directly to the vent of the chamber.  The copper tubing would be held up and out of the earth that is packed around the base of the gun leaving the holder available for primer insertion.  I have no doubt that there would be sufficient flame, and I think it could be used possibly 20 times before needing to be cleaned, which could be done with pipe cleaners. 

     I'm quite confident that it would work for our partially buried mortar too.  We have already logged your text and pics to try this effective equipment as an alternative to our central quill design, should the need occur.  We have a 3.2 inch half scale field gun in mind, maybe the method would work well for that long axial vent through the DeBange breech block spindle on that gun.     Thank you for documenting this method so thoroughly, Mike.

Tracy

[Cannon Cocker]

   I    We have a 3.2 inch half scale field gun in mind, maybe the method would work well for that long axial vent through the DeBange breech block spindle on that gun.     Thank you for documenting this method so thoroughly, Mike.

Tracy

If you fill up that copper central tube with powder it should work, but if you were to use one of my fused "friction" primers, it will shoot a flame all the way down and be easier than filling that whole tube like a quill every time you want to shoot it.  I use the 5/32" tube for the primers and they telescope perfectly with the 3/16" tube, so if you make the central tube out of 3/16" it will fit perfectly.  As I mentioned, the irregular crimp at the fuse area makes it wedge and stick which really gives a good punch to the flame.  You could make the primers ahead of time, and just stick them in for every shot.

[seacoastartillery]

     Cannon Cocker,  Perhaps I led you to believe that I was going to use one of those filled with powder quills which burn like energetic railroad flares!  No, not that kind at all.  The quills we make are hollow .187" diameter paper straws, hollow, except for a piece of double sided celephane tape, .210" wide which has been run through a bowl of 4Fg black powder.  Being coated on both sides with the fine grain powder, it will not stick to the paper straw as you gently feed it in pinching it slightly as it goes in.  These burn instantly, like a super long firecracker and they are excellent communicators of a hot flame at the far end.  Mike and I have never had one fail to set the charge off.  We use fused quills so we can step back a little or a lot depending on the size of the cannon we are firing.

     However, you are most certainly correct, your type of fused friction primers would work and I bet would work very well from your description of their forceful flame.  I will make some and we will experiment with them after we get this big mortar built.  Thanks once again, Cannon Cocker for the excellent description and sketch documents too.

Tracy

[GGaskill]

PM sent.

Not sure PM's are working yet.  Try an email.

[Victor3]

Think Christmas tree stand, the ol' tried & true one sawn from a single 2x4 (with some modification for steel channel of course).

[Mike Scott]

The pyrotechnic mortar shells have a longer fuse that runs from the base of the charge up the to the mouth of the barrel.  Would this work on a black powder mortar?  Embed one end of the fuse in a foil wrapped charge and let the rest "hang out".     

[seacoastartillery]

    Hate to admit it, George, but with guests in the house this weekend, I just forgot to send it.


     Victor3,   Yes it does kinda look like one of those.  I remember for years and years we had a live tree and the old stand, circa 1946, had a heavy duty steel ring with three 5/16" threaded bolts to hold the tree and supported by three heavy legs riveted to it.  Forest green was the color with a tulip shaped water reservoir painted fire engine red.

     Think KISS principle.  Use what you have and bolt together.

The pyrotechnic mortar shells have a longer fuse that runs from the base of the charge up the to the mouth of the barrel. Would this work on a black powder mortar?  Embed one end of the fuse in a foil wrapped charge and let the rest "hang out". 

     I think this use of fuse would work, Mike, but with the bottom edges of the 50 pound projectile being only .060" you would have to lower the heavy projectile very carefully to avoid cutting the fuse.  The windage is .125" all around.  The main problem is with the lengthy delay between lighting the fuse end and the KA-BOOM.  Believe it or not, we always check for light planes flying in the area before we will commit to firing.  Short fuses attached to quick acting quills, ( a type of quick match) are the only safe way to go, other than friction primers or electric ignition.

     Although my grandson and I worked almost all day on his Pinewood Derby car for the big Cub Scout event coming up soon, we did take a break and headed to a remote location to test out the communication of fire capability of a 15" quill through one of my popcorn tins which will become a heavy duty projectile for the 9" mortar when filled with aggregate concrete.  The lessons of keep your distance, know exactly where you are going to stand to safely observe, etc. were taught and the test went off without a hitch as I knew it would.  See the clip below:



   
     


     

[Spuddy]

I like your apprentice's laugh.  It reminds me of one I used to hear around home.  The one I used to hear has now gotten deeper.  Memories.

[Cannon Cocker]

     Cannon Cocker,  Perhaps I led you to believe that I was going to use one of those filled with powder quills which burn like energetic railroad flares! 

Yes.  I guess I did think it was going to be one of those.  Sorry to insult your intelligence.  The hollow powder lined straws work great (kind of like the quickmatch design).

All the talk about Christmas tree stands gave me an idea for a mortar (see picture).  And before everyone comes down on me like a volley of 13" mortar shells, yes,  it's a joke.  No one should ever consider this idea safe.  Do not try this at home, the office, the mall, or anywhere else on planet earth.  Besides....I might incur greater damage from the wife when all the sugar water starts to leak out of the vent I would have to drill.