Improving Accuracy of "Tin Can" Mortar Projectiles

[RocklockI]

Mike and Tracy, glad you love the picture, if i find any test info, i'll pass it along. I would think that if you added the feature of the Hale War Rocket to it, might make for a very interesting combo. I always enjoy watching these experiments, and can't wait to see how they turn out.

Lance this very day I was talking to Tracy and some ideas and oddly enough when I explianed an idea of 'some' rocketry with my projo .........He said "yea sounds good but what if it 's flipping and comes straight back at us ."

Tracy still has his moments wisdom , of course we'll proly still do it but we'll be sure and hide under his big chevy 

I dont need any more "comebacks" .  whether it boomrangs or richoctes it's not good .

Gary

 

[GGaskill]

Next on my list of experiments is the longer 16 oz cans with a lead head.  I have seen only one 12 oz can stop tumbling and fly heavy end forward and that was at least 3/4 of the way to impact. 

Some of you serious beer drinkers start saving the 16 oz cans for this.     

[RocklockI]

24 oz PBR's ? Havnt measured the OD . At the Mont. shoot the first shot out of seacoast big mortar that water jug went out striaght and true arched over nose fist and dove into the ground . After that none flew straight they just went woop woop woop then stop .

You know the aluminium PBR cans may extend my fins better than a steel can .

Maybe have to use a 16oz ?
Gary

ETA My Dad who was in Pattons 3rd as a watercooled machine gunner spoke very highly of German mortar crews .
There would be one long ,one short and one bullseye . Also he told me of a few GI's around a campfire ingnored everyones warnings when one went long .....then short .....they were killed by the third round . This was when I was a kid ,then I see the same thing on some movie of late .

Also he told me of capturing a german who'd shot a medic while he was tending to a german wounded .......like in "Privite Private Ryan"  only this guy endded up with a .45 in his mouth ....It made a hell of a mess is all he said about that .

[Cannoneer]

Alright, now everything is as it should be in BPMC-land! Victor has returned... Welcome back buddy!

 And I'm here with a "can-do" attitude.

 Now then..... Let's have a look at M&T's design. Hmmmm.....

Thanks for your CANdor ; I’ll never point a comedic FINger at any of your theoretical engineering discussions again. You do believe me don’t ya?

[dominick]

From a lurker,

My thought was to use common mouse trap springs to extend the fins.  Cheap and expendible, once the design was finalized. Would need a bit of brazing and all that.  Or perhaps a bit of JB Weld. Install the spring/fin assembly in the end of a cement-filled tin can somehow, stick it down the barrel backwards with the fins tucked in tight (carefully, to save your fingers), light the fuse and let it fly like a shuttlecock.  

My other thought was that fins that extended beyond the diameter of the round may not be necessary.  Older military mortar rounds fit the barrel without deployable fins.  Make an X out of 1/16 inch or so sheet aluminum, sink this into the cement-filled tin can as the cement is hardening, and there you go.  I think the fins would even survive if the round was loaded fin first.

I fire an old Sculler Lyle Gun sometimes, and a couple of golf ball mortars a lot.  Fins on a golf ball?  Hmmm.

Regards,

benzon

If all this is old news for you folks from previous threads, I apologize.

Question,  If the fins were left in flush with the body of the projectile, would the rear portion of the body need to taper into the fin [similar to a modern mortar round]  or could it be squared at 90 degrees as the can is?  How about the leading edge of the fins against the back portion of the can and flush with the OD?  Would there be trailing edge turbulence that would negate the effectiveness of the fins?  Drawing below.

[seacoastartillery]

     Dominic,   I was wondering about that too.  Would this idea work if you put those, less than bore dia. fins, out, away from the projectile- body, on the end of a light-weight shaft, as they did on the Sims-Dudley Dynamite Gun Projectile?

Just wondering,

Tracy

[Victor3]

 I have a thick hide, Mr. J. You may say anything you want whenever you want, as my skull is even thicker. 

 M&T - My rocket comment was of course meant as a small dig about the complexity of your design compared to my tin toy. Pay no attention to the man behind the bronze curtain; he aint been right since he caught a whiff of that de-gassing smoke. 

 If I'm not forced into to making rocket parts this weekend, I'll do a mockup of my design and throw it at the park to see what it looks like in flight.

[Ex 49'er]

Blackpowder lawn darts, eh?

[dan610324]

you are discussing  MORTAR  projectiles ,  OR  ??

the usual antique mortar is most often between 2-3 calibers in bore depth ,  OR ??

so I guess that many of your ideas is a bit difficult to use in a mortar
but in a howie maybe

[Double D]

Dan brings up a good point.  

We always encourage everyone to follow the safe guidlines as laid out by N-SSA and AAA.  http://www.americanartillery.org/aaa/mrt.html


N-SSA speaks only to original guns projectil types, AAA speaks to alternatives.  AAA say Barrel length shall not exceed 2 times the projectile length, while projectile length shall not exceed 3 times the bore diameter.

[jeeper1]

I believe you people are over thinking the stability problem.
I have been mulling over different ideas for stabilizing the cans and came up with a simple idea. Why not just fill the cans half full with whatever weight you want and then cut wide slots running longitudinally from the weight to the base stopping short so there is a ring. By removing 50% to 66% of the metal you should enough room for the air to flow through and keep the can from tumbling.
The idea reminded me of an episode from the series "Junkyard wars" where the contestants build rockets to carry Ostrich eggs to a minimum required altitude and land without breaking the egg. One of the teams made a cone shaped rocket with triangular openings for air flow. It worked fine until the air pressure collapsed the cone due to a lack of reinforcing ring around the base.   

[Cannoneer]

I have a thick hide, Mr. J. You may say anything you want whenever you want, as my skull is even thicker. 

Victor,
You're simply aces in my book! When I think of the trust that's involved in your giving me carte blanche to just fire at will, well, I don't mind admitting that I got a little moisture on the eyeballs.
To prove my goodwill, I make this humble offering of what may well be the shape that put the A in aerodynamics. Now, this design is definitely post Civil War and certainly pre (APFSDSP) armour-piercing fin-stabilized discarding sabot projectile, but right now I can't recall what its acronym (FGR) stands for. FGR


 

[GGaskill]

... but right now I can't recall what its acronym (FGR) stands for.

Flash Gordon Rocket??   

[dan610324]

3X2=6  then I call it a howie if it got a 6 cal deep bore
I guess the mountain howitzer got somewhere between 5 and 6 cal deep bore

why not stop using cans as projos and use spherical projos instead
then I guess most of the problems is gone

now when one of our sponsors can make custom made molds it doesnt matter what caliber you got

[dominick]

    Dominic,   I was wondering about that too.  Would this idea work if you put those, less than bore dia. fins, out, away from the projectile- body, on the end of a light-weight shaft, as they did on the Sims-Dudley Dynamite Gun Projectile?

Just wondering,

Tracy

I think flush fins would probably work. How far back is the open question.  The dynamite gun use compressed air to launch the round at a lower velocity [600 FPS].  Placing the fins against the back of the can with a drop away sabot disc should make it stronger to withstand the black powder charge.  

Dan,
This design is for a cannon or Lyle gun.  It would be too long for a mortar.

[lance]

Cone shaped cans, years ago while out hunting, i found a pile of cone shaped beer cans, shoot, i thought they were brake fluid cans

[JeffG]

I prefer the Rotweil-Brenneke approach.  use a taller can, fill the back 2/3 with great stuff foam, the front 1/3 with concrete.  the light rear does the shuttle-cock thing.....

[seacoastartillery]

     I'm getting the experimental auto-deploying shuttle-cock projectile finished up soon so we will be ready for a test firing salute at Noon on Saturday to 'Ring in The Spring' but good!!  There is at least 7 inches of "global warming" on the ground by now, so I don't think we will be digging the trailer and Paixhans Mortar out.  The drift in front of it looks like it's 4 to 5 feet tall.  

     I think our simple Coehorn Mortar with the EX-Asparagus-1, Super Parabolic Landing Abapical Tentamen, (S.P.L.A.T.) projectile will be fired in the valley in front of the High Speed Camera so we can have a fair chance of seeing the deployment.  Pictures of this highly sophisticated near-space vehicle will be posted pre-launch so it can be seen in all it's glory!   Also before the possible obliteration upon launch or Splattering upon meeting Tera-Firma.            Abapical.......at the lowest point.        Tentamen.......Experimental item.

Til tomorrow,

Tracy and Mike

[lance]

With all the snow on Tera-Firma, you guys might need a metal detector, to recover any space vehicle parts.

[seacoastartillery]

     Sometimes I'm a bit stubborn, but my original "Flailing Fin' guidance system will be amusing to launch this weekend.  I have been building it a little each night and I assembled it this evening.  Mike says it may be more dangerous to the mortar crew than the 100 yard target.  We will see.  I will post half the build photos tonight and half tomorrow as it's getting late.  Mike has had nothing to do with this thing and is openly betting that an asparagus can with a simple weight at one end will beat it hands down.  Since I did all the turning, milling and drilling, you can fault me if it fails to deploy or flies apart upon launch, and not Tracy AND Mike this time!  We will charge our camera's batteries and try very hard to get a good 1,200 frames per second SLO-MO movie of the launch.  Might be interesting.

Tracy


I gave up on lead and used some scraps of steel for the nose weight.  1.5" seemed to be plenty and provides 75% of the weight in about 25% of the volume.




In projects like this it's good to function check critical fit items as you go.  The composite steel slug is 2.545" dia. and the can fits snugly.




I am turning the annular groove here which is the seat for all those machined aluminum guidance vanes.  The .220" dia. post which guides the sliding steel release collar sticks out toward you in this view.




Yes, I use the Digital Read Out on the lathe, but it never hurts to have a quality function check step in your machining process.  Here I use a vane to see if the annular groove is wide enough before I remove this piece-part from the lathe.




Even on a relatively simple project like this one, you almost always have to make special tools that are not in your tool box.  Here it's a .065" drill extension so that tap drill holes can be drilled immediately adjacent to a journal on the vane assy. base.




Drilling those tiny holes for the screw eyes that will hold the bottom end of the vane deployment springs.  More pics on Thursday.

[KABAR2]

I am waiting to see the end result, this is going to be interesting...... my only question is
will one need a NASA type budget to mass produce these?

[seacoastartillery]

      It's Thursday and 60 deg. F for the high and lots of sun today.  I have my grandson to watch today, so while he's eating his breakfast, I figured I would post those other pics I promised.  I forgot to show how I milled each of the 12 aluminum vanes, but it wasn't much, just two .0625" holes at right angles to each other 1.0" and 1.3" from one end of the 5" long, .3125" dia., rod.  One hole is for the dog-leg shaped wire hook which holds the sliding release collar and the other is for the lower end of the deployment springs.  At the other end , I milled a 3 deg., 2.0" long chamfer, to present a flat surface to the air as this missile speeds along.  Looks like the weather will cooperate on Sunday for some testing; hope so.

Today J and I are going to the pond to look for fox tracks.  Last time he learned that particularly pleasing sound that a Red-Winged Black Bird makes and what a thrush looks like.

Tracy

Here are the parts we have so far.  Each needs a 1/4" hole so they can be assembled together.




The major parts are aligned by a 1/4" steel rod.  Everything you see was then epoxied together.




The sliding collar is set to .40" above the 'collar limit surface' of the vane assy. base.  At this height, the vane hooks have .25" engagement with the collar's I.D.  All the vanes with their hooks and springs are connected to the screw eyes on the base.




In this top view, you can see how each hook engages the I.D. of the steel, sliding collar after each vane's deployment spring is fully extended.  This view shows the undeployed, launch position of the spring-loaded vanes.  




Assembly of the can and vane sub-assys.  The masking tape makes for a snug, friction fit.




Assembly is 66% complete.  Final assy. will be done at the test range and will allow only 2.5" of the vanes to protrude above the projectile's steel skin.




Until Sunday!

[carronader]

Gloriously Insane ! put this man on medication.    looking forward to pics and result.

[Spuddy]

Ahhh red winged black birds and peepers are my two favorite sounds.  I close my eyes and I am 7 again falling asleep with the windows open.  I also must comment on the crayons and the high tech guidance system in the same shot.  Very poetic.

[RocklockI]

Between you ,Bert and Errine , what can go wrong ?

[KABAR2]

M&T,

There is some impressive amount of engineering going into this....... I guess the only thing left
is installing a gyrocompass and electronic micro stabalizers to keep the vains correctly alinged........

perhaps GPS tracking? .........


Allen <><

[seacoastartillery]

     KABAR2,     Having worked on quite a few Nasa contract rocket and Space Schuttle parts, I think you probably would need a 'cost-plus' contract to produce these guided mortar rounds properly.  As for the gyroscopic stabilizer, Edmund Scientific comes to mind.  If I did have one I would mount it with the axis perpendicular to the round's central axis.  How would you guys mount it??

     Gary,   Don't tell Allen this, but all the 'engineering' on this project was done by my 3 year old grandson and Bert and Ernie are on the cover of one of his reference books.  I have to agree with Spuddy.  It was great to grow up in the country with those wildlife sounds which were soothing to your soul, not jarring like a computer game.  

     Glad you like it, Carronader.  However, just about all our projects have a hint of whimsy in them, or they outright defy gravity and this one is no different.  In fact, I remember our CPA and business consultant commenting on our business plan.  "But it's based on a vapor; there is nothing solid here, at all.  It's a cotton thread in the wind.  The nitch you fellows want to fill is non-existent!"  This company we created, by far our biggest project, succeeds only because our enthusiasm has never waned and our optimism has no bounds.  

     Tracy

[Double D]

Let me add a bit of whimsical information here!!! 

...Barrel length shall not exceed 2 times the projectile length, while projectile length shall not exceed 3 times the bore diameter.

[GGaskill]

This is a project to improve the flight of beer can projectiles, not period shell.   

[Double D]

Thinking back to my City Cop-Deputy Sheriff days and some of the bar fight calls I responded to, I think it might be hard to improve on the trajectory some of those drunk fishermen and loggers were able to achieve....I recall a perfectly round hole in the windshield  and an unbroken beer bottle sitting on the front seat of my SGt's car. No fins on that bottle.