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long range ammo MiniBoy Mark I

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: HunterT » Sun Oct 02, 2011 10:57 pm

Mr.Tallahassee wrote:That should do the trick! Pick up the frequency on a handheld radio and there it is.


It probably will do the trick, but my concern is whether or not it will be able to withstand the shock of the projectile hitting the ground.
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Unread postAuthor: MrCrowley » Sun Oct 02, 2011 11:01 pm

It might just fit inside the projectile. How much are those circuits anyway?
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 02, 2011 11:15 pm

Fnord wrote:I think there is a more elegant solution to projectile recovery.


HAHAHAHA excellent!
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Unread postAuthor: Mr.Tallahassee » Sun Oct 02, 2011 11:58 pm

You would most likely have to build it yourself. You can probably find schematics for a surface mount AM transmitter. That particular one was actually built by Oak Ridge National Laboratories and has a range of 3 kilometers. :shock: If you wanted them to produce another for you it would probably cost an arm and a leg more than what Miniboy is worth in hours and material price.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 03, 2011 12:01 am

Mr.Tallahassee wrote:You would most likely have to build it yourself. You can probably find schematics for a surface mount AM transmitter.


Have a look at the long range thread, these options were discussed buy cost became an issue.

As to the firing angle issue, I had mentioned it in this thread as well:

Some notes on optimised projectiles and range in the real world, courtesy of fr frog talking about the M829 APFSDS round:

Lets see now -- KE (ft lbs) = (W * V²) / 450436. That gives us (65,870 * 5480 * 5480) / 450436 which boils down to (hold on to your hats!) 4,391,500 foot pounds (that's right 4.3 MILLION ft lbs). Sectional Density = W (in pounds)/D². That gives us 9.41 / .6 * .6 which equals 8.4. (That's eight point four--and you thought your 220gr .30 cal bullet had high sectional density at .343 (that's "point" 343.) The newer M829A3 round throws a 22.2 pound dart at 5200 f/s for 9.2 MILLION ft/lb.

As an interesting side note, when fired at 55 degree elevation, the A2 will travel 113,111 meters (123,630 yards or roughly 70 miles) and reach a height of 44,073 meters (48,171 yards or almost 27 miles). You are NOT safe if someone aims one of these at you. The accuracy of the dart is sub-MOA and the stated effective range is about 3000 meters (3270 yards). However, first round killing hits have been obtained out to about 6000 meters (6540 yards).

Sharp-eyed readers may note the 55 degree elevation for the maximum range of this projectile. While spin stabilized cylindrical projectiles reach their maximum range in air at angles of between 25 and 35 degrees (45 degrees in a vacuum) the "dart is fin stabilized and not spun (the 120 mm gun is a smooth bore) and this gives it its maximum range at 55 degrees elevation--the fins keeping it point first through out its trajectory and providing some lift. Click here for a discussion of projectiles fired at extreme elevations.


Note also the discrepancy between optimum launch angles between spin and fin stabilised projectiles.
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Unread postAuthor: ramses » Mon Oct 03, 2011 7:02 pm

DYI wrote:Jack's reference measured from the horizontal. An M892A2 round has a high enough muzzle speed and low enough drag that it goes high enough for the reduced air density to make a difference. A similarly extreme example of the effect can be seen in the Paris Gun of WW1.

Your friend's dad is not an engineer if he's incapable of such basic dimensional analysis, or the intuitive understanding of low-altitude trajectories. I suggest euthanasia.



AAh, I failed to consider reduced air density. :oops: :oops:
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Unread postAuthor: MrCrowley » Mon Oct 03, 2011 9:18 pm

I've had a long day at uni today and during most long days at uni my mind frequently drifts back to the MiniBoy and the problem of locating him.

Have we discussed a FM transmitter (assuming I can make one cheap enough and small enough) that fits inside MiniBoy with an antenna coiled up inside that is attached to the tail and on impact, the tail comes loose and stays on the surface while the projectile is buried?

There are a number of problems with this that I immediately recognise:
1: buying/making the transmitter
2: the survival of the components (some epoxy should fix this)
3: the tail detaching prematurely, not at all or being dragged down slightly before coming loose
4: the antenna wire breaking
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Unread postAuthor: warhead052 » Mon Oct 03, 2011 9:24 pm

Feel free to edit this, but something along the lines of what model rockets use to deploy parachutes. Except you don't have to destroy the miniboy, just make it easy for the tail to detach on impact or something, that way the antenna stays above ground.
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Unread postAuthor: MrCrowley » Mon Oct 03, 2011 9:51 pm

If I went with the route I'd drop the transmitter all together and just have MiniBoy eject some sort of streamer to sit on the surface. The problem with this is the timing of any 'motor' or ejecting (such as pressure via dry ice) method. Model rockets deploy the 'chute when the motor stops. I don't really want a motor to be ignited inside the MiniBoy during flight.

Your post has given me a few things to think about during my Geology (*sigh*) lecture now so, thanks :P
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Unread postAuthor: warhead052 » Mon Oct 03, 2011 10:18 pm

:D Glad I could help. Possibly a blinking led, on the end of a streamer with a buzzer?
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Unread postAuthor: MrCrowley » Mon Oct 03, 2011 11:40 pm

Na, probably just a bright coloured, long streamer tied by fishing line to the projectile body. If we search using an ATV, a bright streamer should be all that is needed to be located.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 03, 2011 11:51 pm

I think we're past the stage of incorporating recovery systems now that the mini-boy is solidly built, this should have been included in the design stage :P

I say pack it with fine power and have at it.
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Unread postAuthor: MrCrowley » Tue Oct 04, 2011 1:22 am

Godf*ckingdammit, my epoxy and resin is long expired, had only noticed it recently in the garage but my brother says he got it 2 years or so ago.

That's another $40 (assuming 1 litre is even enough for 200g/kg, 2m^2) on top of the $22 on the fibreglass cloth itself. Perhaps I should start looking for a replacement barrel.

Edit: Seems as if I'll have to try and find a pipe that can either sleeve the ABS barrel or one that is about 60mm O.D. with 5mm wall thickness. They don't seem to make much pipe in diameters between 50mm O.D. and 60mm O.D.

Still have to find a place to cut to length as well...hmm
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Unread postAuthor: Fnord » Tue Oct 04, 2011 4:54 am

Have you tried mixing up a small batch of resin to test? It might still be fine.
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Unread postAuthor: MrCrowley » Tue Oct 04, 2011 4:57 am

I'll give that a go tomorrow. I did some reading around and everyone basically says it's useless and a shelf life of a year requires suitable temperatures (we don't get extremes where I live which helps, apparently).
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