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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: Insomniac » Fri May 13, 2011 9:10 pm

The only improvement I could think of, would be to add something to help aerodynamically force the petals apart when firing it as a seperating sabot.

Something like the front of this sabot...

Image

Now, I'm not familiar with these rounds, so I don't know if sabot seperation is caused by some kind of triggered charge, or simple aerodynamic forces... But it looks like the shape of the sabot is designed to allow the airflow to pull it away from the projectile cleanly.
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I wonder how much deeper the ocean would be without sponges.
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Unread postAuthor: Gaderelguitarist » Fri May 13, 2011 9:12 pm

I would paddle out in my one sheet boat halfway across the world to help find it :D

So that ring can ultimately change the way the sabot behaves, eh? Very neat.
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Unread postAuthor: LeMaudit » Fri May 13, 2011 9:59 pm

something to help aerodynamically force the petals apart


It was my first idea too, but after some thinking and taking into account some KISS arguments :-) I finally agreed that it made little sense; the material UHMW is so slippery that there's really no friction to release.
If the projectile had been hold in the sabot with some pins or grabbing points, maybe it would have been necessary to quickly free those pins. For that particular shape, I think it's fine like that. (but if it WAS necessary after all, I want to make it clear that it's all dewey1's fault :angel9: )

Now come experiment time! MrCrowley just need to find one of those cheap 10000 frames/s camera :lol:


I would paddle out in my one sheet boat halfway across the world to help find it


:lol:

So that ring can ultimately change the way the sabot behaves, eh? Very neat.


The ring and the large washer, yes. Too lazy to make two sabots, I know :D
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Unread postAuthor: jackssmirkingrevenge » Sat May 14, 2011 1:23 am

It's simply too much :-/

What we need to do is get folks like Mike and Pete on board to churn out these things by the thousand on their CNC slave army, that way it wouldn't be so unique and someone would actually fire it...

MrC, I don't think you realise the weight on your shoulders the minute you load this think into a barrel!

fortunately dewey1 and JSR were there to KISS me...


I don't mind being part of a projectile designing brotherhood, but that's a step too far :D
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Unread postAuthor: dewey-1 » Sat May 14, 2011 7:39 am

LeMaudit wrote: fortunately dewey1 and JSR were there to KISS me...

A little 4 play goes a long way! To bad it had to take two of us, one on each side to convince you! :lol:

Looks fantastic as all your projects do! :D
Any plans to reduce the overall weight? You need to remove another 6 grams to be the same weight as my proposal. :lol:

The sabot is for MiniBoy and not FatBoy! :D

MrCrowley; Make sure to add weight to nose end such that the balancing point of MiniBoy is as shown here. About 32 mm maximum from nose tip.
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Unread postAuthor: Fnord » Sat May 14, 2011 12:11 pm

(I did not read every single post on every single page so forgive me if I missed or assumed something wrong)

Might I advise painting the sabot bright orange/green? White UHMWPE on sand is impossible to see at a distance.

Also, this shot should be done on a cool, overcast day, sometime after it rains if possible. When that thing burrows into the beach it's going to leave a trench of still-wet overturned sand. This won't be too hard to spot as it's darker than everything else, but in the sun it won't last more than a few minutes.
If you had two or three people on atv's that could take off down the beach the chances would be in your favor.

Also, it would be nice to get a decent range calc done first, so you at least have a rough idea of the impact zone.
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Unread postAuthor: LeMaudit » Sat May 14, 2011 12:32 pm

Any plans to reduce the overall weight?


Nah. I'm afraid that the thing would broke under too much stress, or deform enough to make it unusable. I wish the sabot could sustain at least a few launch. What are a few grams in life anyway? Seriously, I can thin parts, but only for a few grams. I'm not sure it worth it. And I don't know how to be sure of that really. Someone?


You need to remove another 6 grams to be the same weight as my proposal. The sabot is for MiniBoy and not FatBoy!


bla bla bla wont work wont work... :tongue:



Might I advise painting the sabot bright orange/green? White UHMWPE on sand is impossible to see at a distance.


I don't think painting UHMW is possible; maybe some colored adhesive tape on the side of the petals will do? Even around the MiniBoy, a few stripes of alternate colors would not do wrong (unless it's fully buried in sand of course)


Also, this shot should be done on a cool, overcast day, sometime after it rains if possible


Weather will be on our side... winter is starting in NZ I think :-D


Also, it would be nice to get a decent range calc done first, so you at least have a rough idea of the impact zone.


If I manage to make a few dummy ammo, maybe this will make it possible for a few firing tests. I'm not sure how to do that quickly yet... thinking right now about it... :scratch: I do have the appropriate wood dowel to cut...
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Unread postAuthor: jackssmirkingrevenge » Sat May 14, 2011 2:37 pm

LeMaudit wrote:Seriously, I can thin parts, but only for a few grams. I'm not sure it worth it. And I don't know how to be sure of that really. Someone?


Every gram less on the sabot means more fps and more range. What happened to all the holes you were meant to drill in it ;)
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Unread postAuthor: Moonbogg » Sat May 14, 2011 2:43 pm

Could turn a polypropylene sabot with a cup in the front and cut it in 3 sections.
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Unread postAuthor: LeMaudit » Sat May 14, 2011 2:45 pm

Every gram less on the sabot means more fps and more range.


I know that... but will it be significant for say, 3% of the sabot mass?

What happened to all the holes you were meant to drill in it Wink


There's much more cuts and grooves than the original design :tongue1:

But if a few % is significant, I'll shave and drill the beast :D (oops... can I say that?)
Give me some numbers someone! :lol:

[edit] sabot weight as posted before is 49.6 grams for the separating sabot, 54 grams for the cup sabot.
MiniBoy is 68.4 grams empty. It could be filled I guess with 50 to 70 grams of additional weight
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Last edited by LeMaudit on Sat May 14, 2011 4:02 pm, edited 2 times in total.
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Unread postAuthor: jackssmirkingrevenge » Sat May 14, 2011 3:40 pm

LeMaudit wrote:Give me some numbers someone! :lol:


MrC can model it in HGDT, give him a range of sabot weights.

Incidentally, I wonder if Sir Barnes Neville Wallis would be proud :)
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Unread postAuthor: MrCrowley » Sat May 14, 2011 9:03 pm

Fnord wrote:Also, this shot should be done on a cool, overcast day, sometime after it rains if possible. When that thing burrows into the beach it's going to leave a trench of still-wet overturned sand. This won't be too hard to spot as it's darker than everything else, but in the sun it won't last more than a few minutes.

As LeMaudit noted, Winter is pretty much around the corner here and earlier in the thread I was thinking about firing at low tide for the purpose you stated. I've never been to the beach at low tide but I saw a picture of it and the beach was significantly wider and almost entirely damp sand which would be perfect. We will only have a single quad/ATV.

I was thinking about doing a decent distance calc as well, I think we would have only two estimated variables which would significantly alter the results: Cd and wind.

I'm not sure how we could calculate or even estimate the Cd of LeMaudit's projectile and a Cd varying by only 0.01 (or something like that) could change the range by up to 1000m + or -. I know wind has a significant effect on projectiles with a poor Cd like a golf ball but i'm not sure about projectiles which are very aerodynamic, but again, it could significantly change the range calculations.
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Unread postAuthor: jackssmirkingrevenge » Sun May 15, 2011 1:22 am

MrCrowley wrote:I know wind has a significant effect on projectiles with a poor Cd like a golf ball but i'm not sure about projectiles which are very aerodynamic, but again, it could significantly change the range calculations.


As you know, air drag increases exponentially with velocity, and wind changes the velocity of the projectile relative to the air, so its effects will be significant.

My suggestion is to fire in line with a known landmark or compass heading, ideally when the wind is right behind you to prevent drift. This means you can limit your search to a relatively narrow strip (less than 20 metres wide depending on wind) with the only variable being range, and of course you can use a rough range estimation to eliminate say the first couple of kilometres. Google maps could be a variable tool to determine an ideal launch site and the estimated landing zone, heck it wouldn't be the first time :roll:
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Unread postAuthor: ramses » Sun May 15, 2011 1:50 pm

If you can get the projectile in sabot to me in dwg, dxf(with blocks for the materials), or iam, I can run it through a FEM program.
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Unread postAuthor: Crna Legija » Sun May 15, 2011 2:01 pm

ramses wrote:If you can get the projectile in sabot to me in dwg, dxf(with blocks for the materials), or iam, I can run it through a FEM program.


this things going around the world :D
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