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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: Labtecpower » Sun May 15, 2011 2:09 pm

probably in two different ways :D


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Unread postAuthor: LeMaudit » Sun May 15, 2011 3:02 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.


I'm sure dewey1 will love to do that :-D
I'll give him quickly the final sizes for the sabot.


probably in two different ways


hahaha... Houston, we have a problem... :D
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Unread postAuthor: jackssmirkingrevenge » Sun May 15, 2011 4:02 pm

LeMaudit wrote:hahaha... Houston, we have a problem... :D


[youtube]http://www.youtube.com/watch?v=ZSSVM0TpqCs[/youtube]

:D :D :D
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Unread postAuthor: dewey-1 » Thu May 19, 2011 6:44 pm

jackssmirkingrevenge wrote:
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 ;)


Here is how to save about 2 grams per petal or 8 grams total!
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Unread postAuthor: LeMaudit » Thu May 19, 2011 7:04 pm

Yeah yeah... I love holes too...

I'm just afraid the thing will break or heavily deform under stress :-/ Call me chicken...

Nobody answered me about what we really gain saving a few %. Does it really worth it? I don't know how to do the math.

I agree it's about 15%... still, does it worth it?
And if I gain more weight, I would feel more safe by thinning some parts of the petal, like so, removing the pink parts.
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Unread postAuthor: dewey-1 » Thu May 19, 2011 7:19 pm

Round holes will have less chance of weakening the structural support than the cut outs you are proposing.

Just thought I would mention it as another possibility.

But with holes it will look like JSR's coffee table sabot! :D
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Unread postAuthor: LeMaudit » Thu May 19, 2011 7:47 pm

Round holes will have less chance of weakening the structural support than the cut outs you are proposing.


Really? Okay, I'm no expert in that matter :D

Holes it is. But I'll do them only when someone compute and show some significance in saving 10 to 15% of the total weight.

MrCrowley, can you do that?
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Unread postAuthor: MrCrowley » Thu May 19, 2011 8:24 pm

Sabot without ring is 50g right? I'd probably put stuff in the projectile to make it weigh about 100g (if not more but 100g will be used for the simulation). 150g all up at a 10x mix gives me 386ms with 11100 joules of energy :shock:
Shave 10g off the sabot weight and I get 397ms with similar muzzle energy.

What that means in terms of range:
150g sabot + projectile @ 386ms with a Cd of 0.1 = ~5650m
140g sabot + projectile @ 397ms with a Cd of 0.1 = ~5750m

So 10 less grams will add an extra 10ms to the velocity and 100m to the range. I like those numbers, 10, 10, 100 :wink:

Though if I add 40g (so 140g) to the weight of the projectile, I will lose about 50ms in terms of velocity (down to 330ms or so) but the range calculator spits out 5900m. So perhaps we should be looking at projectile density and not so much sabot weight?

Edit: JSR must be reading this with a smile thinking to himself "he's finally learning..." :D
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Unread postAuthor: LeMaudit » Thu May 19, 2011 8:46 pm

So perhaps we should be looking at projectile density and not so much sabot weight?


That's what I was thinking intuitively... but all those numbers make my head spin :compress:

And I'm sure you'll be able to be more than 100 grams for the MiniBoy. Half filled with lead, with some place left for magic powder, it's already 120 grams.

I'm really not comfortable weakening more the petals... maybe I'm wrong, but I would like you to be able to reuse the sabot a few times, especially if I manage to finish those damn DummyBoy :D
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Unread postAuthor: dewey-1 » Thu May 19, 2011 8:46 pm

MrCrowley wrote:Though if I add 40g (so 140g) to the weight of the projectile, I will lose about 50ms in terms of velocity (down to 330ms or so) but the range calculator spits out 5900m. So perhaps we should be looking at projectile density and not so much sabot weight?


Keep in mind that you need add as much weight as possible to get the miniboy COG at the minimum measurement I stated earlier or even closer to the nose tip. You will probably be adding 50 to 60 grams to achieve this.

It is still better to have the lightest sabot as possible.
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Unread postAuthor: MrCrowley » Thu May 19, 2011 8:53 pm

LeMaudit wrote:I'm really not comfortable weakening more the petals... maybe I'm wrong, but I would like you to be able to reuse the sabot a few times, especially if I manage to finish those damn DummyBoy :D

I share your concern with the sabot. I doubt I have enough room in my backyard for the sabot to fall safely to the ground at even 10PSI from a 1.5" porting piston cannon so I'll probably try 'catch' the sabot in a cardboard box filled with clothes and foam.
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Unread postAuthor: LeMaudit » Thu May 19, 2011 8:59 pm

I share your concern with the sabot.


Tell you what... I delegate to you the responsibility of drilling the petals :lol:

There, problem solved ;-)
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Unread postAuthor: dewey-1 » Thu May 19, 2011 9:16 pm

LeMaudit;

You could at least drill some .0625 inch pilot holes for him. Do you want the CAD file?

Now do not tell me that is going weaken the structural integrity! :)

You should also put some lead sinkers/BB shot in it and determine the COG before sending it.
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Unread postAuthor: LeMaudit » Thu May 19, 2011 10:15 pm

LeMaudit;You could at least drill some .0625 inch pilot holes for him. Do you want the CAD file?


Oh, all right :D , and yes.

You should also put some lead sinkers/BB shot in it and determine the COG before sending it.


I'll prepare something with some lead slugs I have.
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Unread postAuthor: jackssmirkingrevenge » Fri May 20, 2011 12:30 am

MrCrowley wrote:JSR must be reading this with a smile thinking to himself "he's finally learning..." :D


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Yes... YES! MUHAHAHAHAHA!

I really don't think the holes will weaken it but it's not going to make a huge difference in range so I would not insist on them ;)

http://www.tungsten-heavy-powder.com/
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