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spudgun range, are we falling short?

A place to ask general spud cannon related questions.
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Unread postAuthor: ilovefire » Tue Mar 29, 2011 7:48 am

i think the reason why it goes sideways is because of the cuped ends, if they weren't i believe they would tumble a lot more
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why make it if it dosent shoot?
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Unread postAuthor: LeMaudit » Tue Mar 29, 2011 8:13 am

I see now... thanks for the explanations guys... I definitely consider now a drilled conical bullets... and I can stop wondering how to keep it from rolling out of the barrel :D
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Unread postAuthor: Technician1002 » Tue Mar 29, 2011 9:58 am

For range, I'm thinking of turning some shapes like this on a lathe.. :D

Using a sabot in a larger bore to get the velocity up to something reasonable and I'm ready for a contest distance shot.

Image
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 29, 2011 10:15 am

Technician1002 wrote:For range, I'm thinking of turning some shapes like this on a lathe.. :D


The Grand Slam (1) would approach the speed of sound by gravity alone, so it's a good design to emulate :)

Using a sabot in a larger bore to get the velocity up to something reasonable and I'm ready for a contest distance shot.


Given your fast valves and large bores I dare say you should get some pretty impressive numbers for a small saboted streamlined round.
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Unread postAuthor: LeMaudit » Tue Mar 29, 2011 1:40 pm

I think that for something close to 50 cal, using a conical or ball lead bullet, and casting hard resin as a tail and fins using a RTV rubber mold would be not difficult. A screw could be a nice and sturdy support.

I believe (by experience ;-) ) it would take about 5 to 7 minutes per cast to make such a missile/bullet in quantity.

Do you think it would work as more precise bullet, and would flight more strait?
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 29, 2011 6:11 pm

LeMaudit wrote:Do you think it would work as more precise bullet, and would flight more strait?


It will certainly be more aerodynamic than a hollow tailed projectile. Brenneke type slugs use lightweight fibre or synthetic tails for this reason:

Image

You could always add dimples for MOAR POWAH! :roll: check the date!

Here's another way of doing it, with a lead nose and light balsa/foam tail section, and a central part of constant diameter to provide stability in the barrel.
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Unread postAuthor: POLAND_SPUD » Tue Mar 29, 2011 7:08 pm

Here's another way of doing it, with a lead nose and light balsa/foam tail section, and a central part of constant diameter to provide stability in the barrel.
It don't think it will work well (i.e. it probably won't be stable enough)

Base drag might be a good thing as it shifts CP to the back of the projectile
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 29, 2011 7:32 pm

POLAND_SPUD wrote:I don't think it will work well (i.e. it probably won't be stable enough)


Fins would probably need to be added, but I'm wondering if having a dramatically forward CG would make them unnecessary.
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Unread postAuthor: POLAND_SPUD » Tue Mar 29, 2011 7:55 pm

Well there is just one way to check that... I modelled similar projectiles in rocksim (there is a thread or a post on it somewhere.

IIRC D_hall replied that the programme isn't good enough to model cd values and other things accurately... not to mention that it's optimised to work with rockets

Anyway whenever I tried to model a truly streamlined projectiles or just used a boat tail design the base drag dropped dramatically and that shifted the CP closer to the nose
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Unread postAuthor: LeMaudit » Tue Mar 29, 2011 8:32 pm

I think I will try to cast a tail in resin like a little bomb. I've done several hundreds of similar casts like that in the past. Like this picture (it is painted resin, about 1 inch long).

The only think I don't know is if the resin will not be crushed while in the barrel... but I guess all the pressure will be on the lead nose so it should be okay.

Now I'm thinking I need to resupply resin and rubber. My stock is too old... and I also badly need a gun now :lol:
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Unread postAuthor: Mr.michael.2468 » Tue Mar 29, 2011 10:33 pm

First the tech stuff, skip to bottom for how to and materials:

not to but in here guys, but again im going to make an advertisement for the design of bullets i've dreamt up in the image of shotgun slugs like you suggested, and also with the budget of a jobless 16 year old in mind, a sabot works because of the high center of gravity towards the front of the projectile, this causes it to tend to "go that way" by that i mean it tends to not tumble like you've suggested as the lighter backing, or where you would "drill a hole" follows behind the heavier head of the bullet, and acts as a tail, like you would put on a kite, or i've used on large shells to either slow them down or increase accuracy by decreasing tumbling. a simple strip of fabric maybe 8inches long is good enough for a 2in diam. shell.

but any way back to the bullet design, i knew it have to be weighted by metal to be able to do any damage to a target and to have any kind of ballistic trajectory and hold up to my 2in sprinkler valve set up. so i went with 3/8in ball bearings, or slingshot ammo, very cheap, a box of 50 is like 3$. then for the tail i knew it would have to be rigid, and also be a perfect seal inside of a barrel, i looked long and hard but found that yellow electrical screw caps that you use to screw electrical wires together fit perfectly into a sch80 1/2in barrel. i don't remember the brand of these caps but i could figure it out easily. its like 10$ for a box of like 200 caps. you then simply hot glue or epoxy the ball bearings to the caps, and it literally is that easy they fly perfectly straight, leave perfect entry holes every time and are incredibly accurate for being smooth bore and being homemade ammo coming out of a home made 40$ sniper cannon

all in all you'll need a 1/2in sch80 pipe for a barrel: >2$
a box of yellow electrical caps: about 10$ for 200
and a case of slingshot ammo, (3/8in ball bearings): 50 for about 3$
and a hot glue gun or epoxy
i could make a video or try to post pics eventually by request. hope this explanation and bullet size works for you. i realize you were talking about a much larger bullet size but i gotta say i enjoy my sniper cannon a lot more then my behemoth of a potato cannon that is ridiculous to carry around takes forever to fill (by bike pump and air compressor).
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 30, 2011 1:06 am

LeMaudit wrote:Like this picture (it is painted resin, about 1 inch long).


They look vaguely like the shells fired by the Anzio Annie :D

Some good discussion of cast projectiles here.

its like 10$ for a box of like 200 caps. you then simply hot glue or epoxy the ball bearings to the caps, and it literally is that easy they fly perfectly straight, leave perfect entry holes every time and are incredibly accurate for being smooth bore and being homemade ammo coming out of a home made 40$ sniper cannon


This concept of a tube that fits in the barrel and is closed and weighted at one end can be applied to any calibre, I had good results for a 3/4" barrel cutting 12 gram CO<sub>2</sub> capsules in half and pouring lead at one end.
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Unread postAuthor: Labtecpower » Wed Mar 30, 2011 2:37 am

What metal would be most suitable for a solid projectile?

Aluminium, steel or something in that direction?
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Last edited by Labtecpower on Wed Mar 30, 2011 2:43 am, edited 1 time in total.
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Unread postAuthor: Technician1002 » Wed Mar 30, 2011 2:40 am

Labtecpower wrote:I guess it's cheating, but this is what I would like to do:


I think it is also against the rules.. You my wish to edit the post before a mod finds it.
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Unread postAuthor: Labtecpower » Wed Mar 30, 2011 2:44 am

Technician1002 wrote:
Labtecpower wrote:I guess it's cheating, but this is what I would like to do:


I think it is also against the rules.. You my wish to edit the post before a mod finds it.



I guess you were right :roll:
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