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Step Barrel / Potato burst disc

A place to ask general spud cannon related questions.
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Unread postAuthor: sputnick » Mon Apr 13, 2009 5:14 pm

Alright, so if I understand correctly, there are 2 barrel knives, and the first is the one you put in, then the second one is cut when fired. If that is the case, you are going to have a barrel full of spud shavings in a reasonably short amount of time.

I would try to pursue an easily replaced burst disc if I were you, maybe just a half coupling that could fit over the barrel knife, that way it could be an optional thing

So yes, I suppose it could work, but if you're shaving it down inside the barrel, you would need to clean out the shavings every couple of shots, so I don't see it being a good idea.
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Unread postAuthor: King_TaTer » Mon Apr 13, 2009 6:16 pm

lctchamp wrote:I doubt his customers would like the idea of unscrewing a union or undoing a camlock and then having to cut the disks from foil.

If this is true then why would the customer want a minor increase in performance anyway?

Also there are alternative burst disk materials and methods that are faster than the ones you stated. And c'mon hes got a machine shop. :P
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Unread postAuthor: LCTChamp » Mon Apr 13, 2009 6:27 pm

King_TaTer wrote:
lctchamp wrote:I doubt his customers would like the idea of unscrewing a union or undoing a camlock and then having to cut the disks from foil.

If this is true then why would the customer want a minor increase in performance anyway?

Also there are alternative burst disk materials and methods that are faster than the ones you stated. And c'mon hes got a machine shop. :P



What I said has nothing to do with an increase in performance. I said they wouldn't want to put extra work into shooting.

The second part is true but machining parts would make it cost more.
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Re: Step Barrel / Potato burst disc

Unread postAuthor: jackssmirkingrevenge » Tue Apr 14, 2009 12:21 am

SPG wrote:I seem to have gone on about the idea quite a lot back then didn't I?


Indeed :)

Well jagerbond, why not give it a go and chrony the results?
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Unread postAuthor: starman » Tue Apr 14, 2009 2:50 am

It's certainly something to try. However, I have found that potato ammo tends to like a slightly gentle acceleration down the barrel. Burst disk potato shots invariably becomes potato salad on the way out of the barrel.

Anything mechanism that emulates the instant release characteristic of a burst disk would be running in to the same troubles.
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Unread postAuthor: SPG » Tue Apr 14, 2009 11:02 am

Just occured to me that a coax is a great place to start for a burst disc.

Glue half a threaded union on the end of the barrel inside the chamber, load your projectile, clamp the burst disc between the the union and the threaded collar, close chamber, and fire.

Does that make sense or do I have to spend an hour googling plumbing fittings?
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Unread postAuthor: jagerbond » Thu Apr 16, 2009 2:58 pm

Results, poor performance, and potato salad not even worth getting the Chrony out.

It did get me thinking about a burst disc hat to cover the barrel end once the spud is loaded.

Mike
Sureshot Inc. http://www.ultimatespudgun.com
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Unread postAuthor: jonnyboy » Thu Apr 16, 2009 4:19 pm

jagerbond wrote:Results, poor performance, and potato salad not even worth getting the Chrony out.

It did get me thinking about a burst disc hat to cover the barrel end once the spud is loaded.

Mike
Sureshot Inc. http://www.ultimatespudgun.com

If your trying to get more performance out of your gun, potatoes as ammo are a bad idea.

Burst disk + golfball + camlocks= FTW :D
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Unread postAuthor: SPG » Thu Apr 16, 2009 4:23 pm

No need for camlocks if you build it coax, just give it a burst disc hat.
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Unread postAuthor: jagerbond » Thu Apr 16, 2009 4:37 pm

material suggestions
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Unread postAuthor: Hotwired » Thu Apr 16, 2009 4:53 pm

Aluminium foil or scored aluminium sheet.

Scored (or stamped) aluminium sheet disks would look like a better value product than circles of foil anyway :)
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Unread postAuthor: jonnyboy » Thu Apr 16, 2009 4:54 pm

Oh that's what he meant by hat... I thought this was a standard combustion.
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mobile chernobyl wrote:I can shoot a Canuter Valve off my '82 Chevy Ram F150 AT LEAST 3/4 Mile with 'ma cannon made of soup cans duct taped together, then I just squirt some bacardi 151 in the chamber and hold up my cigarrete lighta and WHOOSH! That thing flies at least 3/4 mile
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Unread postAuthor: SPG » Fri Apr 17, 2009 4:43 am

It is but even a combustion can benefit from a burst disc.
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Unread postAuthor: jimmy101 » Fri Apr 17, 2009 1:25 pm

You could always donwload HGDT and fiddle with the parameters to see what kinds of performance gains you might get.

HGDT only allows you to enter a single friction value. From that it uses, IIRC, the entered value as the static friction and half that value as the dynamic friction.

To calculate the affects of high static but low dynamic friction you can include a burst disk in the calulation. You should be able to tweak the burst disk rupture pressure to simulate a high static friction and use the friction parameter to mostly model the dynamic friction. Basically something like;

static friction = (entered friction) + (burst disk pressure * burst disk area)
dynamic friction = 0.5*(entered friction)

It's always nice to have some idea what kinds of perfomance gains a modification may give you. A PITA mod isn't worth the effort if it only boosts performance by a couple percent.
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