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Latke Data Collapse... The Plot Thickens

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Latke Data Collapse... The Plot Thickens

Unread postAuthor: D_Hall » Mon Apr 14, 2008 2:26 am

OK, so we've spent a few days arguing over the long-barrel velocity collapse exhibited by the Latke L2 1.5" shooting spuds. I've spent a lot of time studying that scenario. Why THAT scenario? I dunno, I just grabbed it and ran with it.

Anywho, after much wracking of brains here's the best that I came up with....

Image

...Disgusted with my inability to model the much discussed knee in the curve I decided to just move on and come back to it at a later time. I finished up some bits and pieces of HGDT and even went to work on the webpage.

Working on the webpage I felt that I needed to compare HGDT to *something* so I revisited Latke. Yeah, the spud has already been talked about. Given how badly I was modelng the spud I was scared to see what would happen if I modeled anything else.

Long story short: I threw HGDT up against the Latke L2 shooting wood data.

WTF?......

Image

....While I love that HGDT is riding the Latke data pretty well... Where did the knee go?


ARGGGGHHH!

Project for immediate future: Look at the rest of Latke's data. Is the knee endemic to the spud data, but not the wood data? If so, why? Blah blah blah.
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Unread postAuthor: starman » Mon Apr 14, 2008 2:41 am

Hummm interesting. Maybeeeee the spud seals the barrel and the wooden slug doesn't....... or... moisture in the spud vs not in the slug.... or.... wooden slug is a smaller caliber....

Just thinkin' out loud here....
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Unread postAuthor: psycix » Mon Apr 14, 2008 6:17 am

Maybe you should perform tests on your own.
That way you can measure anything you want and will have accurate data to work with.

I cant see why the wood doesnt knee
Weird it is.....
Maybe the wood knee has fallen off the graph since the wood tends to go faster


EDIT:

ARGGGGHHH!

AAAAAAAAAAAAAAAAAAAAAAARGH! :evil:

lol :D

Use facepalmdeaddeskcombo?
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Last edited by psycix on Mon Apr 14, 2008 11:10 am, edited 2 times in total.
Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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Unread postAuthor: JDP12 » Mon Apr 14, 2008 7:21 am

interesting results... i'm with physix on doing your own testing
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Unread postAuthor: jimmy101 » Mon Apr 14, 2008 1:44 pm

I believe Latke breech loaded his spuds. Perhaps blowing a spud down a many foot long barrel abraided the spud and dropped the friction and/or created blow-by? In other words, a long barrel acts funny with fragile ammo like a spud?

BTW, my combustion model also has trouble with the"knee".
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Unread postAuthor: SpudMonster » Mon Apr 14, 2008 5:32 pm

psycix wrote:Maybe you should perform tests on your own.
That way you can measure anything you want and will have accurate data to work with.

I cant see why the wood doesnt knee
Weird it is.....
Maybe the wood knee has fallen off the graph since the wood tends to go faster


EDIT:

ARGGGGHHH!

AAAAAAAAAAAAAAAAAAAAAAARGH! :evil:

lol :D

Use facepalmdeaddeskcombo?


Hmm. That could be the case. The wooden slugs have less friction and weigh more, so they could wind up coasting past the knee. Or as has been stated before, the spuds could be abrading.
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Unread postAuthor: clide » Tue Apr 15, 2008 4:41 pm

Those wooden slugs have gaskets on the back don't they? The gaskets could be acting like a check valve. No blow-by when the pressure on the chamber side is higher than the muzzle side, but once the pressures are reversed the gasket is able to flop backwards and allow blow-by and reduce friction.

Of course the bad thing with that theory is that the knee still exists for a normal gun, but the projectile design is preventing it.

Does the knee show up on the tennis ball data as well?
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