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GGDT Something strange is happening

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GGDT Something strange is happening

Unread postAuthor: boyntonstu » Sun Sep 13, 2009 10:40 am

Image

Image


The only input difference is the chamber OD.

Am I missing something?

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Last edited by boyntonstu on Sun Sep 13, 2009 10:45 am, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 13, 2009 10:44 am

Double the OD and you get 4 times the volume, which accounts for the jump in performance
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Unread postAuthor: Ragnarok » Sun Sep 13, 2009 10:46 am

Oh dear, we have the OD/ID problem again.

Chamber OD is the inner diameter of the outer pipe of the chamber.
Chamber ID is the outer diameter of an inner coaxial pipe (usually the barrel). If you're not using a co-axial chamber design, then this should be set to zero.
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Unread postAuthor: boyntonstu » Sun Sep 13, 2009 11:33 am

Ragnarok wrote:Oh dear, we have the OD/ID problem again.

Chamber OD is the inner diameter of the outer pipe of the chamber.
Chamber ID is the outer diameter of an inner coaxial pipe (usually the barrel). If you're not using a co-axial chamber design, then this should be set to zero.


Mucho thanko's!

Image

Is this a reasonable representation of my layout?

BTW 54 grains is a glass marble.

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Unread postAuthor: Ragnarok » Sun Sep 13, 2009 11:43 am

boyntonstu wrote:Is this a reasonable representation of my layout?

I can't be entirely sure. I'm not familiar with US pipe sizes - but nothing seems too much out of place.

BTW 54 grains is a glass marble.

An 0.8" glass marble that weighs 54 grains? I think not.

If you're using wadding for a smaller marble, maybe, but if not, a marble of that size would weigh around 170 grains.
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Unread postAuthor: D_Hall » Sun Sep 13, 2009 11:54 am

Ragnarok wrote:Oh dear, we have the OD/ID problem again.

Chamber OD is the inner diameter of the outer pipe of the chamber.
Chamber ID is the outer diameter of an inner coaxial pipe (usually the barrel). If you're not using a co-axial chamber design, then this should be set to zero.


Or to put it in the terms that GGDT assumes.....

OD is the outer diameter of the volume of air contained by the chamber.
ID is the inner diameter of the volume of air contained by the chamber.
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Unread postAuthor: boyntonstu » Sun Sep 13, 2009 11:56 am

Ragnarok wrote:
boyntonstu wrote:Is this a reasonable representation of my layout?

I can't be entirely sure. I'm not familiar with US pipe sizes - but nothing seems too much out of place.

BTW 54 grains is a glass marble.

An 0.8" glass marble that weighs 54 grains? I think not.

If you're using wadding for a smaller marble, maybe, but if not, a marble of that size would weigh around 170 grains.


You are very astute!

Wadding around a .62 glass marble.

I calculated the marble weight on 2.5 gm/cm^3.

I will weigh them to make sure.

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Unread postAuthor: D_Hall » Sun Sep 13, 2009 12:33 pm

Don't forget that you need to include the mass of the wadding.
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Unread postAuthor: Ragnarok » Sun Sep 13, 2009 1:02 pm

That still sounds low (even without D_Hall's point above). I calculate ~79 grains for a 0.62" marble.

Still, to be sure, I've weighed some of my (nominally) 5/8" marbles on my 0.01 gram scale. Almost all bang on 5.11 grams - or 78.9 grains.
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