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ggdt HELP

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ggdt HELP

Unread postAuthor: FORE!!!! » Tue Jul 14, 2009 5:36 am

hello ive recently downloaded the ggdt and am wondering if i could get some help with filling in the blanks

ive attached a picture for refrence

in the chamber data colum its pretty straight forward only problem being i dont know the temp of the air im putting into the chamber???
any ideas???

in the second colum *(valve data)* it asks for what type of vavle im using but ball valve is not there????
also the flow coefient????? seat diameter??????? dead volume??????

im using a basic 1" ball valve?


i have other question but ill ask as the questions are answer,,any help is gratly appriciated
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Unread postAuthor: FORE!!!! » Tue Jul 14, 2009 5:48 am

i keep getting a RUN TIME ERROR DIVISION BY ZERO??
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Re: ggdt HELP

Unread postAuthor: jackssmirkingrevenge » Tue Jul 14, 2009 5:48 am

FORE!!!! wrote:forward only problem being i dont know the temp of the air im putting into the chamber???


Leave it as it is, room temperature.

in the second colum *(valve data)* it asks for what type of vavle im using but ball valve is not there????
also the flow coefient????? seat diameter??????? dead volume??????

im using a basic 1" ball valve?


Change valve type to "generic"

Flow coef around 35

Opening time - well, depends how fast you can open it really. I would say around 100ms to give you an idea.
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Unread postAuthor: frozebyte » Tue Jul 14, 2009 5:54 am

Is there even a box for opening time? :]
Dead volume is the amount of space between main valve and projectile :D
Hope it helps and if im even correct.

Cheers.
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 14, 2009 5:56 am

frozebyte wrote:Is there even a box for opening time?


If you change the valve type to "Generic" then yes.

Dead volume is the amount of space between main valve and projectile :D

Hope it helps and if im even correct.


That you are.
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Unread postAuthor: FORE!!!! » Tue Jul 14, 2009 6:02 am

wow changing it to "generic" made things alot easier lol

now for the projectile colum, friction??? initial position????

im using everyday marbles
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Unread postAuthor: FORE!!!! » Tue Jul 14, 2009 6:09 am

frozebyte wrote:Is there even a box for opening time? :]
Dead volume is the amount of space between main valve and projectile :D
Hope it helps and if im even correct.

Cheers.


it asks for an answer in inches cubed for the dead volume, my marble rest againt the internal ball from the ball valve so the is no dead volume???
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 14, 2009 6:22 am

FORE!!!! wrote:now for the projectile colum, friction??? initial position????


Leave friction as it is, intitial position and dead volume are zero if the projectile is resting against the valve.
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Unread postAuthor: FORE!!!! » Tue Jul 14, 2009 6:38 am

ok its come up with a warning that the barrel is choking the flow,,can some one kindly tell me if i should bother with this warning???

my ballistic range is 245m and takes 7 seconds to reach is that respectable???

muzzle velocity 156.6 m/s
muzzle energy 78.5 j
travel time 12.5 ms
pressure drop 0.4 psi

how am i doing ???????? is this a decent gun???? for what it is???
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Unread postAuthor: inonickname » Tue Jul 14, 2009 6:50 am

It's very optimistic. I'll model it for you..

Be back in a second

It gives me 253 feet per second, though I don't have a perfectly accurate valve opening time figure.
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Unread postAuthor: frozebyte » Tue Jul 14, 2009 6:55 am

Relax FORE!!!, cut it out with those triple question marks behind every question :D Take it easy, everyone here who knows how to use GGDT well would gladly help.

:D
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 14, 2009 6:59 am

FORE!!!! wrote:pressure drop 0.4 psi


How big is your chamber :shock:

Can you post a screen cap?

ok its come up with a warning that the barrel is choking the flow,,can some one kindly tell me if i should bother with this warning???


It just means your flow coefficient is too big but this doesn't affect the results.
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Unread postAuthor: FORE!!!! » Tue Jul 14, 2009 7:02 am

inonickname wrote:It's very optimistic. I'll model it for you..

Be back in a second

It gives me 253 feet per second, though I don't have a perfectly accurate valve opening time figure.


is that what ur guns projectiles travel at? or is that what mine does?

and sorry frozebyte this new proggy is exciting,ill use one of theses(?) from now on lol
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Unread postAuthor: FORE!!!! » Tue Jul 14, 2009 7:07 am

jackssmirkingrevenge wrote:
FORE!!!! wrote:pressure drop 0.4 psi


How big is your chamber :shock:

Can you post a screen cap?

ok its come up with a warning that the barrel is choking the flow,,can some one kindly tell me if i should bother with this warning???


It just means your flow coefficient is too big but this doesn't affect the results.


it 65mm pipe approximatly 1.1 m long

heres a link to the weapon http://www.spudfiles.com/forums/first-a ... 18684.html

a lil off topic but check out the last page and sus out my ammom holder and ammom i built it today ,and carbon fibre barrel
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Unread postAuthor: inonickname » Tue Jul 14, 2009 7:15 am

FORE!!!! wrote:
inonickname wrote:It's very optimistic. I'll model it for you..

Be back in a second

It gives me 253 feet per second, though I don't have a perfectly accurate valve opening time figure.


is that what ur guns projectiles travel at? or is that what mine does?

and sorry frozebyte this new proggy is exciting,ill use one of theses(?) from now on lol


That's yours. GGDT tells me I get 955 feet per second at 156.3 ft/lbs. From a 5g projectile.. And then if I use hydrogen, 1449 feet per second at 360 ft/lbs.. Ahh, 400 psi with a super efficient piston valve ported b a 1/2" QEV..what Won't you do? ( next gun)

It will go up or down depending on how fast you open the valve. I put in 200ms as a starting point. Spring loading would definitely give moar.
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