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GGDT request

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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GGDT request

Unread postAuthor: ALIHISGREAT » Mon Aug 18, 2008 2:20 pm

coaxial
101cm 28mm copper chamber (~26mm ID)
1m 15mm copper barrel (~13.5mm ID)
piloted by a 1/2" QEV piloted by a 1/4" sleeve valve
shooting a 3g spud slug at 200psi
3.5cm piston (about 15g)
no dead space
~8cc pilot volume for main valve
~15cc for sleeve valve to QEV


thanks

EDIT:changed specs
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Last edited by ALIHISGREAT on Tue Aug 26, 2008 4:03 am, edited 2 times in total.
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Unread postAuthor: Pilgrimman » Mon Aug 18, 2008 2:24 pm

230 for sure. A 30 psi difference is not worth the extra money in this case. You could probably pump it to 260 anyway, without reducing the safety factor of the pump too much. If you have the ability to build one, go for it!
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Unread postAuthor: potatoflinger » Mon Aug 18, 2008 6:29 pm

I can do it for you but I need the piston weight and the pilot volume.
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Unread postAuthor: ALIHISGREAT » Tue Aug 19, 2008 2:53 am

well the piston is going to be HDPE rod, but i can't find any density figures... all i know is that it will be between 3-5cm long and it has a 25cm diametre. and the pilot volume is about 8cc.
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Unread postAuthor: Ragnarok » Tue Aug 19, 2008 6:06 am

I have to ask where you're going to find an obscure size of ball bearing like 13.5mm (I know they do them, but they're not cheap... nearly a pound a ball I think. Ouch.), or how you're going to find steel with a specific density of 5.8 g/cm<sup>3</sup> (that's the density that would be needed for a 7.5g sphere. Steel is normally 7.7-7.8g/cm<sup>3</sup>) but anyway, using the figures you specified...

230 psi: ~167 m/s
260 psi: ~175 m/s

Assuming actual 13.5mm steel spheres of 9.9g:

230 psi: ~152 m/s
260 psi: ~159 m/s
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Unread postAuthor: CasinoVanart » Tue Aug 19, 2008 6:22 am

ALIHISGREAT wrote:well the piston is going to be HDPE rod, but i can't find any density figures... all i know is that it will be between 3-5cm long and it has a 25cm diametre. and the pilot volume is about 8cc.


HDPE comes in different densities, you will need to find out from the factory.
For example, we stock p300, p5000, p7000 etc HDPE, the lowest is crap, the last is super dense and tough, try grinding or cutting it and you will see the difference greatly.
Is there any chance of asking the supplier?
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Unread postAuthor: ALIHISGREAT » Tue Aug 19, 2008 7:29 am

the BB is from GEOMAG (i 'borrowed' of my little brother) and its more like 13mm (i misremembered the diameter) oh and the website i ordered off doesn't have the specs for the HDPE rod.
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Unread postAuthor: Ragnarok » Tue Aug 19, 2008 8:11 am

ALIHISGREAT wrote:the BB is from GEOMAG (i 'borrowed' of my little brother) and its more like 13mm (i misremembered the diameter)

In that case, it's 12.7 mm - 1/2".

In that case, GGDT gives...
230 psi: ~156 m/s
260 psi: ~163 m/s
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Unread postAuthor: ALIHISGREAT » Tue Aug 19, 2008 10:13 am

yeah but i'm going to give them a tape tail to stop them rolling out of the barrel aswell as making them fit tightly.
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Unread postAuthor: ALIHISGREAT » Tue Aug 26, 2008 4:03 am

Changed specs/edited origional post
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Unread postAuthor: mark.f » Tue Aug 26, 2008 9:01 am

Why can't you install GGDT if you can play COD4 (presumably on a PC)?

In Vista, you have to set it to run with Administrator privileges for it to operate correctly, if that's your problem.

EDIT - oh, your dad won't let you download it. Fair enough, although I would just download it anyway... it has virtually no chance of screwing up your computer since it doesn't even access files or addresses other than the ones you download to the same folder.
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Unread postAuthor: ALIHISGREAT » Wed Aug 27, 2008 2:59 pm

yeah i downloaded it last night (and i play 360 not PC) but the run as administrator thing confused me, i had to search to find that.
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Unread postAuthor: POLAND_SPUD » Wed Aug 27, 2008 3:47 pm

finally... no offence but this programme is usefull if you can use it yourself and 'play' with it... GGDT will work on almost any PC and it won't mess up your computer.... so if you can download it - Do it!!

GGDT requests can be compared to having sex on the phone... sure you can do it like that but it's not the same as doing it in real life :wink:
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