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GGDT/HGDT Request Thread

A place to ask general spud cannon related questions.
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Unread postAuthor: saefroch » Wed Nov 28, 2012 10:16 am

Here you be:
Image
or 370m
Image
or 457m
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GGDT calculation check please

Unread postAuthor: evilvet » Tue Jan 29, 2013 2:20 pm

Hi all

Could someone please check me on GGDT with the following configuration:

This valve with a 1/4" slide valve as pilot
http://www.ebay.co.uk/itm/XQ170600-2-Position-3-Ways-Air-Pneumatic-Quick-Exhaust-Valve-/380530040707?ssPageName=ADME:L:OU:AU:3160
Which I am plugging in as 6.25mm seat/piston and 1cm3 as the pilot volume for the slide valve.

Dead volume is guessed at 2cm3 since the barrel/breech is pretty much hard up against the valve output
300mm of chamber length @ 20mm I/D
1000mm barrel @ 10mm I/D
10mm plastic BB weighing 1 gram
100psi @ 20 degrees C

I get 135m/s or about 440fps, which I am very happy with.

Do those numbers sound right ?

Thanks
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2013 3:12 pm

Sounds about right, this is some real world data with my eBay QEV:

I hooked up a 12 inch 6mm barrel and did some chrony testing at 120 psi. The firing chamber volume is around 3.5 cubic inches, a little wasteful but that's what I had ;)

Using 0.25g airsoft BBs, I got an average velocity of 590 fps, more than enough to punch through a soup tin. With some adapted 1 gram 0.22" pellets I got an average of 355 feet per second, fairly decent.
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Unread postAuthor: evilvet » Tue Jan 29, 2013 3:48 pm

Thanks Jack, appreciate the quick fact-check

The power is interesting, at least to me who does not dabble in HPA or hybrids.

1.
Wadded a 2" bullet head nail with tissue to fit the barrel.
From three metres it went through both sides of a metal tomato can

2.
Plastic BB at 3 metres went through 4mm of cement fibre board then smashed into the whiteboard on the wall behind and made a bloody great crater in the surface about 5mm deep. Bugger it !

3.
At fifteen metres across the back yard a 10mm plastic BB punched a hole through both sides of a laundry bucket, doesn't sound like much but these little BB's are so brittle you can crush them under your boot and that bucket was thick hard plastic. One stuffed bucket and one pissed wife.

There is NO trace of the BB after impact, it just shatters into dust but boy it does some damage. More to follow.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2013 3:52 pm

Ah, so this is a model of an existing device?
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Unread postAuthor: evilvet » Tue Jan 29, 2013 4:09 pm

Internals for this
http://fc00.deviantart.net/fs36/f/2008/263/0/b/Halo_3_Sniper_Rifle_Model_by_timittytim.png

My boys are nuts on Halo plus a chance to give the CNC machine a good workout making TOYS not any sort of air rifle / firearm :D

BTW, thanks to you/mod who put this thread in the right place.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2013 4:36 pm

evilvet wrote:My boys are nuts on Halo plus a chance to give the CNC machine a good workout making TOYS not any sort of air rifle / firearm :D


Lucky kids :)

BTW, thanks to you/mod who put this thread in the right place.


I'm guessing it was MrC, for the sake of the forum and the hobby at large I have no such powers ;)
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Unread postAuthor: wyz2285 » Tue Jun 04, 2013 2:34 am

HGDT isn't working for me, it says some files are missing.
Already re downloaded it, still says the same thing.
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: wyz2285 » Tue Jun 04, 2013 2:35 am

HGDT isn't working for me, it says some files are missing.
Already re downloaded it, still says the same thing.
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: Crna Legija » Tue Jun 04, 2013 4:57 am

what operating system are you using? for vista and newer you need to right click and then click ''run as administrator''
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Unread postAuthor: wyz2285 » Tue Jun 04, 2013 5:06 am

Thanks! I'm running it on win8 so that must be the problem
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: BigDeutcher » Fri Sep 06, 2013 10:01 am

Okay i reload for my IPSC, hunting and general plinking enjoyment and have several ballistic programs, where does one acquire the programs that are mention in this thread?
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Re: GGDT/HGDT Request Thread

Unread postAuthor: dart guy » Tue Oct 15, 2013 8:36 pm

Hey I got a guestion how do you get this software because this would be good for flashdrivin' at school( using a flashdrive for non Internet programs) also I think I truer to get it but I couldn't open it do you need a fancy thing like an emulator?
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Re: GGDT/HGDT Request Thread

Unread postAuthor: sagthegreat » Wed Dec 11, 2013 10:05 pm

I am making a coaxial sniper, my I get help :D
Gas: Air
Chamber Dimensions: 1/2 inch ID and 1ft long copper pipe
Barrel Length: 24 Inches 6mm ID (Tightbore Barrel) 11 Inches of Barrel Inside the chamber, 13 Sticking Out
Pressure:250 PSI
Trigger: Blow Gun
Piston Diameter: .49 Inches
Piston Weight: ?? Making out of Derlin, so 5 grams?
Pilot Distance- .25 Inches

Projectile: Airsoft BB .2 Grams


What I want to know is how thin(diamter) and or short can I make the chamber and still hit a peak fps with 250 psi and 24 inch barrel
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Re: GGDT/HGDT Request Thread

Unread postAuthor: jackssmirkingrevenge » Thu Dec 12, 2013 6:03 am

Here you are, modelled at 100%, 200%, 50% and 25% of your specified chamber volume
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