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homemade combustion light gas gun idea (CLGG)

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homemade combustion light gas gun idea (CLGG)

Unread postAuthor: plasman65kv3Ma » Thu Jun 28, 2012 11:24 pm

hello this is my first post, my english isnt very good so please if i have an error dont complain. since i was a kid i wanted to see a meteorite impact when i could have acces to internet i knew about light gas guns and recently about Larda's hybrid then i begin doing some research and come accros CLGG guns, started in my head an idea of a hybrid with the sig specs
chamber volume 500cm3
ignition presure:200X
propellant:70%helium 21%oxigen 8%methane
bore diameter:25mm
bore length:2.5 meters
projectile:saboted 10mm ball bearing
projectile weigth:18.4g (8.4g ball bearing+10g polypropylene sabot)

what do you think will be the performance of this cannon? do you really think will reach hypervelocity? and if its possible to build such device with less than 2500$ tanks for all you help
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Unread postAuthor: jackssmirkingrevenge » Fri Jun 29, 2012 3:28 am

With those specifications, you will be going at several times the speed of sound but not necessarily hypersonic.

Here's some HGDT models using propane, for which 2.5 metres is too long a barrel length.

You might want to consider fuel/oxygen mixtures as opposed to fuel/air mixtures, allowing you to pack more energy in the system for a given pre-ignition pressure, though the dangers of DDT would then rear their ugly head and you would better hope that your chamber and barrel can take the strain.
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Unread postAuthor: Fnord » Fri Jun 29, 2012 9:08 am

Since your velocity is approaching the speed of sound in a combusted propane/air mix (in the simulation) the efficiency will be going way down. Since you are using helium as a buffer gas, your numbers will be higher than the simulated numbers.
You still won't get close to the velocities of 'meteorite guns', but it'll be a nice violent impact by hobbyist standards.
DYI will be able to give you some more detailed information.

You can use GasEQ to find an optimum mix, though I don't know if there is a translated version out there.


It would be quite possible to build this for less than $2500, but that's assuming you do the machining yourself. You could build a primitive version for less than $500 easily, assuming you pay reasonable prices for material.
You could get a much more practical solution for the money by just using conventional explosives, but it may not be possible where you live and is not something you should discuss here. There are other forums out there that can help you.
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Unread postAuthor: plasman65kv3Ma » Fri Jun 29, 2012 10:53 am

thank you for your feedback i already try it with cononventional ways and i have great results but i dont want to be caught doing such things, and i dont have space to do test of 20g+ of magic stuff so i think a gun of this kind is more feasible and is legal as a research tool
JSR:tanks for modeling in hgdt but i did it in ggdt because hgdt didnt have metane as fue,l and gave me 10053 f/s
with the sig specs
working fluid: helium
temperature:2000F°
pressure:25000psi
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