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problem by designing shell ejection system

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: jackssmirkingrevenge » Fri Nov 16, 2012 12:35 am

You don't need to lubricate the cartridges for effective feeding, remember that because of pre-ignition pressure, the cartridge diameter expands ever so slightly. It's important that when you check for fit, you do so with a pressurised cartridge. After the cartridge is fired, this pressure is gone so it contracts to its original size, making extraction much easier as there is less friction.

The only problem with not having some sort of claw system is that in the case of a misfire, it's a little tricky to remove the dud cartridge... though in practice, pointing the launcher upwards and manually pulling back the bolt should do the trick.
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Unread postAuthor: nitrogigi » Fri Nov 16, 2012 3:39 am

yeah!!!! good idea
I rebuilded a simpler shell, if it works it would be awesome

I'm thinking about H2 as fuel, but with air as comburant and not O2 wich were too dangerous, but I didn't find how to calculate the pressure produced by such a combustion... does someone knows?
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Unread postAuthor: nitrogigi » Fri Nov 16, 2012 5:36 am

in cas of misfire I put a magnet on the piston, wich would pull the cartridge back

about your cartridge : how do you regulate the "burst" pressure of your system?
HGDT give me an optimal pressure of burst between 25 and 30 bars.... but I don't know how to be sure it won't fire before with your system
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Unread postAuthor: jackssmirkingrevenge » Fri Nov 16, 2012 6:43 am

nitrogigi wrote:I'm thinking about H2 as fuel, but with air as comburant and not O2 wich were too dangerous, but I didn't find how to calculate the pressure produced by such a combustion... does someone knows?


It's not going to be much different from what propane or butane will give you if you're calculating using HGDT

about your cartridge : how do you regulate the "burst" pressure of your system?
HGDT give me an optimal pressure of burst between 25 and 30 bars.... but I don't know how to be sure it won't fire before with your system


You need to have some way of adjusting the o-ring compression, ideally it would be between two threaded fittings.

Do you have access to machine tools for this project?
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Unread postAuthor: nitrogigi » Fri Nov 16, 2012 7:25 am

I'm designing in parralel an all-in-one machine tool on a driller basis

Image

in blue, the part machined, in orange the wheels and in red the tool

you can see the 2 mods : turning and milling[/img]
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Unread postAuthor: jackssmirkingrevenge » Fri Nov 16, 2012 7:34 am

I would say save some money and buy a proper lathe and mill, but if you fancy the adventure go ahead ;)
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Unread postAuthor: nitrogigi » Fri Nov 16, 2012 7:48 am

a driller costs about 60 € at first price, I would have maybe for 40 mor for the rest

a lathe+mill in one costs around 600 €

the difference in quick seen
ok, I won't have a super precision, because I'll use normal threaded shaft for the mooving of the tool/part, but I've already machined on old crapy machines , and my grand-father teached me own to supress the clearance
I already have the tools given by my grand father
thoose are good old resistant tools not the crapy ones of today they sell to the public
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Unread postAuthor: nitrogigi » Mon Nov 19, 2012 2:35 pm

here are the firsts outifit of the 3D model:
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 20, 2012 1:46 am

Reminds me vaguely of the F2000 :) how do you plan on making the body?
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Unread postAuthor: nitrogigi » Tue Nov 20, 2012 2:06 am

I'll make it in two wood parts with the inner milled to place all the parts
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Unread postAuthor: nitrogigi » Tue Nov 20, 2012 5:06 pm

here is the electronics sketch:
Image

the reed switch is a normaly closed

to lock it in semi-auto mode, the selector avoid the trigger to get full back, so that the white part is between the two conductors

to shoot in full auto, you push the trigger slowly, so, when the grey part of the trigger makes contact, the coil loads, when the white part is between the contacts, the coil sparks, the blowback acts, you push the trigger full back, the coil reloads, a new shell comes, open the reed contact, and the coil sparks again, the cycle is launched

motha fu**** sh**, I just saw it doesn't work.... I found the solution but it's now time to sleep for me
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Last edited by nitrogigi on Tue Nov 20, 2012 6:01 pm, edited 1 time in total.

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Unread postAuthor: Goats spudz » Tue Nov 20, 2012 5:23 pm

Milling with the drill press isn't such a good idea, there not build for the stress of feeding it into the work and eventually you will wear out your bearings.
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Where's my Chuck key?

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Unread postAuthor: nitrogigi » Tue Nov 20, 2012 5:42 pm

this will only be for very light machining, and I'll add a bearing above the chuck, the heaviest machining I'll do may be milling 1 mm of aluminium with a 10mm of diameter mill
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