Mjöllnir - 1.5" porting Handheld Piston Hybrid

[POLAND_SPUD]

I guess you are more likely to get 5.7% with a 0-51psi reg than with a standard 0-150 psi one.

Anyway you get the idea - 0-51psi might not be ideal but if there are 0-51psi regs then there are probably 0-20 psi ones too

[MrCrowley]

Why not just go with a 0-15PSI gauge like I did? While a regulator would be good for fast reloading and such, I doubt if it would be able to reliably fill at the set pressure.

By the way, notice the push-to-connect fitting? It's on the regulator to plug the gauge port since I don't need a gauge on the regulator.

[Moonbogg]

Very Nice Crowley. Does the pilot dump its air upon ignition? That looks like a seal at the end of the rod.

[MrCrowley]

Very Nice Crowley. Does the pilot dump its air upon ignition? That looks like a seal at the end of the rod.

Yeah that's basically how it works. Once the piston starts moving back, that seal is unseated, dumping the pilot. I stole the idea from SpudBlaster

[POLAND_SPUD]

Yeap I did. I guess it's just like with fridge compressors... you just have to mention something around 500 times - only then people actually realize 'hey, he might be right'

I doubt if it would be able to reliably fill at the set pressure

I guess that a typical 0- 10 bar reg has more less +/- 0.5 bar accuracy or so
So if you've got 0-1 bar reg then +/- 0.05bar accuracy might be ok for fueling

[Gun Freak]

Crowley, very nice. It looks like it would launch a spud (see sig ) Just a question though, why do you call the ball valve with a quick connect the pilot, is it because when you use it pneumatically it pilots the valve?

[MrCrowley]

Just a question though, why do you call the ball valve with a quick connect the pilot, is it because when you use it pneumatically it pilots the valve

Because I fill the area behind the piston with air, say 80PSI for a 5x mix, which pushes the piston forward and seals it against the barrel. This area is o-ringed and 100% sealed off from the chamber. So then you put the mix in the chamber and ignite it, the combustion then pushes back on the small exposed area of the sealing face, overcoming the 80PSI in the 'pilot' which is pushing the piston forward (with a much greater area to push against). Once the piston starts moving back, the 'pilot' air is dumped out through the pilot valve (the gasket on the rod at the end of the piston).

[Gun Freak]

I know how the valve works, I was just wondering why the valve was called a pilot valve. I guess just because it is in the pilot I've already designed a piston hybrid. I won't make it though I may get around to making a smaller porting hybrid some day, or possibly converting my detent bbmg into a small hybrid.

[MrCrowley]

why do you call the ball valve with a quick connect the pilot

I don't call the quick connect and ball valve the pilot valve by the way, I'm referring to the gasket on the rod.

I was just wondering why the valve was called a pilot valve. I guess just because it is in the pilot

Because it is a pilot valve...
If the gasket on the rod pilot valve setup wasn't there, the piston would probably move back a short way then bounce back in to the seat and close.

[Matt_NZ]

I'm still gawking at those pictures, even though I saw them on chat the other day.
Anyway, what exactly does the piston seat on? I can't quite tell from the pictures.

[MrCrowley]

This is the seat inside the housing:
http://i75.photobucket.com/albums/i290/ ... MG0198.jpg

This is it removed from the housing:
http://i75.photobucket.com/albums/i290/ ... C00591.jpg

Just a 1.5" barrel nipple epoxied in to the back of a 2"x1.5" bushing.
Is that what you were looking for?

[Matt_NZ]

Just a 1.5" barrel nipple epoxied in to the back of a 2"x1.5" bushing.

That's what I was after.
Do you mind me asking how much (approx) this cost you to build? I would presume those 2" fittings cost a bomb.

[MrCrowley]

Depends, most are around $10 each, some go as high as $15 and some as low as $7.

Here's a list I kept throughout the build process for the cost of this build. I wrote this as I went, so there aren't totals for say all the galv fittings, also it doesn't including stuff I already had:

Galvanised Fittings (chamber) - $68
Piston Bolts, Nuts, Washers - $35
galv fitting, bolt fitting - $17
ball valves 1/4" x 2 - $14
pressure gauge 145psi - $20
pressure gauge 15psi - $25
male 1/4" quick connect - $7
1/4" nipples and teflon tape - $11
50mm PN12 3m ABS barrel - $65
galv fittings for barrel - $25
galv fittings for chamber - $30

Total - $317

edit:

Just a little teaser:
[youtube][/youtube]

[SpudBlaster15]

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[Gun Freak]

Sorry Crowley I get it now
Funny video... I do that all the time with my big pneumatic hahahah.