Homemade HPA v2 engine

[wyz2285]

Sup.
I had a G&P M4 with broken gearbox for about a year. Even though it wasn't working I got it accessories once a while and it ended up looking very good, a bit too good for just a new gearbox. While I'm not welling to spend >350 on a HPA engine and since it's a DMR build semi only was acceptable.
So, I ended up following a blow forward bolt design I saw here somewhere then added a coaxial piston valve piloted by a homemade 3-way as firing mechanism. The hardest part was definitely the 3-way, but all worked. Blow forward nozzle is the worst functional part, but for a first time attempt I'm happy it all worked, No leak everywhere not even the 3-way.
[youtube][/youtube]
Gonna check the FPS later and get a proper hop-up system, this thing needs a hard hop-up to get the bb fly straight.
Oh BTW I'd show you all the components but I REALLY don't feel like open the gearbox again

[jackssmirkingrevenge]

Very impressive, congratulations!

I guess it's semi-auto only which is a pity but nonetheless, well done!

I've played with PolarStar FE and Jack as well as Valken V12 and the fact that it's electronic makes it relatively easy to optimize but as you say, the price tag is not for everyone.

[wyz2285]

The Jack was actually acceptable, and now since yo have played with it, how does the solenoid works? My guess it's a custom 3way.

[jackssmirkingrevenge]

It's nothing more than a compact solenoid valve driving a blow forward bolt. Since you asked nicely, took one apart and took a photo

edit: just to clarify, it's a little bit more complex than that, since the solenoid has two ports that driver forward and backward motion of the bolt, which allows more adjustability in terms of power and efficiency.

[wyz2285]

Yeah I know it's like a blow forward bolt without a return spring. So the solenoid must be some kind of 2 postion solenoid. Could you please screw out the solenoid? From the only video I found where it was taken apart, it seemed very interesting, my guess is a coaxial 2 position.
Took mine apart, going to source a solenoid 3-way for it, mechanical not very consistent. It was doing 490FPS with 0.20 already though

[jackssmirkingrevenge]

Could you please screw out the solenoid?

Not for now, this is new stock. We'll have to wait until someone breaks one

[wyz2285]

I also confused it with the SMP, must say they look very similar though. Wonder whats the brand of the solenoid they used, it's rather unlikely that they made their own...

[vng21092]

Any way you can make a little sketch of your homemade 3 way pilot internals? Very curious, thanks.

[wyz2285]

Any way you can make a little sketch of your homemade 3 way pilot internals? Very curious, thanks.

The name says it all, it's a 3-way valve, just as any other 3 way valves.

[vng21092]

so basically the same way a slide valve works? but re-configured?

[wyz2285]

Not exactly, even though a slide valve is kind like a 3-way, mine can use all the 3 ports while s slide valve can only use 2.

Now, an update:
[youtube][/youtube]
It's not nearly useful, but I posted because I own this to dewey-1

[vng21092]

Would you say it's kinda like this?

[youtube][/youtube]

[wyz2285]

No, more like this:[youtube][/youtube]
The diagram I posted above shows how the internals work.

[vng21092]

ahhh ok I get it now. Thanks. I just bought myself one off Amazon to play with, hopefully I could implement it nicely into a new build.

[wyz2285]

Haha that's more like it!
[youtube][/youtube]