SpudFiles

Parts arrived, epoxy curing. Lots of bubbles collecting at the surface, I sincerely hope I don't have any stuck below.

Cured, epoxy work appears to be finished.

Threads very exposed because I have to still add the piston and might need to do some adjustments.

Macro button on that last pic

Is there something I am missing ? tell me that the valve is not a balanced QDV

By the looks of the piston, it is a balanced spool valve... but how are you going to pull the piston back? I don't see the purpose of the 3 90° knees and 3 pieces of pipe.. looks like it could be used as a handle... one heavy handle is it?

it is a balanced spool valve

now tell me how the hell is it going to work with a hybrid

I don't see the purpose of the 3 90° knees and 3 pieces of pipe.. looks like it could be used as a handle... one heavy handle

IIRC he build a pneumatic that looked similar

Personally I think it would be better if there was just one coaxial chamber - that would result in better performance and lower mass

now tell me how the hell is it going to work with a hybrid

Don't ask me... I'm not into hybrids and probably never will.
If hybrids are half pneumatic and half combustion, maybe this is like 75% pneumatic and 25% combustion

There's a diagram Fnord posted of a QDV with a sort of internal pop off valve inside the QEV that kicks it open at ignition. Thats the design I Believe he's using

That picture, if you take notice, is focused on the inside of the valve, showing the nice smooth epoxy cavity.

I messed up an order so unfortunately, there's just an elbow where there should be a tee, so I can reset the piston. But it was proposed that the valve may shut itself when the gases inside the barrel and chamber cool, and the piston bounces off the bumper (also yet to be installed), so I'm going to hold off on another order until I can test.

Yes, it's a balanced spool valve/QDV. Coaxial would be better, but I had the parts already for this setup.

The mess of pipes at the back is a stock and handle. It'll become a bit more obvious when I get my ignition setup sorted.

The setups for the bumper and beginnings of the internal piston are drying, they'll be curing soon. The valve itself is leak-free up to ~170psi, but the spark plug was not. I drilled out most of the epoxy and I'm going to try again. I'll post pics when I have something new to show for my efforts.

First attempt at casting the internal piston out of epoxy was an epic fail, but at least I've learned a lot from it:

It didn't seal, is it possible that is entirely due to the crooked nature of the o-ring?

What on earth were you trying to cast it in, a cardboard tube?

And why so long?

:withstupid:
Sorry jack, 8)

I tried to cast it in heatshrink tubing, but I guess it didn't shrink uniformly. I actually intended it to be a bit longer. It must extend from the barrel (which it pushes off of, so to speak) to the other side of the spring inside the piston.

I'm going to try again tomorrow if I don't get access to a drill press. If I do, I'm going to try making one out of steel.

saefroch wrote:I tried to cast it in heatshrink tubing

There's your problem

You need a smooth, uniform tube, ideally the same that the piston will travel in.