New hybrid (w.i.p.)

[Labtecpower]

As it seems now it holds pressure very well, but i'll do some tests with water.
The elecrode is in the right place, with a 1-1.5 mm gap.

[jackssmirkingrevenge]

What's your ignition source? I found that less than 0.5mm was needed with a piezo.

[Labtecpower]

I use the ignition box seen in my youtube video.
I'm able to pull 4cm sparks.
If you were using gaps that small i'm going to bend the electrode closer to the wall, but that doesn't exlpain why I got reliable ignition yesterday morning

[jackssmirkingrevenge]

If you were using gaps that small i'm going to bend the electrode closer to the wall, but that doesn't exlpain why I got reliable ignition yesterday morning

That was just for the piezo, with a more energetic spark you can get by with a larger gap.

[Labtecpower]

Found the problem.
When I pump the chamber to the desired pressure and let it sit for a while, it shoots without problems.
Is there a way I can mix the fuel in my hybrid?

The chamber of this thing is much longer than my previous one, so I think that bugs the mixing...

I'm thinking of adding a few BB's to the chamber, and shaking it before firing

[jackssmirkingrevenge]

I don't think this is your problem. You're pressurising the thing, it doesn't need agitation.

Are you venting properly between shots? That includes the pump volume I like to cover the mouth of the chamber with my thumb and pump air a couple of times before refilling.

[Labtecpower]

I tested it:

with proper venting, first click ignition, but with a very dull "pop"

second time I vented it, and I added a tin foil ball to the chamber.
I shaked it a few times, and this time I got a very loud bang

Let's make some holes

[SpudBlaster15]

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[Labtecpower]

I can't get this thing to work reliably as a hybrid, so I just filled it up with a mixture of hydrogen and oxygen from a small electrolysis cell.
I just needed some bangs

[youtube][/youtube]

Guitars disapproving in the background

[Labtecpower]

Finally working flawlessly
I added an extra connector so I could shake the chamber before firing, hopefully mixing the gas

Fus Ro Fail Dah

[youtube][/youtube]

[jackssmirkingrevenge]

Finally

I still don't think mixing is your problem though, rather achieving the right mix. Can you explain your exact fuelling procedure and calculations?

[Labtecpower]

calculating the chamber volume; (104 ml)

I calculated it by filling from a syringe.
First I emptied two 50ml syringes, and for the last bit I went to a 5ml one.

then (104*0.03230)*mix number

I measure the butane in a syringe, then gently inject it in the chamber.
Before fueling I vent the chamber thoroughly.
After injecting the butane I quickly put masking tape over the chamber opening.

Then I fill it to the right pressure, I use a valve that closes with a spring, it pops open at a pressure of 3 psi.

[jackssmirkingrevenge]

What are you using to pressurise though?

I calculated my shock pump has a dead volume of 1.75mL between pump check valve and schrader attachment, I add this to chamber volume when calculating fuel - indeed none of my hybrids worked before I realised this (because I was dealing mostly with small chamber sizes and this was significant).

Also, obvious and stupid question but I have to ask it, for say a 5x mix, you are pumping to 4 bar, right?

[Labtecpower]

Pumps dead space doesn't count with my gun I believe, the filling valve works as a check valve. There is no open connection between the chamber and the pump.
And yes, I pay attention to that
Good to point out tough

[jackssmirkingrevenge]

Pumps dead space doesn't count with my gun I believe, the filling valve works as a check valve.

I would not be too quick to assume that, if it were mine I would do some tests taking this volume into account.

You said it worked reliably with hydrogen, hydrogen has a massive range of concentrations it can ignite (5-75% if I recall correctly) so proportion is not so important. Butane on the other hand has a 2-8% concentration range, so it is a lot more sensitive for reliable operation.