PMHL by Airpress (Pressure Metered Hybrid Launcher)

[airpress]

Hi folks.

I started a week ago with building a simple hybrid.
It was that type of launcher i never builded since 8 years. So I thought it was time.

When I had in my mind of building one. My only problem would be the ignition. So after searching/thinking i came with the ideal solution.
Here we have those electric fly/wasp killer. I just toke the hole thing apart, cutted the wires, en then tested. The standard voltage the systems works with is 2x 1.5v alkaline batteries. I upgraded it to a 4.5v battery.
It increased the spark!

So some info about the hybrid i'm making:

chamber: 1.5" steel pipes (the excat volume is 710ml, fittings included, i measured it with water)
barrel: I will begin with 1m 22mm copper pipe
propane measuring: since I will not use a propane metering system with a pipe and ballvalves, I think you know what i mean. I will use pressure metering, thats why i'm placing a 0-1 bar manometer. Off course it can be cut off the chamber, otherwise the manometer can be trassed when I hit the ignition button.
ignition: electric fly/wasp killer ignition (upgraded to 4.5volts instead off 3v)
valve: 3/4" union (burstdisk)

Here a some pics of the pipes connected together.






Th ignition will be controlled in a simple box.


Ignition ( I will make a movie when I have time of the ignition)


Airpress

[wyz2285]

That fly killer will not work, increase 3v to 4.5v won´t help and will reduce the transformers´life. It works with a capacitor (that red block) instead of a burst coil like in a tazer. The transformer charges the capacitor, when a fly is hit, the capacitor dump the current to kill it. The voltage of these thing are pretty low, less than 1000v, not enough to ignite a hybrid reliably.

[airpress]

Its strange, when I have a gap of 3/4mm I get big sparks.
If it not work, i have an bbq ignitor laying around.

[wyz2285]

Get a tazer, in my opinion if you want to have reliable fring from a non-mini hybrid.

[airpress]

We haven't that here. I will build further with this ignition. If it not works properly, i will swap to an bbq ignitor. I've already tested it in a normal combustion cannon. No misfires so far. I need to get the gap between 2-4mm. If its wider I get no spark.
But i've read here that the spark gap needs to be close as possible for a hybrid.

[MrCrowley]

Yeah you might have trouble with that ignition source, my stungun will jump about 20mm without problem but the gap between electrodes need to be less than 1mm inside the hybrid chamber for a 10x mix otherwise it doesn't ignite.

Also, you might want to put a ball valve between the chamber and the 0-100bar gauge. I'm not even sure what that gauge is there for, it wont do much good at measuring peak combustion chamber pressure as I think the rapid pressure spike could bugger it. If using the manometric method, you would want a 0-10bar gauge somewhere to measure the total pre-ignition chamber pressure when adding the air to the mix.

[airpress]

Small video of ignition with 2mm gap.

[youtube][/youtube]

@Mr Crowley: indeed, you have a point there about that 0-10bar manometer, I totally forgot it.
About the 0-100bar manometer, from where i bought it, they said its capable of measuring peak pressures, I will see what it does.
Maybe i have to install an check valve an ballvalve to release the pressure.
CHECKVALVE->MANOMETER->BALLVALVE

Also finished the ignition box.


And I've added also a Tee, the threadexopy is now drying. Pictures come when i've mounted the manometers. I've ordered them from Germany.

[wyz2285]

That spark won´t work for more than mix 3. And for a hybrid, under mix5 a big ass combustion probably has more power.

[airpress]

And will a flash circuit work from a disposable camera?

[wyz2285]

And will a flash circuit work from a disposable camera?

Won´t get you very far neither. Take a look at Petitlo´s hybrid thread, there are a couple of pages about ignition in the middle

[airpress]

After a long search on the web, I can get me a 350000 volt tazer. Will this be good enough for higher mixes?

[wyz2285]

yes.
message too short.

[airpress]

I aded a Tee like MrCrowley said.


Now, I will wwait till the ignition arrives.

[airpress]

350kV stungun arrived.
What an incredible spark, and I didnt expect that electric noise :p

Do I need to use special high voltage wires for connecting the stungun to the chamber?

[MrCrowley]

I use coaxial cable with a solid ~1mm thick copper wire in the centre because I've had other wires short out with each other at 10x mixes. It's probably a bit overkill but I was just working with the wires and cables I had at home.