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hybrid 4.5mm

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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hybrid 4.5mm

Unread postAuthor: ghostbuster » Mon Oct 05, 2009 1:54 pm

hi, i want to make a hybrid cannon with a 4.5mm pellet barrel, a map sensor, a propane or butane sensor, microcontroller, electric ignition , air pump and a pneumatic valve for the butane/propane tank.I want to know the chamber size that i've need for this barrel.
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Unread postAuthor: qwerty » Mon Oct 05, 2009 2:01 pm

Before you attempt any of this i would advise you to do some research on hybrids because it sounds like you dont know what your talking about. What do you mean by a MAPP sensor a MAPP meter? What are you thinking of making of? and what x mix.
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Unread postAuthor: ghostbuster » Mon Oct 05, 2009 2:07 pm

The map sensor will measure the air/fuel Pressure, and the butane or propane sensor will measure the fuel ratio.I don't know the mix i am waiting for ideas.
The microcontroller will start/stop the valve from the fuel tank and the air pump of the tyre inflator until the mixture and pressure will me right
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Unread postAuthor: qwerty » Mon Oct 05, 2009 2:11 pm

you dont need any of this and if you know what you are doing why would you need to measure the mixes if they are all ready at the right mix before check out spudwiki. Also why cant you just turn the compressor of instead of using a "microcontroller" why not build something simple like a large combustion gun it sounds like you dont know what you are doing. Take things one step at a time rather than going straight into complicated stuff.
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Unread postAuthor: ghostbuster » Mon Oct 05, 2009 2:26 pm

ok, then so what its the correct fuel/air mixture? i realy want to use de 4.5mm barrel
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Unread postAuthor: Moonbogg » Mon Oct 05, 2009 2:35 pm

You mentioned several fuel types and sensors for them. Not to offend you, but your choice of words has succeeded in confusing the crap out of me and I have built 2 hybrids. You absolutely MUST research this stuff on your own because only you can come to your own understanding of how these work. If you do it wrong dude you're going to get hurt.
Have you ever built a metered spud gun? I suggest at least building a metered pellet gun based on 1x fueling and then perhaps build or convert it into a hybrid once you have a sound understanding of basic function.
There is a program called HGDT that you can use to determine your barrel and chamber size for both standard and hybrid combustion cannons.
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Unread postAuthor: ghostbuster » Mon Oct 05, 2009 2:54 pm

I have mentioned two fuel types because i don´t know wich one is better, And yes i have made a combustion spud gun without meters, but the PVC pipes here in Portugal are very weak...
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Unread postAuthor: MrCrowley » Mon Oct 05, 2009 4:26 pm

Can't you work this out for yourself? Having a 4.5mm barrel means you only need a pretty small chamber, and for the fuel mixture, check the topic HYBRID FUELING 101 for information on how to calculate the mixes.

If you can't figure that out from the topic, you haven't done enough research.
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Unread postAuthor: ghostbuster » Mon Oct 05, 2009 6:20 pm

Ok, i´ve understand really bad the fuel air injection that you are using.You inject the fuel in the meter pipe.. to measure the pressure, then you let him go to the chamber, after that you do the same process with the air.
But i want to know if will work with my idea that is to connect directly on the chamber, a pressure sensor(MAP, like one used in some cars ECU), and a propane sensor.The information of the sensor will be showed on a lcd display, and the quantity of air/fuel it will be adjust with the solenoid valve connected to the propane tank and tyre inflator air pump.
Sorry about the mess with electronics but i want something very hi tech :)
I´ve also reading the hybrid fueling 101 but its a little bit confusing for me to work with inches.
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Unread postAuthor: Mr.Sandman » Mon Oct 05, 2009 6:59 pm

ghostbuster wrote:Ok, i´ve understand really bad the fuel air injection that you are using.You inject the fuel in the meter pipe.. to measure the pressure, then you let him go to the chamber, after that you do the same process with the air.
But i want to know if will work with my idea that is to connect directly on the chamber, a pressure sensor(MAP, like one used in some cars ECU), and a propane sensor.The information of the sensor will be showed on a lcd display, and the quantity of air/fuel it will be adjust with the solenoid valve connected to the propane tank and tyre inflator air pump.
Sorry about the mess with electronics but i want something very hi tech :)
I´ve also reading the hybrid fueling 101 but its a little bit confusing for me to work with inches.
on a side note where are you from? But on topic I slso have no idea what you are trying to say.
And really? an lcd screen thats a bit much for something that simple. Why an lcd? everyone knows gauges are the way to go. but 13 mm chamber to 25mm chamber will do. sorry if the numbers are messed up as i use inches.
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Unread postAuthor: ghostbuster » Mon Oct 05, 2009 7:20 pm

I am from portugal
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Unread postAuthor: CS » Mon Oct 05, 2009 8:38 pm

From testing done by Burnt Latke the optimal propane portion is 4.2% . And at a generalized atmospheric pressure, 14.7psia (0 psi/g for gauge) there is 20.9% Oxygen.

...so, in a 1x combustion launcher there is around 3.0723psi (20.9%) oxygen, and .6174psi (4.2%) propane.
5x hybrid: 15.3615psi oxygen 3.087psi propane
10x hybrid: 30.723psi oxygen 6.174psi propane

Issue is, how accurate are your electronic meters? Oxygen could be injected straight into the chamber because of its higher pressures, but propane would be more difficult because there is less of it. That said I'd think the idea to inject oxygen directly to work, (regulator> flashback arrestor> solenoid valve> check valve) but the propane would need a meter setup.
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Unread postAuthor: Technician1002 » Mon Oct 05, 2009 11:26 pm

Most flammable gas sensors are cross fuel sensitive, but calibrated to the gas they are set up to detect. For example a propane leak detector for a motor home will also detect gasoline, butane, alcohol, and hydrogen. Most of the flammable gas detectors use the same sensing element, a heated bar of silicone. Hydrogen penetrates the semiconductor and makes it conductive.

One of these could be calibrated to directly sense the mix in the chamber so propane can be injected and mixed and the level brought up to the proper mix.

For hybrids, I'm not sure if the sensor is volumetric or percentage, so at higher mixes, the calibrated point for 1 atm may be invalid for a 5x mix.
http://www.buy.com/retail/product.asp?sku=211275512&listingid=45609023

In spite of the cheesy go/no go display on an inexpensive consumer sensor, the sensor chip output is an analog signal that can be measured with a digital volt meter for reasonable precision for repeating known mix values. The sensor would care less what the chamber volume is. I works on the amount of flammable gas present in the air.
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