[AJCoholic]

I have been thinking a lot these past few days about this topic. How to kill (easily) our internal combustion engines. Not just those utilizing spark ignition, but also glow engines, diesels, and others.

One option I have been thinking about is a fuel shut off. Small solenoid valves are already in use in the model jet world, with every auto-start turbine using a pair of them (one for kerosene and one for propane, or two for kerosene if you have a kero start engine). They are small, reliable and fast acting.

So, why can't we invent a small unit, which would go in line with the fuel line feeding the carburetor, that holds the valve open until a loss of radio signal/ battery power is sensed then shuts off fuel supply.

The valve would be of course a normally-closed one, and would need to have battery power to remain open. Lose your battery? Shut down in seconds. Or you can use a radio channel to shut down as well.

The only drawback to this is that from what I have read, the solenoids (like the Jet-tronics I use in my Behotec engines) draw about 200 mA to hold them open. That seems like a lot of current, and I will try and check this out. But if something could be made, say, drawing what a regular servo would average - it would be practical.

No one steal my idea, now... I seriously want to work on something like this. Who knows where it may lead!

AJC

[Mike Sebastien]

I think you are on to something. It's a great idea.

Put it together and then go on Dragon's Den to get seed money!!!!!

[JohnnyS]

One way to do it would be to install one of these, connected to an unused channel:

http://www.dawnmist.demon.co.uk/rcm.htm#5
http://www.hobbyoutlets.com/store/ho...-duratrax.html
http://electrodynam.com/rc/EDR-119/index.shtml

Then plug in a micro server attached to a link that would do one of the following:
1. Pull the fuel line off the carb or remote needle valve if the power fails.
2. Trigger a spring-loaded fuel cutoff to pinch shut the fuel line. A lot of the old control line and free flight guys can remember these. Examples:
http://www.brodak.com/shop_productde...ProductID=5831

Advantages: No significant current draw while the system is operating normally.

[Daren71]

Some of the pylon racers use a small piece of wire looped around the fuel tube. The wire runs through a small hole in the firewall, the fuel line runs near the firewall, when you want to kill the engine, the wire tries to pull the fuel tube thru the small hole, which isn't nearly big enough, and cuts off the fuel flow. I'll try to find a picture of it later. Daren

[E Smith]

Like this you mean. The wire pulls the fuel line into the tube and pinches it off. In this installation the tank is facing backwards for a special reason.

Ed S

[AJCoholic]

JOhn,
The failsafe you posted (#1 and #3) say they will bring your throttle to failsafe when the battery gets disconnected. I imagine it will use the last bit of power to do so until it is completely depleted.

I am thinking of a device that will reset to a shut of position with NO battery power, ie, if the battery suddenly fails or becomes disconnected.

The loop or wire, certainly will work and that I have used to kill Diesels without a throttle in some of my old timer SAM models. But again, you need a properly functioning radio to work.

AJC

[kip51035]

Over a year ago I purchased a .40 size fan unit and it only had an exhaust slide and a S.O.V.. You can buy electronic switches that replace a servo and plug in the same spot. My experience with pinching off the fuel is that when the engine is near idle it seems to take for ever to shut off. I timed one engine it ran for 38 seconds after I pulled off the line. At that length of time the emergency has time to happen several times over. When you close the throttle the engine dies right away. If the radio is not working then all this is a waste of time. Having a separate radio for engine shut off, I could have a lot of fun with that. I am one of those guys that take garbage cases home and I listen to the story that caused the crash and almost always is no fault of the radio. In most cases a proper before flight inspection would have prevented the crash. In some cases the pilot or builder did not know any better.

Kip

[RAMJET]

I don't know if it will kill the motor fast enough ,a coupple of seconds is a long time when pointed down with no controll or running through the pitts.would be a good back up system to the ignition though.or you could have the choke plate close the same way hooked to a solenoid ,would be a faster kill .time to do some testing .intresting idea .Roger

[AJCoholic]

Well, I have some plans to rig up a system and test it out. If nothing else it will show why this isnt used (if it doesnt work well that is).

Rarely does an accident happen with the engine idling... its generally flying at 1/2 throttle and up, isnt it

AJC

[JohnnyS]

Cool!

Please let us know what happens.

Originally Posted by AJCoholic

Well, I have some plans to rig up a system and test it out. If nothing else it will show why this isnt used (if it doesnt work well that is).

Rarely does an accident happen with the engine idling... its generally flying at 1/2 throttle and up, isnt it

AJC