Need failsafe for gas engine-make my own??

[POPEYEBOB]

Hi,I need a failsafe for a gas boat .I want something that will ground out the ignition on a Zenoah gas engine if it senses ANY failure.I used an old servo driver board, wired it "hard over", and connected the leads that went to the motor to a 5v relay.I had to use a 100uf cap across the relay coil to smooth out the pulses.It works. If you turn off the transmitter, loss of signal means no power to the relay coil, and the relay drops out. Of course it drops out too if the battery voltage goes down, or you loose battery completely.When the relay drops out, it grounds the ignition lead, if the rerlay contacts are held in, the lead is open to ground.The problem? it draws 60ma in operation. Anybody know of a better way? The zenoah has a grounding lead coming out of the coil, but I dont know what the current or voltage might be.I am trying to prevent a runaway if I drop the transmitter in the water, or the onboard pack fail's.
Thank's.

[fhhuber506771]

You can buy a failsafe for a single channel to go between the RX and the servo... on loss of coherant output from the RX it drives the servo to the preset position. (sound exactly like what you want? you can put it in any channel and make the servo do anything you want when it takes over.)

I'll do a little looking in Model Aviation... I know I have seen ads for them. (but I haven't needed one.. I had PCM.) Actually... now that my PCM rdio is dead.. (TX failure) I may want to get 3 or 4 of the things myself because throttle failsafe is ALWAYS a good idea.

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Can't find it n Model Aviation... but Google is great :D

http://www.rc-cam.com/rcfs.htm (oops.. not a kit... just instructions... should be a kit out too... most stuff from this guy is also kitted somewhere.)

a trick that should work for the loss of power to the RX... (and about the only way to drive a servo if the power to the RX is gone...) is to clip the red lead between RX and this device... then wire a separate battery (smaller and packaged with the affected servo and the failsafe all in thier own waterproof box n your case) to power the failsafe and servo.

Of course... you can't 100% protect from all possible failures... in reality.. just adding the failsafe between the RX and a servo to operate a high amperage rated microswitch (they aren't necessarilly small) in that ignition short circuit would do what you NEED. If you lost the battery power to your RX in a collision... you probably have sufficient damage that the engine is at the bottom of the pond anyway.