I have seen glow drivers that rely on using a radio channel to work.
Would there be any problems in setting up a mechanical (electric) switch to juice up the glow plug when the throttle reaches a determined position?
I am thinking of those micro-switches that have a spring to keep them open and then if you depress them they close the circuit.
I am also afraid that the switching will produce radio interference...
Of course, I can test empirically but... if somebody else knows about it... that's why we are here for....
Albert

I think thats how they all used to be. The CUB I saw one on simply had the throtle pushrod running next to the micro-switch. Then there was a thicker section on the throotle pushrod to power up the glow driver at 1/2 throttle or less. this plane also has a red light on the dash that is on when the glow driver is hot. The owner says this thats his warning light. He knows not to choke it when the light is on. There is also a switch to turn the hole system on or off. Later daveo

That's how we did it back in the old days. The microswitch method works just fine, just takes a little bit of time to set up.

I use a micriswitch from Radio Shack which has a lever and mounting holes spaced the same as the screw holes on a standard size servo. A spacer and long screws brings the switxh up, and one of the large round output "wheels" is carved into a cam, then drilled fot connecting the throttle pushrod. (yep, I set where in the servo travel the switch is on, then I set up the throttle pushrod.)

I set the cam up to have the kill position on the TX also turn the glow back off... Glow is on from: low stick +2/3 trim, to: full trim + 1/4 stick. (not really hard.. mount the switch, positiin the servo, mark the servo wheel... move the stick and mark again, THEN cut the cam.)

My charging jack for this rig is between the battery and switch, allowing me to plug in a booster when on the ground.

Thanks, guys...
I guess I will use it that way...
I wonder... why make things complicated when a nice hack will do.... and cheaper also...
Albert[img]i/expressions/face-icon-small-wink.gif[/img]

You want a constant-on system...

You could gain some plug heat, eliminate the microswitch and extend the cell's life by putting a resistor between the on-board battery and the glow plug. A paralleled jack to plug in a booster for starting (booster doesn't have the resistor between it and the plug) off you go.
The question becomes... What value and type resistor? The answer is a low resistance, "current limiting" ceramic type... measure the resistance of a glow plug and look for 1/2 that value. (you still get appx 2/3 the current that way. {E=IR => I=E/R With E constant, If R2 = 1.5 * R1 then I2 = I1 / 1.5 = 2/3 * I1} )

The purpose of the on-board glow is to prevent the plug from getting too cold... doesn't take as much current for that as it does to start a cold engine. You won't be burning out plugs, and the on-board glow will last longer per charge. (and on hot days... it might be enough to start the engine without the boost)

Constant electric power to the glow plug and full throttle can lead to premature plug failure. The rich setting we use on the ground would protect the plug some... but in flight it leans out, and its all too easy to overheat the plug element. (I have tried the direct, no switch system. Burned out an O.S. #8 plug each flight.)