I've been tempted to install an onboard glow driver to one of my planes. The circuit will go like this:
Use a single sub-C NiCad cell; the negative lead will be connected to one of the engine holdown screws. The positive lead will be connected to a mechanical switch and this to the glowplug.

The switch will be mechanically activated by a servo to close the circuit; the servo arm will physically push the switch to the on position and viceversa. This way the circuit is completely isolated from the receiver.

I have not heard of many people doing this, thus I'm afraid there might be some sort of risk to this setup... noise or whatever.

I'd appreciate your comments on the safety of this setup or on how to improve it.

I have one I made in two different planes. One I have flown about 1 1/2 gallons of gas through with a PCM receiver and the other just 4 tanks with a PPM receiver. The devices work very well and I don't think there are any interferences but I go out of my way to make sure the wires are away from the radio equipment which are also kept away from any metal pushrods or such.

Materials: I went to Sams Club and bought the rechargeable NiCad pack with 8 batteries and a charger for $20 (AA size) a battery holder and switch from Radio Shack and an old micro servo.

Setup: On the first plane I hooked it up to an external kill switch for safety (not needed unless you forget to turn it off) and on both planes the servo is slaved to the throttle to activate at 1/4 throttle and an auxiliary switch on the radio to turn it off.

Operation: After turning the electronics on I go to full throttle and trottle trim, prime, come back down on throttle till I hear the servo arm move on the switch (the cheap micros are noisy--that's a good thing) and when I flip the switch on the radio I can hear the switch engage. I start as normal and leave it on for about 45 seconds to warm up the engine then I flip the switch on the radio to turn it off and tune the engine.

I've used both the metal glow clip and the rubber one (newest) and I haven't had any problems but the rubber one is still new.

Good luck

I have been making my own glow drivers for years now after I got riped off on a manufactured one. Over priced for a simple setup. Go ahead and make your own. I have never had a problem with mine. Just remember you have to keep them charged.

Perdon!

Aqui tiene!

Wrong picture for the battery, I move it and the switch around for Weight and Balance.

I also had finaly come to the realization that I needed an onboard driver for my inverted 4 stroke. I did get it tuned to where it would not die on me, but I wanted the extra insurance.

I used a 1.2Vt cell from an old Rx battery pack, convieniently it still had the tabs on it after I broke it out of the pack to solder wires onto it. I used a small momentary button, and a spare servo with a spring swining off the end of a servo arm to actuate the button. I know this battery only has 75MaH, but It's only on at the start of the flight and below 1/2 or 1/4 throttle, and since I re-wired a chargeswitch, I can recharge it simply.

I use a Futaba 9C radio that lets me utilize the Thottle-Needle mix. I simply ran the spare servo from Ch8 and adjusted the mix and arm until the glow plug would light at below 1/2 throttle. The spring helps with not having to worry about adjusting the travel.