Re: _CD Ignition_

Good morning Kevin.

Don't think an alternator is needed to power a properly designed CD Ignition system. Attached is a complete
CD Ignition system for reference, including construction and parts info. It is a DC to DC Inverter type circuit.
This circuit claims EMI noise is filtered, which is helpful for the aircraft power bus, especially if running sensitive
electronic devices.
The battery supply is stepped up to 300 Vdc through a multi vibrator stage using a transformer and the charge is stored in a 275 Vac capacitor and then dumped to the coil(s) by mosfet switches in half bridge configuration. Lots of testing would be needed to confirm reliability.

Hope this info helps move forward the rotary engine ignition system.

George M


I have one of those George. I fooled with it for many hours.
It worked for awhile. It was unreliable.
The switching power supply experts say not to use push pull primary circuits as
a slight unbalance in the transformer cause them to fail. Or something to that effect.

It is also a real old chip and newer chips are better.

Paul Lamar



Thanks George- my initial thought was that it might be possible to tap the output of the alternator at the same location where the rectifier diodes pick it up. We could pull the AC from there, step it up and charge the caps with it. While I like the self contained units that Paul is working on that do not need a battery to run, I am also a USCG Captain that spends lots of time in a boat. My experience with the marine CD ignitions is that you need a boat with at least 3 engines on it to be sure you will get home. I cant count the times I came back with one engine up and more than  one instance 2 of the 3 up. Most of the problems were with the Mercury systems, but I had a boat with 3 Yamaha engines on it that had similar issues. My boat now has 2 big detroit diesels in her. Mechanical simplicity and reliability.

As far as commercially available plentiful CD ignitions, I would have to assume that marine engines would be far more suited for aircraft applications- my engines ran at 5000 rpm from startup until I got back to the dock except for time spend trolling on one engine. Yet even with this level of design and engineering there were many many problems. The Vespa isnt designed for continuous 5000 to 6000 rpm running, so that makes me skeptical. I am not at all convinced that this technology is ready for prime time for a plane.

I do believe in the concept if it can be kept simple- alternators run for hundreds of hours without issues (usually) and they make AC power. After this there isnt much of a leap involved to make CD ignition functionally reliable. The system with the crank mounted coils, all the way through to the end I agree would need much testing.

KA





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