I'm quickly approaching the point where all the major airframe systems are done, and the major systems left to build are getting smaller. I've got to make one more wing skin, and then I won't have any more major layups except for the engine cowling, so yesterday I ordered a Megasquirt engine controller. I'll work on getting it built while I finish the electrical, panel and canopy installations.

I'm investigating using two Ford EDIS ignition controllers. They will work without computer input, set for 10 degrees of advance. It just needs a power source and input from a vr sensor. In normal operation, the computer sends a correction signal that the controller uses to change the spark advance. One EDIS would be set to control the leading plugs with a wasted spark, and the second would control the trailing. It promises to be a very robust setup with multiple redundancies.

I still need a toothed wheel for the vr sensor. The EDIS system requires a 36-1 wheel (36 teeth with 1 missing). I'm thinking that one of the old bicycles that my boys never use may end up missing a chain sprocket. (As a nod to the original homebuilders, I think every homebuilt airplane should include at least one bicycle part.)
echristley@nc.rr.com

Enerst ChristleyChanging the subject line to make John and the archive buffs happy 8*)

George Lendich wrote:

    Ernest,
    I can't remember what the Mazda RX8 timing wheel looks like - might it do the job? I've been looking for mine, I have put it away and now can't find it. Failing that you might get one laser cut.
    George (down under)

Dang this airplane building. I swear it's a curse.

11:00 at night an I've got half a bottle of Pinot Grigio from North Carolina's very own Biltmore Estates in me, but a simple question sends me out into the humid night air with a flashlight to fight off mosquitoes while I count the teeth on bicycle gears.

The front middle gear on both of the bikes at my house have 34 teeth. The Ford EDIS ignition needs 36 (you'd have to grind off one tooth). I'll have to check with a bike shop to see what oversized gears look like. They'll give you these things, because they do wear out (my official reason for not pedaling mine around more often). The way they wear out makes it so they can't hold onto the chain, and will have no effect on what we're using them for. All we really want to do is throw some metal in front of a variable reluctance sensor in a timely manner.

I don't know how many teeth the RX-8 wheel has, but I do know that it uses the opposite logic from the missing tooth method. It uses the bridged tooth. But, heh, I'm a southern redneck, ya' see, and around here missing teeth is a tradition! Course, the missing tooth output could be made to look like the bridged tooth output with an inverter and shifting the sensor over by half a tooth.

You can test the vr sensor and timing wheel by chucking the wheel in a drill press and jigging the sensor next to it. Attach an o-scope to the sensor output. You'll also be able to tell what the tolerances are on the spacing between the vr and the wheel.