bryan1, the rpm of the nitro engine is more like 30-40,000.
But still, thats below 1000 rpm per second.
The flywheel is approx. 50mm in diameter and approx. 5mm thick (haven't measured it though).
I have thought about the anneal thing, but I don't know how to do it (it's something about heat up and down, slow/fast ect.). If I do that, I'll drill 1 or two holes (two to balance it) and use an optical interrupt switch (don't know if there is an optical interrupt switch with 6-7mm gap out there). Since the flywheel is steel, it will respond to magnetics and then I'm not sure you can use a magnet in a hole.
And of course I will use a PIC to count pulses, that's not a problem :wink: The problem is the mechanical-to-electrical "conversion" :roll: