Late in June I sent away an oil sample for spectroscopic analysis.
The last time I did this was in 2003, shortly after Melmoth 2 had begun flying.
Lacking a belt to damp the torsional vibrations of the engine, the direct-drive alternator requires a flexible coupling between its shaft and the gear that engages the accessory drive.
I've seen flakey behavior in the charging system before, including on the previous flight, but always the system would pull itself together after a few minutes and do the expected thing, that is, initially indicate a charge as the battery recovers from starting the engine, then gradually drop to zero charge or close to it and maintain a steady 28 volts.My supposition about the function of the wildly expensive coupling between the alternator and its driving gear was apparently incorrect.According to the technician at Aero Accessories from whom I picked up the overhauled alternator this morning, it's just a plastic connection designed to avoid dropping metal fragments into the engine in case the link fails.The pipe looks as though it ought to be able to be put in either way, but actually the flanges on the two ends are of different types, one thicker than the other, and the flanges on the mating parts are as well.It turns out that you have to mix, not match, to get the clamps to work; if you put the two thicker flanges together, the V-groove can't handle them.Tomorrow I will take it to Aero Accessories at Van Nuys, where I bought it in 2011, for repair.What was surprising, and instructive, about this was that I had inspected the alternator before taking the airplane to the mechanic, and noticed nothing; but my attention was directed to the wire connections, and since the alternator itself was ostensibly intact, with all its bolts and screws and safety wire in place, it never occurred to me to grab the end of it and shake it to see whether it was coming loose from the rest.I made an appointment with Able Air (where I used to hangar Melmoth 1 in the Bob Eeg days) to troubleshoot the system on Wednesday.I tested my old epoxy a few days ago; it's still good.Realistically, however, I think I would be satisfied with 30 inches at 18,000 feet, which would provide 75% power. in., so we get 348 pounds of pressure trying to blow the tanks off the intercooler.Being more frugal than impatient, I never use even that much anyway. I put the alternator back into the plane on Saturday.