Io 360 G/drive couplings

[Damon Banks]

GMAs,

Something you said in your last post really hit me.

"kinda wants to make the cam gear force the alternator gear out of mesh.. reason for the gear vibration and groan..."

ahhh this makes some sense. I've looked at the shaft after failure, and it is not a 'torsional' failure, rather a fatigue crack starting at the point where the diameter of the shaft steps down as it leaves the alternator. I couldn't figure how the shaft was snapping in this way if it were being loaded normally - the failure wasn't consistent with the forces.

However, as you say, the higher torsional load pushes the alternator drive gear further out from the accessory drive...now that makes sense, the bending of the shaft will cause the fatigue and failure I've seen.

As to alternator life - I'm more than happy to overhaul at the 500 hour life...I'd just like to get that long without having to remove it from the engine again! The last two failures have been within 250 hours!

Now, thinking about the loads being demanded, I don't know how well the alternators are sharing the load (or whether they're fighting), so I'd better install the IE volt/ammeter to see what's going on here. I don't have the flickering lights syndrome - well not anymore anyway - replaced most of the compontents on the front firewall some time ago and no trouble since...however, I do cycle the gear frequently (my normal stage length is less than 20 minutes between airports) - and I agree with you that it is a very high instantaneous current demand. What can I do to soften the blow to the alternators? How about huge capacitors on the gear circuit?

Damon