Alternator Failure

[judoka5051]

While on the subject of alternators, I have an issue, and hope you guys can help. Let's say a 'friend' has this plane... Anyway, the front alternator mounting hole on the engine case is ruined. I,,, I mean my friend, didn't notice it on the pre-buy exam. Can an alternator be mounted safely using the remaining 3 holes? The plane currently has a pad mounted low-power SD-8. So, if necessary, that can swapped for an SD-20.

Thanks, and you guys rock!

Lance

[lrgabriel]

Originally Posted by Bluelabel

How do you measure? What tool and how?
Thanks,

Lycoming SI 1129D (07/23/15) talks you through the three applicable methods of checking belt tension.

[RONSIM]

is currently doing the job, and you just want a few more electrons, the SD-20 is and easier solution --- I installed one as a "standby" and it is pretty straightforward.

Ron

[aerhed]

Are you talking about the forward of the two holes that attach the saddle bracket to the case on a flat pad surface?

[judoka5051]

The mounting pad for the bracket has 4 holes in a line. The hole farthest forward is ruined. So, just the three are useable.

Thanks, Lance

[aerhed]

4? Hmm. They're typically mounted with 2 bolts. Parts catalog calls for STD 1838 bolts, quantity two.

[BillL]

Originally Posted by aerhed

4? Hmm. They're typically mounted with 2 bolts. Parts catalog calls for STD 1838 bolts, quantity two.

Are helicoils approved for repair? Any special profile on the shoulders of the drill bit?

[Kevin Horton]

Originally Posted by Bluelabel

How do you measure? What tool and how?
Thanks,

Those values are the torque on the alternator pulley that will cause the belt to slip on the pulley. Find a socket that fits on the big nut that secures the pulley, and put your torque wrench on it.

For a new belt, set a click type torque wrench to 11 ft-lb (132 in-lb), and it should click without the belt slipping. Then set the wrench to 13 ft-lb (156 in-lb) and the pulley should start to slip on the belt before the wrench clicks. If you have a beam type torque wrench, the belt should start to slip when the torque is between 11 and 13 ft-lb. Adjust the tension as required until it passes the above test.

For a used belt, replace the above values with 7 and 9 ft-lb (84 and 108 in-lb).

[N941WR]

Originally Posted by Gary 40274

Do we have any consensus about what fails. It would be nice to know wether it is diodes or bearings or insulation of the windings that fails. Inquiring minds want to know

Gary Specketer

No yet. My PP alternator will be dropped off at a local "rebuilder" and I hope he can give me some answers.

It doesn't feel like the bearings went bad as it spins as easily as the Suzuki alternator I bought, that may or may not go in the plane.

There is a lot of black dust on it, so it might simply be the brushes, or the diodes, or the ...

I'll post when I know more.

Bill L., I received your email and will try to get all the details on make, model, size, etc. as well.

[N941WR]

Originally Posted by aerhed

4? Hmm. They're typically mounted with 2 bolts. Parts catalog calls for STD 1838 bolts, quantity two.

It depends on who's bracket you are using. The milled (?) aluminum bracket from Van's uses all four holes and the U shaped steal bracket from PP uses the front two.