B&C Boss mount alternator...

[Michael Burbidge]

I know that my questions are coming fast an furious, since I got my engine hung. I'm entering territory where there are little or no instructions.

My engine is an O320-D3G and it came out of a certified aircraft. It had a large certified alternator on it (pig-n-pancake), made by Chrysler, interestingly enough. I purchased a B&C 40 Amp alternator to replace it. I thought it would be a direct replacement for the certified alternator. The certified alternator is boss mounted and so is my new B&C alternator.

When I took the old alternator off and tried to put the B&C alternator on, I immediately noticed that the mounting brackets were very different. The old brackets consisted of three separate brackets, not including the tension arm. First there is a U-shaped bracket that the alternator hangs directly below. This is made of 3/16 inch steel. There's similar L-shaped bracket behind that, that attaches to the case with three bolts. And then there is a short, flat bracket that ties the alternator and the starter together. Here's a picture of the old brackets that mount to the engine case and starter.



The B&C boss mounted alternator comes with a single, U-shaped bracket that the alternator hangs directly below. It has longer arms, than the old U-shaped bracket. Here's a picture of that bracket. It is made of 1/4 inch steel.



Obviously the flat bracket that ties the alternator to the starter will not fit, it is too short for the new U-shaped bracket.

So my question is, how did you mount your boss mount B&C alternator? Did you just remove the L-shaped bracket behind the U-shaped bracket? Did you skip the flat bracket that ties the alternator to the starter?

I'm guessing that the light-weight alternators do not need the same level of support as the old heavy alternators did.

Thanks for any suggestions you might have!
Michael-

[Geronimo4497]

I assume this engine came out of a Warrior?

Those old Chrysler alternators were not balanced and had the nasty habit of breaking the single mounting brackets.

I imagine the B&C is nicely balanced? I think you'll be just fine with their supplied bracket.

[Michael Burbidge]

Yes it did indeed come out of a Piper Warrior.

[Geronimo4497]

That alternator to starter bracket was a Piper mod. You should be fine without it.

[Michael Burbidge]

I'm not a mechanical engineer, but after installing it with the single B&C bracket, plus the tension bracket, it is very solid. It is so light and small compared to the old beast of an alternator that came with the engine. I feel pretty comfortable with the install.

Thanks,
Michael-

[Geronimo4497]

Make sure to put the flywheel on (ideally the prop, too) and make sure you have proper belt alignment. There shouldn't be any fore or aft pressure being applied to the alternator pulley.