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Don't throw away your Generator!


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@nosky2high There is a question here (above^^^^), I believe is for you...   ?

I’m just cruising through reading and understanding.  This thread is about seven years old and gets dusted off every now and then...

It May take a decade before nosky returns back this way on his own... so I sent this invite...

Best regards,

-a-

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  • 1 year later...
On 2/5/2011 at 5:03 PM, Jerry 5TJ said:

I just finished the "eternal annual inspection" and test flew the 65C today.  Hurrah!

 

The Saga of the Generator:  

The generator seemed a bit loose so I put that on the squawk list for the annual last fall.  Turned out one of the bracket bolts was loose, so I took out the generator to get at the bolt.  With the generator out, I could see both brackets' holes were egg-shaped, so I took the brackets out and had them welded up so I could drill nice round holes again.  When I took the brackets out I could see the bolts were from the auto parts bin and not from Lycoming, so I bought new bolts with the proper drilled-for-safety-wire heads. 

 

Since the prop replacement about 20 hours ago, I've noticed something new with the generator mount on my C.  When I pull on the generator belt during pre-flight to check its tightness, I hear a new noise.  Pull-thunk.  Not loud.   Looking closer, I see that the upper bracket where it bolts into the crankcase is slipping under the bolt head.   I'm guessing that just like what @Jerry 5TJ observed, it must be egged.  It wouldn't move otherwise.   I guess the increased belt tension associated with removing and reinstalling the belt without loosening the generator mount probably loosened things up a bit.  I think the sound is the generator housing making contact with the front air shield.

This raises questions:

1.  Anything urgent?  It seems that a tiny bit of motion there doesn't likely represent a failure mode.

2.  Aside from welding/re-drilling the hole, does someone sell that part?

3.  What is the max. torque spec on that bolt that goes into the crankcase?   I put a wrench on it and snugged it a bit, but don't want to go too far.   Looked in the SMM and didn't find it.

Thanks,

Fred

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2 hours ago, 0TreeLemur said:

This raises questions:

1.  Anything urgent?  It seems that a tiny bit of motion there doesn't likely represent a failure mode.

2.  Aside from welding/re-drilling the hole, does someone sell that part?

3.  What is the max. torque spec on that bolt that goes into the crankcase?   I put a wrench on it and snugged it a bit, but don't want to go too far.   Looked in the SMM and didn't find it.

Yes urgent.

I was changing out the prop oil line (per the AD, 10 years ago) and found the aft hole in the generator mount broken.  It had been welded and broke again.  The prop line adel clamp hid the crack.  Dan (LASAR) sold me a new generator mount, much beefier thickness.  

Check the Lycoming manual for case bolt torque specs.  It’d be a bad thing to warp the mating surface and create an oil leak, or worse, induce a crack in the case.

  

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Let me clarify- it isn't one of the bolts on the bottom of the crankcase, it is the top one on the adjustment mount that seems to be a bit egged.  Moves less than 1/32".  This adjustment arm is the part I'm talking about, the same one that I think @Jerry 5TJ had the hole welded and re-drilled.

15 minutes ago, 47U said:

 

 

generator_mount.png

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12 hours ago, RLCarter said:

make sure the bolt isn't bottoming out (getting tight) before apply pressure to the bracket, an egg shaped hole shouldn't keep it from tightening down 

That is a great point.  Now that you mention it, that might be happening.  I'll give it a look.  Thanks!

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  • 3 weeks later...
On 10/9/2020 at 11:11 AM, 0TreeLemur said:

That is a great point.  Now that you mention it, that might be happening.  I'll give it a look.  Thanks!

Followup: the bolt was bottoming out.  In the absence of a shorter bolt, I added another washer and it tightened up nicely.  Thanks again @RLCarter.

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