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Today, we have been chasing down the high-RPM vibration/thrum coming down Zouave’s transmission tunnel. Having seen this on a tii he worked on some years ago Stevenola suggested it might that the ears on the alternator mount had pulled forward so that the alternator belt is slightly angled on the pulley.  Not enough to shred the belt, but enough to set up a harmonic.  

 

We pulled my ebay 85 amp alternator, Steve heated and ever-so-slightly straightened the mount ears.  On inspecting the ebay 85 amp alternator we noted that: (1) the 100mm through-bolt holding the alternator on the mount was bent, (2) the only mount hole on the alternator that takes a bushing is the adjustment bar mount (the others are just bolt-through), (3)the bushing-washers on the adjustment bar mount ride on the surface, and do not insert into the mount holes — because the mount holes are too small, (4) the metal adjustment bar bushing itself has about 1mm of play inside the mount hole (it has a 15mm OD, and the hole has a 16mm ID), and (5) the bushing washers are floppy neoprene.  Altogether, plenty of reasons for the alternator to pull over a bit on tightening.  Not to mention to create more vibration!

 

You can see the difference in the alternator mounts here, with the original tii alternator sporting red bushings in both holes.  The holes behind those bushings are bigger in diameter than on the ebay 85 amp alternator and the stock alternator has a thicker dimension at the holes so that the bushings are largely recessed.  The ebay 85 amp alternator has a flat plate in which the hole is 16mm ID

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The extent of today’s progress?  Perfectly straight mount reattached to block:

9AB12037-F60B-47C0-B94E-23704580B49D.thumb.jpeg.0271cde6b18c25c1806fb4c2f5a412b6.jpeg

 

The plan:

  1. New through-bolt for the alternator-to-block mount to avoid deflection there.
  2. To get rid of the 1mm rattlespace between bushing and hole in the adjustment bar mount:
  • I have sourced a length of bronze tubing with 15mm ID and 16mm OD, and will press a length of that into the mount hole.  The bushing should then at least fit tight to the hole.  I’d source a urethane bushing with a .5mm thickness, a 15mm ID and 16mm OD if there were one available in the whole world. That would provide some dampening, at least.  We thought about using super-thin PVC, but not sure how that would hold up or how well it’d dampen vibration.
  • I will cut down two of my Ireland urethane bushing inserts to flat washers to replace the existing neoprene, in order to get less compression and therefore less deflection at that critical point.
  • Other things that come to mind include: finding some hard-wearing durable plastic-y substance (other than JBWeld) that could be used to fill the voids where bushings might, like in gthe through-bolt channels and in the 1mm void around the adjustment arm mount bushing.  There’s not enough metal to drill out the adjustment arm hole to accomodate stock bushings, and anyway the metal’s not deep enough to accomodate them.

Frankly, my planned fixes look like real compromises compared to the stock tii setup. Not having urethane bushing washer that totally isolate the bushing from the mount clearly is going to leave Zouave with more vibration than the stock setup.  I see no really good solution but am all ears if someone knows a way to improve on this plan!

 

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‘74 Fjord 2002tii (Zouave)

’80 Alpenweiss 528i (Evelyn)

’05 R53 Chili Red Mini S

‘56 Savage Model 99 in .250-3000

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19 minutes ago, 2002iii said:

You might be able to swap the guts of the Ebay alternator into your old case.

Good idea!  We discussed it briefly.  Maybe just the front half of the case if the bolts line up…. It’s got different wiring (internally regulated) so I am trying to find other ways to win before I go down that rabbit hole.

 

Speaking of which, I was wondering: what model does this ebay 85 amp alternator come from, anyway?

‘74 Fjord 2002tii (Zouave)

’80 Alpenweiss 528i (Evelyn)

’05 R53 Chili Red Mini S

‘56 Savage Model 99 in .250-3000

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