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  #1  
Old 07-14-2019, 06:40 AM
rbibb's Avatar
rbibb rbibb is offline
 
Join Date: Jun 2006
Location: Freericksburg, VA
Posts: 626
Default Alternator Pulley nut.

Ok I had my Plane Power 60 amp alternator pulley nut come off in flight. The pulley remained but the belt got trashed, etc. the good folks at Hartzell send me a new nut gratis but had no info on how to otherwise repair.

The unit is based on some model Nippo Denso oem model but no joy finding any info there.

The question is: How does one torque this nut? There is no way to hold the shaft while torquing the nut. I?ve removed rear cover, etc. to see if there was some access from the rear. No joy.

Unit has performed well other than this unusual incident.

All opinions welcomed and respected until proven unworthy.
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  #2  
Old 07-14-2019, 07:29 AM
cojaken cojaken is offline
 
Join Date: Oct 2005
Location: Tulsa, OK
Posts: 90
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Is it possible to hold the pulley with a strap wrench while torquing the nut? Same method as when you put a drive gear on a magneto.
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  #3  
Old 07-14-2019, 07:41 AM
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rbibb rbibb is offline
 
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Location: Freericksburg, VA
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Quote:
Originally Posted by cojaken View Post
Is it possible to hold the pulley with a strap wrench while torquing the nut? Same method as when you put a drive gear on a magneto.
The pulley isn?t keyed to the shaft, it?s just clamped in place by the nut. That was what I originally thought would work. No key, no joy.

Going to try impact wrench...we shall see.
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  #4  
Old 07-14-2019, 08:26 AM
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koupster koupster is offline
 
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Location: SLC, UT (KBTF)
Posts: 380
Default Yes, impact wrench

You can use the belt wrapped around the pulley to make a temporary strap wrench while you use the impact wrench. Best to use a glove on the hand holding the belt.

Cheers, David
KBTF A&P
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  #5  
Old 07-14-2019, 09:24 AM
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pilotkms pilotkms is offline
 
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Location: WARNER ROBINS, GA
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I took my spare clone alternator to a shop to have a new pully installed. The guy used an air-impact driver to remove and replace the nut. No other way I could see to do same.
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  #6  
Old 07-14-2019, 10:40 AM
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fl-mike fl-mike is offline
 
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Yup, the impact wrench is your friend in these situations.
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  #7  
Old 07-14-2019, 10:46 AM
N40ES N40ES is offline
 
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Location: Maryland Eastern Shore
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Red face Missing NUT

During last Condition Inspection the A&P noticed the large nut missing from Alternator Pully. Pully was tight and working fine. Really NO idea how many hours ago it departed. Called Hartzel and was advised: We can sell you another nut but we prefer you send that Alternator to us to have the Nut. We need to inspect that shaft before installing another nut too. I sourced another new Alternator with two delivery and replaced the whole thing. (Guess 'Im too impatient! )
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  #8  
Old 07-14-2019, 01:31 PM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Quote:
Originally Posted by N40ES View Post
During last Condition Inspection the A&P noticed the large nut missing from Alternator Pully. Pully was tight and working fine. Really NO idea how many hours ago it departed. Called Hartzel and was advised: We can sell you another nut but we prefer you send that Alternator to us to have the Nut. We need to inspect that shaft before installing another nut too. I sourced another new Alternator with two delivery and replaced the whole thing. (Guess 'Im too impatient! )
Given two different folks have had the nut come off new alternators, I would say the method the manuacturer is using to torque it is flawed and would zip it on with an impact instead. No sense shipping it back to have the same flawed method done again.

I believe the shaft has a morse taper and if the pulley is still on the alternator, it is being held by it's taper fit. and no damage has occured. These are pretty binary. They are either tight and don't move or loose and come off, without a nut.

Larry
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Last edited by lr172 : 07-14-2019 at 03:30 PM.
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  #9  
Old 07-14-2019, 04:25 PM
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rbibb rbibb is offline
 
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Quote:
Originally Posted by fl-mike View Post
Yup, the impact wrench is your friend in these situations.
Yeah... trip to Harbor Freight for $22 impact wrench and 20 minutes later problem solved.

Test flew it an hour today and all seems to be holding together ok.
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  #10  
Old 07-14-2019, 05:18 PM
Marc Bourget Marc Bourget is offline
 
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Location: Stockton, California
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Maybe put some "tattle tale" paint and check often ???
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