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  #1  
Old 02-16-2020, 12:20 PM
markelliott markelliott is offline
 
Join Date: Jun 2018
Location: minneaopolis, mn
Posts: 32
Default Prop Governor studs PSA...

On the T-Bolt 390, Lycoming will install their 31c-16 studs (2") and they should have a nominal height above pad of 1.25-1.31". Unfortunately mine were run into 1.19-1.21".


In any case, the Hartzell governor, gasket, washer, lock washer and nut add up to 1.346.


You will not have a full thread out of the nut.


The next stud size is a 31C-17 - .125 longer than the -16 and will need to be ordered and changed out.


Maybe ask and see if they would install the -17 studs during the build?


I have a feeling many previous builders just installed as is, changed to the thinner washer, or ?


Lycoming customer service has been very good, FYI
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  #2  
Old 02-16-2020, 12:54 PM
MED MED is offline
 
Join Date: Jul 2015
Location: Aiken, SC
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Quote:
Originally Posted by markelliott View Post
On the T-Bolt 390

I have a feeling many previous builders just installed as is, changed to the thinner washer, or ?
Perhaps, they have changed? I checked photos of my installation and there are at least 2 threads showing. I received my engine in 2017. Thanks anyway for the heads-up.
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  #3  
Old 02-16-2020, 03:31 PM
lr172 lr172 is online now
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 4,714
Default

Quote:
Originally Posted by markelliott View Post
On the T-Bolt 390, Lycoming will install their 31c-16 studs (2") and they should have a nominal height above pad of 1.25-1.31". Unfortunately mine were run into 1.19-1.21".


In any case, the Hartzell governor, gasket, washer, lock washer and nut add up to 1.346.


You will not have a full thread out of the nut.


The next stud size is a 31C-17 - .125 longer than the -16 and will need to be ordered and changed out.


Maybe ask and see if they would install the -17 studs during the build?


I have a feeling many previous builders just installed as is, changed to the thinner washer, or ?


Lycoming customer service has been very good, FYI
The one thread rule only applies to nylon lock nuts, to help resist loosening. Your post states the use of a std nut with separate lock washer. Not sure why you would need to have a full thread exposed past the nut. It doesn't help anything.
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Last edited by lr172 : 02-16-2020 at 03:46 PM.
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  #4  
Old 02-16-2020, 05:28 PM
markelliott markelliott is offline
 
Join Date: Jun 2018
Location: minneaopolis, mn
Posts: 32
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LR172 - INCORRECT. According to Hartzell propeller service letter and installation manual, "The studs must be of sufficient length to permit AT LEAST ONE thread to be visible above each mounting nut after the governor is installed".


The reason would be to be 100% certain that all the torque on the nut is applied through the required number of threads in the nut. Anything less than a protruding stud would be insufficient.


As always, please follow the manufacturers instructions........
Mark
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  #5  
Old 02-17-2020, 09:14 AM
lr172 lr172 is online now
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 4,714
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Quote:
Originally Posted by markelliott View Post
LR172 - INCORRECT. According to Hartzell propeller service letter and installation manual, "The studs must be of sufficient length to permit AT LEAST ONE thread to be visible above each mounting nut after the governor is installed".


The reason would be to be 100% certain that all the torque on the nut is applied through the required number of threads in the nut. Anything less than a protruding stud would be insufficient.


As always, please follow the manufacturers instructions........
Mark
Didn't realize there was a unique hartzell requirement. I thought you were referring to the general FAA AC guidance.
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