REFLECTOR: MT Prop failure mode? - Resolved

[Alex Balic]

There are a number of different all metal locking nut designs that do not
have a temperature restriction- some are available from McMaster Carr, I
would think that the Nylon insert nuts would be fine in the prop though. I
don't think that jamming 2 nuts together is a very good method of locking-
it puts a good deal of stress on both the nut threads and the shaft that
they are attached to, and even the smallest amount of loosening due to heat
cycling or vibration will unlock them, unlike self locking designs that will
resist turning by themselves.

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of davedent at comcast.net
Sent: Wednesday, November 19, 2008 11:53 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: MT Prop failure mode? - Resolved

Related to the fiber lock nuts, consider that you use only aircraft quality 
nuts.  Steel with nylon only.  Now some may say they are of a fiber insert 
but they are plastic inserts.  Make sure that the insert is made of nylon 
before using.

In very high temp areas like the engine compartment I do not recommend using

any fiber lock nuts.  Most of the nuts are rated to no more then 250 degrees

max.  The prop area will not reach these type of temps.  So the main thing 
to make sure is that they are not plastic but nylon type nuts.  If you check

McMaster Carr you will see they label, if I remember, the type of insert. 
Do not use aluminum with inserts.  Use only steel with a nylon insert.

The nut can be used numerous times as long as you can not turn the nut onto 
a bolt or thread by hand past the locking portion of the nut. You need to 
have at least flush to one thread minimum for the nut to do the job.  I 
prefer that at least one thread be showing past the nut. In the case of the 
prop pitch shaft you will see from four to five threads pass the nut 
showing.  Once you have the low pitch stop where you want it I would 
recommend that you drill a hole through the nut and shaft and pin it with a 
roll pin.  This is recommended by Vesta as well. Their nut comes 
pre-drilled.
Dave 

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