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Prop flange bushing length

mmcelrea

Member
Hi.
I have a Titan io370 and I am concerned about the length of the prop flange bushings. There appears to be less than 1/8” catch on the prop hub, it’s nearly only the chamfered end protruding, thus transmitting the torque through the bolts.
Can anyone advise if there is a minimum length for the prop flange bushing to extend beyond the face of the flywheel?
I have been in contact with Titan and was told there is no minimum length?
I also have the Lycoming document advising the length of the bushing on various engines but nowhere can I find the minimum length that should protrude from the flywheel face.
The hartzell hub is recessed to accept longer bushings.
I don’t know if I need a different flywheel or bushings.
Miller
 
That would be Lycoming Service Instruction # 1098G for a listing of bushings, combinations & positionings. Dimensional listings in there too.
Guess you could change out to some of the long ones.
 
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I can't remember what mine were, but would guess 3/16-1/4" I would want at least 1/8" of unchamfered OD present. Not an expert, so don't know if that is enough. Less than 1/16" of unchamfered sounds way too short to me.

Larry
 
Just thought of something that is probably unlikely, but maybe worth checking out.
One of the bushings is thicker than the others, to line up with one slightly larger diameter hole in the flywheel. This is to determine TDC alignment with the crank. If by remote chance the thicker bushing is in the wrong flywheel hole, it won't mount flat with the crank prop flange, and give the appearance that the bushings are too short, not to mention installation this way would seriously affect prop mounting security amongst other bad things.

Just throwing it out there
 
The prop flange is .45" and the bushing length is listed at .84" which leaves .39" for the flywheel and the protrusion into the prop hub.
From whirlwind prop web page there is a diagram showing typical lycoming drivelug extending .300-.375 from the surface of the flywheel. Another whirlwind diagram shows the drivelug extending .250-.300". Hartzell don't seem to have a minimum requirement.
What is the typical length protruding?
 
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