<VV> Re: VirtualVairs Digest, Vol 8, Issue 113 , Loose Pinion Gear

[Silveyyevlis at aol.com]

Loose pinion gears are not all that uncommon.  One way to use the old  shaft 
with any gear is to do what has been used in the aircraft industry.   This 
process was invented by engineers at Allison Gas Turbine Div of Gen.  Motors.  
Have the shaft splines or the gear splines plated with copper  0.0002-0.0004 
thick. If you have a real loose gear try to measure the radial  loosness  with a 
dial indicator.  Use half the radial clearance plus  0.001-0.0015 thick 
copper.  You can press the gear on or heat the gear or  cool the shaft or both , it 
doesn't matter.  If you press the gear on the  copper galds and balls up 
locking the gear on. If you use the other method and  the gear ever starts to move 
the same thing happens. Bob Galli has used this  method using up to 0.004 
thick plating with success.
 
The aircraft industry had a severe problem with interferrence  fit  bearings 
on the light weight  ( thin ) shafting where the bearings would  eventually 
loosen and spin on the shaft causing a failure.  Allison  Engineering came up 
with this method of locking the bearing to the shaft.   Even with pressing the 
bearings on and off the shaft the copper still did its  job after many removals 
and reinstallations
 
My favorite method of installing the gear is to heat the gear and drop it  on 
the shaft or push it on the shaft as far you can by hand.   It usually will 
not go all the way , then I press it on the remainder  of the way with a press.
 
There are probably no jet engines or turboprops flying today that do not  use 
this method of to lock bearings on shafting.
 
Good luck, Tom Silvey