> >  > > >Fred Osborn wrote:

 >>  > >>
 >>  > >>  Paul,
 >>  > >>
 >>  > >>  I understand that the rear journal e-shaft bearing is not suitable
 >>  > >>  for the side load imposed by a cog belt drive. For a single rotor
 >>  > >>  engine how about a needle bearing which would run between the
 >>  > >>  e-shaft and a reworked or redesigned rear synchronizing gear
 >>  > >>  replacement part. Could that arrangement provide an adequate
 >>  > >>  side load capability? Rotor sync would be maintained by the front
 >>  > >>  sync gear.
 >>  > >>
 >>  > >>  Fred Osborn
 >>  > >
 >>  > >Ken Welter uses an outboard support bearing with simple oiler.
 >>  > >Needle bearings have severe RPM limitations. I would use a precision
 >>  > >ball bearing in that application.
 >>  > >
 >>  > >Paul Lamar
 >>  >
 >>  >    I use a needle roller, Torrington # HJ-202820 which has a speed
 >>  > limit of 14000 rpm.
 >>  >
 >>  >    Ken
 >>
 >>  Yes it does but that is at zero load :)
 >>
 >>  Lets see an HJ 202820 has a Torrington basic dynamic load
 >>  rating of 7400 pounds. That is what they call C sub r
 >>  You use that number to enter this chart with the real load and
 >>  the RPM and figure the life. What is the diameter of the lower
 >>  pulley. I need that to figure the radial load at 300 HP take off
 >>  and at 150 HP cruise.
 >>
 >>  I also need the RPM at 300 HP and the RPM at 150 HP cruise.
 >>
 >>  It helps that the bore of an HJ 202820 is only 1.2500 inches
in diameter.
 >>
 >>  I assume the shaft is Rockwell C 58.
 >>
 >>  Paul Lamar

 >BTW as a ball park number since the speed factor at 7000 RPM is 5 a belt
 >tension of 1480 pounds will yield a life of 500 hours. 10% of a
 >batch of bearings
 >will fail and 90% will live to 500 hours.
 >
 >Paul Lamar

    I use an inner race on the shaft, and yes that is why I went to the
 1.25 shaft size as it has a higher speed rating and it is also easier
 to get seals to work on smaller shaft.
   The redrive I am now running has 400 hrs on it and the bearing is in
 fine shape so I guess I running on the limit now but I think that
 engine bearing is taking some of the load also.
   The bearings are real cheep and easy to replace for cheep insurance.

    Ken

I am not sure if you are Ken until I figure out the belt tension which is
a function of the HP transmitted and the engine RPM.

Yes the rear main could be taking some of the load if the roller is not
directly under the center of the pulley. Even then there could be a bit of
mis alignment.

Paul Lamar

  At static there is zero static load as the belt is loose but the
centrifugal force creates the tension when the engine is running.

   Ken

It is more than that. To transmit HP you must transmit torque.
The moment arm for the torque is the radius of the smaller pulley.
Lets say it is six inches in diameter and the engine torque is 160
foot pounds or 1920 inch pounds. The belt tension due to this alone would 
then be four times 160 pounds or 640 pounds. Putting it another way 1920 
inch pounds divided by 3 inches is 640 pounds. If the pulley is four inches 
pitch diameter the belt tension and side load is 960 pounds.

Paul Lamar
 
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