Paul,

 I am searching for an outer bearing to fit  the Bell 47 PSRU.
 I have found a source for the original one is which called the
 main rotor mast thrust bearing.   Interestingly enough it is a
 caged ball bearing design.  The cage is made of bronze. The
 bearing is robust and of course can handle some pretty large
 forces from a 1600lb helicopter hanging and cranking on it.
 I'm not sure if it can survive the 2700 radial rpms my
 application will subject it to.  In the back of my mind I am
 thinking, This bearing was designed in 1940.  Could be fine.. Do
 you have an idea how to test it or who to speak to about  an
 alternative bearing?

 I have had no luck in finding the OD dimensions of the Timken
 LL714610 thrust bearing you recommend for the PSRU.


 The Bell uses a mill spec TRW  # 47-130-110-1 bearing

 3" (76.2mm) ID,   110mm OD and approx. 16mm thick.

 Any help you or others can give me to find an appropriate
 substitute please feel free to comment.

 Doug in Japan

 If you find a similar ball bearing today it will not be that much changed
 from 1940. A lot of steel improvements were made in the late 1920's.

 I am not as senile as I thought I was. There have been at least 100 emails
 since I uploaded the dwg with the thin section LL714610 tapered roller Timken bearing.
 I amazed myself and was able to find and recall what I really said :)

 Actually I did not recommend it as I said it is too sensitive to
 housing expansion and contraction heat changes as I recall.
 Here is the dwg you are referring to I think.

 The bearing is listed in the 62 meg pdf, 1250 page Timken Products
 Catalog page B128  year 2007
 http://www.timken.com/en-us/products/pages/catalogs.aspx

 The big cat has been broken down into smaller versions
 so it is a lot harder to find things. I have no idea where
 that bearing now hides. The categories are marketing oriented.

 Here is the message from 10/26/2010 12:10 PM
 --------------------------------------------
 I Like the splines on the shaft and prop flange.
 More expensive but probably worth it.
 It allows the other end of the prop shaft to have
 a welded on or totally machined flange  that
 simply bolts to the planet carrier or becomes
 half of the planet carrier

 Here is a low cost and light weight way of
 handling the trust load going down the prop shaft using
 stacked needle thrust bearings.

 My 3D's are not done yet so this will be incorporated into
 my suggested final design.

 BTW I have second thoughts about the mini sprint car bell.
 The bell part is actually a disadvantage for several reasons
 A. is Jeffs adapter plate will have to be modified.
 B. a complex part must be machined to hold the ring gear
 stationary.

 It is probably easier to make something out of thick wall
 aluminum tube similar to this dwg except needles instead
 of thin section tapered roller bearings. Thin section tapered
 roller bearings are sensitive to housing expansion and contraction
 not to mention they are very expensive.

 The diagonal tube bracing  shown is optional.

 The design is interchangeable with Tracy's box.

 Paul Lamar



Paul,
Thanks.   I downloaded the catalog.  I couldn't find any
reference to maximum operating speed.
The properly design ball bearing can take both thrust and radial
loads.   Thrust loads on a aircraft engine with a straight gear
PSRU would be primarily static thrust right?  Axial loads would
be more of a concern.   Reverse thrust will be a concern as the
propeller goes into beta for backing away from the shore.

Doug in Japan

Which catalog did you get? There are about a dozen.

You need to find the place in that catalog that deals with bearing
life as that depends on RPM.

Paul Lamar