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.

-----------------------------------------
Go here and download all three catalogs.

http://www.timken.com/en-us/products/Pages/TimkenProductsCatalog.aspx

In the engineering catalog start on page A21
and read all 176 pages :)

Paul Lamar
--

Paul,

Got them all, read them all. Good stuff. Thanks for the link.
Nice to be able to read catalogs in my native language for
once:)
So the Bell 47 bearing is an angular bearing meaning it can
support both axial and thrust loads. I found some Timken items
that were similar in design but slightly smaller in OD and
thickness. I could always slip in a spacer ring into the
housing I guess.

Doug in Japan


A lot, if not most bearing companies, are switching over
to metric sizes. My guess is the Bell 47 gear box was designed
using inches so you probably need to look for inch bearings
in the larger sizes.

I take it this is the bearing you are looking for.

I see that this outfit had only 1 in stock. Not good news
as they probably looked long and hard for a replacement.
http://www.bell47parts.com/PartsList.aspx


Paul Lamar

            
You can use a combination needle bearing combine with trust
bearing ,i am using one  my design on the front side of planet.
There is the link those bearing are sold in USA east southern state


http://www.ikont.co.jp/eg/product/needle/ndl05.html


Jean Prudhomme

Now you are talking Ross language Jean. That happens to
be the lightest way to go for a PSRU.

Paul Lamar

Jean,
The bell 47 PSRU design uses straight gears so axial loads are
only a component of the propeller thrust. Radial loads incurred
by gyroscopic forces are the bigger concern.   A helicopter by
the way has both but I realize the bell annular bearing may be
way overkill for  for my application.  I think the 2mm or 3mm
9114WI  (Page 178) may be fine.   The first two numbers followed
by  are contact angle of the ball bearing to the race and
influence how much the bearing design is favoring thrust or
radial loads. (WI = low shoulder on outer ring)
Now all I need is price:)

Doug in Japan

Due to the hinge in the helicopter  hub gyro loads are not as high
as one would otherwise think.

Paul Lamar