Fafnir Radial Bearing Thrust Capacity

[dnauts]

I'm having trouble locating the thrust load capacity of a Fafnir 204 radial bearing. I've spoken with a couple people at Timken, and am getting tossed around a little.

Is there a convention similar to some rod-ends, where the thrust or axial load capacity is 20% of the radial capacity?

Dan

 

[Tmoose]

If you are interested in calculating life then there should be a formula for "equivalent load". It takes a fraction (X) of the radial load and a different fraction(Y) of the axial load and adds 'em up.
Then there is the thrust load that causes a problem because it moves the contact ellipse too far up the race. That depends on clearance, etc, but is usually between .4 and .5 for ball bearings under 60 mm bore

 

[diamondjim]

Why are you not talking to Fafnir about
this application? Did Timken buy Fafnir?
There should still be some Fafnir Catalogues
about and you might be able to get the
Static and Dynamic Capacities from it.
Often Radial bearings have little thrust
capacity.

 

[diamondjim]

The thrust capacity is dependent on the
contact angle of the balls in the raceway
and is a sine function of that angle.
Divide by approx 1.25 which assumes only a
80 percent of the balls are carrying the load.
The radial capacity is dependent on the
contact angle of the balls in the raceway
and is a cosine function of that angle.
Divide by 4.37 which assumes only a 25 percent
of the balls carry the load.
I would assume the contact angle to be approx
15 degrees or less for a radial bearing.
These are rough guidelines

 

[btrueblood]

The 204 bearing has a radial load rating only. To determine the rating for combined axial and radial loads "by the book" takes more time and lookup of numbers from complicated tables and graphs than anybody can talk you through here. You need to get ahold of the Torrington/Fafnir bearing catalog, mine is labelled "Torrington" on the front, not Timken, and is copyright dated 2001; apparently the Timken takeover was in 2003, so I have no idea what their latest catalog looks like. The good thing is, the Fafnir bearings have not changed in design in 50+ years, so if you can find a catalog for them dated anywhere within that time frame, use it. In any case, find the Engineering section and go through the calculation to find the equivalent radial loads for your particular combination of radial and axial loading, and then calculate the L10 life per their equations. If they won't send you a copy of the catalog, or at least fax you the relevant pages, holler back and we'll find a way to get the info. to you.

 

[brgguy22]

Rule of thumb is 50% but you must have sufficient radial load too.