Bevel tower/cartridge bearing orientation

[Blimp]

Hi there, I removed the bearing cartridge for the lower bevel gear on my narrowcase engine so I could change the bearings. In my haste I removed the old bearings without taking note of their orientation. I understand the new bearings need to be installed as a pair and the correct way round.

What is the correct way round and how do I tell when looking at the bearings?

Many thanks

Ryan

[Rick]

Ryan,
You should be able to see the difference in width of the bearing races- angular contact bearings have one wide and one narrow race. You want the narrow race to be to the outside/cartridge, and the wider races to the shaft, when looking at the bearing cartridge from each end- harder to explain than I thought- here's the picture from the shop manual:

lower bevel 2.png

If you haven't read about shimming the retaining collars, they need to be shimmed carefully.
Rick

[double diamond]

If you look at the inner race of these angular contact bearings, you’ll notice one end of the race is a larger outside diameter than the other. The larger diameter end of the inner race should face out of the cartridge. So the upper bearing is oriented the opposite of the lower bearing.

Now that you’ve replaced the bearings, you may have to adjust the contact and backlash of the cartridge bevel gear to the crankshaft bevel gear. You should also check the contact of the cartridge retention flange; it should prevent the cartridge from moving axially in the engine case while also accommodating a proper fit for the flange gasket. Matt

[Blimp]

Many thanks guys, that makes sense now when I look at the bearings and read your explanation.

Cheers.

Ryan

[Sigean]

Just a thought, and not wishing to negate the good advice already posted, but with these angular contact bearings does it really matter which way they are oriented as long as the top and bottom orientation is the opposite of each other (ie one is "up" and the other "down")? There should be no difference in performance either way with these bearings. Please tell me if I am wrong!

Sigean

[Rick]

It definitely matters- thrust is transmitted from the lower bearing wide race diagonally across the ball to the other race, along the spacer, and to the other bearing. If the bearings were flipped over, thrust applied to the narrow race wouldn't be applied to the lower balls- even if you moved the spacer to the inner race the lower bearing wouldn't share the load. Even with the bearings arranged in the customary way, I think the lower bearing is carrying more load than the upper, unless you get the shims under the circlip at the top just right- almost slightly preloaded. More complicated than it looks.
Rick

bearing cartridge.png