Self-aligning rear main

[Parazine]

I have the engine out of my RK saloon at present to fix a slipping clutch. Investigation of the rear main reveals this - a self aligning RM10 bearing.


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I guess some of you racing guys and possibly special builders will be familiar with this mod?? I'd be happy to hear the pros and cons.

From my point of view, the engine has been remarkably quiet in the three years I've owned the car, in fact it's hard to set the timing correctly because there's no rumble from the rear main. A friend remarked "how did you fit a three bearing engine to a vintage car?".

There must be a downside.....

[dickie65]

They are pigs to fit and remove if a tight fit.
They stop the crank from moving fore and aft at the back end which may be an advantage as the rear race takes the clutch thrust rather than bending the crankshaft every time you press on the clutch.
My last one brinneled its balls, luckily no damage elsewhere from flakes of ball bearings.
Do not expect to be able to draw the steel housing out using the threads in it you will have to drift the bearing out from inside the crankcase carefully.
And yes no rear main grumble using these bearing.

[Zetomagneto]

What did you find between the flywheel and inner track? Some sort of special deformable washer presumably? There needs to be something to fill the gap but also allow the flywheel to be tight on it’s taper.

[Tony Press]

Keep in mind the self aligning ball bearing has very little thrust capacity.

Is it a floating fit in the housing with angular contact bearings at the front ?

[Bob Culver]

It is curious the bearing is more quiet. I wonder if with a ball at front the crank length variation due heating and flexing preloads and quietens the bearings? Presumably such bearings are even more expensive than rollers.

[Tony Press]

An imperial series self aligning ball bearing would be hard to find now.

[Tony Betts]

my only knowledge of these bearing is from the engines ive had come in with they fitted, as ive not run one in an engine.

i find because the rear is no longer flouting, it pulls the bearing frange out of the front of the engine.

the crank needs to wip.

tony.

[Ruairidh Dunford]

An engine came in with one of these fitted many years ago - the front lip had been machined off completely.

[Charles P]

Are we talking about a normal deep-groove ball race or a self aligning bearing?
As Tony Press observes the self aligning bearing has little thrust ability, so I'd expect a normal AC pair at the front with a bearing lip.
A deep groove ball race, fitted with a spacer to the flywheel (as Zeto said) could live without a lip.
A self aligning rear with no front restraint via AC bearing/lip is not a combination I'd try


Charles

[Howard Wright]

Hi All

Interesting thread.  I’ve used the arrangement suggested by Terrytuned in his thread “Alternative crank bearings”.

This involves a self aligning and deep groove ball bearing at the front and a roller race at the rear.  I understand the front combination doesn’t offer the same restraint as a pair of angular contacts but as Terry states it works. Albeit in my case a 1 1/2” crank.

Parazine also states that his engine ran quietly and well for some time so a rear self aligning bearing seems to work.

Cheers

Howard