ET: Engine (Twin) Installing ET92 Inner Roller Set on Mainshaft

[Bill Thomas]

Just trying to think how deep bearings are before shot,
As a Mechanic of many years , Seen lots where they have worn through a layer,
" Into another colour " ?, Mostly wheel bearings,
Fords in particular had a bad idea of too much preload with there rear wheel bearings,
Taper rollers !
No if's and but's, We just had to do the nut up to a torque !.
It went on for many years, 80 s90 s ?,
Why after a short time they didn't go over to an adjustable taper rollers ,
Like most other makes , I don't know ?.
Cheers Bill.

 

[craig]

I will remeasure the shaft OD and roller ID and post back.
If bearing ID too small can it be ground to size?

 

[oexing]

Bearing dimensions should come in very narrow tolerances so I´d not expect any need for grinding races. The mainshaft is meant to be exactly 1 " , 25.400 mm, or maybe half a thou oversize from nominal. Get a calibrated micrometer for checking mainshaft , a block gage with 1 " would be great - never have faith in anything , better do checks yourself. I´d think your worries come from not quite calibrated mics .

Vic

 

[craig]

I am rechecking dimensions and find that the shaft measures 1.00065"
and the new main bearing roller measures 0.99965"


25.41651 - 25.3911 = 0.02541

 

[greg brillus]

Craig, That comes out at 0.001" interference........ You can simply heat the inner race and it will slide onto the main shaft........You should however go through first and check the crank/rods are as central as you can get with shims if necessary using the center of an old ball bearing as a spacer to check this. It is quite common for the bearings to show movement on the shaft, usually if the ESA nut is loose, and this will wear the shaft quite badly........this is the main reason for replacing the main shafts in the flywheels........not a nice job to do unless you know exactly what you are doing.

 

[oexing]

Ouch, one thou shrink fit would not be my idea, you´d need 120 degrees C for dropping the inner race on the mainshaft. The i.d. of the inner race is about what I´d expect with correct bearings. Only the mainshaft was made a bit oversize - did you get a new crank or new mainshaft in this case ? If it was my crank I´d try to machine the mainshaft to max. half thou over nominal or just nominal 1 ". Who was the provider of the crank parts ??

Vic
P.S. the safer way to deal with excessive shrink fit is to have the inner race lapped or honed to max. half thou undersize. Lapping by diamond paste on expandable bronce or cast iron mandrel or honing by Sunnen 1 " hone. You want a good parallel contact race bore on mainshaft, so polishing it by abrasive is not a great idea.

 

[greg brillus]

Ideally you want the inner ET 92 race to be a snug/interference fit on the shaft, and the outer ball bearing E 91 a sliding fit, but not loose........If the ball bearing is tight, then you have to press the crank assembly in/out of the cases and this is not ideal.........A bit too much "over thinking going on here" I could have carried out this whole process many times in the time this is being discussed here.......... We are dealing with 1940's tech here, not modern computer space age tech........these things should not be difficult to sort out.

 

[oexing]

With the actual crank there will be same problem of oversize mainshaft for the ball bearing inner I guess ? So same honing job again, a slide fit is allright as all inner races plus spacer are under high side load from the ESA springs. Not much wear expected here as any walking of inner races is very limited I´d think.
I decided on all lipped roller bearings and did my special steel bush with extra wide lip for the sprocket face to sit on , spreading spring loads so less wear than with standard ball bearing inner race with its radius.

Vic

 

[craig]

I rechecked the centrality of the rod with a 0.015" shim on drive side.
Using over bored dummy ET92 inner races 0.750" width both sides, seems central rod is okay.
Also able to slide fit the small roller ET94 in place to confirm no fit issues.

I am needing a refresh on the need or procedure for shimming ET92 on the timing side.
What is to be accomplished?

 

[Bill Thomas]

I can't remember where,
But I thought we have been told to open up the oil feed hole to the oil pump,
I have just opened mine to 3/32" ?.
Cheers Bill.