16-02-2019, 05:43 AM
(This post was last modified: 16-02-2019, 04:25 PM by Bob Culver.)
The bearings seem in good order and provided the tracks are free of indentations, rust or (unlikely) fatigue pits fine for reuse. Can shim for no clearance but I am curious as to basis for the .004 preload (and this before assembly). From catalogues for normal off the shelf ac races no mention of preload, seem to have a clearance. Preload seems to apply to special precision bearings for machine tools etc I am unsure if great rigidity is desirable, although the strong lip helpful. Other non rigid applications such as gearbox mainshafts and rear axles often stipulate a bearing more loose than standard.
I wonder if preloaded ac races contribute to broken lips.
The saga of the ac bearing and crankcase variations is covered in Woodrow pA2-45, but unfortunately the diagram A-41 lower depicts the inner rings as 1 9/16 instead of 1 5/8!
Many “mechanics” and others have limited grasp of ac bearings and cock ups common. Wrong bearing can alter crank location slightly. Conrods should be in centre of piston apertures etc.Ideally the cam gear needs to be supported near the centre. Not all amateurs accumulate lengths of heavy pipe etc for such applications, but with ingenuity all manner of devices can be utilised to provide an aperture and support. The thread on the camshaft is hardened and difficult to restore if damaged.
As far as i know the bearings do not fail from conventional fatigue but, esp with engines used for short runs with the oils of long ago clearance increases due corrosion wear and almost any clearance contribute to harsh running. Should be virtually no depth of wear on the rear roller track.
I wonder if preloaded ac races contribute to broken lips.
The saga of the ac bearing and crankcase variations is covered in Woodrow pA2-45, but unfortunately the diagram A-41 lower depicts the inner rings as 1 9/16 instead of 1 5/8!
Many “mechanics” and others have limited grasp of ac bearings and cock ups common. Wrong bearing can alter crank location slightly. Conrods should be in centre of piston apertures etc.Ideally the cam gear needs to be supported near the centre. Not all amateurs accumulate lengths of heavy pipe etc for such applications, but with ingenuity all manner of devices can be utilised to provide an aperture and support. The thread on the camshaft is hardened and difficult to restore if damaged.
As far as i know the bearings do not fail from conventional fatigue but, esp with engines used for short runs with the oils of long ago clearance increases due corrosion wear and almost any clearance contribute to harsh running. Should be virtually no depth of wear on the rear roller track.