Greg, I guess you had a painted crankcase for taking temperature readings from an infrared digital . These instruments will turn out funny readings when pointed to shiny bare metal surfaces, you´d have to adjust parameters on the gauge. Yes, cylinder heads can easily reach 200 degrees C and more , but better keep that lower as alu would get soft from high temps. I do not believe the main bearings would see much above 100 deg C on the road, any oil temp gauge could tell . Classic all roller bearing engines tend to run quite cool - not so maybe in AUS, a special case here. So that leaves us in a discussion about the need to do extra honing of races for more clerarance in roller bearings when appearing tight in a cold case, not my view. Standard play in new bearings is as seen in my posting above so when there actually might be some risk of loose outer races in ultrahot engine cases , why any need for extra honing - maybe just for assembly in cold garage allright.
Compare operating conditions of cylinder roller bearings in traditional mills and lathes, even when rpms are lower: For setting zero play on spindles some types got taper inner races with spindles to suit. So for achieving a solid rugged spindle - not any play permitted but preload - you knock the inner race along the minimal taper up the spindle for zero play resp. preload and some resistance when spinning the lot. The test run at high rpms will tell if preload is as specified depending on temperatures to stay below like 60 degrees C. No chance of extra clearance from heat growth, all components on spindles are steel certainly. Same with taper roller bearings like on lathes , preload as required, not the least play admitted !
By the way, in the iron diff on the E-Type you are meant to set the taper roller bearings at a certain PREload in cold state, for ridgidity, all iron, no heat growth for extra clearance in consequence !
Bevel Ducatis with taper roller bearings - not in my memory, I´d think they had angular contact ball bearings with sort of tufnol cages.
In our classics conditions for crank bearings are obviously very different , but even so, I cannot see the panic about theoretical bearing play, be it CN or C 3 whatever. Fact is, the thing got lots of kilograms - or pounds - out of balance flywheels and conrods dragging all that steel in all directions with extreme forces at high speeds. So in cruel reality all that steel and alu gets forced anywhere around while some softness and elasticity in components has to deal with this somehow. Some extra 10 or 20 microns from C 3 in this torture will not make a difference in this mess.
As to shrink fits for main bearings in Vincents I cannot figure it out why they decided on plain outer races , no chamfer too, and rollers plus cages on inner race. I never ever found like it on the continent in motorcycles - in combination with staking as well . . . As shown some time ago I have stayed with the lipped races design in my engines with rollers and cages contained in outer races as is common in most machinery. So no string trick is applied here for begging rollers to enter the outer race and no walking plain race eating into the crankpin nut. I have proposed for metric bearings - yuk - with lipped races so no need for weakening the case like when you bore it oversize for a bush and standard 63.5mm imperial bearings. With the lipped metric bearings you could just press in an alu adapter for 62mm metric o.d. and loctite a bush on the imperial crank mainshaft of 1 " for the new 30mm inner race - simple . Plus the PA 66 GF cage of modern bearings will provide decent higher load factors too, from some more rollers inside.
Anyway, just a few suggestions, I may be quite wrong certainly, but sorry, some designs from olden times have not grown more acceptable to me, just drawing my conclusions from decades of working on machinery, not by engineering degrees, just a lowly toolmaker. And with defects it is often not an obvious single flaw but really a collection and result of many underlying defects in an engine - an extremely rough habitat for components which work together more or less in harmony - or rather by sheer force . . . So when facing a defect I am not in a position for pointing exactly and absolutely to one single root of it, you´d have to see the whole picture of a particular engine.
Vic
Compare operating conditions of cylinder roller bearings in traditional mills and lathes, even when rpms are lower: For setting zero play on spindles some types got taper inner races with spindles to suit. So for achieving a solid rugged spindle - not any play permitted but preload - you knock the inner race along the minimal taper up the spindle for zero play resp. preload and some resistance when spinning the lot. The test run at high rpms will tell if preload is as specified depending on temperatures to stay below like 60 degrees C. No chance of extra clearance from heat growth, all components on spindles are steel certainly. Same with taper roller bearings like on lathes , preload as required, not the least play admitted !
By the way, in the iron diff on the E-Type you are meant to set the taper roller bearings at a certain PREload in cold state, for ridgidity, all iron, no heat growth for extra clearance in consequence !
Bevel Ducatis with taper roller bearings - not in my memory, I´d think they had angular contact ball bearings with sort of tufnol cages.
In our classics conditions for crank bearings are obviously very different , but even so, I cannot see the panic about theoretical bearing play, be it CN or C 3 whatever. Fact is, the thing got lots of kilograms - or pounds - out of balance flywheels and conrods dragging all that steel in all directions with extreme forces at high speeds. So in cruel reality all that steel and alu gets forced anywhere around while some softness and elasticity in components has to deal with this somehow. Some extra 10 or 20 microns from C 3 in this torture will not make a difference in this mess.
As to shrink fits for main bearings in Vincents I cannot figure it out why they decided on plain outer races , no chamfer too, and rollers plus cages on inner race. I never ever found like it on the continent in motorcycles - in combination with staking as well . . . As shown some time ago I have stayed with the lipped races design in my engines with rollers and cages contained in outer races as is common in most machinery. So no string trick is applied here for begging rollers to enter the outer race and no walking plain race eating into the crankpin nut. I have proposed for metric bearings - yuk - with lipped races so no need for weakening the case like when you bore it oversize for a bush and standard 63.5mm imperial bearings. With the lipped metric bearings you could just press in an alu adapter for 62mm metric o.d. and loctite a bush on the imperial crank mainshaft of 1 " for the new 30mm inner race - simple . Plus the PA 66 GF cage of modern bearings will provide decent higher load factors too, from some more rollers inside.
Anyway, just a few suggestions, I may be quite wrong certainly, but sorry, some designs from olden times have not grown more acceptable to me, just drawing my conclusions from decades of working on machinery, not by engineering degrees, just a lowly toolmaker. And with defects it is often not an obvious single flaw but really a collection and result of many underlying defects in an engine - an extremely rough habitat for components which work together more or less in harmony - or rather by sheer force . . . So when facing a defect I am not in a position for pointing exactly and absolutely to one single root of it, you´d have to see the whole picture of a particular engine.
Vic
