Crankshaft Endplay

normally should have around about .20mm of preload

 

I don't believe I have just seen that reply..........I think Amentia should ignore it.

 

There you go.......so I was right first time

I was going to suggest you phoned Moto Rapido or Snells........

Its the gearbox shafts that need some endfloat and 39 thou seems to be the figure in the workshop manual....

AL

 

Steve

I would be grateful if you could explain ' Pre- load'

I can understand the need for ' end-play on a gearbox shaft, but am I correct in assuming that 'Pre- load' on the crankshaft means that the bearings are being ' sqeezed'by a small amount?

 

What's your problem with this Al? 0.20mm is by my reckoning about 0.008", which is about the correct preload is it not?

 

@CRYSTALJOHN Are you sure? The online convertors say 0.20mm = 0.0078"

 

Dave Hopefully you can see by my post deletion I was wrong - you are correct!


And can you explain Crankshaft pre load please?

 

Preload is basically the opposite of end float, the distance between the housings is X mm, the distance outside the bearings is Y mm, if X is greater than Y, then you will have end float, if X is less than Y you will have preload, preload is generally used in higher load applications and uses special bearings. there are differing ways to achieve preload, in my experience, the most common are using shims or collapsible spacers, and adjustable "nuts" that are lockable.

:Arghh: Fuck, why didn't I just say that!!! ^^

 

I can understand the need for pre- load on a tapered roller bearing , but can't work out why pre- load is needed on a plain ball bearing. It seems to me that applying a sideways load would be increasing friction?

 

You do not want a crankshaft moving laterally in an engine, it would create all sorts of load in places you wouldn't want it, so they use preload to "hold" it place at differing temps, with different metals expanding at different rates.

Plus they are not plain ball bearings, the races the balls run in have a higher side inboard on the inner race, and a lower side outboard of the outer race, to cope with the extra side thrust loads. (As I understand it)

 

Excellent explanation Dave, fully understood.

I didn't realize that the crankshaft bearings had a ' higher side and a lower side'

 

I'm not positive the Ducati ones have, I'm going off my experience with automotive gearbox's, axle bearings etc. But I would imagine they are they same.

 

The Ducati workshop manual mentions nothing about pre-load on the crankshaft........and the OP has spoken to a Ducati dealer who also stated 'None'.

If pre-load was a requirement, I'm sure Ducati would have stated it in the manual, but as they provide a range of shims from 0.3mm to 0.6mm, it seems likely this is to ensure there is no pre-load.

The manual doesn't mention two sided bearings either.

Mind you, when the crankcase is built without the gasket, that alters everything...how thick is the gasket for example?

I can understand a negligible amount of pre-load, but 0.2mm is a helluva lot, really.......I have experienced what the incorrect length spacer can do to wheel bearings and the wheel itself.

Still, not having built a Ducati crankcase, I would have to refer to the manual....and avoid having shims 0.1mm or less.

Give me a horizontally split crankcase and bearing shells any day!!

 

Taken from a 1000sport manual but they are all pretty much the same

 

That's interesting Bolds.............I wonder why Ducati appear to have changed their minds between models and manuals.......IE; SS no pre-load and 1000Sport pre-load.....

AL