531colin wrote:Brucey wrote:.........You can check how tightly held the sprockets really are by using a couple of chain whips; they will move within the spline backlash, at a torque which varies with the clamping load.....
All my freehub bodies are steel. Even with cassettes built up from bits (ie no rivets), all I see are bright witness marks where the individual sprockets bear on the hub body.
I know its different with alloy hub bodies, you can get a lot of wear on the edge of the splines; but can you realistically exert enough clamping load on the sprockets (and plastic spacers) so that the chain load on one sprocket is shared out between the stack of sprockets? Because if you can't, what is the purpose of tightening the lockring to a high torque?
With my steel hub bodies, I just nip up the lockring so that the cassette doesn't fall off.
I have seen worn steel freehub bodies but this takes a long time to occur even with loose sprockets. For sprockets which are clamped to any meaningful extent, they may not be on the move all the time, only when you are putting in an above average effort. Obviously this will vary from rider to rider. When I see 'badly bitten' freehub bodies this can only have occurred two ways;
1) the lockring wasn't tight enough
for that rider and the sprockets were on the move from the start or
2) the clamping force on the sprockets eased over time.
I think 2) is very common; lockring serrations may mean that the clamping force isn't quite as high as you would like from the start, and between creep in plastic spacers and wear arising (from movement) the clamping force is only ever going to go one way.
IMHO the clamping force doesn't have to be enough to cause it to be shared with neighbouring sprockets; it should be enough to prevent the sprocket from moving around. I think that the wear arises from small radial movements of the sprocket under load, and that if the clamping force is enough to suppress that most of the time, it is 'job done'. With plastic spacers I don't think they are stiff/creep resistant enough to sustain enough clamping load to suppress movement under all conditions; the most violent of efforts will always produce some movement rather than none. It is just a question of having enough clamping load that the in-service movement isn't enough to cause problems in the intervals between the lockring being retightened.
Radial in-service movement may be driven by chordal effects (which generate net radial thrusts on the sprocket) in some cases; thus the torque on larger sprockets can be higher, but the chordal effect is less; thus the worst wear in the interface is commonly seen with small and middling-sized sprockets rather than larger ones, perhaps...?
FWIW I would probably have designed the spline with sloping faces rather than radial faces; this would tend to keep each sprocket centralised even under load (cf sturmey-archer IGH sprocket mounting for example). Mountings of this type are inherently more stable when subjected to combined torque and radial thrust loads.
BTW it isn't necessary to undo the lockring on tour, if you use shimano hubs; provided you have cone spanners the axle can be withdrawn and the freehub body removed (with the cassette still attached). This way you can have your lockring properly tight and not have to worry about getting it undone.
cheers