Hub wear

[rossclark]

Further to the discussion on hub issues I did a bit of digging on the shed and turned up an old hub and cone and a new one.

I asked a question about the fit of the cone in the hub on one of the earlier threads but this might answer it.

This is a new SIL hub and cone. If you look you can see that the cone protrudes by a couple of mm from the taper in the hub and there is room for it to be drawn in and compressed before it gets to the splines.



Here is the old hub and cone -



You can see how much further this cone goes into the taper. It looks like there is no scope for the taper in the hub to squeeze the cone. I suspect that if this hub where to be fitted that the cone and taper would not be doing much to secure the hub and that you'd be relying on the nut staying tight.

Even with the new cone fitted in the old hub there's still not much room for the cone to work.



I think this shows wear on the hub and I'd be very wary about refitting this old hub.

[johnnyXS]

good bit of detective work there Ross.. and very timely too. I noticed yesterday that my LiS has got the dreaded hub wobble and I'm going to need to see to it asap. I checked the hub nut and it was still tight so something else methinks.

Funny enough it went through the MOT Saturday with flying colours

[Scooterlam]

Check the inside diameter
If it's been under compression it may have lost some of its spring.

A slightly more scientific test would be to fit to each to its specified torque, then using a hub puller puller working from the lowest setting up on a tourque wrench find how much force they hold.

[johnnyXS]

my feeling is that wear has allowed the hub retaining nut and lockwasher to 'bottom out' on the layshaft shoulder. That could explain why the nuts are are still tight and torqued to spec yet the hub wobbles on the shaft.

Or the wear could be in the cone or the hub thickness or a shim somewhere. Or .... maybe the hub bearing is worn or the end plate is loose ...
It would probably be a good idea to measure the thickness of the hub and width of the cone and compare with standard tolerances.

[johnnyXS]

Check the inside diameter
If it's been under compression it may have lost some of its spring.

A slightly more scientific test would be to fit to each to t find hohe specified torque, then using a hub puller puller working from the lowest setting up on a tourque wrench find how much force they hold.

ok I give up are you referring to the cone ?

[Scooterlam]

Sorry mate,
Dodgy eyes and an over zealous predictive text are getting the better of me.

But yes the important thing is the internal diameter of the cone, when it's pulled fully home.

[kennystag]

Hi All,
There are Indian and an Italian cones.
Stag
LAMBRETTA REAR HUB CONE - INDIAN SIZE

LAMBRETTA REAR HUB CONE - ITALIAN SIZE

[johnnyXS]

Sorry mate,
Dodgy eyes and an over zealous predictive text are getting the better of me.

But yes the important thing is the internal diameter of the cone, when it's pulled fully home.

Hi scooterlam thanks for the clarification . predictive text eh.!?.... tsk tsk .....bane of my life
Apologies for delay in replying .

I am just about to rebuild a spare engine so I'm going to be looking very carefully at all the hub /layshaft components and making some measurements especially of the new cone .

[rossclark]

Bit of a delay, been working away this week.

The Italian hub / and cone are old but GP. I think you can see even in the picture that the gap is smaller and that's why it fits in ever so slightly further than the new SIL one.

As has been stated above, it's probably lost some of its spring. I'll dig them out again on the weekend and get the micrometers out...

[Scooterlam]

Ive spent the last two days fitting and refitting 6 different hubs, dont ask why .
Some of the cones were so closed i had to wedge a driver into the split and twist to get them over the splines.

With the exeption of one they all tourqed up and needed a good bit of leverage on the hub puller to get them off.

[rossclark]

How was the fit in the hub?

[Scooterlam]

As you would expect really,
tight on the splines, loose in the Hub and visa versa

I always have the gap in the cone suppurted..
i wonder if not doing this is where some of the issues come from.

[rossclark]

Sorry I meant kind of in the context of how deep into the hub the cone fits.

In the case above I don't think there's any room for the taper in the hub to compress the cone axialy at all and while you'd still be able to torque the nut down I'd suspect the cone would be doing very little binding on the layshaft.

The cone should always be fitted with gap over a spline, agreed.

[Warkton Tornado No.1]

Hmm.

I’ve watched this debate & hope that my comments will help.


A cone is specific to certain hub types in the variation of the taper. There are three different angles, I believe.

They all have the same ‘nominal bore’ in that when compressed so that the bore fits the layshaft, they will all have the same major outside diameter & the same minor diameter within acceptable tolerances.

You can prove this to yourself by placing a cone on a spare layshaft with its split in line with a spline then compressing the outside in the soft jaws of a vice. Have the split uppermost. Don’t worry for the purpose of this exercise that if the cone ‘springs’ open a little on the small end (minor diameter) add a piece of softwood or two with the soft jaws to compress it fully on to the layshaft.
The (now parallel) gap can vary, but the major diameter will be ‘Ø X’ & the minor diameter will be ‘Ø Y’ if the length is ‘Z’

That’s all there is to the theory of cones & how it will be forced to fit both hub & layshaft if fitted correctly.

I think that people can get their knickers in a twist over-analysing what is a simple, proven concept because the split means that the cone will naturally ‘spring’ (usually inwards a tad even from new) & that will be dependent upon variations in age, material, manufacture et cetera.

I would just add that the ‘datum’ face is @ the large (major diameter) end & should be ‘square’ (perpendicular) to the bore. The face of the small (minor diameter) end hardly matters a toss as nothing should get to touch it apart from fresh air. That’s why the length of the cone can vary without problem as long as the taper remains @ the correct angle.

I really hope to have only helped & suspect a few other engineers on this site will agree with my analysis which some of us may be a little complacent about & take for granted.

Please. Just don’t comment adversely about my attempt to help unless you really can prove otherwise.

“A little knowledge is a dangerous thing”

[Scooterlam]

in my simple world I look on the cone as a wedge being forced into the gap of the shaft and hub.
the fact its a circular wedge makes no difference to the Basic theory.

[Dimitrios_231]

Found some NOS cones.
If you have free time,spot the one that looks different,it is not for S1/2/3

[rossclark]

I don't disagree but if there isn't room axially for the cone to compress into the taper in the hub before it hits the splines then surely it won't work as intended.

All the hubs above are 8 degree taper GP type.

[Fast n Furious]

This is an old thread I know but let me put my 2 pen'th worth in.
To get the best out of these 'Taper lock' bushes you should lap them in with grinding paste. Especially, if the hub or cone is new or from another scoot.

No different to how you match your flywheel with your crankshaft taper!

The rated nut torque then has a chance of being properly effective. Additionally, this would promote confidence in the integrity of the layshaft making it less likely to snap, and because the pressure is spread evenly within the taper, the stresses around the hub center are also reduced.

Win Win.

[ROClarke]

My rear hub comes off without a puller,what does that mean guys?
Is the cone worn or the hub ?

[Warkton Tornado No.1]

My rear hub comes off without a puller,what does that mean guys?
Is the cone worn or the hub ?

Q: My rear hub comes off without a puller,what does that mean guys?

A: DANGER

Q: Is the cone worn or the hub ?

A: Either or both. Sometimes the hub conical surface cracks thus enlarging the area that the cone tries to engage with. You may have a mismatch. We'd all be guessing the problem.

This is a safety issue & you really should not ride any machine where the hub doesn't lock on to the cone.