rear hub mishap, advice please

[peejay]

at some point that hub was incorrectly fitted to the layshaft and partial damage occured to the hub splines.

it was then only a matter of time before the hub came loose.

always fit hub with matching cone and torque up correctly, this is just so vitally important it cannot be stressed enough.

the locking plate screw and locking plate will not prevent the hub nut from coming loose if the nut is not correctly fitted.

sadly most peeps will have experienced this problem, i certainly have

[johnnyXS]

The taper cone is a common tried & trusted method of drive in engineering (Morse taper for drills & mills) & automotive (front wheel bearings on FWD cars have terrific amounts of load serving the purpose of drive, braking & steering) where there will be specified amounts of pre-load.

Most motorcycles & modern scooters use a taper for driving the rotor (flywheel in our case) with the woodruff key as a ‘one toothed spline’ just for location.

.

yes we are all aware of the taper drive for rotors but there is a lot of difference between driving a 3Kg rotor by friction and driving the weight of a scooter and rider throught a rear wheel by friction alone under acceleration and braking . As for the cars wheel bearings yes they do take enormous point,distributed, dynamic , axial and impact loading but they don't act as a transmission of engine output to the road as the transmission components do and anyway they are ball and needle race bearings not friction cones

if you removed the splines on a layshaft and the hub and relied on just friction of the cone and lock nut how far down the road do you think you'd get .?
sorry WT1 i'm not trying to beat your gums but as an Engineer I just cannot accept your premise as it cannot work

[Warkton Tornado No.1]

Post by johnnyXS » Mon May 23, 2016 10:06 am

yes we are all aware of the taper drive for rotors but there is a lot of difference between driving a 3Kg rotor by friction and driving the weight of a scooter and rider throught a rear wheel by friction alone under acceleration and braking . As for the cars wheel bearings yes they do take enormous point,distributed, dynamic , axial and impact loading but they don't act as a transmission of engine output to the road as the transmission components do and anyway they are ball and needle race bearings not friction cones

if you removed the splines on a layshaft and the hub and relied on just friction of the cone and lock nut how far down the road do you think you'd get .?
sorry WT1 i'm not trying to beat your gums but as an Engineer I just cannot accept your premise as it cannot work

I don’t understand your comment about FWD bearings as they are still under load, whatever you may reason regarding the transmission components. Loads to a bearing are a product of the power/torque/impact being passed through them, if you like, but still significant. Witness the change by Innocenti in upgrading the magneto side bearing to an NU2205 yet if you were to follow your logic, there would be no need.

I think I understand your misgivings but I have only done my best to explain what I believe to be true.

You could hypothetically, remove the cone from a hub, tighten up & even ride some distance should you choose. After all, the splines existence would allow you to tighten the nut to whatever torque you think adequate. If you felt that you needed a ‘centring’ component then in place of the cone, you could perhaps have a heavily turned back cone with just two thin bands of contact. I wonder how far you would get….

On the other hand, I would much rather prefer to ride from one end of the country to the other with no splines whatever but a well fitting cone, tightened to the correct torque*. Perhaps you would concede to allow me a dab of Loctite to keep the nut in place as the locking ring would serve no purpose? Better still, allow me to drill & fit a split pin through nut & layshaft.

That’s how much I believe in the relevance of the elements that conspire to keep the hub in place.

* Before anybody points out the difficulties of torquing up the nut, yes, I know that I may need to lock the transmission or simply use an impact driver with torque settings, but believe that as soon as the cone started to grip, significantly below 110-120 lb/ft, say, then the final tightening could be achieved via the back brake alone.

[johnnyXS]

no point in coming to verbal blows over it I always enjoy reading your posts and respect your desire to help and advise others so

guess we'll just have to agree to disagree

[Andie]

Thanks gents.

I am putting the error down to a well worn hub and the locking screw coming loose - the former being an eventuality and the locking screw my fault - after a full rebuild I should have checked it. I probably ran a good 4 KM after the problem bloomed fully, trying to get back to my garage with a wobbly hub (though not recognising the symptoms at the time), which might explain the damage.

The locking locking ring is totally shot - a cheap replacement that I will think twice about next time.


I have 'upgraded' to an MB stainless steel version. Which is a hat above the previous one, it's thicker, solid, fits over the nut well and binds much better.

Even with good torque on the cone, if the locking screw comes loose, and I'm braking, it's going to come loose I guess. I had 450 klicks of constant back road stop/start before it failed.

Thanks again for assisting. This forum is very useful.

[Warkton Tornado No.1]

Post by johnnyXS » Mon May 23, 2016 8:15 pm
no point in coming to verbal blows over it I always enjoy reading your posts and respect your desire to help and advise others so

guess we'll just have to agree to disagree

Thank you for your comments.

As an Engineer myself, I am still keen to push some of the boundaries that sometimes restrict our thinking. I am aware that my often outspoken thoughts can seem incredulous, but, as is often the case, it is satisfying when I can prove my beliefs despite any scepticism.

As a Design Engineer, I am probably somewhat privileged to have worked with large, highly accurate concepts that utilised double row spherical roller bearings with a 1:12 taper in their bore. The removal of those bearings, once fitted, relied not only on induction heating but principally upon grooves & oil ways built into the journals in which oil would be injected to unseat the taper; such was the strength of the bond.

[Andyf]

I often chicken-out when doing up my rear hub and wait for a mate to come round and tighten it, I simply cannot comprehend that it requires such force to provide sufficient grip/security. I can't help thinking that - when dealing with relatively small diameters such as these - the load/grip limit is very soon reached and it quickly converts to thread deformation. stupid I know but I simply can't do it.

[rossclark]

How far should the cone go into the hub in normal circumstances?

I'm trying to figure out if a hub I have has worn taper or cone.

It protrudes from the hub by about a millimetre or so and looks like it might go down nearly to the bottom of the taper area.

[xenia1]

does anyone else think that the hub splines show insufficient bearing on the layshaft ?
It looks like the layshaft hasn't been pulled through sufficiently or the layshaft shimming is wrong somewhere?
Maybe its just me but I would have expected the splines of the hub to engage on the splines of the layshaft at least 3/4 engagement yet that hub looks like they engaged about 1/3rd ?
Could the original cone be poorly dimensioned not allowing the hub to engage fully with the layshaft?

My thought as well when i first saw the picture of the layshaft, there doesnt appear to be enough of the splines through to allow proper/full engagement..