Front Wheels Bearings - with a twist

[lambrettalad]

was that Halleys comet In 1910?

[bmcecosse]

Hohohoho - not quite...

[philthehill]

Islipminor
I can see that you are passionate about the subject matter of this post but I have to say you have not won me over with your arguments so I will say no more on the subject and leave you to plough your furrow.

And as with BMC I am old enough to remember the 1954 De-Haviland Comet crashes.

Regards
Phil

[IslipMinor]

No, not passionate, just like to understand things thoroughly, so thought I would do a few basic strength calculations for the stub axle and the effect of the clamped bearing/spacer.

Of the 3 elements the spacer is the weakest, the others being 2 solid inner bearing races, so I have used the spacer as the basis for calculating any strength increase.

Taking the axle bearing diameter of 25mm (inner bearing i/d) as the datum, and the spacer at its minumum of 17mm (outer bearing i/d), the stub axle strength in bending is increased by 55% (this would be the absolute minimum as the stub axle reduces down to 17mm and the spacer bore increases to ~25mm). Taking mid-points for both axle and spacer gives an increase of a massive 162%.

A bit surprising maybe, but strength of a round bar or tube increases by the cube of the diameter, so for example if the diameter is doubled, the strength is increased by a factor 8.

Hopefuly this will help to explain the effect of the clamped bearings on the stub axle strength - whether it is required or not is a very different discussion and would need far more involved calculations. Based on the general level of conservative engineering in the Minor design, who knows. What has convinced me though is that I am definitely not going to remove the spacer and weaken the stub axle by a minimum of 35% and more likely a lot more.

Yes, I too remember the Comet crashes at the time.

[bmcecosse]

This rather assumes that clamping with a nut on a thread is the same as a solid tube.......

[IslipMinor]

Of course, what factor should be used to reduce the increase in strength? Even using 50%, which would be much too conservative, gives between 25% and 80% increase - a very significant improvement.

[bmcecosse]

And then - if the nut comes a bit loose - the extra strength is gone ! I do wonder if all this really was considered when the hub was being designed.... What does really surprise me is that Metric sizes were used - in a time when metric really was not the norm in British engineering.

[IslipMinor]

And then - if the nut comes a bit loose - the extra strength is gone

That's why it is secured with a split pin. In general if a nut comes loose there is a problem. That is why things are set to a particular torque, use split pins or other retaining methods, Nyloc nuts, spring and shakeproof washers etc.

The metric bearings and seal in the front hub have puzzled me as well - unified threads were still a bit new in the early 50's, let alone funny foreign things like metric dimensions! Is it related to the original design, because the MM uses nominal metric dimensions for a number of components, including the engine I think? Perhaps Mike Perry knows more about it?

[bmcecosse]

I think the sidevalve engine was 'stolen' from the French!!