I agree completely that the bearing preload is important, but it's equally
impotent now, and it's not done with any accuracy. The current situation
is that the axle shoulders space the bearings and the hub nut torque sets
the load both on the inner and outer races. Common practice, but not
better (other than spacers being a more fussy method) that takes the shear
load (or at least part of it) off the axle.
I currently use a two pound residual pressure--it helps a little.
-----Original Message-----
From: Peter Vucinic [mailto:vucinic@b140.aone.net.au]
Sent: Tuesday, September 09, 2003 6:07 AM
To: Friends of Triumph
Subject: Re: TR6 Axle Mod
I thought I might 'chime' in on this one as well. I think someone in the
group earlier said something along the lines of 'fixing one problem may
lead to another'. In my opinion, I think that this is a distinct
possibility in this case.
I see the merits of the engineering principals in this case to increase
the bending moment of the stub axle. However, care must be exercised, as
when we become focused on eliminating one problem we may, however
inadvertently, induce another problem. This secondary problem may not be
immediately obvious, nor may it prove to be a 'major' problem. This is
true, as long as we understand the full impact and consequences of what we
were trying to originally achieve, and that we are willing to take any
secondary problems that are a consequence.
The issues that I can see with this modification are:-
1. Pre-load and/or zero clearance, is extremely difficult to measure/set
without using some sort of torque gauge set-up. Therefore a consistent
torque setting 'accuracy' cannot be achieved. 2. The risk of excessively
pre-loading the hub/bearing assembly is great. If excessive pre-load is
inadvertently applied to the bearings, it will be detrimental to the life
of the bearings/hub unit. Excessive pre-load will lead to excessive heat
through increased operational friction. Excessive heat will of course
oxidise/degrade the lubricant rapidly. Metal-to-metal contact will occur
and if left un-checked, bearing failure/collapse is the resultant. 3.
Every time you change a wheel bearing set you will need to re-shim the
assembly to obtain the correct torque/pre-load. 4. Bearing clearance is
the norm in our type of front hub assembly. This is to accommodate for
thermal expansion of the hub. This is typically required due to the heat
generated by the braking components (disk rotor/pads) of the hub. Also,
there is less chance of a bearing failure with an end float setting as
opposed to a pre-load setting.
If this method of increasing the stub axles bending moment is employed to
avoid 'pad knock back', great care should be taken in setting up the hub
assemblies to obtain the 'correct' hub rotational torque which is directly
related to the pre-load. The hub assemblies should be disassembled at a
much lesser frequency than that of a STD hub assembly to replace the
lubricant.
As an adjunct to this, I also wondered whether anyone has investigated the
possibility of plumbing in a 3-5 PSI residual pressure valve in the front
line to ensure that the disk pads are kept up against the disk rotors?
Just some of my thoughts.
For those of you who wish further information here is a link
http://www.timken.com/products/bearings/techtips/PDFs/Vol6No3.pdf
Kind Regards
Peter Vucinic
WORKS-4
TR-4
|