TC front hub assemby with taper roller bearings - for amateurs
Posted: Mon Feb 28, 2000 2:17 pm
I recently asked about the correct sequence of assembling the front hubs of a
TC. I was overwhelmed by the advice given and especially thank Messrs.
Grunau, Old, Pleitner. McCrary, Furneaux for their insights. Having
completed the assembly, I thought it might be worthwhile to record my
progress step-by-step from the perspective of a rank amateur with only basic
handtools.
1. I decided to use taper roller bearings rather tha ball bearings. These
were purchased from Roger Furneaux's "Mad Metrics" as were new hubs ( the
splines on my originals being well worn and I am determined to rid myself of
the dreaded front wheel "clunks").
2. Stub axles were professionally crack tested and passed OK. Axle
dimensions measured by my 1" micrometer showed almost no wear compared to the
dimensions listed in TCs -Forever, page 103.
3. As many of the correspondents pointed out, the key to the success of
assembly is that the central "core" (inner oil seal tapered washer,inside of
inner bearing, original spacer, shims, inside of outer bearing, cupped
drilled washer, nut) should form a solid, stressed surround to the stub axle,
WITHOUT that stress being applied to the taper bearings via their outer
sides. This means that shims that match the "central core" to the hub must
be exactly tailored to your own components and their wear.
4. With a couple of extremely frustrating exceptions, assembly proved
reasonably simple and accomplished with minimal (many thanks Don Spurr!)
technical support.
As follows:-
5. Bolt stub axle to back plate and secure using the appropriate special
lock washers.
This enables the assembly to be firmly mounted in the bench vice, using fibre
protectors on the vice faces.
6. I measured up the inner and outer bearings to determine the offset between
the inner and outer rings. I did this by placing the bearings on a sheet of
glass and measuring the difference, which amounted to 0.053" and 0.054" for
each.
7. Based on this I had made two 0.100" washer shims with inner diameter
0.800" and outer
1.100" to match the original spacer.
8. I pushed the outer part of both bearings into the inside and outside of
the hub, securing with Loctite. I used the old bearing as a drift and
pressed home home with a matching (to the outside of the old bearing) socket
set. - Very satisfying; Roger's components were a superb fit.
9. I purchased a shim sheet set from my local engineering supplies store.
Through trial and error I discovered that adequate shims to match the spacers
can be made using tinsnips (outside) and ,surprisingly for the inside cut
out, a (cheap!) PAPER hole punch on shims up to 0.010".
Now the frustrating part!
10. Mount the stub axle in the vice, (leave out the inner oil-seal for the
moment).
Push on to the stub axle the inner oil seal cupped washer, inside of inner
bearing, hub.
Then from the front, mount he original spacer, 0.1" spacer, shims, inside of
outer bearing, cupped washer and castellated nut. This operation has to be
repeated many times until the shims added enable the stub axle nut to be
tightened firmly (I'm sure there is an appropriate torque setting) and at the
same time there is absolutely no "play" between the hub and the stub axle.
In fact there should be sufficient load on the bearing that resistance to
free motion has just been reached. Roger Furneaux tells me that this is the
point where the hub requires 3 lb-inches torque to rotate it. I'll leave it
to you to work out a suitable test rig to produce this - my wife wants to
know where her scale weights disappear to.
In my case I needed shims of 8 "thou" on one side and had to grind down the
new 0.100 spacer by 5 "thou" on the other side. Which meant, I assume,that
the original spacer was slighly long(?) to begin with.
11. Grind down the nuts, so that the torque is correct and the castellations
enable the split pins to be inserted.
12. Final assembly:-
Pack the bearings with grease, add the inner oil seal, repeat 10, -
hopefully for the last time and insert the split pin.
Comments welcomed.
John Steedman TC0301
TC. I was overwhelmed by the advice given and especially thank Messrs.
Grunau, Old, Pleitner. McCrary, Furneaux for their insights. Having
completed the assembly, I thought it might be worthwhile to record my
progress step-by-step from the perspective of a rank amateur with only basic
handtools.
1. I decided to use taper roller bearings rather tha ball bearings. These
were purchased from Roger Furneaux's "Mad Metrics" as were new hubs ( the
splines on my originals being well worn and I am determined to rid myself of
the dreaded front wheel "clunks").
2. Stub axles were professionally crack tested and passed OK. Axle
dimensions measured by my 1" micrometer showed almost no wear compared to the
dimensions listed in TCs -Forever, page 103.
3. As many of the correspondents pointed out, the key to the success of
assembly is that the central "core" (inner oil seal tapered washer,inside of
inner bearing, original spacer, shims, inside of outer bearing, cupped
drilled washer, nut) should form a solid, stressed surround to the stub axle,
WITHOUT that stress being applied to the taper bearings via their outer
sides. This means that shims that match the "central core" to the hub must
be exactly tailored to your own components and their wear.
4. With a couple of extremely frustrating exceptions, assembly proved
reasonably simple and accomplished with minimal (many thanks Don Spurr!)
technical support.
As follows:-
5. Bolt stub axle to back plate and secure using the appropriate special
lock washers.
This enables the assembly to be firmly mounted in the bench vice, using fibre
protectors on the vice faces.
6. I measured up the inner and outer bearings to determine the offset between
the inner and outer rings. I did this by placing the bearings on a sheet of
glass and measuring the difference, which amounted to 0.053" and 0.054" for
each.
7. Based on this I had made two 0.100" washer shims with inner diameter
0.800" and outer
1.100" to match the original spacer.
8. I pushed the outer part of both bearings into the inside and outside of
the hub, securing with Loctite. I used the old bearing as a drift and
pressed home home with a matching (to the outside of the old bearing) socket
set. - Very satisfying; Roger's components were a superb fit.
9. I purchased a shim sheet set from my local engineering supplies store.
Through trial and error I discovered that adequate shims to match the spacers
can be made using tinsnips (outside) and ,surprisingly for the inside cut
out, a (cheap!) PAPER hole punch on shims up to 0.010".
Now the frustrating part!
10. Mount the stub axle in the vice, (leave out the inner oil-seal for the
moment).
Push on to the stub axle the inner oil seal cupped washer, inside of inner
bearing, hub.
Then from the front, mount he original spacer, 0.1" spacer, shims, inside of
outer bearing, cupped washer and castellated nut. This operation has to be
repeated many times until the shims added enable the stub axle nut to be
tightened firmly (I'm sure there is an appropriate torque setting) and at the
same time there is absolutely no "play" between the hub and the stub axle.
In fact there should be sufficient load on the bearing that resistance to
free motion has just been reached. Roger Furneaux tells me that this is the
point where the hub requires 3 lb-inches torque to rotate it. I'll leave it
to you to work out a suitable test rig to produce this - my wife wants to
know where her scale weights disappear to.
In my case I needed shims of 8 "thou" on one side and had to grind down the
new 0.100 spacer by 5 "thou" on the other side. Which meant, I assume,that
the original spacer was slighly long(?) to begin with.
11. Grind down the nuts, so that the torque is correct and the castellations
enable the split pins to be inserted.
12. Final assembly:-
Pack the bearings with grease, add the inner oil seal, repeat 10, -
hopefully for the last time and insert the split pin.
Comments welcomed.
John Steedman TC0301