Semi Girling front hubs

[Bob Culver]

Hi Tony

It can be difficult. A mechanic colleague bought Javelin fwbs SKF brand from a major supplier. Failed even sooner than normal. Turned out fake. Some years ago the mainshaft bearings in my wifes Sentra failed woefully. Had never tackled a modern so replaced diy.All the bearings were Jap except the most simple dead common one, which was Polish or some such. Failed in about 25,,000 miles, although the buyer did not twig.....(incidentally the local agent said they used the cars to train appentices. Had repleced several hundrd pinion bearings! The rollers were hugely reduced in dia and the oil like silver paint but not esp noisy.)
And for anyone tinkering with Sevens, trailers etc have to be on alert for ac races where not intended (or fitted reversed!)

[Tony Press]

SKF unfortunately have a manufacturing Plant in China- given Australia's nasty attack by China I think all companies who manufacture in China may face an uncertain future, especially with China supporting Russia in trying to start WW III

Sounds ominously like 1939- don't they watch any of the many offerings on WWII 

Unhinged Dictators again.

[Dennis Nicholas]

I wonder what any objection to fitting tapered roller bearings to A7 front hubs might be.......apart from finding any with cup and cone the right diameter and width to fit in hub, around stub and between hub and felt carrier with washer.
The tapered roller bearings fitted to some cars  have a spacer between inner and outer bearing so locking nut and 2 bearings against the shoulder of the stub.
The axial clearance, usually around 0.002 to 0.007 inch is achieved by shims between spacer and inner cone (outer race of a bearing = cup and inner = cone)...the thicker the shimming the more the cups of inner and outer bearings move apart and being tapered roller bearings the smaller the end play.
No fiddling with a split pin.
Nice and easy to set up with sets of correct ID shim washers and hub nut can be done up tight.  With tapered roller bearings on one of my cars, for MOT I take along my DTI if I know MOT man is not knowledgable to demonstrate the end float of the wheel being as specified in the manufacturer's workshop manual (or bearing manufacturer's end float requirement for the pair of tapered roller bearings).

I would think that if the edge of the A7 inner hub (officially called the felt carrier in the Austin spares catalogue) had 1/16 inch back and forward (i.e. radiall) play then since that is 0.0625 inches, then 62 thou play in the bearing axially is surely far too much?  Put simply that means that with the balls against the cone (inner race) there is a gap of 62 thou between the balls and the cup (outer race)? (assuming the cup is a good push fit in the felt carrier and the cone is a good push fit on the stub and all the play is in the bearing.

Dennis

[Bob Culver]

I presume the outer edge of the bearing housing was referred to. It is abot 4X the radiius of the ball track and the bearing tilts to more than twice the pure axial clearance, so about .007 which is not so great. But pure radial is what matters. The Seven set up is reasonably fool proof whereas taper roller, a.c , ball races fitted like rollers etc  are not
Compared with other cars the bearings are very large, esp when modern uprated ratings are considered, and failing is not a problem Design was empirical and some post war cars driven much harder than previous were short lived  on ball bearings; early Minor Javelin etc,. I had a colleague who lived at a radio station on a winding road miles out of town, where his girlfriend lived. He went thru front tyres and bearings on his MM at a great rate.
Taper bearings force the grease out and should be periodically repacked whereas ball races recycle it and with modern non drying greases need no attention, as moderns.
On Javelin cars the outtr bearing is locatd in the hub, not the inner. Held by a screwed ring which suffers even more from amateur attention than the typical Seven hub, most of which have been prised apart by owners without a puller.

[Dennis Nicholas]

 It is the inner bearing that has the slop...radial play 1/16 inch at the edge of the plate. Seems too much to me. 

Erich in Mukilteo

That to me seems to say that the outer edge of the felt carrier (inner hub) is moving forward and back (radially) (at 90 degrees to the stub) by 1/16 inch (as opposed to towards and away from the chassis (axially))?

perhaps Erich could clarify?

Dennis

[Erich]

Dennis, grabbing hold of the inner plate as it sits on the stub, and without the outer bearing or outer plate installed, the outer edge of the inner plate can move in and out approximately 1/16 inch. The outer bearing, also has about the same amount of play. However, when assembled the plates(inner and outer) have slightly less than 1/16. Since the bearings on both sides appear in good shape, I'm speculating that the Indian bearings have intentionally no play, whereas the Hoffman English bearings have intentionally some play. If I had my preference, a little play is what I would want. While the ones with no play don't bind, they are tight enough that when spun without a drum or wheel installed, the carrier plates will only spin about 1 1/2 times as opposed to the other side which will go three or four revolutions. Not very scientific, I admit, but the Indian bearing side will drag a bit.

Erich in Mukilteo

[Dennis Nicholas]

Terminology.....looking at the diagram on page 1, there is a swivel pin and a hub cap. Movement in the direction between swivel pin and hub cap is axial movement i.e. movement along the axis of the stub axle.  At 90 degrees to axial movement is radial movement.

The inner race of the inner bearing is a tight push fit onto the stub and it sits against the inner shoulder of the stub. The outer race of the inner bearing is also a tight push fit in the felt carrier (I presume what you are calling the "plate" is the felt carrier...sometimes referred to as the inner hub).

Since the inner race is fixed against the stub axle shoulder and is tightly held in place it will have no axial movement on the stub.  Since the outer race is held firmly in the felt carier it has no axial movement relative to the felt carrier (inner hub/plate). Therefore if there is axial movement of 1/16 inch that can only be due to clearance between the balls and the races in an axial direction...axial clearance.   My thought is that 1/16 inch is excessive. 

The assembly is - hub nut against outer bearing inner race -inner race against spacer -spacer against inner race of inner bearing - inner race of inner bearing against stub shoulder.
 The inner bearing outer race sits against a shoulder in the felt carrier (inner hub/plate) and on the inner side of the outer race it presses against the felt seal plate which is dished so the inner race does not touch it; then comes the felt seal which sits against the inner lip of the felt carrier (inner hub/plate.)...the felt gets a bit squashed between the felt seal plate and the felt carrier (inner hub/plate).

If you look at the A7 Friends ARCHIVE section you will find LISTS OF SPARES  for different years/models of 7 that can be downloaded and printed out.  These spares lists can be useful  for naming the parts being discussed so we are all talking about the same thing.

Hope this is of some help.

Dennis

[Erich]

Thank you, Dennis. I have contacted one of the cherished suppliers for new bearings and felts and will at some point in the near future change out both o/c and n/s.

Erich in Mukilteo

[Tony Press]

A couple of items.

If the inner large bearing is still a good fit on the stub shaft and in the felt carrier the 1/16" wobble in the felt carrier is the  internal movement in the bearing (magnified at the rim of the felt carrier).

The internal clearance in a bearing is the radial clearance - if the ball groove radius in the bearing rings is larger than the ball diameter then the rings can move axially even with a small internal clearance. This is not a problem with the outer ball bearing keeping the hub upright.

The hub housing design is made for a pair of ball bearings. If taper roller bearings were installed the housing would have a quite different design.

Austin Seven hubs have survived for 100 years - if you want a car with taper roller bearing hubs then buy a different car.

Most modern cars now have hub units which usually use ball bearings.


  Modern Car Front Hub.JPG (Size: 20.71 KB / Downloads: 102)

[Erich]

Tony, I completely agree. The n/s with the play is what I would expect since when everything is installed, there is very little play left. I suspect the issue lies with the bearing on the o/s which doesn't have nay play at all. The issue is that while it doesn't bind, I believe that it should have some play as there will be a build up of heat. In the end, I've ordered two sets of bearings and will replace at least the o/s. Even with my Minis, I remember backing off a bit after tightening. I just don't like a bearing that while not binding, doesn't spin as freely as it should. Personally, I don't think there is anything wrong with the Austin design. My motorcycles always just had caged ball bearings.

Erich in Mukilteo