Semi Girling front hubs

[Dennis Nicholas]

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.

Yep I realise for tapered roller the hub would probably have to be different.......I do in fact have a Reliant which has a pair of tapered rollers at front whereby the outer races are held in the hub at a fixed distance apart and it is the moving together or apart of the inner races located on the stub that is used to set up the required end float........I have just completed a full careful rebuild of that cars front suspension.
I think Ball bearings have axial clearance as well as radial. (may be different or same depending on the type of bearing?)

Just out of curiosity I would like to know the actual figures for the internal clearance of the balls and race (axial) and the figures to show what the theoretical movement would be projected to the rim of the felt carrier if one side is pulled and the other side is pushed...........a different proposition to pulling and pushing both sides in the same direction at the same time when the movement would surely be the same as the bearing axial clearance? i.e. no magnification of movement due to turning moment around the centre of the balls/bearing at any distance from the centre.
Perhaps there is a bored mathematician/engineer out there that could amuse themselves with this little task 

Dennis

[Bob Culver]

Mention has been made of Minis. These have either ball a.c. races or taper rollers, both with a precision length spacer between the inner rings. On older vehicles considerable scope for misassembly. Many other taper rollers have no spacer and the nut is just finger tight and retained solely by the split pin. It seems primitive but umpteen millions of vehicles were like that. 
Bearing makers do publish specs for radial and axial clearance but as pointed out the tilt is a bit more complex (and much more).
Assessing used bearings is a puzzle for amateurs especially. The tilt is not an accurate indicator, although if a clean bearing with very thin oil has almost none it wont be significantly worn. But it might also not be ideal for the application (ie rear hub)

[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.

Yep I realise for tapered roller the hub would probably have to be different.......I do in fact have a Reliant which has a pair of tapered rollers at front whereby the outer races are held in the hub at a fixed distance apart and it is the moving together or apart of the inner races located on the stub that is used to set up the required end float........I have just completed a full careful rebuild of that cars front suspension.
I think Ball bearings have axial clearance as well as radial. (may be different or same depending on the type of bearing?)

Just out of curiosity I would like to know the actual figures for the internal clearance of the balls and race (axial) and the figures to show what the theoretical movement would be projected to the rim of the felt carrier if one side is pulled and the other side is pushed...........a different proposition to pulling and pushing both sides in the same direction at the same time when the movement would surely be the same as the bearing axial clearance? i.e. no magnification of movement due to turning moment around the centre of the balls/bearing at any distance from the centre.
Perhaps there is a bored mathematician/engineer out there that could amuse themselves with this little task 

Dennis

Not sure that this discussion advances Austin Seven maintenance so stop reading here if not interested.

Deep Groove Ball Bearings are manufactured in various internal clearances depending on the application:


  SKF Internal Clearance.JPG (Size: 28.81 KB / Downloads: 119)

The axial clearance is rarely quoted for Deep Groove Ball Bearings - if it is important then Angular Contact Ball Bearings are used:


  RHP Ball Bearing designations.JPG (Size: 138.14 KB / Downloads: 119)

The radial internal clearance is listed:


  Ball Bearing Radial Internal Clearance.JPG (Size: 91.06 KB / Downloads: 119)

The internal design of Deep Groove Ball Bearings is a series of Balls running on a grooved track. The relationship between the Ball and Track radius is known as Osculation (stop giggling that boy at the back of the class )


  Ball Bearing osculation.JPG (Size: 24.78 KB / Downloads: 119)

A ball running in a groove presents a slight difficulty- the outside diameter of the ball follows a rolling path at the bottom of the groove but as the contact rises up the track sides, the surfaces slide. 

A good design of Deep Groove Ball Bearing is a compromise where the osculation provides good support without too much sliding friction.

The groove width design can vary with each manufacturer and the axial movement is related to the groove design as well as radial clearance.

[Bob Culver]

Hi Tony

I looked up the very same info in NSK book a few hours ago. Are you going to explain what microns are?

I wonder if the taper bore K corresponds with the early Sevens!

My fastidious father used to replace roller mains about every 2 years.  He was sold various tolerances before he realised. He reckoned he could hear the differnce between one, two and three spot.

[Dennis Nicholas]

A micron is a metric unit of measurement where one micron is equivalent to one one-thousandth of a millimetre [1 micron (1μ) = 1/1000 mm] or 1 micron (micrometer) = 1/1,000,000 of a metre. Visualizing a micron. a human red blood cell is 5 microns. an average human hair has a diameter of 100 microns

(as an aside...I still wonder at some paint instructions that tell you how many microns of paint coat thickness to apply! )

Dennis