Banjo axle 1928. rear pinion bearings

[scrooge]

I am just replacing the pinion bearing in my Chummy axle and the new bearing for the rear of the pinion (ie just forward of the gear) differ from the original in as much as it has no method of confidently retaining it in place.
The outer race of the old one had a smaller bore at the forward end and hence would not pass the rollers and drift into the diff. The new one doesn't and whilst it was a good interference fit in the torque tube, and Loctite bearing adhesive used abundantly, I cant decide if I should take it apart again and perhaps fit an oil thrower between the bearing and the pinion gear. the thrower being of sufficient diameter to impede an errant outer race attempting to a approach the crown wheel.

I wondered if anyone else has a  tackled this before ?

Any advice welcomed.

[Chris KC]

I've never been inside a pre-29 axle myself, but I believe the correct bearing has a floating outer race (the rollers are retained axially by the inner race). The OR simply presses into the housing; and if not a good fit might indeed benefit from a spot of 'bearing fit'. But don't take my word for it...

[Howard Wright]

Hi

Please those with more knowledge correct me but...

I think that the pre 1931 torque tubes retain the pinion shaft by thrust bearings and a thrust adjusting nut that bears against the pinion flange. That means adjusting the mesh is effected by moving the whole tube closer to or further away from the crown wheel thus necessitating a sliding bearing just behind the pinion gear.

Later torque tube pinions have a threaded portion closer to the crown wheel and are retained by a nut two thirds the way along the shaft. So only this portion of the shaft is moved back and forward by adjusting shims. and the pinion bearing is fixed not sliding.

I'm most familiar with the screw in torque tube where the pinion bearing closest to crown wheel is definitely a sliding fit and can be moved in and out by screwing the tube in or out to mesh properly with the crown wheel.

Hope this helps.

Howard

[scrooge]

Thanks gents.
The bearing I have fitted does allow the rollers and inner race to slide . Its just that there is nothing stopping the outer race passing rearwards toward the crown wheel.
The bearing I removed couldn't have been the original as it was RHP  MRJA 7/8 . I remember Ransome and Marles being taken over by Hoffman as my brother worked for RHP in the tool room. This bearing would allow some movement but would not allow the outer race to pass the rollers . It could be my brother made the bearing for our father when he rebuilt this axle in the 80's .   The bearing was pitted as the axle had been left partly disassembled since early 90's  , it felt a bit graunchy when turning the torque tube flange but that was the thrust bearings I think.

 My father shortend a latter D type axle for the Chummy as he got tired of the oil getting into the brakes. The half shafts were used in the later axle . This is still on the Chummy but I thought I would return it to original. 

I think the twin thin locking nut arrangement at the front of the toque tube (behind the flange) are used just to set the thrust bearings preload.   The sleeve at this same end with its castellated peen retention for the seal is hopelessly fragile , as there are  virtually no lugs left, ive used a sealed bearing at this end.

The mesh between the crown wheel and pinion is  by shimming between the torque tube and banjo casing.

I think ill go ahead with the new bearing , I had to warm the torque tube to fit the outer race and also applied the Loctite stud and bearing glue.



 Thanks for thoughts

Charlie

[scrooge]

As ever, read Jack French  and all will become clearer.
Ive just remembered Jack French had some notes from his lectures around 1953 published , these feature on page 165 of my 1980 A7 Companion.
Regarding the interchangeability of rear axle parts part 3 refers to conversion of banjo axle to roller race type bearing, he suggests that to stop the outer race approaching the crown wheel you should fit a peg and also a distance piece to prevent it moving forward.

I am not sure it could move forward as it is home against a shoulder in the torque tube.

[Chris KC]

Well spotted Scrooge!
I dare say Loctite would have much the same effect but you know where you are with a mechanical stop.

[Bob Culver]

Just curious but what exactly does the oft used expression banjo refer to? Am now cofused as to just which era of axle is being pondered.
I am familiar with the roller retaining peg on post 1934 axles and the need to fit when converting 1933 type to rollers.

Wyatt 3rd Editon p204 reprints a 1928 Austin publication with roller pinion bearing  and no retention method is apparent.
The loading may be such as to always encourage forward. If bearing is at all recessed, can the lip be gently peend over?
Unless some teeth pass thru, it should never need replacing in anyones lifetime!

[David Stepney]

Bob,

The term banjo when applied to a rear axle refers to the fact that, if you look at the centre casing of a three piece axle, it is circular with a small nose sticking out, a bit like a banjo with its fingerboard.

David.

[Tony Press]

The Banjo Axle now refers to the type having a nosepiece with the crown wheel and pinion which bolts into a double armed 'banjo' axle housing, but the early Austin 7 differential with torque tube bolted on to the central differential 'drum' more resembles a Banjo.

Regarding the 'loose outer ring' pinion bearing  originally fitted to the 1928-1929 short nose bolt on torque tube differential  (R&M or RHP MRJ 7/8 , SKF CRM 7) I have not heard of an outer ring (which should be as good tight fit in the Torque Tube nose) moving into the crown wheel.

The later fitting of a stop pin indicates that possibly this sometimes happened but with a good tight fit I think you should be OK.

The roller bearing with double inner and single outer ring lip was sometimes produced for special applications to accept very light axial thrust but this was never used in the Seven differential, given the great difficulty of aligning the thrust bearings with the roller outer flange.

[scrooge]

Thanks Tony.
I think I may be worrying about a very unlikely event.
I have spotted that the RHP MRJA 7/8" bearing my dad must have fitted in the early 80's would solve the problem if it existed. They are still available , or at least I spotted the equivalent on simply bearings website but at £106 a throw, I may take a more detailed inspection of the pitting in the one I have.

Anyway, now i'm on to the fun bit, pushing the diff carrier back and forth to measure the end float with a DTI poked down the mouth of the casing which I cant see to read.  . And then onto the dreaded engineers blue.

regards

Charlie.