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Re: 1938/1939 rear axle dilemma.

Bob Culver
Hi Dennis

I am a bit confused by the 25.4, 34 , 20 mm overall length pairs and which has/had the longer inners. (Normally assembled back to back these protrude, as per early models. Is it not practical to accommodate using appropriate spacer to pinion?)


Jeff is hopefully putting up scans of the drawings sent by RHP which should show all dimensions and gives instructions for fitting.

Dennis

Location: NW Devon

Re: 1938/1939 rear axle dilemma.

In SKF inch series bearings the number indicates the bore in 1/8 of an inch hence 11 is 11 x 1/8" = 1 3/8".

Cheers, Tony.

Location: Melbourne, Victoria, Australia.

Re: 1938/1939 rear axle dilemma.

Tony Press
In SKF inch series bearings the number indicates the bore in 1/8 of an inch hence 11 is 11 x 1/8" = 1 3/8".

Cheers, Tony.


Aaah. Another grain of knowledge to be taken in. Thanks

Location: W Devon

Re: 1938/1939 rear axle dilemma.

Bob Culver
Hi Dennis
.012 does seem excessive if due “wear” and probably not prudent to reuse even with packing, although from the few I have seen seems the nut often loose and the spacer worn which would account for.


The inner track each of the 38MJT25 pair looks rather worn and scored so I expect that is where the end float is caused.

I did tighten the nut up a little ( about 3 degrees of turn to check if spacer between thrust pair and roller had "shrunk" a bit but no difference.

I am a retired electronics professional and my mechanical engineering knowledge has only been gained over the years from playing with old cars and reading up on various aspects and some from experience when working on our ships on the mechanical bits involved with the electronics e.g. radar scanners and various sizes electric motors etc.
So my mechanical engineering knowledge is quite well down the information scale!
I have a medium size lathe but lack the skill/knowledge to do anything really meaningful/skilful with it and certainly not precision work!!

Dennis

Location: NW Devon

Re: 1938/1939 rear axle dilemma.

Uploaded via Photobucket are Dennis' RHP drawings - not sure how long they'll stay up given Photobuckets recent policy changes, so make the most of them while you can.







Jeff.

Location: Almost but not quite, the far North East of England

Re: 1938/1939 rear axle dilemma.

Thank you Jeff.

The one thing I do not fully understand the meaning of is the wording:-

"Groove side of inner to be flush to 0.025 mm above stamped face of outer when a gauging load is applied to stamped face of outer".

I believe this is the wording on the original drawing and was aimed at British Leyland as a technical part of the bearing description, rather than as part of info to me for the modification by me when using in the A7 axle as a pair of thrusts.

I have just looked at the 38MJT25 pair and the balls and raceways that they run in are quite pitted. I can't see a "groove" to distinguish the "groove side".


Dennis

Location: NW Devon

Re: 1938/1939 rear axle dilemma.

I am not sure why these drawings were made- it appears that the two R&M bearings suggested were a wheel bearing in the early style with reduced width outer ring of 10 mm vs 17 mm inner ring.

Could have almost been as easy to use a standard SKF 7305B at 17 mm wide, but if the original bearing was a R&M 3MDJT25 with 25.4 mm width seems a lot of messing about with spacers and a serious risk of ruining the pinion/crown wheel mesh.

Simpler to fit an SKF 3305A and the original spacers. although a lower thrust capacity.

Also eBay seems to have old stock 3MDJT25 bearings often listed for MG/Morris use as well

http://www.ebay.com/itm/NOS-R-amp-M-BMC-Front-Bevel-Pinion-81933-3MDJT25-MGTB-MGTC-1935-1948-Morris-/331756047117

I would suggest go back to the original design and not mess about with the drawings which use the two A/C bearings.

Cheers, Tony.

Location: Melbourne, Victoria, Australia.

Re: 1938/1939 rear axle dilemma.


Thanks Dennis and Jeff.

Generally back to the start!

Had drafted this much as Tonys answer.

The 38MJ... with protrusion on the back face and proportions so unusual I thought I was misreading.

I think I would have opted for a spacer ring instead of reducing!

Considerable mods have obviously been accomplished before. If the one piece assemblies are not reasonably available, and common metric a.c not too expensive, is it not possible to go further and move everything toward the pinon and accommodate 17mm outers? Means remaking the bearing housing piece, a bit of a mission; finishing to .00025 for bearings is tedious, altho not sure if essential.

The spacer needs be got right first time to avoid repeat removal of the bearing. Dummy bearings would be helpful. With roller pinion diffs the pinion can be easliy removed to check mesh.

Location: Auckland, NZ

Re: 1938/1939 rear axle dilemma.

Update.

Pinion Angular contact dual purpose bearing single inner 2 outer Original 3MDJ25 located and 2 bought (1 for use and one for future) £45 +VAT @20% = £54 each.

Pinion Roller MNJ 1 1/8 £32 + VAT @20% = £38.40.
finally should be on way in post after I collect a wrong one (ball) then a problem between the supplier and retailer trying to identifying the right one. (so far no price adjustment).

Diff thrust (Ball) ALS11 (LJT 1 3/8 inch) located and a pair bought £35 + VAT @20% = £42 each = £84 for the 2 required. (Old ones removed may be ok...not yet minutely scrutinised).

Hub bearings SKF6207 (R&M LJ35. 35 X 72 X 17mm ball) Located and bought £6.55 + VAT @ 20% = £7.86 X 2 = £15.72


See next post for next problem oil seals

Location: NW Devon

Re: 1938/1939 rear axle dilemma.

Next problem - Oil seals
The next problem is to identify modern lip seals in the axle casings for the larger half shafts to replace the old felt seals.
I note from previous correspondence with Coopers Payen Ltd that I eventually used their NB084 (now obsolete of course!!). There was a big question mark because they are handed with a helix as well as the lip seal so one shaft would be rotating the wrong way in the seal....HOWEVER I went ahead and fitted one on each side and over many thousand miles have had no problem with leak down casing to brakes.
I am just about to take one out to see what state it is in and how I fitted it (in axle case or in the felt holder?)

Hope to save vast amount of research time by someone knowing of a supplier of the modern seal suitable. Bearing in mind it is the larger 1.015 inch half shaft (earlier pre July 1938 were thiner)

Same for the oil seals to replace the felts in the larger hubs. with the 35 X 72 X 17 mm bearings (may just have to continue using felts?)

Location: NW Devon

Re: 1938/1939 rear axle dilemma.

Dennis,

"Same for the oil seals to replace the felts in the larger hubs. with the 35 X 72 X 17 mm bearings (may just have to continue using felts?)"

Why not use double sealed bearings SKF 6207 2RS instead of Hub bearings SKF6207

Shouldn't cost much more than the open bearings (£6.55 + VAT @ 20% = £7.86 X 2 = £15.72) and save on grease !

Location: Melbourne, Victoria, Australia.

Re: 1938/1939 rear axle dilemma.

Tony
Too late as already have the SKF6207........I didn't think about it at the time of ordering.

Will however be putting in prop front end ball with one shield on front of bearing.

Location: NW Devon