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Assembling 1938/39 rear axle casing - Dennis Nicholas - 28-09-2017
1938/39 (heavy) back axle assembling.
I am just about to put the diff/shaft assembly back into the axle casings after all new bearings on the axle. The thrust bearings are fitted to the diff carrier; one went on too easily so was removed and put back with LOCTITE and the second one also had LOCTITE applied but it proved more difficult and took a lot of (fairly gentle) knocking on with hammer and drift (against inner race obviously).
I don't know how good a fit the outers will be in the case.....I didn't try them while they were off
I know that they will need to be able to be moved in their housing to get the correct backlash so assembling with LOCTITE is not an option so hoping they will be tight (the ones removed by unscrewing the adjusters were a good fit
)Question
What is the best way to fit the casings assuming the thrust bearing outers are going to be a good tight fit in their housing?
Thoughts/musings
1. Put one half at a time on......starting with which half?
2. Don't like the idea of pulling the 2 halves together with the bolts around the flanges incase of distorting.
3. Don't like the idea of putting one end on wood block on ground (with hole for half shaft to sit in) and hammering on other end (via block of wood) as I am aware that shock will be transmitted via outer race to balls against inner race and possibility of thus creating small indentations on the races.
4. Heat around casing by bearing housing then combination of pushing, drawing together with bolts and gentle knocking on end as in 2??
I have one of those induction heaters with the long element that can be wrapped round the case. I have not had any experience of heat application so would be working blind as to how HOT to get it before bearing race would go into housing easily and how quickly it would cool down and require further heating to continue the process.
5. I have a floor standing hydraulic press which I could probably find a way of rigging up wood blocks at each end of casings to push the 2 halves together, perhaps with added heat as well?
All comments gratefully accepted.
I am being somewhat fussy about this car rebuild because I am getting on in age and expect this to be the final major work I will ever have to do before having to retire from driving and am expecting around 65 - 70 bhp to be being put through the transmission.
Dennis
RE: Assembling 1938/39 rear axle casing - Tony Press - 28-09-2017
(28-09-2017, 10:34 AM)Dennis Nicholas Wrote: All comments gratefully accepted.
I am being somewhat fussy about this car rebuild because I am getting on in age and expect this to be the final major work I will ever have to do before having to retire from driving and am expecting around 65 - 70 bhp to be being put through the transmission.
Dennis
The standard bearing design is-
rotating rings -tight fit
stationary rings- loose fit
Usually Longbridge followed this, so the diff bearings should be a sliding fit in the housing.
As long as the bearings enter the housing squarely the side tubes should slide on easily.
Cheers, Tony.
RE: Assembling 1938/39 rear axle casing - Bob Culver - 29-09-2017
Bearing fits are tricky. The difference between an easy fit and tight is incredibly small, and even ball races have tolerances. Comparison by measuring is difficult even when transferred to one mike. Vernier callipers too caorse although can be used as agauge. Nails can be filed to length as rigid precision internal gauges. Or can turn up test plugs or rings to determine exact size and shape and for easy comparison. Are the housings clean and unbruised? The ball race edges to the radius can be eased. Tony, or Machinerys Handbook etc can provide typical recommended fits. Very slight easing may not be a crime.
If intending to drive anything Seven based with 70bhp (net!) I would not anticipate a long driving future either!
RE: Assembling 1938/39 rear axle casing - Dennis Nicholas - 29-09-2017
Tony and Bob thank you.
I hope to pluck up the courage to try the assembly today.
In our youth we often just used to do some of the jobs in blissful ignorance but with age and a lifetime of experience and learning one is aware of pitfalls and sometimes their disastrous consequences (written off engine parts/axles etc).
I do envy those with the engineering skills to be able to make precision parts.... but then my electronics/electric skills have proved very useful.
I still feel that there is a requirement for a good publication that contains all the DETAILED tips and "How To" information gained over the years for working on the Austin 7. I have found that whilst the books like Bill Wiliams special builders guide, 750 'companion' and its predecessor, 750 special builders guide, are very useful they so often lack essential DETAIL of how or what and just rehash previous vague articles albeit with a few tips thrown in.
Forums are an excellent place to glean information but can be oh so time consuming to sift through for scraps of relevant information and each 7 club has its own so asking questions can be a tedious operation repeating them on numerous forums then looking back on each for answers. I feel there should be one Austin 7 forum to which all could contribute. It could have local sections where those interested only in local chit/chat/events could go for their information. It could have an ever growing technical section becoming virtually a works like workshop manual.
Tony's information above about bearings is a good example of basic information that would be a very big help included in a publication. The publication should be available in ring binder form so that pages (in plastic envelops) can be added as more information on each subject is found out. (see my PS below) Modern computers and printers are wonderful tools to enable such a thing.
Those that worked on the 'companion ' are to be applauded for the time and effort they gave, but I still feel that having bought it I found it a disappointment. A good example is the lack of information on the 1938/39 axle. It is almost as if it doesn't exist.
A huge thanks and debt is owed to those that are dealing with the A7CA archive. I have learned a lot from the works spares books, now freely available on line, and now know more about the later axle through the 1586A publication and even the Big 7 version and later spares publication and also the cards showing in depth works modifications. How lucky we were that they were saved.
Rant nay thoughtful musings over.....back to work.
Dennis
PS my running of Reliant Scimitars (GTE and GTC) has led to my having the Makers workshop manual in ring binder format which is ever growing with corrections to erroneous information in the original and with further more detailed how to articles which fill in the gaps where professional mechanics/engineers would have been expected to already have the "basic" knowledge. Yes I do frequently pass on the knowledge and answer questions on that club forum.
RE: Assembling 1938/39 rear axle casing - Dennis Nicholas - 29-09-2017
(29-09-2017, 08:57 AM)Bob Culver Wrote: Nails can be filed to length as rigid precision internal gauges. Or can turn up test plugs or rings to determine exact size and shape and for easy comparison. Are the housings clean and unbruised? The ball race edges to the radius can be eased. Tony, or Machinerys Handbook etc can provide typical recommended fits. Very slight easing may not be a crime.
If intending to drive anything Seven based with 70bhp (net!) I would not anticipate a long driving future either!
Will sort out my tin of old nails and have an experiment. However elastic micrometer (or is it me ?) does not fill me with confidence!!!!
Long future
It has lasted around 60,000 miles with old engine 948cc about 45 bhp which has included mostly road use and also a few Classic (MCC) trials. New engine 1275 (breakers yard 40,000 miles from crashed car) it was available and reasonable priced to replace 948, which broke 1 piston/rings, and is virtually same external physical dimensions and almost direct fit exchange - givs about 65 BHP. (+ bit extra for a mild cam to be fitted).
Death of pinion thrust ball races .....about 12 thou end float found in pinion......probably more due to old age wear than excessive power? Now that I will be using the AFMT (Prolong/Synionic) there will be even less friction/heat/wear so longer life.
Age and sensitivity will dictate that I really will be gentle as possible with my baby!
Interest is in economy, reliability over long distance runs and being able to keep up with motorway traffic as required so as not to be a hazard and to be able to drive out of a hazard if needs be rather than boy racer.
I hope and think it will outlast me!
Dennis
RE: Assembling 1938/39 rear axle casing - Tony Press - 29-09-2017
(29-09-2017, 03:16 PM)Dennis Nicholas Wrote: Dennis,
I would be very careful using AFMT in a ball or roller bearing (even their website doesn't seem to suggest this) because they are antifriction bearings- but they rely on a modicum of internal friction to 'roll' correctly- any slippage of the balls/rollers can cause 'smearing' of the tracks.
The crown and pinion are plain spiral bevel and only have rolling contact so a good thick lubricant suffices here.
20 years as a lube engineer made me very suspicious of any magic fluids- not much of it about since Merlin died.
Cheers, Tony.
RE: Assembling 1938/39 rear axle casing - Dennis Nicholas - 30-09-2017
(29-09-2017, 11:54 PM)Tony Press Wrote:(29-09-2017, 03:16 PM)Dennis Nicholas Wrote: Dennis,
I would be very careful using AFMT in a ball or roller bearing (even their website doesn't seem to suggest this) because they are antifriction bearings- but they rely on a modicum of internal friction to 'roll' correctly- any slippage of the balls/rollers can cause 'smearing' of the tracks.
The crown and pinion are plain spiral bevel and only have rolling contact so a good thick lubricant suffices here.
20 years as a lube engineer made me very suspicious of any magic fluids- not much of it about since Merlin died.
Cheers, Tony.
Thanks tony.
Attached is the SINTEF lab report which you would be able to understand more fully than I so any further observations would be welcome. Merlin's home town,Tintagel, is not far down the road across the border in Cornwall so I ought to pop down and see if he is home and can enlighten
RE: Assembling 1938/39 rear axle casing - Tony Press - 30-09-2017
(30-09-2017, 12:25 AM)Dennis Nicholas Wrote:(29-09-2017, 11:54 PM)Tony Press Wrote:(29-09-2017, 03:16 PM)Dennis Nicholas Wrote: Dennis,
I would be very careful using AFMT in a ball or roller bearing (even their website doesn't seem to suggest this) because they are antifriction bearings- but they rely on a modicum of internal friction to 'roll' correctly- any slippage of the balls/rollers can cause 'smearing' of the tracks.
The crown and pinion are plain spiral bevel and only have rolling contact so a good thick lubricant suffices here.
20 years as a lube engineer made me very suspicious of any magic fluids- not much of it about since Merlin died.
Cheers, Tony.
Thanks tony.
Attached is the SINTEF lab report which you would be able to understand more fully than I so any further observations would be welcome. Merlin's home town,Tintagel, is not far down the road across the border in Cornwall so I ought to pop down and see if he is home and can enlighten
I think that proves my point- reduced friction ! Note that the tests are metal on metal simulating plain bearings not rolling or anti-friction bearings.
Regarding the use of extra additives in motor oil - all current reputable oils are all made from either a synthetic or mineral base oil with upwards of 15-20% additives - all carefully balanced to work harmoniously together.
The addition of another package of additives can cause problems with the functioning of the original additive package.
Plus I would think the additive suppliers would have investigated most available friction reducing additives to combine with the various other additives to get the optimum result.
Cheers, Tony.
RE: Assembling 1938/39 rear axle casing - Bob Culver - 30-09-2017
Hi Dennis
Your observations about information are similar comments I made recently on old Forum but cannot now find. However for decades enthusiasts had to make do with the likes of Pitman or Nicholson. Many would never have seen or heard of an owners handbook or parts book, and then only for their model.
A problem now is the volume of material, much of it obsolete, poor advice, or with errors. The knowledge required to sift the wheat from the chaff is such that those with knowledge have little cause to read anyway, and newcomers, even if they manage to find all and make the huge effort to read, are largely bamboozled. Ideally old articles need to be pruned, corrected, categorised, assembled or indexed together, and rated with emphasis given the more succinct and useful, and with a summary of errors if these cannot be fixed. Including those in the books. Many old Forum responses gave succinct summaries on topics but were, like this, under unrelated headings and were unfortunately hard to find, and now increased so.
But it would be a huge job and those able are not numerous and have other things to do. Passing on what to them is basic stuff to what in many cases seems to them to be bumbling amateurs does not appeal to all of the experts. And some regard as intellectual knowledge to be dispensed sparingly.
The gap between basic skills and application is difficult to cover without related experience. It is what apprenticeships were largely for. It has always been difficult to find books which cover the transfer of basic workshop skills to real machinery. Even many “mechanics”, and esp modern ones, lack ability other than with their standard routine work. In another Club over the decades I have observed skilled fitters, technicians and the like do well, and a surprising number of able woodworkers. Observant attention to detail and fits seems to be important.