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yorkshire_spam
November 29, 2017, 10:04am Report to Moderator

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Hi all,
Wimpus' recent gearbox related activities have got me thinking.
The RMS8NR/MJ1NR/MS10K - pn 104433 input and output shaft bearings are getting harder and more expensive to source.
Current best prices I can manage are around 15 quid per bearing for "European budget quality" or between 30 and 35 quid per bearing for good named brand (SKF/FAG/STEYR etc.)

Which got me wondering.... what purpose does the snap-ring serve? Since the corresponding RMS8/MJ1/MS10 bearings are easier and cheaper to source.
Is it there for location or retention?

Cheers, Sam
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glang
November 29, 2017, 10:29am Report to Moderator

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Unfortunately I think the snap rings prevent bearing movement due to the thrust forces developed by the helix type gears used in these boxes. If they were straight cut it would be another matter but then there would be other problems.....
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yorkshire_spam
November 29, 2017, 10:38am Report to Moderator

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Quoted from glang
Unfortunately I think the snap rings prevent bearing movement due to the thrust forces developed by the helix type gears used in these boxes. If they were straight cut it would be another matter but then there would be other problems.....


I thought that too, but I can't see how the bearings could move into the box (due to the internals) and they certainly don't stop the front bearing being pushed out (as I could clearly see on my box when the circlip snapped - the front bearing was pushed about 3mm forwards.
I'm wondering if blocking the outer race against the bell housing/tail casing might be possible and serve the same purpose without needing the snap rings.

You could quite easily be right though - it could be a VERY stupid idea.
I'd also wondered about taper roller bearings.... but that's another story!

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glang
November 29, 2017, 10:43am Report to Moderator

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Dont forget that the thrust forces go in both directions depending on whether the car is under power or not. Trouble is we dont know how much force is generated and if some loctite would sufficient to hold the bearings....
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yorkshire_spam
November 29, 2017, 10:53am Report to Moderator

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And looking closely at RKC634 the overdrive adapter casing, there's clearly a recess in the face for the snap ring, so even if the input shaft bearing can move forward the output shaft bearing is going stay where it should.
Oh well, probably a non-starter.
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JumpingFrog
November 29, 2017, 10:57am Report to Moderator

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I've been trying to source these bearings too, but I'm unable to buy quality ones anywhere. I got sent some NTN ones with a kit, but I'm not entirely convinced these are genuine as NTN's product finder doesn't list RMS8N.

One thing I've considered, is buying MJ1 (still quite expensive, all imperial bearings are...), then getting grooves cut in them on a lathe. I've also looked into taper roller bearings too, but couldn't find anything that looked suitable (at least using Timken's bearing finder).

There is a similar availability issue for some mini gearboxes, these also use an MJ1 derivative, but these have a step rather than a snap ring...


1971 Herald 13/60 Saloon - Just about on the road.
1967 Herald 1200 Estate - Rebuild in progress, just about rolls - http://mongoltriumph.com
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glang
November 29, 2017, 11:16am Report to Moderator

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Looking at my three rail non OD box the input shaft bearing cant go forwards because its held in place by the oil seal housing and the output shaft bearing cant go backwards cos its restrained by a snap ring on the shaft which itself is fixed by the tail bearing snap ring.
Would it be possible to fix a non grooved input bearing by drilling and tapping a hole in the casing adjacent to the bearing so that a bolt could be screwed in to trap the edge of the bearing without interfering with the input gear?
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Nick Jones
November 29, 2017, 2:06pm Report to Moderator

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There for location and definitely required.  You could buy plain bearings and have the slots machined later (should be easy enough with a modern tipped part-off tool) though might not end up much cheaper.

The ones we got for the Spit gearbox were very "ordinary" quality - I was almost tempted to re-use the rather weary originals.

Nick


Nick Jones
Somerset UK

Vitesse Mk 1.5 Convertible EFI, Survivor of RBRR 2008, HCR & 10CR 2009, HCR 2010, 10CR2011, HCR 2012, 10CR2013, 10CR2015, HCR 2016 & HCR 2017.
GT6 Mk3 Roto - project in progress
Spitfire MKIV son's project now on the road as a daily driver
2.5 PI Saloon now EFI (PIe?), Engine rebuilt and running sweet.  Diff howling...... Survivor of HCR 2013 & 2014 Gone to live in Swansea

http://www.tengaston.plus.com
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