Stub Axle wear

[SwiftDB4]

Any suggestions on combating wear of the stub axle at the outer bearing journal? As shown on the photo I've had 2 axles wear at this point. The inside of the bearing showed some signs of fretting. Admittedly the axles have at least 25000 miles and some with racing slicks on track days. Also both hub carriers had wear of the aluminum at the inner bearing outer diameter. Until recently we kind of had to treat the housing wear with loctite as a band aid. Not really suitable, but new hub carriers are a permanent solution now. The axle design has some real flaws especially that part of the bearing journal is in the splines. Why Lotus never changed this from the Imp design is beyond me. I've always green loctited the splines and threads and the spacers were not distorted or crushed.
I replaced the axles in Meissel sleeved housings recently. I used grease on the journals in assembly, but wonder if loctite would have been a better choice?
As far as axle improvements has anyone machined the axle to fit a wider inner bearing (19 mm vs 13 mm)? Is it safe to remove about .200" from the axle hub to accommodate the wider bearing?
Finally are one piece axle/flange replacements available for S2's? Banks and Kelvedon sell TC ones, but how about S2?

[jbcollier]

If you are going to run slicks, upgrade your axles to either the Corvair option or the new ones sold by Kelvedon.  Both will require going to the TC sized u-joints, shafts and output yokes.

The stock axles are so much crap.  Careful, meticulous assembly can make them "ok" for road use.  For the track with slicks?  Nope.  Or you can fit new axles ever season or so.  Less with heavy tracking.  Perhaps more with less.

[SwiftDB4]

Track days and slicks are not in the Europa's future. At 70 years old I'd just like to have things last another 10 years or 20,000 miles on the street.

[surfguitar58]

Crap axles aside, it looks like the wear from the outer bearing is outside of where the machined diameter is, like the inner race was over the beginning of the spline cuts. Are you sure your bearings were fully seated in the housing or the correct spacer was used?
Tom

[SwiftDB4]

On all the S2 axles I've used the outer bearing rides partly on splines. Spacer lengths all measure the same and are 31mm i.d., not 30mm. No appearance that everything isn't seated fully. Are TC axle splines different so that the bearing isn't partly over them? JB?

[jbcollier]

As far as I know they are the same except for the larger u-joint and 30mm inner bearing.

[jbcollier]

... but let someone with more TC/S experience chime in.

[BDA]

Sorry, I don't have long term experience but I have a couple of points that may be helpful.

First, and the least significant because I have the least hard information on it, is that I had heard or read that design changes between the S2 and the TC improved bearing life. That might suggest some carry over to stub axle life. I believe that one change was beefier bearings. Interestingly enough, the S2 and TC share the same bearing spacer length, and it's the longer (at 2 1/8") where the TCS takes a 2" spacer. The Specials inner bearings is wider by approx 1/8". Of course, that also implies that S2 and TC (non-special) may not be that different and therefore it is only the TCS which might enjoy better bearing life. Some good information on rear bearings and spacers can be found here: http://www.syer.net/rearbearingtech.htm

Second, and a bit more significant because it relies on actual experience, comes from the Jensen Motors Competition Manual. About the rear axles they write:

The rear stub axles were installed using "Loctite Shaft and Bearing Mount" on the threads.
The locking nut was torqued to 160 lbs ft. The hubs should be checked for tightness after every
track session as problems have been experienced with stretching and consequent slackening of
the axle shaft nut. It is recommended that the stub axles be replaced after three practice and race
sessions as a precautionary measure.

There are a few things to note. First is that they ran wheels that were 7" wide with slicks. Also, they don't explicitly say so, but they appear to have run a TC as opposed to a TCS. The reason is that the 365 was not allowed for the season they ran (1972 - 1973) and I think that implies that the TCS was not legal which means that the smaller inner rear bearings (for the TC) were used.  (My quick reading of the manual and my memory of how the rules worked in that period suggests that to me.)

As for stub axles, I would suggest that if your are expecting a steady diet of auto crossing or track days - especially if you run slicks - you should definitely opt for an alternate stub axle arrangement. JB already mentioned Kelvedon as a source. Richard (Europa Engineering) has a similar kit which I would recommend. There are also plans for modifying Corvair or BMW stub axles here (http://lotus-europa.com/manuals/). David Anderson describes a solution he came up with here (https://www.prevanders.net/europa/rearaxle.html). If memory serves, our own Andy Harwood had a VW based replacement (http://www.lotuseuropa.org/LotusForum/index.php?topic=2414.msg28915#msg28915). Like rear disc conversions, there are many ways to skin that cat.

Hopefully that helps and that if I missed something or get something wrong, I will be corrected.

[Richard H]

Back in 2017 I had time on my hands and did a thorough load and stress analysis of the stub axle and bearings.  It's contained in this file on the new LotusEuropa site..

https://groups.io/g/LotusEuropa/files/Stress%20analysis%20of%20Europa%20rear%20axle.pdf

Any questions I'll try and answer.  Probably the best that can be achieved from the standard parts.

[BDA]

Richard, that looks like a very complete analysis! Thanks!

[SwiftDB4]

Thanks for the report from 2017 Richard. I would agree with you on all points and had not considered the wider contact of a 30mm inner bearing would help to maintain clamping forces. What does bother me about the Lotus design is that the outer bearing rides partly on splines. Maybe this was original Imp axle, but couldn't Lotus have shortened the splines to give the outer bearing a full journal?

[Roger]

As I remember from rebuilding my TC's axles, the hub spacer fits over the inner ends of the splines, not the bearing inner race.
I remember the build particularly because the hub spacers supplied were undersize, and would fit over the splines but not the full diameter of the axle and were therefore not in contact with the inner race of the bearing. I had them turned out to fit.
When I looked at the old ones I had removed I found they were the same. No wonder the axle slid in and out!

[magno_grail]

Not familiar with differences between S2 and TCS. What internal bearing tolerance are you using, CN, C3? Perhaps you are not getting enough preload on the bearing.
If the carrier is not a press fit on the splines it will walk the inner race on the shaft. Also, at least on my TCS, the spacer is not hardened which allows it to flex more than it should.
My work around for the spline problem was to make the wheel carrier part of the axle with the U-joint bolt-on. Also changed the outer bearing to a roller since it takes a majority of the load.

[BDA]

  magno_grai!!

That's a nice setup. Can you tell us more about it? I assume the half shaft is hardened. Is there a possibility that others can purchase a set of those?

[dakazman]

 
Magno_grail ,
   Exactly what BDA mentioned. More info Please?
Dakazman