Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: SwiftDB4 on Saturday,February 01, 2020, 03:04:12 PM
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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?
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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.
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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.
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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
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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?
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As far as I know they are the same except for the larger u-joint and 30mm inner bearing.
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... but let someone with more TC/S experience chime in.
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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.
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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.
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Richard, that looks like a very complete analysis! Thanks!
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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?
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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!
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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.
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:Welcome: 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?
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:Welcome:
Magno_grail ,
Exactly what BDA mentioned. More info Please?
Dakazman
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If the outer bearing is a roller, what takes the side thrust? The inner bearing? If so, what locates the inner bearing?
Has this actually been assembled and run, or still at the idea stage?
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In the stock set-up, side thrusts are routed through the half-shafts to the transaxle.
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In the stock setup, the outer bearing locates the axle in the bearing carrier, and transfers side thrust to the bearing carrier. Note, there is no preload on the bearing, The inner bearing is not fixed in place in the bearing carrier, it would be a remarkably poor design if it were.
The bearing carrier is located laterally by the driveshaft and the lower link, which does most of the work. If the
If the outer bearing is a roller, and the inner is not fixed in place, then there is no lateral location for the axle.
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I agree that the outer bearing shouldn't be a roller but the upright/bearing carrier does not take much at all of the side load. The wheel is bolted to the axle and the axle is directly connected to the chassis through the half shaft and transaxle. The radius arm locates the wheel fore and aft, and takes the brake and drive torque. The lower link keeps the wheel upright.
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I also saw an upgrade axle on a formula ford group on facebook.
Danny J Stanzl is the person that might be selling these.
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I agree that the outer bearing shouldn't be a roller but the upright/bearing carrier does not take much at all of the side load. The wheel is bolted to the axle and the axle is directly connected to the chassis through the half shaft and transaxle. The radius arm locates the wheel fore and aft, and takes the brake and drive torque. The lower link keeps the wheel upright.
So when I'm taking a right-hand corner, and weight transfers to the left rear wheel, the transaxle pushes on the driveshaft which in turn pushes the axle outward in the bearing carrier where the outer bearing stops the axle from leaving the carrier.
You might also consider that the tyre/road interface is where the load ends up, not the centre of the wheel, and think about the compression loads on the top and bottom links.
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I had a lot of wear on the left axle splines. I looked at making new axles but unless the wheel carrier was press fit on the splines it would probably eventually have the same problem. I decided a better arrangement was to make the wheel carrier part of the axle and bolt the yoke on the end. The Lotus arrangement has the outer bearing bottom in the upright bore and the inner bearing is floating. Since the outer bearing take most of the wheel load I wanted to use a roller bearing which meant the inner bearing would take the thrust load. A spacer between the inner bearing and trailing arm clamps the bearing in place. Same as the original, just reversed.
At the same time I was converting the rear brakes to disc so the caliper carrier would double as the seal holder, actually triple duty as it also holds the parking brake drum shoes that work on the inside of the disc hat.
I was able to find the correct size yokes which were weld-on. Holding these on the shaft extension I drilled and tapped them for the through bolt. Having the long bolt from the wheel side to the yoke allows it to be tensioned as opposed to just clamping. There was little room between the yoke and cross for a bolt head anyway.
The dogs on the end of the yoke and shaft were cut on the CNC mill. Easy enough to get a good fit on a CNC.
I drilled the flange for 12mm wheel studs from a Land Rover Freelander. 3/8" studs were too small. Nuts are Ford Probe GT.
I also sleeved the upright between the bearings. The casting hole goes down to the bottom so not much chance of grease staying up in the bearings.
This all assembled but not run yet. I have to finish the fuel injection, LIN buss for all the electrics and paint.
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Elsewhere on this forum I've kidded our own Chuck Nukem about using it to produce new stronger stub axles with his (new) old machining station.
There are, however, suppliers that already make (are can make) improved stub axles:Lotus Supplies - https://www.lotus-supplies.com/parts/suspension/rear-corners/outboard-shaft-assembly-en24-billet-modified-tc/ and Kelvedon - https://kelvedonlotus.co.uk/product/race-drive-shaft-kit/. Knowing even less about British material designations than I remember about US material designations, I tried to figure out which of these two might be better. So far, it appears that the EN-24 that is used on the Lotus Supplies part is stronger than the EN-34 used in the Kelvedon part but I could easily and happily be corrected. The Kelvedon part is heat treated (which is much more than I can say for the stock stub axles) and I expect the Lotus Supplies part is also. Whatever the strength, the Kelvedon part is going to be much stronger than the original part and either part is going to be a huge improvement.
There is a third source for improved rear stub axles, http://dogrings.com/index.html. I was not able to find a picture of his stub axle on his site. This is an acquaintance of of our own Grumblebuns. He (not Grumblebuns) is apparently in decline and I'm not sure if there is a succession plan but it might be worth a phone call.
The last thing of note is that our own andy harwood used VW parts to make a fully CV-jointed half shaft and IIRC he also used VW parts to make a stronger stub axle arrangement. I think he discusses what he did here: http://www.lotuseuropa.org/LotusForum/index.php?topic=2414.msg28915#msg28915. There maybe more info elsewhere or you can buy his project that he's selling (http://www.lotuseuropa.org/LotusForum/index.php?topic=3558.0) which includes all the neat stuff he's put together so far.
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Check this article out. It is quite an interesting read.
https://groups.io/g/LotusEuropa/files/Stress%20analysis%20of%20Europa%20rear%20axle.pdf
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No price on lotus-supplies. Kelvedon lists axle, yoke, nut and spacer separately so is it 495 GBP (axle price) for everything or 920 GBP?
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I have the dog rings set up. It's meant to be a direct substitute for the Imp axle used in various single seaters from the 60s. As supplied there was a lot of additional machine work required. The splines were not cut correctly and I had them remachined locally. I also had to make up spacers for the drums. I am very happy with the end result but I would go with one of the other kits specifically designed for the Europa if I did it again.
Write up and photos here:
http://www.lotuseuropa.org/LotusForum/index.php?topic=3102.msg30873#msg30873
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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.
Very nice work! Is your stub axle/wheel flange one piece? What steel did you use?
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Flange and axle are one piece 4340. It would have been cheaper to make them separate, press together, weld, then finish machine. Looking up available materials, 8620 is cheaper at $288/ft.
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I like the newer design approach magno grail and Serge are showing. If I have worn out parts and have to replace everything those ideas step right past the wear issues i'm reading about.
On the other hand if stock TCS parts look good is it possible to turn the axle shoulder back and put a hard washer behind the bearing race for more shoulder contact area? I'm not at the shop so asking before I look. I read a lot about the nut coming loose. Are there enough threads for an oversize nut with slot and pinch bolt for half the threads?
Luke