Stub Axle wear

[Roger]

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?

[jbcollier]

In the stock set-up, side thrusts are routed through the half-shafts to the transaxle.

[Roger]

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.

[jbcollier]

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.

[Serge]

I also saw an upgrade axle on a formula ford group on facebook.

Danny J Stanzl is the person that might be selling these.

[Roger]

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.

[magno_grail]

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.

[BDA]

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.

[Chuck Nukem]

Check this article out. It is quite an interesting read.

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

[magno_grail]

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?

[jbcollier]

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

[andy harwood]

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?

[magno_grail]

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.

[edgefinder]

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