A seriously failed experiment
 

Two weeks ago I built up our tandem's rear hub with some moped bearing cones I found online. M11's just aren't in general circulation any more. We couldn't ride last weekend but today we did. 65.0 miles, home in Waltham to Chelmsford Center and back. Shortly after we started for home we noticed an odd noise coming from the rear. I'm still not sure what it was, perhaps something in the panniers shifting. But we stopped to investigate and I discovered the rear wheel wobbling on the axle. What the '? Did I forget to tighten something in the hub? Naw. Nothing to do but ride home, another 30 miles maybe.

When we got home I grabbed a beer and some tools and pulled the rear hub apart (again). Here's what I found on both sides:

http://world.std.com/~muller/pics/BearingCone.jpg

This is after only 65 miles, but the problem became evident after more like 35. Apparently Olympia doesn't use quite the grade of steel we need. I wonder what a moped would be like with this. It was supposed to be a front axle set.

Our axle was slightly bent, might have been that way for a while. But I doubt that contributed to this problem, not in 35 miles. So I replaced the axle with the one from Olympia and put the original cones back in. I made sure the pit was on top, since that isn't where the load happens. We'll see how well the axle does.

I'm rather bummed this didn't work out. There are other parts suppliers available, perhaps from the same manufacturer. None are expensive so I may try again. Still, I'd rather spend my time doing other stuff. Like mowing the lawn on the second Saturday of every week.

Weeks have two Saturdays now? Whoo-hoo! Wait? do I have to move to Massachusetts?

You definitely need better quality cones. Presuming you also properly adjusted with cone wrenches to find that sweet spot between the wheel not wobbling and the wheel not spinning freely.

Those cones must have been really soft. If you want to keep the Atom hub maybe you could have some custom cones machined and hardened, but it won't be cheap.

Dang Jim! :eek: That is really a shame! You need to send those to someone with a hardness tester to see if they were ever case hardened. I'd also contact the seller for a new set and have them tested as well.

Jim,

That looks like it's going to be so much work that it might be worthwhile modifying the hub to use precision cartridge bearings with a special high strength axle.


verktyg :50:

Chas.

I know you would love to keep your old hub but on a tandem you should seriously consider switching out to a cassette. The wider bearing spacing puts less strain on the axle, cones and bearings.

While modifying the hub to accept a cartridge bearing may help, I think in the long run you may have the same issue again since your not actually changing the dimensions of the axle.


Someone did post a pic a few years ago about they sometimes slide a cartridge bearing in between the axle spacers and the FW to help support the drive side but I forget who.

I'd be sorely tempted to get new wheels and spend less time cutting the grass. . . .

That's a shame Jim. good luck.

Someone like Henry III, a machinist, may be able to help you out.

+1.... I'd guess that those cones missed a step (or two) in the hardening process.

Those are my thoughts also.

I can't tell from the photo how deep the wear is. I got some generic cones that were zinc plated. Now I have been experimenting with polishing the cones before installation, including removing all the zinc. I had some Mongoose races (and maybe cones) that were PAINTED :eek:

My Campy BB spindle had gotten badly pitted. I was in a pinch a few weeks ago, so I decided to try polishing it. It was really hard to cut :P
But, the polishing helped a lot.

Did you keep all of your old parts? Perhaps your old cones can be reground & polished.

Earlier I was thinking it would be nice to find a method to test the hardness of various brands and sources of cones, without taking them on the road and riding for 2000+ miles :P

Thanks for all the suggestions. In fact I did keep all the old parts. Since our axle was slightly bent and may have been that way for a while, I installed the new axle (it remains to be seen how durable it is) with the original cones. I positioned the pitted cone so that the pitted section would be on the top where it doesn't carry the weight of the bike. Maybe we'll get a more thousands of miles out of it; it already has 6000 from us and at least 3000 from the original owners.

As for how deep the wear is, compare the curvature of the race on each side. That entire dark area on the right is a slot worn away. This happened in only 65 miles. I had already been in conversation with Henry III about solutions and I do have a few more options. Since the spacing is 135mm the best ultimate solution is a new Shimano hub with disk or drum brake. Of course my sweetie wants me to keep the bike running for a 100 years.

@jimmuller,

We sold some Gitane tandems BITD. Usually kept one on display at least until 1975 or 76 when we started importing Bertins.

I can't recall having a lot of problems with the bearings on the Atom drum brakes but I remember a rear wheel sitting around for ages waiting for parts???

Headset yes! We snagged everyone we could find. Those 1 1/8" Metric threaded headsets were pretty scarce (don't know if they were 32mm but they were always referred to as 1 1/8"). Stronglight made a better quality one than the standard Gitane headset that came on their tandems.

Maybe our local tandem riders didn't put that many miles on them?


The standard Normandy/Atom cones were very low quality. We got them in bags of 50 from France - they cost us less than $0.50 apiece. We inspected every bag and threw out ~10 cones out of 50 because they were damaged in the ball track surface.

Those cones were case hardened. They were machined on automatic lathes or screw machines, tumble polished and then put in a heat treating furnace and heated to red hot in a high carbon containing atmosphere. Over time the carbon is absorbed into the steel. The red hot parts are dumped into water to quickly quench them and create the 60 Rc case hardened zone.

This picture show the depth of the case hardened area which can be from .005" to .050" deep (0.127mm to 1.27mm).

http://bikeforums.net/attachment.php...hmentid=461287

The dark areas in these parts are the 60 Rc case hardened zones.

Precision case hardening creates parts that are 60 Rc hard on the surface but the core metal remains softer and tougher to resist cracking and breaking.

Cheap case hardening like on the standard Normandy/Atom cones (and also cheap headsets, BB spindles and cups etc.) is inconsistent and the hardened depth varies from part to part and even in different areas of the part.

The ball tracks on cheap case hardened bearing are rarely ground or polished. They're used as they came out of the heat treating furnace (cheap case hardened headsets are tumble polished then chrome plated so the plating covers the ball tracks and quickly chips off in use adding to the premature wear on those parts).

The moped cones were probably poorly case hardened!

As @Bianchigirll suggested you may be better off in the long run going to a modern rear hub with outboard bearings. :thumb:

verktyg :50:

Chas.

Does the taper of the new cones match that of the original cones? "Close" is usually not good enough.

I would thought they were identical from visual inspection. The ball tracks were certainly correct.

I got an email reply from Benji at treatland.tv today and he is sending me two cones of a different manufacturer. These are the ones that a reviewer on his site described as having poor machining but I'll reserve judgment until I receive them. It was nice of him to reply so promptly.

The story continues...

Replacing the cones is more interesting. Replacing the hub with a cassette hub seems more practical.

Have you looked into further case hardening the cones yourself? It's cheap and easy to do if you have an OA torch and a wire wheel/dremel to polish the parts after hardening. A MAPP gas torch might work too. If you overdo it, worse case they fracture on you and your hub starts feeling gritty. Compound can be found at numerous places such as here: http://www.brownells.com/gunsmith-to...prod27119.aspx

@jason_h,

That kind of case hardening has been around for a long time. It' a blacksmith's art most commonly used for knives, swords and guns.

Several problems, it's hard to get a uniform case hardness depth, secondly it's more applicable to surface hardening such as on gun parts than for highly stressed wear applications like bearings.

Commercial case hardening is done in time and temperature controlled furnaces with close control over the carbon bearing atmosphere.

verktyg :50:

Chas.

Indeed. The challenge is fun; heck, it's a C&V project after all.

But also I know nothing about modern hubs other than that 135mm hubs exist. I may have to give up the hub brake because I don't know how a disk caliper would attach to the frame and I don't know if drum brakes exist any more. Online searches produce mostly S-A IGH hubs with internal brake.

Since it isn't a crisis situation I'm taking the interesting route.

Jim,

Shimano and SRAM make hubs which accept a drum-like roller brake.

SRAM calls theirs an I-brake. I believe it can be mounted to this 135mm SRAM DualDrive hub. Such a hub would give you the added benefit of a 3 speed IGH along with your triple front crankset. You could use a 7, 8 or 9 speed cassette in the rear, or I could try to build you a custom 6 speed version.

I looked again and finding a 135mm spaced Shimano hub which accepts the Roller Brake doesn't look possible.

Hey @jimmuller, I have a hub for you. It's a cassette hub with drum brake. I don't think I'll ever need it. You can put a 7- or 8-speed cassette on it. It was supposed to fit a 9-speed on it, but the last cog stuck out too much. It has a solid axle with nuts. I'll measure the OLD. I suspect it's 130.

It's about 127mm OLD. The hub flange diameter across the spoke holes is about 74mm. Made by Shimano, barely used (by me). Interested?

That's a kind offer, Tom. Thank you. Our frame is 135 but I suppose I could find a longer axle and add some spacers. That would let me play with how much dish the wheel has too. Hmm. If you think it would hold the weight of a tandem, then yes. Though I'm still chasing options this sounds like the best long term solution!

It's a solid axle, not QR. I think it's long enough to accept spacers. Maybe.