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Sturmey Archer XL-FDD brake problems

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Sturmey Archer XL-FDD brake problems

Old 04-20-19, 11:32 PM
  #1  
scarlson
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Sturmey Archer XL-FDD brake problems

I don't know if this is the right subforum to post this in, but I figure I'll give it a shot here because commuters probably have the most experience with these hubs.

I built a Sturmey Archer XL-FDD hub into a bulletproof 700c front wheel with Rigida Sputnik rim and Sapim Strong spokes, thinking it would be the ideal wheel to commute on. The drum has kind of never worked very well as a primary brake, so mostly it has sat around while I ride other dynamo wheels with cantilevers. Now it is time I try to fix it or else get rid of it. So the thing is 7 years old but has very little mileage on it - maybe 1500 miles tops - albeit in some bad weather and down some steep hills, but not to the point of brake fade, just to the point where you could see steam rising off the hub in cold weather. It really did work poorly/not at all before it got warmed up on those -10F Vermont mornings when cars wouldn't even start. Road spray would also run down the fork blade, down the reaction arm, and (presumably) into the drum, making it worse in the wet than a pair of cantis because braking doesn't make the water go away immediately.

Lately when I use it, it brakes very unevenly. Like it will make the fork judder in time with the wheel rotation - as if the drum is out-of-round or partially glazed or cracked or something, so it catches and then releases, "thump, thump, thump". I hate using it. I examined the drum and saw nothing wrong, just a little surface rust. I tried lightly sanding the rust from the inside of the drum. This didn't help at all. I would assume any rust would get worn off of the inside of the drum by the brake pads. I have motorcycles with drum brakes, and this never happens to them. I wonder if any of you have experienced this, and what you think I could do to correct it. I have googled my heart out and found nearly nothing.

Some thoughts:
Could it be uneven spoke tension pulling the thing out of round? I think I can build wheels ok, but this was one of my first.
Could it be that I've overworked the thing in cold weather and messed it up somehow?
Are they known to be susceptible to rusting?
I have heard about the need to "break-in" these drum brakes. Did my disuse cause it? Is it still not broken-in?

I can try to resurface the drum, but it will be hard. Even the American Pacemaker lathe at work does not have enough space to swing such a large diameter wheel. I suppose I could try setting something up with the milling machine to turn the wheel on its axle while lightly milling the drum, or just unbuilding the wheel, resurfacing the drum, and rebuilding it again. But I really don't want to do that.

Any input you have would be amazing. Thank you.
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Old 04-21-19, 07:09 AM
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Moe Zhoost
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I have an X-FDD on my commuting bike and have had none of the issues you describe, even after ~20,000 miles of all weather commuting. Winter temps in NC are a bit warmer; however on those occasional dips into the teens, the brake only needed a bit of use to warm up sufficiently. That said, I have no idea what's going wrong with your hub but I can offer a bit of brainstorming:

1) I really doubt that you can pull the drum out of round with spoke tension. It may be that your spoke tension is not sufficient so that they are not transferring the braking force to the rim uniformly.
2) I also doubt that the drum needs to be machined. This just a gut feeling from the lack of internet postings pinpoint out-of-roundness of the drum. Should be easy to check with a dial indicator.
3) Headset ok? Probably since you have no problem with other wheels. You may want to check anyway.
4) Have you checked that your reaction arm is secure? Mine got a bit loose one time and I heard a thunk every time I applied the brake. No pulsing though. I wonder if it's possible that braking creates some torsion on your fork blades due to misalignment of the torque arm causing a resonance that you feel as pulsing.
5) I've not had any problems with water getting into the drum with the exception of internal condensation that developed when I went from my cold garage into a warmer humid environment. One application of the brake took care of that. Also - no issues with rust, although I imagine that some light rust could form. Braking should take care of that as well.
6) You've checked for oil or grease contaminated shoes?
7) Does the wheel behave the same when mounted on a different bike?

That's all I got for now. Good luck tracking it down.
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Old 04-21-19, 10:46 PM
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Thanks for the reply.

Punch list, here goes:
1) I always build wheels too tight. A good bit tighter than machine-built wheels on lower-line bikes anyway. Runs in the family.
2) I don't know why I didn't think of a dial indicator. For all the machining I do, yeah, I just completely forgot about that. So I set the thing up in the mill with the thou dial indicator this evening. With the fat tire it just barely fit! I am lucky I did not use the tenths indicator. I would have broken it!! Out-of-round does not begin to describe this thing. I found three "lumps", roughly corresponding to the three or so judders per revolution that I get while braking. The biggest one was forty thou proud of the rest of the drum surface. And surface rust in the drum indicates that these three lumps were getting most of the action, as far as braking goes.
3) Headset feels fine, and I usually notice these things.
4) Reaction arm has no play that I can feel.
6) The shoes are glazed funny. I don't know if it's oil or grease or just moisture but they have a weird crÍpe-y sorta film on them. Maybe from disuse? I could lightly sand them.
7) It's worst on my tandem (where it's relegated to now, least-ridden bike) and was best on an old mongrel Stumpjumper that I put 700c wheels on used as a winter beater years ago. This probably correlates with its age and my age and thus how crabby I am about it. So probably no significant difference between bikes. Or maybe it got worse over time.

I think I got a dud. The lumps inside the drum almost look glazed. And it's not like an oval shaped out-of-round. It's seriously three little lumps. I bought this thing years ago so I'm probably out of any kind of warranty. I may try to mill it if I can get it held down securely somehow. I will ask one of my friends who machines more things than I do. Worst case, I guess I can un-build and rebuild the wheel. That really was not what I expected. Thanks for prodding me to take a measurement!
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Old 04-24-19, 05:46 AM
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Glad you figured it out. Three humps is crazy and certainly indicates a manufacturing issue. I've had good luck with Sunrace customer service, so even if your hub is out of warranty you should send them an email. Contact info is below. The person I dealt with was David Prosser.

Good luck.


Info@sunraceusa.comSunrace Sturmey-Archer952 School Street #409 , Napa CA. 94559 USAwww.sunrace.com www.sturmey-archer.comTel: +1 (707)259-6700 E-mail: david@sunraceusa.com
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Old 04-24-19, 09:35 AM
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Thanks for the info!

Before talking with my oldtimer colleagues about how they would skim brake drums, I looked around for how to skim brake drums built into wheels and came upon
of a kindly old British chap doing motorcycle drums in the mill, by holding a lathe tool in the spindle of the mill, with the power off, feeding the quill, and spinning the wheel by hand. I showed this video to one of my colleagues and he gave me the go-ahead to use the clapped-out Bridgeport in the middle of the night for this project. So here I write, bleary-eyed, about my experience.

I ended up taking a similar approach to that in the video, with a few notable changes.

The axle was mounted in a 5C collet, tightened in a 5C collet block, in the vise of the clapped-out Bridgeport mill along with a bunch of spacers to keep it within Y-axis travel limits. There was barely enough space for the wheel with the tire deflated. I put a brazed carbide boring bar in the chuck of the mill and engaged the low gear range so that the spindle wouldn't turn when I put load on the tool. I locked the quill in place and moved the table up and down to feed the tool while I was manually spinning the wheel. The axle flex combined with lash in the mill's geartrain meant that I had a huge problem with chatter. Low speeds and aggressive feeds were the name of the game. Putting a thumb between the mill spindle and the wheel axle sorta dampened things out. Because of the chatter, the surface finish was pretty bad so I cleaned up with some 100-grit emery paper.

I got it to within 2 thou, using the tenths indicator. I guess now I really have voided the warranty! I'll see how it rides soon!!

Here are some pics.





Upon looking harder I think the American Pacemaker lathe could have fit this wheel, but I don't think it would have been a good plan. It has a three-jaw universal chuck on it, and it ought to have a four-jaw independent for a job like this where concentricity is paramount, so I'd have to change chucks and they weigh 400 pounds. I'd also have to bore between centers, so setting up all the tooling would take me two hours, for two minutes of machining. With the mill, the equation was reversed: two minutes setup and two hours of machining.

Last edited by scarlson; 04-24-19 at 09:39 AM.
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