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Broken Hammered Aluminum Fender

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Broken Hammered Aluminum Fender

Old 07-06-19, 06:31 PM
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Broken Hammered Aluminum Fender

This is not a knock against the folks who make these Honjo lookalikes. I just thought the multitude might be interested in the way this rear fender cracked after maybe a year of use. I tried to follow the rule to be sure there is no bending stress "baked in" when tightening the mounting hardware, especially at the point where the fender attaches to the brake bridge, and I did use a leather washer between fender and bridge. I think I might have cheated just a little bit in trying to fine-tune the curve of the fender to follow the tire -- shouldn't have. Also, I used a wider than normal machine screw here, reasoning that spreading out the clamping stress of the screw head would reduce the tendency to break...and because my hole was a tiny bit larger than it should have been by the time I got it lined up exactly. But the flat underside of the wider screw head likely couldn't follow the concavity of the inside of the fender and its edge applied stress to the material of the fender, right on either side of the screw hole. Shouldn't have done that, either.

So it cracked. I like how the crack followed the lines of the hammered honey-comb pattern, propagating through the little polygons. (Murphy's Law, "The paper is always strongest at the perforations," didn't apply here. ) A bit of a bummer because they weren't cheap. But they are light and looked great. I think I'd go steel next time, as this is a classic aluminum fatigue failure. Also, I prefer a breakaway mounting on the front. I fashioned one but it rattles. (I took a header in the dark years ago when something jammed in the front fender. I didn't know what was happening until the world fell on top of my head. I don't know why I didn't break my neck.)

The original screw hole was exactly on the line that joins the two rolled edges, right between the inward-pointing vertices of the last two octagons. The two round holes in the photo are where I tried riveting a splice across the break. It worked, sort of, but it rattled and I decided it just wasn't good enough. The two fragments will fit nicely on our tandem, where the tire clearance requires a fender to be cut in two anyway.
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Old 07-07-19, 04:07 PM
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...and here's the finished re-purposing. Now any bending from bouncing over road roughness will occur in the steel rack bracket that joins the fender to the brake bridge, and not in the fender. The front fragment, immediately behind the stoker's seat tube, is mounted deliberatedly, if unattractively, "high" so I can stick an Allen wrench in to get at the cap screw that holds it on to the "Sheldon" brake nut. One of these days I'll get around to finishing the edges of the doubled bit but it held up well on our 80-km test ride today.

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Old 07-07-19, 04:55 PM
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Stress risers gonna crack. There's proof of that.

Good job on the rework; should be enough hardware there to hold it in place from breaking yet again in the center.

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Old 07-08-19, 04:47 PM
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Aluminum + stress riser + vibration + time = crack
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Old 07-09-19, 09:41 AM
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I like that the repair makes that s&s machine pack down a bit easier too now! Who made that fat-tubed beast of a tandem?
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Old 07-09-19, 10:09 AM
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Great job! I'll bear this in mind should my fender of the same design ever fail.
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Old 07-09-19, 11:09 AM
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It's possible the manufacturer or distributor would replace it. I had a plastic "Planet Bike" fender break, took it to the LBS, they gave the shards to the distributor, and a week later I had a new fender, gratis. I didn't even have my receipt for the fender!
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Old 07-09-19, 06:54 PM
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Originally Posted by scarlson View Post
I like that the repair makes that s&s machine pack down a bit easier too now! Who made that fat-tubed beast of a tandem?

The tandem was built in 2007 by Kent Ericksen in Colorado to a design worked out for us by Glenn Erickson (no relation) of Seattle. Glenn is/was (it's a little unclear in my mind) the "E" in R&E Cycles, and remains illustrious in so many other ways as well. That's his signature on the top tube just behind the S&S coupling. Of all the "things" we've ever bought together, this bike has given us the most happiness.

The fender was originally installed intact, in the normal way, on a Jeunet (single) touring bike that has ample clearance for fenders and gravel-grinder tires. But when it broke, I thought, ah, here is the opportunity to use it on the tandem, which has always required fenders to be cut in two anyway. We spec'd the bike for rim brakes. On a tandem you want the arms to be as short as possible, so the free lunch we gave up was straightforward fender installation. The frame has the mount for a rear disc brake and when we used to to tour in Europe, we would change to a front disc brake fork, too. But for all the riding we do around here, rim brakes work just fine, look nicer, and allow a C&V steel fork.

For disassembly it is, as you note, convenient to have easy-on, easy-off fenders that pack smaller into the cases. (The front fragment stays where it is.) It's even practical, on a supported tour, to leave both fenders in the SAG van on sunny days and just put them on in the morning if it looks like rain -- takes like 2 minutes if you don't lose a wingnut in the grass. This aluminum fender is so light, I think I'll just leave it on more or less permanently. Even though Erickson tandems are long, we are short and it will still fit sideways on a trunk rack with both wheels off. Being able to pop the rear fender off quickly is very handy.

Good point from JohnDThompson about seeking replacement. It would not surprise me if this shop or this supplier would have replaced it on a goodwill basis. I do know that at least one supplier doesn't warrant aluminum fenders against breakage and I think I made a couple of first-timer-with-aluminum mistakes in mounting them, so I don't feel entitled to a new fender. (That's what goodwill is, isn't it: being given something that makes you happy that you didn't feel entitled to.) But, hey, I'm happy as it is. Tandems can do that for you.
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