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Failure report: Fork on old Schwinn lug frame

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Failure report: Fork on old Schwinn lug frame

Old 09-28-19, 04:50 PM
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Gresp15C
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Failure report: Fork on old Schwinn lug frame



The picture tells the story. Early 80s Schwinn lug frame. I went shopping last weekend, on the way home, heard a "clunk" as I was getting on the bike. No need to explain how I figured out that the fork end had broken clean off. Other side was still together, but cracked in the same way.

The only "analysis" was that it looked like the cracks went right through the corners of the rectangular holes in the fork ends. Those holes were for a secondary retention scheme that Schwinn used on some bikes. I prefer the Brilando clips, but whatever. I'm not an engineer, but I have a hunch that the corners of the holes could be stress risers. Two other old schwinns in the family fleet have those holes, another does not. I've inspected the forks closely for any signs of cracking.

I suspect the crack developed slowly, and I might have noticed it, had I done a more frequent inspection. This bike has been ridden hard for about 20 years, and I don't know how it was used before that. The fork was always a bit crooked. Was it crashed in its former life?

PSA: I think it's worth inspecting old frames for mechanical integrity on a periodic basis. I don't know how often is necessary, maybe some of the experts could advise.

Good news, I had another Schwinn frame hanging in the garage, took about an hour to transfer the parts, new bike day!
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Old 09-28-19, 05:32 PM
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Wow... So a "safety feature" (tabbed washers on the axle nuts) nearly killed you.

Oh, the irony!!!!!

Glad you're OK.
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Old 09-28-19, 06:36 PM
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If you get the break under some magnification you'll see the darker, oxidized area where the crack first started. And, yes, I'll be you're right it was at the sharp corner of that rectangular hole.
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Old 09-28-19, 08:13 PM
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Same thing happened to me back in 1976 on my Fuji Finest, no lawyer tabbed retaining washers yet back then. I had ridden to our big art show/festival and after unlocking the bike noticed the steering was weird, no noises though. I taped the drop out to the blade and limped home. The local; Fuji dealer (primarily a ski shop) refused the warranty as I had bought the bike directly from the rep after he had quit Fuji the year before. I asked them to check with Fuji about the cost of a recall (this is when the CPSC was just starting). I was supplied with a warranty replacement a week later. Andy
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Old 09-29-19, 10:27 PM
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Originally Posted by Gresp15C View Post
I'm not an engineer, but I have a hunch that the corners of the holes could be stress risers.
You don't have to be an engineer to be right about stress risers.

BTW, look up the De Havilland Comet, the world's first jet airliner. Square holes (or windows) in highly stressed areas are a bad idea. Very sad, as the Comet had some cool features. And the plane was made by De Havilland, who also had made (during WWII) the Mosquito which was pretty instrumental in winning the battle of Britain.
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Old 09-29-19, 11:23 PM
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Lawyers tabs - OSHA approved stress concentrators.

My Lambert had even an even more egregious stress starter built into the fork crown, a far worse place. I wondered if that was how the joined the fork and steerer but thought that any sop****re engineering student knew full well that would be suicidal. Well, Lambert did it and it nearly killed me. They also designed that key point to be completely hidden from inspection short of X-raying. (It took 4 years from new to break. Your bike presumably served you and others far better.)

Ben
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Old 09-30-19, 06:17 AM
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Glad you're okay and riding again.

Originally Posted by Gresp15C View Post
The picture tells the story.
Every picture tells a story, don't it?
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Old 09-30-19, 01:31 PM
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Have worked in a bike shop full and part-time since 1982, and have yet to see in person a fork drop out failure. That is scary.
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Old 09-30-19, 05:25 PM
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The very few ft dropout failures I've seen (including mine described above) were rather anti climatic. Much like one axle nut, of a nutted wheel, coming loose. Some weird (till you realize what's going on) flopping about of the wheel, the steering is like a car's when the rack or ball joints are loose. Appling the front brake help stabilize the slop, a pretty natural reaction when things go wrong in general.

Now I don't suggest one "tries this at home" as it's not right and bad stuff isn't always predictable. Just that the ones I've experienced or have had first hand stories about were not the big deal we might initially think.

If we think about the redundancy of our bike's designs most all members (frame tubes, wheels) that directly influence steering and bear weight are connected at two ends/two points. It's things like stems, pedals and steerers failing that make me REALLY worry. Andy
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Old 09-30-19, 06:00 PM
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This failure was certainly of the anticlimactic variety, though I'd prefer to have caught it before it actually broke. The retaining clip doesn't seem like the best possible design. I have one Schwinn with Brilando clips and no rectangular holes, and it works great. Otherwise, lawyer lips work just fine, and wouldn't seem to cause any stress issues if properly designed. I have two other Schwinns with the holes, and I'm not going to freak out, but I will pay more attention to the mechanical integrity of old frames in general.
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Old 09-30-19, 08:14 PM
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Originally Posted by 79pmooney View Post
Lawyers tabs - OSHA approved stress concentrators.
I'm not a particular fan of lawyer tabs, but since they are below the dropout, they aren't on an area that otherwise receives stress.
Unless you're specifically referring to the Schwinn system which seemed to offer a stress riser in this case. (I don't know whether Schwinn's system was in response to lawyer/Nader pressure.)

Since the OP said the fork or dropout seemed misaligned, I would guess that was a partial cause of the crack along with the edge of the square hole. At least, the square hole likely made the fork less durable under condition of misalignment.
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Old 09-30-19, 08:48 PM
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Originally Posted by TallRider View Post
(I don't know whether Schwinn's system was in response to lawyer/Nader pressure.)
The history, as I understand it, is that the bike companies were keeping records of front wheel detachment failures, possibly along with other kinds of bike failures. Some of these failures probably generated lawsuits, or at the very least, warranty claims. I tried to do a bit of digging, and was able to gather that we're talking about maybe 10 to 50 crashes a year -- enough to raise eyebrows but not enough to do any kind of systematic root cause investigation.

The bike makers decided to design their way around the problem. In my view, completely independent of the legal issue, this could have been a straightforward engineering decision. Someone like Frank Brilando might just have been trying to design a better bike. The existence of a working design meant that bike makers could no longer claim that there was no technological solution to the problem. Also, Schwinn could have been engaging in what's called "regulatory capture," where you invent something and then persuade regulators to mandate it.

From what I've read, front wheel detachment failures practically vanished after the introduction of secondary retention. Schwinn made it prohibitive for any other bike maker to license their patented spring clips, so the other makers adopted strategies such as the now-ubiquitous lawyer lips.

Like it or not, litigation is how we police product manufacturers in the US.
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Old 09-30-19, 09:55 PM
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Gresp15C- Yet years later QR skewers (of any detail) were pretty much eliminated from kids bikes. The story I heard was a NJ state lawsuit or law drove this. The drive to protect us from our ignorance continued. Andy
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Old 10-03-19, 12:29 AM
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Do you know if this was a GIANT made (Taiwan) Schwinn? I doubt it was a PANASONIC made Schwinn! Chicago built frames were built to last. Schwinn engineers overbuilt everything. PANASONIC made great bicycles, as did other Japanese makers such as Bridgestone-Kabuki and Fuji. GIANT was always second-rate compared to PANASONIC and the other Japanese marques. That is not to say that GIANT didn't build decent enough, functional bicycles but compared to PANASONIC, it was the same comparison as comparing any sixties/seventies AMF bicycle to any Chicago built SCHWINN.
The factory was in Mississippi after Chicago factory closed around '82. Schwinn had contracted with GIANT of Taiwan to build some bikes. These were acceptable but no where near the quality that the PANASONIC built bicycles.
I am curious about what the exact model of early eighties Schwinn has this lack of engineering excellence. Just a guess that it might be a GIANT product!
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Old 10-03-19, 10:23 AM
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It's a Schwinn World Tourist, maybe 1981 or 1982 (I think the serial and head badge disagree). From what I've read, it was made by Giant.
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