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Archive for February, 2010

Bike SnobNYC said it best:

“Because nothing can be toxic as long as bicycles are involved somehow.”

There seems to be this pervasive notion that because it has to do with bicycles, its good for the earth. We saw it in Bicycling Magazines letter from the editor, and we see it in the video Junkun BSNYC shared with us. I also discuss this topic with bike riding folks on a regular basis. Its nothing new, in 1994 Bridgestone had an article about it in their catalog. For some reason, some folks tend to think bicycles are inherently good for the earth. Its clear that if all you do is strap it on the roof of your car for getaway weekend rides, its actually worse for the earth than if you didn’t buy a bike in the first place. The only time it’s good for the earth is if you use it instead of your car until you’ve offset the environmental impact from the bicycles creation and ending. This notion gave the bike companies an opportunity to delay jumping on the eco-friendly bandwagon, because their products were inherently “green” just by being what they are. Something tells me the big boys like that rumor and tend to spread it. In the first few seconds of the video I’m about to share with you, a Trek representative slips in a “…bike riding itself …” when talking about Treks new Eco Bikes. It doesn’t really make sense except of course in a subliminal way. Listen carefully, its crammed in there.

Trek is stepping up to the plate with a line of Eco Bikes. The fella admits at the end of the first video that this is “just a beginning” in Trek’s commitment to saving the earth. Lets take a closer look at what they are doing. I encourage you to watch the videos on the website. The fella in a black shirt and jeans gives a good introduction.

(EDIT: I can’t get any of the direct links to the videos to work. Sorry Folks, watch them all Eco Bike)

EcoBike Intro

Trek Belleville

Trek Atwood

They’ve added two steel bikes to their lineup, made in China, that have recyclable plastic in the saddle and grips, and recycled material in tires. One is the Belleville, and the other is the Atwood. I can’t be too hard on them, because I really do believe they are making an effort, although most of the effort seems to be put into the marketing.

The man in the black shirt goes on to tell us about the method they used in designing these bikes. They used “basic principles” from “Eco-Design” which uses the OKALA method to score the design based on the products lifecycle. He does not, however, tell us the score OKALA gave to Trek for these here machines. He goes on to tell us that OKALA uses the birth, life, and death of the product to grade the eco-friendliness.

During the segment on birth, the presenter talks about how steel is the best choice for an Eco Bike and reminds us of the great riding characteristics steel has.  So, if Trek is truly committed to helping the earth, and this is a new venture for them, I suggest they replace their carbon fiber and aluminum with all glorious steel! I’m not holding my breath. They also take advantage of “close sourcing” for the components. So instead of buying all the components from somewhere in Asia, boxing them up and have them shipped to a factory somewhere somewhere in Asia to make bikes, they are…….wait a second! Nothing changed here. The guys in the finance department figured out close sourcing a long time ago. Less shipping means more profit.

The paint is powder-coat instead of regular bicycle frame paint and they don’t use chrome plating. Less waste, less toxins, longer life. I like it Trek! Moving forward in your endeavor, you can do this with all your bikes!

In the life segment, all the black shirted man says is that the bikes are useful for a really long time. This is great. So all this time Trek has been building bikes that are not useful, and don’t last that long. I believe Trek should be striving for these characteristics in all their products, and not just the “green” products. I noticed in this segment he didn’t mention that the Shimano components will last forever and never need to be replaced. Maybe that’s because its not true. In the future, Trek could start a platform initiative to change the planned obsolescence practices of Shimano. They could team up with Specialized and demand that parts have a life span more than a few seasons and be made of something other than plastic. Now THAT would be something to make a video about!

The end segment really gets me exited. They designed the bikes so they can be taken apart. Well, until this very moment, I thought most bikes could be completely dis-assembled with nothing more than a couple wrenches, some cable cutters, and a bit of alcohol for the grips. Boy was I wrong, and apparently hallucinating during my experiences of taking bikes apart.

This is a good sign though. The green movement is mainstream enough for Trek to get on board. Its only a matter of time before Specialized has a competing line. Then, they will compete to see who can make the most sustainable bicycle ever. Will they still have a new model every year?

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Part of being a sustainable bicycle component is having a long life span, or at least having a long life span worked into the design. Failure analysis is an important aspect of the design process in order to gain long life span. For parts or components that undergo load, a good design process usually involves failure analysis after the testing phase. A lot of this happens in the bicycle industry. Many bicycle and component manufactures have an entire branch of their company that tests their product to a point of failure, learns from that failure, and works that knowledge into the continued design. If the company does not have a testing department, they contract the testing out to a third party such as EFBe. Another important reason that frames and components are tested is to make sure they meet certain safety standards, or performance standards. This kind of testing usually doesn’t lead to failure.

Cycling is a good place to find failures after the product has hit the shelves. The reason for this is that the weight of the final product is an important design parameter. So important that vast amounts of research go into removing mere grams off of components. Jobst Brandt said it well: “Parts which give reliable service are often considered “overbuilt” and are redesigned to save a few grams.” Unfortunately other design parameters are sacrificed to obtain desired weight. These can include ultimate strength, fatigue strength, and lifespan. Visit Jobst’s article Some Bike Failures to see more photos of failures and some more discussion as to the reason why bike parts fail.

Failures are seen on just about every part of a bicycle,  but one of the most common failures that I see on a regular basis as a mechanic is pitting of bearing races such as this one:

Pitting on a axle cone

This pitting can happen when abrasives contaminate the grease surrounding the ball bearing and race. Put simply, a ball bearing is sandwiched in between two smooth surfaces that are parallel to each other. These surfaces are called “races”. Since it is almost impossible to get the two races perfectly parallel, the ball bearing is always a little bit closer to the races at a single point in its rotation around the surfaces. The space between the ball and race is filled with grease, so when this grease is contaminated with abrasives, the abrasives get compressed against the race and the ball at the point in the rotation where the ball is closest to the race. When this squeeze happens under load, with thousands, upon thousands of rotations, it causes the pitting you see in the picture. This is a common failure and is the result of poor maintenance and poor bearing adjustment. With proper maintenance and adjustment, bearing systems of this type will last longer than their modern brethren.

Modern bearing systems are usually sealed. This means that the two races and ball bearings come in a neat adjustment-free package that just needs to be pressed and seated into a recess, like this:

You can see two metal rings. These are the races. The balls are under that blue piece of plastic. When these types of bearings get contaminated and go bad, you remove them, throw them in the recycle bin, and put in new ones. To maximize their life span they must be installed correctly (parallel and seated), and carefully wiped clean every now and then. You want to be careful as to not push contaminants beyond the plastic seal.

Once in awhile I’m blessed with an uncommon failure. Recently I was working on a Masi Gran Criterium that was upgraded in 1985 to full Campagnolo Super Record components. The rear derailer (1984 Super Record) had a small crack in its outer cage:

Cracked SR outer cage

This is a strange spot for a crack failure since this part of a bike is under minimal load. Since the crack lies at the back of the cage, then the maximum load scenario would be when the chain is in the big-big combo. This would place the tension spring at its maximum potential to compensate for the lack of slack in the chain. In other words, the derailer would look like this:

Big-Big Combo - Tension spring at maximum

When the derailer is in this position, the tension spring is counteracting the chain by trying to pull the tension pulley back to its neutral position. This puts tension on the back surface of the pulley cages. If you have trouble visualizing this, imagine the bottom surface of a beam under load. This surface is in tension while the top surface is in compression. In this scenario the back of the cage is in tension and the front of the cage is in compression.

Now, I don’t think that this is the only factor that caused the failure. In the picture of the cracked cage, you see a nut recessed into the cage where the spring cage bolt screws into. When the bolt is tight up againast that nut then there is a portion of the cage that gets compressed. The cage material is a very lightweight aluminum alloy, and when compressed with a recessed nut that has 90 degree angles for edges it will develop microscopic cracks. Points like this are called stress risers. To get a better look, I pulled the cage apart at the crack:

Notice the nut seat has a 90deg angle at the compression point.

The thin part of metal that is below the nut seat in the above picture is compressed when the derailer is in use. The angle between this section of material and the non-compressed material is around 90 degrees. At the vertex of that angle, the compressed material is being pulled away from the non-compressed material forming a high stress point which, over time, will develop microscopic cracks, especially in lightweight aluminum alloy.

Add one more factor to the mix, and it all becomes clear. Material flaw. There is a good chance that this part may have had a flaw on its back outersurface, such as impurity or void. I didn’t see any evidence of one, but I don’t have a scanning electron microscope at my disposal, so I may never know. It is, however, likely.

Design flaw, material flaw, and one too many times in the big-big combo sent this derailer cage to the graveyard. The problem is I don’t know the history of the bike, the rider, or when the crack developed (my customer just bought the bike), so I don’t know if it had a long life or not. I do know one thing. The bike it was on did not get ridden all that much. This crack may have developed in 1985 for all we know.

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