Thursday, July 22, 2010

Birth of a rim

Ever wondered how aluminum rims are made? No? Too bad! Here's how it happens, with diagrams from the 1996 Mavic Rim catalog.

Step 1! Procure aluminum extrusion based on your rim profile. These come as straight sections, extruded via a die in to the desired shape.

Step 2! Coil the extrusions in to a continuous, spring-shaped loop of the right size. A straight line is then cut across the coil.

Step 3! Join the two ends together, forming a hoop. Some rims have an aluminum or plastic insert here to hold the shape. At this point, some rims are also welded.

Step 4! Drilling the rim. This is done using a re-targetable, computer controlled drilling system.

Here's the drilling system Mavic was employing in the 1996 time frame. I doubt much, if anything, has changed.

Step 5! Anodize. At least, this is where you anodize if the rim is. This is where another manufacturer's rim is painting or powdercoated. Machining of a brake track is probably also done here.

Step 6! Eyeletting! Again, if your rim has eyelets. No eyelets, no eyletting. At this point, any finishing touches are applied, like decals, inspection is performed (hopefully) and the rim is wrapped and ready to head out.

Carbon rims are obviously an entirely different process. I have some memory of a video that documented how they were made. Anyone have a link?

Wednesday, July 21, 2010

Practice makes perfe...pass the Doritos

Back in 2002, back in the dark ages before the waiting lists and hundreds of people clamoring to get in, I went to UBI to try my hand at frame building. Schedule-wise, the class that worked best for me was the steel TIG class. It was a ton of fun, and I learned a lot, but the learning curve on TIG was pretty steep for me - I've often described it as 2 weeks of self-administered shock therapy. It's not easy!

As you might guess, training people to do production welding takes some time, and teaching them to do it in titanium takes even more! Steel is pretty forgiving, but titanium is far, far less tolerant. So naturally, a largish titanium frame production line is going to have their people practice. Apparently, someone at a large Ti frame producer thought this..."air filter" made a perfect project.

As a practice project, it's got it all - mitered joints, tight radius welds, and milled-down tubing. It's owner tells me it has one fatal flaw as an "air filter" - you can't put it down without it tipping over, due to where the holding ring is welded. Bike frame design has been thoroughly refined over the last 100+ years, but every once in a while, someone tries something new that ends up not working as well as the classic triangle frame. Guess the same thing applies to the "air filter".

Any guesses as to what frame manufacturer this came from?

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