Part 7: Build – Tube Prep

April 1, 2007

The build section of this report will be a day by day update. I can’t really comment on the fabrication process, so I’ll simply post some pictures as I get them and explain the best I can including any comments I get from Carl.

Carl e-mailed me today (June 6, 2007) and let me know that he’s starting on my frame tomorrow. Today he pulled the tubeset. I’m guessing the tubes from left to right are the top tube, seat tube (tapered), down tube (thickest), chain stays (tapered), seat collar, BB shell, and seat stays (straight).

Tubes are Feather-Tech down tube at 1.375″ outside diameter and , top tubes and seat tubes at 1.250″ outside diameter. The Chainstays are Nova Oval Taper and Seatstays are Nova Taper. The downtube is bi-ovalized vertically at the head tube and horizontally at the seat tube. This should make the frame plenty stiff at the bottom bracket and resist twisting at the head tube.

I had never heard of Feather-Tech, but here’s a description of the tubes from their website.

FeatherTech is a Colorado based company created to offer the very best in ultra high performance, state of the art titanium tubing.

With the recent plethora of composite and hybrid aluminum / carbon frames, it has become necessary to take titanium to the next level to “compete.” After all, you wouldn’t think of building custom frame with straight gauge steel or aluminum tubing. FeatherTech offers custom profile Titanium that is essentially “butted”, only much better (read why later) putting titanium back on top for your custom frame material choice.

FeatherTech considered conventional mandrel butting technology, but ultimately developed proprietary Custom Profiling methods to achieve more precise results and greater design flexibility.

FeatherTech has perfected this technology over the past several years. Our Research and Development team is now able to offer optimum thickness and strength to weight ratios for individual applications.

It is important to point out that Custom Profiling is also distinctly different than cold working, shaping, or swaging tubing. These methods simply shape the tube, keeping the wall thickness the same, and saving absolutely no weight. Custom Profiling actually removes material from the tube in the lesser stressed areas, offering true weight savings.

It is also very important to point out that oversize (OS) tubing is very necessary in the performance equation. Custom Profiling significantly reduces the tube weight while the OS tubing adds the resistance to flex and twisting. This combination truly offers the best of both worlds resulting in lighter weight and higher performance.

FeatherTech sources titanium from the very best, premium mills worldwide. The mills we use must first pass stringent independent lab tests. This is not as easy as it may sound. Next the mill must be capable of producing large diameter thinwall tubing. Searching the globe has only turned up two mills capable of producing our 2 inch O.D. tubing (used in Tandem bicycles) that can meet our tolerance and specification.

Here it is: (click on all images for full size)

Here the seat stays are getting mitered. I think it’s cool (and perhaps obvious) that he has a jig to get the exact angle the seat-tube will be intersecting the stays at. Also note the “blade” (I think Carl called it a “cutter”) that I assume matches the diameter of the seat tube that will be on the bike. I noticed that the little crossbar for the rear brakes are not on there yet – I suppose that makes sense as they should not go on until the stays are solidly attached to the bike and in firm place.

Main tubes getting mitered

And the chain stays getting mitered

At first I thought that applying vents to the bottom bracket meant that he was putting in the screw holes you see from the bottom and attach the derailleur cable guides to. In fact, these are drilling holes that allow air to pass through to the chain stays and the seat tube. I assume there’s one more that allows the flow of air to the down tube.

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