Seven Cycles Collaborative

Tubing sitting in the comfy chair

I mentioned this earlier but it bears more props:  last night we performed our first in-house steel tube butting tests for main triangles.  Mike S. is managing the tube aspect of the project and he just ran with the tubular ball, worked with Jon Henig—our senior production machinist and frame builder to run some tests.  Actually, only two tests.

What is tube butting?

In short, tube butting is a process which results in a tube that has various wall thickness.  In the bike world, the most common butted tube is on that is thick on both ends and thin wall in the middle sections.  The thick sections, after the tube is coped to become part of a frame, are usually about ¼ to 1/6 of the total length of the tube.

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Oh so limited.

In the Collaborative meeting yesterday we reviewed the high quality brazing recommended steel frame tubing options.  That’s a mouthful.  Because it’s a long set of limiting parameters, it also limits the legitimate tubing options that we can apply for this project.

Let’s start with sources:  In the bike industry, four serious sources exist for high-end steel bicycle tubing:  Columbus, Dedacciai, Reynolds, and True Temper.  I would think that, with four sources, there’d be plenty of options to mix and match.  Well, not true—at least from Seven Cycles’ perspective.

Now, which of the four companies offer tubesets that they specifically recommend for brazing—as opposed to TIG welding?  Only two of the four.*  That’s okay, in reality, I’d bet that a lot of lugged frame builders use tubing not specifically designed for lugs.

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In this evening’s Collaborative meeting we dug into, among other items, steel tubing.  Tubing is a big topic so we couldn’t cover all aspects in one meeting—it’ll probably take about 100 meetings.

Tubing is an important aspect because, among other reasons, it is the primary influencer of the bike’s ride characteristics.  So, we’ll probably end up spending more time and energy working on the Collaborative’s tube set than most other aspects of the bike.

Seven Cycles’ Mike Salvatore is managing the tubing aspect of the Collaborative.  So, during the meeting he helped run us through some of the facets of steel tubing, including:

• Selection options for luggable steel bicycle tubing:  I’ll post details of this in the next journal entry.  The options are a surprising.
• Tube butting process:  We’re going to run some tests in-house, on Thursday, to butt the tubing ourselves.  No easy task.
• Material strength overview:  We spent a good portion of the meeting discussing steel tubing options and how material strength plays a factor in the options available.  More on this later.
• Engineering aspects of tube diameter and tube wall thickness:  And even some ways in which tube butting influences durability and ride characteristics.
• Steel tube alloy options:  We discussed the properties of everything from the popular “cromoly” to the most exotic micro alloys to the more recent efforts of stainless steel.

Lots to cover later.

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