The Taiwan Bicycle
Manufacturing Industry Review

How Butted Aluminum Alloy Tubing is Produced – the strength of Taiwan’s bicycle component manufacturing sector

Glenn Reeves

Bicycle component manufacturing is highly distributed and specific; nobody manufactures complete bicycles in-house. Bicycle industry SMEs in Taiwan are at the center of multiple highly specific routines carried out and techniques applied. This feeds complex supply chains which all terminate in the assembly of a bicycle, the endpoint of the process.

In this post, I want to  highlight this by looking at a small but important part of the process that creates a bicycle frame, by briefly looking  inside an alloy tube processing workshop.

Frame-making involves at least four SMEs: 1.Tube jig manufacturer 2. Tube processing workshop 3. Frame welding and alignment. 4. Heat treatment. (The reader might like to consult the post on AL 6061 and AL 7005 in conjunction with this current post).

In this case it is the frame welding/frame alignment/finishing firm that oversees the whole process–the engineer produces the AutoCAD blueprint for frame construction and tubing jig design. The relevant workshop then carries out the work.

So when you are talking about a “frame-maker”, you are actually talking about an abstraction. This is because the activities that lead to the production of a frame take place in a variety of locations and contexts.

This detailed division of labor is a key strength of Taiwan’s component manufacturing sector. Within a few minutes drive around Taichung county’s Da Jia district are dozens of SME workshops all concentrating on specific processes. While this mode of industry organization does not in itself ensure high quality, having the industry organized in this way certainly firmly supports the  institutionalization of quality production across the board where quality is the aim, an aim that is generally achieved.

Incidentally, in relation to the Taipei International Cycle Show held every March, it is the sourcing of components that forms the focus of business for most trade visitors. This is literally the nuts and bolts (and a whole lot more of course!) of the industry.

Turning to the alloy tube processing workshop, what basically happens is that tubing of various lengths is delivered on one side. These move through machining processes inside the plant. The result is specific batches of tubing that are bundled up and stored ready to be picked up for transport to further processing for various purposes (mainly frame assembly)  in other workshops, on the other side: a basic input/output system.

For the purposes of bicycle frame construction, what  concerns us here is the machining of tube walls into different thicknesses, the procedure known as “butting”. Tubing, then, enters the plant as plain gauge and exits as a butted steel or alloy lengths ready to be worked into frames.

High end bicycle frame production employs tubes of varying wall thicknesses:

Chromoly butted frame - High Resolution photo

You can download this and zoom in to get a better look at the measurements. This is basically a cut-away example demonstrating double and triple butted tubing. At least I think there is triple butting in there ie. three different tubing wall thicknesses on some of the tubing. Looking at the photo now, the numbers are very hard to read. Anyhow, you get an idea of what we are talking about and this workshop’s speciality.

butted aluminum alloy bicycle tubing

This shot is a little out of focus. However you have a view of the machine that forms butted tubing out of plain gauge tubing.

Steel rods withthe desired gauge(s) are fitted to the machine. Tubes enter the process at the point where you can see the operator’s arm. The rod is inserted, then withdrawn. Then the tube is moved forward for the next process. At the end of the process it is cut and drops into a tray (visible here on the top left).

This takes care of the — all important — internal wall of the tube. The exterior is formed by using the appropriate circular steel die (visible right in front there).

butted aluminum alloy bicycle frame tubing

And there is no shortage of these. One for every gauge of tubing that you could want. And, of course, if the right one is not here, you can have one cut for you.

butted aluminum alloy bicycle frame tubing

Having a closer look at this gives you a better idea.

butted aluminum alloy bicycle frame tubing

As for the internal butting rods, there also is no shortage: the shelves at the back recede to the left, laden with jigs of different dimensions.

Coming back to the main theme, this directly displays the efficiencies of the industry as a whole. It would be an expensive and risky investment to have to produce these as a frame-maker existing as a stand-alone operation. If you are looking to engineer a particular design requiring complex butting , then this workshop (one of several) has the expertise and the technology at hand to enable you to do this — all within a few minutes drive.

On another level, you could say that the slogan “better, cheaper, faster” becomes, for the bicycle (component) industry, “lighter, stiffer, stronger” on the product development (read marketing)  field of battle!! An interesting question, then, becomes — is  marketing a simple by-product of technical expertise and product development, a way of converting product into cash? Or is marketing, actually, a key driver behind the whole process? Without marketing, and the benefits of advanced metalwork that support claims for the superiority of one product over another that it feeds upon, would this workshop exist?  I guess it depends as to whether you are situated as a consumer or as a producer. I’ll follow this some other time. In the meantime . . .

butted aluminum alloy bicycle frame tubing

. . . if you zoom in on this pic, you’ll be able to see the specifications of the jig written on the ticket. These ones are all fairly simple. There are, on the other hand, those like the following:

butted aluminum alloy bicycle frame tubing

The jig pictured here is employed to create 13-butted tubes! That is, tubing having 13 different wall thickness measurements. The boss showed me one they have developed for BMX bikes that will enable the production of 17 butted tubing, especially applied for handelbars. He was pretty proud of this and reluctant to have it photographed.

butted aluminum alloy bicycle frame tubing

On the far side of the workshop is a hydro-forming machine. It does not get much use since the workshop concentrates on higher-end al 7005 butted tubing. It’s easier and cheaper for most producers to get hydro-forming done (with al 6061) over in China.

butted aluminum alloy bicycle frame tubes

At the end of processing you will have butted tubing ready to go. These are seat-tubes for a new TT model for a very well-known company.

The purpose of my visit to this workshop today was for discussing issues to do with the production of appropriate tubing for a new model that I am developing. If I can get the timing right, I may be able to document the production of tubes for that model. That will give you a more detailed view of how butted tubing is produced and hopefully into other processes as well.

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