Silver Case

Luke, Ling, Woei, and I did a short bike run for breakfast today. I was riding my Favorit fixed-gear bicycle. On the way back heard a repeating noise. Unusual. Single-speed track-gears make almost no noise, because there are no freewheels or derailleurs. When I looked down I could see a wobble in the rear tire, so I figured a spoke broke.

When I inspected closer, I saw that the spoke was fine, that in fact the cheap aluminum spoke nipple had snapped its head off. At least that will be easier to fix, but no wonder quality wheelbuilders refuse to use aluminum nipples on wheels. That wheel has literally seen less (far?) than 100km on it.

The wheel issue reminded me that I needed to have a follow-up appointment with my road wheel I rebuilt back in January. It is running true but I was more interested in the spoke tensions and how they’ve held up since I first built the wheel.

Wheel

The results look pretty good. Not perfect, but liveable.

When I did the math

January Measurements:

Drive Side tension (mm of deflection) averaged 1.85 with a std dev of 0.08mm (or 4.17%)

Non-Drive Side tension averaged 1.22 with std dev of 0.08 (6.76%)

March 2010 Measurements

Drive Side: 1.82mm average with std dev 0.09 (4.80%)

Non-Drive 1.13mm average with std dev 0.10 (8.60%)

So the wheels loosened up a bit and slackened a bit, but still quite ok. The worst drive-side spoke deviated by 10%. On the non-drive side, I had three spoke unacceptable (-14%, -20%, +11%).

This should be quite fast and easy to tune up, and then I’ll check again in a couple months. I guess I’ve probably ridden a little over 700km on this wheel so far?

Interesting, I was talking to Brian Roddy, president of Rolf Wheels at the NAHBS. I told him that my friend had been using a Rolf wheel forever and claimed it was the strongest wheel he’d ever used. Brian told me that how they built the wheels is (1) build the wheel (2) press the rim from each side with 400lb force (3) re-tension (4) press again with 400lbs (5) do a final retensioning. That means the spokes are really well seated in. Pretty cool, and it makes results. I guess I make some sort of jig to press wheels like that myself — just need a big lever and a proper die to press against it.

I’ve recently spent three monastic evenings in the Straits Dispatch workshop building the front triangle of a new bike. Our current project is a lady’s size Le Chacal tuned for mountain bike use. This has been a far more precise and efficient operation than my first project.

I learned during the first bike that Measurement and Marking is an absolute prerequisite to any hope of accuracy and control.

So this time, we modeled it in Bike Cad Pro, a parametric CAD program designed for bicycles. From this I can get accurate dimensions and angles on any part of the frame.

I put more care into scribing the lines too, using a carbide scriber (basically a steel pencil) and making the lines as thin as possible. When I’m trying for sub-millimeter accuracy, it doesn’t help to have a scribe line 0.8mm wide drawn in pencil that rubs off.

I didn’t measure twice, cut once. I measured many, many times and cross-checked measurements using different techniques. I caught a few errors this way.

Cutting miter with belt sander. (The blue lines are NOT cut markings!)

Mitering a single joint now takes less than 15 minutes. That’s big savings versus hand-mitering, which can take 30-60 minutes. Of course the belt sander is more precise now that we’ve figured out tricks of clamping and feeding the stock.

It’s pretty close to being done. Two more miters tomorrow and it’s ready to be stuck on the jig and brazed. In the meantime Sulaiman has been working on some tricky rear-triangle engineering.

On a side-note, I’m excited to be attended the 2010 North American Handmade Bike Show in Richmond Virginia in late February. The craftsmen displaying their projects there have stunning work to show off.