Fall Color in Ohio

A graceful beauty.

From Revolution Cycles, a new shop in Columbus, Ohio. They're apparently too busy building gorgeous bikes to activate their new web site. Expect more from Jared Cavileer and friends.

For Spoke Nerds Only

Please don't read further if you are not a spoke engineering nerd.

One of the best examinations of wheel physics and spoke performance is a 1996 paper by Henri Gavin, Bicycle Wheel Spoke Patterns and Spoke Fatigue.

Its findings and predictions stimulate numerous revisits every year in forums and exchanges that explore the principles of bicycle wheels. On page 11 he refers to spoke testing conducted at Stanford in 1984 and 1985 by Wheelsmith. My brother Jon and I were developing a superior spoke at that time and the convenient and friendly presence of Stanford in our neighborhood led to some ground breaking research. Spokes were tested and some conclusions reached. Recently, Charles Ramsey speculated what would be the ideal spoke design, one in which breakage at the elbow was as likely as at the thread.

Spoke surface texture and microstructure.

With a 14 gauge (2.0mm diameter) spoke, breakage at the elbow is much more likely than at the thread. By contrast, with a 15 gauge (1.8mm diameter) spoke, the opposite is true: thread breakage is more likely. Much of this is owed to the ISO thread pitch used on both diameters (56 tip). Jobst Brandt has noted that, in a perfectly rational world, a finer thread pitch would be used on the thinner, 15 gauge spokes, to reduce the stress riser the thread presents. Here is part of Charles' thinking:

8 of the Wheelsmith spokes tested broke at the threads 68 broke at the elbow. The spokes were also tested at different levels of stress. The HP Gavin paper gives the formula as Log S = -.3 Log N +4.12 the breaks followed a normal distribution with a standard score of .072 If you draw 2 normal distributions separated by 2.5004 standard scores the center where they overlap is 8/76 area on one and 68/76 area on the other. The center is half the possible breaks spokes didn't break at the threads and the elbow at the same time. Feeding 2.5004 standard scores back into the equation gives Log S = -.3 Log N +4.12 + 2.5004*(.072) solving for any number of cycles gives a stress difference of 1.514 times so a plain gauge spoke is effectively 1.514 times as strong at the threads than at the elbow. If you make a spoke 2.46mm at the elbow and 2.0mm at the threads if will have an equal chance of breaking at the elbow as at the threads. This spoke can be made and I believe it will fit in Shimano hubs. The nipple could be made at 1.36 rather than 1.27 this will let you tighten the spokes an additional 7 percent. I believe a Weinmann 519 rim will take a .156 inch nipple drilled for 14 gauge spokes. I have never been able to crack one of these rims at the spoke hole though I have bent around 10 solid 10mm axles on the rear. With rolled threads the inside of the threads has a diameter of 1.8mm there is of course a stress riser so the center of the spoke could be made thinner perhaps 1.7mm such a spoke would no be stiff enough for me I get a lot of pannier steer so I would stick to a single butted spoke.

His calculations seem valid to me and speculation that a 2.46mm x 2.0mm single butted spoke would be more ideal is also logical.

Helps explain the high success reported with Alpine, DH and Strong spoke models. 2.3mm x 2.0mm may lack some elbow thickness (compared to Charles' 2.46mm) but they virtually eliminate spoke breakage. Rather than transferring the failure to the thread, in practice they seem to transfer it to the hub (flange crack), rim (hole crack), or time (eventual mishap).

Single butted spoke.

Even so, there is another quirk to this application that deserves mention. Throughout our spoke making careers, the more we tested and watched empirical outcomes, the more we listened to metallurgists, the more it seemed that wire quality trumped all other factors. This is not a scientific observation since the number of variables is so high a reliable deduction process dwarfs my means. Still, we regularly saw outstanding outcomes when the wire was flaw-free. The worst hub, rim, tension, and load situations were easily handled with flaw-free wire. It is more than the absolute mechanical properties of the wire. It's processing success, making spokes not imbedded with fatigue catalyzing flaws in their microstructure.

So, if there were a wire with 30% lower properties but from which a super consistent spoke could be made, you would have better results compared to wire with greater potential but harder to work. This, of course, is a strike against stainless with its work hardening propensity.

Therefore, my quest for an ideal spoke is driven more by the need for consistency than by geometry. Spoke breakage is a combination of high number of fatigue cycles with a pre-existing metal flaw - a crystal discontinuity, hardness anomaly, impurity, etc. The simple presence of high fatigue is not enough. The wire must offer up a flaw. Spokes that lasted 100,000 miles exist. Their properties are consistent with their ingredients. But flaws they did not present.

A good case in point were tandem wheels built for the budding West Coast scene in the '80's. Success came from using the best quality spokes in ANY gauge, not better dimensions in inconsistent wire. Maybe part of the lesson is that bicycle spokes, despite their gossamer appearance, are actually over-dimensioned for the task. If so, 2.0mm wire is more than enough as long as the wire is consistent.

Thanks, Charles, for your predictions, but I'll continue thinking about superior wire. Of course, upping elbow diameter is an obvious freebie since hub makers have been drilling oversized holes for some time.

Going New with the Old

In June of this year (2010) we shipped a pair of Elegant tubular rims to Donald Dickson in Virginia. He built them up on NOS Campagnolo large flange hubs from the 1970's that he found on eBay.

"I must be the only person in the country riding the Ghisallo rims," he said. No, it just seems like that since so much of the cycling world follows in each other's footsteps. Check the previous post, you're not alone.

On Oct 9, Donald rode a local Ultra Gran Fondo from Mexico City to Acapulco on the toll highway.

70km/hr in Mexico on a 1983 Schwinn Superior

On account of problems with the route, the riders were portaged 140km, so the total became 240km. Not bad. "Plenty of compliments on the aesthetic factor. The ride is smooth."

Sometimes, to be ahead of the crowd you have to go in another direction.

The Hero in Us

Some days life can seem pretty ordinary, even boring. But now and again, each of us manages to break up the monotony with something heroic. Some more than others.

Last year, Tom Inskeep, from Maryland, bought a set of wood wheels. I sensed he was taking them for more than a decorative, restoration look. In fact, he had a wild scheme in mind: equip his bamboo Calfee with wood rims and race New Hampshire's legendary Mt. Washington Hill Climb. 526 starters. One on wood rims.

Bamboo and Beech!

Well, he trained on this new rig and finished in the top third. Bravo! It's enough to climb the mountain. Doing it on a largely wood bicycle puts the achievement into another category of heroism. This is the stuff Tom's grandchildren will someday remember him for.

He owes it all to wood!

Take two bits of wisdom from Tom's exploit:

(1) Wood rims are genuinely functional. They're fast, smooth, and fun. Tom didn't deserve a handicap in the hillclimb. His bike and wheels were fully competitive.

(2) Make sure you're planning something heroic for yourself. What defines heroism? That's for you to decide. But grab something bold, unconventional, and memorable. Your life and family deserve the stimulation. If it involves wood rims, send me the story and a picture!

Masters at Work

While many of you admire and some ride wood rims, nearly no one has seen how they are made. So, you can imagine my pleasure when Antonio sent me a 20 minute movie in which he and his father, Giovanni, demonstrate their craft.

Watch some familiar wood working machines and some built 100 years ago, expressly for wood rims. There's nothing like true artisans with the tools of their trade.

We're grateful to Daniele Di Lodovico, a doctoral student at the University of Washington, for his partial translation of the Cermenati's description. Kristina Hjertberg applied the subtitles.

In this three clip session, you'll see the basic method for building a Ghisallo rim. Naturally, the details vary from rim to rim. Lately, the highest performance tubular rims are made from equal thickness, 4mm laminations with cotton cloth between each. These are thin enough to bend dry.

Of course, you can't see the decades of experience that guide these masters in selecting wood, orienting and matching grain, wetting and drying laminates, and shaping the final rim. It's as non-automated, a hands-on process as you will see: the handiwork of a family of dedicated artisans, in the name of cycling. Each rim contains a generous portion of their life and wisdom.

Just click each link, Part 1, Part 2, and Part 3, and enjoy!