Workshop Stories: Rolf Vigor

[Johan Bornman]

Workshop Stories: Rolf Vigor.

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Most of you are familiar with the Rolf wheels. This particular wheel in the spotlight is the Vigor, a tandem wheel and I?m discussing the rear one.

 

 

 

Rolf Vigor Tandem wheels

 

A customer brought the wheel in to me, complaining that it keeps on breaking spokes and that he wants the wheel completely re-built with new spokes.

He pointed to the last straw, a spoke broken at the elbow where the spokes exits from the hub. I examined the rim for cracks to see if it is a viable proposition repairing the wheel but as luck had it, no cracks.

 

Rolf Dietrich, founder of Rolf wheels built a reputation on unconventional wheels and was single-handedly responsible for perpetrating the paired-spoke design. The design had nothing to offer from an engineering point of view, but was marketable. It was a mild success in the ?90s and today still survives in odd niches, noticeable with Campagnolo. The latest eye-brow raiser from Rolf is a 10-spoke rear wheel. That?s another story.

 

Back to the wheel on the operating table. Upon disassembly, it reveals some interesting characteristics. The nipples are concealed inside the rim and are much longer than conventional nipples, requiring the spoke to be almost 10mm longer than what would have been right for a wheel with exposed nipples. The used spokes came out bent where they entered the rim. This is because the arrival angle is more than 90 degrees on any cross-spoked wheel and the nipple wants to seat on the inside of the rim at exactly 90 degrees. This causes huge problems and dramatically reduces durability if there is thread at the bend. I recently pointed to the problem with a Shimano wheel, albeit that the thread was at the hub side.

 

 

Note the paired spoke design and spokes arriving at an angle to the rim. The nipples are seated inside, flush with the rim and thus at an angle to the spoke line.

 

A thread in the bend leads to a very prominent stress riser and premature spoke breakages. Rolf seems to have known this and designed his wheels so that the thread is removed from the stress zone by way of an extra long nipple. 10 out of 10 for that design.

 

 

Notice the severe bend in the spoke's neck, yet it never broke there. The nipple on top is a standard nipple and the ones on the spokes the Rolf nipples. Their long barrels require a longer spoke but removes the thread from the stressed bend area.

 

However, the spokes aren?t breaking at the rim, they?re breaking where they exit the hub. It?s a standard hub flange requiring J-bend spokes. However, the wheel was laced so that all the spokes exit the hub from the same side, causing a severe bend where two spokes cross right at the hub. This crossover creates an unstable zone where the spokes continuously bend in an exaggerated fashion as the wheel cycles. This brings about metal fatigue and broken spokes.

 

 

Spoke broken at the elbow at the hub. The spoke head would have faced upwards. Note the 4mm distance between spoke and hole - the amount of stretch in the tensioned spoke.

 

The spokes exit the hub on the outside, making me believe the designer did that to effectively create a wider hub (wider by half of the flange thickness) and therefore a stronger and better-braced wheel. He didn?t take the side-effects into consideration.

 

 

 

Same-side spoke exit makes for an oncomfortable cross right at the hub flange. I suspect the cut-out is an attempt to alleviate the resultant bulge.

 

A better solution would have been to create a standard alternating in-out spoke pattern at the hub, avoiding the big loose cross-over bend. That?s how I?ll lace the new spokes.

 

 

A poor photo but an attempt at showing the cross in profile. You are looking at the flange from the rim's side, at the place where the right spoke crosses the left. Notice the undesirable gap between right spoke and rim and resultant flex point that causes metal fatigue as the wheel cycles.

 

What I did find admirable was the elegant solution at the rim. Although the spokes bent quite severely there, none broke there (that I can gauge from talking to the customer). This solution should be used on all wheels with internal nipples, such as Reynolds and others that now escape me. It is a pity that the designer overlooked problems on the hub-side.

 

 

 

 

 

 

[andrewc]

Thanks Johan,

 

 

 

I always enjoy the Workshop Stories - and keep an eye out for them. Your effort to share your experiences is appreciated.

 

 

 

There seems to be much to learn in the cycling world where marketeers seem to have the final say in engineering designs. I saw a similar trend in the scuba industry where kit was marketed that served no real purpose and made no appreciable improvement over other designs, other than being New! and Improved! In some cases, these New! Improved! designs were downright dangerous.

 

 

 

Of course, I'm not saying that Rolf wheels are dangerous (but I may say that about a certain model of French wheelset where the marketeers have had a field day...).

 

 

 

Cheers,

 

 

 

Andrew

[jugheaddave]

thanks for an interesting article.

[TooManyMatts]

Interesting. thanks.

[Gobbo]

very interesting.

I had a pair of shimano 540's

kept on breaking rear spokes.

[Rocket-Boy]

These stories are the best. Keep them coming!