God Hjulstämning Alla! Jag tar mig friheten att saxa följande ur min egen velomobilseminarieartikel fr 1998, inget är omodernt ännu tycker jag och hoppas att någon ger mig feed-back. Hälsningar Anders Brage.

"Where does energy go in small wheels?

Small diameter wheels are prone to stumble over obstacles. On soft ground, like a lawn or a gravel faced pedestrian path, they dig steeper holes to come out of than larger wheels do. I think this is the main reason for big wheels. A folded bike with big wheels however is to bulky. Bike wheels have for long been preferably large, until sir Alec Moulton combined a small wheel diameter with a suspension. The Dunlop invention of the pneumatic tyre gave rise to a new type of rolling resistance that is to day fairly often misinterpreted, though the Michelin brothers did invent a good solution to one part of the problem with their radial carcass tyre.

A plea for good bicycle tyres have been heard before and is still to be emphasised for small diameters. One major problem is said to be the low priced import giving developers no margin between the cost for materials and ready available tyres on the market. I think there is a technical approach with patents and profits awaiting for a truly dedicated developer.

The rolling resistance when no power is transmitted, as measured by Ian Sims Australia, give to faint a difference between tyres, to make up for the sensation of power drain when going uphill, changing from a racing bicycle to a mountain bike or a small diameter wheel bike. Does size really matter this much? I think not, because the sensation is the same if only tyre pressure is lowered.

The missing link may be the power transmitted from the drivetrain through the pneumatic tyre to the ground. It has to be transformed into stresses in the tyre carcass, and in my opinion, these stresses tend to return the deformed cross-section to the toriodal shape. Meaning, the tyre cross-section flattened towards the ground, is deformed back to a round shape by the stressfields in a diagonal carcass, producing a redundant work-out equal to squeezing a tennis ball. This can be designed away in three ways.

· One being a radial orientation of the filaments together with circomferential filaments building up the carcass, whereby the tractional filaments are separated from the filaments deformed by the ground. · The other, being a more wide shape of the tyre cross-section, seen on modern racing motor bikes, with a rim Width to tyre Height ratio slightly above one.

· Hence Wrim/Htyre >1. (equ 3)

This could also be accomplished by simply putting an ordinary tyre on to a wider rim, which however is hard to find. This ratio has a value close to one for very thin racing push bike tyres and less than 0.4 formountain bike tyres. I think proportion matters more than size uphill. I have not been able to test this hypothesis. · Third, the rubber compound, inherited from the car tyre industry, where damping is favoured, couldbe switched to a blend with a greater bouncing factor, leaving more of the deformation energy to be elasticly recoverable.

A possible all composite wheel has been made, to show the that it could be done. Soft spokes from Kevlar in Polyurethane matrix broke, after that they had been repeatedly bent at the rim.

The picture (finns på liggisthemsidan) shows a prototype all composite filament wound wheel, when loaded across a cable in a softened state, by closing the hubs to each other. Climbing capability enhanced by the elastic deformability and an inherent suspension that gives a minimal unsuspended weight and good dynamics."