Question: Two wheeled wheel spokes

I would think that the spokes are at a tangent to the inner hub in order to place the thin wire spoke in a state of tension instead of compression. A thin wire will handle much more of a tension load than a compression load. The tension force of each spoke is offset by the spoke 180 degrees from it.

Tangential spokes help transmit the torque from the hub to the tires from your pedaling, you might radically spoke a front wheel (track/time racers do it often) but a rear wheel would wobble and twist pretty badly if you didn't tangentially mount it… For more reading : http://www.exploratorium.edu/cycling/wheel2.html

I would guess it is not so much tensile vs. compressive loading as normal vs. shear loading. When you're accelerating or decelerating, torques are transmitted between the rim and hub. If the spokes were completely radial, the spoke loading in such a situation would be pure shear, and they would probably deform over time. Making them tangential to the hub means that they bear transmitted torques in at least a partially normal manner. You can't avoid the shear completely, but I'll bet it attenuates it a great deal.

My reasoning goes like this: Using a coat hanger, staighten it out and cut off the ends, now try to push a heavy object with it, it will bend and not do a very good job of moving it, now fashion a hook on one end and try to pull something heavy with it. You can pull a much heavier load that pushing, illustrating the state of tension and compression. I agree that tangential spokes handle torque better than radial spokes.

I agree with your reasoning, but I don't think this is an issue with spoked wheels. The spokes go all the way around, so if you look at a situation where a given spoke would be placed in compression, there will always be a symmetrically opposite spoke that would be placed in tension, and the spokes in tension are actually doing all the load-bearing work.

I think shear vs. normal stresses in torque is the more important factor.

Simply think of the stress on the spoke if you apply brakes attached to the hub.

Just to add to the other comments: Placing the spokes at a tangent allows you to weave the spokes. Bicycle wheel manutacturers typically use a 4 cross weave for production line bicycles. It is the strongest, but it also adds a small amount of weight that has to be rotated with the wheel, which does make a big difference when it comes to rapid acceleration (i.e. think skinny tires for racers). 3 cross and 2 cross weaves are commonly used by racers. There is less weight, but also an associated loss of strength. There are specifications available to use radial spokes, but the weakness of the wheel limits its use to racers who have little need to brake and only occassional needs for rapid acceleration. That is, track or velodrome racers.

Radial spoking on the non-drive side of rear wheels and the front wheels of bicycles is now more the norm than the exception, esp. on higher level equipment. For the definitive text on the subject I recommend "The Bicycle Wheel" by Jobst Brandt.

Thanks