OK, time for a new discussion on an old, old subject.
Many light weight rear hubs are now being designed for a radial spoke pattern only, on the non-drive side (NDS).
My hypothesis is that this is an incorrect application of the physical dynamic forces in a cog-driven spoked wheel.
So I ask that this thread be limited to discussion rear wheel spoke patterns, as there will be plenty to discuss.
1. Since the hub flanges must be offset from the centerline in order to accept the cassette, the DS and NDS hub flanges experience different stresses. One goal is to equalize these flange stresses as much as possible.
2. Another goal is to equalize the spoke tension on each side, to better keep the wheel true.
3. Another goal is to equalize the stresses at the rim holes. (The pulling force from each side of the hub)
1. A smaller (lower) hub flange experiences less stress than a high flange.
2. A longer spoke requires more tension than a shorter spoke to do the job (resist external forces on the wheel). that
3. More spokes on a hub side tend to result in more pulling force at the rim. Which is to say that fewer spokes under higher tension equal the force of more spokes at lesser tension.
4. We are discussing the pattern of radial on the NDS, and a crossed pattern (usually 2x) on the DS. For the sake of discussion and because of the design of these modern hubs, assume that each hub flange has the same number of spokes, regardless of the pattern.
The assumption in a crossed DS + radial NDS is that the torque force starting from the cassette will reach the DS flange more so than the NDS flange.
I don't agree. Modern hubs have enough material between the flanges, and are strong enough to almost completely resist torque equally at each flange.
Old-school hubs with a very narrow center section did exhibit this dynamic, but modern hubs have "cured" this issue with larger cores.
Now we deal with the spoke dynamics. Because of the offset, the NDS spokes are always going to be longer than the DS.
It appears that the radial NDS pattern is trying (among other things) to reduce the NDS spoke length. After all, a radial spoke is shorter than a 2x spoke. Combined with a 2x DS, this seems to be an attempt to equalize the spoke lengths used on each side, with the implied objective of equalizing spoke tension because of more equal spoke lengths.
The problem is that this only addresses spoke tension, without dealing with hub flange tension, or tension at the rim. A radial spoke, being shorter, will require less tension. Therefore, it aggravates the inherent difference in tension between the DS & NDS due to the uncurable offset.
This is further aggravated by the flange design, which is typically lower on the NDS. Again, I have to assume that this parameter is an attempt to cure the spoke angles. The narrower DS angle will be relieved with a higher flange, thus angling the DS spoke out just a hair more.
And a lower flange on the NDS makes those spokes angled in just a hair more. And, the lower NDS flange will lengthen the NDS spokes, thus demanding a hair more tension, which admittedly helps. But, using a radial pattern on the NDS is overall a shorter spoke than a 2x. So, the tension gain of a lower flange is actually dimished over using a 2x NDS spoke.
To cut this short, that is my issue. Using a radial NDS spoke actually results in a larger overall difference in forces between the sides. With the high DS flange /low NDS flange, use of 2x pattern on both sides will get the most out of that design. The use of a shorter spoke by using a radial pattern doesn't really gain anything, in my book, it makes the sides even more asymmetric in overall forces.
So these modern hubs designed only for NDS radial spokes (especially the straight-pull spokes with an even lower effective flange diameter) are missing the overall effect. If I had to have radial on one side, I'd actually rather have it on the DS (like ZIPP) than the NDS.