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To be fair, Royce do specifically prohibit radial lacing on all their hubs. Building radially, seeing a cracked hub and then saying "Well, it's 20 hole you'd think you could do it despite all warnings to the contrary from the manufacturer," is unreasonable.
Radical lacing puts a tremendous amount of force through a hub flange, so choosing the right hub for the job which is warrantied for a specific spoke pattern and then using the appropriate spoking pattern is the responsibility of the end user or professional wheelbuilder.Going back to Hope hubs, the photos seen in this thread are a catastrophic failure of a special kind. I haven't seen, personally, any other hubs fail in that manner; though what you say could potentially be a factor in such cracks.
But I do know of other hubs failing catatrophically, even if laced correctly according to manafacturer's specs. Online I've seen Chris King hub failures, DT Swiss, Rohloff, and other well known hubs. These mostly seem to be fatigue failures after many, many thousands of miles of riding, but then CNC machined hubs by their nature can have stress risers that help facilitate such failures.
I know of one very well known wheelbuilder who built a with a Chris King hub, the hub failed, and Chris King blamed him, citing unduly high tensions as a the main cause of the failure. After many years of not using a tensiometer the wheelbuilder then promptly bought one.The one Hope hub failure I saw personally (A Hope Pro II Evo front) I believe it possible that unduly high tensions were a factor. A home wheelbuilder had a built with straight guage spokes (he had also crossed the valve hole, indicating his wheelbuilding experience was minimal) and the average tension in the wheel perhaps 140kgf+ (hard to assess completely accurately with a couple of spokes having no tension.)
IIRC there are a couple of manufacturers who don't recommend using straight guage spokes on their hubs because of their lack of faith in the average wheelbuilder's ability to accurately measure tensions.
Rohloff specifically prohibit using 13g spokes, as do White Industries on their tandem hubs, because of the same issues; plus the spoke hole diameter being too small.
t_w-
Yes, Royce hubs come with a yellow leaflet explaining not to lace radially, clearly it was ignored. That said, if other manufacturers are happy with radial lacing on their 20 H hubs (including Hope), then what does it say about Royce shells?
Funnily enough I recall a rear DT 240 hub failing on the non drive side flange in one of their handbuild Mon Chasseral wheels, which you can't blame high tension for. Low tension is just as bad, if the spoke loses tension and the head is allowed to dig and grind in the hole at every revolution.
My comment re. Hope hubs failures and jumping is because I know Hope is very popular among downhill riders, trial and all sorts extreme bike users... I don't think you can experience such a catastrophic failure out of nowhere, "just riding along" so to speak... in the same way as carbon frames don't open up in half while you are riding, but they might do so if you crash against a bus
ugosantalucia
Seen a cracked royce flange in the flesh... the guy was not supposed to build it radial, but being a 20 holes hub, one would expect it to be an option...
It seems to me that my sample size is more representative of a few photos on the web of which we know very little... the large crack might be the result of a four feet jump with a bad landing... people on mountain bikes do crazy stuff with their bikes.