Radial-spoked rear wheel

[NickJP]

We're finishing off a tour of Austria, northern Italy, and Switzerland by watching the UCI world road championships in Zurich. I've noticed that the rear motor hubs on one of the brands of hire ebikes here are radially spoked. I would have thought that this was a recipe for problems, but apparently not - several of them have come flying past me on the steep climbs, with the hub obviously putting out somewhere close to maximum power, and the wheels survive that without failing.

[Jdsk]

"Pros and Cons of radial spoking":
viewtopic.php?t=143933

Jonathan

[Brucey]

...the hub obviously putting out somewhere close to maximum power, and the wheels survive that without failing.....

the hub is a fairly large diameter, meaning the spokes don't see the worst torque loadings. Often, that flange design has two spoke drillings per 'ear', so most builds look radial, but are actually ~x 0.5. What they have done there isn't a spectacularly good idea, but it is probably OK because something else will break first.

[531colin]

Possibly radial spoking is the "least bad" option.
If you wanted crossed spoking, with a huge hub like that you could only look at 1 cross, and even then the spokes would approach the rim at a silly angle (a long way from a right angle), so you would need a rim drilled at the appropriate angle, which will be expensive and difficult to replace worldwide.
Presumably the wheel isn't dished, and the left and right flanges are connected by a huge cylinder, so spokes both sides will support the drive torque.

[Brucey]

as built, the wheel relies upon friction between the spokes and the flange for transmission of drive torque. This friction is only likely to be present in sufficient quantity when the spokes are tight. It sounds a bit shonky, relying on friction like that. However, whilst it wouldn't be my first choice for a wheel build, it is probably OK, after all, tyres are held on with friction too.

[rogerzilla]

Low-rider bikes with 144 spokes per wheel also use radial rear wheels.

[Chris Jeggo]

An experiment. Sit on the bike with plenty of weight on the back wheel. With the front brake on hard, press hard on a pedal in the fully forward position and get someone to see if the hub rotates a fraction while the rim does not. I would love to know the result.