--- In bentechriders@yahoogroups.com, "Russell Allen Zech"
<raz711@...> wrote:
>
> Folks,
>
> I have been having troubles with non-drive side spoke failures on
> the rear wheel of my Infinity LWB. I was hoping that someone here
> might have some advice. They failed on the 27" stock wheel, they
> evenutally failed on a used 700c wheel (concave Winemann off of a
> Trek 360)and again after I had it relaced.They have failed on a
> brand new Sun CR-18 with Wheelsmith DT spokes and an Ultegra hub
> that I just had built. The spokes are failiing at the bend right at
> the hub.

We need to know more about you and about the wheels - it does sound
like you're hard on them. Recumbent rear wheels can take a beating
because on some bikes they take most of the rider's weight, and,
unlike a regular bike, the rider can't stand on the pedals and bend
his knees to absorb road shocks. If the rider's a little heavy as
well, rear wheels need to be pretty beefy.

The bend in the spoke near the hub is its weakest point. Sometimes
spokes fail here because they're not a good fit in the hole in the
hub. As the wheel rotates and the spokes stretch and contract, the
heads fret at the hole. (If you take apart a well-used wheel, you can
see where the alloy has worn to fit the spoke here). Eventually, the
spoke worries its head off. "Eventually" may not be very long - a
wheel rotates an awful lot of times in a mile!

To prevent this, the spokes must be a really good fit in the hub
drillings. Thin spokes may save weight, but fail because they're too
loose a fit in the hub. Some builders put a little grease on every
spoke head. Also, many hubs are drilled so that the holes are
countersunk to accommodate the bend in the spoke - but only on one
side. Alternate spokes rise from the hub on the inside and then the
outside of the flange, so you can build the wheel so that every spoke
sits correctly in the countersink, or so that every spoke is threaded
the wrong way. Then the bend in the spoke is resting on a
right-angled metal edge. It'll saw through the spoke in no time flat.
You'll either do one or the other. If your builder's done the other,
your spokes will fail sooner.

What will also help is having a really well-built, well-tensioned
wheel. Machine-built wheels can perform well for years - if they're
only lightly stressed. This is unlikely to be the case with a heavy
rider on a recumbent bike. Their spokes are often quite loose. This
means there's more scope for them to stretch, flex - and fret at the
hub drillings. The non-drive side spokes are longer, and leave the
hub flange at more of an angle, so those are the ones that stretch and
fret the most.

A really good wheelbuilder will tension the spokes to minimize the
stretching and fretting.

You could also try more spokes. Heavy touring bikes and tandems used
sometimes have 40 or even 48 spokes. If all else fails, more spokes
means less load per spoke. Once upon a time, wheels built in a 4X
pattern were said to be stronger than the standard 3X (but I've never
managed to work out why this should be so - the spokes have to be
longer I think...)

So it sounds to me like you need to find someone who really knows what
they're doing building wheels, and have him (they are usually men;
don't know why - it seems one of those jobs that women might be better
at...) custom-build a wheel just for you, just for this bike. A
builder who really knows his stuff will be happy to guarantee the
wheel. If he won't, go elsewhere. Your builder probably needs to see
you and the bike, and discuss what sort of riding you do with it. It
wouldn't hurt if he could see some of the wheels that failed, too, and
learn from those.

> I had a frame failure about a year ago. The guy who rewelded it was
> not a bike builder but he did put it back where it was and welded a
> reinforcing plate to the area.
>
> Could some type of frame missalignment be causing the spoke
> failures? If so, what should I be looking for? I have been playing
> with this since last August and could use some advice.

That doesn't sound likely to me.

> Here is a link to a Yahoo group dedicated to the Infinity in case
> you want to see what it looks like.
>
>
> http://sports.groups.yahoo.com/group/InfinityRecumbent/?
> yguid=98801700
>