Why are spokes bent on the end anyway?



T

TBerk

Guest
Shouldn't the place where they come out be parallel with the rim? Are
there just such hubs being made and if so why aren't they common
place.

I found a spoke had pulled itself out at the axle end yesterday. That
along with the recent 'fatigue' thread, got me to thinking.


TBerk
 
On Apr 27, 6:24 pm, TBerk <[email protected]> wrote:
> Shouldn't the place where they come out be parallel with the rim? Are
> there just such hubs being made and if so why aren't they common
> place.
>
> I found a spoke had pulled itself out at the axle end yesterday.  That
> along with the recent 'fatigue' thread, got me to thinking.
>
> TBerk


It's called straight-pull. I suppose it was historically difficult to
make suitable hubs strong enough cheaply. And if it ain't broke, don't
fix it. Properly built wheels with conventional J-bend spokes can last
forever.

Joseph
 
On Sun, 27 Apr 2008 09:24:56 -0700 (PDT), TBerk
<[email protected]> wrote:

>
>Shouldn't the place where they come out be parallel with the rim? Are
>there just such hubs being made and if so why aren't they common
>place.
>
>I found a spoke had pulled itself out at the axle end yesterday. That
>along with the recent 'fatigue' thread, got me to thinking.
>
>TBerk


Dear T,

Originally, modern single spokes were straight. They threaded directly
into hubs on highwheelers and were laced radially.

Tangent lacing, which is stronger, was invented early in 1874, roughly
the beginning of the highwheeler era.

But tangent lacing was practically ignored until 1885 by hundreds of
highwheeler manufacturers, who happily used straight spokes and radial
lacing, much like wagon wheels.

Here are some simple 1890s radial straight-pull safety-bicycle hubs:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1890's+straight+pull+hubs.jpg

Straight spokes can be tangent laced, but the hubs need little arms
with holes drilled at different angles.

Here are some complex 1890s tangnet direct-pull safety bicycle hubs:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1890's+straight+pull+hubs+1.jpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1890's+straight+pull+hubs+2.jpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1890's+straight+pull+hubs+3.jpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1890's+straight+pull+hubs+4.jpg

The modern Mavic Cosmos wheelset uses radial direct spokes on its
simple front hub (like old highwheelers and the first pictures) and
tangent direct spokes on its more complex rear hub (like the second
set of pictures).

Spokes with elbows and hubs with side holes keep things simple and
allow different tangent lacing patterns--1x, 2x, 3x, and so on up to
8x.

Spokes with elbows also resist wind-up better than straight spokes.

By the 1890s, elbow spokes and hubs were replacing straight spokes and
hubs. They work so well and are so easy to manufacture that they have
over 99% of the bicycle market.

Here's a page that shows several varieties of the old direct
highwheeler spoke schemes:

http://www.hochrad.info/hochradseite/hochradteile/hochrad teile speichen.htm

Here's a later 8-cross tangent highwheeler hub with elbows:
http://i2.tinypic.com/5xq520p.jpg

Cheers,

Carl Fogel
 
A

Alexandre Kampouris

Guest
TBerk wrote:
> Shouldn't the place where they come out be parallel with the rim? Are
> there just such hubs being made and if so why aren't they common
> place.
>
> I found a spoke had pulled itself out at the axle end yesterday. That
> along with the recent 'fatigue' thread, got me to thinking.
>
>
> TBerk


This is what Jobst Brandt [1, p. 51] wrote about this:

<< Because spokes often fail at the elbow, hubs have been built that use
straight, elwowless spokes. [...] More recently, a hub was designed that
used straight spokes threaded at both ends. One end screwed into the
flanged while the other end used a conventional nipple. This hub allows
only the one spoking pattern for which it was designed. It is also
expensive and very difficult to repair if a spoke breaks in the hib.
These drawbacks make it unlikely that such hubs will become popular.
Another design [...] uses straight spokes identical to ordinary bicycle
spokes, but with no elbow bend. These spokes are inserted through a wavy
cup-shaped flange and end engaged in conventional spoke nipples at the
rim. Even though the shape of the flanges permits only one spoking
pattern, this method seems more promising than the threaded hub. >>

I dug up some relatively old French and German patent documents related
to elbow-less spokes.
http://Radio-BIP.qc.ca/Velo/FR2653069.pdf
http://Radio-BIP.qc.ca/Velo/DE3612772.pdf
http://Radio-BIP.qc.ca/Velo/DE3216396.pdf
http://Radio-BIP.qc.ca/Velo/FR2595993.pdf

I guess you'd find these designs in stores by now if they were succesful.

Alexandre

[1] Jobst Brandt, "The Bicycle Wheel", Menlo Park: Avocet Inc., 1981
 
I

It's Chris

Guest
Because it's easier (less expensive) to make a flat flange with holes
around the edge and bend the spoke end than to leave the spoke straight
and machine the more complex hub to accomodate it.

I have straight's on one set of my MTB wheels, it ain't pretty (not from
a machining POV)!

- -
Compliments of:
"Your Friendly Neighborhood Wheelman"

If you want to E-mail me use:
ChrisZCorner "at" webtv "dot" net

My website:
http://geocities.com/czcorner