MA3 rim failure, where to now

"Simon Brooke" wrote in message
. uk...

But against that a three cross wheel is substantially springier than a
radial.

I'd like to see some backup for this, please.

Assuming you mean what is commonly meant by "springier" and
"substantially" - i.e deflection per unit force and a difference of, say,
10%.

Numbers please.

"jt" writes:

"Simon Brooke" wrote in message
. uk...

But against that a three cross wheel is substantially springier than a
radial.

I'd like to see some backup for this, please.

Assuming you mean what is commonly meant by "springier" and
"substantially" - i.e deflection per unit force

Yup...

and a difference of, say,
10%.

Probably.

Take a radial and a three cross and bounce 'em off the workshop floor,
and you'll see what I mean.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/
;; Our modern industrial economy takes a mountain covered with trees,
;; lakes, running streams and transforms it into a mountain of junk,
;; garbage, slime pits, and debris. -- Edward Abbey

Simon Brooke wrote:

Take a radial and a three cross and bounce 'em off the workshop floor,
and you'll see what I mean.

If you do that with tires on and inflated, I predict any
difference you see will be due to the tires (Try 20psi vs 100psi
to see an exaggerated example).

If you do that without a tire on the rim, I predict you will
hear a loud clang and learn nothing about the properties of
the wheel lacing.

Ben
I'm pretty certain about the loud clang

In article ,
Simon Brooke wrote:

Take a radial and a three cross and bounce 'em off the workshop
floor, and you'll see what I mean.

So, umm, perhaps you can figure out a way to prove your point without
us bashing perfectly good wheels into the ground?

Tim McNamara writes:

In article ,
Simon Brooke wrote:

Take a radial and a three cross and bounce 'em off the workshop
floor, and you'll see what I mean.

So, umm, perhaps you can figure out a way to prove your point without
us bashing perfectly good wheels into the ground?

OK, first I confess I'm just repeating what I was taught when I learned
to build wheels. You build touring wheels more crossed to make them
springier and more compliant; you build racing wheels less crossed to
make the bike flippier and more precise. Since I like my bikes
flippier I've always tended to build my own wheels less crossed, and I
don't really have that much 'seat of the pants' experience of whether more
crossed really gives a more compliant ride.

But consider it as a problem of geometry. On a radial wheel pressure
in the plane of rotation can only be resisted by the direct
enlongation of spokes, each forming a simple radius of the circle (and
to a lesser extent by the out-of-round distortion of the rim, but
that's a constant wrt the problem). On semi-tangent wheels, each spoke
is longer than the radius of the circle, possibly by the 10% quoted
earlier. Furthermore, because they're tangential, movement of the rim
doesn't only stretch them, it moves them (slightly) in their
web. Finally, unit movement of a point on the rim wrt the hub does not
translate into unit enlongation of any one spoke; it translates to
slightly less than unit movement. So given that the spokes are equally
springy, it seems (to me at least) logical that longer spokes which
move less will allow greater movement per unit force than shorter
spokes which move more.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

;; MS Windows: A thirty-two bit extension ... to a sixteen bit
;; patch to an eight bit operating system originally coded for a
;; four bit microprocessor and sold by a two-bit company that
;; can't stand one bit of competition -- anonymous