Spoke Pattern on Front Disc Hub

On 31/07/2014 01:18, wrote:
On Wed, 30 Jul 2014 11:00:22 -0400, Frank Krygowski
wrote:

On 7/29/2014 10:05 PM, wrote:
On Tuesday, July 29, 2014 9:46:16 PM UTC-4, Frank Krygowski wrote:
On 7/29/2014 6:58 PM, wrote:


my vote goes to lead spokes head out.

Why?

COMPLIANCE

i.e. to comply with the notion that the lead spokes should have their
heads out?

The difference in angle between head in and head out for an
approximately 11 inch long spoke seems to be about 0.2% of the
diameter of a 22 in circle. Is that a significant change when
calculating the load on a spoke?

As the angle gets closer to perpendicular to the hub, as it started
doing on the drive side when numbers of gears were multiplying but
widths hadn't grown, potentially yes :-)

(though pedantry forces me to point out that you can't compare angles
and lengths in the way you're doing - dimensionally incorrect).

On Thu, 31 Jul 2014 02:24:32 +0100, Clive George
wrote:

On 31/07/2014 01:18, wrote:
On Wed, 30 Jul 2014 11:00:22 -0400, Frank Krygowski
wrote:

On 7/29/2014 10:05 PM, wrote:
On Tuesday, July 29, 2014 9:46:16 PM UTC-4, Frank Krygowski wrote:
On 7/29/2014 6:58 PM, wrote:


my vote goes to lead spokes head out.

Why?

COMPLIANCE

i.e. to comply with the notion that the lead spokes should have their
heads out?

The difference in angle between head in and head out for an
approximately 11 inch long spoke seems to be about 0.2% of the
diameter of a 22 in circle. Is that a significant change when
calculating the load on a spoke?

As the angle gets closer to perpendicular to the hub, as it started
doing on the drive side when numbers of gears were multiplying but
widths hadn't grown, potentially yes :-)

(though pedantry forces me to point out that you can't compare angles
and lengths in the way you're doing - dimensionally incorrect).

True but it got an answer :-) But what does "potentially" means in
real life?
--
Cheers,

John B.

John B.

ANSWER ? minutiae .. !

trivializing grand ideas is trollish

On Thursday, July 31, 2014 8:40:13 AM UTC-4, datakoll wrote:


trivializing grand ideas is trollish

And aggrandizing trivial ideas...?

- Frank Krygowski

Frank, tuning has finesse.

On Thu, 31 Jul 2014 07:18:22 +0700, wrote:

On Wed, 30 Jul 2014 11:00:22 -0400, Frank Krygowski
wrote:

On 7/29/2014 10:05 PM, wrote:
On Tuesday, July 29, 2014 9:46:16 PM UTC-4, Frank Krygowski wrote:
On 7/29/2014 6:58 PM, wrote:


my vote goes to lead spokes head out.

Why?

COMPLIANCE

i.e. to comply with the notion that the lead spokes should have their
heads out?

The difference in angle between head in and head out for an
approximately 11 inch long spoke seems to be about 0.2% of the
diameter of a 22 in circle. Is that a significant change when
calculating the load on a spoke?


I neglected the flange thickness, and hence also the effect of head-in vs.
head-out, in my previous work:



which asumed that the spoke centre-line ran from the centre-line of the flange
thickness. In that the elongation due to spoke crossing was on the same order
of magnitude as you indicate above, and the calculated tension in the spoke
due to that amount of deviation was 8.5 kgf. Typical values for total spoke
tension are 100 kgf or more.

As for the original question, much depends on the mode of failure anticipated,
which in turn depends not only on the orientation of the spoke heads but also
on the materials used, the design and the quality of the manufactured parts,
the degree of crossing, the type of loading cycles to be experienced,
etcetera.

Flanges that are at 90 degreees to the hub centreline will have an additional
stress componenent as all the spokes will pull inward on the flange; but there
is also an additional stress possible in the spoke as the head-in ones will
have a bend where they pass over the edge of the flange. However, if the
dominant failure mode is breakage at the nipple end then head-in vs head-out
vs flange strength is all moot.

As for head-in vs. head-out for leading vs. trailing there is a slight
possibility that a mtbf difference exists for spoke-elbow failure, as the
head-in ones may have that extra bend, and the internal strain attempting the
unbend the head would thus be shared (and at the elbow itself somewhat
angularly displaced); I leave the magnitude and sign of that difference as an
exercise for those who tire of numbering the grains of sand on Chesil beach.