Breaking Spokes

Mike Prime said:

jim beam <[email hidden]> wrote in message

Quoted message said:

there's elastic & plastic strain. metallurgical
stress relief is only achieved in the 1-3% /plastic/
strain region.

Significant stress relief occurs before 1% applied total
strain. All that is required for stress relief is that
under load the stress range over the spoke cross section
is made smaller. Since stress will unloaded evenly
(elastically), this smaller stress range is retained and
the residual stresses are relaxed. Yes you do need some
plastic strain, since the spoke will load evenly until
part of it yields. Since some of the spoke has tensile
residual stress, a significant portion of the spoke cross-
section will have some plastic strain by the time the
applied stress equals the yield strength, which happens
well under 1% strain for these steels.

ok, makes sense.

Quoted message said:

Aluminum plate is stretched to 1-3% plastic strain to
achieve a greater degree of stress relief than you can get
at lower levels and to stress relieve in the transverse
direction at the same time. However, significant relief
occurs much earlier. In the below paper recently published
by Alcoa, see Figure 5. Although simplified, it
illustrates the concept. Curve "A" reaches the yield
strength before .3% strain. By 0.6% strain, the whole part
has yielded. No further stress relief occurs with further
stretching. In reality, materials are not perfectly
plastic, so further stress relief does occur for larder
strains. However, the majority occurs before 1% strain.

(Don't let the title fool you. Microstructural effects,
etc, are what limit the stress relief to something like
90-95% relief instead of 100%. It has little bearing on
stress relief in spokes, which is not trying for 100%
relief). Title:A simplified analysis of the effect of
microstructure gradient on the stress relief of aluminum
plates and extrusions Author:Karabin, ME ; Barlat, F ;
Becker, R Institution:Alcoa Tech Ctr,
Journal:INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES; SEP
2003; v.45, no.9, p.1483-1503

Mike Prime

i don't work in the materials biz any more, so i don't have
ready access to this paper - would like to read it tho.

what you say sounds logical. the percentages i quoted were
from one of my old textbooks for drawn steel wires & tubes.
can you recommend a text that might be useful for further
reading on highly worked stainless wires? i was under the
impression that at high dislocation densities, their strain
fields tended to interact to the point where they had the
lattice effectively "locked up" with continued work only
adding to this situation, not alleviating it. wouldn't this
be the case here?

great to hear from you mike!

jb

RWM said:

<[email hidden]> wrote in message
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Quoted message said:

Roger Zoul said:

With a 36 spoke wheel you would not have to worry about
walking home

even if you did break a spoke. They will roll along quite
nicely till you can get a chance for a replacement. In
the past I have ridden over 30 miles with a broken spoke
on my 36 spoke hub, screwed in a replacement spoke and
not had to mess around with retrueing.

Not true. I ruined two 36 spoke rims by riding them home.

I have ridden a 32 spoke front wheel with a broken spoke on
2 occasions, each with no long-term damage. Each post-break
ride, however, were not terribly long. They were each in the
neighborhood of 10 miles.

--
Greg Estep

Tim McNamara said:

Quoted message said:

You'd need to go with a different rim, perhaps a Torelli
Master which is similar to an MA2.

I think the Master is a bit more of a racing rim than the
MA2. It is rated at 435g rather than the 490g or so for the
MA2. That is if I remember correctly. That said, I do like
the Master.

http://www.torelli.com/par-" rel="ugc nofollow noopener">torelli.comhome.htmlOpen ↗
ts/wheels.html&1 Master. 435 grams. A good all-round racing
and training rim available in 32 and 36 hole. Silver $43.90.

Ukai used to make a MA2-like rim. It was the model "20A." I
don't know of a source. They are double-eyeletted, about 19-
20 mm wide, and weigh about 490g. I believe they are box
section. They are not machined. There is anodizing, but it
is very thin and is easily penetrated with ohm-meter probes.
JB has stated that a very thin layer is unlikely to cause
crack initiation problems like thick anodizing does.

David Reuteler said:

... i've built 4 pairs of wheels now and i'm very glad to
have the experience. in fact i've built all but one pair
of the wheels i'm currently using. there are, however, a
lot of people who should probably not be building their
own wheels. or cooking their own food for that matter...

Food can be cooked?

--
Tom Sherman – Quad City Area

"Roger Zoul" <[email hidden]> wrote in message
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Quoted message said:

If I dent a rim, I don't expect to get that fixed
for free.

A sloppy job with a mediocre spoke wrench led me to
strip a few nipples on my rear wheel. My LBS says the
wheel must be entirely rebuilt, that the rim and all the
spokes are shot, which is [censored]. The wheel has maybe
2-3K miles on it, and the rim was just barely out of
true when I took it in.

I couldn't get a straight answer from the dude on the
phone: How much for the full re-build vs. a re-build
with the old rim but new spokes vs. just replace the few
bad spokes (which of course he claims is eight or so vs.
the maybe 3-4 which are actually nicked) and true it up.
Instead he wanted to go on and on about how a damaged
nipple makes it impossible to get the spoke off without
slicing it under pressure, which of course will warp the
rim and make it unusable, so a full re-build with a new
rim and all new spokes is the only answer.

Shop owners: If a guy doesn't have the ability to
converse on the phone and doesn't give a [censored] about the
price a customer has to pay, Don't let him talk to
customers!

Rico in Sacramento