Mavic MA-40 - Piece of Crap? - Page 5

Mark Janeba writes:

>> Curiously the ancients also had dupes among them. Some Fiamme tubular rims had rivets at the
>> joint to "keep then from coming apart in use" and some did not. There was a fable about spokes
>> adjacent to the joint needing to be crossed to keep the rim together. That ignored that 32 spoke
>> wheels had parallel spokes at the stem and joint as do any regularly spoked wheels with spoke
>> numbers evenly divisible by four. N MOD 4 = 0.

> Did you mean divisible by 8, and N MOD 8 = 0?

Yes, I slipped a bit binarily. Of course, all standard spoke patterns are N MOD 4 = 0 having left
and right, leading and trailing spokes. The 36 and 24 spoke wheels have crossed spokes on the seam
(that lies opposite the stem) and 48's, 40's, 32's and 16's have parallel spokes at the seam if they
are parallel at the stem, where they should to be parallel.

> Otherwise all traditional wheels would meet the criterion.

> Mark (I've built 32s,36s,40s and 48s, but not 30s or 34s) Janeba

Thanks,

Jobst Brandt jobst.brandt@stanfordalumni.org

both sides. it appears to have been welded then abraded "smooth" afterwards. the abrasion extends
about 2" before & after the join which is why the pads sink into the depression and have a tendency
to wedge on the way out.

imo, welded rims are better because they offer more even weight distribution - no heavy spots at the
insert. however, as this case illustrates, subsequent machining is pretty much mandatory.

Tim McNamara wrote:
> jim beam <uce@ftc.gov> writes:
>
>
>>you're assuming a high spot. as you say, that would be trivial to correct. in the case of the
>>cxp14 however, it's a low spot. "removal" of the bump would require machining the whole rim.
>>
>>comparative width measurements of some unbuilt rims i have:
>>
>>ma3 cxp14
>>21.10 19.88
>>21.10 19.92
>>21.10 19.90
>>21.10* 19.66*
>>
>>* at the rim joint.
>
>
> Well, now, that's an interesting scenario. Is the rim equally pinched on both sides of the seam or
> just one side?

Yeah, Merry Xmas to you too and even to the ones who still believe that Elvis is alive and that a uneven rim seam is better than a smooth machined one.

On 24 Dec 2003 16:29:19 GMT, vecchio51@aol.com (Qui si parla
Campagnolo) wrote:

>Bacardi is a loon, don't feed him...

An unpleasant one at that.

--
Dave...

BaCardi <usenet-forum@cyclingforums.com> wrote:

> even to the ones who still believe that Elvis is alive and that a uneven rim seam is better than a
> smooth machined one.

This is a technical newsgroup, and your comments deserve fuller explanation.

Please let us know your arguments in favor of machined rims. Please address the effects of the weld
on strength an durability of the alloy used. Compare the weights of machined rims versus unmachined
rims. Compare the cost to produce, and consider the cost against the simple procedures used, or not
used, to eliminate an uneven rim seam.

--
Ted Bennett Portland OR

Ted Bennett wrote:
>
> BaCardi <usenet-forum@cyclingforums.com> wrote:
>
> > even to the ones who still believe that Elvis is alive and that a uneven rim seam is better than
> > a smooth machined one.
>
> This is a technical newsgroup, and your comments deserve fuller explanation.
>
> Please let us know your arguments in favor of machined rims. Please address the effects of the
> weld on strength an durability of the alloy used. Compare the weights of machined rims versus
> unmachined rims. Compare the cost to produce, and consider the cost against the simple procedures
> used, or not used, to eliminate an uneven rim seam.

Or we could just machine rims from aluminium billets, and pay several hundred dollars for
each rim.

Tom Sherman - 41½ N, 90½ W

jim beam <uce@ftc.gov> wrote in message news:<mqkGb.1851$1O6.340@newssvr27.news.prodigy.com>...
> you're assuming a high spot. as you say, that would be trivial to correct. in the case of the
> cxp14 however, it's a low spot. "removal" of the bump would require machining the whole rim.
>
> comparative width measurements of some unbuilt rims i have:
>
> ma3 cxp14
> 21.10 19.88
> 21.10 19.92
> 21.10 19.90
> 21.10* 19.66*
>
> * at the rim joint.

Dear Jim,

Am I correct in thinking that your cxp14 rim's two ends meet smoothly on each side, but are slightly
narrower than the rest of the rim?

(I vaguely expected the rim to be the same width, but slightly misaligned at the joint.)

If so, do you know if this this a normal result for however rims are bent into hoops? That is, are
the two ends grabbed so hard by some gizmo that they're routinely squeezed a little bit narrower
than the rest of the rim?

It's Christmas, so I'm staring at shiny round objects with fascination. Thanks for raising an
interesting point.

Carl Fogel

Carl Fogel wrote:
> jim beam <uce@ftc.gov> wrote in message news:<mqkGb.1851$1O6.340@newssvr27.news.prodigy.com>...
>
>>you're assuming a high spot. as you say, that would be trivial to correct. in the case of the
>>cxp14 however, it's a low spot. "removal" of the bump would require machining the whole rim.
>>
>>comparative width measurements of some unbuilt rims i have:
>>
>>ma3 cxp14
>>21.10 19.88
>>21.10 19.92
>>21.10 19.90
>>21.10* 19.66*
>>
>>* at the rim joint.
>
>
> Dear Jim,
>
> Am I correct in thinking that your cxp14 rim's two ends meet smoothly on each side, but are
> slightly narrower than the rest of the rim?

yes

>
> (I vaguely expected the rim to be the same width, but slightly misaligned at the joint.)
>
> If so, do you know if this this a normal result for however rims are bent into hoops? That is, are
> the two ends grabbed so hard by some gizmo that they're routinely squeezed a little bit narrower
> than the rest of the rim?

doubt it. the cxp14 appears to be welded, so some form of post-join finish work is mandatory for
smooth braking - but doing it in just the weld area is not the solution - needs to be machined all
the way around to maintain dimensional accuracy. from what i've seen, most unmachined rims are
simply joined with an insert.

>
> It's Christmas, so I'm staring at shiny round objects with fascination. Thanks for raising an
> interesting point.
>
> Carl Fogel

Read page 2. Then come back and talk to me.

And another thing. This is a technical newsgroup. Please let us know your arguments in favor of seamed rims. Since you are so heavily in favor of the old seams in rims, please let us know why. Compare weights. Compare cost. Compare cost per weight ratios. Finite Analysis is also desirable.

Dave Kahn <dkahn400@yahoo.co.uk> wrote:
: On 24 Dec 2003 16:29:19 GMT, vecchio51@aol.com (Qui si parla Campagnolo) wrote:
:
:>Bacardi is a loon, don't feed him...
:
: An unpleasant one at that.

carl, this loon business is your fault.
--
david reuteler reuteler@visi.com

Zog The Undeniable <ggg@hhh.net> wrote:

> Chalo wrote:
>
> > Sun rims are, to the best of my knowledge, nearly all available in polished bare aluminum, most
> > with eyelets too.
>
> Their silver ones - I have Rhyno Lites [1] on the touring bike - have a very thin anodising (as do
> many silver rims) which is rubbed off by the brakes after only a couple of hundred miles. I doubt
> this thin anodising is particularly harmful to the rim, and it does protect against spots caused
> by road salt.

I have built many Rhyno Lites, and I have found them to come in four variations (not including the
Rhyno Lite XL, a wider and taller rim). Those are black with black sidewalls, black with bright
machined/sanded sidewalls, satin silver anodized, and bright polished bare aluminum. The most common
by far in the aftermarket (in my experience) are the latter type, which have no anodizing at all and
a near-mirror finish.

It is that highly buffed bare finish that I have come to associate with Sun rims. It looks
especially nice on the Venus deep-section road rim and the Big City BMX rim, 34mm wide and
20mm tall.

> [1] actually about 1" wide...you should see the non-lite version!

The Sun Rhyno rim is noticeably narrower than the Rhyno Lite, just much heavier. I have seen it in
only two finishes: satin silver anodized, and chrome plated for BMX wheels. As a very heavy, not
very oversized rim, it never gained too much popularity outside of almost-exclusive use on
triplets and quads! I have a set of 48 spoke wheels built with 700c Rhynos, and they're just so
strong it's boring.

Chalo Colina

jobst.brandt@stanfordalumni.org wrote in message news:<yelGb.4833$XF6.105197@typhoon.sonic.net>...

[snip]

> . . . In fact you could take a rim made of individual N unattached segments, each with a spoke at
> its midpoint, butted together without an alignment spud and ride it with no perceptible
> difference from a one piece rim.

[snip]

> Jobst Brandt jobst.brandt@stanfordalumni.org

Dear Jobst,

Am I correct in thinking that this N-section rim with N spokes and no alignment spuds is a thought
experiment, not anything actuallly tried like the Kevlar-string spoked wheel?

I can see an imaginary rim with miraculous cuts half-way between each spoke working as you suggest.

But how would you assemble it in reality? Wouldn't tightening the single spoke N at each mid-point
pull and tilt each rim section N sideways in alternate direction out of the intended hoop before the
section-to-section tension was enough to hold the rim sections steady torsionally?

(I like imaginary engineering, but would love to learn that it's actually been done. Maybe the
sections could be pre-tensioned by assembling them inside a tire with loose spokes, inflating the
tire to jam the sections firmly together, and then tightening the spokes?)

Gotta go--I hear someone at the chimney.

Carl Fogel

Carl Fogel writes:

>> You're assuming a high spot. As you say, that would be trivial to correct. In the case of the
>> CXP14 however, it's a low spot. "Removal" of the bump would require machining the whole rim.

>> Comparative width measurements of some unbuilt rims I have:

>> ma3 CXP14
>> 21.10 19.88
>> 21.10 19.92
>> 21.10 19.90
>> 21.10* 19.66*

>> * at the rim joint.

Hold the phone! Is there a discontinuity at the joint or a width variation, and how abrupt is it?
This has the classic form of lies of the second kind, where the statement although accurate conveys
an untrue message. Nowhere is there a mention of discontinuity in the rim in a misaligned rim joint
that purportedly causes wheels to lock when braking. That the claimed lockup is untrue is apparent
from the lack of end-over crashes cause by rims that aren't welded and machined.

> Dear Jim,

> Am I correct in thinking that your CXP14 rim's two ends meet smoothly on each side, but are
> slightly narrower than the rest of the rim?

> (I vaguely expected the rim to be the same width, but slightly misaligned at the joint.)

> If so, do you know if this this a normal result for however rims are bent into hoops? That is, are
> the two ends grabbed so hard by some gizmo that they're routinely squeezed a little bit narrower
> than the rest of the rim?

Rim extrusions are coiled (rolled) into a helical multi-turn hoop and made into rim hoops by a cut
perpendicular to the extrusion edge (a slight angle to the coil axis. Resulting short end pieces are
recycled while the hoops in between are made into rims. There is no end effect other than pushing
them onto a filler spud that closely fits the inside contour.

> It's Christmas, so I'm staring at shiny round objects with fascination. Thanks for raising an
> interesting point.

I don't have such a variation in my MA-2 rims and also have no offset at the joint. As I said, the
wheel that was run over by a motorcycle had a bad wow and a misaligned joint, but that was
repairable and is not readily visible now.

Jobst Brandt jobst.brandt@stanfordalumni.org

Carl Fogel writes:

>> ... In fact you could take a rim made of individual N unattached segments, each with a spoke at
>> its midpoint, butted together without an alignment spud and ride it with no perceptible
>> difference from a one piece rim.

> Dear Jobst,

> Am I correct in thinking that this N-section rim with N spokes and no alignment spuds is a thought
> experiment, not anything actually tried like the Kevlar-string spoked wheel?

In a way I have experienced that in a rim in which the alignment insert at the joint was so loose
that the rim was easily separable by a little pull and alignment was neither radially or laterally
properly constrained. With effort I aligned the ends while tensioning the spokes and realized that
when finished, this would be, in effect, a compression-friction joint that was stable purely from
the compressive force.

It was these considerations from which I developed the equation N*T/2pi for rim compression and
those of rim compression by tire inflation. I suppose you saw the effect of tire casing cord angle
from inflation pressure, and how the cord angle visible in clear reinforced Tygon tubing was arrived
on, the angle found in any good pressure hose that prevents it from changing length when
pressurized.

> I can see an imaginary rim with miraculous cuts half-way between each spoke working as you
> suggest.

> But how would you assemble it in reality? Wouldn't tightening the single spoke N at each mid-point
> pull and tilt each rim section N sideways in alternate direction out of the intended hoop before
> the section-to-section tension was enough to hold the rim sections steady torsionally?

In wheel building, no one spoke is tensioned alone. The whole complement is tightened incrementally.
As I said, the sloppy rim joint with which I worked had just such a characteristic and it was
apparent that only friction and compressive force held it in place.

> (I like imaginary engineering, but would love to learn that it's actually been done. Maybe the
> sections could be pre-tensioned by assembling them inside a tire with loose spokes, inflating the
> tire to jam the sections firmly together, and then tightening the spokes?)

Well that depends on whether you have to do it 36 times to believe or if once is enough. Not
everything has to be repeated to the limit to assess its results. For me one free joint is enough,
for others two adjacent ones may be enough. I don't see doing it 36 times although if I had such a
rim, it might be fun to do. The only problem would be making 36 zero thickness saw cuts.

> Gotta go--I hear someone at the chimney.

Don't feed the animals.

Jobst Brandt jobst.brandt@stanfordalumni.org