Re: Durable Rims for Road Wheels - Recommendations?
daveornee
Steve Sr. Wrote:
> I am looking to build a set of road wheels and am looking for
> suggestions for suitable rims. Of course, I would like them to be as
> light as possible without sacrificing the durability.
>
> While we all appreciate a litle nostalgia please limit your
> suggestions to rims that are still available. Previously I think I
> remember hearing about Mavic rims being a good choice but not any
> more. Apparently their quality has suffered in the race for "stupid
> light" and marketing fad of the day. What would you build up a pair of
> wheels with today?
>
> BTW, I weigh about 160 pounds and the roads in this area are somewhat
> rough but not too many potholes to hit.
>
>
> Thanks,
>
> Steve
Velocity Aerohead with Aerohead OC in rear makes a good combination for
someone your weight.
I suggest Sapim Laser 14/17 DB spokes front and left rear + Sapim Race
14/15 DB spokes right rear.
I just built another pair that way and they work very well.
--
daveornee
Michael Press
Steve Sr. <Nos...@nospam.com> wrote:
> I am looking to build a set of road wheels and am looking for
> suggestions for suitable rims. Of course, I would like them to be as
> light as possible without sacrificing the durability.
>
> While we all appreciate a litle nostalgia please limit your
> suggestions to rims that are still available. Previously I think I
> remember hearing about Mavic rims being a good choice but not any
> more. Apparently their quality has suffered in the race for "stupid
> light" and marketing fad of the day. What would you build up a pair of
> wheels with today?
Actually newer clincher rims that manufacturers present as
their best rims are heavier than the best rims available
20-25 years ago. Those older clincher rims were light,
fully socketed, box section, un-anodized, not welded, not
`machined', and inexpensive. Clincher rims are one bicycle
part that are in every regard worse than they used to be.
As for a recommendation, see if you can find some Torelli
Master rims.
--
Michael Press
jim beam
> In article <cps4e2181gi89af1c...@4ax.com>,
> Steve Sr. <Nos...@nospam.com> wrote:
>
>> I am looking to build a set of road wheels and am looking for
>> suggestions for suitable rims. Of course, I would like them to be as
>> light as possible without sacrificing the durability.
>>
>> While we all appreciate a litle nostalgia please limit your
>> suggestions to rims that are still available. Previously I think I
>> remember hearing about Mavic rims being a good choice but not any
>> more. Apparently their quality has suffered in the race for "stupid
>> light" and marketing fad of the day. What would you build up a pair of
>> wheels with today?
>
> Actually newer clincher rims that manufacturers present as
> their best rims are heavier than the best rims available
> 20-25 years ago. Those older clincher rims were light,
> fully socketed, box section, un-anodized, not welded, not
> `machined', and inexpensive.
and many modern rims are lighter, higher profile and therefore stiffer,
available with double eyelets just like before, box section just like
before, anodized so they don't corrode for those of us that ride when
the sun's not shining, welded for strength and consistency and balance,
machined for more consistent braking performance and at $65 for an open
pro, inexpensive. the double-eyeleted replacement rims for my mavic
cosmos wheels were $60 the /pair/. how much were you paying for an ma2
20 years ago and what's that worth in todays money?
> Clincher rims are one bicycle
> part that are in every regard worse than they used to be.
untrue, by any logical metric.
jim beam
> I am looking to build a set of road wheels and am looking for
> suggestions for suitable rims. Of course, I would like them to be as
> light as possible without sacrificing the durability.
>
> While we all appreciate a litle nostalgia please limit your
> suggestions to rims that are still available. Previously I think I
> remember hearing about Mavic rims being a good choice but not any
> more. Apparently their quality has suffered in the race for "stupid
> light" and marketing fad of the day. What would you build up a pair of
> wheels with today?
>
> rough but not too many potholes to hit.
>
>
> Thanks,
>
> Steve
>
- if you want them + good rims + a good build, get a mavic cosmos
wheelset. open-pro type rims, straight pull spokes to resist fatigue,
and very very well sealed hubs. you'll easily spend the same money on
hand built wheels with inferior hubs. they cope with my weight just
fine - your measly #160 is no problem.
MykalCrooks
"Steve Sr." <Nos...@nospam.com> wrote in message
news:cps4e2181gi89af1c...@4ax.com...
> I am looking to build a set of road wheels and am looking for
> suggestions for suitable rims. Of course, I would like them to be as
> light as possible without sacrificing the durability.
>
> While we all appreciate a litle nostalgia please limit your
> suggestions to rims that are still available. Previously I think I
> remember hearing about Mavic rims being a good choice but not any
> more. Apparently their quality has suffered in the race for "stupid
> light" and marketing fad of the day. What would you build up a pair of
> wheels with today?
>
> BTW, I weigh about 160 pounds and the roads in this area are somewhat
> rough but not too many potholes to hit.
>
>
> Thanks,
>
> Steve
>
Velocity rims and Sapim spokes.
http://www.velocityusa.com/
http://www.sapim.be/
Built a pair with the Deep-Vs and Velocity hubs and laced each with 36
Lasers. Like 'em.
mC
Qui si parla Campagnolo
daveornee wrote:
> Steve Sr. Wrote:
> > I am looking to build a set of road wheels and am looking for
> > suggestions for suitable rims. Of course, I would like them to be as
> > light as possible without sacrificing the durability.
> >
> > While we all appreciate a litle nostalgia please limit your
> > suggestions to rims that are still available. Previously I think I
> > remember hearing about Mavic rims being a good choice but not any
> > more. Apparently their quality has suffered in the race for "stupid
> > light" and marketing fad of the day. What would you build up a pair of
> > wheels with today?
> >
> > BTW, I weigh about 160 pounds and the roads in this area are somewhat
> > rough but not too many potholes to hit.
> >
> >
> > Thanks,
> >
> > Steve
Velocity Fusion or Aerohead
Mavic OpenPro of CXP-ss
DT-1.1
Fusion or CXP-33 fronts-28 2 cross, Rev spkes. All rears, 14/15/3cross
brass. DT, Aerohead and OpenPro front 32 3cross, Rev spokes...
Sapim spokes are fine but hard to find in all lengths.
D'ohBoy
Qui si parla Campagnolo wrote:
> Sapim spokes are fine but hard to find in all lengths.
thorusa.com. All lengths (or as many as one would need for a common
rim and hub combo).
D'ohBoy
Robin Hubert
$50 or more per wheel!?! Are they that much better than DT?
Robin Hubert
Ernie
While you guys are on the topic of rims, what about open pros versus
MA3? MA3 is cheaper, heavier, single eyelet, but the extrusion has 3
boxed sections and I believe I saw it was listed as suitable for use as
a touring rim? So would this be a stronger rim than open pro?
thanks,
Ernie
Art Harris
> While you guys are on the topic of rims, what about open pros versus
> MA3? MA3 is cheaper, heavier, single eyelet, but the extrusion has 3
> boxed sections and I believe I saw it was listed as suitable for use as
> a touring rim? So would this be a stronger rim than open pro?
You definitely don't want an MA3, but I doubt you'd find any. They were
replaced with the Open Sport which is a bit heavier, but till single
eyelet. The MA3 had problems with spokes pulling through.
The Open Pro has sockets (a.k.a. double eyelets) and are lighter.
Art Harris
thomas.t...@gmail.com
> I am looking to build a set of road wheels and am looking for
> suggestions for suitable rims. Of course, I would like them to be as
> light as possible without sacrificing the durability.
>
>
Sun CR-18, half the price of a Mavic Open Pro, at least as durable, and
a whopping 50 grams heavier (probably less than the Open Pro's
manufacturing tolerance).
Good luck,
Tom
jim beam
>
> So you are saying that it is possible to find good, durable, and well
> sealed pre-built wheels?
that's been my experience, yes. i only bought some to see if all the
negative hoopla here on r.b.t was accurate, and have found my
pre-built's to be perfectly reliable. [with the exception of trashing
rims on a giant pothole at least - but that's not the wheel's fault.]
>
> After all of the talk and answers I have been hearing was that if you
> wanted wheels that met these criteria you pretty much had to have
> them custom made out of select components.
sure. a good quality hand built wheel can be a joy, but two factors
stand against them:
1. it's /very/ hard to find a good builder. i've tried about 6
different highly reputable builders here in the san francisco bay area
and only one has proven to me that he can build a wheel that stays true
under my weight. that's len at the bike nook in sf.
2. i was also surprised to discover that low spoke count wheels can be a
substantial benefit when riding in strong cross winds. i proved that to
myself again the other weekend. had a flat so quickly grabbed a spare
32 spoke wheel and used that on my commute across the golden gate
bridge. it was startling how much difference the extra spoke count made
to cross-wind handling. next day, back to normal, 24 count front on the
mavic cosmos, much less wrestling required. try that for yourself some
time.
>
> The pre-built wheels seemed to be pretty much like the Real Design
> Supersphere "boutique" wheels I currently have. Low spoke count and
> inferior components at rip-off pricing. The only thing I have found
> good about these wheels is the sealed bearings. The freehub isn't
> sealed hardly at all and now at 4000 miles the rear rim has cracked.
stick to major brands and make sure they haven't been "helped".
>
> I would definitely be interested in looking at complete pre-built
> wheels if they meet the well sealed and durable 32 or 36 spoke
> criteria. You specifically mentioned the Mavic Cosmos are there others
> as well that I should be considering?
i only mention the cosmos because i have direct personal experience of
them and their hub seal proficiency. i weigh #205 and have found them
to remain perfectly true straight out of the box. they do have the
lower spoke count, but if they work with my weight, they'll /definitely/
work with yours. i've also got a pair of shimano r540's which i've
found reliable, but i wouldn't' recommend them for wet stuff because
they just have standard shimano seals.
>
> It looks like my other option would be to go with Phil hubs
sure. while they'll be just dandy, you'll still be using j-bend spokes
and be dependent on finding a competent wheel builder.
> and work
> up from there since no one has much regard for the sealing on
> Shimano's road hubs and I don't think you can put a 10 speed road
> cassette on an MTB freehub.
i'm pretty sure that if they're both shimano, you can. the freehub
bodies are identical afaik. it's only the 10-speed d/a that can't take
the 9-speed cassette. check sheldon's web site - i think he's got a
cross-compatibility chart.
>
> Thanks,
>
> Steve
Dave Mayer
> On Tue, 15 Aug 2006 21:49:04 -0700, jim beam <nos...@example.net>
> wrote:
>
> So you are saying that it is possible to find good, durable, and well
> sealed pre-built wheels?
>
I doubt it. Possible exception: Campagnolo wheels. Big $$ though.
Modern rims are generally poor, as anodizing, machining, seam welding and
the lack of nipple sockets are all major problems. Oh, and the current
generation rims weigh a ton.
I find older rims such as MA2s, Sun M14s and Ambrosio Elites to be clearly
superior.
I get my rims from the basements of older bike shops. I've never paid more
than $35 for a rim. Actually, I rarely pay this for an entire wheel.
Mate the older rims with Shimano cassette hubs, double-butted stainless
spokes, and most importantly a good wheelbuilder, and you have the parts for
a perfect set of wheels.
carl...@comcast.net
wrote:
[snip]
>2. i was also surprised to discover that low spoke count wheels can be a
>substantial benefit when riding in strong cross winds. i proved that to
>myself again the other weekend. had a flat so quickly grabbed a spare
>32 spoke wheel and used that on my commute across the golden gate
>bridge. it was startling how much difference the extra spoke count made
>to cross-wind handling. next day, back to normal, 24 count front on the
>mavic cosmos, much less wrestling required. try that for yourself some
>time.
[snip]
Dear Jim,
My almost flat, non-aero front rim (not even box section) and 700c x
26 front tire and rim are about 38mm thick.
Most posters would have thicker tire and rim combinations.
At a circumference of about 2100mm, that's 38 x 2100 = 79,800 mm^2 of
tire and rim, as viewed by a side wind.
With about 290mm of my 36 straight 2mm spokes exposed, that's 36 x 290
x 2 = 20,880 mm^2.
Some crude theoretical calculations:
290mm 2mm 38mm 36 32 28 24
spoke spoke rim+tire total spoke spoke spoke spoke
count mm^2 mm^2 mm^2 change change change change
----- ------ -------- ------- ------ ------ ------ ------
36 20,880 79,800 100,680 100.0% 102.4% 104.8% 107.4%
32 18,560 79,800 98,360 97.7% 100.0% 102.4% 105.0%
28 16,240 79,800 96,040 95.4% 97.6% 100.0% 102.5%
24 13,920 79,800 93,720 93.1% 95.3% 97.6% 100.0%
So on my front wheel, it looks as if the simple sideways area changes
only about 5% between 32 and 24 spokes.
My wheel, of course, maximizes this difference with thick 2.0mm
straight spokes and thin rim+tire combination.
With thinner spokes and a thicker box-section or even aero rim, the
effect on area of a spoke count reduction from 32 to 24 would be even
smaller.
With straight 1.8mm spokes (a rough approximation of the kind of thin,
butted spokes often mentioned) and a rim+tire thickness of about 45mm
for a modest box-section with mild aero profile, reducing the exposed
spoke-length to 283mm (like a wheel hanging in my garage) . . .
2100 x 45 = 94,500 mm^2 rim+tire side-view area
36 x 1.8 x 283 = 18,338 mm^2 spoke area
283mm 1.8mm 45mm 36 32 28 24
spoke spoke rim+tire total spoke spoke spoke spoke
count mm^2 mm^2 mm^2 change change change change
----- ------ -------- ------- ------ ------ ------ ------
36 18,338 94,500 112,838 100.0% 101.8% 103.7% 105.7%
32 16,301 94,500 110,801 98.2% 100.0% 101.9% 103.8%
28 14,263 94,500 108,763 96.4% 98.2% 100.0% 101.9%
24 12,226 94,500 106,726 94.6% 96.3% 98.1% 100.0%
This suggests that most posters would see a 3.7% drop in side-view
front wheel+rim+spoke area if they dropped from 32 to 24 spokes (or
gain 3.8% if they added 8 spokes to a 24-spoke wheel).
Aerodynamics is a tricky matter, so raw side area may somehow be
deceptive
But the 8-spoke count reduction sounds like less than a 3% change.
Moving from one kind of rim to another in my poorly stocked garage can
reduce side area from 94,500 mm^2 to 79,800 mm^2, which is 8.4%.
almost three times as much.
The winds on the Golden Gate vary more than that much every day. They
also blow sideways against the handlebars, fork legs, levers, hands,
and arms of the rider.
So I'm curious what the spoke thicknesses and exposed lengths are on
the two wheels that you rode, as well as how thick the tire plus rim
is on each wheel.
The weight would be interesting, too. At speed, a heavier tire and
wheel have more angular momentum and should be more stable in gusting
winds.
Maybe someone will have a link to wind tunnel tests, or an explanation
of how the spokes have a much greater effect than would be expected.
Cheers,
Carl Fogel
Smokey
Steve Sr. wrote:
>
> So you are saying that it is possible to find good, durable, and well
> sealed pre-built wheels?
>
> wanted wheels that met these criteria you pretty much had to have
> them custom made out of select components.
>
> Supersphere "boutique" wheels I currently have. Low spoke count and
> inferior components at rip-off pricing. The only thing I have found
> good about these wheels is the sealed bearings. The freehub isn't
> sealed hardly at all and now at 4000 miles the rear rim has cracked.
>
> wheels if they meet the well sealed and durable 32 or 36 spoke
> criteria. You specifically mentioned the Mavic Cosmos are there others
> as well that I should be considering?
>
> up from there since no one has much regard for the sealing on
> Shimano's road hubs and I don't think you can put a 10 speed road
> cassette on an MTB freehub.
>
>
> Steve
I've had good luck with my custom wheels that were built by Colorado
Cyclist. They've got Ultegra hubs, 36 14ga spokes laced in a cross-3
pattern, and Mavic CXP-33 rims. I haven't had to lay a spoke wrench on
them in over three years, including some rough gravel road riding. I'm
not sure how well sealed they are, though. I haven't done much rain
riding with them.
Smokey
Qui si parla Campagnolo
BUT the supplier of Sapim in the US-KHS(not the MTB KHS) does not have
all lengths. If I'm going to stock up on sapim spokes, to replace the
5000 or so I have in DT, I'll want to pay wholesale, thanks.
jim beam
> "Steve Sr." <Nos...@nospam.com> wrote in message
> news:brh7e29jh9qhjkbv9...@4ax.com...
>> On Tue, 15 Aug 2006 21:49:04 -0700, jim beam <nos...@example.net>
>> wrote:
>>
>> So you are saying that it is possible to find good, durable, and well
>> sealed pre-built wheels?
>>
>
> I doubt it. Possible exception: Campagnolo wheels. Big $$ though.
>
> Modern rims are generally poor, as anodizing, machining, seam welding and
> the lack of nipple sockets are all major problems. Oh, and the current
> generation rims weigh a ton.
anodizing protects, machining ensures consistency, welding ensures
strength, consistency and better weight distribution, and the eyelet
thing is a complete red herring. i'm surprised you didn't try to say
that machined rims are thinner:
http://www.flickr.com/photos/38636024@N00/121453841/
>
> I find older rims such as MA2s, Sun M14s and Ambrosio Elites to be clearly
> superior.
er, weight of the ma2 vs. open pro please?
jim beam
thanks carl. believe me, the most surprised person on this subject is
me. when i first compared these wheels, i took them both [same rim
profile and tires] and swapped back and forth on the same day same test
route. no doubt about it - the 24-spoker is /much/ less of a wrestle.
the comparison is that when i ride the 32, i have to be alert to both
sudden steering changes as well as balance due to wind on my body,
particularly rounding the northern pylon, with steering being the
dominant concern. on the 24, the dominant issue is balance, not
steering. if you find yourself in sf, i'll loan you the two wheels so
you can try for yourself. oh, and it's also noticeable when riding with
others. two people same place, same wind gust, you can see one deviate
much more than the other.
Scott Johnson
> Built a pair with the Deep-Vs and Velocity hubs and laced each with 36
> Lasers. Like 'em.
Deep-V's are what you want if you want something
that will shrug off an IED blast.
--
Scott Johnson / johnson dot sa at comcast dot net
Matt
> "Steve Sr." <Nos...@nospam.com> wrote in message
> news:brh7e29jh9qhjkbv9...@4ax.com...
> > On Tue, 15 Aug 2006 21:49:04 -0700, jim beam <nos...@example.net>
> > wrote:
> >
> > So you are saying that it is possible to find good, durable, and well
> > sealed pre-built wheels?
>
> I doubt it. Possible exception: Campagnolo wheels. Big $$ though.
I really like my Campy Protons, typically around $400/pair I think (I
got 'em as part of a kit). And my neighbor's got a pair of Ventos that
are heavy, but pretty inexpensive and durable.
Mike DeMicco
jim beam <nos...@example.net> wrote:
> and the eyelet thing is a complete red herring.
Why? Eyelets/sockets distribute the load over a wider area and thus the
rims are less likely to crack. All the rims that I've had crack had no
eyelets/sockets.
--
Mike DeMicco <blaster186...@comcast.net>
carl...@comcast.net
<blaster186...@comcast.net> wrote:
>In article <t7GdnYGGEadk-3nZ...@speakeasy.net>,
> jim beam <nos...@example.net> wrote:
>
>> and the eyelet thing is a complete red herring.
>
>Why? Eyelets/sockets distribute the load over a wider area and thus the
>rims are less likely to crack. All the rims that I've had crack had no
>eyelets/sockets.
Dear Mike,
I have no objection to eyelets and sockets, and I expect that they do
exactly what you say.
But the plain 36-spoke rims (no-box-section, no sockets, no eyelets)
on my 1998 Schwinn LeTour lasted around 35,000 miles at a rough guess
with no cracks.
They spun at about 20 mph on daily 15-mile rides that involve about 6
miles of deteriorating bike path with cracked concrete slabs and
endless tree root cracks in the asphalt. (A "Caution Trail Damage"
sign is cheaper than repairs.)
Bike, bags, and rider are about 220 lbs. There's hardly any braking,
so the rims don't wear out.
Cheers,
Carl Fogel
Dane Buson
> MykalCrooks wrote:
>
>> Built a pair with the Deep-Vs and Velocity hubs and laced each with 36
>> Lasers. Like 'em.
>
> Deep-V's are what you want if you want something
> that will shrug off an IED blast.
That's what I recommended for my brother who recently started cycling
seriously. He was about 280 lbs, but now has dropped down about 40 lbs.
The cycling worked in tandem with getting on better diabetes [1]
medication very well.
He built up a fixed gear wheelset with 36 spoke DB 14/15/14 Deep-V's and
(I think) IRO hubs. They've been a really good wheelset for him.
[1] Type II - Gila monster spit
http://www.sptimes.com/2005/04/30/Worldandnation/Diabetes_drug_stems_f.shtml
--
Dane Buson - sig...@unixbigots.org
Rincewind had generally been considered by his tutors to be a natural wizard
in the same way that fish are natural mountaineers. He probably would have
been thrown out of Unseen University anyway--he couldn't remember spells and
smoking made him feel ill.
-- Terry Pratchett, "The Light Fantastic"
doug....@gmail.com
carl...@comcast.net wrote:
> On Wed, 16 Aug 2006 21:20:15 -0700, jim beam <nos...@example.net>
> wrote:
> ...
> So on my front wheel, it looks as if the simple sideways area changes
> only about 5% between 32 and 24 spokes.
> ...
> This suggests that most posters would see a 3.7% drop in side-view
> front wheel+rim+spoke area if they dropped from 32 to 24 spokes (or
> gain 3.8% if they added 8 spokes to a 24-spoke wheel).
> ...
> Aerodynamics is a tricky matter, so raw side area may somehow be
> deceptive
> ...
> But the 8-spoke count reduction sounds like less than a 3% change.
> ...
> Maybe someone will have a link to wind tunnel tests, or an explanation
> of how the spokes have a much greater effect than would be expected.
Elementary, my dear Carl. You neglected two things:
1. What Jim is feeling is an absolute value, not a percentage. 3% of
something small is also small, but 3% of something big might be big.
Your statement that something is only 3% of the total without stating
the size of the total has no bearing whatsoever on whether or not it is
big enough for Jim to feel.
2. You assume the bike is standing still, and neglected the forward
motion and rotation of the wheel in your calculations. But they will
definately impact wind resistance. Think of it this way: if you walk
home in the rain, you take a certain amount of rain on top of your
head, and you walk into a bunch of drops, too, which land on the front
of you. If you run home in 1 second instead of 1 minute, less
raindrops will land on your head. But you will take more in the tummy.
As your speed approaches infinity, you will approach taking -all- the
raindrops between you and home on your forward-facing surfaces. Agree?
So, the rotating wheel, as it spins faster and faster, must approach
appearing as a solid disk to the wind coming from the side.
So, complete your analysis: What will be the actual change that Jim
experiences riding at 20mph in a 20mph crosswind from the change from
32 to 24 spokes?
Cheers,
Doug
carl...@comcast.net
Dear Doug,
Er, some parts of your analysis seem to have gaps.
You're saying that the spokes on a wheel whose tire is spinning at 20
mph appear to be solid to a side wind?
How does the side wind view the gaps between the spokes?
And only the outer edge of the tire turns 20 mph. The nipple end of
the spoke is turning more slowly, the midspan slower, and the elbow
end at about 3 mph.
How does the forward motion change the effect of a side wind? At the
bottom of the wheel, the vertical spoke is doing 0 mph forward,
relative to the ground.
Cheers,
Carl Fogel
jim beam
> In article <t7GdnYGGEadk-3nZ...@speakeasy.net>,
> jim beam <nos...@example.net> wrote:
>
>> and the eyelet thing is a complete red herring.
>
> Why? Eyelets/sockets distribute the load over a wider area and thus the
> rims are less likely to crack. All the rims that I've had crack had no
> eyelets/sockets.
>
double-eyeleted.
RonSonic
There isn't much gap if it is full of dirty air.
>And only the outer edge of the tire turns 20 mph. The nipple end of
>the spoke is turning more slowly, the midspan slower, and the elbow
>end at about 3 mph.
>
>How does the forward motion change the effect of a side wind? At the
>bottom of the wheel, the vertical spoke is doing 0 mph forward,
>relative to the ground.
It is indeed a very messy picture both conceptually and aerodynamically.
Ron
doug....@gmail.com
Dear Carl,
You are correct that the forward motion is not a factor, but the
rotation is. I did not say that a wheel spinning at 20mp will appear
as a solid disk, but it will have greater wind resistance from the side
than a wheel which is not spinning, and that is true. That fact will
increase the total number of which 3 or 5% is the difference you
claimed, and your analysis did not take that into account.
Back to the first point I raise, you still claim that because it's only
a 3 or 5% change, it's a surprise that Jim feels it, an argument which
has a huge gap :-)
Cheers,
Doug
carl...@comcast.net
Dear Doug,
I don't get the impression that Jim is saying that he feels only a
3-5% difference in how the side wind affects his 24 spoke versus his
32 spoke wheel. He wrote:
>> substantial benefit when riding in strong cross winds. i proved that to
^^^^^^^^^^^^^^^^^^^
>> myself again the other weekend. had a flat so quickly grabbed a spare
>> 32 spoke wheel and used that on my commute across the golden gate
>> bridge. it was startling how much difference the extra spoke count made
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> to cross-wind handling. next day, back to normal, 24 count front on the
>> mavic cosmos, much less wrestling required.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Nor am I sure that there should be only a 3-5% difference, since
aerodynamics is a tricky subject.
But the strength of the cross wind varies so much from day to day that
subjective impressions should be treated with skepticism. Dowsers will
assure you that the stick well-nigh twists out of their hands when
they locate water--but they've failed objective testing by James Randi
for decades. Randi, incidentally, makes a point of insisting that the
vast majority of dowsers appear to be sincere and honest.
Treat the spokes as an isolated and bizarre propellor, and 24 spokes
versus 32 sounds like a 25% difference, roughly an order of magnitude
more than the apparent side-view area. Maybe someone will explain how
the spokes could function as a propellor affected significantly by
side winds.
But if you pick up 8 spokes and wave them around, you'll notice far
too little wind drag to affect handling.
Another example of spoke wind-drag. Stand a bike upside-down and crank
a 36-spoke rear wheel up to about 30 mph with a few twists of one hand
and time how long it takes the wind drag to slow it to a halt.
When I tested the effect of slime in a tube, a plain tube and tire
with no slime took about 33 seconds on average to slow from 30 mph to
10 mph.
I'm willing to learn otherwise, but I suspect that daily variation,
expectation, and the buffeting of the side wind against the entire
bike and rider play a large role in the perceived difference.
To argue against that, a side wind does indeed increase forward drag
through rotating spokes, so curious things are going on:
http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/667bbc3488dc0ad4/66efd955895fdb16?lnk=st&q=carl+jobst+side+drag+wind&rnum=4#66efd955895fdb16
or http://tinyurl.com/zjyq3
Cheers,
Carl Fogel
jim beam
aerodynamics are not my thing so i'm not going to argue the math, but
you're welcome to come try these wheels some time. i don't like
sticking my neck out unless i'm pretty darned sure of something, and on
this, i'm pretty darned sure.
3rd...@willets.org
carl...@comcast.net wrote:
> Some crude theoretical calculations:
Wires have a long and disreputable history in the field of
aerodynamics. Almost the first thing that airplane designers changed
with the advent of wind tunnel drag testing was to remove external guy
wires, cross braces, and antennas.
If you look at figure 2 here, you'll notice a vast increase in drag
coefficient as reynolds number (a scaling factor, like diameter) is
reduced:
http://www.princeton.edu/~asmits/Bicycle_web/blunt.html
For instance, going from 10^0 to 10^-1 creates 10x less frontal area
(and 100x less cross section), but the CD goes from 10 to over 60,
giving less than a 40% reduction in drag.
> The winds on the Golden Gate vary more than that much every day. They
An example here is that new safety barrier on the inner side. IIRC
there was a long period of calculations to make sure that any new
structure wouldn't drastically increase the drag of the bridge, or
create a Tacoma Narrows Bridge situation.
carl...@comcast.net
Dear 3T,
Yes, and rotating wires moving forward through side winds are probably
even more disreputable.
Treated as a propellor with 24 or 32 badly-designed blades, the front
wheel could see a 25% reduction in--well, in something-or-other.
And the spokes are going to be 33% further apart, which should have
some effect on their turbulence.
(But some impressive hand-waving may be needed here to remove the rim,
tire, fork, handlebars, rider, and trailing part of the bicycle.)
So it's possible that Jim is indeed feeling exactly what he thinks, a
dramatic difference in handling in cross-winds, the physical result of
removing 8 out of 32 spokes.
But the winds themselves probably vary that much during a typical ride
across the bridge, so I'd love to see some wind tunnel or other
practical demonstration of the side-wind effect.
Cheers,
Carl Fogel
MykalCrooks
"Robin Hubert" <cv2...@hotmail.com> wrote in message
news:OJFEg.6659$Qf....@newsread2.news.pas.earthlink.net...
> D'ohBoy wrote:
> > Qui si parla Campagnolo wrote:
> >
> >> Sapim spokes are fine but hard to find in all lengths.
> >
> > thorusa.com. All lengths (or as many as one would need for a common
> > rim and hub combo).
> >
> > D'ohBoy
> >
>
>
>
> Robin Hubert
Sapim Laser 14/17G Double Butted Stainless Spokes, Bag/20 $12.95
Specs:
http://www.sapim.be/index.php?st=products&sub=spokes&category=3960&id=3386&detail=butted
mC
ste...@holyrood.ed.ac.uk
> I am looking to build a set of road wheels and am looking for
> suggestions for suitable rims. Of course, I would like them to be as
> light as possible without sacrificing the durability.
>
> While we all appreciate a litle nostalgia please limit your
> suggestions to rims that are still available.
I suggest the ST17 "Elegant" from DRC, or if you need a more solid rim,
try the ST19. However, for a 700C road wheel suitable for general use,
including fast road riding, dirt tracks and reasonable luggage
carrying, the ST17 is fine.
As an alternative, consider the Ambrosio "Nexus". It has the same ERD
as the Mavic MA2, which might allow you to use your old spokes. Both of
these rims are double eyeletted, available in 36 hole with a silver
finish.
I have built wheels with both of these rims, and the results have been
completely satisfactory.
s.
doug....@gmail.com
>
> I don't get the impression that Jim is saying that he feels only a
> 3-5% difference in how the side wind affects his 24 spoke versus his
> 32 spoke wheel.
Actually, he did not say that. You said was that he likely is not,
since it is only 3 to 5 % of something else, which I say makes no
sense, since you did not quantify the something else.
> But the strength of the cross wind varies so much from day to day that
> subjective impressions should be treated with skepticism.
Carl, this argument makes no sense at all -- you have not even so much
as inquired or otherwise determined what the wind speed was when Jim
conducted his test. Your argument could be applied to anyone claiming
to have felt any wind anywhere.
> Another example of spoke wind-drag. Stand a bike upside-down and crank
> a 36-spoke rear wheel up to about 30 mph with a few twists of one hand
> and time how long it takes the wind drag to slow it to a halt.
>
> When I tested the effect of slime in a tube, a plain tube and tire
> with no slime took about 33 seconds on average to slow from 30 mph to
> 10 mph.
Perhaps we are talking about apples and oranges here. Try this: Take
10 or 100 peas or marbles. Stand your bike upside-down or put the
wheel in a truing stand and, standing to the side of the wheel, toss
the peas one by one at the wheel. Count how many pass through the gaps
in the spokes. Now spin the wheel. While the wheel is still spinning,
toss the peas again. You will find that many more peas bounce back at
you after being struck by the spokes.
I have not done the calculations so I cannot say if the effect is
significant. But it is there and missing from your analysis.
> I'm willing to learn otherwise, but I suspect that daily variation,
> expectation, and the buffeting of the side wind against the entire
> bike and rider play a large role in the perceived difference.
That make no sense to me. The range of variation of sensitivity of
human feel constantly amaze me. Did you know that a few years back,
motocross motorcycles started using 19 inch rear wheels with lower
profile tires, whereas the had used 18 inch wheels for decades? The
reason? Because the lower profile tires handle better due to the
shorter sidewall. Now when I get out on a motocross track, I am lucky
to make it around without breaking any bones. I'll be goddammed if I
can feel anything at all smaller than a three inch rut. But some guys
can. In fact, I asked one buddy to try my bike,n and after he came
back in, he said "Nice bike. lotso power, great suspension. Great
bike. Oh by the way, your bars are bent." See what I mean? I had not
even noticed that the freakin handlebars were bent. He noticed it
instantly. And I have other bikes, so it wasn't a question of having
been used to it.
You, my friend, are like me. Relatively poor athletically, it is
almost beyond our comprehension that others can feel some tiny amount
of change of something which is so much smaller than the minimum change
we can detect. But, it is true. After ten years of riding road
bicycles, I STILL can't do a trackstand for more than 20 seconds, and I
am more than a little jealous of those with better balance than me.
But for you to say that Jim can't be feeling what he claims because the
winds through the GG vary daily is just you making excuses for - rather
than coming to terms with - your own poor abilities in that department.
Cheers,
Doug
carl...@comcast.net
[snip]
>You, my friend, are like me. Relatively poor athletically, it is
>almost beyond our comprehension that others can feel some tiny amount
>of change of something which is so much smaller than the minimum change
>we can detect.
[snip]
Dear Doug,
Jim did not say that the change is "some tiny amount" that only he can
detect.
I repeated it, but you snipped it, so here again is what Jim said:
> substantial benefit when riding in strong cross winds. i proved that to
^^^^^^^^^^^^^^^^^^^
> myself again the other weekend. had a flat so quickly grabbed a spare
> 32 spoke wheel and used that on my commute across the golden gate
> bridge. it was startling how much difference the extra spoke count made
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> to cross-wind handling. next day, back to normal, 24 count front on the
> mavic cosmos, much less wrestling required.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
My point is that when we expect a difference, we often feel it quite
sincerely, even if it's not there or something else is affecting
things.
In this case, the side winds on the Golden Gate bridge are notoriously
strong and variable.
Unless you ride two bicycles across the bridge at the same time, a
good deal of the apparent difference is likely to be different
expectations and different wind speeds.
A controlled test could eliminate the psychological expectations and
the physical variation of the wind.
Jim could be substantially right--there could be a large physical
effect.
He could also be partly right--there could be a physical effect, but
rather smaller than he thinks.
And he could be substantially mistaken--there must be a physical
effect, but it could turn out to be so small in testing that even he
would change his mind.
One of the hallmarks of double-blind, controlled testing is that
otherwise sensible people argue that there's no need for it.
We routinely see posts here on RBT about how this or that [fill in the
blank] is so much lighter that the poster can feel the awesome
difference.
The posts are made in good faith.
When the weight differences are plugged into a variety of speed
calculators, the improvement usually amounts to a couple of feet per
mile, a few hundredths of an mph, a couple of seconds per hour, and so
forth.
I'm willing to believe that Jim is mostly right (or partly right, or
mostly mistaken). What's the physics?
Cheers,
Carl Fogel
doug....@gmail.com
>
> Jim could be substantially right--there could be a large physical
> effect.
...
>
> I'm willing to believe that Jim is mostly right (or partly right, or
> mostly mistaken). What's the physics?
>
Dear Carl,
My mistake, then. I thought you were disputing Jim's claim when you
wrote
>Maybe someone will have a link to wind tunnel tests, or an explanation
>of how the spokes have a much greater effect than would be expected.
But, I guess, the only mystery is how he could possibly have held
incorrect expectations to begin with. :-)
For my own part, things surprise me all the time, so I'm not surprised
that he was surprised. :-)
Cheers,
Doug
carl...@comcast.net
Dear Doug,
More suprises:
http://www.zipp.com/Portals/0/Technology/Documents/A%20note%20on%20spoke%20count.pdf
Cheers,
Carl Fogel
Mike Jacoubowsky
>
> I have no objection to eyelets and sockets, and I expect that they do
> exactly what you say.
>
> But the plain 36-spoke rims (no-box-section, no sockets, no eyelets)
> on my 1998 Schwinn LeTour lasted around 35,000 miles at a rough guess
> with no cracks.
>
> They spun at about 20 mph on daily 15-mile rides that involve about 6
> miles of deteriorating bike path with cracked concrete slabs and
> endless tree root cracks in the asphalt. (A "Caution Trail Damage"
> sign is cheaper than repairs.)
We're talking about very heavy rims (approximately 550-600 grams?), combined
with wider tires (28c? 32?). Is it any wonder that they should last forever?
That option still exists today on some touring bikes and many hybrids.
The need for eyelets & sockets doesn't exist until you get into lighter
designs, with the exception that it's far easier to true a wheel when you
have a brass nipple against an eyelet or socket (made of brass or whatever,
but certainly not aluminum).
--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com
<carl...@comcast.net> wrote in message
news:uua9e2d5lb3pm9rl9...@4ax.com...
carl...@comcast.net
Dear Mike,
I'm far too lazy to unlace two rear wheels just to compare rim
weights, so instead . . .
dt swiss champion 2.0 straight spokes weigh 444g/64
http://www.dtswiss.com/index.asp?fuseaction=spokes.bikedetail&id=8
dt swiss competition 2.0x1.8x2.0 weigh 382g/64
http://www.dtswiss.com/index.asp?fuseaction=spokes.bikedetail&id=7
brass nipples weigh about ~1gram each
36-spoke straight 2mm Schwinn rear wheel
no box section, no eyelets or sockets
just a simple curved rim
24mm wide, 15mm deep
2lb 10.3 oz = 907.181 + 291.999 = 1199.180 grams
32-spoke 2.0x1.8x2.0 Performance Forte rear wheel
box section, eyelets, sockets
what I had handy
19mm wide, 20mm deep
2lb 7.4 oz = 907.181 +209.786 = 1116.967 grams
simple-rim 36-spoke wheel weighs 1199.180 grams
box-eyelet 32-spoke wheel weighs 1116.967 grams
--------
82.213 grams difference
roughly 294mm spokes on each wheel
294/264 x 444/64 = 7.726 grams / 2.0 straight spoke
294/264 x 382/64 = 6.647 grams / 2.0x1.8x2.0 spoke
So subtract ~4 grams for 32 versus 36 spokes
Subtract ~4 more grams for 32 versus 36 nipples
So if the hubs and freewheels are the same . . .
My simple no-box section Schwinn rim weighs 74 grams more than my
Forte box-section rim with eyelets and sockets, but is also 25% wider
and 25% shallower. This doesn't sound like 550-600 gram rim.
Tires were 700x26 at ~125 psi, bike and rider were ~220 lbs. The
Schwinn rim seems fine after about 35,000 miles of daily 15 mile rides
with about 6 miles of badly deteriorated bicycle path
Cheers,
Carl Fogel
Booker C. Bense
In article <1155869318.1...@b28g2000cwb.googlegroups.com>,
_ It's also pointless unless Jim is using exactly the same rims
and tires. My guess is that the difference he notices has way
more to do with rim depth and shape than the number of spokes.
_ Booker C. Bense
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carl...@comcast.net
<bbense+rec.bicycles.misc.r...@telemark.slac.stanford.edu>
wrote:
>-----BEGIN PGP SIGNED MESSAGE-----
>
>In article <1155869318.1...@b28g2000cwb.googlegroups.com>,
> <doug....@gmail.com> wrote:
>>carl...@comcast.net wrote:
>>> On 17 Aug 2006 16:16:09 -0700, doug....@gmail.com wrote:
>>>
>>
>>Back to the first point I raise, you still claim that because it's only
>>a 3 or 5% change, it's a surprise that Jim feels it, an argument which
>>has a huge gap :-)
>>
>
>_ It's also pointless unless Jim is using exactly the same rims
>and tires. My guess is that the difference he notices has way
>more to do with rim depth and shape than the number of spokes.
>
>_ Booker C. Bense
Dear Booker,
To be fair, think of the sidewind as blowing through a fan whose 28 or
32 blades (spokes) are connected by a thin ring (rim).
The fan is weird, since it spins not like a stationary fan, but like a
bike wheel, with the top blade (spoke) doing 40 mph relative to
ground, and the bottom blade (spoke) doing 0 mph relative to ground.
A slightly wider or thinner ring (different rims) might not make much
difference to this fan in a side wind.
But if almost all the side wind action takes place in the fan blades
(spokes), then reducing the number of blades from 32 to 24 suggests a
25% change in side wind effect.
If there really is a 25% difference, then Jim is feeling exactly
what's happening, a noticeable improvement in the way the wheel
handles the gust side winds on the Golden Gate.
If the difference is actuallly much smaller, then Jim could be feeling
just the normal variation in the gusty winds on the bridge, coupled
with the expectation of improvement.
I'm still puzzled and can't see any easy way to test it, short of a
wind tunnel.
Here's a somewhat similar situation:
http://www.rouesartisanales.com/6-categorie-94458.html#english
In the test, the same bicycle and rider rolled down a 3.25% grade (the
degree sign is a misprint) twenty times, ten with ordinary wheel
bearings, ten with ceramic bearings, and found that the ceramic
bearing runs were 3.8% faster over a roughly 55-second, 500 meter
course, 47.3 kmh top speed versus 45.4 kmh.
Before I spent hundreds of dollars on ceramic wheel bearings, I'd want
to see a drum spin-down test.
If the wind on the half-kilometer hill changed 1.9 kmh after the first
ten runs, which would take half an hour to do, then that wind change
would account for the difference--and a 1.2 mph wind speed difference
is pretty much undetectable.
Then there's the double-blind problem. How did the bicycle start
rolling? A tiny difference in the initial push makes a surprising
difference in coasting tests. And how closely did the rider duplicate
his tuck from the start to the finish, knowing that he was looking for
improvements on the ceramic bearings?
Maybe I was wrong about ceramic bearings, too, but when wind drag and
rider perceptions are involved, it takes a lot to show a difference.
Cheers,
Carl Fogel
doug....@gmail.com
> On Mon, 21 Aug 2006 21:24:38 +0000 (UTC), Booker C. Bense
> <bbense+rec.bicycles.misc.r...@telemark.slac.stanford.edu>
> wrote:
>
> >-----BEGIN PGP SIGNED MESSAGE-----
> >
> >In article <1155869318.1...@b28g2000cwb.googlegroups.com>,
> > <doug....@gmail.com> wrote:
> >>carl...@comcast.net wrote:
> >>> On 17 Aug 2006 16:16:09 -0700, doug....@gmail.com wrote:
> >>>
> >>
> >>Back to the first point I raise, you still claim that because it's only
> >>a 3 or 5% change, it's a surprise that Jim feels it, an argument which
> >>has a huge gap :-)
> >>
> >
> >_ It's also pointless unless Jim is using exactly the same rims
> >and tires. My guess is that the difference he notices has way
> >more to do with rim depth and shape than the number of spokes.
> >
> >_ Booker C. Bense
Dear Carl,
> A slightly wider or thinner ring (different rims) might not make much
> difference to this fan in a side wind.
What are your numbers behind this statement?
Doug
carl...@comcast.net
>carl...@comcast.net wrote:
>> On Mon, 21 Aug 2006 21:24:38 +0000 (UTC), Booker C. Bense
>> <bbense+rec.bicycles.misc.r...@telemark.slac.stanford.edu>
>> wrote:
>>
>> >-----BEGIN PGP SIGNED MESSAGE-----
>> >
>> >In article <1155869318.1...@b28g2000cwb.googlegroups.com>,
>> > <doug....@gmail.com> wrote:
>> >>carl...@comcast.net wrote:
>> >>> On 17 Aug 2006 16:16:09 -0700, doug....@gmail.com wrote:
>> >>>
>> >>
>> >>Back to the first point I raise, you still claim that because it's only
>> >>a 3 or 5% change, it's a surprise that Jim feels it, an argument which
>> >>has a huge gap :-)
>> >>
>> >
>> >_ It's also pointless unless Jim is using exactly the same rims
>> >and tires. My guess is that the difference he notices has way
>> >more to do with rim depth and shape than the number of spokes.
>> >
>> >_ Booker C. Bense
>
>Dear Carl,
>
>> A slightly wider or thinner ring (different rims) might not make much
>> difference to this fan in a side wind.
>
>What are your numbers behind this statement?
>
>Doug
Dear Doug,
A ring/rim has the effectively same side resistance, whether it's
spinning or not.
(Yes, there's some drag on the smooth surface, but it's trivial in
this case. This is why a disk wheel reduces drag so much over exposed
spokes.)
A blade's resistance increases as it spins.
(How well thin round spokes function as blades is the question.)
If you blow hard through a handy computer fan in the right direction,
you'll notice the blades slowing. Blow on a spinning ring and not much
will happen.
The bicycle wheel, it's worth repeating, complicates things by not
really functioning like any normal propellor or fan.
When a bicycle moves at 20 mph, the top end of the top "blade" is
doing about 40 mph forward and its bottom end is doing about 20 mph.
Meanwhile, the bottom of the bottom "blade" is doing about 0 mph,
while its upper end is doing about 20 mph forward.
The entire blade pointing dead forward is moving 20 mph forward, with
its far end moving 20 mph downward, but heavily sheltered by the rim
and tire.
The entire blade pointing dead backward is moving 20 mph forward, with
its far end moving about 20 mph upward through a turbulent mess.
Plus, the blades are all sticking out at ang angle from the plane of
the rim.
Cheers,
Carl Fogel
doug....@gmail.com
Yes, Dear Carl, but... Jim is feeling the resistance that the wheel
would have even were it not spinning. Which is five times the
resistance that comes from the spokes, according to your own
calculations of surface area. Added to that, he is also feeling any
increases or differences due to forward or rotational speed.
You've come full circle in your arguments - you yourself counted that
79,800 mm^2 in your argument that the change is only 3-5%.
Since the area of the rim+tire is approx 4 times that of the spokes,
Jim will surely find it (a change in tire or rim size) affecting how
much harder it is to control in a crosswind.
Remember, it was a change of wheel resulted in whatever that Jim felt,
not a change in bike speed.
Cheers,
Doug
doug....@gmail.com
> Dear Doug,
>
> More suprises:
>
> http://www.zipp.com/Portals/0/Technology/Documents/A%20note%20on%20spoke%20count.pdf
>
> Cheers,
>
> Carl Fogel
Dear Carl,
I don't see any surprises there. Which part did you not expect? Also,
it seems to be discussing wattage to spin - what does it have to do
with crosswind resistance?
Doug
carl...@comcast.net
Doug,
Jim feels a strong difference at roughly the same speed between two
front wheels in gusty side winds.
If the effect of the side wind is just a matter of surface area, then
the feeling is likely to an illusion--expection coupled with highly
variable winds. After all the difference in surface area appears to be
only 3% to 5%.
But if the effect of the side wind is more a matter of the number of
blades whirling in the wind like a fan, then the rim surface becomes
trivial and the 25% reduction in the number of blades suggests that
Jim is feeling a clear effect.
Viewed from the side, whirling fan blades are obviously different than
a smooth, spinning rim surface, so the question is whether thin spokes
in the peculiar turbulence of the wheel generate enough force to have
a significant effect.
The blades on the fan in your computer have an effect, but not enough
to affect a rider's balance. The "blades" in a wheel are much thinner,
are shaped differently, sweep a much larger area, and are very
peculiar in that they are rolling instead of stationary.
Do they have a big enough aerodynamic effect to explain what Jim
feels? I don't know. But those are the two possible explanations that
I can see.
If you find a wind tunnel test for gusty wind effects, let us know.
Cheers,
Carl Fogel
carl...@comcast.net
Dear Doug,
There's a nice graph on page 3.
What happens at 30 mph to the drag force in pounds as the angle of the
wind changes from 0 to 20 degrees?
What happens after that, as the wind angle changes from 20 to 30
degrees?
Those two contradictory trends surprised me.
Given those two trends, what would you predict would happen as the
wind angle changed from 30 to 90 degrees?
The drag is measured straight back, but obviously the wind is not
dragging straight back. To produce the kind of increased straight-back
drag noticeable at a 30 degree angle, how much side drag do you think
is necessary?
If anything, it seems to support Jim's feeling that the side winds
affect his 24 count wheel much more than his 32 spoke wheel. The 32
spoke wheel in that graph produces about 1.05 pounds of straight-back
drag, versus about 0.55 pounds of straight-back drag for the 24-spoke
wheel.
Given the weird nature of a rolling fan versus a stationary fan, the
side drag that must also be increasing is probably unbalanced.
Thanks for making me look more closely at some of the surprising
things in that article.
Cheers,
Carl Fogel
RonSonic
Very simply, because that's all I can do, for all practical purposes the area of
an object includes the mass of roiled air attached to it. If the spoke has less
drag going forward it will have a much smaller profile to the side winds. The
crosswind "sees" the wheel components as a single piece with the wad of dirty
air in and around it.
Need more, ask an aerodynamicist and be prepared to take on a new study.
Ron
carl...@comcast.net
Dear Ron,
A solid disk front is universally agreed to be a bad idea in a
crosswind.
So the question still remains: does a 32-spoke wheel look
significantly more turbulent to a gusty crosswind than a 24-spoke
wheel as Jim rides across the Golden Gate?
That is, how much dirtier is the wad of air whipped up inside a 32
spoke wheel, versus a 24-spoke wheel?
Cheers,
Carl Fogel
Joe Riel
>>> More suprises:
>>>
>>> http://www.zipp.com/Portals/0/Technology/Documents/A%20note%20on%20spoke%20count.pdf
>>>
>>> Cheers,
>>>
>>> Carl Fogel
>>
>>Dear Carl,
>>
>>I don't see any surprises there. Which part did you not expect? Also,
>>it seems to be discussing wattage to spin - what does it have to do
>>with crosswind resistance?
>>
>>Doug
>
> Dear Doug,
>
> There's a nice graph on page 3.
I'm not sure what to make of the graph, considering the text:
"Because of this, we accept the margin of uncertainty to be 0.5 pounds
per data point." Maybe that is supposed to be 0.05 pounds, the total
drag being less than 0.5 pound force for almost all the data. Even
so, the text indicates that the difference between the plots is within
the margin of uncertainty of the measurement (see end of page 2).
Joe
doug....@gmail.com
>
> There's a nice graph on page 3.
>
> What happens at 30 mph to the drag force in pounds as the angle of the
> wind changes from 0 to 20 degrees?
>
> What happens after that, as the wind angle changes from 20 to 30
> degrees?
>
> Those two contradictory trends surprised me.
Dear Carl,
Well, if the wind was all coming from the front, then it would be
hindering the spokes moving forward, but helping the spokes which are
on the bottom half of the rotatation. So it will tend to slow down
the spokes in the top half of the wheel, but not speed up the spokes in
the bottom half, since they are not free to move backwards, being fixed
to the road. So it hinders more than it helps.
A wind coming from the side, however, cares not about the direction of
the movement of the spokes in the inline plane, and helps or hinders
all 36 the same. Apparently it hinders. Since more spokes are visible
from the side then from the front, there are more spokes affected by
wind from 90 than from 0 degrees.
As the angle of attack of the wind changes from 0 to 20 degrees, the
effect of hindrance on the spokes in the top half of the wheel drops
off, and the graph dips. As the angle of attack increases past 20, the
effect it has on all spokes increases, and the graph rises.
Cheers,
Doug
carl...@comcast.net
Dear Joe,
Yes, that's what the text says.
The explanation given is this:
"Since these particular runs were all taken over a 3 day period, there
could be other factors as well, such as temperature and humidity
effects. Because of this, we accept the margin of uncertainty to be
0.5 [1] pounds per data point."
[1] Yes, that looks like a typo for 0.05
But while the graph points for the individual spoke counts might vary
due to humidity and temperature differences during 3 days of testing,
the averaged data for each wheel followed the same curious pattern.
Drag dropped gently from 0.45~0.40 to 0.33~0.28 as the wind angle
increased to 15-20 degrees.
Then drag rose sharply toward 0.51 to 0.62 as the angle increased.
As far as I can tell, this is straight-back drag. Since the wind is
coming from an increasing angle, there should be a side "drag", too.
If the apparent straight-back drag rises 50% on a wheel at 30 mph just
because the wind is angling from 20 degrees to 30 degrees, then the
side forces must be interesting.
And notice how the 28-spoke stands out above the others--it could be
just weird luck and variation, but it suggests that a 32-spoke would
be sticking up even farther.
Go down to the next graph, where the deep 404 wheels are graphed
against 2 non-aero wheels with 28 and 32 spokes. The 28 spoke may show
a faint dip before rising, but the 32 spoke shows a steady climb. And
both non-aero wheels have much more drag.
In fact, the 28 and 32 spoke non-aero wheels stay about half a pound
of straight-back drag apart at all angles at 30 mph.
So this stuff strikes me as suggesting (not proving) that Jim may well
be right.
To take the other side of the question, however, the four 404 deep rim
wheels showed very little straight-drag variation in that second graph
(whether they had 16, 20, 24, or 28 spokes) as the wind angle
increased. That is, the drag changed in the same odd pattern for 404
rims regardless of the spoke pattern, but the number of spokes seems
to have little effect according to wind angle for the 404's.
It's a beastly tricky question.
Cheers,
Carl Fogel
carl...@comcast.net
Dear Doug,
Could be.
But look at the next graph down for the same 30 mph wind at angles
increasing to 30 degrees.
The 404 deep aero rim wheel shows the dip with 16, 20, 24, 0r 28
spokes.
A non-aero rim with 28 shows what might be a faint dip.
The non-aero rim with 32 spokes shows no dip.
Beastly tricky and surprising, like lots of aerodynamics.
A deeper rim is associated with an odd dip in straight-back drag as
the wind angle increases at 30 mph. The dip disappears with more
spokes on shallower rims. I'm baffled as to what the side forces must
be, but it seems reasonable to deduce that they're present.
Cheers,
Carl Fogel
Donga
daveornee wrote:
> Velocity Aerohead with Aerohead OC in rear makes a good combination for
> someone your weight.
I have dented two Aerohead OC on the drive side, where the rim is near
vertical and close to the edge of the tire. I'm guessing I hit a
'cateye' on the edge. Perhaps I didn't have my tires pumped up enough?
I don't think so - I pump my tires before most rides to 120lb, tho'
this was with an old Silca that might not be too accurate. Has anyone
else had this experience with the OC rims? I won't use them any more.
Donga
Ron Ruff
carl...@comcast.net wrote:
> A deeper rim is associated with an odd dip in straight-back drag as
> the wind angle increases at 30 mph. The dip disappears with more
> spokes on shallower rims. I'm baffled as to what the side forces must
> be, but it seems reasonable to deduce that they're present.
They are shown here... scroll down:
http://www.zipp.com/Default.aspx?tabid=103
The wheel with the most spokes... the 32 hole GL330... has the least
side force. So, Jim's contention does not square with Zipp's data. It
appears that the spokes contribute very little to the side force
compared to the rim.
RonSonic
Empirically, enough.
Is it just the spoke count? Apparently not.
Ron
jim beam
one high spoke count, the other low, the comparison for /spokes only/ is
direct and easy.
carl...@comcast.net
wrote:
Dear Ron,
Aha!
You've found exactly the kind of stuff that I was hoping to see!
Your link appears to expand on the data from the other link:
http://wordsworth.classicauthors.net/PoemsOfWilliamWordsworth/PoemsOfWilliamWordsworth41.html
Oops! I got excited and forgot that my cut-and-paste clipboard had an
address from an unrelated email exchange about psycho killer raccoons,
Hemingway, Senator Kennedy, Marlowe, and Wordsworth.
But actually the line "The winds that will be howling at all hours" is
appropriate because--
Er, never mind. Let's start again.
Here's the link to the earlier spoke drag pdf:
http://www.zipp.com/Portals/0/Technology/Documents/A%20note%20on%20spoke%20count.pdf
or http://tinyurl.com/qzxta
Here's your nice link to the side force graph and article, which seems
to expand on the same wind tunnel testing:
http://www.zipp.com/Default.aspx?tabid=103
The side-force graph near the bottom shows that an older GL330 32
spoke rim's side force rises to just under 2 pounds with a 30 mph wind
angle of 30 degrees.
But an A1 (or AL) rim with only 20 bladed spokes suffers a side force
that's noticeably larger, roughly 30% more.
And the average side force for the 404 wheel with 16, 20, 24, and 28
spokes from the other link is about 4 pounds, about twice as much as
it is for the 32 spoke wheel.
(A graph showing the side forces for the 16, 20, 24, and 28 spoke
versions of the 404 would be wonderful, but alas we only get the
average.)
I have to agree with you that the rim differences seem to affect the
side force far more than the number of spokes. The deeper 404 rim with
an average of 22 spokes has twice as much side drag as the shallow 32
spoke rim.
Thanks for finding that side-force graph.
Cheers,
Carl Fogel
carl...@comcast.net
<rons...@tampabay.rr.com> wrote:
Dear RonSonic
Hard to keep the Ron's straight here.
Elsewhere in this thread, Ron Ruff found a very nice link to a side
force article with a graph well down that suggests that spoke count is
much less important than rim differences:
http://groups.google.com/group/rec.bicycles.tech/msg/c01ecef22aeb16cb
The link above to my post includes Ron Ruff's post, link, and the
related link.
Cheers,
Carl Fogel
Chris Neary
>http://www.zipp.com/Default.aspx?tabid=103
>
>The wheel with the most spokes... the 32 hole GL330... has the least
>side force. So, Jim's contention does not square with Zipp's data. It
>appears that the spokes contribute very little to the side force
>compared to the rim.
This squares with personal experience on our tandem:
Wheelset #1 used 40 spokes with a Mavic box section rim.
Wheelset #2 uses 24 & 28 spokes with an aero rim profile (Rolf Prima Tandem,
for those who care)
Wheelset #2 is significantly less stable in crosswinds @ speed when I'm
using the aerobars.
YMMV
Chris Neary
diabl...@tcsn.net
Chris & Tracey
1999 Co-Motion Speedster
Ron Ruff
jim beam wrote:
> that may well be the case, but if i have two wheels, same rim profile,
> one high spoke count, the other low, the comparison for /spokes only/ is
> direct and easy.
I was just thinking... side force is one parameter, but wouldn't it be
more important to know where it is relative to the steering axis? Seems
like that is the thing that would upset your handling. If the side
force is equal fore and aft of the steering axis it wouldn't turn the
wheel, but if the center of pressure was towards the front it sure
would!
So the question is... what configuration is most likely to give you the
biggest *unbalanced* side force... or net moment on the steering axis?
I'm still thinking the spokes won't matter much... but it is much too
late to think...
jim beam
on the same bike/fork. on the spoke count is different between wheels.
dvt
> jim beam wrote:
>> that may well be the case, but if i have two wheels, same rim profile,
>> one high spoke count, the other low, the comparison for /spokes only/ is
>> direct and easy.
>
> I was just thinking... side force is one parameter, but wouldn't it be
> more important to know where it is relative to the steering axis?
Yes... in other words, what is the steering *torque* induced by the
wind? I don't know how to estimate this.
--
Dave
dvt at psu dot edu
Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)
carl...@comcast.net
>Ron Ruff wrote:
>> jim beam wrote:
>>> that may well be the case, but if i have two wheels, same rim profile,
>>> one high spoke count, the other low, the comparison for /spokes only/ is
>>> direct and easy.
>>
>> I was just thinking... side force is one parameter, but wouldn't it be
>> more important to know where it is relative to the steering axis?
>
>Yes... in other words, what is the steering *torque* induced by the
>wind? I don't know how to estimate this.
Dear Dave,
It's going to be tricky, even when idealized.
Let's say the wheel is going 20 mph forward.
A sudden gust of wind at 20 mph hits it at 90 degrees.
A flare of turbulence should erupt from the far side of the wheel,
trailing backward sharply.
Some of the effect will be from torque trying to turn the wheel.
Some of the effect will be from the whole wheel being tilted over
sideways without turning--keep the wheel perfectly straight, tilt the
bike slightly, and the rider must either turn or topple.
At the moment the wind hits the wheel, the bottom of the bottom spoke
is motionless relative to the road, while the top of the top spoke is
doing 40 mph to one side.
The ends of the horizontal spokes are going forward at 20 mph and also
going either up or down at 20 mph.
Everything behind the leading point of the front tire is already is a
turbulent mess.
The mess in roughly the upper rear quarter of the wheel is complicated
by the turbulence off both fork legs.
The slower-moving hub ends of the dished spokes stick out past the
plane of the tire, while the faster-moving rim ends are tucked in.
At a certain angle, two of the four roughly horizontal spokes will be
pointing straight into the apparent wind, one leading, one trailing.
And so on . . . even a wind tunnel test will give only the side force
under fairly steady conditions, not what happens when the wind gusts
back and forth erratically with real-life abruptness.
But it's a fascinating question.
Cheers,
Carl Fogel
doug....@gmail.com
carl...@comcast.net wrote:
> On Thu, 24 Aug 2006 13:10:29 -0400, dvt <dvt+u...@psu.edu> wrote:
>
> >Ron Ruff wrote:
> >> jim beam wrote:
> >>> that may well be the case, but if i have two wheels, same rim profile,
> >>> one high spoke count, the other low, the comparison for /spokes only/ is
> >>> direct and easy.
> >>
> >> I was just thinking... side force is one parameter, but wouldn't it be
> >> more important to know where it is relative to the steering axis?
> >
> >Yes... in other words, what is the steering *torque* induced by the
> >wind? I don't know how to estimate this.
>
> Dear Dave,
Dear Carl,
> Let's say the wheel is going 20 mph forward.
OK
> A sudden gust of wind at 20 mph hits it at 90 degrees.
OK
> A flare of turbulence should erupt from the far side of the wheel,
> trailing backward sharply.
OK
> Some of the effect will be from torque trying to turn the wheel.
OK
> Some of the effect will be from the whole wheel being tilted over
> sideways without turning--keep the wheel perfectly straight, tilt the
> bike slightly, and the rider must either turn or topple.
OK
> At the moment the wind hits the wheel, the bottom of the bottom spoke
> is motionless relative to the road, while the top of the top spoke is
> doing 40 mph to one side.
To the side? Not forward?
> The ends of the horizontal spokes are going forward at 20 mph and also
> going either up or down at 20 mph.
Are you sure? Forward at 20, yes, but up and down too?
Cheers,
Doug
carl...@comcast.net
Dear Doug,
Let's leave the side wind for further down.
All figures are slightly high because the spokes don't reach the edge
of the tire--20 mph for the spokes is 20 mph minus a little bit.
Everything on the bicycle is moving forward relative to the ground at
20 mph.
The wheel is also rotating at enough rpm that its outer edge is doing
20 mph.
So the top of the top spoke is going 20 + 20 = 40 mph forward.
The bottom of the bottom spoke is going 20-20 = 0 mph forward.
The entire front horizontal spoke is going 20 mph forward, while its
rim end is also moving 20 mph straight down.
The entire rear horizontal spoke is also going 20 mph forward, but its
rim end is moving 20 mph straight up.
Okay, now look at the wheel from the side, the wind's point of view.
The bottom spoke's bottom end is motionless when viewed from the side,
since it's going 0 mph forward relative to the ground.
The top spoke's top end is doing 40 mph forward (to one side as viewed
by the side wind.)
The two horizontal spokes are moving 20 mph forward (to one side as
viewed by the side wind) and their rim ends are also moving either up
or down at 20 mph.
Of course, the closer you get to the hub, the more all spokes are
moving mostly forward at around 20 mph. The center of the axle is the
only thing that actually moves straight forward at 20 mph.
This is why I keep adding that if the spokes act as propellors, then
it's a very weird propellor. The face of a normal fan is stationary
relative to the wind and we can forget everything above--all the
blades are moving at the same speed relative to the wind that they
generate.
Bad as this explanation is, it could be worse, but I'll spare everyone
attempts at drawing pictures. Maybe someone knows of a nice set of
illustrations of spoke speeds relative to the ground.
Cheers,
Carl Fogel
doug....@gmail.com
> >> going either up or down at 20 mph.
> >
> >Are you sure? Forward at 20, yes, but up and down too?
> >
> >Cheers,
> >Doug
>
> Dear Doug,
Dear Carl,
> Let's leave the side wind for further down.
OK
> All figures are slightly high because the spokes don't reach the edge
> of the tire--20 mph for the spokes is 20 mph minus a little bit.
Okey Doke
> Everything on the bicycle is moving forward relative to the ground at
> 20 mph.
Disagree. The wheel, where it touches the ground, is not moving
forward at all.
> The wheel is also rotating at enough rpm that its outer edge is doing
> 20 mph.
At two points [on the outer edge] but not at the rest of it.
> So the top of the top spoke is going 20 + 20 = 40 mph forward.
>
> The bottom of the bottom spoke is going 20-20 = 0 mph forward.
The bottom of the bottom spoke is not 0-0, not 20-20.
> The entire front horizontal spoke is going 20 mph forward, while its
> rim end is also moving 20 mph straight down.
Really? I would have said that it is moving approximately 25mph down.
Remember that during one rotation of the wheel, any point on the
circumference moves forward by one circumference, so, 2piR, but up and
down by two diameters, so, 4R. The vertical distance travelled is less
than the horizontal distance, it's 2/pi (0.6366), times it, so it looks
doubtful that the number we are looking for is going to come out to 20
or 40.
The ratio of horizontal movement to vertical movement is 2piR to 4R, or
pi to 2. If you multiply 20 miles times pi/2, you get approximately
12.75. So a point on the circumference has to average 12.75 mph
vertically while averaging 20mph horizontally.
Furthermore, the point on the circumference speeds up and slows down
twice per rotation, as opposed to once in the forward direction. So it
has to accelerate to 25.5mph and then decelerate to zero once on the
way up and then do it all again on the way down.
Correct?
carl...@comcast.net
Dear Doug,
I think that the difference is that you may be thinking of averaging,
curves, and angles, while I'm talking about simpler straight forward
and straight up rates of motion.
That is, you may be thinking about speed along a curved descent or
ascent, while I'm simply treating it as rate of climb and pure forward
progress
To simplify the terms, treat the ends of the spokes as a metal rim
with no tire.
If the axle moves forward at 20 mph, then the rim must spin at 20 mph.
The exact top of the rim is always doing 20 + 20 = 40 mph straight
forward.
The exact bottom of the rim is always doing 20 - 20 = 0 mph in every
direction relative to the ground.
(If the exact bottom of the rim did anything except 0 mph relative to
the ground, it would leave a skid mark.)
The exact horizontal forward part of the rim is always moving 20 mph
straight down at the same instant that it's doing 20 mph forward.
Same for the exact horizontal rearward part of the rim, except that it
moves straight up at 20 mph.
Viewed from the side, a pinpoint light on the rim proceeds in an
endless series of half-circle leaps, slowing to 0 mph forward speed
each time it "bounces" off the ground, accelerating to 40 mph forward
speed at the top of the half-circle, and slowing back down to 0 mph.
With a rim moving forward and rotating at 20 mph, the maxium straight
upward or straight downward speed is obviously limited to 20 mph,
since the axle does not move up or down.
Cheers,
Carl Fogel
doug....@gmail.com
Nope, I'm talking about straight-line motion.
> If the axle moves forward at 20 mph, then the rim must spin at 20 mph.
Not true. Each and every point on the rim is constantly changing
speed, in every direction, and in total.
> The exact top of the rim is always doing 20 + 20 = 40 mph straight
> forward.
Correct.
> The exact bottom of the rim is always doing 20 - 20 = 0 mph in every
> direction relative to the ground.
It is doing 0, but it's not 20-20. It's 0-0.
> (If the exact bottom of the rim did anything except 0 mph relative to
> the ground, it would leave a skid mark.)
Correct.
> The exact horizontal forward part of the rim is always moving 20 mph
> straight down at the same instant that it's doing 20 mph forward.
Incorrect. It it moving 25.5mph straight down.
> Same for the exact horizontal rearward part of the rim, except that it
> moves straight up at 20 mph.
Incorrect again. It is moving 25.5mph straight up.
> Viewed from the side, a pinpoint light on the rim proceeds in an
> endless series of half-circle leaps, slowing to 0 mph forward speed
> each time it "bounces" off the ground, accelerating to 40 mph forward
> speed at the top of the half-circle, and slowing back down to 0 mph.
Correct. But that movement is not symmetric. It involves more forward
movement that up-and-down movement. Therefore the total distance
travelled is not the same in the two directions.
> With a rim moving forward and rotating at 20 mph, the maxium straight
> upward or straight downward speed is obviously limited to 20 mph,
> since the axle does not move up or down.
Faulty logic. Do the math, Carl. Each point on the [circumference of
the] rim moves 20mph in the forward direction and 12.75mph in the
vertical direction when the bike moves 20mph. Therefore each point
must average 20mph forward and 12.75mph upanddown. Furthermore, being
a circle, changes in sine and cosine are symmetric, so the increases
and decreases in horizontal and vertical speeds are mirror images.
Therefore the wheel must be going twice the average, or 40mph at the
top of its run. And it must be going twice the average, or 25.5mph,
when at the midpoint of its upstroke, and again at the midpoint of its
downstroke.
The error in your logic is in your claim that any point on the rim is
moving at 20mph just because the wheel is rotating, and the bike is.
But you can arrive at the correct answer without thinking about that,
just do the math of the vertical movement and divide by time.
Do you agree that while the forward movement of one rotation is 2piR,
the vertical movement is 4R?
Cheers,
Doug
carl...@comcast.net
Dear Doug,
Put the bike upside down on a railroad flatcar.
Have the flatcar do 20 mph forward.
The wheel does not rotate.
Every point on the wheel moves forward, just like the bicycle frame at
20 mph.
Now spin the wheel so that the rim/tire/simplified-spoke-ends are
doing 20 mph.
***
Axle = 20 mph forward relative to ground.
Top of rim = 20 mph forward relative to axle.
Axle = 20 mph forward relative to ground.
20 + 20 = 40 mph for top of rim relative to ground.
***
Axle = 20 mph forward relative to ground.
Bottom of rim = 20 mph backward relative to axle.
20 - 20 = 0 mph for bottom of rim relative to ground.
***
Now view the wheel from dead ahead in the dark.
It doesn't matter whether the axle is moving toward you, standing
still, or moving away from you.
A light on the rim will appear to bounce back and forth either way
from the center of the tire, both up and down.
It will slow to 0 mph up/down at the top and bottom of the tire.
It will accelerate to 20 mph either straight up or straight down in
the exact middle of its travel, when it is in line with your eye and
the axle--that's the definition of a rim spinning at 20 mph.
***
Draw a circle with 4 tangent 2-inch lines at the top, bottom, and both
sides.
If the circle spins around a stationary axle at 20 mph, then each
2-inch tangent line is a 20 mph velocity, speed plus direction.
To make the axle move forward at 20 mph, add four horizontal 2-inch
lines at the appropriate spots.
The two lines cancel to 0 mph at the bottom of the circle.
The two lines add to each other for 40 mph at the top of the circle.
The horizontal lines do not affect the vertical travel, which remains
20 mph, either up or down.
Cheers,
Carl Fogel
doug....@gmail.com
>
> Put the bike upside down on a railroad flatcar.
>
> Have the flatcar do 20 mph forward.
>
> The wheel does not rotate.
>
> Every point on the wheel moves forward, just like the bicycle frame at
> 20 mph.
Dear Carl,
Okay.
> Axle = 20 mph forward relative to ground.
> Top of rim = 20 mph forward relative to axle.
> Axle = 20 mph forward relative to ground.
> 20 + 20 = 40 mph for top of rim relative to ground.
Okay.
> Now view the wheel from dead ahead in the dark.
> It doesn't matter whether the axle is moving toward you, standing
> still, or moving away from you.
> A light on the rim will appear to bounce back and forth either way
> from the center of the tire, both up and down.
> It will slow to 0 mph up/down at the top and bottom of the tire.
>
> It will accelerate to 20 mph either straight up or straight down in
> the exact middle of its travel, when it is in line with your eye and
> the axle--that's the definition of a rim spinning at 20 mph.
Wrong. It will accelerate to 25.5mph both straight up and straight
down. Furthermore, there is no definition of a rim spinning at 20mph.
Rims spin, like everything else, at RPMs, not MPHs. It is undefined to
speak of a rim spinning at an MPH. This is critical.
> If the circle spins around a stationary axle at 20 mph, then each
> 2-inch tangent line is a 20 mph velocity, speed plus direction.
Carl, a circle DOES NOT "spin at 20mph". The If you -must- speak of
the circle as a whole, then the circle has forward speed of 20, and a
vertical speed of 0. The numbers 20 and 40 come into play when you
look at the forward speeds of various points on the rim. It really has
nothing to do with the vertical speeds at all - with the exception of
the relationship pi over 2.
You keep trying to claim that anything that is true about the forward
movement is also true of the vertical movement, but that's simply not
true.
Carl, you agree that a point on the rim will accelerate and decelerate
twice per rotation. Do you also agree that the distance travelled per
rotation is 2piR forward, 0 backwards, 2R up, and 2R down?
Cheers,
Doug
carl...@comcast.net
Dear Doug,
I think that you are confused about rpm and speed.
A point on the edge of the rim travels along a circular path at 20 mph
when your bicycle goes 20 mph,
That's how your bicycle odometer and speedometer work. RPM alone is
useless. You must also have the circumference to figure out the speed.
I also think that you need to look into the difference betwen a speed
and a velocity.
As I have repeatedly said, the pure forward speed of the leading
spoke's point on the rim (a horizontal velocity) is 20 mph straight
forward, and the pure downward speed of the same spot is 20 mph
straight downward.
Cheers,
Carl Fogel
doug....@gmail.com
>
> I think that you are confused about rpm and speed.
No Carl, you are :-)
> A point on the edge of the rim travels along a circular path at 20 mph
> when your bicycle goes 20 mph,
No, Carl, it does not. It -averages- 20mph. Only in two points is it
actually doing 20, the point at 90 degrees and the point at 270 degrees
where 0 is at the top. All other points are moving either less than or
greater than 20.
> That's how your bicycle odometer and speedometer work. RPM alone is
> useless. You must also have the circumference to figure out the speed.
No, Carl, it is not. They compute the speed of the bike and the
distance travelled from the known circumference of the wheel and a
count of the rotations. Not from the speed of a point on the rim.
> I also think that you need to look into the difference betwen a speed
> and a velocity.
And I think you need to run some numbers.
> As I have repeatedly said,
- incorrectly -
>...the pure forward speed of the leading
> spoke's point on the rim (a horizontal velocity) is 20 mph straight
> forward, and the pure downward speed of the same spot is 20 mph
> straight downward.
Incorrect. Carl, why do you not do the math? The pure downward speed
of the leading point of the rim is 25.5mph. Do the math and show us.
If your logic is correct, the numbers will verify it.
Cheers,
Doug
carl...@comcast.net
Dear Doug,
Since you insist, I suggest that you might ponder an instantaneous
velocity (not speed) of 28.3 mph (not 25.5) at 45 degrees to the
ground (not forward and not vertically) on a bicycle rim of any size
whose axle is moving forward at 20 mph.
Cheers,
Carl Fogel
41
carl...@comcast.net wrote:
> Since you insist, I suggest that you might ponder an instantaneous
> velocity (not speed) of 28.3 mph (not 25.5) at 45 degrees to the
> ground (not forward and not vertically) on a bicycle rim of any size
> whose axle is moving forward at 20 mph.
It's impolite to ask your discussion partner to complete some
mathematical excercise when you have repeatedly declined to do the one
he has repeatedly asked of you:
>Carl, you agree that a point on the rim will accelerate and decelerate
>twice per rotation. Do you also agree that the distance travelled
per
>rotation is 2piR forward, 0 backwards, 2R up, and 2R down?
â
doug....@gmail.com
True, however, in this case I'm afraid it might be for the better :-)
Mike DeMicco
news:1155770780.6...@i42g2000cwa.googlegroups.com:
> Sun CR-18, half the price of a Mavic Open Pro, at least as durable, and
> a whopping 50 grams heavier (probably less than the Open Pro's
> manufacturing tolerance).
It only has single eyelets.
--
Mike DeMicco <blast...@comcast.net>
Tim McNamara
Mike DeMicco <blaster186...@comcast.net> wrote:
> "trey...@my-deja.com" <thomas.t...@gmail.com> wrote in
> news:1155770780.6...@i42g2000cwa.googlegroups.com:
>
> > Sun CR-18, half the price of a Mavic Open Pro, at least as durable,
> > and a whopping 50 grams heavier (probably less than the Open Pro's
> > manufacturing tolerance).
>
> It only has single eyelets.
Get used to it. Few rims have proper spoke nipple sockets these days.
They are too expensive to fabricate and install, and cut into the profit
margins from selling $60 rims plastered in meaningless tech jargon to
fool the punters.
That said, the CR-18 is actually quite durable, being polished rather
than anodized. I've had good results with the polished Sun rims such as
the CR-16a and the CR-18. Given the dearth of polished rims, these are
the ones I would choose once my back stock of MA2s is gone.
41
Tim McNamara wrote:
> In article <Xns982C4CD373E04bl...@130.133.1.4>,
> Mike DeMicco <blaster186...@comcast.net> wrote:
>
> > "trey...@my-deja.com" <thomas.t...@gmail.com> wrote in
> > news:1155770780.6...@i42g2000cwa.googlegroups.com:
> >
> > > Sun CR-18, half the price of a Mavic Open Pro, at least as durable,
> > > and a whopping 50 grams heavier (probably less than the Open Pro's
> > > manufacturing tolerance).
> >
> > It only has single eyelets.
>
> Get used to it. Few rims have proper spoke nipple sockets these days.
> They are too expensive to fabricate and install, and cut into the profit
> margins from selling $60 rims plastered in meaningless tech jargon to
> fool the punters.
I can't believe that cost per se has anything to do with it. The goal
of the manufacturers seems to be to inflate the cost with useless
features that cost money but detract from value. The MA2 was not an
expensive rim, in constant dollars it is much cheaper than an Open Pro.
Instead, it seems to me that the only selling point of them is
durability. That has zero market value, and so the cost cannot be
passed on to the final purchaser. On the other hand, value detractors
such as machined sidewalls and welded joints can be sold, because they
supposedly give you a better experience.
Hank Wirtz
ste...@holyrood.ed.ac.uk wrote:
> Steve Sr. wrote:
> > I am looking to build a set of road wheels and am looking for
> > suggestions for suitable rims. Of course, I would like them to be as
> > light as possible without sacrificing the durability.
> >
> > While we all appreciate a litle nostalgia please limit your
> > suggestions to rims that are still available.
>
> I suggest the ST17 "Elegant" from DRC, or if you need a more solid rim,
> try the ST19. However, for a 700C road wheel suitable for general use,
> including fast road riding, dirt tracks and reasonable luggage
> carrying, the ST17 is fine.
>
> As an alternative, consider the Ambrosio "Nexus". It has the same ERD
> as the Mavic MA2, which might allow you to use your old spokes. Both of
> these rims are double eyeletted, available in 36 hole with a silver
> finish.
>
> I have built wheels with both of these rims, and the results have been
> completely satisfactory.
>
> s.
Do you know of an online reseller of the Nexus? I've been looking for
some. FWIU, they actually bought the MA-2 die molds from Mavic, extrude
the stock in France, then ship the stock to Italy where Ambrosio rolls
them. I've got a set (relabelled for US sale as the "Torelli Master")
and they're fine rims.
I'm also a fan of the Ambrosio Excursion, their only other non-machined
road rim.
Tim McNamara
"41" <KingGe...@yahoo.fr> wrote:
> Tim McNamara wrote:
> > In article <Xns982C4CD373E04bl...@130.133.1.4>,
> > Mike DeMicco <blaster186...@comcast.net> wrote:
> >
> > > "trey...@my-deja.com" <thomas.t...@gmail.com> wrote in
> > > news:1155770780.6...@i42g2000cwa.googlegroups.com:
> > >
> > > > Sun CR-18, half the price of a Mavic Open Pro, at least as
> > > > durable, and a whopping 50 grams heavier (probably less than
> > > > the Open Pro's manufacturing tolerance).
> > >
> > > It only has single eyelets.
> >
> > Get used to it. Few rims have proper spoke nipple sockets these
> > days. They are too expensive to fabricate and install, and cut into
> > the profit margins from selling $60 rims plastered in meaningless
> > tech jargon to fool the punters.
>
> I can't believe that cost per se has anything to do with it. The goal
> of the manufacturers seems to be to inflate the cost with useless
> features that cost money but detract from value. The MA2 was not an
> expensive rim, in constant dollars it is much cheaper than an Open
> Pro.
You're being very nice to the rim makers. The useless features are
generally done in the extrusion or anodizing tank, so these can be done
very cheaply with little or no extra time and little or no extra labor.
Installing nipple sockets requires a machine to form the sockets,
another to install them in the rim, and the people to run those
machines. I would bet that removing that step cuts the cost of
producing a rim in half. It probably costs $5 to produce a $60 rim now.
> Instead, it seems to me that the only selling point of them is
> durability. That has zero market value, and so the cost cannot be
> passed on to the final purchaser. On the other hand, value detractors
> such as machined sidewalls and welded joints can be sold, because
> they supposedly give you a better experience.
They're hypable and marketable. Durability is a cost center. If you
can get the punters to buy a new rim or two every other year, zoom goes
your profit margin.
Every decision made about rim design is about the money, and how to fool
John Q. Public into parting with ever more their wallet contents. The
utter lack of critical independent testing (e.g., by bike magazines,
motivated by ad revenue) is complicit in defrauding the public further.
Thus we end up with break-o-matic rims and fragile plastic frames that
can't withstand the normal bumps of daily life, all touted as "progress"
to a gullible public who wants to Be Like Lance (except for the
training, discipline and diet part). I love seeing fat guys on a Madone
in full Discovery team kit...
We need a resurrection of the Technical Trials in which equipment is
subjected to rigorous, real life testing.
carl...@comcast.net
<tim...@bitstream.net> wrote:
[snip]
>It probably costs $5 to produce a $60 rim now.
[snip]
Dear Tim,
What accounts for the other $55?
That is, if it costs a manufacturer only $5 to make the rim, what
steps and middlemen do you think add $55 to the price?
Cheers,
Carl Fogel
daveornee
some nice testing before Trek hired him.
I am a fat guy that likes to ride and wishes I had the discipline of
Lance and the time for training like he did. I spend a lot of my time
building wheels. Ater 25 years+ of 10,000 miles+/year I slowed bicycle
riding down considerably. (No full Team Discovery kit here, but a few
US Postal items from the Master's Team left.)
I don't think the sockets are a panacea. They make building wheels a
little easier. Eyelets (even single ones like Sun CR-18, Velocity
Synergy, etc.) usually make easier nipple alignment. I have
experienced cracking around spoke holes more with rims that have
eyelets/sockets than rims with no eyelets at all. I once put a new set
of FIR rims in the recycle bin that were fully eyeletted/socketed when
they cracked upon stress relieving them. I am not sure that in inner
web walls of the rims helped support the additional forces, but every
spoke hole had cracks around it with just one set of spoke squeezing.
Fascinating features and claims for low mass are marketable.
--
daveornee
Michael Press
<timmcn-7F4E79....@news.iphouse.com>,
Tim McNamara <tim...@bitstream.net> wrote:
I `discovered' CR-18 rims because they are the one decent
ISO 630 rim to be had. They are better than most rims of
any class, according to my lights. Durable, good looking,
round; and they have eyelets.
--
Michael Press
Tim McNamara
"Hank Wirtz" <ha...@wirtznet.net> wrote:
Hmm. IIRC the Torelli Master rim was not quite the same shape as the
MA2. I haven't seen the Ambrosio Master, but according to their Web
site Hewitt Cycles in the UK sells them (first hit on Google for
"Ambrosio Nexus"):
http://www.hewittcycles.co.uk/
Also Deeside Cycles:
http://deesidecycles.com/info/ambrosio.htm
I think that EuroAsia is the U.S. importer of Ambrosio rims- you could
have your LBS check the catalog for them.
Tim McNamara
carl...@comcast.net wrote:
> On Sun, 27 Aug 2006 14:08:57 -0500, Tim McNamara
> <tim...@bitstream.net> wrote:
>
> [snip]
>
> >It probably costs $5 to produce a $60 rim now.
>
> [snip]
>
> Dear Tim,
>
> What accounts for the other $55?
I'd guess about $25 in profit to the manufacturer, plus
> That is, if it costs a manufacturer only $5 to make the rim, what
> steps and middlemen do you think add $55 to the price?
Shipping to the wholesaler, plus the wholesaler's profit; shipping to
the retailer, plus the retailer's profit.
carl...@comcast.net
[snip]
> That said, the CR-18 is actually quite durable, being polished rather
> than anodized. I've had good results with the polished Sun rims such as
> the CR-16a and the CR-18. Given the dearth of polished rims, these are
> the ones I would choose once my back stock of MA2s is gone.
Dear TIm,
I emailed Sun and asked:
| Can you please tell me if the Sun CR 18 rim is polished, anodized, or
| available in both versions?
|
| I couldn't tell from the web site and the downloaded catalogue
Sun replied:
| What size of CR18 were you looking for? Most of the size's are
| available in both versions.
Cheers,
Carl Fogel