Durability Of Velocity Aerohead Rims In 20/24 Hole Drillings.

On Nov 7, 10:05*pm, DirtRoadie wrote:
On Nov 7, 6:05*pm, Frank Krygowski wrote:

*As
with a lot of the issues we talk about, I'm not trying to forbid your
choice. *But I am trying to apply a little science to the discussion.
...
And after you have answered those questions please also tell me what
wheels I need to buy for my bicycle the next time that issue raises.

DR: There's no need to go into much detail. It's easy to tell what
wheels you need.

You need the lightest, most aerodynamic wheels you can possibly find.
For you, durability is no concern. Availability of repair parts (like
proprietary spokes and nipples) is no concern. Compatibility with any
other part of your bike is no concern. Actual performance difference
in any given situation is no concern, although you do need to have
numbers to tell your friends. (Claimed drag reduction ought to
suffice.) Of course, price is no concern, as long as they're suitably
expensive.

You NEED the wheels with the highest zoot factor, the ones that match
the flashiest advertisements, and that match those used by the teams
with the biggest budgets. And the following year, when the ads and
the sponsorships change, you'll NEED a new set of wheels.

Hope this helps. Enjoy!

- Frank Krygowski

On 2010-11-06, Jobst Brandt wrote:
Ben C (who?) wrote:
[...]
I think the assessment of wheel durability is misplaced. When I
consider the many miles on unpaved or cobble roads that my wheels
have crossed in the more than 30 years (since I wrote "the
Bicycle Wheel"), the same MA-2 rims, that even had a pinch flat
or so, are still working well with their 36 spoke Campagnolo
RECORD hubs.

OH! but they aren't as light as CF wheels are as aerodynamic as
18 spoke wheels. I can only ask, "What is the goal of your
wheels?" I think I made clear what causes fatigue failures and
how these stresses are avoided by stress relieving wheels after
tensioning.

If that were true, then why wouldn't it work for 24 or 18 spoke
wheels?

For the same reason four steel spoked wheels don't work. Load
concentration is too great at the few spokes that there are. If
you look at the load diagrams in "the Bicycle Wheel" you'll notice
that a 18-spoke wheel will have its entire load on essentially one
spoke instead of four or more.

Why should that matter? Are you saying that even "stress-relieved"
spokes in a 36H wheel are in places within 25% of their yield
stress?

THE RIM! Get the message. Spokes can be made to support great loads,
but rims crack and that is the subject of this thread. Stop the
mis-attributions and out of context depictions.

Well, you wrote:

OH! but they aren't as light as CF wheels are as aerodynamic as
18 spoke wheels. I can only ask, "What is the goal of your
wheels?" I think I made clear what causes fatigue failures and
how these stresses are avoided by stress relieving wheels after
tensioning.

So if you weren't talking about spokes, are you now claiming that "stress
relieving" stops the rim fatiguing?!!

Why not I suppose. In for a penny in for a pound.

Anyway, I suspect you just got your catechisms jumbled up. But the point
I now realize you were trying to make, which is that wheels with fewer
spokes need higher spoke tension, which wrecks the rim, is not a problem
in reality. If everything else were equal, that would be true, but it's
not. Modern rims are deeper section and stiffer, and need no more
(possibly less) tension in each of their 18 or 24 spokes than the MA-2
needed in its 36.

In article
,
Chalo wrote:

Ed wrote:

I am not convinced an eyelet is goint to solve things unless you get
one that transfers the force to the inner wall of the rim - I don't
think they make those any more.

A single eyelet (grommet) serves two valuable purposes: It provides a
better bearing surface for the spoke nipple head, and it helps prevent
galling damage at the drilling from initiating cracks into the rim
extrusion.

Double eyelets (sockets) are still offered by Mavic, Rigida, and Alex
on a few models. Whether they actually transfer any load to the
internal wall of the rim depends on the specifics of the socket and
the rim extrusion and manufacturing tolerances. On modern deep and
semi-deep section rims, sockets offer the benefit of keeping nipples
from going astray within the rim channel while the wheel is being
laced.

The CR18 has eyelets. It does not have sockets
but they are overbuilt with doubled walls that
serve for sockets.

http://www.amazon.com/gp/product/images/B000C15K6G/ref=dp_image_text_0?ie=UTF8&n=3375251&s=sporting-goods

--
Michael Press

On 11/8/2010 3:39 AM, Michael Press wrote:
In article
,
wrote:

Ed wrote:

I am not convinced an eyelet is goint to solve things unless you get
one that transfers the force to the inner wall of the rim - I don't
think they make those any more.

A single eyelet (grommet) serves two valuable purposes: It provides a
better bearing surface for the spoke nipple head, and it helps prevent
galling damage at the drilling from initiating cracks into the rim
extrusion.

Double eyelets (sockets) are still offered by Mavic, Rigida, and Alex
on a few models. Whether they actually transfer any load to the
internal wall of the rim depends on the specifics of the socket and
the rim extrusion and manufacturing tolerances. On modern deep and
semi-deep section rims, sockets offer the benefit of keeping nipples
from going astray within the rim channel while the wheel is being
laced.

The CR18 has eyelets. It does not have sockets
but they are overbuilt with doubled walls that
serve for sockets.

http://www.amazon.com/gp/product/images/B000C15K6G/ref=dp_image_text_0?ie=UTF8&n=3375251&s=sporting-goods

The Sun CR-18 [1] is a good rim, but rather narrow at 22.5 mm.

[1] http://www.sun-ringle.com/bmx/rims/cr-18/,
http://www.sun-ringle.com/product-vault/road-rims/cr18-700c-29er/.

--
Tom Sherman - 42.435731,-83.985007
I am a vehicular cyclist.

On Nov 5, 5:42*pm, wrote:
On 05 Nov 2010 22:05:51 GMT, Jobst Brandt wrote:





Ben C (who?) wrote:

I have a set of Areoheads based on a set of Dura Ace hubs with the
18/24 combination.

Great wheels if you consider them race day only. *I normally use
them for Criterium racing and longer/hillier sportifs.

I have had a couple of problems though, just the rear rim hitting
a pothole and have just recently replaced the front due to
cracking around the nipples.

Considering the front was 2 years old and had not even needed a
truing during this time leads me to think I hit something but did
not notice it at the time.

I think the assessment of wheel durability is misplaced. *When I
consider the many miles on unpaved or cobble roads that my wheels
have crossed in the more than 30 years (since I wrote "the Bicycle
Wheel"), The same MA-2 rims, that even had a pinch flat or so, are
still working well with their 36 spoke Campagnolo RECORD hubs.

OH! but they aren't as light as CF wheels are as aerodynamic as 18
spoke wheels. *I can only ask, "What is the goal of your wheels?"
I think I made clear what causes fatigue failures and how these
stresses are avoided by stress relieving wheels after tensioning.

If that were true, then why wouldn't it work for 24 or 18 spoke wheels?

For the same reason four steel spoked wheels don't work. *Load
concentration is too great at the few spokes that there are. *If you
look at the load diagrams in "the Bicycle Wheel" you'll notice that a
18-spoke wheel will have its entire load on essentially one spoke
instead of four or more.

You might read about it. *Bike shops sell books, as does Amazon.

http://www.avocet.com/wheelbook/wheelbook.htmlq
http://tinyurl.com/22v535

Jobst Brandt

Dear Jobst,

Can you give us some load calculations or diagrams on 24 and 18 spoke
figures?

Cheers,

Carl Fogel- Hide quoted text -

- Show quoted text -

no scatter diagrams but I have asked various LBS types
receiving' whoa you wouldn't beleive it's' as response.
At first sins of wear, install Ti washers. Lube brake surface with
CRC Rubbah Dressing. Lube hub's spoke holes with spokes with Finish
Line Dry Lube or Pedro's 2.0

On Nov 7, 11:27*pm, Frank Krygowski wrote:
On Nov 7, 10:05*pm, DirtRoadie wrote:

On Nov 7, 6:05*pm, Frank Krygowski wrote:

*As
with a lot of the issues we talk about, I'm not trying to forbid your
choice. *But I am trying to apply a little science to the discussion.

On Nov 5, 9:25*am, landotter wrote:
Did you check the tension on them? Alex rims are made from a strong
alloy. Tension that's enough to crack them is enough to destroy most
other similar rims, regardless of brand.

A strong alloy is not necessarily good. See "stress corrosion
cracking".

On Nov 7, 10:27*pm, Frank Krygowski wrote:
On Nov 7, 10:05*pm, DirtRoadie wrote:

On Nov 7, 6:05*pm, Frank Krygowski wrote:

*As
with a lot of the issues we talk about, I'm not trying to forbid your
choice. *But I am trying to apply a little science to the discussion.

On Nov 7, 7:53*pm, "Barry" wrote:
I though that Bicycling Science would have something about the variation of
power during the pedal stroke, and how peak instantaneous power depends on
cadence, but I couldn't find anything relevant.

Peak = double the average is a good starting point. Also if you do the
calculations, you'll find that heavy and strong riders on steep grades
in a low gear are the "worst case" scenario for rear wheel torque.

On 11/8/2010 12:26 PM, Ron Ruff wrote:
On Nov 7, 7:53 pm, wrote:
I though that Bicycling Science would have something about the variation of
power during the pedal stroke, and how peak instantaneous power depends on
cadence, but I couldn't find anything relevant.

Peak = double the average is a good starting point. Also if you do the
calculations, you'll find that heavy and strong riders on steep grades
in a low gear are the "worst case" scenario for rear wheel torque.


I think the worst case for spokes is when riders "toss" a bike side to
side during sprints. You get big lateral loads.