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PostPosted: Fri Mar 10, 2006 4:49 pm 
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very good posting, madcow!
and something to add: maybe one can save something with an fsa ceramic bb(wich, as you said, is absolutely not proven), but this saving would probably just compensate the lost power because of those flexy cranks...


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Posted: Fri Mar 10, 2006 4:49 pm 


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PostPosted: Fri Mar 10, 2006 6:01 pm 
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:goodpost:

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PostPosted: Fri Mar 10, 2006 6:14 pm 
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This guy has been posting ceramic bearings on ebay as replacements for Dura Ace, Hollowgram SI, FSA, etc.

http://cgi.ebay.com/Ceramic-bearings-Sh ... dZViewItem


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PostPosted: Fri Mar 10, 2006 7:20 pm 
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Location: USA
Remove all seals.
Done for a short distance special event in low-dust conditions only.
After removing the seals, it doesn't take long for dust to increase bearing drag higher than with seals.
Bearings (including cup and cone for loose bearings) must be replaced frequently.

'Polishing' or 'lapping' the bearings. You put a polishing compound on a set of new balls, cups and cones and spin then. Obviously, it is only for loose-bearing type of bearings. The instructions warned to be patient and turn the bearings slowly. It is easy to polish too much. After the bearing track is polished correctly, you remove and throw away the polishing bearings and clean the cups and cones super-clean. You then install new bearings with the normal grease and enjoy. It can be done to the bb, hubs and freewheel. It claims to also increase bearing life.

I did this once, it took a loooong time.

This is from an article in a cycling magazine about 25 yrs ago. I don't remember all the details. I can take 2 hrs looking it up if you like.

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PostPosted: Fri Mar 10, 2006 8:39 pm 
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I have good luck with Boca.

www.bocabearings.com

They have searchable inventory set up by manufacturer. You can find FSA, Shimano, or Campy. Then see what they have avaliable.

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PostPosted: Fri Mar 10, 2006 8:49 pm 
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BocaBearings Bicycle Cross Reference Guide Categories Alphabetical list of mfg.
Sealed bearings for almost every mfg there is. Steel, ceramic and full ceramic ($600 each!).

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Equality for Cranks.


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PostPosted: Fri Mar 10, 2006 9:10 pm 
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anyone know or have tried installing the ceramic bearings from FSA megoexo on a clavicula crankset?


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PostPosted: Fri Mar 10, 2006 9:44 pm 
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kom wrote:
Tests by the Danish magazine Cykel-Motion (Mar 2005)
and subsequently supported by calculation, show how using
ceramic bearings can reduce rolling resistance by 50%, saving
22m in just 55 seconds at 32kph. In short, astounding speed
improvement of 4%.


Does anybody have the actual report of this? Because I don't believe it. Bearing friction on bikes has always been considered to be *very* small.

This is from Inside Tri: http://www.insidetri.com/train/bike/art ... 960.1.html

Typical coefficient of friction for a ball bearing is about mu=1.5e-3
(for example, http://www.ntnamerica.com/Engineering/P ... ictemp.pdf)
Power dissipated in one bearing is
P1 = mu * (m/2) * g * V_bearing where m is mass of rider+bike V_bearing is linear speed the bearing rotates at.
P_bearingloss = 2*P1 total power lost in two wheels
V_bearing = V_bike * d/D d = bearing race diameter = wheel diameter
P_bearingloss = mu * mg * d/D * V_bike
P_bearingloss = C_bearingloss * mg * V_bike where C_bearingloss = mu * d/D, can be compared to C_rolling resistance of tires
For a bearing race diameter of 20 mm and wheel diameter of 668 mm (700x23) C_bearingloss = 4.5e-5
for comparison, C_rolling resistance is supposed to be 4e-3 for smooth pavement (e.g. from www.analyticcycling.com), or 100x higher.

For a rider+bike of 75 kg traveling at 10 m/s, I get that the power dissipated in wheel bearings is 0.33 watts.


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 Post subject: hey
PostPosted: Fri Mar 10, 2006 10:29 pm 
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kom wrote:
2002SaecoReplica wrote:
The FSA mega exo ceramic bb's aren't bad.


i was looking at FSA web site and found this:

Tests by the Danish magazine Cykel-Motion (Mar 2005)
and subsequently supported by calculation, show how using
ceramic bearings can reduce rolling resistance by 50%, saving
22m in just 55 seconds at 32kph. In short, astounding speed
improvement of 4%.

Further tests by SKF, and confirmed by the Danish cycle magazine
Cykel Magasinet (Sep 2005), describe dramatic reductions
in friction compared to conventional cycle bearings. For example:

With a pair of race wheels (total of six bearings), friction with
ceramic bearings is reduced 22 fold
While Dura Ace pulleys consume 0.78W @ 500rpm, ceramic
pulleys use less than 0.06W
A Record BB @ 100rpm and 400W consumes 0.6W, the same
BB with ceramic bearings consumes 0.02W


can you give us some SN of ceramic bearing for Record so I test the upgrade and let you know???


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 Post subject:
PostPosted: Fri Mar 10, 2006 10:54 pm 
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Location: Leiden, NETHERLANDS
Madcow:

Fine posting! I like your opinion in that way.....

Westbank:

Look at www.ceramicspeed.com

To all:
The drag of the bearings and other mechanical movement on our bikes don't matter that much. See the attached graphic.

The biggest problem is the front of the rider cutting thru the air. That is consuming the most watts and as you are going faster it gets worse. So mind your position and you can make a lot more profit then the tiny watts you win by using ceramic bearings. But is everything is perfect then you might try the ceramic bearings at the next Olympics (because there it would matter).

I just bought them to try. I am happy with them but comparing to what you will be able to improve ...... The costs are huge!

Aerodynamic spokes and tuning your position are a lot cheaper and give you far more result. But ceramic bearings are COOL!


Attachments:
Grafics_resistance.gif
Grafics_resistance.gif [ 3.89 KiB | Viewed 684 times ]

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PostPosted: Fri Mar 10, 2006 11:58 pm 
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mike wrote:
anyone know or have tried installing the ceramic bearings from FSA megoexo on a clavicula crankset?


That would not be necessary, as you can get a good quality ceramic bearings for the THM's I've put them into half a dozen pairs now. No noticeable difference, except that the seals are even tighter than the originals, but again, tight seals have never bothered me. I don't think it creates a sufficient amount of drag.

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 Post subject:
PostPosted: Sat Mar 11, 2006 3:29 am 
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Location: Tucson
madcow wrote:
mike wrote:
anyone know or have tried installing the ceramic bearings from FSA megoexo on a clavicula crankset?


That would not be necessary, as you can get a good quality ceramic bearings for the THM's I've put them into half a dozen pairs now. No noticeable difference, except that the seals are even tighter than the originals, but again, tight seals have never bothered me. I don't think it creates a sufficient amount of drag.


It's not a significant amount of drag, and the amount that bearing drag increases is a linear function, unlike aero drag. The drag from seals is a constant and doesn't increase with speed.


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 Post subject:
PostPosted: Sat Mar 11, 2006 4:21 am 
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alienator wrote:
madcow wrote:
mike wrote:
anyone know or have tried installing the ceramic bearings from FSA megoexo on a clavicula crankset?


That would not be necessary, as you can get a good quality ceramic bearings for the THM's I've put them into half a dozen pairs now. No noticeable difference, except that the seals are even tighter than the originals, but again, tight seals have never bothered me. I don't think it creates a sufficient amount of drag.


It's not a significant amount of drag, and the amount that bearing drag increases is a linear function, unlike aero drag. The drag from seals is a constant and doesn't increase with speed.


While it doesn't increase with speed part of that drag is not friction but stiction. In essence the effect will decrease as speed increases.

Ciao, :wink:

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