Difference between revisions of "Eccentric Bottom Bracket Modification"

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(Problem)
 
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===Problem===
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I know a few people around the country that are sponsored by Gary Fisher to ride 29" Rig Singlespeeds for the 2007 season.
 +
 +
The biggest complaint that they all have is the weight of the stock EBB cam. I figured that I would make a tool to trim some fat off the EBBs for these racers. Every gram counts.
 +
 +
The Fisher EBB measures 56.75mm (2.234").
 +
 +
This is a picture of the Fisher EBB. It is designed like a giant quill stem. It weighs 285 grams. That is some serious bullshit.<br>
 +
[[Image:Rig wedge ebb.gif]]<br>
 +
 +
===One Possible Solution===
 +
 +
It may be possible to shim the bb shell with some 0.050" delrin sheet or aluminum tube and use a Bushnell expanding eccentric.
 +
 +
A Bushnell EBB cam:<br>
 +
[[Image:Bushnell ebb.gif]]<br>
 +
 +
This will be researched a bit.
 +
 +
===The PVD Mod===
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 +
[[Image:Rig1.jpg]]<br><br>
 +
 +
[[Image:Rig2.jpg]]<br><br>
 +
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[[Image:Rig3.jpg]]<br><br>
 +
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[[Image:Rig4.jpg]]<br><br>
 +
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[[Image:Rig5.jpg]]<br><br>
 +
 +
102 gram weight savings.
 +
 +
===Other Peoples Work===
 +
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:*[http://www.creepyfriendly.typepad.com/ creepyfriendly] - 90 gram (unconfirmed) reduction
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:[[Image:Light2.jpg]]
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:*[http://forums.mtbr.com/member.php?u=252893 mckeand13] - 80 gram (unconfirmed) reduction
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:[[Image:EBB1SMALL.JPG]]
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===Generic EBB Weigh In===
 
===Generic EBB Weigh In===
 +
 +
This EBB cam is from a Zion Single. It's pretty generic and will serve as a good test peice untill I get the actual units in hand.
 +
 +
189 Grams.<br>
  
 
[[Image:Light-EBB-8.jpg]]<br><br>
 
[[Image:Light-EBB-8.jpg]]<br><br>
Line 8: Line 53:
 
[[Image:Light-EBB-3.jpg]]<br><br>
 
[[Image:Light-EBB-3.jpg]]<br><br>
 
[[Image:Light-EBB-4.jpg]]<br><br>
 
[[Image:Light-EBB-4.jpg]]<br><br>
 +
 +
===Machining the EBB===
 
[[Image:Light-EBB-5.jpg]]<br><br>
 
[[Image:Light-EBB-5.jpg]]<br><br>
 
[[Image:Light-EBB-6.jpg]]<br><br>
 
[[Image:Light-EBB-6.jpg]]<br><br>
 +
 +
===Final Weight===
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 +
135 grams. 54 grams shaved off!
 +
 +
I could probably pull off another 10 grams, but I've done enough for now.<br>
 
[[Image:Light-EBB-7.jpg]]<br><br>
 
[[Image:Light-EBB-7.jpg]]<br><br>
  
 
[[category:Bicycle]]
 
[[category:Bicycle]]
 
[[category:Drivetrain (Bicycle)]]
 
[[category:Drivetrain (Bicycle)]]
 +
[[category:Frame Building]]

Latest revision as of 23:52, 7 February 2007

Problem

I know a few people around the country that are sponsored by Gary Fisher to ride 29" Rig Singlespeeds for the 2007 season.

The biggest complaint that they all have is the weight of the stock EBB cam. I figured that I would make a tool to trim some fat off the EBBs for these racers. Every gram counts.

The Fisher EBB measures 56.75mm (2.234").

This is a picture of the Fisher EBB. It is designed like a giant quill stem. It weighs 285 grams. That is some serious bullshit.
Rig wedge ebb.gif

One Possible Solution

It may be possible to shim the bb shell with some 0.050" delrin sheet or aluminum tube and use a Bushnell expanding eccentric.

A Bushnell EBB cam:
Bushnell ebb.gif

This will be researched a bit.

The PVD Mod

Rig1.jpg

Rig2.jpg

Rig3.jpg

Rig4.jpg

Rig5.jpg

102 gram weight savings.

Other Peoples Work

Light2.jpg
EBB1SMALL.JPG

Generic EBB Weigh In

This EBB cam is from a Zion Single. It's pretty generic and will serve as a good test peice untill I get the actual units in hand.

189 Grams.

Light-EBB-8.jpg

Making the Arbor

Light-EBB-1.jpg

Light-EBB-2.jpg

Light-EBB-3.jpg

Light-EBB-4.jpg

Machining the EBB

Light-EBB-5.jpg

Light-EBB-6.jpg

Final Weight

135 grams. 54 grams shaved off!

I could probably pull off another 10 grams, but I've done enough for now.
Light-EBB-7.jpg