|Work stand and carbon seat post||txcross|
Aug 5, 2003 1:11 PM
|I have always clamped my bike by the seat post in my work stand. I am looking at getting a bike with a carbon seat post, any problems continuing to work this way or should I clamp to the seat tube/top tube instead? Frame is aluminum...
|re: Work stand and carbon seat post||rrjc5488|
Aug 5, 2003 1:20 PM
|Not as bad as clamping it in the seat tube.|
|I agree.||Dave Hickey|
Aug 5, 2003 4:08 PM
|I clamp mine to a carbon post with no problems. A seat tube clamp puts far more stress on the post.|
|Exact same comment||pmf1|
Aug 6, 2003 10:24 AM
|The last thing you want to do is clamp it to the frame.
Some people are real anal and stick a different seat tube in before clamping the workstand. I've been clamping Look and Colnago carbon posts for years in my Park stand without doing any damage.
Personally, I wouldn't worry about it.
Aug 5, 2003 1:30 PM
|If you scratch, gouge or overstress a carbon seatpost it can fail without warning. To be safe, put an old metal seatpost on your bike while working on it.|
Aug 5, 2003 5:18 PM
|Scratch? I mean, I keep hearing these kinds of things but I wonder if they are true or cyclist folklore. A seatpost "fails without warning" because it was "scratched?"
A workstand clamp probably puts a lot less torque on a CF seatpost than me straining against the saddle on a steep seated climb.
I'm not trying to be argumentative, but I would really appreciate an accurate bottom line on carbon accessories such as seatposts and bars.
|No worse than metal||Dave Hickey|
Aug 5, 2003 5:58 PM
|Put a big gouge in one of todays light weight aluminum seat post or bars and you could have the same result. There was a post earlier this week about someones aluminum bar that failed. It failed without warning. I wouldn't trust a carbon bar with gouge into the fibers but I wouldn't trust an alloy bar big gouge either.|
|True?.... sort of - you might want to read this.||Synchronicity|
Aug 5, 2003 11:19 PM
|Any scratches will weaken a material, even metals. That is why polished items have a greater fatigue strength. |
*BUT* the thing is carbon fibres are only strong because the individual fibres have a very small diameter. That is the only reason a carbon fibre is any stronger than a lump of charcoal. This small diameter reduces the number of imperfections on the microscopic scale. It is that fact that makes them very strong. Aluminium in bulk form, such as a seatpost, is no where near as susceptible to scratches as a fibre-reinforced composite is.
For my degree I did this laboratory experiment where we tested the strength of a *single* carbon fibre! They only take about one newton of force before they break!! It was very hard to set it all up, but I can tell you that if it would have only taken a scratch 1 micron deep in a 6 micron fibre to affect that strength. In comparison, a one micron scratch in a lump of metal is *nothing*. THAT, my friend, is the bottom line.
B.Sc. (Materials Science)
|Wait a minute ...||pmf1|
Aug 6, 2003 10:33 AM
|Doesn't carbon fiber derive its strength from being woven together into a cloth and impregnated with resin? Testing a single strand seems about as valid as testing a single tiny strand of a climbing rope and concluding its not strong because it can't withstand a fairly deep incision.
Personally, I think there is so much urban legend regarding carbon bikes. They're just as strong as any other bike. They don't shatter, melt or suddenly crumble from a scratch. This is all from my own personal experiences riding them for the last 10 years so, THAT, my friend, is only my opinion
|works stands are padded...||C-40|
Aug 5, 2003 7:17 PM
|My park stand has heavy rubber padding in the clamp area. Putting the post in the work stand isn't nearly as stressful as clamping it in the frame.|
|re: Work stand and carbon seat post||Jervis|
Aug 5, 2003 1:52 PM
|Just clamp it onto the post, but be very careful about the pressure you use, as said above. I used to work in a shop and made the mistake of clamping a new bike via the seat tube and it wrinkled the crap out of the decal.
|use a shop rag and don't clamp too tight||maurizio|
Aug 6, 2003 9:10 AM
|Just clamp it to your post. Wrap the post with a shop rag first and don't excessively tighten the clamp on the post and you'll be fine.
The rag will prevent scratches and act as an extra buffer with your post.
I wouldn't switch to an aluminum post - especially - if you are doing this often as this is going to stress out your frame and seat post clamp as well as give you a hassle tring to align your seat to the where it was before.