The engineer in the video makes some bold claims - however he falls down in a very major way. In all his simulations and calculations he claims that the seat post has the same 'flex' across the whole post when in fact the rear part is an aero wing only. Secondly, in his solution mock up he shows the seat tube protruding above the top tube, it does not, it is flush.
Another very poor design by a very respected manufacturer.
- Thread starter davidphilips
- Start date
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IanSmithCSE
Guru
- Location
- Worcester, Worcestershire
Good morning
I would have thought it was almost inevitable that most good, bad and indifferent new designs would come from the upper end of the market.
Mass produced bike design was cracked 60+ years ago, with the exception of a few extra gears.
Mass produced aluminium frames are a new addition having being around for about 30 years, but even they weren't really necessary, although they did help to make cheaper bikes as light as premium steel.
From my perspective the problem is that the improvements in equipment are coming with compromises that are perfectly acceptable for elite level riders as there is nowhere else to go design wise but not for the general non specialist consumer.
So, many people are buying equipment that only makes sense for such elite level riders and not recognising it as such, it certainly doesn't help that this equipment is marketed as suitable for general purpose use.
Aerodynamic efficiency is real and the main selling point for CF so it is inevitable that there will be some leading edge designs that fail. Without such designs then CF is almost pointless as aluminium frames are so close to CF across most of the market, with only the very best CF frames being untouchable by aluminium.
That there are failures should be perfectly acceptable as the gains new being offer are so small that anyone with an FTP of less that say 275watts won't notice them so is buying the wrong product. Only those for whom such as saving have any value should be buying such designs, otherwise it is the same as complaining that Ferrari is a terrible car for doing the weekly shop or taking the kids to school.
I genuinely regard my plastic frame as semi-consumable, anyone who buys a bike with a seat-post custom designed for the frame and expecting a "general consumer" grade rather than an "elite athlete" grade product has probably made a bad choice.
Bye
Ian
I would have thought it was almost inevitable that most good, bad and indifferent new designs would come from the upper end of the market.
Mass produced bike design was cracked 60+ years ago, with the exception of a few extra gears.
Mass produced aluminium frames are a new addition having being around for about 30 years, but even they weren't really necessary, although they did help to make cheaper bikes as light as premium steel.
From my perspective the problem is that the improvements in equipment are coming with compromises that are perfectly acceptable for elite level riders as there is nowhere else to go design wise but not for the general non specialist consumer.
So, many people are buying equipment that only makes sense for such elite level riders and not recognising it as such, it certainly doesn't help that this equipment is marketed as suitable for general purpose use.
Aerodynamic efficiency is real and the main selling point for CF so it is inevitable that there will be some leading edge designs that fail. Without such designs then CF is almost pointless as aluminium frames are so close to CF across most of the market, with only the very best CF frames being untouchable by aluminium.
That there are failures should be perfectly acceptable as the gains new being offer are so small that anyone with an FTP of less that say 275watts won't notice them so is buying the wrong product. Only those for whom such as saving have any value should be buying such designs, otherwise it is the same as complaining that Ferrari is a terrible car for doing the weekly shop or taking the kids to school.
I genuinely regard my plastic frame as semi-consumable, anyone who buys a bike with a seat-post custom designed for the frame and expecting a "general consumer" grade rather than an "elite athlete" grade product has probably made a bad choice.
Bye
Ian
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Archie_tect
De Skieven Architek... aka Penfold + Horace
- Location
- Northumberland
It's a difficult engineering design solution- the clamp bolt is at the bottom acting as a pivot meaning that the whole seat post is constantly rotating backwards against the frame so the seat post is unsecured and free to rotate about the clamping bolt fulcrum- it's inevitably going to wear as shown. It's much better that the manufacturers have engineered a softer seat post to protect the frame from wear.
Making the whole seat post smaller, as his solution, will exacerbate the problem as the rubber grommet will increase the rotational movement back against the aero frame at its thinnest edge... carbon is better in compression but weaker in tension and could split. The clamp bolt should be at the top of the frame and the flex should be engineered into the upper exposed seat post not in the clamped area and it should be held rigidly in the frame in my opinion.
Making the whole seat post smaller, as his solution, will exacerbate the problem as the rubber grommet will increase the rotational movement back against the aero frame at its thinnest edge... carbon is better in compression but weaker in tension and could split. The clamp bolt should be at the top of the frame and the flex should be engineered into the upper exposed seat post not in the clamped area and it should be held rigidly in the frame in my opinion.
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Chris S
Legendary Member
- Location
- Birmingham
It came loose and rotated under the wheel. I just cut off the squashed bit and put the rest back on.
SheilaH
Guest
Why would that make any difference to the issue at hand?
He has a cap that sits over the entire rim of the seat tube and covers it, this would not be possible. Although in practice this makes no difference as a different cap could be used it does show that he has not looked at the problem properly.
