Bike Forums - Carbon Clincher Rim Manufacturing Primer; Taiwanese vs Chinese Methods

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Quote:

Originally Posted by Bob Dopolina (Post 16002294)

@ Mark Kelly

Any thoughts on Cup Stacked Carbon nanotubes in terms of the thermal and structural benefits?

Bob

I know next to nothing about them.

Mark

Quote:

Originally Posted by Bob Dopolina (Post 16002107)

I'm all ears. I have been looking at a disc specific application myself. I wanted to find a partner before committing to the tooling and that hasn't happened yet.

My partner developed carbon clinchers for disc applications before disc brakes became mainstream as he saw what was coming, one would be looking at a nigh indestructible rim that was 25 % lighter and stiffer than anything you can find today.

But producing these is expensive on a smaller scale, outsourcing introduces variables and inevitable quality control issues.

Quote:

Originally Posted by Sixty Fiver (Post 16002482)

Welcome to my world...

If there is a discussion to be had (and there may) PM me.

Quote:

Originally Posted by redoak (Post 13810386)

http://i.telegraph.co.uk/multimedia/...h_1658574c.jpg

I love this picture. It looks like he's falling into a wormhole or something. Or perhaps riding into Narnia.

Quote:

Originally Posted by Bob Dopolina (Post 16002107)

I'm all ears. I have been looking at a disc specific application myself. I wanted to find a partner before committing to the tooling and that hasn't happened yet.

No question that carbon wheels are the future and in particular they make sense for disk applications. If disk brakes really start to take off on road bikes, I believe this will accelerate the usage and popularity of carbon wheels even on mid level road bikes.

Quote:

Originally Posted by Mark Kelly (Post 16001934)

Tg in epoxies is basically shorthand for crosslink density. Crosslinking occurs late in curing (after chain formation and branching) so it is strongly influenced by cure cycle - the epoxy must be warm enough for the chains to be moderately mobile or they won't bang into one another often enough to crosslink to the required degree. For a given formulation, Tg tends to follow cure temperature, at a first guess you can knock 20C off the cure temp to get the Tg but this is not universal; simple amine curatives won't achieve high Tg no matter what you do but can achieve a Tg above 50C with room temperature cure.

The curing behaviour also explains why people who want to cut corners won't use these resins: besides their extra cost they also impose significantly greater processing costs because the cure cycle must be tightly controlled to get the right properties. If there's not enough chain growth before it enters the crosslink phase the chains won't be able to crosslink properly, if they are too long they will be too immobile to promote crosslinking. Some of the higher spec epoxies have much more complex behaviour - one I use cures nicely at 50 C but then requires a post cure bake at 120 to achieve full properties.

A typical high end resin will use aromatic amine curatives: the aromatic ring gets in the way, slowing the cure right down so an elevated temperature cycle must be used. As above, this will result in a higher Tg but it also gives other benefits such as improved chemical resistance. Some of the simpler aromatics will give a high Tg at the cost of increased brittleness and some of them are quite toxic / carcinogenic so more complex aromatics (including anhydrides) are usually used and inevitably these are more expensive.

BTW resin Tg mostly affects strength and toughness, stiffness is 99% determined by the fibres.

Caveat: I'm not an epoxy chemist, just an end user. I'm actually a winemaker by trade, I just happen to like chickenwire.

Really an informative post and underscores the importance of not only epoxy selection in terms of glass transition temperature as it relates to cross linking and strength but effect of processing and cure. And then there is the uniformity of the lay up and pressures and temperatures over time which have a huge effect on the structural integrity of the end product. First 5000 wheels maybe fine but new batch of material, tool wear and process variation can change everything. Same has to apply to all carbon bicycle items from handlebars to frames to forks. Forks in this discussion come to mind. Fork steerers made of carbon seem to be most susceptible to failure in the field. Even major bike companies who sweat the details have had recalls due to failure to avert sweeping lawsuits.

To me, carbon is the best bike material on many levels but also a material very sensitive to design and process and why I personally like to stick with name brands that perform lot acceptance testing of materials and ongoing destructive testing of their products over time to determine safety factor. That isn't to say that Chinese or even perhaps more evolved Taiwanese smaller companies as Bob explained aren't making a great product. Many do and supply the big guys and some of the smaller companies will emerge and turn into bigger companies because their product is so good. I just personally don't want to buy price and find out the hard way a company without a name brand did cut corners by not buying good material or controlling their process adequately...the knock on 'some' Chinese companies.

How often has anyone seen a braking surface "wear out" on a carbon wheel? I've searched high and wide and can't really find this result. How many people buy these carbon wheels and feel it wasn't worth the cash and buy aluminum the next time? I'm going to buy a 23mm+ wheel soon, not sure what it will be made out of. CF is sexy.

Quote:

Originally Posted by Hiro11 (Post 16001377)

It seems like a lot of people on the internet are focused on mainland resellers. I'm surprised that there are so few smaller Taiwanese brands out that make it easy to buy their wares. I'm not talking Giant or Merida, I'm talking smaller brands like Velocite, Neo, Swift, Axman and the like. You can find these brands, but it's a bit of a pain. They all make some truly cool frames in the same factories (sometimes mainland) that top end European-branded stuff is made in. I think a lot of American cyclists would be willing to pay the premium over rock-bottom Xiamen pricing to get Taiwanese quality.

Some of those companies are manufacturers and not just "brands". The reason they're made in the same factory as some European companies' products is that they are the factory. The European manufacturers are their customers, not the end users. Competing with ones customers is risky business and may be explicitly prohibited in the manufacturing agreements.

Quote:

Originally Posted by halfspeed (Post 16004584)

I get that, but all of those are sold at retail just not in the US.

Also, the line between different brands sharing designs gets a little hazy in some cases. BH uses a lot of designs that are available from other sources. Ditec seems to be rebadged Orbeas. Frames badged Fondreist and Masi are sold under a variety of other brands. Even old designs show up occasionally here and there: Neuvation sells rebadged Blue and Cervelo designs from a few years ago. Etc. Obviously this is dependant on the specifics of the agreement.

Quote:

Originally Posted by Hiro11 (Post 16004789)

I get that, but all of those are sold at retail just not in the US.

Also, the line between different brands sharing designs gets a little hazy in some cases. BH uses a lot of designs that are available from other sources. Ditec seems to be rebadged Orbeas. Frames badged Fondreist and Masi are sold under a variety of other brands. Even old designs show up occasionally here and there: Neuvation sells rebadged Blue and Cervelo designs from a few years ago. Etc. Obviously this is dependant on the specifics of the agreement.

That's pretty much the whole point.

Great vid. Nice step by step explanation of the general processes.

Now, how many steps do you think you can eliminate to save money? Lots and lots.

Of those steps, how many of those have the potential to impact quality and consistency? Lots and lots.

Was scanning Velonews tech articles which are always an interesting read and stumbled upon Giant's new foray into 27.5" mtb arena...a pretty bold step as many in the off road community now embrace 29-ers. 27.5" wheel size for those not into mtb's is 650 wheel size with tall rubber...the standing height of the tire fully inflated. As a sidebar 29 inch mtb's were slow to evolve because of the added spool up inertia of the bigger wheels...mtb tires have greater mass. But general consensus is the upside of a 29er overshadows this deficit. I own a 29er and do like the platform but no question many will embrace the 27.5" platform which will split the difference.

Since Giant has to release new CF molds for their 27.5" series of mtb, below is particularly relevant to discussion here and speaks to the complexity and cost of CF. I think the last sentence of the article is particularly telling of discussion here and largely what differentiates quality:

In a departure from the company’s usual pattern, Giant is releasing both carbon and aluminum versions of its new 27.5 models. Because of the costs associated with building the molds for composite bikes, Giant has traditionally made new models in aluminum first. It is comparatively easy to make adjustments to an aluminum bike’s geometry.
“You can make changes in aluminum,” said Justkaitis. “If you make the angles wrong, you can make minute changes to that. The tooling associated with aluminum is easy. Once you commit to composite molds, you are committed to those molds, and you can’t change it. Those are literally chiseled out of steel.”
The molds for a single size of a carbon frameset can run $75,000 to $100,000, which is part of the reason for the high retail price of the finished bikes. The process of building the frames is labor intensive, too, and Justkaitis does not expect the costs of high-end composites to come down any time soon.
“There are over 500 pieces [of carbon fiber] in an average road frame, pieces that are placed by hand,” said Justkaitis. “We have molds, and into the molds go individually shaped and cut pieces at certain angles at certain degrees. There is no way to automate the process. It’s all done by hand. It’s not like you’re pouring goo into a mold.”
The ride quality, the elusive “feel” of the bike, comes from the carbon lay-up, which is the way the pieces are set into the molds. “The secret is the math that goes into the lay-up,” said Justkaitis. “There’s an astounding amount of math that goes into this stuff.” The basic processes of building carbon bikes are the same across the industry. The way the carbon pieces are set together is not.

Quote:

Originally Posted by halfspeed (Post 16004584)

While potentially prohibited, Chinese protections on intellectual property can be very minimal for Western companies (see fake ipods). Part of the advantage of manufacturing in Taiwan is that the factory won't immediately sell your design from under you.

And the Taiwanese companies are selling stuff, see Giant and Merida. But those companies actually have bike development R&D. If one of the smaller factories started selling other people's designs they'd very quickly lose all their business to China (cheaper) or other Taiwanese factories (IP).