Carbon Fiber Bicycle Fabrication

[Peter Matteson]

Not really a FIRST related tech question but I wanted to troll for an answer from some fellow engineers.

I'm looking at a new road bike. Here is what I'm looking at. http://www.specialized.com/SBCBkMode...h rjcg.j27010

I wanted to see if any of you know how Specialized eliminated the bonding lug style construction, i.e. Trek & Giant. I can't figure it out. They claim monocoque construction but I can only figure out how to make this frame in 3 pieces and bond them together. 1 for the main triangle and 1 for each seatstay/chainstay.

Thanks in advance,
Pete

[Travis Covington]

Does monocoque neccesarily mean one complete bike frame? I know that alot of bike manufacturers label their frame as monocoque construction but is really two monoqoque pieces welded together (as far as the aluminum mountain frames go that I am aware of) The seam runs right down the top of the top tube, bottom of the down tube, etc. I'm sure you have seen these frames. The Intense M1 and Tazer FS, Tomac, etc, are good examples

As far as a monocoque carbon frame is concerned, unless there is some sort of lost material in the frame voids, I cannot come up with an answer either.

[RogerR]

ditto to what Travis said. there are some carbon fiber bike makers that do that, but, i'm not sure if Specialized is one of them.

But, if their bikes truly are one-piece monocoque, then they may do it using foam core injection. from what i understand, the foam serves the same purpose as a bladder would.

[PMGRACER]

Been a while since I've been in the Bicycle bus, but 15 years ago Kestrel made a Monocoque style Carbon Fiber Frame. They in fact did use a bladder and foam. That manufacturing method didn't produce a reliable wall thickness as the resin would not flow evenly. That is why Trek originally developed the OCLV design which had the reinforced lugs. I think currently Trek still uses that style of Manufacture but the Head tube, seat stay/ bottom bracket and chainstays are moled as one piece units and straight tubes are bonded to them.

[Peter Matteson]

PMGRACER

Was that an RTM process over the bladder?

The only thing I could come up with was a foam core process but there is frequently discussion of hollow tubes. I couldn't figure out how they would due a lost foam process.

Thanks for the answers everyone.

[PMGRACER]

I don't remember what the actual process was. As far as I know, Kestrel isn't building frames anymore. Also, I don't have much experience with Carbon Fiber molding techniques. Sorry I can't be of much help there.