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1 Feb 2010

My wish to build a carbon 2x28" quasi low racer (1)

My current stable of 'bents covers almost every wish a cyclist could have. Yavixa the Mango is pretty car-ish. She combines racing speed with every day and all weather usability. The Pioneer is sort of the same, but without the high speeds and the weather protection. He doesn't fear the unpaved road. Yivalté is the fast racer and tourer for long rides and the best cornering you can think of.

One part of recumbent racing is not yet covered, ultimate speed without any compromise to comfort (well, it's still a 'bent, so it won't be that hard) or practicality. Pure straight line speed is all that counts. A 2 wheeled straimliner has proven to be the best at this subject, but that is a little bit to complicated. I'd like something like a M5 CHR, but than prettier, better engineered and with some sort of finishing. It should also be faster and a whole lot cheaper. Not an easy task, not by far. So best would be to try to design and build it all by myself. With simple techniques, everything made in the shed. Beginning with a donor DF to keep the budget down and the concept simple.

Big wheels help to seriously reduce rolling resistance. Good thing is that such wheels are easy to get. Every road bike has a pair. The donor also comes with light weight brakes which are easy to mount. It's front fork is narrow, thus leaving room for the chain. The gearing is aimed at my goal, a cruising speed of 50km/h in a race. You can get a reasonable donor bike for about €50,-. My brother rides such a bike and it functions well.

In the title a call it 'quasi low racer'. Thing is that I'm only 1.74m in length and that I want a 622 front wheel. By agreeing with a horrible crank wheel overlap, combined with a seat hight of about 38cm, that is possible. The seat angle can't be extremely laid back, I'd be looking at the crank set all the if I'd go below 20 degrees. There is no room in the design and my build capabilities for front wheel drive. I'll go for the classic and efficient rear wheel drive. In that way I also reduce the need for special (expensive) components.

The frame has an integrated seat and is made around a foam core with wet in wet carbon cloth lay up. Metal parts will be isolated from the epoxy using a polyester resin. They'll be glued to the foam frame and  aligned in a rig. After a base layer has been applied to the foam, the delicate job of laying the layers can start. Think of something like 2 (3?) layers 200grams woven cloth with 1 or 2 layers of 5cm wide unidirectional in most places. The UD arranged in such a way to withstand the forces that the frame has to deal with. The top layer start with peel-ply to wrap everything together and provide a good surface for the paint.

If everything goes well, I'll have a frame that weighs 2,5kg. Adding all the donor components should lead to a bike that weighs 10kg or so. With the help of some clever earo features this machine should be very fast. I' have to craft the foam into a sleek shape that pushes and guides the air in the right direction and leaves little turbulence behind. Ambitious? Yes, but it should be possible.

4 comments:

  1. Hai Peter,

    Eenvoudigste manier om tot dat doel te komen is het verbouwen van bvb een M5 lowracer. Die zijn tweedehans zeer veel en goedkoop te krijgen. idt kan met een redelijk minium aan lassen.

    Het ontwerp is dan niet zo mooi en straks als jou schets, maar je bent op het einde van de rit wel zeker dat het werkt!

    Grtz
    Jonathan

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  3. Hoi Jonathan,

    Met veel goedkoper bedoel ik iets ter waarde van een nieuw carbon M5 achterwiel.

    Jouw idee is inderdaad wel een stuk zekerder, eigenlijk ook een heel goed idee. Maar ik vind zelfbouwen ook een mooie bezigheid. Plus het feit dat M5's vrij floppy zijn.

    Groeten,

    Peter

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  4. Ze zijn inderdaad zeer "floppy" Ik zou persoonlijk een iets hoger gewicht voor lief nemen als wat stijver zouden zijn...

    Jonathan - denkt aan een carbon jasje...

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