Half a croissant, on a plate, with a sign in front of it saying '50c'
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plastic bike

Why not take advantage of new thermoplastics/thermosets?
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Seems to me there's an opportunity there for plastic bicycles -- light, stronger than steel depending on resin chosen, and the ability to 'cast' or injection-mold parts to whatever shape you need. Combine functions for effecient design. The gearset, etc. could be designed to take advantage of the fact that some plastics don't require lubrication, and I doubt that a human would exceed the yield strength of an appropriate design. Wondered if it was baked, but didn't find anything current online...Add rims that are solid extrusions, with a rubber cap and you have puncture-free rides, and the 'spokes' could be like blades (see spinergy(tm) wheels) that act as shock absorbtion or use a fork shock... Might reduce my bike's weight from 35# to a more reasonable 20#...
ruxpin76, Mar 29 2004

(?) Swedish plastic bike, 1982 http://www.dtek.cha.../jpg/plastcykel.jpg
main problem was poor rigidity [FarmerJohn, Oct 06 2004, last modified Dec 04 2004]

The XtraCycle project http://www.xaccess.org/index.html
A great link and a reason to bake this ASAP [subflower, Oct 14 2005]

Itera plastic bike http://en.wikipedia...era_plastic_bicycle
The same bike as refered to above. [BlueGiraffe, Apr 26 2007]

[link]






       As far as I know: Aluminium, Reynolds 531, Carbon fibre - All used before. Aluminium tends to crack, carbon fibre is extremely stiff and if used for forks without suspension would give a very uncomfortable ride.
Reynold tubing is the best all round, since it can flex slightly (esp. good for forks).
Plastic would have some tough competition, especially when it comes to roller bearings and chains.
If your bike weighs 35lb, perhaps you don't need to look for plastic to solve your problem.
My gut feeling is that plastic would be a heavier solution (..he says without checking material specifications).
Ling, Mar 29 2004
  

       Note that there is now a mandated minimum bike weight of 7kg for racing bikes (15lbs) and many are right on this limit, many of these use carbon fibre a strong form of composite.   

       You may just need to spend the money to buy a decent bike.
PiledHigherandDeeper, Mar 29 2004
  

       I remember fellow club riders spending a fortune on titanium bolts and what-nots. I always thought that at this level, having a good crap and cutting your toe-nails before an event would have more effect.
(A little training would make the biggest difference!).
At the level that [UnaBubba] is talking about, absolutely everything counts, including shaving your legs and polishing your teeth.
Ling, Mar 30 2004
  

       I take my hat off to him: I marvel at the speed some of these guys can sustain.
The really noticeable effect is that they can normally maintain a good pace up an incline, since it is nearly all wind resistance at those kind of speeds.
Even at the more humble speeds at which I used to run around, it was surprising how little difference there was in average speed between a bicycle and a car on some journeys.
Ling, Mar 30 2004
  

       I don't know of any thermoplastics that have a better strength to weight ratio than good old crome- moly steel, and carbon fiber is definitely widely baked.   

       [below: [bungston], all that chrome moly hoohah was for the tightpants crowd 20 years ago. The aim of this idea was for lighter bikes, not cheap or recyclable or toy-like.]
oxen crossing, Mar 30 2004
  

       //polishing your teeth// Yeah, teeth are a luxury that will likely be removed in future racers.   

       I think this is absolutely bakable - not for high-performance bikes, but definately for inexpensive bikes. I'm picturing larger volumetric areas for weak points like the chain to deal with strength issues.
Worldgineer, Mar 30 2004
  

       Yes: disposable bike. All that chrome-moly hoohah is for the tightpants crowd. I want a bike that comes in a 3 pack, each a different color. A bike that I can ride into the ocean off a pier. A bike that makes you happy when someone steals it, because you know they are using it themselves for transportation.   

       Maybe I just miss my Big Wheel.
bungston, Mar 30 2004
  

       I think this is a great idea. The problem is that cost is not preventing bicycles from being used more widely for transporation. If this is jsut for rich guys, there are already lots of carbon bikes...mine is a Giant TCR Advanced.
seriousconsult, Dec 04 2004
  

       You have a giant bike? How do your feet touch the ground?
Belfry, Dec 04 2004
  

       Made from recycled materials a good bike can transport tons of useful stuff and make life a LOT easier for people who have no car or gasoline. see link.
subflower, Oct 14 2005
  

       I once met someone that takes old bikes and turns them into wheelchairs for people in 3rd world countries. Perhaps the cheap plastic bicycle company could also have a cheap plastic wheelchair product.
Worldgineer, Oct 14 2005
  

       This has already been tried about 30 years ago. I have seen one in a Materials lecture it didn't seem particularly great. The whole thing was too flexible which made riding difficult, especially steering.
BlueGiraffe, Apr 26 2007
  

       I'm surprised they haven't made CF skateboards.
apocalyps956, Apr 26 2007
  
      
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