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Growth-Matching Bicycle

Because children usually get taller
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Bicycles are often fairly inexpensive compared to other forms of transportation, but that doesn't mean you can't spend more money than you might like, when you buy a small one for a child, and then a larger one because the child has outgrown it, and an adult-sized bike later on.

How about a single bike that accommodates the whole age range? It seems to me that only a couple of special things are required to make this work.

Start with an adult-sized bike frame. Adjust the seat to its lowest point. Make sure the pedal assembly is a multi-part thing, with a central axle separate from the pedal-attachments. Connect SHORT pedal-attachments to the central axle.

Many bikes today have disk brakes for the wheels. If your bike has caliper brakes, you will want to remount them so that they are not directly attached to the bike frame, you will want to mount them onto a kind of "extension piece" that attaches to the bike frame.

Now put small wheels on the bike frame. The whole bike is closer to the ground, the brakes still work thanks to them being either extended-caliper or part of the wheel, and the pedals don't hit the ground because they are shortened. A child learning to ride should be able to use this bike (remember to add removable training wheels).

As the child grows, simply get longer pedal-attachments and bigger wheels. Adjust any caliper-brake extensions as appropriate, and also adjust the seat-height. Buying the the bigger wheels and larger pedal-attachments will obviously cost a lot less than buying a whole new bicycle!

Vernon, Jul 11 2012

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       The interior mechanisms add complexity and a bit of extra weight, but overall this is one of those ideas that makes so much sense, I wonder why it hasn't been baked yet.   

       <afterthought> It could even be turned into a sort of communal use membership program: when you purchase the bicycle, you register with the company. As the child outgrows the replacable components like wheels, they are exchanged for larger ones and refurbished to go back into circulation. Tires and brake pads are replaced at the central depot; when parts are exchanged, the member only has to pay for shipping.
Alterother, Jul 11 2012
  

       What's needed, shirley, is a bike that actually grows.   

       Bamboo bikes exist. Simply keep the roots on the bamboo, and attach suitable compost-filled containers at strategic points. Nutrient regulation should keep the bike's growth in step with that of your descendant.
MaxwellBuchanan, Jul 11 2012
  

       ^damn, I was gonna say that.
FlyingToaster, Jul 11 2012
  

       You missed one major factor. A child riding on an adult frame will have to seriously stretch to reach the handlebars. If you make that distance something that the smaller children can reach, then a larger child will have a hard time controlling the bike, because the bars will be to close.
MechE, Jul 11 2012
  

       [MechE], while you have a point, it isn't quite that critical. Handlebars come in different styles and are replace-able, after all. You could pick a design that a child could reach fairly easily.   

       But that's not the only factor. The angle of the seat-extension is also a factor; often the higher the seat, the farther away horizontally it also is from the handlebars --and I did mention adjusting the seat. A modest design change to the frame could enhance that distancing effect, so when the seat is completely un-extended, it is reasonably close to the handlebars.
Vernon, Jul 11 2012
  

       Make the frame entirely modular, with a variety of different-length structural members that lock securely into one-size-fits-all stub joins. That way the entire frame of the bicycle can be expanded as the kid grows.
Alterother, Jul 11 2012
  

       Easier perhaps to have a small bicycle which incorporates a clamp to affix to the child every night while they sleep, to prevent growth.
pocmloc, Jul 12 2012
  

       As far as the bars, simply extending the bars won't work. Cruiser style bars don't have nearly the steering range of flat bars. Likewise, a steep seat-tube angle (so it goes backwards more as it goes up) would only work for a limited range, because a saddle that is hugely behind the pedals results in a very poor (and knee damaging) riding position.   

       It might be more practical to have a childrens bicycle leasing system. The company would have a wide range of frame sizes, and the parents would sign a single lease that would cover the child as they grow.
MechE, Jul 12 2012
  

       Teach your kids how to steal the bike that fits them best.
UnaBubba, Jul 13 2012
  
      
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