Some time ago (years ago) there was a short thread about the 
mechanical internals of my daughter's tricycle wheel.  Just in case 
anyone forgot (unlikely, I know), the summary is that it looks like a 
normal child's tricycle, with cranks off the axle of the front wheel, 
but it will both freewheel and drive in both directions, so pedal 
forwards and you go forwards, pedal backwards and you go backwards, 
stop pedalling and you free-wheel either way.

It's one of these:
http://toys.kettler.net/typo3temp/pics/8a76c6f8af.jpg

Anyhow, there was some discussion of how it might work internally.  I 
still don't know (daughter 1 has passed tricycle down to daughter 2, 
and I'm still not allowed do dismantle it).

However, someone highlighted the existence of BMX hubs that 
free-wheel both ways (but only drive forwards).  I've just come across 
a youtube video discussing these and their internals, which might be 
of interest to those here that like the mechanical side of cycling:

http://www.youtube.com/watch?v=12I8iK12oqA

regards,   Ian SMith
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Bad form to reply to my own post (especially as no-one else has), but 
I said:
> 
>  Anyhow, there was some discussion of how it might work internally.  
>  I still don't know (daughter 1 has passed tricycle down to daughter 
>  2, and I'm still not allowed do dismantle it).

As a consequence of a parallel discussion elsewhere, someone has 
pointed out the US patent.  So just in case anyone else here remembers 
discussion about how it might work:

http://www.freepatentsonline.com/6705443.html

and while that wants you top register to get pictures, the key one 
could well be this:

http://www.freepatentsonline.com/6705443-0-large.jpg

regards,   Ian SMith
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  |o o|
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