[python] RE.: Re: New Drawing: Drive system




Hi,

This is the forum of weird ideas, right?
So even if I never actually built a bike,
I can suggest anything, no?

So imagine the front bottom bracket  is REALLY wide;
besides the normal chainring there is one chainring at
either extremity; just INSIDE each chainring you have
e piece of frame going backwards to each single-foot
BB. The right singlefoot BB has its chainring on the
right side and a pedal facing inwards on the left side.

Just mirror the setup for the left single-foot BB.

The idea would be to cancel some of the momentum
(and, of course, to be able to mount rotating knives
on the two front chainrings when biking in hostile
environments  ;^) - sorry , couldn't resist)

Godspeed

Rasmus


                                                                                
                                                
                      Ralf Weigel                                               
                                                
                      <Ralf.Weigel@iss.        Til:      python@xxxxxxxxxxxxx   
                                                
                      fzk.de>                  cc:                              
                                                
                      Sendt af:                Vedr.:    [python] Re: New 
Drawing: Drive system                                 
                      python-bounce@fre                                         
                                                
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                      28-06-2004 11:38                                          
                                                
                      Besvar venligst                                           
                                                
                      til python                                                
                                                
                                                                                
                                                
                                                                                
                                                




Sometimes, using Outlook (to read my mail from everywhere in the world, was

my employers choice, not mine...) is a pain. This is a replica of an answer

I sent the 18th June.....It got stuck somewehre.

Hello Paul,

in principle it would work, but...

-it requires a stronger front frame because of the momentum each half crank

induces in only one of the tubes separated by the wheel

-you will have to come up with some really clever bearing design for your
half crank, as the force is at least equal to a normal bottom bracket
system, probably a lot worse (you push forward with your foot and the short

chain excerts a pull to the front as well) and the maximum possible
distance between two bearings is much, much shorter than in a standard
pedal bearing.

I experienced at my Speedbike that the whole frame deforms in an elastic
manner (really hope it stays like this and does not go to plastic
deformation) when I use the 26 chainring I fitted this year, while riding
uphill. First I thought the rear shock absorber blocking was faulty, but
no, the chain makes the frame bending slightly... In fact the bike is most
efficient using the 53 chainring, the 38 is almost the same unless I go
uphill, but the 26 is an emergency exit only. Just calculate: if you push
with, let's say 500N, this force is multiplied by ~3 with small chainrings,

so 1500 N pull at the chain.

Best whishes for your design

Ralf


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At 10:46 18.06.2004 -0400, you wrote:
>Hi all,
>
>and welcome to Ralf.
>
>I am pretty busy until after my wedding day on July 10th. I have been
>working on a design until I can start building in at the end of July.
>
>One of my problems is my short 5'4" frame and legs. I have been trying to
>figure out how I can fit 26 inch wheels(559's I think in metric)
>
>I drew up a design for the pedal system which has half a crank on each
>beam of the front frame, ahead of the front axle.  I'll not try explain
>further but give you the link to my drawing. The drawing is not to any
>real scale as I just use Illustrator to do the sketch, and not a CAD
>program.
>
>http://www3.sympatico.ca/jebelisle/pythonpedals.gif
>
>Any comments on this design concept???
>
>I think this might help stability as power transmission from the legs will
>be closer to the front wheel axle, but its just a guess.
>
>Cheers,
>
>Paul Bell
>
>p.s. Have one other drawing on my basic web page...
>http://www3.sympatico.ca/jebelisle/
>
>
>
>
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>This is the Python Mailinglist at freelists.org
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>Listmaster: Juergen Mages jmages@xxxxxx
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