skid patch stalactites/stalagmites
Thread started by
sciencefriction at 05.8.09 - 10:56 am
What do you get when you plot the number of skid patches (z) as a function of chainring teeth (x) and cog teeth (y) in 3 dimensions and render it in excel?
a bunch of chaotic looking stalactites and stalagmites.
does this change your life or mine?
not at all.
happy friday.
have fun at the swine flu ride everyone and i hope you remember this when you become a zombie.
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Seems like the larger the cog, the greater possible # of patches....
vor05.8.09 - 11:42 am
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Here is a Python script that will calculate patches and gear inches:
from copy import copy
class FixedBike():
def __init__(self, wheel, chain_ring, sprocket):
"""
wheel = the diameter of the wheel in inches
chain_ring = the number of chain teeth
sprocket = the number of chain teeth
"""
self.wheel = wheel
self.chain_ring = chain_ring
self.sprocket = sprocket
self.skid_patches = self.skid_patches()
self.gear_inches = self.gear_inches()
def skid_patches(self):
"""
Determines the number of points of contact there are during
non-switch skidding.
"""
remainder = int(self.chain_ring) % int(self.sprocket)
if remainder != 0: x = float(self.sprocket) /
float(remainder)
else: x = 1
y, c = copy(x), 1
while int(y) != y:
y = x * c
c += 1
return int(y)
def gear_inches(self):
"""
Determines the gear inches.
"""
return float(self.wheel) * float(self.chain_ring) /
float(self.sprocket)
a = FixedBike(27,48,15)
print a.skid_patches
print a.gear_inches
http://braydon.com/blog/2009/4/23/fixed-gear-bicycle
vor05.8.09 - 11:50 am
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Well I think that's covered.
vor05.8.09 - 12:43 pm
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that's the same table i used to render the 3d image.
this one looks cool too. the curves are much more defined.
sciencefriction05.8.09 - 1:22 pm
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Hahah...
That one looks less random, there has to be a proper equation.
vor05.8.09 - 2:16 pm
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as the ratio between the chainring's angle of rotation and the wheel's angle of rotation get closer and closer to 1:1, your number of skid patches approaches 1. right?
Eric Hair05.8.09 - 2:41 pm
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Right.... Easy way to do it in your head is if your Chain / Sprocket = a nice quarter number 3.5, 3.25, 3 3.75 you have very few patches. If you first get something like 3.1, or 3.6 you've got plenty. I have the worst possible ratio of 1:1, haha... which I didn't know until after the fact.... but I don't really skid anyways.......
braydon05.8.09 - 2:56 pm
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wait I have a 1:3 ratio (or 3:1) .... 48 / 16
vor05.8.09 - 3:06 pm
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Transformerbrake.
vor05.8.09 - 3:25 pm
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