M
Martin Trautman
Guest
Hi all,
do you know any overview of tapered squares of bottom brackets and cranks?
I got one here that is e.g.
+---------- +/////////|
| )
+====\ ) ^ | || ) M | || ) v +====/ )
| )
+\\\\\\\\\| +----------
^W_o ^W_i
<--- L --->
huh, this asci art is pretty ugly. Sorry, this is NOT a thread on the spindle, but shall be read as
a slightly tapered square (/// \\\). Check
e.g. http://www.sheldonbrown.com/harris/images/ta-bb-axles.gif for a better drawing - the picture
above shows the crank screw thread as well.
An old bottom bracket here has e.g. an outer size W_o = 13.0 mm, inner size W_i = 14.0 mm, and a
square length L = 15.0 mm
This square length L is measured from W_o to W_i, which is slightly biased. The angle of the square
is alpha = arc sin ((W_o - W_i) / L), alpha = 3.8 deg
The horizontal length of L thus is L' = L * cos alpha = 14.97 mm For those small angles L and L' can
be assumed to be identical.
The thread for the crank screw here is M12x1 - thus you might name this square as 12/13/14/15
Other spindles are not drilled and threaded for screws, but have a thread for nuts - yet
another standard.
What are the typical sizes of e.g. current Shimano (not splined), Campa etc. cranks or bottom
brackets, JIS or ISO square?
AFAIK both JIS (e.g. Shimano) and ISO (e.g. Campa) share an angle of 2 deg; JIS is 12.65 mm
somewhere, Campa is smaller somehow.
I've found Sheldon's different dust cap sizes of Campa 22 x 1 mm (and others)
e.h. 22.8 x 1 mm Stronglight 23 x 1 mm Lampert 7/8" x 24 tpi ( = 22.22 x 1.05 mm)
... but nothing on square 'standards' and different variations. Which dimensions are there around?
Best regards Martin
do you know any overview of tapered squares of bottom brackets and cranks?
I got one here that is e.g.
+---------- +/////////|
| )
+====\ ) ^ | || ) M | || ) v +====/ )
| )
+\\\\\\\\\| +----------
^W_o ^W_i
<--- L --->
huh, this asci art is pretty ugly. Sorry, this is NOT a thread on the spindle, but shall be read as
a slightly tapered square (/// \\\). Check
e.g. http://www.sheldonbrown.com/harris/images/ta-bb-axles.gif for a better drawing - the picture
above shows the crank screw thread as well.
An old bottom bracket here has e.g. an outer size W_o = 13.0 mm, inner size W_i = 14.0 mm, and a
square length L = 15.0 mm
This square length L is measured from W_o to W_i, which is slightly biased. The angle of the square
is alpha = arc sin ((W_o - W_i) / L), alpha = 3.8 deg
The horizontal length of L thus is L' = L * cos alpha = 14.97 mm For those small angles L and L' can
be assumed to be identical.
The thread for the crank screw here is M12x1 - thus you might name this square as 12/13/14/15
Other spindles are not drilled and threaded for screws, but have a thread for nuts - yet
another standard.
What are the typical sizes of e.g. current Shimano (not splined), Campa etc. cranks or bottom
brackets, JIS or ISO square?
AFAIK both JIS (e.g. Shimano) and ISO (e.g. Campa) share an angle of 2 deg; JIS is 12.65 mm
somewhere, Campa is smaller somehow.
I've found Sheldon's different dust cap sizes of Campa 22 x 1 mm (and others)
e.h. 22.8 x 1 mm Stronglight 23 x 1 mm Lampert 7/8" x 24 tpi ( = 22.22 x 1.05 mm)
... but nothing on square 'standards' and different variations. Which dimensions are there around?
Best regards Martin
