22mm Square Cranks

[email hidden] (Dave) wrote in message news:<[email hidden]>...

Quoted message said:

Obsolete/"retro" question... if each square crank is compatible with a
specific BB spindle length why did they never print that number on the
cranks? Or did they? Can it be derived by measuring the thickness of
the crank? Thanks!

Who says a tapered-square crank is specific to a BB spindle length? BB
spindle length is determined by frame design, number of chainrings,
and crankarm design.

For instance, a Sugino "Mighty Tour" crankset might use a 120mm
spindle if it was configured as a double or a 126mm spindle if a
triple. The crankarm forgings were identical. Conversely, a double
crank might use a 118mm spindle on a road bike with minimal
clearances, while double on a touring bike might use a 122mm spindle
to clear splayed chainstays.

The variety of spindle lengths allowed an intelligent mechanic to
fine-tune the spindle length to the application or the rider. The rise
of specific spindle lengths for particular cranksets is a late
invention, and not a particularly welcome one, IMO.

Jeff

[email hidden] (Jeff Wills) wrote in message news:<[email hidden]>...

Quoted message said:

[email hidden] (Dave) wrote in message;

Quoted message said:

Obsolete/"retro" question... if each square crank is compatible with a
specific BB spindle length why did they never print that number on the
cranks? Or did they? Can it be derived by measuring the thickness of
the crank? Thanks!

Who says a tapered-square crank is specific to a BB spindle length? BB
spindle length is determined by frame design, number of chainrings,
and crankarm design.

For instance, a Sugino "Mighty Tour" crankset might use a 120mm
spindle if it was configured as a double or a 126mm spindle if a
triple. The crankarm forgings were identical. Conversely, a double
crank might use a 118mm spindle on a road bike with minimal
clearances, while double on a touring bike might use a 122mm spindle
to clear splayed chainstays.

The variety of spindle lengths allowed an intelligent mechanic to
fine-tune the spindle length to the application or the rider. The rise
of specific spindle lengths for particular cranksets is a late
invention, and not a particularly welcome one, IMO.

Jeff

Still it seems to me that every RH crank could have the offset of the
innermost or outermost chainwheel printed on it. You would then
add/subtract the offset to/from half the spindle length to find the
chainwheel position from centerline.
???

(Dave) said:

Still it seems to me that every RH crank could have the offset of the
innermost or outermost chainwheel printed on it. You would then
add/subtract the offset to/from half the spindle length to find the
chainwheel position from centerline.

Many square taper spindles are asymmetrical.

Chalo Colina

[email hidden] (Chalo) wrote in message news:<[email hidden]>...

Quoted message said:

(Dave) said:

Still it seems to me that every RH crank could have the offset of the
innermost or outermost chainwheel printed on it. You would then
add/subtract the offset to/from half the spindle length to find the
chainwheel position from centerline.

Many square taper spindles are asymmetrical.

Chalo Colina

Ok, but would any of them be so asymmetrical as to measurably affect
the seated crank position? Isn't that asymmetry merely an "anti-creep"
solution?

(Dave) said:

(Chalo) said:

Many square taper spindles are asymmetrical.

Chalo Colina

Ok, but would any of them be so asymmetrical as to measurably affect
the seated crank position? Isn't that asymmetry merely an "anti-creep"
solution?

I mean that the distance from the bearing race to the taper is
different on each end of many spindles. Of course this makes one
crank arm naturally sit further outboard than the other. Don't ask me
why this is desirable; I don't know.

Chalo Colina

[email hidden] (Dave) wrote in message news:<[email hidden]>...

Quoted message said:

Still it seems to me that every RH crank could have the offset of the
innermost or outermost chainwheel printed on it. You would then
add/subtract the offset to/from half the spindle length to find the
chainwheel position from centerline.
???

Well, you'll just have to invent a time machine, go back 30 years, and
convince all the crank manufacturers to stamp this information on
their beautifully finished forgings.

In my experience, it's easier to simply make an intelligent estimate,
put the parts together, and then adjust with a longer/short spindle as
necessary. This is what I was taught and practiced for many years.

What problem are you trying to solve, anyway?

Jeff

[email hidden] (Jeff Wills) wrote in message news:<[email hidden]>...

Quoted message said:

[email hidden] (Dave) wrote in message news:<[email hidden]>...

Quoted message said:

Still it seems to me that every RH crank could have the offset of the
innermost or outermost chainwheel printed on it. You would then
add/subtract the offset to/from half the spindle length to find the
chainwheel position from centerline.
???

Well, you'll just have to invent a time machine, go back 30 years, and
convince all the crank manufacturers to stamp this information on
their beautifully finished forgings.

Well, they are only too happy to put the stupid crankarm length on
there, which is rather useless since you can easily measure it
yourself.

Quoted message said:

In my experience, it's easier to simply make an intelligent estimate,
put the parts together, and then adjust with a longer/short spindle as
necessary. This is what I was taught and practiced for many years.

What problem are you trying to solve, anyway?

Just replacing BB stuff. I was hoping it wasn't always done by trial
and error.