How much do cranks expand by?

"Pete Biggs" wrote: (clip) How much does the hole enlarge by when the crank
is correctly fitted, and how can the amount be measured or calculated?
^^^^^^^^^^^^^^
First, I would measure the taper. Then I would hand seat the crank on the
taper, and count the turns of the screw required to bring the crank to
appropriate tightness. From the thread pitch, you can calculate how far it
moved up the taper. Knowing that, you can figure how much the taper
expanded the crank. (Assume the tapered square shaft, being steel, does not
compress.

Pete Biggs said:

I'm trying to convince someone that cranks expand as they are fitted on
square tapered spindles.

How much does the hole enlarge by when the crank is correctly fitted, and
how can the amount be measured or calculated?

The hole will expand, and the spindle will compress. Both aluminium and
steel (or titanium) are "elastic" materials and are placed under
"stress" by the bolt and the taper, and therefore experience "strain".
How much? Somewhere between "just a little" and "not a lot". It should
be calculable (with more effort than I'm prepared to put in ;-) If you
happen to have a class of mechanical engineering students handy this
would be an interesting question to set them.

You could try asking in rec.bicycles.tech where Jobst Brandt may have an
answer. (And a lot of fools will have wrong answers...)

As a wild guess, you probably couldn't measure it with a conventional
micrometer, or only just.

Mike

Mike Causer said:

The hole will expand, and the spindle will compress. Both aluminium
and steel (or titanium) are "elastic" materials and are placed under
"stress" by the bolt and the taper, and therefore experience "strain".
How much? Somewhere between "just a little" and "not a lot". It
should be calculable (with more effort than I'm prepared to put in
;-) If you happen to have a class of mechanical engineering
students handy this
would be an interesting question to set them.

You could try asking in rec.bicycles.tech where Jobst Brandt may have
an answer. (And a lot of fools will have wrong answers...)

As a wild guess, you probably couldn't measure it with a conventional
micrometer, or only just.

Thanks Mike. Enough expansion to make count as an interference fit,
would you say?

Buy the way, this *is* r.b.t! :-)

~PB

Pete Biggs said:

Thanks Mike. Enough expansion to make count as an interference fit,
would you say?

It's an interference fit for sure, but not in the traditional
engineering sense. Tightening the bolt does it, whereas a "proper"
interference fit comes from the slight overlap of the unforced sizes of
the two components. I did have a quick look at Machinery's Handbook,
but it doesn't appear to cover bicycle tapers. For any real calculation
I'd have to dig out my college textbooks, which haven't been opened in
the last 35 years ;-(

Quoted message said:

Buy the way, this *is* r.b.t! :-)

Ahhh, yes. In traditional usenet fashion I noticed a split second after
sending the reply. I'm used to seeing your name on uk.rec.cycling, and
I assumed (silly boy!) that's what I was reading....

Mike

Pete Biggs said:

I'm trying to convince someone that cranks expand as they are fitted
on square tapered spindles.

Quoted message said:

How much does the hole enlarge by when the crank is correctly
fitted, and how can the amount be measured or calculated?

Quoted message said:

If a specific example is needed: Campagnolo Veloce.

These use an ISO square taper seems to be 1:15 or so and the crank
bolt has a 1mm pitch. Assuming you push the crank on manually as far
as it will go, you'll get 0.0666mm expansion with every rotation of
the bolt. The reason for this approximation is that the steel spindle
cannot readily compress and must extrude elastically axially like a
rubber rod grasped in hand. Steel having a higher modulus:

Al = 68.95 GPa
Fe = 196.50 GPa

So count the turns of the crank bolt and divide by 15 roughly
speaking, if I got the ISO standard correctly for square tapered
spindles. Maybe someone can check on that. I don't have the value
handy.

This is not a good joint and that's why people are looking for a
better way. See ISIS or Shimano's latest answer. It's not change for
change's sake but because cranks and spindles fail. I can swear by
that!

Jobst Brandt
[email hidden]

In article <[email hidden]>,

Quoted message said:

Pete Biggs writes:

Quoted message said:

Quoted message said:

How much does the hole enlarge by when the crank is correctly
fitted, and how can the amount be measured or calculated?

Quoted message said:

These use an ISO square taper seems to be 1:15 or so and the crank
bolt has a 1mm pitch. Assuming you push the crank on manually as far
as it will go, you'll get 0.0666mm expansion with every rotation of
the bolt.

Quoted message said:

This is not a good joint and that's why people are looking for a
better way. See ISIS or Shimano's latest answer. It's not change for
change's sake but because cranks and spindles fail. I can swear by
that!

I know you have mentioned that you get around this by inspecting your
cranks assiduously, and that you have mentioned specific
_implementations_ of ISIS with design flaws.

So, the question is, when you get your bike upgraded to a threadless
stem, will you also add an ISIS or Hollowtech II crank and BB?

--
Ryan Cousineau, [email hidden] http://www.wiredcola.com
Verus de parvis; verus de magnis.

i have two sets, one steel one aluminum
of l980's metallurgy-the aluminum set is a fancy SR,(rumour has it
that this one is worth $250 today-no more standing around the lathe
for $1/hr) the steel a lesser variety but still in today's $100-76 'no
stinking ramps' range.
each CR appears to last maybe 10,000 miles with two-three rebuilds a
year and maybe 6 or 7 reasins to pull the cranks off.
Ima no,well almost,gaulling mechanic.
the cranks, as JB maths, do expand even with a light touch-i see more
than a 32nd" up to an 8th" on the steel crank that works loose: one of
four!?
that's over two-three years. I was surprised to see this happen.
we use anti-seize!

Ryan Cousineau said:

Quoted message said:

Quoted message said:

How much does the hole enlarge by when the crank is correctly
fitted, and how can the amount be measured or calculated?

Quoted message said:

Quoted message said:

These use an ISO square taper seems to be 1:15 or so and the crank
bolt has a 1mm pitch. Assuming you push the crank on manually as
far as it will go, you'll get 0.0666mm expansion with every
rotation of the bolt.

Quoted message said:

Quoted message said:

This is not a good joint and that's why people are looking for a
better way. See ISIS or Shimano's latest answer. It's not change
for change's sake but because cranks and spindles fail. I can
swear by that!

Quoted message said:

I know you have mentioned that you get around this by inspecting
your cranks assiduously, and that you have mentioned specific
_implementations_ of ISIS with design flaws.

My crank failures WERE at the pedal eye. The Square tapers had all
been detected as cracks beginning at the corners but never an advanced
one that could cause failure soon. I've fixed the pedal eye problem
but I'll have to defer to MFr's for the spindle.

Quoted message said:

So, the question is, when you get your bike upgraded to a threadless
stem, will you also add an ISIS or Hollowtech II crank and BB?

I've been using a threadless stem for some time now but that doesn't
do anything for the BB.

Jobst Brandt
[email hidden]

Thanks for the replies.

What about carbon cranks (square taper type)? Does the Al insert expand
as usual? What happens to the carbon surrounding it if so?

~PB

[email hidden] wrote in message ...

Quoted message said:

Pete Biggs said:

I'm trying to convince someone that cranks expand as they are fitted
on square tapered spindles.

Quoted message said:

How much does the hole enlarge by when the crank is correctly
fitted, and how can the amount be measured or calculated?

Quoted message said:

If a specific example is needed: Campagnolo Veloce.

These use an ISO square taper seems to be 1:15 or so and the crank
bolt has a 1mm pitch. Assuming you push the crank on manually as far
as it will go, you'll get 0.0666mm expansion with every rotation of
the bolt. The reason for this approximation is that the steel spindle
cannot readily compress and must extrude elastically axially like a
rubber rod grasped in hand. Steel having a higher modulus:

Al = 68.95 GPa
Fe = 196.50 GPa

So count the turns of the crank bolt and divide by 15 roughly
speaking, if I got the ISO standard correctly for square tapered
spindles. Maybe someone can check on that. I don't have the value
handy.

This is not a good joint and that's why people are looking for a
better way. See ISIS or Shimano's latest answer. It's not change for
change's sake but because cranks and spindles fail. I can swear by
that!

Jobst also adheres to grease lubrication of the taper, so forces the crank
too far with the recommended torque figure.

Trevor

In article <[email hidden]>,

Quoted message said:

Ryan Cousineau writes:

[square-taper BB spindles]

Quoted message said:

Quoted message said:

Quoted message said:

This is not a good joint and that's why people are looking for a
better way. See ISIS or Shimano's latest answer. It's not change
for change's sake but because cranks and spindles fail. I can
swear by that!

Quoted message said:

I know you have mentioned that you get around this by inspecting
your cranks assiduously, and that you have mentioned specific
_implementations_ of ISIS with design flaws.

My crank failures WERE at the pedal eye. The Square tapers had all
been detected as cracks beginning at the corners but never an advanced
one that could cause failure soon. I've fixed the pedal eye problem
but I'll have to defer to MFr's for the spindle.

Quoted message said:

So, the question is, when you get your bike upgraded to a threadless
stem, will you also add an ISIS or Hollowtech II crank and BB?

I've been using a threadless stem for some time now but that doesn't
do anything for the BB.

Ah. I didn't realize you had upgraded; last I remember on this subject,
you had merely said you were planning to.

You may also be interested in this recent memo from FSA, which explains
in fascinating detail one of their designers' views on the separate
issues of crank-BB joints and BB bearings (in short, he seems quite
concerned that virtually all pipe-spindle designs, including
FSA-promoted ISIS, don't have enough room in the BB shell for ordinary
bearings because the spindles are too big):

http://velonews.com/tech/report/articles/6799.0.html

They have plans for something called "MegaExo," which sounds like
another pinch-bolt external-bearing crankset (we can say that when
talking about integrated crank/BBs, right?).

Special bonus insanity: Osymetric chainrings. I can't remember whether
this design is Biopace or anti-Biopace style:

http://velonews.com/tech/report/articles/6807.0.html

Their site:
http://www.osymetric.com/

--
Ryan Cousineau, [email hidden] http://www.wiredcola.com
Verus de parvis; verus de magnis.

Quoted message said:

Special bonus insanity: Osymetric chainrings. I can't remember
whether this design is Biopace or anti-Biopace style:

http://velonews.com/tech/report/articles/6807.0.html

The VeloNews article states:

Quoted message said:

Quoted message said:

designer Jean-Louis Talo was clear to point out that
his patented out-of-round chainrings are considerably
different that Shimano's original Biopace and
Biopace II chainrings.

Talo's "Osymetric" chainring is just another resurrection of the
hundred-year-old idea of the elliptical chainring, except that instead
of being elliptical, it looks to be four circular segments of different
radii.

--
"Bicycling is a healthy and manly pursuit with much
to recommend it, and, unlike other foolish crazes,
it has not died out." -- The Daily Telegraph (1877)

Ryan Cousineau wrote in message ...

Quoted message said:

In article <[email hidden]>,

Quoted message said:

Ryan Cousineau writes:

[square-taper BB spindles]

Quoted message said:

Quoted message said:

> This is not a good joint and that's why people are looking for a
> better way. See ISIS or Shimano's latest answer. It's not change
> for change's sake but because cranks and spindles fail. I can
> swear by that!

Quoted message said:

I know you have mentioned that you get around this by inspecting
your cranks assiduously, and that you have mentioned specific
_implementations_ of ISIS with design flaws.

My crank failures WERE at the pedal eye. The Square tapers had all
been detected as cracks beginning at the corners but never an advanced
one that could cause failure soon. I've fixed the pedal eye problem
but I'll have to defer to MFr's for the spindle.

Quoted message said:

So, the question is, when you get your bike upgraded to a threadless
stem, will you also add an ISIS or Hollowtech II crank and BB?

I've been using a threadless stem for some time now but that doesn't
do anything for the BB.

Ah. I didn't realize you had upgraded; last I remember on this subject,
you had merely said you were planning to.

You may also be interested in this recent memo from FSA, which explains
in fascinating detail one of their designers' views on the separate
issues of crank-BB joints and BB bearings (in short, he seems quite
concerned that virtually all pipe-spindle designs, including
FSA-promoted ISIS, don't have enough room in the BB shell for ordinary
bearings because the spindles are too big):

Only with graded parts could a BSA type axle be made successful. How come
its taken so long to realise the difficulties of using cartridge bearings?

Trevor

Trevor said:

Only with graded parts could a BSA type axle be made successful. How come
its taken so long to realise the difficulties of using cartridge bearings?

The "Thompson" BB used on some cheap bikes and BMX machines (cups
pressed into the frame, cones screwed to the axle) is *theoretically* a
superior design. The BB shell is larger and the axle is better
supported with the cones on the outside; it's like a hub except the
shell is stationary and the axle [1] rotates. Unfortunately the sealing
is nearly always dreadful due to the huge circumference of the cone/cup
joint, and I've never seen an attempt at making a high-quality one.

Here's a picture of one:
http://www.engr.utk.edu/~tsaleh/bike/Thompson/thompson.html

[1] technically the BB has a "spindle" because it spins, and the hub has
an "axle" - I think.

Zog The Undeniable wrote in message <4130e8ef.0@entanet>...

Quoted message said:

[1] technically the BB has a "spindle" because it spins, and the hub has
an "axle" - I think.

I don't like the word spindle for this use as it has connotations to sewing
machines. Sewing machine manufacturers were the first to take up production
line of the bicycle. I consider spindle inappropriate for this highly
loaded component.

Trevor

Quoted message said:

Zog The Undeniable wrote in message <4130e8ef.0@entanet>...

Quoted message said:

[1] technically the BB has a "spindle" because it spins, and the hub has
an "axle" - I think.

Trevor said:

I don't like the word spindle for this use as it has connotations to sewing
machines. Sewing machine manufacturers were the first to take up production
line of the bicycle. I consider spindle inappropriate for this highly
loaded component.

Who made you the Red Queen?
It's a spindle.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

A Muzi said:

Quoted message said:

Zog The Undeniable wrote in message <4130e8ef.0@entanet>...

Quoted message said:

[1] technically the BB has a "spindle" because it spins, and the hub has
an "axle" - I think.

Trevor said:

I don't like the word spindle for this use as it has connotations to sewing
machines. Sewing machine manufacturers were the first to take up production
line of the bicycle. I consider spindle inappropriate for this highly
loaded component.

Who made you the Red Queen?
It's a spindle.

Dear Andrew,

And so is this heavily loaded 117mm item:

http://www.dosecc.org/html/body_rigspecs.html

Trevor's logic resembles the peace of God, as Mark Twain
remarked in "Roughing It."

First, Trevor tells us that he dislikes using the word
"spindle" for a bicycle part because it is connected with
sewing machines in his mind.

(Presumably true.)

Next, he tells us that sewing-machine makers were the first
companies to produce bicycles.

(This connection is probably true.)

Finally, he concludes that since sewing-machines and
bicycles were once made by the same companies, it is wrong
to use sewing-machine terms for bicycles.

(Non sequitur--it is precisely because different things are
connected that we use the same words and roots to describe
them.The pedal that we push on employs the same "ped- "
found at the end of our legs that we use as pedestrians.[1])

If we applyTrevor's linguistic reasoning about the
now-lapsed connection between bicycles and sewing companies,
then we must conclude that the phrase "sew-ups" should not
be used in polite company.

Carl Fogel

[1] Pedantry, on the other hand, springs from "paed-," which
meant child--a pedagogue instructed children, if a recursive
footnote (and two--no, three footling puns) may be peddled
here.

In article <[email hidden]>,

Trevor said:

Zog The Undeniable wrote in message <4130e8ef.0@entanet>...

Quoted message said:

[1] technically the BB has a "spindle" because it spins, and the hub has
an "axle" - I think.

I don't like the word spindle for this use as it has connotations to sewing
machines. Sewing machine manufacturers were the first to take up production
line of the bicycle. I consider spindle inappropriate for this highly
loaded component.

Trevor

The shaft of a milling machine is also known as a spindle and it is
quite heavily loaded.

--
B.B. --I am not a goat! thegoat4 at airmail.net

Trevor said:

Only with graded parts could a BSA type axle be made successful. How come
its taken so long to realise the difficulties of using cartridge bearings?

Probably because they came from the same fresh vein of imagination as your
aquaplaning bicycle which periodically springs into the air for no reason.
--
David Damerell <[email hidden]> Kill the tomato!