tapered square standards

Discussion in 'Cycling Equipment' started by Martin Trautman, Feb 11, 2003.

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  1. 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
     
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  2. On 11 Feb 2003 13:00:29 GMT, Martin Trautmann wrote:
    > 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

    oops - I feel that in general the angel is not given in total, put per side. Thus the angle will be
    arc sin ((W_o - W_i) / 2 L) = 2 deg

    > 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.

    from news:<[email protected]> I found:

    ISO: L_right = 18 +0.5/-0 mm L_left = 16 +0.5/-0 mm

    Dimension across flat 1.5mm from end: 12.6mm +0.02-0.05 Spindle end to bolt seat: Loose: 3mm
    Tightened: 1.5mm min. Crank fixing threads: Bolt-type M8x1 Nut-type M10x1.25 Crank bolt or nut
    size 14mm Dustcap threads M22x1

    what/where are crank fixing threads?

    Best regards Martin
     
  3. In article <[email protected]>, Martin Trautmann <[email protected]> wrote:
    >
    >from news:<[email protected]> I found:
    >
    >ISO: L_right = 18 +0.5/-0 mm L_left = 16 +0.5/-0 mm
    >
    > Dimension across flat 1.5mm from end: 12.6mm +0.02-0.05 Spindle end to bolt seat: Loose: 3mm
    > Tightened: 1.5mm min. Crank fixing threads: Bolt-type M8x1 Nut-type M10x1.25 Crank bolt or nut
    > size 14mm Dustcap threads M22x1
    >
    >what/where are crank fixing threads?

    It's the bolt or nut that holds the crank arm on. Most are bolt-style today. M8x1 is the size used
    on square-taper spindles.

    --Paul
     
  4. On Tue, 11 Feb 2003 14:52:56 GMT, Paul Southworth wrote:
    > In article <[email protected]>, Martin Trautmann <[email protected]> wrote:
    > >
    > >from news:<[email protected]> I found:
    > >
    > >ISO: L_right = 18 +0.5/-0 mm L_left = 16 +0.5/-0 mm
    > >
    > > Dimension across flat 1.5mm from end: 12.6mm +0.02-0.05 Spindle end to bolt seat: Loose: 3mm
    > > Tightened: 1.5mm min. Crank fixing threads: Bolt-type M8x1 Nut-type M10x1.25 Crank bolt or
    > > nut size 14mm Dustcap threads M22x1
    > >
    > >what/where are crank fixing threads?
    >
    > It's the bolt or nut that holds the crank arm on. Most are bolt-style today. M8x1 is the size
    > used on square-taper spindles.

    Thanks - so the 14 mm is the outer width (the literal German translation would be key width) of the
    nut or six edge bolt.

    I was confused by standard non-bicycle versions, with 13 mm for M8 six edge bolts and 6 mm for M8
    Inbus / ISO 4762 or 17 mm for M10 nuts.

    Best regards Martin
     
  5. In article <[email protected]>, Martin Trautmann <[email protected]> wrote:
    >On Tue, 11 Feb 2003 14:52:56 GMT, Paul Southworth wrote:
    >> In article <[email protected]>, Martin Trautmann <[email protected]> wrote:
    >> >
    >> >from news:<[email protected]> I found:
    >> >
    >> >ISO: L_right = 18 +0.5/-0 mm L_left = 16 +0.5/-0 mm
    >> >
    >> > Dimension across flat 1.5mm from end: 12.6mm +0.02-0.05 Spindle end to bolt seat: Loose: 3mm
    >> > Tightened: 1.5mm min. Crank fixing threads: Bolt-type M8x1 Nut-type M10x1.25 Crank bolt or
    >> > nut size 14mm Dustcap threads M22x1
    >> >
    >> >what/where are crank fixing threads?
    >>
    >> It's the bolt or nut that holds the crank arm on. Most are bolt-style today. M8x1 is the size
    >> used on square-taper spindles.
    >
    >Thanks - so the 14 mm is the outer width (the literal German translation would be key width) of the
    >nut or six edge bolt.

    14mm is the size of the socket you use to tighten the bolt.

    15mm also exists but not as common.

    --Paul
     
  6. A Muzi

    A Muzi Guest

    "Martin Trautmann" <[email protected]> wrote in message
    news:[email protected]...
    >
    > 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)

    > T.A. 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
    >
    >
    >
    >
    >
    >

    That is an early variant of inexpensive square-taper crank, made when melt-forged aluminum cranks
    were new and the alloys weren't as developed as now. Those were made by Takagi and SR-Sakae. Some
    but not all sizes are still available as spares.

    It should have a marking for size, like possibly 3H, which would be a big help if you are looking
    for a new one.

    I can't do ascii art either, but I have a camera:
    http://www.yellowjersey.org/photosfromthepast/3SPINDLE.JPG Is it the one on the left?

    --
    Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971
     
  7. On Tue, 11 Feb 2003 22:10:05 -0600, A Muzi wrote:
    > That is an early variant of inexpensive square-taper crank, made when melt-forged aluminum cranks
    > were new and the alloys weren't as developed as now. Those were made by Takagi and SR-Sakae. Some
    > but not all sizes are still available as spares.
    >
    > It should have a marking for size, like possibly 3H, which would be a big help if you are looking
    > for a new one.
    >
    > I can't do ascii art either, but I have a camera:
    > http://www.yellowjersey.org/photosfromthepast/3SPINDLE.JPG Is it the one on the left?

    Yeah, I'd say so. How about the measured sizes of those models?

    Kind regards Martin
     
  8. On 11 Feb 2003 13:23:16 GMT, Martin Trautmann wrote:
    > > 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.
    >
    > ISO: L_right = 18 +0.5/-0 mm L_left = 16 +0.5/-0 mm
    >
    > Dimension across flat 1.5mm from end: 12.6mm +0.02-0.05 Spindle end to bolt seat: Loose: 3mm
    > Tightened: 1.5mm min.

    Yet another source claimed that the squares of Campa, Mavic and Stronglight (ISO) are smaller than
    Shimano and Suntour (JIS) with the result that JIS cranks will move about 4.5 mm further in.

    This may conflict with the end of the square and result in a loose fit or braking stress. for ISO
    cranks on JIS squares there's less contact area between crank and spindle, since the crank does not
    slip perfectly on the spindle. The result again is a higher risk of braking the crank.

    But assuming those 4.5 mm and 2 deg, ISO is about 0.3 mm smaller than JIS (2 * sin 2 * 4.5 = 0.3)?

    Kind regards Martin
     
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