RE: [CR] Measured data, Was Re: Campag 3-arm Crank?

(Example: Component Manufacturers:Campagnolo)

From: "Ken Freeeman" <>
To: <>
Subject: RE: [CR] Measured data, Was Re: Campag 3-arm Crank?
Date: Wed, 23 Feb 2005 08:03:15 -0500
In-Reply-To: <>
Thread-Index: AcUZZrq5lNaiQTMpRn6oANiZuCzRjAAQSE+Q

If I recall both of my chainwheels on the FB crank were on the same bolt set.

Ken Freeman Ann Arbor, MI

-----Original Message----- From: [] On Behalf Of r cielec Sent: Wednesday, February 23, 2005 12:16 AM To:; Classic Rendezvous Subject: Re: [CR] Measured data, Was Re: Campag 3-arm Crank?

What about the small ring ? Richard Cielec Chicago, Illinois wrote: In a message dated 2/22/2005 3:18:23 PM Eastern Standard Time, writes: I am sorry to say that this is amiss. The distance between bolts (c-c) on threearm cranks is half the bcd times the root of three which is 1.7320508

My 116 mm bcd cranks then have a c-c distance of 100.45894 mm. If I measure them I get 100 mm, near enough. Your distance of 112 would give a bcd of 130 mm which sounds very modern but makes me doubt your measurements.


Olof Stroh Uppsala Sweden

Olof, you are correct, thank you. I mis-converted the 10.2cm that I was reading with a tape measure to 112, instead of 102mm ... and then never looked back as I landed in the same position from crank to crank (metric is a second language). Should have taken the extra steps to retrieve the digital calipers. I maintain that I am a nice guy, but not necessarily the sharpest knife in the drawer :)

The 102mm by my eye, as you say, was close enough to the 100.46~ from bolt to bolt that you noted. So, I placed one Campagnolo crank upside down underneath the other and reversed the crank direction in order to simulate a measurable 116 BCD, pictured here:

Click on the pic to view a huge version, if y'all dare.

Below, I amend my post copy to read more correctly

---- Original Message -----

From: To: Cc: ; ; ; ; Sent: Tuesday, February 22, 2005 8:41 PM Subject: Re: [CR] Measured data, Was Re: Campag 3-arm Crank? Ok, I have a good handful of misc. 3 spider arm cranks on various bikes, so I went down and took some measurements. Turns out I have 11 different varieties, and 9 of them measure the same! I measured simply from one bolt center to the next, and the approx. 102mm results sound like the 100.46mm, or 116 BCD that Olof mentioned (still dunno how to measure BCD accurately on an assembled and mounted crank).

(Note: for all my photo names and dating, "~" after the date means "approx.")

1955~ Magistroni with "circus tent" logo - on a Torpado - STEEL 100.46mm 1959~ Magistroni with Torpado logo engraving - STEEL 100.46mm 1961~ Magistroni with "circus tent" logo, from an Olmo Special - STEEL 100.46mm Bike boom, No name, from a Coppi low end - STEEL 100.46mm Bike boom, No name French, from a gaspipe Regina - STEEL 100.46mm Early 70s? Campy w/ French b.b, from a Cilo - STEEL crank/ALUMINUM rings 100.46mm 1972~ No name, believed to be Nervar on Italvega - STEEL 100.46mm 1974~ TA with black anodized rings, from mix/match Italvega - ALUMINUM 100.46mm 1975 Campy G.S. - ALUMINUM 100.46mm 1975~ Sugino Maxy, fixed big ring holds 3 bolt sm. ring, on a Sekine - ALUM 93mm Late 70s? Shimano 600 on a mix/match 3Rensho Sup.Rec.EXP. - ALUMINUM 83mm

And what I forgot to mention, was this is confirmation that Campy aluminum 3 hole rings are the same BCD as the steel ones.

Ciao, Mark (back to tape measure school) Agree Southfield MI ~ ~ ~


Do you Yahoo!?
Yahoo! Mail - Helps protect you from nasty viruses.