Interesting picture, but different from my GS three arm,' 77 ? Mine has two sets of mounting holes in the large ring. The large ring bolts to the spyder, with 11mm hex nuts on the rear, and smaller 6mm (thread) bolts and spanner type nuts for the smaller ring, which bolts directly to the large ring, with a spacer to account for the spyder thickness. The large ring uses the smaller diameter bolt circle, 100cm c-c, and the larger diameter bolt circle measures 127cm c-c. Sorry, no way am I trying bcd for this. I lost my protractor. There is not enough material on the 42t ring to enlarge the holes, or at least I wouldn't !
If I can get our camera working will try for pictures later.
From: Mark Stonich <email@example.com>
To: Jerome & Elizabeth Moos <firstname.lastname@example.org>,email@example.com
Subject: Re: [CR]More on 3-arm chainrings
Wed, 01 Aug 2007 07:39:09 -0500
>At 11:36 PM 7/31/2007, Jerome & Elizabeth Moos wrote:
>> Does anyone have any firsthand information about the
>>compatibility of Campy 3-hole rings with TA, Stronglight or Nervar
>36-46 Stronglight rings on steel Campi 3 pin arms. I don't remember
>what bolts I used, but the are longer than Campi. I also have a set
>of alloy 3 pin Campi arms. and the original chainrings from both
>sets. The crankarm/chainring interface is the same 9mm hole.
>If I didn't have the bolts, and was mixing brands, (so originality
>wasn't an issue) I'd get out my trusty 10mm drill bit and make the
>rings and arms compatible with modern 10mm bolts.
> BikeSmith Design & Fabrication
> 5349 Elliot Ave S. - Minneapolis. MN 55417
> Ph. (612) 824-2372 http://bikesmithdesign.com