i am assuming you are making reference to the ref:ra203 outer chainwheel:
http://www.blackbirdsf.org/
which is intended to mount to ta pro 3 attaches (or other 3-arm, 116mm bcd crankarms) and have ta 6-pin 116mm bcd "randonneur" inner chainwheels mounted to it.
those 3 tabs are plain holes, untapped.
-joel
At 19:52 -0600 08.22.2006, Bob Hanson wrote:
>Jerry,
> Sorry, but my scanner is in the crapper.
>
>The one place that I've seen this actually illustrated is in Chuck
>Schmidt's reproduction of the 1963 Ron Kitching Catalogue. Perhaps
>someone can share a scan of page 10 with everyone.
>
>What the illustration shows, is a large outer chainring with an inner
>band linking the 6 arms and right at the ring/arm intersections the 6
>holes are drilled through. Then within 3 of the 6 trapezoid windows
>between the arms, there are short 'tangs' extending inward.
>
>Before examining that very small illustration for a second time [just
>now], it had assumed these tabs must logically suggest that these 3
>connection points must have been allowed for fastening to a something
>with greater BCD than 116 mm. But, this does not appear to be the case,
>after all; they seem to be simply additional alloy material, added to
>furher support the drillings along the thin inner band. Yes, all 9
>holes appear to be right at the intersects with the band.
>
>So, this still raises the question: what the heck were 3 additional
>equidistant drillings needed for?
>
>I think that perhaps the other 3 were actually tapped / threaded holes,
>or at least bored in a different diameter than the other 6 - and were
>intended to better support an original 3-arm steel crank's threaded
>screws.
>
> ~ Just my guess.
>
>Bob Hanson, Albuquerque, New Mexico, USA
>
>_______________________________________________
--
joel metz : magpie@blackbirdsf.org : http://www.blackbirdsf.org/
bike messengers worldwide : ifbma : http://www.messengers.org/
magpie messenger collective http://www.magpiemessenger.com/
portland, oregon
==
i know what innocence looks like - and it wasn't there,
after she got that bicycle...