I did several of these back in the 80's to make 24 speed tandems. I used a standard triple on the inside of the arm and a single chain ring on the outside. If memory serves, the outer was one of those that was drilled for the large bolt circle (I think they only went down to ~45 teeth) I bolted the centers of the two outers together, and drilled the inner outer to match the outer outer. Used standard bolts and spacers. Worked great with a minimum of modifications and was really rigid. I remember it did take a while to figure out what order to install the bolts in. I used an extensively modified Cyclone FD as it was the only thing that would make the throw back then.
Bill Boston Dark in Wilmington, DE Snow should get here about the same time as the sun maybe!
> theres a smallish, but still descernable, pic of a TA quad at:
>
> http://www.bikecult.com/
>
> its described there as a "tandem triple".
>
> granted, not 4 drive chainwheels (tandem, right side linkage), but
> its still a quad...
>
> cant tell if its set up with 2 outers or 3 inners...
>
> -joel
>
> >Roy Drinkwater wrote:
> >>
> >> Steve Kistler commented:
> >>
> >> >His [Bob Freeman] vast expertise advised me against trying to
> >> >build a Quad TA crank! out of the Paramount's exising TA triple.
> >> >How to make a TA quad crank??? Bob said expensive and rare
> >> >parts? Suggestions?
> >>
> >> Well, it's just long bolts and spacers. Harvey Sachs has
> >> probably done one. The major problem is that the smallest ring is
> >> 26T.
> >
> >Not even extra long bolts, just two sets of regular TA triple bolts. I
did
> >one in about '77 for a front-drive tandem. I used two outer rings, which
> >attached to the front and back of the 5-pin "spider" with double
chainring
> >bolts. Then two inner rings of course. One set of triple bolts went
> >through the outer three rings at the 36-tooth bolt circle (sorry I don't
> >know the BCD); the other set of triple bolts went through the inner three
> >rings at the 26-tooth bolt circle. Made a very rigid and useful 26-56
tooth
> >quad - the 56 was nice to have due to the 650b wheels on this bike. Had
to
> >do some drilling of course, the only tricky part.
> >
> >
> >Mark Bulgier
> >Seattle, Wa
> >USA
> >_______________________________________________
>
>
> --
> joel metz : magpie@messengers.org : http://www.blackbirdsf.org/
> bike messengers worldwide : ifbma : http://www.messengers.org/
> po box 191443 san francisco ca 94119-1443 usa
> ==
> i know what innocence looks like - and it wasn't there,
> after she got that bicycle...