> First, let me agree strongly that the TA "cyclotourist" units had
> design defects. The business of 6 spindly arms supporting a large
> chainring can be best described as "nuts."
If you had it set up as a triple, those "six spindly arms" would have to
support all three rings!
> My touring bike of the era had such an arrangement, and the middle
> cog warped backwards substantially, while remaining nicely in plane.
I've never had that problem, but I'm much more a spinner than a masher.
As evidenced by the 45-49T large rings on my bikes -- I found I never
used the higher gears so I got rid of them.
> For the next set-up, I installed a supplementary ring of machine
> screws and spacers, at the radius used for one of TA's other styles.
> I used flat-head machine screws, head outside, and the slight nub of
> the 1/2" screws that stuck out to the inside was easily filed off.
> Never had a warp again - but maybe I was getting older and weaker.
Some of the larger TA outer rings were double-drilled to allow bolts both at the smaller Cyclotouriste attachment point (accommodating rings down to 26T) and the larger Criterium (44T minimum) attachment point. You'd have double the bracing on each arm, at least for inner rings >44T.
-John Thompson (email@example.com)
Appleton WI USA