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Interesting thoughts, but I'm not sure I agree.....

I am familiar with the Lenco, Thorens and Garrard idler designs, not so much with the Russco and other idlers. I have seen pictures of the recent designs but have not heard them.

But, to go back to basics, let's consider WHY idlers designs were used in the first place. I think the reason is that, in the absence of electronic motor controls, they were designed to allow the possibility of changing platter speeds. The Thorens and Garrard allowed limited speed change by using magnetic braking, and the Lenco of course used a tapered spindle system for infinitely variable speed change. IIRC the first electronic speed change was the Thorens TD125 which used a DC motor and electronic speed control. Of course, direct drives also use electronic speed change.

However, back in the fifties and sixties, AC power basically meant one motor speed. Belt drive could do different platter speeds by manually or mechanically moving a belt from one pulley size to the next. Idler did it by mechanically moving a idler wheel from one pulley size to the next, or, on the Lenco, moving the wheel along a tapered spindle, with the pulley or spindle being directly attached to the motor. The idler itself provided a 1:1 drive, so there was no torque transformation.

The only other rationales I can see for having an intermediate idler are 1) possible noise isolation, although the "stiffer" the idler the less the noise isolation, and 2) to allow the idler to be disengaged from the platter when it was off to prevent flat spotting, which is a known problem with the Garrard 301/401, and to some extent with the plastic wheel Lenco - the metal wheel Lenco has a thin rubber coating and is reported to be largely immune to this problem.

Thus, if you can change speeds electronically, that removes one reason for needing an intermediate idler. If the motor is sufficiently quiet, that removes the second reason. If the pulley can be designed with sufficient friction to drive the platter directly, but stiff or resilient enough to prevent flat spotting that removes the third reason. Therefore, I see no obvious reason from a design standpoint why a rim drive with the motor driving the rim "directly" via a pulley/wheel would have to be a "cheapy" or "inferior" solution to using an intermediate idler. In fact, theoretically, either an idler or a belt introduces a potential source of "slop" in the system. The overall results would still depend on the implementation, as is usually the case.

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