Vintage DD turntables. Are we living dangerously?

The L07D is a system, using several different metals (stainless steel, alu, brass) with different temperature coefficients of expansion,

The basic frame of the L-07d shown in my attachment is cast aluminium which has twice the expansion co-efficient of steel.
For every centigrade degree change of room temperature (and unless your room is fully air-conditioned 24/7 the variation can easily be 5 degrees C)...there is clearly change in the distance between the spindle and tonearm pivot of several millimetres which is disastrous in the scale of vinyl groove information extraction.
Now please tell me Lew....what is the exact "drift of alignment" of my fully outboard armpods?

Henry, Come back to me with actual numbers to describe the possible change in mounting distance, given what you perceive to be the problem. My listening room varies in ambient temp by about 4 F degrees, from 68 to 72. According to my calculation, the fractional expansion of an alu bar (which this is not) would be .000052 (4 times 13*10^6, using the inches/F coefficient) over this 4 degree F span of temperatures. Further, the aluminum yoke embraces a stainless steel and brass pod (yes, a heavy and damped pod like yours, except it does not touch the shelf) that in turn embraces the vertical shaft of the tonearm in a clamping collet (not with a flimsy set screw). The alu is constrained from expanding and contracting by the bond between it and that pod plus the fact that it is also surrounded by the concrete-like material that constitutes the plinth itself. In other words, your critique of the L07D is off the mark, at best, and a sidebar to the central question. But let's stop here; I am OK with your belief structure; it has no effect on me whatever, and I am sure your music sounds just fine. This is all about splitting hairs anyway.

Dear Thuchan, I may be wrong in my assessment of the top line MS tonearm mounts; I have only ever seen them in photos. Possibly they are more rigid than they appear to be. If so, my apologies.

Good one Halcro, this debate gets funnier by the minute. Assuming the Kenny was set-up and then played at room temp, there should be virtually no discrepancy in distance. 70°F = 21.1°C, and 79°F = 26.1°C (for those of us...). Is that enough to cause several mm change?

Still, the point is made and it seems valid, at least to me. Why is it better to have arm and platter joined at the hip? Potential for extraneous interactions seems greater, not less.

The linear temperature coefficient of expansion of Aluminium is 0.000023m/m degrees C and is indeed approx. double that of steel.
Using this figure on a LO7D and assuming a 5 degree C delta, we get a change in distance to spindle of around 0.04mm. (approx 1.6 thou inches) Further the arm is lengthening and shortening relative to the ambient temp. This would somewhat mitigate the distance change.

Of course if one goes the pod way, the shelf's thermal expansion, contraction becomes the decider of the dimensional change.

The thermal expansion "problem" has been grossly overstated.

Richardkrebs
The thermal expansion "problem" has been grossly overstated.

So what are we left with,the stylus moving a 4 or 5lb pod?

Time to exit this carousel.