Vintage DD turntables. Are we living dangerously?

Halcro
We have been thru the thermal expansion thing already. As I stated some months back, with an aluminium chassis, the change in spindle to arm distance due to delta temp is very small. Dover is correct, it is no where near a "few millimeters"
Of course the shelf on which you place your TT isn't immune to dimensional changes due to temperature. Don't know the material you use, but the change is also likely to be insignificant.

Cheers.

a piece of aluminium 255mm will only expand by 0.0587mm for a 10 centigrade temperature change according to my calculations.

You're correct Dover. Quite small but as record grooves are in the order of microns...I wouldn't be boasting about this concept as you and Lewm do.
The tonearm vibration is a more serious issue however.

BTW...it's not often an architect gets to design a bridge.

Halcro - indeed it is quite something to have designed a bridge. When you mentioned designing a bridge in your earlier posts I thought you were a dental technician, until I found out that you were an architect. I studied engineering at university and most architects only do a couple of basic engineering papers for their degree in New Zealand.
As regards vibration - yes I agree it is an issue. The Final uses a superplastic zinc alloy chassis base that dissipates any vibration between 10 & 100hz at room temperature internally at a molecular level. Both the platter and arm pod are bolted to this SPZ energy sink to achieve both loop rigidity and deal with vibration. 

Dover,
When I graduated in 1970, a University Architecture degree in Sydney was 5 or 6 years of full-time study with Structural Engineering being a compulsory subject for each and every year.
But it was really 40 years of professional practice consulting and co-ordinating with all the relevant engineers (Geo-Tech, Structural, Civil, Hydraulics, Mechanical, Electrical, Acoustical) that taught me more than a mere 6 years of university study ever could...😎
I'd appreciate it if you could send me the Post where I said I had designed a bridge....as I haven't and I don't believe I wrote it? As I said.....very few bridges are designed with the input of an Architect.

When you say you studied engineering at university....did you graduate? 

Halcro - Yes in finance - switched to finance after a couple of years, decided engineering was not for me. I should have done an architectural degree in hindsight as that interests me more than civil engineering. Cheers.