Micro SX-8000 II or SZ-1

The required figures are in the link provided above.

The motor / flywheel has an inertia of 5.1 x 10^-3 kg.m^2.

It turns at 750 rpm, so the inertia referred to the platter is multiplied by the square of the gearing ratio.

22.5^2 = 506.25 so the total moment of inertia = 506.25 x 5.1 x 10^-3 kg.m^2 which is 2.58 kg.m^2.

In the perfectly ridiculous unit of tonnes.cm^2 this is indeed nearly 26.

Thanks Raul. I remember that number now (which I bet is for platter only; the motor flywheel would add another 8-10% to that number for the SZ-1). I think the Verdier and the highest-end Final Audio tables may have a higher moment of inertia (as would the table that Dertonarm put together a while ago) because of slightly massier platters, but it wouldn't be too much bigger (in the case of the Verdier at least) and I could probably suffer through ownership of the SZ-1...

Wonder why more people don't build dual-voltage motors (one high-voltage motor rim drive motor for start-up and another for maintaining speed on a belt drive). If you did that, you could run a VERY big flywheel and use the outside of your flywheel as your belt pulley, which would mean that you'd largely eliminate the belt tension issue (which Mark Kelly has written about). And this, in turn, makes me think back to the big thread about massy platters, belt drive vs DD, and alternate drive mechanisms that got reasonably technical.

T-bone

The problem with that idea (besides complexity) is that you lose most of the advantage of running an external flywheel because your gearing ratio is much reduced. Using the effective mass analogy as given above, a 5 kg flywheel of 150mm diameter coupled "outside to outside" would add about 3 kg of effective mass to the platter.

As a contrast, the motor arrangement in the "Saskia" table adds an effective mass of about 85 kg.

In any case there are other ways of addressing the limitations of belt drives regarding creep (which is what I assume you mean by "the belt tension issue". There will be a completely new take on the issue exhibited at RMAF come October if everything goes to plan.


Mark Kelly

The system seems to have eaten the post on equivalent mass, so I'll do another.

The idea is analogous to the method of calculating equivalent mass for tonearms and the calculation is the same: divide the moment of inertia by the square of the radius of action, the result being an equivalent mass.

Using a standard radius of action of 150mm, the equivalent mass of the flywheel arrangement for the Micro Seiki is 2.58 kg.m^2 / (0.15m)^2 giving 115 kg.

Note that due to distribution of mass, a TT platter would have to be about 200 kg to achieve this equivalent mass.


Mark Kelly

Lewm, of course you need to see both units in person to have a better decision-bases. Nevertheless the solid buttons of the RY-5500 II and their haptics are a statement of High-Quality engineering and machine building I do not see at the SZ-1m so far.

The link Pcosta provided gives a very good picture of the unit and of the buttons. What matters more than taste of design is the in-built fly-wheel concept and the air bearing of the SZ-1m which T-Bone has described. Maybe I should look for an extra fly-wheel unit for the 8000.