Nipkow disc weight reduction holes?

[Viewmaster]

I am trying to find the time now to finish off my own NBTV. (too much time on still experimenting with that dear ol' Edikow! etc etc )

My disc is 12" dia aluminium.
Some say that one should reduce the weight by putting large holes in them.
Others say this may lead to wind turbulence and wobble?
So should I leave the Nipkow as a solid disc or not?
Has anyone had trouble either way with aluminium discs?
Thanks for any guidance.
Albert.

[DrZarkov]

My "test-televisor" has an aluminium disc with a diameter of 30 cm, and no holes for weight reduction. I'm using a common 12 V cassette-recorder motor (from an "Aiwa" tapedeck), without problems, the disc is mounted directly on the motor. I think the weight is an advantage in my case: my testing device has no sync, so if it has the correct speed, it can hold it a little bit longer without correction. It needs a few seconds to get the right speed, so the disc is not too heavy for the motor. My "real" Televisor has a club disc made of plastic, it needs the same time to get the right speed, and both discs (BTW the same with the MUTR monitor, too) need a manual correction of speed after the motor has warmed up.

[Steve Anderson]

I must admit that I've scratched my head over this one a few times. It seems that the vast majority of discs have material removed creating a spoked wheel/disc. This will reduce the weight, but I'm not sure that's a plus point.

Doing so does reduce the load on the bearings, but I would have thought that within limits the additional mass would provide a better flywheel effect. The spokes could also increase the aerodynamic drag, I note that more than a few cyclists now have solid wheels. This could be negated by running it in a vacuum!

The other big advantage? There's not so much work to do!!

Steve A.

[Viewmaster]

Thanks for your thoughts...
Not having so much work to do appeals to me. So for starters I will use a blank disc. Holes/spokes could always be added at a later date.
I would have though that spokes could create an additional unwanted whining noise too.
The spinning Nipkow is like the old sharp bacon slicers discs once seen in grocer shops.....(do you remember the hank of bacon held in a reciprocating table which indexed forward for each bacon slice, adjustable for thick/thin slices?)
Cannot understand why NBTV enthusiasts using aluminium discs don't have missing fingers!
Albert.

[DrZarkov]

How about a new NBTV-programme: "The Nipkow-disc massacre" about an inventor in the early thirties who cannot accept that everyone prefers electronic scanning devices and his invention became obsolete?

[Viewmaster]

So he goes around slicing every non believer's head off with a 4" pocket Nipkow which has a razor sharp stainless steel edge.
"The Nipkow slasher strikes again."
"Read all about it."
"Star, News 'n Standard."
"Nipkow slasher strikes." "Scotland Yard baffled."

Albert.......hiding under the bed!.

[Klaas Robers]

I mentioned this already before: Denis Asseman made me some years ago a 50 cm ø (20") aluminium disc without spokes. For his own replicae of the Baird Televisor he made spokes. The spoked discs are wobbling about 1 cm peak to peak, the unspoked disc runs without wobbling.
My monitor in wooden case has a Mart Schouten aluminium disc of 30 cm diameter. It has large holes in the centre part to reduce weight and it wobbles.
The reduction of material is mainly ment for reducing the rotating mass in order to improve the synchronisation capabilities using a phonic wheel. However the dynamic mass is more dependant on the mass at the outher side of the disc than on mass at the inner side. So the loss in dynamic mass is not large. With electronic synchronisation (4046) this is less an item. A thin aluminium disc is anyway so light that bearing problems are not really a point.
My advice: no spokes or holes.

[Steve Anderson]

My advice: no spokes or holes.

Klaas, I agree 100%. I can't see how spokes/holes provide any advantage. (Unless I have really missed something).

Steve A.