NBTV wax cylinder synchronisation

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NBTV wax cylinder synchronisation

Postby Viewmaster » Mon Jul 09, 2007 4:01 pm

On the face of it putting the cylinder system on the same drive as the
Nipkow disc seems the way to go to get synchronisation on recording and playback.
But there is a big problem in doing this I think....
Even if the cylinder each time is keyed to the cylinder mandrel, because the recording/playback head is placed gently by hand onto the cylinder surface, as is normal for cylinder machines, there is no correlation then between the line/frame information on the cylinder and with the Nipkow disc postion.
I therefore think that a seperate drive and machine be used with what I would call a 'rotary adjusting sync wheel' as my rough sketch shows.

It would be about a 4 inch dia wheel driven at 750 RPM with the 31 sync holes around its outer circumference, (like the present Nipkow.) The new idea though is to have the opto fork on a rotating arm which can be swung around in order to send sync pulses correctly aligned with the picture information coming from the cylinder. A small adjusting knob at the end of the shaft would enable this.

Each time the reproducing head is placed upon the start of a cylinder a new sync adjustment will be required by moving the opto around once again (because each time the reproducer/recorder is place upon a cylinder it is always in a different relative radial position to the cylinder and to the start of line/frame picture information.)
.....this might be all part of the novelty in using a cylinder system. :)

Another advantage of seperating the drives would be that existing NBTVs could easily be adapted to use the cylinder system by just adding 2 external phono plugs. One for the picture information from the new cylinder machine and the other the sync pulses from the new rotary sync wheel on it which could be taken straight to the motor control 4046 IC cct., so bypassing any normal sync seperator.

Added later........
If standard sync pulses where to be modified to have a longer pulse length these could then be recorded directly onto wax, but this looses some picture info. :cry:
Albert.
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Rotary adjusting sync wheel
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Postby Klaas Robers » Mon Jul 09, 2007 5:26 pm

I read all kind of wrong things: Opto fork, 4046, IC's.....

Why not placing a differential gear in between the Nipkow disc and the 1:8 reduction gear? The position of the planetary wheels then could be rotated and the relative position of the disc in respect to the cylinder can be set for correct interaction.

An even better solution would be to use a planetary gearing to do the 1:8 reduction and the relative position setting in one. Then the disc should be at the the sun, the position of the planetary wheels is adjustable and the annulus is then connected to the cylinder. It is not impossible that you can find such a gearing in a discarded rechargeable hand held drill and/or screw driver.
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Postby Viewmaster » Mon Jul 09, 2007 6:30 pm

Yes that is another way to go, but I was trying not to introduce too much extra delicate engineering...gears and yet more gears, and a seperate machine has its attractions as I mentioned.

I haven't handled an Edison type phonograph, maybe someone could tell us how the lead screw/reproducer positions work when lowering it down onto the disc. etc.
Albert.
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Postby DrZarkov » Mon Jul 09, 2007 8:41 pm

IMHO synch should be a problem of the camera/monitor, not of the recording device! to let the cylinder spin a the correct speed a simple stroboscope should be fine. In 1930 television had been transmitted on shortwave, there was no extra channel for synch impulses, too. An electric recorded cylinder will be much better than any shortwave signal. Making a recording more durable is just a choice of material. As i suggested before, a cylinder made of Fimo, http://en.wikipedia.org/wiki/Fimo would be ideal. It is a kind of clay, which is formable like wax. After heating it at about 150 degrees it is hard like plastic and durable.
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Postby Stephen » Mon Jul 09, 2007 11:47 pm

Viewmaster wrote:I haven't handled an Edison type phonograph, maybe someone could tell us how the lead screw/reproducer positions work when lowering it down onto the disc. etc.
With any of the cylinder machines, and with the Edison Diamond disc machines as well, a threaded half-nut engages a lead-screw when you lower the sound head onto the cylinder or disc. In the case of recording, the groove cuts wherever the recording stylus lands on the surface. In the case of playback, the groove in the cylinder surface when mounted on the mandrel may not line up exactly with the leadscrew. For this reason the sound head has a stylus linkage that is laterally loose so that it may rock from side to side to engage a slightly off-centre groove. Someone seeing such a sound head for the first time might think that it is broken because of the lateral play!
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Postby Viewmaster » Tue Jul 10, 2007 2:56 am

Thanks for that description, Stephen. Very helpful.

I did think that some lateral movement must be built in for playback .
The half nut too enables quick return to start of play again without running it all backwards.

I have been eyeing our 2 inch and 4 inch diameter plastic round rain water down pipes on the house as material for cylinders if one wished to make very cheap ones....
..but wifey won't let me take a few foot down! :lol:
Probaly too soft anyway.
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Postby DrZarkov » Tue Jul 10, 2007 3:43 am

For lateral movement at playback you can use the groove itself to lead the reproducer (like with a grammophone). It was done with very cheap playback-only phonographs like the "Puck". If you use an electric reproducer it should even work better without wearing the grooves out.
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Postby Viewmaster » Wed Jul 11, 2007 5:22 am

For replay,if it's mono hill and dale one could probaly use a standard 78 pick up arm mounted at the rear of the cylinder with the stylus just on top of the cyl grooves. The arm then swinging across the cylinder as it would when playing a 78 record.

I wonder what the slight angular distortionwould look like on the NBTV picture so produced?
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Postby DrZarkov » Wed Jul 11, 2007 6:24 am

A standard grammophone arm is not very helpful, we need an electric signal, the grammophone is acoustic. But you can easily "abuse" a tone arm of an electric stereo record player, a stereo pickup would be able to read the hill and dale writing of the phonograph cylinder. And yes, it would have been possible with 1920th technology. Maybe they've wouldnt used a piezoelectronic pickup but a magnetic system, but that is just a question of parts you want to use. I have here some electric record players from the thirties (for use with steel needles), I think it would be possible to modify the tone arm of the old Dual record players for use woth a phonograph. (Just because it fits better to a phonograph than a stereo pickup.)
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