Mixed or fixed NBTV cylinder machines

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Mixed or fixed NBTV cylinder machines

Postby Viewmaster » Tue Jul 10, 2007 6:31 pm

I daresay there are as many ideas as to how the design of a NBTV /cylinder machine might be as there are grooves in a wax cylinder!
(at the standard 160RPM for 2 mins that's 320 ideas! )

Some will favour a new machine with the Nipkow disc system and the new cylinder system all built into one cabinet. But unless one is certain about obtaining sync from the cylinder (which might well have been recorded from NBTV files from a PC or CD), then it would be a risky enterprise I reckon.

Others will favour a seperate cylinder system which can be attached to their existing NBTVs. Here the sync coupling has to be electrical, maybe along the lines I suggested re the rotating sync wheel.

So, if I could solve the cutter head problem the later is the way I would go, because a seperate machine allows for easier experimentation if things don't pan out successfully first time.....or 50th time!

I would also ensure that each NBTV frame occupies an exact number of grooves in the cylinder. (at the standard 160 RPM there are ~4.7 frames per cylinder groove)...hope my calc is right!

So I would ensure that it was a whole number, say 5, because that would enable a continual pattern to be seen along the whole cyl length and this might help in the sync problem eventually.
I say might! I do not know.

Anyway the repeated patterning along the cyl wall would look very pretty, don't you think!
Albert.
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Postby Klaas Robers » Wed Jul 11, 2007 5:02 am

However, if you keep the 160 rpm then you come to exactly 150 NBTV-lines on one revolution. This is 4 full frames and 22 lines of the next frame. So the sync pulses will be still in line and give a nice pattern on the cylinder.
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Postby Viewmaster » Wed Jul 11, 2007 12:07 pm

Klaas Robers wrote:However, if you keep the 160 rpm then you come to exactly 150 NBTV-lines on one revolution. This is 4 full frames and 22 lines of the next frame. So the sync pulses will be still in line and give a nice pattern on the cylinder.


Yes Klaas, that is true but I now tend to favour a slightly non standard 150 RPM cyl speed for 2 reasons........

!st. The gear reduction from 750 RPM (if that is required in a design) is a very simple 5/1 whereas the gear reduction for 160RPM is a complex and maybe a practically impossible 4.6875/1

This would mean a compound gear train which will add to friction and much more importantly to gear noise in the machine.

2nd. Having complete frames starting exactly at the same cylinder radial position might be a very useful insurance in overcoming sync problems.
Again, the operative word is 'might'!
Until a final design were achieved it is not possible to say if this would be useful or not.

You can see that I am burning the midnight oil on this if you look at the post timing of this letter! :lol:

Albert.
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Postby Klaas Robers » Thu Jul 12, 2007 2:44 am

What do you think of a planetary gearing with 16 teeth on the sun-wheel and 75 on the annulus? Or 32 : 150 if you like a smaller modulus better?

On the other hand I thought that a non coupled system was adopted, so no coupling between the cylinder and the reproduction disc. I wouldn't recommend that, as the speed of the hand cranked reproduction cylinder is not that constant. Then the high innertia Nipkow disc can't follow that in a servo controlled way. That is the reason that I am so happy with cristal stable audio out of the CD-player.

I never know what to think of the time indication on the forum pages, if this is the local time of the writer, or my local time, or the local time where the forum is hosted, or GMT. I fear that you can initialise this as you like, so I don't look at these indications. One of the problems of world wide systems.
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Postby Stephen » Thu Jul 12, 2007 3:19 am

Klaas Robers wrote:I never know what to think of the time indication on the forum pages, if this is the local time of the writer, or my local time, or the local time where the forum is hosted, or GMT. I fear that you can initialise this as you like, so I don't look at these indications. One of the problems of world wide systems.
In your Member Profile you can set the time zone for which the time indication for messages displays and this then converts all messages to your selected time zone. This does not affect the time stamp on any outgoing messages. If you have the time zone set to other than that of the sender, then you have to make the necessary conversion to determine when the sender posted a message in the sender's time zone.
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Postby Viewmaster » Thu Jul 12, 2007 3:30 am

Klaas Robers wrote:What do you think of a planetary gearing with 16 teeth on the sun-wheel and 75 on the annulus? Or 32 : 150 if you like a smaller modulus better?


That will give 160 RPM which I would not use.
Maybe you would be able to get this exotic type of gearing (at a fancy price?)but I would prefer to keep things simple if possible.

So my preference at present would be for 5/1 simple and cheap spur gear from 750 to 150 and then again 5/1 from 150/30 driving a
12mm x1.25mm pitch leadscrew to give an exact .010 " groove spacing as per standard 2 minute cylinders. 12mm dia lead screw would be quite sturdy and inflexible enough for this purpose.

This is simple and cheap gearing and will acheive what I have in mind.

Klaas Robers wrote:On the other hand I thought that a non coupled system was adopted, so no coupling between the cylinder and the reproduction disc. I wouldn't recommend that, as the speed of the hand cranked reproduction cylinder is not that constant. Then the high innertia Nipkow disc can't follow that in a servo controlled way.


I am favouring the seperation of the NBTV machine from the Cylinder for the reasons I have previously indicated, so the sync from the cyl will have to be electrical, and my cylinder will not be hand cranked.

Not being able to rely on pulses on the actual wax cylinder is a big problem. A strobewill only ensure correct speed but not pick up where lines and frames start on the cylinder.

At 150RPM there is 20 seconds available before starting the 2 minute playing time on the blanks I have bought. In this time sync must be obtained as the short 2 minutes cannot be wasted in making sync adjustments, so I am thinking of using this 20 seconds with a static image.

Each cylinder is tested out to establish correct sync in this 20 sec slot
using my rotary opto fork sync wheel and the cylinder is given a sync number which is entered on playback, this giving correct sync relative to the cylinder. This is another reason why I require to have an exact number of frames per one rev of the cylinder. 5 in this case.

But allthis is still in the melting pot! :)

And just to make life really hard two cylinders may be part of this machine, one for the sound and other the picture !
[/quote]

Klaas Robers wrote:I never know what to think of the time indication on the forum pages, if this is the local time of the writer, or my local time, or the local time where the forum is hosted, or GMT. I fear that you can initialise this as you like, so I don't look at these indications. One of the problems of world wide systems.


Well Klaas, I can assure you that it was in the middle of the night I wrote that letter. I couldn't get to sleep as each time I tried giant gear wheels kept waking me up again. :lol:
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Postby DrZarkov » Thu Jul 12, 2007 3:36 am

Instead of messing with stereo or double cylinders, why not a double groove on one cylinder? It was done with so called "magic records" or "surprise records" with two or three different recordings on one side of the recording, depending where you put down the needle. Disadvantage is of course half the playtime of the cylinder.
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Postby Viewmaster » Thu Jul 12, 2007 3:45 am

DrZarkov wrote:. Disadvantage is of course half the playtime of the cylinder.


This has been mentioned before, but........

With cylinders being so short on playback time that surely would not be a disadvantage, but a bit of a disaster. :lol:

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