Idea: Conveyor belt mechanical TV

[aussie_bloke]

G'day all.

When I was building my plywood Nipkow disc televisor, I initially wanted to make it 60 lines but in doing that I realize I would be roughly halving the height of the picture in comparison to making it 30-32 lines unless I made a disc with a circumference that's double the size. Then I have been thinking about the aperture drum televisors which the holes were arranged diagonally across a strip that is wrapped around a disc and same issue applies when increasing resolution from 30/32 lines to 60 lines and higher, the circumference has to be doubled in size.

So thinking about the aperture drum televisor gave me an idea of a mechanical televisor that can be made high in resolution without having to make a whoppin huge Nipkow disc or aperture drum. So what came to mind is a conveyor belt mechanical televisor which you cut a long strip of flexible material to your desired length, punch/drill the holes in it to the resolution and picture width/height you want and mount it on a conveyer motor/pulley system arranged in the most compact way as possible with light source mounted behind the belt like that in an aperture drum televisor with screen arrangement in front (mask, magnifier lense etc) and there you have it, a bigger sized mechanical televisor with a very straight square/rectangular picture.

Has anyone else thought of constructing a conveyor belt televisor back in the mechanical TV days and in the more recent times? And has any actually been constructed???

Anyhow I have done a sketch of my conveyor belt televisor idea to visually represent what I am talking about which is in the picture below.

So what do you's think of this conveyor belt televisor idea? And what kind of problems would I run into constructing such a televisor? Am very interested in hearing some expert opinions.

I know one thing that has got me pondering is whether it can be driven by one motor or whether it would need a motor for each pulley for stability?

[Harry Dalek]

Hi troy

Yes it has been done not sure for 60 line ,most likly the easiest way would be a loop of undeveloped film perhaps 35 mm still film..and use a camera or 2's insides for the movements .

[Klaas Robers]

I know that I have seen an old drawing of it. Indeed using 35mm film. However there are a few problems:

1. it is rather noisy. The rollers and the film over it makes quite some noise, much more than a drum or a disc.

2. it wears out. The edges of the film wear out on the flanges of the rollers. After one minute of operation you need a new film loop.

3. film has a too low contrast. The transparency of the black of the film is too high to block the light of the light box, which is 1000 x as high as the brightness of a white area on the picture. So a (far) too low contrast is the result.

[aussie_bloke]

Thanks for your input guys.

Yeah, film in one sense seems to be the appropriate material for a conveyer belt but then there's those issues Klaas mentioned.

As for the extra noise, I think there may be ways to reduce it such as a lubricated pulley system with an acoustic hood to further reduce the noise.

Anyhow for the belt my first thought of material to use was thick insulation paper used for transformers like this http://sell.lulusoso.com/upload/2012031 ... _paper.jpg which I believe will be more robust than film. Another thought was a thin tough opaque black plastic strip that is wear and stretch resistant.

Another issue that sprang to my mind with the conveyor system is the possibility of the belt veering left or right on one or more of the pulleys and coming off due to slight imperfections to the belt being cut or positioning of the pulleys.

[Harry Dalek]

Well a belt monitor would be different you could use paper the paper i used on my drums were great for light might be an idea as i did test what your going to try infront of a light before you use it.

The pulley side of it easiest i can think of but depends on what you have troy would be 2 drums but you just need enough space for the light between the belts... 3 would give you lots of space as it said depends on what you can find or make .

I think its easier but to use 2 drums or 2 disks slits if you are going to make some thing more complex and it would give you also a larger size display for the work .

But having said that a belt monitor is what it is and never seen anyone try to make one.

[gary]

Another issue that sprang to my mind with the conveyor system is the possibility of the belt veering left or right on one or more of the pulleys and coming off due to slight imperfections to the belt being cut or positioning of the pulleys.

Well you could do the band saw trick where the wheels have a crown on their edges - this tends to keep the band centered.

http://woodgears.ca/bandsaw/crowned_pulleys.html

This may give some distortion to the belt surface but it should be negligible.

[AncientBrit]

Hi aussie_bloke,

If you work out the linear speed of the belt you'll find it's travelling at a considerable speed if the picture height is at all reasonable.

Probably why people have chosen to form the belt into a drum to produce a drum monitor which suffers none of the geometric distortion of a disc monitor.

If you go down that route remember its easier to punch a linear strip with the holes and then assemble this on the drum with a sideways offset start to finish to produce the spiral.

Regards,

Graham

[Viewmaster]

You'll have to think how to get sync. Using 35mm film one could use the sprocket holes to sync. With other material with no sprocket holes, how?
In addition to the scan holes another set of holes for sync maybe.
For 60 lines that's 120 accurate holes required to be drilled/pierced

[gary]

In addition to the scan holes another set of holes for sync maybe.
For 60 lines that's 120 accurate holes required to be drilled/pierced

Made somewhat easier (compared to a disk) by the fact that all of the apertures lie along a straight line - so only one dimension to get right.

Actually it is possible to get sync via the picture apertures with a bit of trickery - so, theoretically, 60 apertures spaced evenly along a straight line is all (all??? ) that is required.

[Viewmaster]

As has been mentioned, the speed of the film/band....

The equivalent linear speed of a 12 inch dia Nipkow's scan lines is about 40 ft per second.

This will also be the speed of an endless belt to give the same sized picture.
As most of us know, this picture is very small, so just to double its size would increase the speed to 80 ft per sec.

For 60 lines this would near double it again to 160 ft per second. The film/belt would certainly tend to flap/oscillate/tear/break....160 ft/sec is
about 140 MPH

[gary]

Well done Albert - there you have the major flaw I think.

[DrZarkov]

If you really want to try this: How about taking a bicycle-chain and gears, and glue the film (or belt made from other material) on that chain? The NBTV chainsaw massacre...

[Viewmaster]

The other thing to bear in mind is the length of the belt/film required.....

For 60 lines and a picture twice the size of the 12 inch Niplow, as I mentioned, it would be 12 feet long

So unless the belt run was a gaint 6ft long or 3ft x 3ft square, then it would have to run back and forth a few times to reduce overall size.

This imposes yet more noise and wear and tear at 160 ft/sec.
Bear in mind too that 35mm cine film only runs at 1.5 ft /second, not 160 !
.......and a bicycle chain normally at about 10.

[Harry Dalek]

I found one of my scanning belt files...
looks easy but i bet there will be some hair pulling out building before you got it right...
perhaps you could get larger size on a drum system like this using multiple nipkow scans with a interrupter to block out say 16 out of 32 nipkow scan lines or what ever every 8 depending how large you want the picture and or number of lines ?

It would drop the belt size length wise .

Could also go like film and tape just manually swap over nipkow film loops every every often !

[aussie_bloke]

Thanks all for your input on the conveyer belt TV, I think the logical thing for me to do is start small and work my way up like with the Nipkow disc set. When I get around to constructing the belt TV, I will start at standard NBTV 32 line and at a picture size equivalent to my 40cm plywood disc televisor which is about 30x38mm and then progress from there. Thanks Harry for the belt TV article with picture, I figured this would of been done before in the past and that article confirms it!

Anyhow will let you's know when I get started on constructing this belt TV.