Starting at the beginning with Mirror Screws

[Panrock]

Cогласен. Every little speck of dust or smear can spoil the picture. That's a very good mirror finish you have achieved and I would be happy with it myself. Today, I am visiting the polishing company and taking my block.

Steve O

[Panrock]

The mirror block is back. Two local firms were involved - one for the grinding and one for the polishing. It cost a few bob but the improvement will be worth it. Note how important absolutely scrupulous cleanliness is... the reflection of my mouth is behind a finger mark here! The 'lineyness' is due to the slats having settled slightly during the polishing process. This won't affect the picture.

Meanwhile, on another front, Karen O has drawn my attention to this:
http://www.microsharp.co.uk/index.php/n ... nched.html

It's one-dimensional light diffusing material. Added to the front of my RGB lines-of-light, it could merge the individual LEDs in the vertical sense without any loss of sideways (ie. video) definition.

Steve O

[Harry Dalek]

Hi Steve looks good hate to think what it cost to polish it ....how do you stop touching it when you put it back together i am thinking gloves yes ? ,the new diffuser looks worth it if you can get it ,good for all nbtv work really but for you its spot on are you going to try and get it ?

[Panrock]

The gloves are a good idea Harry. Thanks.

This seemed a good time to black the backs and ends of the slats while they were still all locked together. After rubbing over with thinners to clean the surfaces, I lightly sprayed on some undercoat followed by matt black. Then the merest puff of clear lacquer for protection and to discourage dust marks.

I shall go out and get some 'Silvo' metal polish today. I am "greedy for gleam". Maybe I can make the mirror finish even better?

the new new diffuser looks worth it if you can get it ,good for all nbtv work really but for you its spot on are you going to try and get it ?

Yes, this will be a refinement at the end. I'll have to work out how to mount it. I may also combine it with strips of black tape to create masking slits of the right width to give the optimal video bandwidth. Karen can advise the figure here, using her fancy mathematical formula.

Steve O

[Panrock]

I've recently been delayed while preparing for a meeting in London about getting 405-line analogue television back on the air on its original band here in the UK. I attended the meeting as part of a team. I'm pleased to say it went well and it really does now look that 405-lines is going to return to the airwaves! Incidentally, this rather removes the need for my 'optical broadcasting' activities, which were intended as a fall-back should the radio licensing have proved impossible.

Anyway, back to the Mirror Screw. I have now started the laborious (or at least boring!) task of reassembling the mirror slats in 120-line configuration. Only, straight away I have hit a problem. All my original 4.5mm long indexing pegs have been lost and I'm going to have to make 240 new ones (from 4mm OD brass tube if I can get it). The 6mm long pegs I made for the 60-line construction are no good for this. I guess I could shorten them but in any case there are too few of them.

So it's going to be another few months before this 120-line screw is finished! Mirror Screws may be fun to use but are no fun to build. The more lines, the more labour. Last thing, you recall I was complaining about building the Line-of-Light. But that eventually got done. So will this.

Steve O

[Panrock]

Well, maybe not a few months... more likely a few weeks. I'm now up to slat No. 25. Another 95 to go! You can't see the actual reflective surfaces in the picture.

Each slat is numbered so I can ensure it is assembled next to the same neighbour it had when they were all ground and polished as a block.

The slats' other sides are being blackened by two applications of a permanent black marker pen. I'm hoping this will be more reliable than the previous method using matt black paint (and undercoat), which tended to flake off.

Each slat is located by two brass pegs on either side. Each peg passes through a run of three slats below it. In this way the whole assembly is rigidly interlocked... comforting to know when the whole thing is whizzing round 25 times a second!

Each peg has to be specially made and then carefully teased into its hole. It's a fairly tight fit, so this can't be rushed.

I'm building up this new screw while leaving the bottom thrust and radial ball races in position. The upper (radial) one is supposed to be a sealed type, but I want to take no chances with grit entering, so it's covered with a temporary plastic sleeve and kitchen paper.

I'm very glad I had these slats professionally ground and polished. I think the picture will be much clearer as a result. However, 0.3mm of metal was removed from each one. This is to the side (the short dimension), so the balancing should not be too greatly affected. In any case, once the full 360 degree corkscrew of them is finished, all the errors should cancel out.

A Mirror Screw has a strange beauty all its own. As it grows, it becomes more and more attractive to behold - a sort of reward for the fag of building it.

Steve O

[Harry Dalek]

Great work Steve ...that does look tedious ! but i am sure well worth the effort.....

Also interesting news on the 405 line ! is it just for any one to use the channel or you have pretty much got a little tv station for your group .Never heard of a vintage tv system coming back ...
I am not sure if it was ever used in Australia so i did some research i know in the late 40s a tv system was demonstrated i think at the Sydney easter show sounds likely it was something before 625 line .
Looking up the very first late 40s tests the Sydney ones were 405 line so it did make it here and the Melbourne ones were 625 line ////
Thanks to Troy mentioned this link as well
https://www.youtube.com/watch?v=nk8-vuapgjk

[Panrock]

That's a fascinating and little known piece of history Harry! The picture on Troy's YouTube reference was very good. I wonder if anything similar took place in New Zealand?

It's been a long process trying to bring 405-line television broadcasting back to the UK and it's not finished yet. You can keep abreast of the latest news here: http://405-line.tv/?page_id=127

Moderators... this post and the preceding one have really been off-topic for this thread. Perhaps move them to start a new thread in the 'electronic' section?

Steve O

[Panrock]

Over half way now... at No. 65!

Having run out of the original slat locating pegs, which were then shortened, I am now making new ones from 4mm brass tube. I first mark the cutting positions, slightly long, then cut them using a mini pipe cutter intended for brake pipe. Finally, I grind them to an accurate length against a steel grinding plate of the correct thickness, which has a hole to accept them.

Steve O

[Harry Dalek]

Over half way now... at No. 65!

Having run out of the original slat locating pegs, which were then shortened, I am now making new ones from 4mm brass tube. I first mark the cutting positions, slightly long, then cut them using a mini pipe cutter intended for brake pipe. Finally, I grind them to an accurate length against a steel grinding plate of the correct thickness, which has a hole to accept them.

Steve O

Good Work Steve looks great your over the half way ! does not look easy and it would be twice as heavy i should think

[Panrock]

... twice as heavy i should think

A reasonable thing to think, but no... the slats were mounted in side-to-side pairs before, for 60-line working. Now, they're being mounted as singles for 120. So the total number - and weight - is the same!

Steve O

[Panrock]

All 120 mirror slats now individually re-polished and mounted.

Phew....

Steve O

[Harry Dalek]

All 120 mirror slats now individually re-polished and mounted.

Phew....

Steve O

The Beast looks good Steve your thoughts can turn to testing now !

[gary]

A thing of beauty to be sure.

[Panrock]

Kind comments fellas. Thanks.

Actually it looks kind of dishevelled at the moment. There's a temporary protective cup over the bottom bearing, the top one is missing entirely, and I have yet to 'black' the rear surfaces and index pegs. For all I know there could be a horrible general error in the positioning of the slats, though the 120 of them seem to be describing the correct 360 degrees.

All joys in store. How much more hair will I lose?

Steve O