Starting at the beginning with Mirror Screws

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Re: Starting at the beginning with Mirror Screws

Postby McGee2021 » Tue Aug 08, 2017 12:39 am

albertMunich wrote:Incredible! You did it ! Damn it- my 3d printers are 800 kms away. Do you think it would be necessary to keep the "optical" sides of the slats in touch with the glass printing bed to keep them flat? Or will the flatness be ok for plating?

FYI: Found the original BRAMI VISIOLA patent- Harry this French Televisor from the 30s is a great find because it shows that a mirror screw does not have to be humungous in size. Simple motor, phonic wheel for sync and a led line lamp. A small handy 30 line demonstrator -thats what it would be without the need for a 50 cm diameter Nipkow. And the screw would be of a printable size.

In the Brami disc they kept the slats as a pack, polished the edges while the slats were kept in a jig and then they used the stepped edges for alignment with another special jig. Have a look at the drawings...perhaps the stepped edges could be made in such a way that the alignment is almost automatic.?
Once the thing is aligned the slats can be fused together. I think by the time I get home you'll have a 3d printed mirror screw!



Brami TV supplement.pdf


Interesting how they put the slats into a cylinder with spirals cut out of it to alight the slats, i think i might draw up a model in Autodesk Inventor, give me 2 weeks and ill have access to a laser and plasma cutter, and one of the largest CNC mills on the market. Then ill start making some metal slats! But first, the parts for my televisor shall be made.
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Re: Starting at the beginning with Mirror Screws

Postby Andrew Davie » Tue Aug 08, 2017 12:48 am

albertMunich wrote:Do you think it would be necessary to keep the "optical" sides of the slats in touch with the glass printing bed to keep them flat? Or will the flatness be ok for plating?


Interesting question - my guess is that it would not be good enough. Each individual filament-pass might be flat, but the area between 'rows' of filament would probably have imperfections. I think the most likely way to success with this is to print in any orientation and then assemble all slats into a flat block and then polish it flat. Or with ABS maybe acetone-melt it flat. Or perhaps with PLA just melt it flat on your heated bed. I don't think they will come usable-flat straight off the printer.
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Re: Starting at the beginning with Mirror Screws

Postby Andrew Davie » Tue Aug 08, 2017 12:51 am

albertMunich wrote:Auto aligning slats? No pin...what do you think?


I think it's a clever idea, but that filament 3D printers would not be accurate enough to make it work. Those edges need to be really precise, and a printer isn't going to be able to do that too well. With guide-holes, you are not (really) relying on the edge of the filament to be accurate, you are relying on the averaged position around the hole centerpoint to be accurate. That is, imperfections in the printing of the hole might average-out and the hole center might actually be more accurate than the printer can position individual filament. That's my theory!
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Re: Starting at the beginning with Mirror Screws

Postby Andrew Davie » Tue Aug 08, 2017 12:56 am

McGee2021 wrote:Unfortunately, i tried to print at to high detail, and did not have enough solid top AND bottom layers. They'll serve their purpose, but they come with imperfections. I took out the handle on my bathtub, which was conveniently a circular acrylic tube. Now for the lighting part...


Exciting to see it come together, though! How was the pin/hole issue... tight?

Your "infill" looks very sparse, (15%?) and although that won't affect the dimensions of the print, it does make it difficult for your top layer to print smoothly, and that's probably why we can see the pattern in the tops. I find that 2 bottom layers are sufficient, and usually I print 2 top layers but now I'm experimenting with 3 top layers to give a really nice finished look. Typically I use infill of about 20-25%, minimum. I have also started experimenting with "quick hexagonal" infill, which seems to do a nicer job.
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Re: Starting at the beginning with Mirror Screws

Postby McGee2021 » Tue Aug 08, 2017 1:11 am

Andrew Davie wrote:Exciting to see it come together, though! How was the pin/hole issue... tight?

Your "infill" looks very sparse, (15%?) and although that won't affect the dimensions of the print, it does make it difficult for your top layer to print smoothly, and that's probably why we can see the pattern in the tops. I find that 2 bottom layers are sufficient, and usually I print 2 top layers but now I'm experimenting with 3 top layers to give a really nice finished look. Typically I use infill of about 20-25%, minimum. I have also started experimenting with "quick hexagonal" infill, which seems to do a nicer job.


The pin-hole issue i solved by reaming the holes with a small screwdriver, and my infill is at 10 percent. the pattern is due to the fact of not enough solid layers, more solid layers, less of a pattern. I generally use 20-30 percent for parts that people order from me, but for myself, i use 10 percent. It saves time and filament. when im printing with 20 percent, ill have to order 2-3 rolls of filament per week, but with 10 percent, i only have to order 1, with the large amount of printing that i do. My printer hasn't stopped for more than an hour in the past 2 years.
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Re: Starting at the beginning with Mirror Screws

Postby Andrew Davie » Tue Aug 08, 2017 1:14 am

McGee2021 wrote:The pin-hole issue i solved by reaming the holes with a small screwdriver, and my infill is at 10 percent. the pattern is due to the fact of not enough solid layers, more solid layers, less of a pattern. I generally use 20-30 percent for parts that people order from me, but for myself, i use 10 percent. It saves time and filament. when im printing with 20 percent, ill have to order 2-3 rolls of filament per week, but with 10 percent, i only have to order 1, with the large amount of printing that i do. My printer hasn't stopped for more than an hour in the past 2 years.


I didn't realise you were so experienced with 3D printing - it seems I was teaching my grandma to suck eggs!
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Re: Starting at the beginning with Mirror Screws

Postby Andrew Davie » Tue Aug 08, 2017 1:30 am

Panrock wrote:A very elegant idea. This angles in this method would clearly be determined by the shape of the slats. For any but the lowest line counts they would end up very thin. See my diagram further up to get a feel for the angles. The reduced area of overlap though would lead to greater flimsiness and 'bendiness' in the complete stack. I noticed this effect even in mine, with lots of overlap.


If you printed in ABS and "painted" each slat with acetone as you put the whole thing together, it would be a solid chunk with no flex. That is, the slats would weld together via the acetone. As to the "reduced area of overlap" it would be easy enough to design the slats to optimise overlap - they don't have to be rectangular, do they?
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Re: Starting at the beginning with Mirror Screws

Postby McGee2021 » Tue Aug 08, 2017 1:40 am

Andrew Davie wrote:
McGee2021 wrote:The pin-hole issue i solved by reaming the holes with a small screwdriver, and my infill is at 10 percent. the pattern is due to the fact of not enough solid layers, more solid layers, less of a pattern. I generally use 20-30 percent for parts that people order from me, but for myself, i use 10 percent. It saves time and filament. when im printing with 20 percent, ill have to order 2-3 rolls of filament per week, but with 10 percent, i only have to order 1, with the large amount of printing that i do. My printer hasn't stopped for more than an hour in the past 2 years.


I didn't realise you were so experienced with 3D printing - it seems I was teaching my grandma to suck eggs!


Ive been printing since i was eleven, so, about 3 years Ive been printing? I feel as if i understand these things TOO much :lol:
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Re: Starting at the beginning with Mirror Screws

Postby McGee2021 » Tue Aug 08, 2017 2:18 am

Currently printing more slats, they are about 25% done.
0807171113-1.jpg


The tape at the edges is to keep the parts from curling up.
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Re: Starting at the beginning with Mirror Screws

Postby Panrock » Tue Aug 08, 2017 2:22 am

Andrew Davie wrote:If you printed in ABS and "painted" each slat with acetone as you put the whole thing together, it would be a solid chunk with no flex. That is, the slats would weld together via the acetone.

You are really 'nailing your colours to the mast' if you do not allow for later fine adjustment, though maybe you can get away with this at 32-lines. Even assuming perfect dimensional accuracy, differences in handling as you press the parts together to stick them could cause unpredictable positioning errors that might spoil the picture at higher line counts. I am not making trouble here... it really is that critical.

Not wishing to be a party-pooper, I am not clear of the advantage of 3D printing over CAD + laser cutting for making individual slats unless we already have proof it will be a more accurate process.

Andrew Davie wrote: As to the "reduced area of overlap" it would be easy enough to design the slats to optimise overlap - they don't have to be rectangular, do they?

No , but if you make them non-symmetrical, make sure you maintain the balance. When you want the whole screw to be balanced after building up over 360 degrees, this is automatic when each component part is balanced.

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Re: Starting at the beginning with Mirror Screws

Postby Andrew Davie » Tue Aug 08, 2017 2:35 am

Panrock wrote:Not wishing to be a party-pooper, I am not clear of the advantage of 3D printing over CAD + laser cutting for making individual slats unless we already have proof it will be a more accurate process.


I expect it to be a far less accurate process, but it is accessible and it's fun to try and see what happens.
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Re: Starting at the beginning with Mirror Screws

Postby Panrock » Tue Aug 08, 2017 2:46 am

Yes, and hopefully we'll come by useful data as a result regarding just how good or poor it is. You're doing valuable work. (wish there was an emoticon for applause) :D

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Re: Starting at the beginning with Mirror Screws

Postby albertMunich » Tue Aug 08, 2017 4:33 am

My God you're all going at full speed! I am really happy about that.
In case anyone is interested, on a French forum I have found more pictures of the BRAMI Visiola - someone actually found one! Even in the original box. Brand new, no rust, no nothing, this is unrestored.
The French flea markets are amazing. I have found an original French Ruhmkorff spark induction coil from the Ateliers Ruhmkorff in Paris years ago in Bordeaux. And got it for a pittance because the seller did not have the faintest idea what he had. But many dealers seem to know a lot more about "exotic" gadgets from the past now. I might try to get in touch with the guy who posted it in 2014. To see what has become of it.

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Apparently it had a big knob on the back so it could be flipped from vertical to horizontal viewing position. I'm really beginning to like that thing.
DSC_2207_redimensionner.JPG
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He even found the line lamps. Green with envy!
Panrock, of course you're right about the accuracy in 3d printing .. but even if nothing comes of it I think its a good idea to have tried it. If only for the reduced weight and inertia!
And if you go to a laser cutting or cnc shop it might be nice to show them an assembled model. But perhaps we will be surprised how well it works.
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Re: Starting at the beginning with Mirror Screws

Postby albertMunich » Tue Aug 08, 2017 5:09 am

Hmm. The Brami pix were all on the Early television Forum as well as on the retro-forum.com where I found them. so perhaps old hat to you, but at least they're in the right thread here now.
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Re: Starting at the beginning with Mirror Screws

Postby Harry Dalek » Tue Aug 08, 2017 6:28 pm

albertMunich wrote:Hmm. The Brami pix were all on the Early television Forum as well as on the retro-forum.com where I found them. so perhaps old hat to you, but at least they're in the right thread here now.


Great to see more photos to this Albert i don't know if you read French but i think the the manual for this mirror screw i posted up a bit back you saw the slats look thiner in the manuals photos to the one you posted up may be because they have been painted black in the other areas i will post it again for others not having to search .
https://www.taswegian.com/NBTV/forum/vi ... rew#p11101

I wonder if either chrome painting the slats edges idea i like best Andrew or using mirror tape here might be an idea for your print outs ?
Thin acrylic mirrors can be cut another idea ?
Even using the slats to hold a polished wire might work copper wire mirror screw :wink:
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