35mm film driven repstrap

getting there!

wow i just realised that bit of film actually says printer on it!!!

... excellent idea

How elastic/springy is the film?

This let me remember our talks about chains and such ... why not etch a stripe of 0,1mm thick steel similar to the film and build fitting pinchwheels with inserted nails?

Viktor

LOL! I absolutely LOVE this! :-)

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

Nice, how did you make / obtain the spools?

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[www.hydraraptor.blogspot.com]

They look like they've been scavenged off of an old film editing machine. Mind, I don't think they would be too hard to print.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

Of course the most attractive part of this is that it would be possible to develop the film to have an exact grating/pattern on it. Using that together with optical sensors and DC motors would allow for fine movement. We might need to glue the film on a non-stretching backing, but that seems a problem that should be easy to solve.

-Geert

film doesn't stretch much unless you apply alot of force, still pretty strong stuff. I'm a casual projectionist so we get heaps of scrap film, the gears are resin casts of an intermittent roller, a spare we had (from the head of a projector)

This in not only *very* clever, it's another widely available resource for driving mechanisms.

Q: Did you put the "PRINTER...." image onto the film?
Could you put regular stripes on it instead?
If so, such film could serve as both a drive belt and an encoder.

Good work!

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Larry Pfeffer,

My blog about building repstrap Cerberus:
[repstrap-cerberus.blogspot.com]

thanks! no the film is just scrap film that comes on either end of anything we receive; ads, trailers and spools from films. i probably have some plain film with no writing in the frames if that's what you mean? at work we put little magnetic tape on the film and the projector has a sensor which reads it and sends a que to the automation, i.e lights down, lens change, sound change etc. maybe that could be used as opto stops if that's what you mean by as an encoder?

... the idea is to expose an 'endless' sequence odf thin lines along the complete film ... maybe several lines with changing spacings, so with two or three optical sensors you can encode the actual position either incremental or absolute ...

Viktor

By "putting stripes on it" folk mean a set of black lines that will function like this stuff:
[www.usdigital.com]
[www.usdigital.com]
[www.usdigital.com]

It would be easy (but expensive) to expose black lines on film. Or 11"x17",13"x19" laser cutter transparency.
[www.printersupplyshop.com]

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A number of folk out there have laser cutters, and are willing to do cottage industry stuff. This suggests we can make our own timing belt out of mylar or another tough film, possibly semi-automating the job. Even making very long strips, and then running the strip across the bed of the laser cutter to cut the drive-holes.

Also, it wouldn't be too hard to build an apparatus to inkjet or marker-pen mark lines onto a film strip.

I don't know if either of these ideas are worth following up on. Simple conceptually, but it takes a bit of human time and machine time to do.

We can also print timing belt with the laser printer, and cut it (and drive holes) with the laser cutter.

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Setting aside the feasibility of buying large 36" rolls of mylar, looking at this:
BG-60 Mono laser printer film
Clear heat stabilized laser transparency film -13" X 19"
50 sheets - $42.50

Assuming a 13"x19" sheet makes 13 strips, each strip 19" (48.26 cm) long, then each strip costs USD 0.065 . (6.5 cents) for materials.

I assume people would buy "RepRap timing strips" for USD0.50, and folk would be willing to fabricate them for USD0.50.

Edited 1 time(s). Last edit at 02/05/2010 03:57PM by SebastienBailard.

For comparison, 19" long encoding strips from us digital are USD$40.
[www.usdigital.com]

... i can easily buy steel-stripes with 5m length, different breadths and thickness form 5microns upward ... then spool them through my laser and cut the feeding holes shouldn't be a problem

But maybe etching could be made easier or mor DIY-like by more people than with my special setup ...

Viktor

hmmm interesting idea. Although i am more keen to get printing than experiment with anything else at the moment.

here is a scan of one single negative i cut from sherlock holmes: you can see on the right inbetween the sprocket holes there is a DOLBY logo, which is actually a signal that is read i think with infra red. maybe that could be used?

... i can see some coding on the right border of the image-area - if this is along the complete film, then it would be very interesting as absolute positioning too

Viktor

That strip of film has quite a few soundtracks on it.

The analog is the two lines to the right. The little white pulses to the left of the analoge lines are sync codes which can be used for DTS played off of a CD. The Dolby Digital is between the sprockets. The outside Patterns are also Digital, I think this is DTS. Most modern film has about 5 soundtracks encoded onto it, I count 4 on this one.

Dolby is read with a camera and microscope. The outside tracks are read the same as DVD audio.

In theory one could recover the SMPTE timecode from a strip of film. Possibly even from the attached image.

Here in the communities near and outside the Silicon Valley, most theaters use digital projectors. Film is not going to be around much longer in the mainstream houses. Too expensive, as a print costs hundreds of dollars to strike.



-julie

Love it.. been busy so not got into the forum for a while..

Like the idea of using film having the belt run at 25Fps or whatever film is filmed at with a fixed light source in between the two strips of film and a lens mounted on the frame projecting the image on the wall providing visual entertainment whilst printing.

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now there's an idea!!

Hi all just so you know i haven't given up,

i've had a violent redesign, (and less time for cnc building)



i found a smaller part off the projector to use, and i'm trying to model it digitally, (and a pully system) so i can share it at thingiverse.. so far i've modeled it superfically in blender... i first have to learn how to model things precisely to the mm (only ever used blender for visual effects)

Love this idea film is so cheap.

Any idea where one could obtain some scrap-film?
I´d like to redesign a MiniMendel to use it and try this out.

What do you use to glue it?

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just go to your closest cinema and ask, they should have enough scrap in the bin for many mini mendels. If not they will eventually. If they don't feel comfortable giving you some, I can mail you some although remember i haven't finished it hasn't really been proven yet ...though it seems good so far,

Hey I want to redesign the film gear so it's the same size as the mendels gear and that way i won't have to tinker with the firmware...

Can anyone tell me what the diameter is of the mendels gears that drive the belts?

Then i will have it up on thingiverse i've worked out how to sculpt the parts i want perfectly it using this great tute:

[www.blendernation.com]

oh and no glue it has a 3 thread through the side for a tension screw, so it screws onto the spline (you have to file a flat onto your motor axis) you can see it on the top left photo on the blue one.

i have to redesign it though so the tension thread has more depth and room for more thread

mlagana2 Wrote:
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> oh and no glue it has a 3 thread through the side
> for a tension screw, so it screws onto the spline
> (you have to file a flat onto your motor axis) you
> can see it on the top left photo on the blue one.

Ah, not as a continous belt but screwed into the sled that it moves?
Cool idea!

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whoops that was meant to read m3 thread...

oh yeah the film attaches to the bed with 2 screws, i just used a hole puncher to put a hole in the film and nylon washer. im sure i could improve the design of the bed to do away with using screws/hole punchers... just want to speed things up!

can anyone confirm for me if the diameter of the mendel drive pulley is 11.96mm?

The diameter is not important, it is the number of teeth and the tooth pitch. The Mendel pulleys have 8 teeth with a pitch of 5mm, so they feed 40mm of belt per revolution. That would give a nominal diameter of 40/pi = 12.73mm, but timing belts are a few mm thick, so the bottom of the teeth would have a smaller diameter and the top a larger diameter.

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[www.hydraraptor.blogspot.com]

i think something like this

thanks nophead.... i'm gonna sleep on it still a bit confused.