Wolverine-Hawkeye Telecine

[Stan Jelavic]

Thank you Kamel and Bruce. In https://www.treatstock.com/my/print-model3d/printers they offer several materials including resin. I ordered it in ABS from teh supplier in Tampa, FL. Will see if it turns out OK.

[David Brown]

Hello

I went thru this "printer" problem a few months ago printing the capstan parts. Printing the teeth for super 8 was not successful for me. So I sent the parts out. Shapeways is very fast and very precise. Did I mention VERY expensive! $25 for 1 super8 and 1 reg8. I printed all the other parts.

I think it's important that people have some instruction and practice using the inserts. I thought they would be pressed in with a vice. They are hot pressed using a soldering iron.

For the parts already in hand, I used epoxy putty to glue the insert into the retainer. The only force that will see is from the screwdriver. Most of these materials do not glue well. ABS can be glued with acetate (fingernail polish remover), but I have no experience there. The hub could be shimmed, I left mine loose. It still works.

[Kamel Ikhlef]

I redid the calculation of the toothed capstan pulley. the perforation pitch of the super 8 film is 4.234 mm.
If we calculate 12 teeth : 12x4.234 = 50.808 mm.
50.808 / 3.14159265359 = 16.172688 mm. The pulley must have a diameter of 16.172688mm.
R=8.086344 mm. The teeth are 0.8 mm base size.

[Stan Jelavic]

I measured the part and it is correct. In my case the problem seems to be the teeth themselves. The surface is rough and catches on the hole edges. Will see what the new parts are like.

[David Brown]

This might be useful. https://www.allthat3d.com/best-3d-service-online/

I was just reading that UPS is offering 3d printing in some of their UPS Stores. Not in my area.

Kamel I have found some of the 8mm specs and dimensions online differ, and even font one that was impossible. Verify if you can against your own films. It can be difficult to measure!

I don't have a problem with the "toothed pulleys" I had printed at Shapeways. Both can be wrapped with film and the teeth fit. The ones I tried to print either needed to be cleaned up or were different lengths. Those teeth are SMALL.

Sounds like I might be the only one with R8mm film. I'd leave a little clearance on the "back toothed pulley" for those of us swapping R8 & S8.

I will be reprinting that back pulley. This time I will test it for a friction fit on the motor. I just don't think it will slip. I had to drill it out larger just to fit the motor shaft.

[Bruce Davis]

Hi Kamel, I certainly did not mean to offend or criticise your work, I very much appreciate the hard work you have put into this project and making it freely available, your method of calculating is obviously correct.
From the wiki page it stated that Kodak Super8 has 72 frames per foot, that would be 4.2333mm Pitch.

I measured your STL file in Inventor and it came out at 16.1765216 mm Dia on the tooth side and 16.1765610 on the blank side, lets just say 16.1765mm (no FFF printer will print this accurately). Your STL files have an extraordinary number of segments, I can not reproduce this accuracy with inventor.

The image you posted where the film is wrapped around the S8 toothed pulley it looks as though the film is being held in place by the teeth of the pulley.

I have reduced the toothed pulley Dia by 2x the thickness of the S8 film (film is 5.5 thou or 0.0055 inches thick = 0.1397mm), 16.1765 - 0.2794 = 15.8971, I rounded it to 15.9mm Dia.

Have printed a sample and my S8 film fits perfectly around the circumference without binding on the teeth.

Thanks again everyone
Regards - Bruce

[Kamel Ikhlef]

Bruce,
On the contrary, the critics are very constructive and move forward.
This allowed me to recheck and improve my 3D design.
I redid the design of the capstan toothed pulley and curved pulleys (super 8).
the other files did not need modifications. I hope this will be convenient for everybody.
I will post the update of the files during the day.

https://drive.google.com/file/d/1xde...ew?usp=sharing

The super 8 pitch that I found is not the same as yours (4.23418 mm).
https://www.filmkorn.org/super8data/..._standards.htm

But if you are sure of 4.2333mm, So I can redesign a new pulley of 16.17mm diameter to be even more precise !
I will try your method for test on my printer (Dia 15.9)...
... And you are right that domestic 3D printers will not be able to reproduce this precision.
My printer can print at 0.02mm layer and 0.2mm nozzle max which is already very good !... But...
... But, I will be tempted to try the resin printing. I think about it...

[Bruce Davis]

Hi Kamel, as David mentioned, S8mm specs and dimensions online differ so I just used the formula of 72 frames per foot for Kodak film. The differences between your dimensions and the ones I used are fairly minor but because I found the tooth spacing too wide on my print of your first stl file I decided to use the lower pitch dimension.

It seems to me that this 8mm film specification is a bit of a dogs breakfast, made up of a combination of imperial and metric.

Thanks for your updated design, I have downloaded and printed it, see attached photo, it is very poor phone camera quality, my dslr is with my son. As you can see it is better, many more teeth than 4 as with the first version, but it is still very tight and the film is held in place by the teeth. This of course is on my printer with a 0.4mm nozzle at 0.15 layer height, material is PETG.

Dimensionally the print is correct with an overall diam of 16.1mm (measured with vernier caliper), square hole size 9.2mm and overall height 7.35mm.
Regards - Bruce

[David Brown]

Let me retract my claim that the toothed pulleys I had printed are good. There is something strange and that might be the tooth spacing.

Here is what happened, and I'm not finished yet. After the talk of tooth pitch, I remembered that I have tightened the screws in the gate. That relieves pressure. I also taped a spacer in the gate, equal to the folded paper used to stop the jitter. My gate is fairly quiet now. It used to make a snapping sound.

And I thought, why not move the capstan back to the 3rd pulley? Well, now it works! Before, the motor did not have enough torque to pull the film thru the gate, now it does.

So the film now wraps around 50% of the toothed pulley. For some reason the film does not stay engaged with the teeth for even 50% rotation. It could be the tooth spacing, but I'm not sure of that. There is no visible eccentric rotation to cause the film to move out of line.

I'll look at that again. Using a screwdriver to rotate the capstan in either direction, the teeth don't easily let go of the perforations, spacing?

Here is just a visual confirmation of the above calculations. These dimensions are real, not just labels. Measuring my actual pulley should be daunting!

[Stan Jelavic]

Had a hunch. Even if the film wraps around the capstan OK that still does not mean that it will not catch the tips of the teeth. See the picture attached.

The teeth height may be excessive. Not 100% sure about this but could run the math.

[Kamel Ikhlef]

Thank you to everyone for your participation. that motivates!
(Thanks for your feedback Bruce, David and Stan)

Yes, bruce you're right. the perforations seem to be too far apart.
Which is strange if the printed measurements are correct.

We will end up finding the right measure!

David, I don't understand how you found circ: 49,9422 (à quoi correspond le pitch 4.16185 (4.162) ?
Does that match the dia found by Bruce? by calculating with respect to the thickness of the film?

Indeed, it is not obvious at all ... I will design several Dia and test tonight....

Stan's latest idea is a good lead to think about...

[Bruce Davis]

Hi David, Stan, Kamel, David thanks for the illustration, I feel that the 4.23xmm pitch is more correct as per your illustration 12 inches divided by 72 frames.

Stan you have hit the nail on the head with your sketch, that is exactly the problem I found when trying to wrap the S8 film around the sprocket (capstan). As one moves further out in diameter the tooth spacing increases causing the film sprocket holes to catch on sprocket teeth, that is why I reduced the sprocket diameter to overcome this problem. One could also reduce the tooth height slightly, a matter of testing (I prefer using a smaller diameter).

Regards - Bruce

[Stan Jelavic]

Agree, it is better to keep the tooth height as is, less chance that it will slip off.

[David Brown]

KAMEL I like to have visual guides, I can get lost reading equations. I took Bruce's numbers and yours, sketched them in cad software. Pitch suggests the slope of a roof to me, but I see it is used with pulleys and belts. The cad dimensions will measure the length of an arc, which I take to be the same as pitch.

I started with the diameter you both choose and then measured the results. 12 teeth will be at 30 degrees.The circumference is reported in the margins. We started at different points.



The 12" piece of film I checked against the spacings I have to see how close to 72 frames that is. The precise number is less than 12" as the spacing is off .002mm.

The printed teeth on my pulley are clean, unlike the ones I printed that were damaged or distorted by the post cleanup I had to do. I had problems with wobble on the motor shaft and presumed that to be causing the film to disengage.

My first thought is to find a projector and compare the tooth length and spacing. BUT, I have no memories of film engaging more than a few teeth like the Hawkeye with the pulley in the 1st position. They do however have a retaining clip that keeps the teeth in the perforations.




This, should be reliable


and this also might be good.

https://www.filmkorn.org/super8data/database/articles_list/super8_fotmat_standards.htm

[Bruce Davis]

Hi Kamel, according to the SMPTE standard table1 the nominal pitch would be 4.227 (lets say 4.23 for the sake of argument).

There seem to be 2 standards:-
B, perforation pitch (long) = 4.234 mm
B', perforation pitch (short) = 4.227 mm

They also mention some film shrinkage after processing and with age (0.2% not sure if this applies to our S8 film).
This is all highly confusing, I would be inclined to use the shorter pitch dimension due to the problem as illustrated by Stan's Sketch.

4.234mm - 0.2% = 4.2255mm
4.227mm - 0.2% = 4.2185mm

By reducing the Diameter of the sprocket (capstan) to 15.9mm dia, the root pitch is 4.16261mm
The tooth tip dia @ 15.9mm sprocket dia will be approx. 18.1mm dia, the pitch is 4.73856mm
My printed Sprocket tooth tip dia actually measures 17.5mm, the pitch is therefore 4.581mm

What I am trying to point out is that one has to use a diameter that will work for both the root pitch and the tooth tip pitch, so that the tooth tip leading edge moves easily into the film perforation (or one could reduce the tooth length, not my favored approach).

Regards - Bruce