Elmo GS-1200 black lower tensioner

[Douglas Meltzer]

Edwin,

That design is brilliant. It looks much sturdier than what I currently have. As for the spring, the service manual only has information about the spring pressure adjustment (30-40g).....anyone have any ideas?

[Steve Lee]

Edwin, that is absolutely brilliant.
Steve

[Lee Mannering]

I have nothing to offer but encouragement for you with this project and much applause for your inventiveness

[Paul Adsett]

The CAD design looks excellent Edwin. I think the success of this assembly in the GS1200 application will depend on which materials you plan to use for the roller and pin. One suggestion is a stainless steel shoulder pin and a DELRIN AF (anti-friction) roller. It would also be a good idea to have a thin metal washer on either side of the roller, with the outside diameter of the washer being less than the outside diameter of the roller.
I would also suggest that before you go into production with this part that you make it available for field testing by somebody on the forum.
Good luck with this project, a lot of GS1200 owners can't wait to dump the OEM design.

[Graham Ritchie]

Doug

I just used the original spring adjusting the tension I wanted by rotating the little tab that the spring hooks onto at the top, getting the tension right was more of an experiment that appeared to have worked out just fine. It appears to have just the right tension on the film after starting, with it settling down quickly to be a constant. The roller spins away quite freely on the film running under it. I check it every so often when running a film, and it seems good. The roller itself came from a old ST1200 that I use for parts.

What Paul suggests above would be even better.

[Douglas Meltzer]

All good suggestions.......what I'm curious about is the answer to Edwin's question of what would be the specs for the necessary extension spring?

[Steven J. Kirk]

I offer the greatest encouragement and I would buy several of these.

[Burton Sundquist]

...Here's the one in my GS-1200. I bought it from Leon Norris back in 2018 and at that time he said it was his last one. I believe he modified the OEM tensioner and added a screw - mounted roller. The spring seen behind the roller keeps it at the end of the screw shaft, directly in line with the film path.
His tensioner didn't include the tensioner spring but the existing spring works just fine.

[Edwin van Eck]

Thanks for the feedback. I will produce a small first series of this part. First we test it ourselves in our repair department. When it is working according to my expectations, I will ask someone from the forum as well for some tests!

[Burton Sundquist]

The groves carved in Steven's tensioner should be a red flag to all GS-1200 owners and another
worry. Let's hope the Van eck replacement becomes available soon! My stock tensioner has just started to wear at film edge. No image contact yet but who wants to risk it. Let's face it a horrible design that can be improved. And has been before.

[Renzo Dal Bo]

I tried another quick way to solve the problem of the lower scratching tensioner on my GS, with good results.
I simply wrapped the tensioner with a teflon tape, a low friction material that easily adapts itself without the need of glue it.
Another advantage is its white color. When you see the black plastic appears again, it's time to substitute it.

[Edwin van Eck]

The 3D printed Elmo GS 1200 - black lower tensioner is now build in a projector.

It functions ok. But I am not satisfied with the strength so far. I will make a more sturdy version (sticker material) and then I think it is ready for some serious testing.

[Douglas Meltzer]

Edwin,

Thank you for taking this project on!

[Paul Adsett]

While wishing Edwin every success with this project, I am alarmed at the surface finish of the roller in the photo, which looks like sandpaper ! I think that will have to be addressed.

[Stuart Budd]

When I first followed the path of the film through the GS1200 and saw that (factory original) tensioner moving up and down as the film scrapped over it, I did think, of all the places this machine has wheels to not have one there was a massive oversight. It just looked horribly wrong. There seems to be several versions of the GS1200, Marks or production improvements versions. I wounder if this would have been addressed in later designs. Nice to see it developing still.