One Weakness of Early Eyemo and Fresh Replacement Parts

[Simon Wyss]

To the repair people:

The 1925 Eyemo 71 design has a clutch spring between main spring hub shaft and first gear, to be preciser a helicoidal spring made from round wire with an axially protruding leg that sits in a bore of that gear. The leg can break off. In such a case nothing holds the main drive spring so that it unleashes instantly. I am having a 71-A here with this damage. What happens next is that one of the stop mechanism gears, it sits on the main drive hub shaft, will pound onto the other with the full energy of the drive spring. So the stop mesh is no longer there. Also, the main spring may unhook from the hub shaft.

It is difficult to buy replacement parts from the remainders of Bell & Howell stocks. Nobody at MPE knows the camera. Parts can be sold only by the civilian numbers. I have the military parts list, not useful. The civilian parts list is not given out. So the replacement of the stop gears can become cumbersome although you describe the parts exactly.

Since I didn’t want to fool around with the MPE people I decided to have fresh clutch springs made. They arrived Friday, the Eyemo is back to life now. The stop mechanism is dysfunctional but else the camera can be used. I have a couple dozens of springs. Interested parties may buy from me, CHF 10 each, net. Mind you that younger models, I don’t know from which serial number on though, have two shorter mirror-inverted legged coil springs. Bell & Howell had to improve the construction.

May many Eyemo users use their Eyemos. I love these noisy automatic cine cameras and I love to retrieve the savoir-faire from the twenties.

[Simon Wyss]

One of the new springs.

[Simon Wyss]

Have found the register of this camera too long. Bell & Howell’s specification is 1.5 inches plus or minus 0.0005. That is 38,1 mm but my measurements revealed 38,4 mm. The camera was sold that way!

So we machined 0,3 mm down to have 38,09 mm now, aperture plate screwed on. The head of the underlying release anchor trip nut screw I had to grind shorter as well.

Remaining problem is only to find lenses that have an [A] or [B] mount. They weren’t marked as such, only from model 71-C on the mount barrels were engraved with a C. The difference lies solely in the rotational orientation of the cameras’ guide prong and thus the position of the index mark. Additionally, nothing younger than 1939 will fit a 71-A, -B or -C.

[Scott Barton]

On 3/25/2023 at 9:13 AM, Simon Wyss said:

Have found the register of this camera too long. Bell & Howell’s specification is 1.5 inches plus or minus 0.0005. That is 38,1 mm but my measurements revealed 38,4 mm. The camera was sold that way!

So we machined 0,3 mm down to have 38,09 mm now, aperture plate screwed on. The head of the underlying release anchor trip nut screw I had to grind shorter as well.

Remaining problem is only to find lenses that have an [A] or [B] mount. They weren’t marked as such, only from model 71-C on the mount barrels were engraved with a C. The difference lies solely in the rotational orientation of the cameras’ guide prong and thus the position of the index mark. Additionally, nothing younger than 1939 will fit a 71-A, -B or -C.

It sounds like B&H needed six-sigma manufacturing practices back in the day, haha! Wow, some QA/QC Dept. Sheesh!

Kudos to you for keeping the roaring 20s alive! Very cool stuff...

Moviemaking was truly "magic" back then, right?

I mean, the real early work was remarkable and then Schwarzschild empirically witnessed and then attempted to mathematically explain silver halide blackening reciprocity well before they knew how it worked with the photons converting to photoelectrons in shallow interstitial pockets between grains of elemental silver that would nucleate on a defect in the silver halide lattice after photo-catalyzation and grow in size as development centers due to irradiance intensity and time and finally produce a grain cluster large enough and stable enough to imprint the latent image on the crystals of silver that were spontaneously being created from the instantaneous degradation of the photocatalytic metal-halide compound once the photons passed through the objective and the f-stop and was focused on the gelatin-based emulsion-impregnated silver salt. (Or something like that...Not really sure, though, hahaha! But it sounds like magic to me too! It's the ''real magic' of movies, IMO - because it's a natural process (presumably noted while mining the mineral bromargyrite at some point in history) and one that we eventually exploited on a large enough scale to significant beneficial gains for humanity...).

And especially with silver bromide being uncharacteristically, for a silver compound, densely packed into a face-centered-cubic crystal structure that could be manipulated using dopants to impart engineered crystal-lattice defects such as edge dislocations and probably inclusions since formulation temperature and kinetics were probably a big concern to the film chemists of the time...

So any deviations at all from a tried and true "recipe" could have had significant effects. How fun that would have been!!!

I bet they tried a lot of things besides sulfur and gold, for sure...

But they didn't have nano-silver particles back then, haha!

But yeah, without a real understanding of what was actually happening, I bet it did seem a lot like magic to them - and it still does to me in a way - and your efforts to preserve the way that the magic was captured are appreciated by many in our community I am certain.

Thanks for the detailed tutorial on your cameras and I hope you find the lenses that you seek...