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Gus Bendinelli

Transplanting Bolex EBM 170

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Transplanting Bolex EBM 170º Shutter to SBM


Hey there! I recently purchased a Bolex SBM and have been loving it so far. The one thing I'd love to change though is the shutter angle—the built in variable shutter is 135° at its most open setting, and thus the motion rendition is a bit choppy compared to the 180° standard I'm used to on an SR3/XTR.

After doing some research I noticed that the electronic Bolexes (EBM and EL), as well as possibly some early non-reflex models, have fixed 170° shutters. I'm wondering if its theoretically possible to transplant a 170° shutter into a Bolex that came with the variable 135° shutter. I don't expect to keep any variable shutter capability—obviously it would be a permanent change over to the fixed 170° version.

The main limitation I'm concerned about is that a 170° shutter doesnt provide enough cover for the SBM's pulldown mechanism to complete the frame advance, and that the EBM/EL have a faster pulldown which makes a 170° opening possible.

But if it was a visual aesthetic decision rather than mechanical decision (perhaps Bolex thought the tighter shutter would be better for most users since there would be less motion blur), perhaps it's possible. Unfortunately I don't have the means to test this myself, so I'm wondering if any Bolex experts/machinists can chime in!


(Sorry for the incomplete topic name, it got cut off by the forum software!)

Edited by Gus Bendinelli

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Not simple. The variable shutter mechanism is part of a different front plate. If you want to install a simple shutter, you need to build one of those onto the main works blank together with its bearing block. That again is dowelled. A standard front would round off the job. In other words, you can’t combine a simple shutter with a RX front.


I think it will be easier to find an older or a standard model that has everything in place. H-16s with serial numbers below 100,400 have a different claw mechanism and a shutter with 190 degrees opening angle. Invest in the thorough overhaul of a well-kept H-16 S and be well.

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There is no difference in the pulldown mechanism between the spring wound RX or SB cameras and the electric cameras.

I am not sure why the open shutter angle on cameras with variable shutter is narrower than on fixed shutters but it's not related to the pulldown cycle.

That being said, If you want a fixed 170º shutter in your SBM, it is possible if you have the right parts. This is something I could do. PM me for details.

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Paillard adopted the almost unchanged shutter variation gearing of the Ciné-Kodak Special (four gears). That mechanism has some play which forced the technicians to decrease the open angle by, say, ten degrees. In addition some void movement is necessary to have an overlap of the blades on closing, another 10 degrees perhaps. Different from the CKS the shutter shift control lever is not directly tangible. You have an internal lever with an opening into which protrudes another lever with a stud, still more play. What made them settle on 135 degrees I don’t know either.


Looking for a large shutter opening? Bell & Howell Filmo 70, serial numbers below 154,600 have 216 degrees, from #154,601 on 204 degrees. Mitchell 16 have 235 degrees.

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