Diagnose my Bolex Issue

[Oscar Soucy]

Hello everyone!

I did a camera test this weekend with my new Bolex H16 non-reflex. Basically everything seemed to work, but after filming for a few seconds, the bottom loop slowly shortens which causes the film to stop moving. The top loop stays the same size. I’m thinking either the take up spool side is moving quicker than the claw, or the claw is not moving quick enough to match the speed of the gears. Does anyone have any ideas?

Best,

Oscar

 

[Jon O'Brien]

I've not encountered that one myself. I'm not sure of your level of experience but have you disengaged the loop formers? I don't know if that would affect your camera issue (probably not) but I just throw it in here in case it does.

[Dom Jaeger]

If the loop itself is getting shorter (not just shifting position) then there is a discrepancy between the feed sprocket and the take-up sprocket. They are linked by gears, so the shafts should be turning at the same speed, which keeps the loop a constant size, but it's possible either the top sprocket is loose on its shaft (two screws hold it) or the film is somehow not engaging with the top sprocket correctly, perhaps too large a gap between guide and sprocket, allowing the sprocket teeth to slip over the film perfs.  

Ideally a newly bought Bolex should go for a service, it may save you a lot of wasted film, time and money. It's like buying a vintage car that's been kept in a garage for decades and expecting it to be roadworthy. 

Also just a thought - older Bolexes can have double perf sprockets, with teeth on the top and bottom, which are not compatible with modern single perf film stock. But normally single perf film just wouldn't run through the camera.