BOLEX - Camera looses loop

[Arthur Sanchez]

Hello all you Bolex gurus out there...

OK, I have a Bolex H16 REX 5 that threads nicely and seems to be running well. The camera maintains the loop while running with out a take-up reel... But as soon as the take-up reel used the loop begins to be lost.

 

But note not all take-up reels cause this... I switched out take-up reel and some reels work fine and some do not. and it seems to be consistent.

 

any ideas on what causes this to happen?

 

Arthur!

[Simon Wyss]

With no spool should that happen. The film jumps from the sprockets, so most probably the sprocket drum is not properly set along its axis. Did anybody screw on it? Also the film guidance (spring loaded forks) may be bent. Guidance and drums work together, or they don’t.

[Arthur Sanchez]

No Simon... some spools work fine and others don't... and with no take-up spool it work always.

the film never jumps from the sprockets ... the loop just very slowly starts getting smaller...

 

and if there was an alignment issue it wouldn't work with or without spools...

 

It's almost as If the take-up is pulling the film too much.

[Dom Jaeger]

The film must be jumping a sprocket tooth, otherwise the loop would stay constant. The take up spindle pulls on the film as the take up sprocket roller feeds it through, so any misalignment or maladjustment can cause the film to jump a tooth. You need to make sure the gate is parallel (use the gate alignment jig), the sprocket roller height is correct (use the height setting block), the guides are aligned and correctly spaced and there is nothing bent. Also the take up tension should not be too strong - make sure the belts are clean (I sometimes lubricate them with GN paste so the take up spindle slips more smoothly rather than jerking on the film). Different spools may be slightly altering the angle that the film is making as it leaves the take up sprocket roller, and either helping or hindering the alignment. If everything else is correctly set it shouldn't matter.

[Dom Jaeger]

The only other possibility I can think of, if the film is not jumping a sprocket tooth, is that the sprocket roller is slipping on its shaft, however this would throw the automatic threading timing out.. But check the screws holding the sprocket rollers are done up tight.

[Simon Wyss]

Arthur, you haven’t answered my question, did anybody screw there? As Dom mentions, the roller not holding to its shaft is the only other possibility.

[Arthur Sanchez]

DOM YOU'RE A GENIUS!!!!

 

it was the loose sprocket wheel...

 

it's weird how the auto-thread never failed... cause that would have point to something wrong in the sprocket wheel setting...

 

Thanks again Dom!.... Genius at large!

[Dom Jaeger]

Glad we could help!