Film-Tech Forum ARCHIVE: Brenkert Shutter Shaft setup

This is topic Brenkert Shutter Shaft setup in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Paul G. Thompson (Member # 655) on 02-17-2002, 09:27 PM:

That's something I never had much luck with when it came to complete teardown of Brenkert BX-40's, 80's, and 100's. I usually let the bracket in the casting.

Is there a way to easily set them up when they are re-installed in the casting? Once I tried it, I fiddled with it for almost 8 hours torqueing and untorqueing bracket bolts to get the shafte running free and easy again.

Posted by Mark Gulbrandsen (Member # 72) on 02-17-2002, 10:16 PM:

Paul,
Josh just asked me this same question. It sounds like something is warped or incorrectly machined. Could there be a glob of paint or something else under it causing it to warp when you tourque it down? I've had them out before, its been a really long time since I have had one out but I don't remember it being a bastard like you describe.
Sort of reminds me of the Century INtermittent drive gear assy. Some of the older machines were hand painted when assembled and paint got in between the top and bottom surface of the gear bearing bracket causing the thing to bind when you'd put it back together, in some cases even causing a new vert shaft to bend!

In the Brenkert having both of these mounting surfaces scrouplously clean is extremely important. They could be cleaned up with a stone very carefully without loosing any tolerances if in doubt. Also look for nicks in either the bracket or main casting if U used a screwdriver to pry the thing out. Clean these off with a stone as well. Both surfaces MUST be flat.
Mark @ Home

Posted by Paul G. Thompson (Member # 655) on 02-18-2002, 02:34 AM:

Mark, yes, I know. Josh and I were talking about it earlier today. He has an old scrap Brenkert I gave him to play with, and I suggested he give it a try to see if he was more successful than I was.

Actually, he was a little more successful in a shorter period of time, but he still had slight binding in some places as he rolled it through. (That's what I ran into when I tried it in my travels.)

The mating surfaces are clean of burrs, etc.

A couple of months ago, I demonstrated to Josh how critical those brackets are. I laid it over the edge of the table, and he held it in place. Then I put slight finger pressure on the other end of the casting, and the rear pinion had a very nasty bind and was almost impossible to rotate the pinion until the slight finger pressure was removed from the casting.

By jockeying the six screws that hold the shutter shaft casting in place, most of the time I could eliminate any nasty tight spots. After loosening the rear pinion collar Allen screws and tweeking, I was able to reduce the binding a little more. But that was the limit. There was still slight binding. After about 8 hours of screwing with this thing, I shouted an obsenity and said, "Close Enough!"

I wonder if Brenkert line-bored the shutter shaft casting after it was installed in the projector, and then assembled and installed the shafts and pinion gears into the shutter shaft bracket. By the way it looks, there is a good possibility it could have happened this way to maintain and keep the marvelous precision that has kept the Brenkerts running so well for over 50 years. Someone told me many years ago there was a lot of "hand fitting" of some of the the critical Brenkert parts. How true that is, I don't know. But it would not surprise me at all if it was.

I spoke with another tech, and asked about the varnish that builds up through the years in the shutter shaft parts. He suggested lacquer thinner will do an excellent job in removing the crud and varnish as long as nobody cares about the paint job on the shutter shaft bracket.

Josh, if Mark agrees with this, let it soak for 3 days or so in that stuff, and it should be easy to flush out. Give it a good bath, and don't let the bracket holes plug up with paint remnants. Then dry it off, and oil the hell out of it with your Brenkert oil. Don't worry about running out of Brenkert oil...I still have 4 gallons of that stuff for you in a 5 gallon bucket that I use as a telephone table.

Thanks for your input, Mark. I'll talk to Josh tomorrow and see how he is doing with the experiment.

Paul