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Focal Plane Shutter Servicing

 
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Joined: 28 Sep 2001
Posts: 3233
Location: Mid Peninsula, Ca.

PostPosted: Tue Apr 15, 2014 5:09 am    Post subject: Focal Plane Shutter Servicing Reply with quote

When servicing your FPS measure the roller shafts and ID of their bearings. They should be within .001 inch of one another. You will most likely find they are elliptical shaped from wear, not perfectly round.

I have found that excessive side play in the roller shaft and its bearing results in sluggish FPS operation.

In resolving the sluggish shutter in my worn out RB Series B I made a shutter speed tester, http://graflex.org/helpboard/viewtopic.php?t=6105 , using 2 sensors placed diagonally on the film plane 1/4 inch inward from the top and bottom edge of the film opening and 1/4 inch inward from the outer edge of the frame. The recording results in two waveforms that start and end off set from one another. I use http://www.openoffice.org/ spreadsheet to record the results in. I list the top sensor time, the bottom sensor time, their average, the time from lead edge to lead edge, and the time from trail edge to trail edge then calculate the difference between sensor times and edge times.

A difference of more than .001 inch between the roller shaft and its bearing needs to be shimmed/sleeved to bring the difference to .001 or less but the roller must turn freely in the bearing.

The difference between sensor times and edge difference will be far apart on shutters with more than .001 inch difference in diameters and they will be the same or less than .002 second apart once the shaft and bearing have been shimmed/sleeved. The shutter speeds will come in closer to accurate from 1/10 to 1/500. The Series B tested 7 speeds good before shimming the bearings and 11 speeds in tolerance after shimming, a Anniversary Speed showed 10 speeds good before and 10 good after but a different set of 10 with slow speeds testing fast where they were slow before. A series of exposures from 1/1000 to 1/30 shutter speeds shows even exposures. https://www.flickr.com/gp/thirteenthumbs/7m95gN/
Exposures are from left to right 1000, 500, 240, 125, 60, 30. The images are crops from 4x5 Arista EDU Ultra 400 processed in HC110 @68F. They have been spotted. They were scanned on an Epson V500 at 4800 dpi and resized. No adjustment to the histogram or levels was made. The tones are the same as if they were wet printed at paper black.

If I had a lathe I would turn the roller shafts and sleeve the bearings but for now I'm using .001 brass shim stock cut to fit the inside of the bearing as needed according to the amount of wear.

The wind gear and tension setting ends do not appear to wear as much as the bearing end.

Any camera I have previously serviced that still has a sluggish shutter I will shim for the cost of shipping only.

Photos from the Series B will be posted in the near future.
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