B&H TQIII 1692 take-up arm issue

[Seb Metens]

I am having a spot of bother with my Bell & Howell TQIII 1692 16mm projector, and nothing I have tried so far has fixed the problem. When projecting a film, loud noises seem to emanated from the rear take-up arm and the rear spool struggles at times to keep a steady speed. The torque also seems very weak; if I provide even a light downward pressure to an empty reel spinning on the rear spindle, it starts to slow and stutter. The front spindle, on the other hand, spins beautifully when I put the projector in reverse. Any advice as to what could be the cause of this and how to rectify the issue would be most appreciated.

Some things I’ve tried:

• I changed the motor drive belt, even though the one already installed didn’t seem in bad shape.

• I opened the rear casing of the projector and greased up the gears that make up the take-up gear train. They all look in good shape cosmetically to my (albeit) untrained eye.

• I removed the rear arm cover to see if I could find fault there. One of the white gears was quite dirty, so I cleaned it up with 99% isopropanol and re-greased. When I turn the gears manually by hand, everything seems to move smoothly. I have read in these forums that with these machines the rubber drive shaft can sometimes get sticky and produce symptoms similar to the ones I am describing. I checked said rubber drive shaft and it does not seem sticky. The cloth belt did have one side which had blackened (the side making contact with the rubber), so I decided to turn the belt inside out to see if that would help things. That, like the other steps I enumerated above, did not prove fruitful.

I attach two annotated photos of the rear arm with the cover off, the annotations describing some steps that I have already taken in trying to remedy the issue.

Lastly, here is a link to a short video of the problem in action https://youtu.be/7Zsa-PpbH9g . In it I first show an empty 2000ft reel placed on the rear spindle and start the forward projector mechanism; one can hear the noise to which I have been referring. The video then cuts to a second clip in which I place my hand very lightly on top of the reel—in an effort to simulate the weight of an actual reel with some film in it—and again one can hear the noise (more so now) and the reel stuttering and slowing down. I really am only applying a very light touch to the spool.

As I mentioned above, any help would be greatly appreciated. I have a copy of the service manual but am at a bit of a loss as to what I can possibly try next to fix the problem.

[Paul Browning]

Are the small gears fixed to the shaft that's turning with a roll pin ?, if not are they turning slower than than the spindle driving them, have they come unattached and under load are just barely turning because of the load, perhaps hold the gear and turn the shafts by hand to see if they are firmly fixed, if not this could be your problem.

[Seb Metens]

Hello Paul and thanks very much for your reply. Apologies if I get some of these technical terms wrong, but I’ll try my best. And I hope I’ve understood what you’ve been trying to explain to me.

I think you may be on to something! Holding down the (white) spur gears—as they are called in the service manual—I am still able to rotate the gear shaft (long black shaft connecting the two spur gears) a bit. The spur gears are fixed to the gear shaft with a retaining ring and retaining clip, but the spur gear closest to the projector isn’t all that tightly fixed; the service manual does talk about inserting a feeler gauge when assembling that spur gear, so perhaps that is normal?

Again, it is probably best to see this in action with a short clip, but I shall also describe the video’s contents below in the event that the video is ever removed.

https://youtu.be/EG_-4-e0ZTw

I did not show holding each spur gear still and trying to rotate the shaft as it’s difficult to do whilst filming, but the shaft does rotate, as mentioned above. In the video, you can see me rotating the gear shaft in either direction, with a close-up of each spur gear. The upper spur gear (as it’s called) does show a more hesitant movement than the other one.

Would you recommend disassembling the whole rear arm assembly and fitting everything back together, or could I just tighten those retaining rings/clips without doing all of that? Is there a special tool you would recommend to tighten a retaining clip? I notice there are two little holes (to grip the clip, no doubt).

[Maurice Leakey]

Seb
Would the service manual help you.
See page 18, A3.8.1 Rear Reel Arm.
BHTQIII.pdf (film-tech.com)

[Seb Metens]

Hello Maurice. Thanks, and apologies for the delay in replying. I do already have the scanned service manual as provided by Film Tech. I found that some of the photos and figures at the end were missing, so I also bought it elsewhere.

After inspecting the rear arm mechanism again and moving the gears manually, I spotted where the problem was coming from: the lower face gear was not snug against the lower spur gear, causing the mechanism to stall at times. To fix the issue I loosened the set screw (14 in the service manual) holding the gear shaft (16) in place, and moved the latter so that the lower face gear made good contact with the lower spur gear. I then retightened the set screw; a 1/16 inch Allen key is needed. As per the service manual, there should be a very small amount of backlash between the two gears, so a small amount of wiggle room is recommended—though only a *very* small amount!

I spent the last few days testing the fix—first with a 400ft short, and then an approximately 55-minute 2000ft reel—and the take-up now works as it should: no loud noise, no stuttering.

Thank you, Paul, for pointing me in the right direction and making me look more closely at the gears in the arm. Thank you Maurice, too, for the link to the service manual, even though I already had a copy. I appreciate it!

[Maurice Leakey]

Well done Seb.