I will have to try removing that retaining ring and go from there. I'm afraid that even if I can do that and release the tubing so that it comes out the front, I still may not be able to get the disk out of the larger hole in the back of the drum but I don't have anything to lose at this point so I'm going to give it a try.
Thanks,
Barry - N4BUQ
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----- Original Message -----
From: "Jim Adney" <jadney@...>
To: "tekscopes" <[email protected]>
Sent: Friday, December 17, 2021 3:44:35 PM
Subject: Re: [TekScopes] Internal Drive Mechanism for 7B53N (et., al.) Sweep Speed Cam
Yes, it's clearly been a long time since I've had to work on one of these. I was
thinking that pulling the drive dog forward would disengage the drive dogs from
the rear drum, but that bothered me, as something in the back of my mind kept
saying, "A Sweep in front, B Sweep in back."
So the interlocking is done by the knobs and the drive dogs continue to turn the
rear drum even when its shaft is pulled forward.
Thanks, that makes more sense.
For the original poster: If the front knob does not turn the B drum, does it
turn the 1/8" B drum's shaft? If it does, but the B shaft does not turn the B
drum, then the drive dog has either shattered (most likely) or come loose from
the shaft. You'll have to remove that retaining washer from the shaft to get it
apart. That can be tricky, or you can destroy the washer and buy a new one at
your local hardware store.
Does anyone have a better name for that kind of retaining washer? It looks like
an internal star lockwasher, but the inside spikes flare in one direction so
that it can be pushed on but can't be easily pulled off. McMaster-Carr calls
them Push-On External Retaining Rings.
