View Full Version : Focusing gear trouble

21-May-2009, 09:42

I did a little overhaul of a "new" sweet little Charten 5x7 I got recently - the camera is a beauty and now that I lubricated the moving parts it's smooth as it should be. With one little problem…

The camera has, like all field cameras, two focusing knobs at the right, one in front and one at the back, to be used for close and far focusing respectively (well, kinda - you get what I mean?). Now the cog-wheels on the front knob that move the front system "disengaged" themselves - maybe I should not put a drop of lubricant on those cogs? When turning the focusing knob the rod spins without the cog-wheels moving. Why did that happen? And mainly - how can I fix the issue? Is this something field camera owners encounter every now and then, or am I alone with the problem?

Any suggestions on how to take it from here would be welcome!

Kind regards,

21-May-2009, 09:55
Sounds as if the pinion is no longer fixed to the rod.
The fresh lubrication- if it has seeped into that joint, may defeat the easiest solution- cyanoacrylate [super/crazy glue] in the space.
If the original affixation was a press fit glue with replace it. Or there may be a shear pin. If so, it would be visible at the "valley" between gear teeth. If the pinion is large enough it might have been a setscrew that has unset and/or fled
Got pics?

21-May-2009, 12:17
Ed, thanks for your suggestion. It might look like the cogs were held in place by friction, there doesn't seem to be any pin. And I doubt that a setscrew went missing. I doubt the screw you see in the very end on the knobs is of any help - it looks more like the screw to just keep the knobs from falling off. So the superglue would have been an option - except that I doubt it has any effect now if some lubricant got in there… I attach some quick pics I took - not sure whether they are of any help.

Any more suggestions? :)

21-May-2009, 12:53
By the looks of it: tighten the screws inside the focussing knobs and see what happens, it might work.


21-May-2009, 12:59
Peter, thank you - that sounds like a good suggestion, will try it tomorrow morning. But first I'll need to make myself a tool for the job (there's a pin sticking right into the screw groove, so a normal screwdriver won't work…)

Ernest Purdum
21-May-2009, 14:38
Your problem is better than the more common ruin of the gear teeth.

I'm afraid you are going to have to take the assembly out, clean very thoroughly, and then either glue or silver braze the pinions to the shaft. A hazard here! The gears must be held by, or sitting on, something that will keep them in the identical relationship to the shaft as the glue sets or the silver hardens.

22-May-2009, 01:33
Thanks for all the suggestions! It was not the screws inside the focusing knobs (they really are only for preventing the knobs to fall off). It was also not possible to unmount the whole thing - it wouldn't move any further than a certain point, and I did not feel like forcing it. But at that point I had enough play to clean the shaft and roughen it up a bit. A drop of glue and the thing sits tight again (and still moves ;) ). Ernest's caveat was helpful - made sure I didn't forget about that detail :)

Thanks again,


Doremus Scudder
22-May-2009, 01:35
You might try applying some Loc-Tite or similar product carefully to the exposed juncture of pinion gear and rod while the gears are engaged in the rack (i.e., do not disassemble the camera). This will ensure that the pinion gears do not get misaligned. Just a thought...


Doremus Scudder