FED slow shutter hits the spot

[fidget]

A while ago, I had my FED3a (one of 10 FEDs) in pieces to fix a shutter release fault and complete a CLA. I learned a lot doing this. One thing was just how the slow speed escapement was engaged by the shutter speed dial. On mine I had problems with the first of these slow speeds, the 1/15th. As the winder nears the end of its travel when cocking the shutter, the very last part of the movement cocks the little clockwork timer. Any variation in where the winder stops will affect the timing of the speeds. The winder on this and some other such shuttered cameras doesn't always engage on that very last tooth of the winder cog, so doesn't cock the timer to the full 1/15th. Times can be much shorter. It's difficult to imagine a fix for this design feature, so I left it as it was, who needs a 1/15th? Well, I did! While running a group of lens tests, more (..oh, so much more....) about this later. I needed 1/15th at f8 as part of the test. I used my mint FED3b, which, you can guess!!! fired audibly differently on a few shots.
In that moment I both knew what the problem was and that I no longer have the will to persue it. Later, I tried in vain to console myself with a browse of FSU gear up for auction, all to no avail. I must be cured!!! :angel: Have I now reached the bottom of that slope? Maybe a Bessa would help?

 

[je2a3]

Did you try tensioning the slow escapement gear train by turning the crown ~ 2.5 turns CCW and then screw it down in place? With this much tension the 1/60 the speed lever control engages the slow speed gear train and succesfully completed a CLA on my Fed3a in this manner with all speeds pretty much on target.

Joseph

 

[fidget]

Joseph,
thanks for the suggestion, it is appreciated. The speeds on my 3a & 3b are all good, except that the 1/15th is unreliable. In this case it looks like the speed selector lever which engages the slow speed pin/cog does not always cock fully back to it's furthest extent. It will do this on all speeds but it makes no difference to the faster speeds as they are timed in a different way, whereas all the slow speeds take their timing based on being "wound up" by the timing cog being turned by the speed selector which is turned by the winder up until the point that the end of the travel is reached. This end of travel is governed by the cog sitting at the bottom of the curtain spool next to the toothed film advance shaft. This has a machined rotary slot which sits on a pin. When you wind the camera this is what stops it winding the curtains past their max point. If at this point the ratchet has not caught the winding cog by being in the trough of a pair of teeth, the train will unwind a fraction until the ratchet drops into the next trough. This reduces the amount that the clockwork mechanism is wound up. I have some cameras which reliably wind and stop at the same point, but some which either need a bit more force to catch that last click or that just don't make it now and then. This difference will be present on all slow speeds, just not noticable on the longer times. It's as though the ratchet cog is not quite round or the teeth are not quite evenly machined. I'm sure that the condition of the clockwork mechanism will have a lot to do with timing issues, the one way mechanism gumming is probably the main cause of non functioning timers and many intermittent issues. Perhaps another look at the problem is in order.
It's strange but, I can excuse this problem on my FED3a but not on the 3b (or 4/5/zorki4k for that matter) as it has the claim to be a "modern" design with winding lever and a full range of speeds.

 

[grifon]

Not sure about the 3B, but i'm pretty sure its the same mechanism as Z4... and on a Z4 1/60th is actually the first speed to employ the slow speed escapement, 1/15th comes next (thats the reason 1/30th is way off on the other side of the dial) and so on.

 

[fidget]

The slow speed is engaged on the 1/15th first on FEDs, but I'm sure that 50th/60th on a Kiev actually does get timed, makes that mechanical sneeze noise, but of course that is a completely different shutter. If you look at any older FED, say the FED2 (or even Zorki 5 or 6), you see the same progression of speeds and their relative position on the dial, the slower speeds were added in the gap between 50/60th and 25/30th using this timer escapement.
My second 3a from thE bay was, as usual, described as working, rare etc. When i got it I found that the clockwork escapement had been removed! The slow speeds causes the shutter to operate at somewhere between 1/50th and 1/25th. Perhaps these have a history of being a problem.

 

[je2a3]

The slow speed is engaged on the 1/15th first on FEDs

AFAIK, the Fed 3a, 3b, 4, 5 and Zorki 4/4K share a similar slow speed gear train arrangement. When these cameras are working properly you can feel a slight resistance as you move the shutter speed dial to 1/60 where it engages the slow speed escapement. You'll hear a slight whiz from the clockwork at 1/60 when the shutter is released and more so at slower speeds except at 1/30 which is the synch speed and is not governed by the slow speed gear train, thus the odd location. See Rick Oleson's note here and his text explanation/comparison of slow speeds in Fed/Zorki vs. Leica .

Joseph

 

[fidget]

I believe that the position of the speeds on the dial mirrors the gap between the curtains as they close. The reason that a 30th is the sync speed is only because the gap between the curtains is the full frame. The physical space between 60th and 30th, (just as per non slow speed FEDs) was simply used as a home for the few slow speeds. The normal speeds work in exactly the same manner as on earlier models. (I am still trying to reason why a 60th would be timed by the escapement yet a 30th is not)
Guess we will have to differ on this one, but thanks for the input.