Compur Rapid shutter on Certo

[johnnyrod]

I have a 1937 Super Sport Dolly rangefinder which I have been cleaning up this week. It has a Compur Rapid shutter which goes up to 1/400. I have hardly used this so knowledge and experience are thin on the ground. I am doing my best to be super careful with this camera.

The shutter is very easy to get into, lenses unscrew by hand front and back (Tessar f2.8, front and middle groups in one unit), the front plate comes off with a few screws and that's it. After removing the speed setting ring it looks like this:
Compur Rapid shutter from Certo Super Sport Dolly by John Rodriguez, on Flickr
I have a few questions if you please:
1. On only the 1/400 speed, whether or not the shutter is cocked, pressing the shutter release to the end of its travel means it stays there. The only way to release it again is to part-cock the shutter until it lets go. Is this a foible of this shutter? It operates fine on that speed if you only go as far as pressing until it fires.
2. I measured the shutter speeds (indicated vs. true) as:
1/400 was 1/180
1/200 was 1/120
1/100 was 1/110-1/130
1/50 was 1/40
1/25 was 1/20
The 1/400 speed uses an extra, heavy spring, seen here at 9 o'clock (the coil spring). I tried adjusting the position of the escapement but it had almost no effect on the speeds. Any thoughts? Aperture and shutter blades look clean and free of oil, I swabbed them quite a bit, also removed and soaked the escapement in hexane though not lubricated it.
3. I found a small pin loose in the shutter, no idea where it's come from. It's made from a small piece of tube so looks like it should be pushed into something. It is the same size and looks the same as the one you can see in the escapement just below the 3 o'clock position. I've been looking at pictures of this shutter from Hans Kerensky and others, and I'm blowed if I can figure out where it came from.

Other than that it's going okay, glass looks good, struts work well, RF seems fine. I would very much appreciate some ideas on this one!
Thanks, John

 

[Ron (Netherlands)]

Here's a nice service/repair manual for the compur rapid:
http://benoit.suaudeau.perso.neuf.fr/manuels_rep/obturateurs/compur_rapid_shutter_repair(2).pdf

 

[Dan Daniel]

1) Look at the bottom of the extra-strong spring. It may be riding into something as the timing plate is pushed into position. Also look at the timing plate and its interaction with the shutter release part and the two levers being activated. Something might be hanging up.

You can put a very light coat of grease on the end of that spring and underneath the timing plate where it pushes against the spring to help things work.

A drop of oil on the pivot of the shutter release parts. A small drop, almost immediiately soaked up with a cotton swab.

A light coat of grease on the inner surface of the cocking ring that is wiped off pretty much completely.

Make certain that the cable release socket is screwed down firmly.

2) What about B and the slower speeds? In general with Compurs you set 1 second and 1/10 second first.

Look at the manual linked above and lube the pivot pins of the escapement.

All in all those are not bad speeds for an 80 year old shutter.

3) Photo? Is B working?

Hard to see all the mechanism in your photo because of the shadows.

 

[johnnyrod]

Ron - amazing, many thanks. I did some inspection last night while testing the shutter, and it takes some figuring out when you are on your own. As the book says, different parts of the escapement work at different speed ranges. for 1/200 and 1/400 it looks like the shutter (main lever) returns as fast as possible with more or less no control by the escapement.

Dan - many thanks for your extensive notes. More for me to do alter but for now:
The high speed spring engages with a notch in the side of the timing plate as you turn it, so appears to be held securely, but I need to look more. When other speeds are selected, it is free to rotate on its mount.
I have some watch oil. Normally I'd put a little on the pivots of the escapement and self-timer although some people would say not - but just a touch as you describe. While cleaning it I couldn't get the self-timer out (the post holding the spring seems to need a tiny wrench with a pair of pins and was stuck fast) and it did look like there was some oil or grease further down in the blade area, so I tried flushing with a bit of hexane. I don't like doing this, there is no guarantee the dirt comes out. I might have to disassemble further to clean all this again to be sure, lube, and hopefully it will then be tip top and maybe even a bit quicker but am a bit wary of unnecessary surgery. My Ikonta also runs at half speed on the faster settings so yes this is not such a surprise for an old camera.
2. B and T work fine, they operate without cocking the shutter which I believe is correct.
3. Will take a picture later of the loose pin. It was stuck in the mechanism somewhere between the shutter release and the cable release although I'm not sure how far it travelled. The only use I've had from this camera was to finish off the roll that was in it, maybe half a dozen shots which were mainly duff because of the age of the film (1950s at best) but it worked fine on various speeds, the only clue was that the speed ring stopped turning as far as B one day.

Thanks again gents

 

[Dan Daniel]

The lever just below the 1/400 spring that is moved by the shutter release button lifts off, I think.The spring itself will rotate and maybe you need to push the shutter button to rotate the lever to a position that will clear the spring. The bottom of the spring has a long extension- you can see it in your photo. Look if there is any interference under there when the spring would be under tension.

If there is oil at the bottom of the case there's a good chance that there is oil on the shutter blade ring itself. That is not good.

 

[Mr_Flibble]

It looks very similar to a Compur-S I've had apart a year or two ago.

On point 2. you are correct, B and T work without needing to cock the shutter.

B and T were malfunctioning on my Compur-S due to the prong of a forked-part having bent half a millimeter out of spec. You can see that partically hidden under the shutter-release part in your photos.

But I don't remember running into any loose tubular pieces in it.

Good luck with the clean-up job.

 

[hanskerensky]

John, just had a look at your Flickr image.

Your shutter looks very much like the one on a Zeiss Ikon Super Ikonta 530/16.

I did a compare with the images I have of that one but could not see any problems at first sight. Of course that loose pin could be a problem but it might as well be just a remnant of a broken cable release.

Here an image of my Compur Rapid :


Super Ikonta 530/16 (12) by Hans Kerensky, on Flickr

 

[johnnyrod]

Gents, thanks for the info, I haven't had time to read the thread Mr. Flibble but I will. A few things to add:
Loose pin from Compur Rapid shutter by John Rodriguez, on Flickr
This has a closed end which is facing away from you, looks like it is made from a small piece of tube. The open end has a slight taper so to me suggest it should be jammed into something (i.e. an interference fit in engineering-speak). A couple of views of the high speed spring and the cable release:
Compur Rapid detail by John Rodriguez, on Flickr
Compur Rapid detail by John Rodriguez, on Flickr
It looks like the cable release is just a piece that holds the screw-in part of the cable, there is a lever than sits just inside the shutter body. Does this look right?

 

[Dan Daniel]

Nothing looks wrong to me in the cable release area. It's if there is interference that problems come. I mentioned the cable release base part because I once had some jamming and strange operations that were because the block was loose and shifting under certain pressures.

I don't see a place where the small tube appears missing. It looks as if it could be the pin on the slow speed escapement, but there is one there already. Aperture and shutter mechanisms on the camera itself?

One difference I see between your shutter and Hans' shutter is in the middle of the self timer block. There is a small tongue, at 6 o'clock in your photo and at 4 o'clock in Hans' photo. The gap in yours is consistent, 1mm or so? In Hans' shutter, that gap is slanted and narrows to a very small opening at the end of the tongue.

I have no idea what this means! It has the appearance of an adjustment point for the speed of a pawl release affecting speed of an escapement, but that's just a guess.

In the manual linked to above, did you notice the different results from moving one end of the slow speed escapement versus the other end? This is important in the Compurs, as I remember.

 

[johnnyrod]

I could be a while investigating before I have some good answers! I don't think the tongue does anything but there are lots of things I don't necessarily know. Re. shutter timings, in all honesty I didn't properly understand that the escapement has a couple of different ways of regulating depending on the speed range, so I was focused more on the pallet end and the higher speeds. Measured speeds were fairly consistent but I really need to look at it again to give a sensible answer about each end. I'm more used to 1960s 35mm rangefinders where the esacepment works just one way, but by varying degrees.

 

[johnnyrod]

I found a bit of time to look at this and have some good news. Hans I misunderstood the comment about the cable release - you meant a bit of the cable release itself, not the receiving part. I think you may be right, I still can't find where else it could have come from. I figured out the jamming on 1/400, which was my fault. I was testing with the fascia plate off, and due to the strength of the extra spring, I was holding the speed plate down while firing the shutter. This was not enough, and the main lever was becoming disengaged with one of the smaller levers - the one in the middle of the last picture, with a screw as a pivot - as the main lever rode up over it, and also then held it in place. The shutter release would then jam without the shutter being cocked as the small lever was already stuck and I hadn't noticed. Putting the fascia back on meant nothing jumped and it works fine.

I checked all the timings from 1 to 1/400. 1 second is 1.6 seconds, 0.5 is 0.6, but the rest up to 1/100 are no more than 20% out. 1/200 is still about 1/120 and 1/400 is still about 1/180 so I think there is more oil down in the shutter area. So, next job is to get in there, clean and lube, then it's as good as it gets. That will definitely need a bit of time to do! The aperture has quite a few blades so am hoping to leave it untouched.

Thanks all for your help, it has made a big difference.

 

[johnnyrod]

An update. I took out the shutter blades and rotating ring, cleaned everything with hexane, and reassembled. The swabs looked dirty though it all hadn't looked that bad to start with, but it's all definitely clean now. I lubed as Dan says above, and sparingly. I haven't moved the escapement so I just tested the speed from 1/100-1/400 and they are just the same as in the first post i.e. 1/100 is actually a bit quicker than 1/200 and the top two speeds run at half speed. 1/100 and 1/200 sound slightly different, I think this is because, as I understand it, the escapement isn't used for 1/200, and it does sound a bit snappier, less going on. So, is this the best case, or is there anything else I can do?

The other camera parts are in need of a good clean so plenty to keep me busy. I found nothing amiss in the bowels of the shutter, and no indication that the loose pin came from anywhere, so I think it did indeed come from outside, which is a relief.

 

[Dan Daniel]

You should pull the escapement, clean and lube, properly adjust the hairspring tension before installing. Also move the spring at the pallet end over one notch tighter in theslotted bracket- you can see this in Hans' photo.

Then adjust for a better 1 second time. Everything starts there. 1 second, 1/10 second. If you still get 1/180 for highest speed, then yep, that's as good as I know how to do. Well, there is adjusting the speed dial notches to fine tune- filing or splaying to get better individual timing.

 

[johnnyrod]

Thanks for the tips Dan, though it took me a while to properly understand what you meant. I had cleaned and lubed the escapement before I took out the shutter blades, think that maybe wasn't very clear. I've spent the evening fiddling, and hopefully it's good news.

Tightening the spring in the notches seems to slow the timings down. It was actually past the last notch so resting inside the escapement casing, minimal tension. I adjusted it first one then another notch, now 1s was actually 2s. Finally I tried to adjust it back but this time with the escapement in place, at which point it slipped back to its starting position, and the timings sped up considerably.

The hairspring was far too tight, my fault for popping the lever out by accident, and just pushing it back in. I reset this and I think it has helped. Results as follows:

1s = 1.13s (1/0.89)
1/2 = 1/1.13 (0.45s)
1/5=1/5.1
1/10=1/8.3 (consistently)
1/25=1/22
1/50=1/45
1/100=1/92
1/200 approx 1/120 (not so consistent)
1/400=1/180

The top two speeds have not changed all the way through. I tried 1/200 while holding the follower of the escapement as far out as possible and it made no difference - it is possible to move it just a little further out when the top speeds are selected, but the manual says it doesn't regulate anyway. I wondered if it was working just a little, but it doesn't seem to be, so that's as it should be.

The middle ones are a touch slow but fine, and at least there is a sensible gap from 50-100-200. The 1/100 is the only one where the follower sits on a slope on the speed ring rather than a flat point, so I've had to be careful to be able to get consistent measurements and so make sense of things.

So, is there any mileage in doing anything else?

 

[johnnyrod]

I have put the photos up here, with notes
https://flic.kr/s/aHskBeuLok