Compur with funny speeds

SalveSlog · Sep 7, 2014

A Compur from the early 30ties on a Voigtländer Inos has these speeds:

1/1 is 1/1.2
1/2 is 1/2.8
1/5 is 1/9.4
1/10 is 1/38
1/25 is 1/109
1/50 is 1/122
1/100 is 1/112
1/250 is 1/162

The seller who had done CLA on it, but only tested by sight and sound, said this was not possible. But asked me to return it. Which I did. He probably don't believe my measurements.

Any comments on these speeds? I'd like to learn more..

John Koehrer · Sep 7, 2014

As you say, most of the speed are off. And, they're way out of any official tolerances.
ISO tolerances aren't really tight, around +/- 20% at slower speeds and +/- 30% at higher ones.

What did you use to get the accuracy to those decimals?

SalveSlog · Sep 7, 2014

I buildt a tester from this instruction:
www.baytan.org/prak/shutter.html

I use Sox (an audio application) for recording a text file of the signal
and Octave (a free alternative to Matlab) to analyze it.

shutterfinger · Sep 7, 2014

Compur tolerances are 15% on speeds from 1 second to 1/100 second, 20% on speeds 1/125 second and faster; most other shutter manufacturers use 20% on speeds from 1 second to 1/100 second and 30% on speeds 1/125 second and faster. The wider tolerances are equal to 1/3 stop of exposure.

See the last two posts in this thread on photo.net http://photo.net/large-format-photography-forum/0044cW?start=10
works well.

The Compur shutter delay mechanism is positioned to set the speeds correct. Adjust the left end in/out from shutter center to set the 1 second speed. Depending on vintage adjust the right end for 1/15 or 1/25 second. All other speeds should be correct when these two are set correct. If the other speeds are not correct the delay tensioning spring needs to be adjusted/replaced.

fotch · Sep 7, 2014

"The seller who had done CLA". Well, maybe the quality of the CLA is worthless. Did he really do it or just picked the cheapest? If it were me, I would rather pick the person who was going to do the work & not pay any premium in the purchase.

SalveSlog · Sep 8, 2014

Thanks for answers. The funny thing is that speeds are faster, not slower. Is this common? How can that happen?

shutterfinger · Sep 8, 2014

Compur shutters use a spiral torsion spring like a watch main spring. If it is set too tight it will prevent the delay mechanism from setting to its full delay. If the delay housing is set too far from the center of the shutter housing it will not be set to the proper delay at any speed. If the person trying to do the CLA just flushed it or refreshed it with new oil then the delay mechanism may be sticking and not delaying the closing of the shutter resulting in faster speeds.

Correct operation:
Cocking the shutter sets high tension on the drive and locks the mechanism from moving.
Tripping the shutter releases the blade controller which opens the blades to full open in .1 to .3 milliseconds.
When the shutter blade controller reaches full open the cocking spring tension is applied to the controller in the closing direction and unrestricted will close the blades in 1/100 to 1/125 second.
When slower speeds are selected the delay mechanism restricts the application of the cocking spring tension for a predetermined time then allows the full closing force to be applied.
When speeds faster than 1/100-1/125 are selected booster springs are compressed in cocking and released on tripping applying additional force to close the shutter.

Depending on what the person did or did not do to CLA the shutter will tell why it does what it does.
The 1 second adjustment can be set to roughly .6 seconds at the fast end; the 1/25 adjustment can be set to approximately 1/45 second.

Speeds above 1/125 frequently show 1/2 to 1 stop slow on testers but exposures show them to be accurate to 1/2 stop slow.

According to your test chart it is poor adjustment of the delay mechanism.

SalveSlog · Sep 8, 2014

Thanks a lot, shutterfinger!
I kind of regret I sent it back for repair, but have to wait and see if he can put it right this time. If not, there may be a chance I can do it myself.

E. von Hoegh · Sep 8, 2014

SalveSlog said:
A Compur from the early 30ties on a Voigtländer Inos has these speeds:

1/1 is 1/1.2
1/2 is 1/2.8
1/5 is 1/9.4
1/10 is 1/38
1/25 is 1/109
1/50 is 1/122
1/100 is 1/112
1/250 is 1/162

The seller who had done CLA on it, but only tested by sight and sound, said this was not possible. But asked me to return it. Which I did. He probably don't believe my measurements.

Any comments on these speeds? I'd like to learn more..

"All speeds sound good!"

You've just posted the translation of that statement. Does the shutter smell like lighter fluid?

BrianShaw · Sep 8, 2014

shutterfinger said:
...
According to your test chart it is poor adjustment of the delay mechanism.

concur. That's what I've been thinking all along.

shutterfinger · Sep 8, 2014

I picked up a print copy of this manual: http://www.suaudeau.eu/memo/rep/Compur-shutter-repair-manual.html about 20 years ago for $40. Shop around ebay and camera manual sites and you may find it still available for roughly the same price or download all the sections and print them. The service Instructions section only tell you the special settings for that shutter. There are no step by step disassembly/reassembly instructions. The diagram numbering is assembly order, lowest number first.

The manual is picture breakdowns of the varrious shutters made in the 1950's. They are listed by camera type-lens to find the appropriate shutter diagram.
If you cannot find your lens type in the list then remove the top plate and possibly the speed setting ring, which may require disconnecting the main setting spring. Now look through the diagrams and find the shutter that closely matches what you have.

A while back I was given a 135 Xenar in Compur Rapid shutter. It had a lot of internal rust with some levers stuck. I saw a tip on American Restoration to put rusted metal in cider vinegar for 15 to 30 minutes then wash with water and treat with oil or paint so I tried it on the shutter parts and it worked like a charm.
Looking at the service manual there was no listing for the lens/shutter combination. I looked through the diagrams and found one that matched the top side of the main plate but upon full disassembly found the lower side to be different. Looking through the service manual more I found another diagram that had the lower section that matched my shutter.

The top side of the main plate has the cocking, delay, flash sync, and self timer mechanisms; the lower side has the blade controller, shutter blades and aperture mechanism. The aperture blades are a Bear if there are more than 5 of them.

BrianShaw · Sep 8, 2014

SalveSlog said:
Thanks a lot, shutterfinger!
I kind of regret I sent it back for repair, but have to wait and see if he can put it right this time. If not, there may be a chance I can do it myself.

No matter who does the work, it should be clearly understood that one cannot remove and clean the delay mechanism with no knowledge of how to ensure that it is replaced correctly. As has been pointed out earlier, the adjustment of the delay mechanism is critical to ensuring that the timing is correct in the timing range that uses that assembly. Also, it should be mentioned that proper lubrication is important... as defined by the repair manual.

E. von Hoegh · Sep 8, 2014

shutterfinger said:
I picked up a print copy of this manual: http://www.suaudeau.eu/memo/rep/Compur-shutter-repair-manual.html about 20 years ago for $40. Shop around ebay and camera manual sites and you may find it still available for roughly the same price or download all the sections and print them. The service Instructions section only tell you the special settings for that shutter. There are no step by step disassembly/reassembly instructions. The diagram numbering is assembly order, lowest number first.

The manual is picture breakdowns of the varrious shutters made in the 1950's. They are listed by camera type-lens to find the appropriate shutter diagram.
If you cannot find your lens type in the list then remove the top plate and possibly the speed setting ring, which may require disconnecting the main setting spring. Now look through the diagrams and find the shutter that closely matches what you have.

A while back I was given a 135 Xenar in Compur Rapid shutter. It had a lot of internal rust with some levers stuck. I saw a tip on American Restoration to put rusted metal in cider vinegar for 15 to 30 minutes then wash with water and treat with oil or paint so I tried it on the shutter parts and it worked like a charm.
Looking at the service manual there was no listing for the lens/shutter combination. I looked through the diagrams and found one that matched the top side of the main plate but upon full disassembly found the lower side to be different. Looking through the service manual more I found another diagram that had the lower section that matched my shutter.

The top side of the main plate has the cocking, delay, flash sync, and self timer mechanisms; the lower side has the blade controller, shutter blades and aperture mechanism. The aperture blades are a Bear if there are more than 5 of them.

Acetic acid. Any vinegar will work, I've used white distilled vinegar. Acetic acid stop bath works too.
The tannic acid in strong (say three bags per cup) tea will reduce the rust as well.

American 'restoration'... I saw one show where he made an absolute mess out of a pretty nice original Atwater Kent metal cased radio, one of the art deco ones. He destroyed the decent original wrinkle finish paint and repainted it with semi gloss. He didn't mask the little brass bits like the tuning index either.

shutterfinger · Sep 8, 2014

No matter who does the work, it should be clearly understood that one cannot remove and clean the delay mechanism with no knowledge of how to ensure that it is replaced correctly.

Actually on my first delay mechanism I had to figure out how it was suppose to work, experiment with the tension spring tensioning then put it in the shutter and set according to the manual and test to see if I had it right.
Most Compur delay mechanisms are riveted together so the gearing cannot be removed from its frame but the tensioning spring is easily released.

On Compur shutters from the 1930's-1940's there are levers riveted/staked screwed to the main cocking ring that sit into recesses in the case. If they are not in their proper recess the shutter will go together but work as described in the first post in this thread.

Any vinegar will work, I've used white distilled vinegar.

The one time I tried white vinegar it did not work.

BrianShaw · Sep 8, 2014

shutterfinger said:
... and set according to the manual and test to see if I had it right.

Yes, thank you... that was my point to the OP. I worry about folks who think it is easy to properly CLA a shutter without a manual or test equipment.

E. von Hoegh · Sep 9, 2014

BrianShaw said:
Yes, thank you... that was my point to the OP. I worry about folks who think it is easy to properly CLA a shutter without a manual or test equipment.

As well as without tools, skill, and experience.

removed account4 · Sep 9, 2014

SalveSlog said:
A Compur from the early 30ties on a Voigtländer Inos has these speeds:

1/1 is 1/1.2
1/2 is 1/2.8
1/5 is 1/9.4
1/10 is 1/38
1/25 is 1/109
1/50 is 1/122
1/100 is 1/112
1/250 is 1/162

The seller who had done CLA on it, but only tested by sight and sound, said this was not possible. But asked me to return it. Which I did. He probably don't believe my measurements.

Any comments on these speeds? I'd like to learn more..

sorry to sound like a country bumkin, but why would someone buy a something used and not figure it needs a CLA
no matter what the person who sells it says ( unless they do CLAs themselves that is ).
some people tend to say anything they want, true or false to sell something they have.
i have more than one story of sellers ( here and on eboo ) who are FOS and sell things by misrepresenting the truth.

Dan Fromm · Sep 9, 2014

John, leaf shutters are like people. They never get old.

BrianShaw · Sep 9, 2014

... and they all lived happily ever after.

removed account4 · Sep 9, 2014

Dan Fromm said:
John, leaf shutters are like people. They never get old.

Compur with funny speeds

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