Spring for Synchro-compur shutter

[Yourix]

Hi there !

I am looking for a small spring to repair the Synchro-Compur #0 MXV CN-1210-051 mounted on my 90mm Super-Angulon.
It's the one you can see on this picture i found on the internet, below the "half-geared wheel" ::: https://www.flickr.com/photos/myster...ol-camerapedia

And here is the (broken) spring :::


It's about 7mm of outer diameter (6mm inner).

I would be thankful for any advice about where to find this little thing... I'm in France but this shouldn't be a problem given the thing is so small...

Thank you for reading !

[BrianShaw]

This might be too small; you should ask the seller. Mainsprings aren’t easy to find.

https://www.ebay.com/itm/ROLLIEFLEX-...-127632-2357-0

[Yourix]

This might be too small; you should ask the seller. Mainsprings aren’t easy to find.

https://www.ebay.com/itm/ROLLIEFLEX-...-127632-2357-0

Thank you for the link. Not the same spring but it looks like it...
Actually I don't think the one i'm looking for is the main-spring of the shutter (the one that open the blades) but the one that pull the coking lever back to it's initial position when you fire the shutter.
I say "I think" because i'm not repairing this shutter myself, I gave it to my neighbour (retired watchmaker) because my local store say they don't have the spare parts to repair it.

[BrianShaw]

https://www.ebay.com/itm/17489093648...Cclp%3A2047675

[Yourix]

A little update as this shutter was successfully repaired by my skillfull neighboor...

There was 3 springs broken in this old shutter... one for the opening lever, one i don't know why and... The main one ! (picture above).
The two first where easy to replace because they don't have to be very precise in diameter, lenght or torque but for the main one it was an other story...

It has to be of a very specific thickness and diameter to fit in place, and it's power has to be of the very exact force required to power the shutter. Too strong and the echapment can't work, too weak and it get stuck...
The original spring had 9 loops and was made of a flattened wire of 0,3mm by 0,5mm that is impossible to find.
By grinding a 0,5mm wire with a flat stone my neighboor was abble to make it but then it was impossible to use it to make the spring... because of it's flat sides it keeps twisting when rolled in the desired shape...
So he ended up doing it with a regular 0,5mm wire, with only 7 loops to keep it the right thickness. It was a game of trials and errors and he had to make dozens of it to finally reach the right force !

At least he succeded and it's working again. I tested it and of course the speeds are off by 1/3 to 2/3 stops (too slow) but this is not uncommon for old shutters and it is perfectly usable for me who shoot mainly in b&w... It's now back on his SA 90mm and in the fields for some landscapes...
Kudos to my neighboor !

[ic-racer]

Great save!
I was just reading about springs in the on-line shutter repair course yesterday. You found a good solution.
Also, the way I look at it, shutter speeds are never ‘off,’ they are always exactly what the shutter speed tester indicates.

[sharktooth]

Your neighbour is very resourceful and deserves a tip o' the hat for both ingenuity and dedication.

I've was thinking about the possibility of making leaf shutter springs a while ago, and your post reminded me about it. I've designed many springs in my career, but they weren't for cameras. If you know the wire sizes, coil diameter, and number of windings, it shouldn't be difficult to design a spring to replace it. Even if you can't find the same exact wire size, it should still be possible to get the same effective output from a slightly different wire by changing some other parameters, as your neighbour has done. To make a spring, you need a spring winding machine, wire, and setup cost. There isn't really any special new tooling required, so the primary cost is in setting up the machine to run the springs. It's not really much different than making a custom machined part, like S.K. Grimes would do. The main cost is in setting up the machine to run the part, and the running time on the milling machine or lathe. With a spring winding machine, the running cost is negligible, since the part can be done in seconds. The primary cost of a custom spring is going to be the time involved to change the setup in the machine. Since the per piece cost of the wire, and the running cost are negligible, compared to the setup cost, you could get hundreds to thousands of springs for pretty much the same cost as one spring. For example, I'm guessing that if you invested a few thousand dollars to get a spring supplier to make a special prototype run, you could get several hundred to a few thousand springs. The cost for each spring would be a few dollars. If you could sell them on for $20 or more, then there might be a good business case to do it. I myself think I would be happy to pay $20 to save a leaf shutter, but I'm not sure what the current and future demand is like.