DIY repair a SCNOO triggerwinder for Barnack Leicas

Some time ago, I suddenly was certain I needed a trigger winder on my 1938 Leica IIIa. Not having a transport lever on the camera made it a bit slow in use when I am shooting in the streets.

The Leica-made trigger winder is in fact a trigger bottom plate. It takes the place of the normal bottom plate, it has a spring to make the trigger return and that construction has one flaw: the trigger is connected to the film winder axle with the spring by means of a silk ribbon. And these ribbons sooner or later always snap.

When my trigger winder (Leitz code word SCNOO) arrived, I could start repairing it straight away, since the ribbon was torn when it arrived. I took out needle and thread and did a fine job and for three or four rolls of film I was a happy snapper. But then, the ribbon broke again. Grmpf.

So, I decided on a more permanent solution. And in the process created a pictorial on the repair I did. Here it goes.

Before you get the wrenches out, here’s the how and what:

  • I work on a soft cloth, the synthetic kind. Any screw dropped won’t budge from the moment it hits the cloth.
  • Only use screw drivers that actually fit the screws. And you’re going to need a set of jewellers screw drivers, because these screws are small!
  • Bring a pound of patience, a steady hand and evict all family, pets and visitors for an hour and a half. I’d say double that time if you are all thumbs.
  • Never force anything, there’s blunt brass screws in the SCNOO and if you apply force where you should not, you will wreck them. Buying another SCNOO for spares is not an option, they do not come cheap.

This is the SCNOO. The ribbon is supposed to run from the trigger to the big drum on the right. But it snapped and it’s in the drum now and leaves the trigger useless.

Here, I took out my secret tool to get the SCNOO fixed:

It’s a pocketable tape measure. The one with a metal strip that retracts by itself when released. Some people keep them on their keychains. Read on to see what we’re going to do with that thing.

Start with the small trigger side of the SCNOO. Two smaller screws keep the top plate of it secured, the third bigger screw is actually a small threaded-and-slotted pin that the ribbon is sewn around. Cut the ribbon off. Put all parts aside.

Next, I’m taking out the three screws on the inside of the bottom plate that keep the drum fixed to the bottom plate. Put screws and drum aside. There is a black (plastic? bakelite?) ring inside, that is slotted for the ribbon to slide through. Put that aside as well. Remember orientation before removing.

The ribbon is coiled onto the brass large-diameter axle that you see on the right. The crescent-shaped brass collar with the two blunt brass screws lying inside it secures the ribbon to the brass axle. The ribbon is clamped between the axle and the brass collar, the two screws tighten the collar to the axle, with the ribbon inbetween. Like this, the ribbon is tightly connected to the axle without the risk of being torn off anywhere. Again, study orientation of the brass crescent collar throroughly before removing.

I used the ribbon as a template to cut a similar length piece of metal from the ruler. You might want to have a good look when copying the ribbon length, you need to measure approximately 4 millimeters beyond the second screw hole in the brass axle, and also add 6 millimeters to the trigger side so that you can fix it to the trigger later on.

Re-connecting a piece of the metal ruler tape to the axle, put the collar on just for the shot…

Here, I left the paint on the metal ruler ribbon so you can see what I’m using. I planned to keep the print on it as a little joke, but soon found out I really should not… More about that later.

I drilled two little holes in the metal ribbon, again using the original ribbon as a template. I made them a full millimeter wider than the screw diameter, so that I would not have too much trouble lining them up against the holes in the collar and the axle. This proved to be a good idea. Taking the paint off here was also wise, since it made the metal ribbon fit between the collar and the axle a bit easier. The paint wasn’t as smooth as the metal, sliding the ribbon in between the collar and the axle was a lot easier without any paint interfering.

Here, I have (clockwise!) wound the spring that provides the return tension up as tight as possible. I’m keeping it fixated with my finger while winding the metal ribbon on the axle. BAD IDEA: this is where I later decided to take the paint off, and use small round-beaked pliers to bend the metal ribbon. Why? Because the ribbon wants to take on its original form (straight) and that locks it up inside the black plastic/bakelite drum. The return spring then simply cops out, it cannot apply enough force to pull both the metal ribbon and the trigger back. To see my final ribbon result, have a look at the last picture of this pictorial.

Here I have already installed inner bakelite drum and outer brass drum. Inside, the return spring tension is tightly wound at maximum and I have extended the metal ribbon, made a small-diameter round curl at the end and fitted that around the pin that secures the ribbon into the trigger. This is simple re-assembling.

When I was done the first time, I made a 26-second movie to show how the SCNOO works with the new metal ribbon:

Cool, huh?

Like said above, you wanna remove all paint and use small round beaked pliers to make the new metal ribbon coil up on the brass axle inside. This will make sure that the ribbon will not ‘expand’ inside the bakelite inner drum, and freeze things up.

Once that is done, this is what your final result could look like:

Best of all: this might last for another seventy years without ever breaking. I applied a really small amount of lithium grease to keep rust away from the surface. And also very cool: from a meter distance, there really is no telling that this is a metal ribbon, it looks just like the real deal.

I hope this pictorial is of any use to those of you that consider buying a SCNOO. When I first considered buying a SCNOO I was told straight away that I should forget about them because the ribbons always break. Yet, they are really nice and cool trigger winders and I’d be happy to see any of them be brought back into service with this repair.

To go, a picture of the repaired SCNOO on the little IIIa. The camera was as nice as they come (upgraded to a Leica IIIa-syn, a flash-enabled and flash-synchronized version in the 1950’s), it has a 1.5x viewfinder that is ideal for focusing fast lenses like my 50mm f1.5 Sonnar lens) and I had it covered in grey leather, with an M4-type film reminder dial at the back. Truly one of a kind, now why did I let go of that set again…?

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