How does the position of my camera affect how the shutter performs?

Question

I have a Speed Graphic Pacemaker. I suppose that everything works fine, except for the focal plane shutter at the back. All the speeds seem to be accurate when the camera is sitting normally, but when it is sitting on its side (where you would attach a flash gun) the shutter speeds are affected and are slower.

The interesting thing is that if I hold the camera upside down then the shutter still works normally, and if I hold it in any position, just holding it to the side gives me shutter problems. What could be causing this and how do I fix it?

Answer 1

The focal plane shutter consists of a spring loaded curtain. To operate, you wind a spring that is similar to the type of spring associated with wind-up clocks. When setting the shutter speed, you are actually adjusting the width of an opening slit. When the shutter is activated, the spring loaded curtain unwinds from a supply roller and winds onto a take-up roller. This focal plane mechanism is thus dependent on the spring tension and the friction happenstance of the rollers etc. Likely as you reposition the camera, gravity changes the friction. I would start by lubricating the roller bearings and observing the travel path for unwanted rubbing etc. It would not surprise me if the curtain material has become stiff and brittle. Add this to a spring that likely has taken on a set and thus is weak.