Danger of leaving shutter open?

While I would never store a lens with the shutter cocked, it might be

useful to store lenses in the bag with the shutter opened and ready

for viewing upon mounting. My shutters are Copals or Synchro Compurs

of various vintages. Do you think that putting a lens away with the

shutter opened would result in the same kind of wear problems that

storing a shutter cocked would bring on? Opening a shutter for viewing

doesn't feel as though it is tensioning springs, but since I've never

looked inside I don't know.

Tony,

I have two schneider lenses. I have been using them for over twenty years and have usually stored them with the shutters open. I have never had a single problem with the shutters or any other part of the lenses. I do not think it is advisable to leave the shutters cocked, though, as it may weaken the springs over time (I assume).

One PNetter pointed out to me in a rather condescending note that springs don't lose their tension. However, I probably wouldn't store it with the shutter cocked. No reason to place undue tension on the components, if it's not necessary.

New copals are boxed with open shutters, so apparently the manufacturer doesn't think it

is bad for them.

Jason, the shutters are probably moved to the "focus" position, rather than set to "T," cocked and then fired. That would be different. The "focus" position is like the "T" and "B" on old Compurs that didn't require you to tension them first.

All springs back off in tension; at the micro level. The creep increases with temperature. A shipped shutter can be baked in a truck for days; and the tension will relax abit. Creep curves for spring materials vary with each different spring material. Do you know what each material the spring is in every one of your photo items? Did a jackass manager get a raise subsituting a lesser material; just to keep the assembly line going? Here I have had to recall items; due to spring creep; for products in the field. Saying springs dont creep at all is abit idiotic. At working temperatures; springs when properly selected creep only a small amount during service life. Music wire has excellent strength; but only average high temperature robustness. Springs used in engines; hydraulics; miltary gear; have a higher temperature creep temp. <BR><BR>Some older compurs have a helper spring for 1/500 second; that is much higher stressed. The old adage about not leaving a camera cocked came from springs like this getting weak after a camera is left on a hot cars dashboard. <BR><BR>A black car dashboard can go well over boiling; in a closed car. <BR><BR>In engineering testing; items are placed in ovens; and heated and cycled; to measure the drop in spring tension versus time. Many times if the data is great; the bean counters will have the engineers run tests on cheaper springs. Here the creep is more at a given temp.<BR><BR>In camera repair; replacing the 1/500 helper spring is often done; to make the speed higher. <BR><BR>The biggest danger; is not giving your shutter regular exercise. I wouldnt worry much about spring creep at room temps. In hot applications; hot cars; unknown transport; why add extra creep?

"One PNetter pointed out to me in a rather condescending note that springs don't lose their tension"

 

A classic application of "a little knowledge is a dangerous thing" - this is probably the result of a limited recollection of a school lesson he half slept through... Hooke's Law only applies to idealised springs, operated within their elastic limit. In the real world, with real materials, springs will deform when used.

 

Cheers,