Storage of Mamiya RB lenses

[brett_kosmider]

This is one of those questions that the amazingly detailed manual (not) for the RB Pro-S

fails to answer:

 

When storing lenses for the RB should I leave the shutter cocked or uncocked? Also, I keep

at least one lens mounted to the camera body while in storage in my camera bag - should

I leave the camera cocked (ready to take a photo, mirror down, shutter cocked), or

uncocked (mirror up, shutter closed)?

 

Sounds silly, but my gear has been idle the last couple months and it dawned on me I

should probably keep it stowed away in the correct way.

 

Thanks

BK

[paul ron]

Uncocked is the way to go. Springs tend to weaken if left in tension. Uncock the body as well for the same reasons.

 

Just a note... long term storage is really bad for a mechanical camera. These beasts like to be used. If parts are left to oxidize and lube cakes up on you the camera will need a good CLA before it can be used again.

 

If you do plan to store the camera long term... having the CLA done prior to storage is a good idea, since newer lubes are less likely to cake up like older lubes are notorious for. Desicant packets are good to include in teh case to reduce humidity and prevent fungal growth in the lenses.

[ronald_moravec1]

Shutter uncocked and set to B. Do not store lens up. My pro-s developed a strange noise after this. Sounds weird, but this was the normal position in the aluminum suitcase made for it.

[q.g._de_bakker]

Paul,<br><br><i>"Springs tend to weaken if left in tension."</i><br><br>A myth. ;-)<br>There is absolutely no evidence supporting that statement.<br><br>Springs weaken by repeated releasing and tensioning. Good-old metal fatigue setting in.<br>But tension itself does precious little.<br><br>So don't worry, and store your cameras and lenses with every spring tensioned. You'll be ready for action faster, and mechanisms "under stress" are more resiliant, stand up to shakes and bumps better.<br>So no reason not to leave springs in tension, two reasons to do leave springs in tension. An easy choice? ;-)

[dalahorse]

Two opposing theories so far... Interesting!<p>

It is good to exercise lens shutters once a month or so to prevent lubricants for solidifying and/or building up on the shutter blades. It only takes a few minutes to take out all of your lenses, cock and fire each of them once at each shutter speed, and pack them away again. I open and close the aperture a couple of times when exercising my lenses, too.<p> I leave my lenses and camera uncocked when they aren't in use.

[paul ron]

If you insist the unloaded spring care suggestion is a myth, can you supply us with a published paper that supports your statement? In all the years I have repaired cameras and clocks I have, professionally, been advised to unload springs before long term storage. I forgot to mention also as someone pointed out, setting the shutters's speed to it's slowest setting. Shutters are very accurate mechanical clocks and should be treated with the same respect. Below you'll find a quote from a paper published by a clock restorer on proper long term storage and care of mechanical antique museum clocks.

 

"If a clock is to be left stopped for any length of time, allow it to run down fully if it is spring wound. This stores the spring in an unstressed condition. A weight-powered clock can also be run down to remove the loading from the gear train, but this may allow the weight cords or chains to hang out of the winding barrel on their securing lines alone. For this reason, it may be wiser to stop weight-driven clocks in a partly wound condition."

 

As for shipping shutters in a cocked state, this is not advisable at all. Certain springs in the shutter that power shutter blades and iris blades, for instance the particular one that fails mostly, is the one that closes the blades prior to firing, mearly rests on a tiny nub and is made of #70 wire, Mamiya part #501-2026. If shocked while loaded it WILL slip off it's nub causing the lens not to close down prior to firing. There are a few of these types of hair springs which are vulnerable when in tension.

 

The shutter's main spring, when loaded will be in torsion, if left in torsion long term, will develop memory. When put back into normal operation, it will not have the same driving force it was designed to deliver and thus the shutter speeds will be slower than tolerance will allow for proper operation. To support this, see the many papers published on spring mechanics, design and manufacture.

[q.g._de_bakker]

Well, you have shown that a myth is something repeated again and again. And again. So much so that people take it for "gospel truth", handed down from the ancients, the origins lost in the mists of time.<br><br>Now i can accept that you do not believe what i say. It's fair enough. But (yes, the unavoidable "but") why do you not try to find proof (!) for what you (!) believe to begin with? Good luck trying!<br>;-)

[q.g._de_bakker]

I forgot to give references... Where to begin... Ask any metallurgist, or pick up any metallurgy textbook. Learn about yield point, and what goes on in the realm below that.<br><br>For those who don't want to, in short: Should a sping permanently deform, or show a loss of elasticity, it has been stressed beyond its elastic limit, i.e. it should not have been used for what it is used for to begin with. So assuming the designer of a mechanism had brain enough not to use the wrong springs, springs will not (!) suffer from being under tension.<br>Use it a lot, and it eventually succumb to fatigue. Extra cycles caused by misplaced care about leaving springs stressed will hasten (be it a bit) the end of the spring.<br>So you're actually better of <b>not</b> taking the stress off the springs. Keep the things cocked!<br><br>Mechanisms in a cocked state have the full load of the springs to keep them the way they should be. Knocks will be cushioned by the springs. But remove the tension, and what remains is a collection of movable parts, which given a good knock, will indeed move...<br>That story about the spring in the Mamiya not caring much for being "moved", slipping off when shaken, is rather alarming. If true, what a pathetic, crummy design!!! Unbelievable.

[paul ron]

Sekors and Copals are basically the same so where is the pathetic design? I see you know nothing about these shutters nor the mechanics involved in their timing mechanisms, let alone your pathetic support of some theories you made up just to be contravercial. Please substantiate your references and not tell me to research basic metalergy books since this is where my information is comming from. Point me to some real information? ANYTHING?

[q.g._de_bakker]

paul RON<br><br>Thank you for the kind response.<br>May i suggest that perhaps it is your pigheaded ignorance that is bothering you?<br>Good.<br><br>If the Copals and Sekors are as you describe they are indeed pretty hopeless designs. But perhaps it is your understanding of those that is just that.<br><br>And instead of trying to spell "controversial", maybe you should educate yourself about the things discussed. If you do, you'll see that these "theories" are not controversial at all.<br>But i guess your "knowledge" "about these shutters" will prevent you from doing so. Anecdotal old men building clocks... and confusing (questionable) knowledge about shutter mechanisms for knowledge about materials... riding the high horse, demanding proof, while you do not have one shred of that to back your own position... It's a shame, but there we are.

[paul ron]

Thank you.

[brett_kosmider]

Thanks for the responses. I've heeded previous advice to exercise the lens shutters at

least once a month, which I've done. I may have left the lenses cocked (oops), but you live

and you learn. I do suspect that my 50mm C lens is slow, though I must admit, it was

shipped to me from KEH in the cocked position!

 

I will have to have the shutter speeds timed and see if its still acceptable. Damn. I

suppose the cost of having the shutter repaired/replaced is more than the cost of the lens

used... We'll see, may not be as bad as I think.

 

At any rate, thanks for the advice.

[joseph_e._forks]

If you don't believe Paul, as I do, you can read it right in the Mamiya manual (and they should know).

 

Here is the quote:

"Storage

When not used for a long period of time remove the battery and

film from the camera and keep mirror and shutters in uncocked

state. Avoid storing the camera and lenses in humid or sea air

atmosphere or in extreme hot or cold environment. Periodically

exercise film transport and shutters by making a number of blind

exposures at various shutter speeds and f/stops."

 

Regards

Joe

[harold_levie]

Whether or not a spring stressed below its elastic limit will take a "set" is a complicated question which will no doubt be debated endlessly. But there is another issue that may or may not be relevant: stress corrosion. In some cases, metals stressed below the elastic limit may corrode between the grains, resulting in cracks which would not have occurred in an unstressed condition.

 

Cartridge brass (i.e.--ammunition) is notorious for this if the atmosphere contains ammonia; in a loaded cartridge the bullet is retained largely by tension in the neck, and in the old days the ammonia from horse manure gave cavalrymen problems with cartridge neck cracking. (As the weather warms up in the spring, ammonia from manure increases, leading to the traditional term "season cracking".)

 

I would hope that modern camera springs are made out of alloys that are not susceptible to this problem, but some stainless steels can show stress corrosion from chlorides (found in human perspiration) so it is not altogether impossible. (Anyone know the properties of Nivarox, offhand?)

 

Personally, I'd like to think that a cocked spring would be at risk only under humidity conditions that would destroy the lens anyway, but the phenomenon of stress corrosion could explain why there are such conflicting opinions on the vulnerability of springs in general to being stored under stress.

[brett_kosmider]

Sure! You fork over BIG cash for the RZ and you get an instruction manual with something

useful in it! Ha! Us RB owners got jipped! LOL

[paul ron]

http://www.mamiya.com/customerservice1.asp?id=3&id2=115

 

Go to this site and click on 6x7 where you will find user manuals for the RBs.

[frdchang]

i recall a zeiss article that mentioned to keep our lens cocked (i believe it said that having it cocked made no difference)..(anyways, the way the hasselblad system worked, it ensured that our lens was always cocked when stored).

 

i can't find the article (perhaps it was in my hasselblad manual, or i read it on zeiss.de website).

 

i do not know if this information only applies to the new springs installed in the CFI lens or not...