Yashica Mat 124G: To Cock or Not to Cock

Discussion in 'Medium Format' started by ben_nauber, Nov 11, 2009.

  1. I was told once that I should never leave my shutter cocked for an extended period of time. Doing so wears out whatever mechanisms are used to cock and fire and hence blows out your shutter. Is this true? If so, do you folks with Yashica Mat 124Gs and other like cameras wind and backwind immediately before your shot? Also, is it still bad if I only wind and not backwind? Or is all winding off-limits, so to speak? Any help would be greatly appreciated. Thanks!
     
  2. Ah, and lastly... how much time is okay between winding and firing? Is like, 10 minutes okay?
     
  3. I just wind on and cock it to be ready for the next shot. I doubt if even leaving it cocked for months will seriously "set" the spring.
     
  4. The answer is I think that it is better to relieve loaded springs than not in most circumstances of mechanical assemblies. But, that's only my gut surmise as having worked so far for 36 years as a mechanical/electrical engineer. I once wrote Mamiya and asked the same question ... see the below paste of their response. Their response is the bold text. The only other guy to ask might be some super qualified repair person who has seen it all, per se. The expert on the web for Yashicas is without question Mr Joe. M Wolff, yashica_guy@yahoo.com one of the most gracious guys I've ever emailed back and forth with.
    Hello,
    Thank you for your interest in Mamiya. See answers below.

    Thanks,
    Garry Montalbano
    The MAC Group
    8 Westchester Plaza
    Elmsford N.Y. 10523
    Tel: 914.347-3300
    From:
    Jim Momary [mailto:momary@xxxxxxxxx.com]
    Sent: Thursday, December 20, 2007 7:44 AM
    To: info mamiya
    Subject: technical question - storage of RB systems
    Greetings & Happy Holidays -
    I have acquired a couple of RB67 Pro S bodies and 4 of the C type lenses.
    I understand all that I need in using the cameras from an operational viewpoint.
    My question is/are -
    Obviously the camera and shutter need to be cocked prior to removing or re-attaching a lens. When a camera will be stored for a while, i.e weeks, months, etc ...
    1. Is it better to fire the shutter or leave it cocked? The internet is full of opinions that claim one or the other or neither. (Most of my previous work was with Nikons and they always recommended relieving all spring force whenever possible) Firing the shutter as you mentioned relieves the springs.
    2. On lenses that are stored not mounted on the camera, is it better to relieve the cocking or leave the lens cocked? Fire (uncock) the lens also.
    My use is as a busy amateur, not a pro so the number of cycles the cameras go through is not a busy day at a studio.
    Anecdotal info - The cameras are in great shape, they do not appear to have been used much at all. Speeds are perfect as is the operational interface. The ability to have a PD type prism viewfinder along with a waistlevel makes for a universal system. I would like to comment on the good job Mamiya did then & now.
    Thank you for any response and help that you provide,
    Jim Momary
     
  5. thank you kindly, that was very helpful !
     
  6. paul ron

    paul ron NYC

    Thanks for posting real facts from the horses mouth.
    THis same question comes up almost every year. And for years I have been telling everyone the same thing... unload springs when storing cameras for extended periods of time. I have been blasted over n over by know it alls that just simply insist on spreading nonsence. Just do a search.
    As for cocking your Yashicamat, or any camera, after taking a shot... it leaves your camera in a vulnerable situation where you can miss fire while handeling it, just wasting film on shots of the sky n ground. Why not get into the habbit of cocking before each shot?
     
  7. Find a metallurgist, and ask about fatigue and strain.
    Strain (of the magnitude found in these springs) does very little, if anything at all, to metal. Releasing tension and retensioning does.
    Leaving a spring under tension does very little. Firing the shutter needlessly, retensioning when you need it again does.
     
  8. [Double post deleted]
     
  9. Metallurgy aside, it's still spring force that's the design factor.
    Assume one has a small diameter spring, let's say 5 thousands of an inch in diameter.
    The recognized yield strength for decent spring steel is 1100 MPa.
    The yield strength is that point at which the spring will take a permanent set, i.e. the spring deforms plastically, no longer elastically.
    So, what is the force it takes to permanently deform a 5 thousandths diameter spring steel wire?
    Well that works out to 3.15 pounds of force.
    Is it possible to develop 3.15 pounds of force in a lens or shutter assembly ...? Heck, I dunno, I didn't design the darn thing. I do not even know the diameter of the various springs. My assumption of the diameter, is just that, an assumption. I measured 6 ballpoint pens, the clicky variety and their springs were typically 0.008 to 0.010" in diameter. So, 0.005" for a camera spring of sorts, seemed to be plausible. Obviously bigger components will have larger diameters and hence 'stronger' springs. (For the inquisitive a 10 thousandths diameter (0.010") spring would permanently deform at a loading of 12.7 pounds. )
    One might ask if we keep a 0.005" spring steel fiber stressed at 2 pounds of loading for 3 months, will there be creep in the metal so that a minor amount of permanent deflection occurs? I do not know as it depends on a bunch of factors.
    I'm already in over my head, so time for coffee.
    Jim
     
  10. Hasselblad says to always leave their lens cocked. I have always stored all of mine cocked, never had a problem.
     
  11. It differs by camera. Some mechanisms (like the Rollei 35) are designed to be stored cocked, others are not. So while the Mamiya reply above was helpful, it really only applies to the camera the poster asked them about.
     
  12. Nice compromise answer, Janne. ;-)
    But it's not the answer. The question really is whether the stuff cameras are made of does wear more from extra cycling, or from strain.
     
  13. Winding the lever forward advances the film and winding it back finishes up cocking the shutter. You have to do both.
     
  14. It is the forces of rapid decompression followed by the abrupt stop at the end of its travel that kills springs and to a lesser extend the force of cocking it, not leaving them cocked.
     
  15. Despite the response about firing the shutters on dismounted RB67 lenses coming direct from Mamiya, I would say that they should stay cocked.
    The shutters in the RB67 lenses need to be cocked to mount or dismount them so my assumption would be that they are designed to stay in this state for extended periods. Mine certainly do.
     
  16. Whether cocked or not, my RBs willl probably outlive me. Also, let's not forget the advice to cock ... in Mamiya is it so that folks don't wreck the lens taking it on and off improperly. Instructions, rules and legends follow the KISS principle. Keeping a camera cocked also means an instant shot when you pick it up. So, for us erratic humanoids it is one less thing to remember to do.
    It's also more than just springs. Those springs apply pressure to shafts that sit in bearings or journals. The locked up force of a small spring will eventually cause the shaft and its line contact in the journal to displace lubricant. The initial turn then will be with less than optimal lubricant dispersal. Does this matter? Heck, who knows for certain.
    If the spring is run at below its limit, compressing and releasing it should have no deleterious effect. Other pivots and stops do take a beating under usage. In the final analysis, all things do wear out (entropy, sort of). I sure as heck don't obsess over it, I just have habits (dumb hunches mostly) and had asked Mamiya what they thought. So, is it company line, BS or a guess ...? And it's Mamiya-centric.
    And the Evil-Jim also figures that somebody wants to sell me a new camera or repair services, so is the advice really free of taint that might suit the company's bottom line? I worrry more about making a good photo than I do if I left a camera cocked..... now, long term storage and batteries ... in or out?
    :eek:)
    Jim
     
  17. Ben, I've used my Yashicamat 124G indifferently over the years, and had no problems with it. I would not worry about winding.
     
  18. Heh, not to forget all the stuff that can stick to your mirror and other parts when left cocked (old SLR). One would have to break down a specific camera and observe the mechanisms at work.
    Only then could we assume something that neither of us did, right?
    All in all I would say it is VERY camera dependant. RB67,Bronica SQ definitely cocked, Mamiya 645 (Pro), Pentacon, Flexaret, and I think Yashica 124 uncocked.
    If possible, or applicable, not winding the film. From my experience it can slacken quite fast and even get you very unpleasantly blurred pictures when the film comes off even by a little bit. Especially the bigger formats, like RB67. Once a one-click slack ruined my 3 shots. :)
    But I'm not sure how the Y124 works and did not dissassemble it (don't mess with it when it's working)
    That's for my little bit of brain...
     

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