[pure-silver] Re: old rollei over exposing
- From: "Gene Johnson" <genej2@xxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 18 Feb 2005 06:19:30 -0800
I agree with Mr. Knoppow,
Though both of the failed mainsprings I've actually seen were broken as a
result of a crack started from a spot of surface corrosion.
I have seen several synchro-compurs on old Rolleiflex MX's that were just
plain worn out. The first symptom is usually a failure to cock the shutter
when the board is extended outward. The wear on all the cocking mechanism
parts stacks up to the point where there isn't enough travel left to quite
cock the shutter. Generally the shutter would still function if you could
cock it manually, but even then it feels pretty rough while the shutter is
being cocked. Theres a steel toothed ring that bears on the aluminum
housing, and that's one of the main wear points. These shutters are on
either heavily used cameras, or have a lot of dirt in them.
----- Original Message -----
From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, February 17, 2005 11:13 PM
Subject: [pure-silver] Re: old rollei over exposing
>
> ----- Original Message -----
> From: "Richard Urmonas" <rurmonas@xxxxxxxxxx>
> To: <pure-silver@xxxxxxxxxxxxx>
> Sent: Friday, February 18, 2005 7:59 AM
> Subject: [pure-silver] Re: old rollei over exposing
>
>
> > Quoting "Koch, Gerald" <gkoch02@xxxxxxxxxx>:
> >
> >> It
> >> is extremely important not to leave a shutter cocked for
> >> long periods of
> >> time.
> >
> > The manufacturers of the older leaf shutters generally
> > recommend
> > the shutter be left cocked. From a mechanical point of
> > view, the
> > cocked state will result in less chance of the shutter
> > misbehaving
> > (going sticky) as the driving spring is much stronger than
> > the return
> > spring, so there is more force available to 'break free'
> > any sticky parts.
> >
> > Richard
> > --
> > Richard Urmonas
>
>
> Well, I've never seen such a recommendation. If a spring
> is not tensioned beyond its elastic limit it probably
> doesn't matter if its tensioned or not as far as losing
> strength with time.
> Many shutters do work as you describe. When the shutter
> is cocked the restoring spring on the retarder winds the
> retarder to its starting position. This usually brings the
> speed control peg up against the speed cam. When the shutter
> is tripped the retarder is forced over by the full strength
> of the drive spring. If the retarder mechanism is glued
> together sufficiently by old lubricant it might just not
> move enough to allow the shutter to close again. Hard to
> know. I would not leave shutters with booster springs in
> their highest speed position because that puts a lot of
> force on some of the parts and I suspect the booster springs
> may be close their limit.
> Springs wear pretty much because of work hardening due to
> cycling rather than constant tension or compression.
> The Compur shuttes used in Hasselblads and the similar
> shutter used in EVS Rollei cameras was designed to be left
> cocked all the time, they must be in Hassy cameras.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
>
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