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Re: To David Soderman: A Little Test

----- Original Message -----
From: "Dave King" <kingphoto@mindspring.com>
To: <scan@leben.com>
Sent: Friday, April 12, 2002 7:55 AM
Subject: Re: To David Soderman: A Little Test

> ----- Original Message -----
> From: "Ernst Dinkla" <E.Dinkla@chello.nl>
> To: <scan@leben.com>
> Sent: Thursday, April 11, 2002 5:40 PM
> Subject: Re: To David Soderman: A Little Test

> > The scan movement can't be done with the gear-teeth and a
> > wheel. The only workable solution possible that includes the
> > teeth of the carriage could be a belt that fits in the gear
> > over a longer stretch and the belt itself driven by friction
> > very fine teeth on the inside. But most likely the carrier is
> > clamped between some wheels and relies on friction movement
> > for the scan movement.
> > If it still has to move the uncoupled gear wheel then that in
> > itself could be a source of vibration.
> >
> > The weight difference between the carriages is considerable,
> > their length varies as well so a rack and pinion kind of
> > with teeth of that size isn't an option. I have seen better
> > solutions on 19 th century canal locks. I'm tempted to open
> > scanner as my plan to make another type of glass carrier
> > be compatible with the scan mechanism in all aspects. Maybe
> > tomorrow.
> >
> > Ernst
> If you do get in there could you also have a look at the
> positions?  Wondering if they're user accessible for the
inevitable day they
> need cleaning.

Taken off the steel cover and resisted my desire to take it
further apart.

First, there is most likely just one mirror that bends the light
from vertical to horizontal and so to the rear of the scanner
where the lens and the CCD are located. Cleaning that mirror and
the lens that must be horizontal at 1/3 from the rear of the
scanner is not a DIY job. There's a cilinder like shaped chamber
made of I guess glassfiber reinforced thermoplastic (looks more
like a Bakelite but I doubt that is true) that holds the lens,
mirror and at the rear end the CCD. Not something to take apart
and put together without the right calibrating tools.

The carrier is inserted in a traction unit that positions the
carrier for scanning etc with the gear teeth at the side of the
carrier. For scanning the whole traction unit glides on two rods
with a traditional 3 point brass bearing setup. That movement is
done with a finely machined screw spindle (don't know the right
English term for it). So far I do not see any flaws in the
mechanical design but maybe one;
I can't see how the carrier is locked in the traction unit. From
above some flat springs keep it down but
if it is only arrested by the gear wheel on any lengthwise
movement and sideway movement then I fear that it is difficult to
keep out all vibrations on all the carrier models with their
different weigths and lengths. Remember that the carrier is
'locked' in two extreme positions in the traction unit when it
scans the first and the last image. The brass bearings are
capable enough to keep the whole unit straight for a long time.
But if a Nikon tealady (KME) did design the clamping of the
carrier in the traction unit then there may be a problem there. A
good vibration meter on the carrier will tell a lot.

I think it must be in the CCD arrangement what causes the banding
but I will take the cover off once more to see how the carrier is
clamped down.


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