Hi all,
not long ago Joseph Borker asked for some information on the ETA
cal.2894-2, a module chronograph movement powered by ETA's workhorse
caliber 2892. You may read about how the discussion started out here. As I underastand this caliber the module is ETA "inhouse" (that sounds sort of funny ). I'd be curious though if that's the whole story or if there is something more to learn about that...
Later on some follow up threads developed and I've to admit that I got
a bit confused as some suggested it maybe a Dubois Depraz module (which
I thought and still think it isn't...). You'll find those thread here and here.
So, I really had to "scan" my "trash bin" (the type of trash bin where
all the stuff always goes thinking I might use a part or screw of it
one day... ) for the replaced module I remembered once to have had - and finally I found it.
First, here you find a part of ETA's tech spec sheets, just to have a better idea what we're talking about:
As you may see, no lubrication info and the relative strict
recommendation not to disassemble the module at all. And, as I've
already said in an earlier thread, a close look doesn't whet ones
appetite to go ahead and disassemble it
Here's a "real life" picture of the module, dial side and you may get an idea....
Most of the date bits and canon/hour wheel are missing as those were
used to complete the spare module. An interesting feature of this
module is the date wheel on top of the module activated by a driving
pinion which is geared with a large driving wheel on the base movement
where it replaces the original date wheel (maybe much better
undertsandable looking at the exploded view above).
This specific module was taken from an ETA 2894-A2, which to my
understanding is the versin with two subdials, i.e. without hour
counter at "six". As can be seen, some of the hour counter bits are
present, but the only reason is that those are also responsible for
other chrono functions.
Now, here is the module underside where it's connected to the base movement:
And of course I had to open the "forbidden door" ...the top plate is hold by four (pretty crudely finished) screws.
Besides a broken pivot of center seconds (chrono runner) wheel there was a much bigger surprise ahead....
The most shocking news, it's indeed a column wheel chronograph module....well, sort of
. Maybe "rotating cam" would be more appropriate, but functionally it's
exactly that what is commonly called column wheel. Here's a close up :
And after all, this is a very good example that a widely accepted (and
among wis' much prefered) design solution like the column wheel isn't a
guarantee for superior functionallity - at least the specific examples
I've seen pusher feel was'nt what one would expect form a column wheel
chrono. It almost feels like something is breaking inside, I'd say
almost frightening.... it's surprising those tiny angled push pieces
can stand those forces. A large part most likely is due to the fact
that it's not that easy translating hrizontal in vertical movement,
which is necessary for this design - vertical clutch and chrono brakes.
I'll take it apart a bit further later and hope you all enjoyed at least a little bit
). I'd be curious though if that's the whole story or if there is something more to learn about that...
. Maybe "rotating cam" would be more appropriate, but functionally it's
exactly that what is commonly called column wheel. Here's a close up :