Greetings MMDers,  Just a few suggestions from someone who started
a Duo-Art Vorsetzer, never finished it and then got a Welte built,
but never entirely finished, by Jim Miller.

I finished up what had not been done and rebuilt the rest, as it had
been stored in a hot garage for several years and every bit of cloth
was crisp.  It now plays beautifully.  Many of the details of the
mechanism are not what you would stumble upon in your first attempt,
nor are they the final solution as Jim is always improving his designs
and this one is 20 years old or more.  If someone is interested in
learning from the design, I can take some pictures of the way various
problems were solved.

This Vorsetzer is now quite advanced as I have added many refinements,
such as adjustable bleeds on all of the control valves and stack valves
as well as laser cut phenolic valves guides to enable it to survive
rough shipping.  It made it to the MBSI convention and back by air --
California, Chicago, California, including dirt roads -- with no damage
and just needing a bit of regulation.

The Vorsetzer also has a MIDI valve system installed so it can play
from the computer and several pump options for home as well as (some
day) concert playing.  The pneumatics for the pedals are capable of
operating the sustain and una corda pedals of a grand piano in good
shape but it must be considered that the una corda is not a good way
to soften a grand piano that is running the Duo-Art system.  The soft
pedal was tremendously over used as a coding device and could cause
damage to the piano.  Duo-Art grands used a hammer rail lift (with a
few possibly non-original exceptions) and this would be best fitted to
the piano if it is to play Duo-Art rolls.  The Welte soft pedal is used
less and operates more slowly so it is not as bad for the piano.

Things that I learned from not finishing my first Vorsetzer include,
but are not limited to, the following:

The time "saved" by using a grand stack will be more than made up for
by the time spend adapting everything else to fit.  With an Ampico
stack, you have a chance but with a Duo-Art stack fitted to the grand
you will have to remake the guide rail and tilt the pneumatics all over
the place to fill in the gaps and probably still not fit it to the
keyboard at all.  Using an additional deck might give more flexibility
but will make the monster even bigger and good luck with the plumbing.

A custom stack is really the way to do it.  It will be less work in
the long run and much better.  It is really just some repetitive hole
drilling that is needed to make the deck boards.  A good wood shop
should be able to do the machining although it would be best done by
an experienced stack builder, of course.  The rest of the parts can
be used from the original system although it might be quite a squeeze
fitting in the pump.

Another problem with the Duo-Art is the interdependencies of the
system.  Once you are done with the Vorsetzer you will probably find
that it plays horribly and you will spend an equal or greater time
changing everything around trying to get it right.  It might be a fun
waste of time if you like this sort of project but I would leave a
Duo-Art Vorsetzer to someone with experience if you want something that
you can stand listening to and do not have a lifetime to dedicate to
the project.

If you need to build a Vorsetzer, consider building a Welte.  The
system is much better regulated and can handle variations in components
that would drive you nuts with a Duo-Art.  If you make some less than
optimal decisions about valve or pneumatic configurations you will
still probably get it to play well enough.  Not likely with a Duo-Art.

If you do build a Vorsetzer, look at a lot of them first and consider
why things were done the way they were and how you are going to
regulate the thing without spending hours each time the piano is
changed.  My Vorsetzer is pretty easy to regulate in several ways but
there is definitely room for improvement.  If I were to build another
one, I would definitely do it differently.

Fortunately I realized pretty early on that the Duo-Art Vorsetzer would
not work out without a huge effort and abandoned that project.  It is
enough work to get an original Duo-Art to play superbly and who needs
another one that doesn't?

Best regards,
Spencer Chase
Garberville, CA 95542
http://www.spencerserolls.com/