John Johns's post about the Arielle turbine pump in a Duo-Art piano
was most interesting and intriguing [050130 MMDigest].

Have any MMD members come across the Motor Player Corp's Electora?
An advert in the Player Piano Treasury says the Electora was patented
in the US on 28 October 1919 and was only 7" diameter x 10" high.

Here in the UK many late Duo-Art uprights and some small grands were
fitted from new with a Motora turbine vacuum unit.  These are US made,
110 V, use a dropper resistor(!) or transformer, and seem similar to
the Electora, so may have been manufactured by Motor Player Corp.
I believe the same may be true of the late Welte turbine pump.

Motoras are in cast aluminium cases, the other way up than the Electora,
and about 10" tall x 10" round maximum.  Their UK patent is dated
21 August 1919 and shows a well-developed design in the name of S. S.
Cramer.  Motor Player Corp are not mentioned -- maybe the original
invention was British.

The Motoras we see are almost exactly as shown in the patent drawings,
but the bottom baffle floats on a central spring and they don't have
the adjustable inbleed (No. 101).  They're fairly quiet but even so
Aeolian UK put them snugly in square felt-lined wooden boxes which will
just fit in the pianos.

Pianos sold with Motoras invariably have a sticker in the spool box
warning against overheating through playing more than six rolls in
succession without a break!

The Arielle sounds very interesting; it's obviously quite a lot smaller
than a Motora and, from what John says, nice and quiet.

Turbines (particularly ones with forward curvature blades) are ideal
for players as they're somewhat self-regulating and give very constant
suction characteristics.  Ampico's Dr. Hickman knew this and advised
Motor Player Corp on design.  But they're inherently noisy.

I've done a lot of R&D over the years on modifying vacuum cleaner
turbine pumps to make them quiet enough for reproducing pianos, and
have supplied a number to Player Piano Group members here in the UK.
The smallest I can make them, and virtually silent, is about 10"
diameter x 12" tall.  I usually use 750+ watt units which can produce
80" of water if desired, but run them slower on thyristor regulators
to reduce noise and overheating.  35" is about enough to run a small
late Duo-Art providing the flow is sufficient at that head of suction.

Any pictures, sketches and details of the Electora's, Welte's and
Arielle's construction would be very welcome as they may shed light on
the manufacturer(s) and give some insights into techniques used to cut
noise.  Perhaps they have trailing carbon brushes, or filled commutator
slots, floating baffles or gill-slits rather than holes for the
airflow?

Paddy Handscombe
Wivenhoe, Essex, UK