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MMD > Archives > May 2004 > 2004.05.19 > 07Prev  Next


Electrification Kit for Rebuilt Player Piano
By Roger Waring

A little while ago I submitted a posting on vacuum control and
promised to report back on my experimental efforts to find a
comprehensive method of preventing excessive wear and tear on the
instrument.  In view of the recent posting on reduction of blower
motor speeds perhaps now is an appropriate time.

Here are my findings:

Here at The Pianola Workshop I get fairly regular enquiries about
putting an electric pump into standard upright pianolas as an
additional option to pedalling.  There is nothing new about this,
of course.  As we all know, many instruments with reproducing actions
were designed to run in this manner and fitted with suction motors as
standard.  Personally, I prefer to pump, but I accept that the owners
of mechanical instruments are entitled to modify them as they see fit
in order to maximise their enjoyment.

My limited experience of installing electrification kits has been
fairly painless, but I feel that the control elements leave something
to be desired.  Specifically, it has been my observation that the motors
generate far more suction than necessary in terms of the needs of he
instrument, but the speed controller features offered do not seem able
to slow the motor down sufficiently to stop it from hammering both the
piano and player actions to the point of excessive wear.

Now this may be fine for a leaky, badly maintained player, but I do not
install motors on such instruments on principle.  If the player action
is shot then in all probability the rest of the piano is in a dire
state as well, and will still perform poorly.

A properly restored and fully airtight stack and valve chest should
require minimal suction to operate well.  I would suggest a figure of
around 10 inches is more than sufficient for the most part, and yet we
have electric motors able to pull around 40 inches being offered as the
solution to our needs.

Certainly, the kits imported from USA that I have seen are far too
strong at the low level of control.  Perhaps this is because the use of
potentiometers reduces voltage rather than frequency and can therefore
only slow the motor down so much.

My aspirations are quite simple: to allow the player to operate at a
level compatible with the needs of the owner, whilst also protecting
the carefully restored piano action from undue wear and a need for
frequent tuning.  I do not wish to make the operation of the player in
any way subordinate or less responsive as a result of electrification.

My main objectives are as follows:

1. Ease of supply of parts - preferably UK made motors and controllers

Delivery from the USA is of necessity, rather time consuming, unless
premium shipping rates are paid.  I have found suppliers for both
components in the UK, on a next day delivery basis.  Both are
convenient to me in central England where I live.

2. Cost of materials - less than $500 for all components

I have assembled a de-luxe kit for just about this figure.  It does
not take into account the time taken to construct the soundproofed
baffle box in which the motor sits, but that element is quite modest.
Considering that the retail cost of the best US model is around $615
-- to which must be added the cost of a 240VAC/110VAC step-down
transformer ($180) -- then this is very encouraging.  There is also
a very real possibility of $100 VAT being applied on the US model upon
its entry to the UK.

3. Total dynamic flexibility in terms of motor speed, from 0% to 100%

This is the crux of the matter -- being able to set a base level of
playing volume that suits the instrument and its owner, from the
boudoir to the concert hall!  But always being able to specify a
maximum, beyond which might result in damage to our ears or to the
piano.

I have found a compact induction motor less than 6 inches long, having
a cowl diameter of similar dimensions.  Its maximum suction capacity
is well in excess of what is needed, but this is of no consequence
provided that its speed can be fully regulated.  It sits in a small
soundproofed box in the well of the piano.

In order to control the speed of this motor I have acquired a
state-of-the-art single phase 240 VAC inverter that is able to be
programmed for many different applications using a keypad and LCD.
The source is an international company, Eurotherm, and I imagine that
equivalent products could be obtained for 110 VAC applications.

Specifically, it controls the motor speed via regulation of Hz
frequency.  Motor speed can be set at a standard running rate, or
adjusted dynamically as a result of independent or combined events,
by defining percentage levels of the maximum speed, also itself
definable in frequency terms.

It has two modes of working: Local and Remote.  Local is completely
manual control -- you press go and it goes, you press faster and it
speeds up, but never faster than the preset maximum defined earlier.
In Remote mode you automatically invoke a preset configuration at
switch-on using all of the variables applicable to the particular
instrument that have been entered during the initial, one-off set-up.

The process of playing, rerolling, and cut-off is then fully automated
once you move the lever to PLAY.  You can switch between both Local and
Remote modes very easily as long as the motor is idle.  It is not
cheap, but it compares well against the step-down transformer needed
for the US model.

I had originally planned to install a transducer inside the reservoir
to provide feedback on suction levels, and to make adjustments
accordingly.  The inverter is easily capable of controlling such a
closed-loop system.  However, I have found this unnecessary as so many
variables can be configured in the set-up to regulate suction to within
safe limits.  Quite frankly, this box of tricks is magic.

4. Choice of preset suction levels to suit a particular instrument's
needs.

The tests that I have carried out show that running the motor at 25 Hz,
and 50% of maximum easily generates 10 inches of suction, more than
adequate to operate a well restored player.  If the instrument were
particularly large, however, then these parameters could be adjusted
accordingly.

5. Switching to a definable suction level for rewind.

Naturally a reroll pneumatic is required to be fitted that senses
end-of-roll via the trackerbar.  If no suitable holes are present in
the trackerbar, then holes 1 and/or 88 may be used as alternatives.
The programmable facilities allow an event (such as the lever moving
to Reroll position) to be sensed via a microswitch and acted upon to
reduce the suction to a pre-determined level.

6. Automatic cut-off at end of roll.

Once again, this can be programmed using parameters and a suitably
placed microswitch, typically mounted at the rear of the spoolbox
to detect the flapping tab at the start of a roll.  However, the
configuration that I have found to be quite successful requires only
one such switch: that to open when the lever is moved away from the
Play position.

The motor can be ramped down to zero speed over any predefined time,
say, 20 seconds, or can even be allowed to coast to zero, gradually
reducing suction during reroll until eventually coming to rest.  In
both cases the roll has been rewound and the motor is idle, awaiting
further work.

7. Control at keyboard level.

A simple RS232 cable connection is available so that the small keypad
with its liquid crystal display can easily be mounted just beneath the
keybed.  The main case of the inverter is then fitted inside the piano
well, alongside the motor.

To make this arrangement easy to install I have fitted detachable
connectors to all cables.  This also facilitates removal if maintenance
is required on any component.  Everything is protected by 5 amp fuses.
The motor draws less than 3 amps.

To enable pedalling without modification a check valve forms the basis
of connection to the suction reservoir.  This automatically seals if
atmosphere is present on the outer side.

I am prepared to take UK orders for the installation of such
electrification from July of this year.  What I offer is a bespoke
solution to enable owners to get the best from their instrument without
compromising its pedigree or value.

I can be contacted via email at <Pianola-Workshop@blueyonder.co.uk>

Roger Waring - The Pianola Workshop
Solihull, United Kingdom
www.pianola.co.uk


(Message sent Wed 19 May 2004, 20:31:35 GMT, from time zone GMT+0100.)

Key Words in Subject:  Electrification, Kit, Piano, Player, Rebuilt

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