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MMD > Archives > February 2000 > 2000.02.25 > 06Prev  Next

Boyd Pistonola Player Action
By Craig Brougher

Just a curious question regarding the power of the Boyd Pistonola
player, and to suggest that playing a piano isn't just a matter of
force at the key but also "impulse," if we did a little simple figuring
we can guess that its note pistons couldn't be any larger than 1/2"
diameter and probably less, since 1/2" is about the spacing of the
piano whippens and you'd need some wall space between pistons.  But
let's say the pistons are 1/2" anyway.

So if the player pumped at an average vacuum pressure of 20" the
maximum force exerted by a piston would be 2.2 oz. with no friction,
losses, or space between them (far less, actually).  What we are
probably looking at then would be about 30-40% less in practice.
That doesn't give this piano much margin, all considered.

On the other hand, a covered pneumatic 5" long and 1.5" wide, under
the same vacuum exerts 5.4 lbs or about 86 oz. and the losses probably
total 10% or less.  That's 40 times more power off the top, and
practically speaking, almost 50 times.  "Over-engineered," to be sure.

The best reason I know of to build a player with lots of extra margin
like most of them have is to build in reliability.  So really, they're
"over-engineered" only if you don't intend to play it longer than 10
years or so.  Once you get a little leaking and a few valves failing to
seat, and feeder cloth starting to perforate, then you understand why
they foresaw the need to give these players margins like this.  That's
where their legendary reliability begins.

The engineering philosophy was always this: Whatever we put into a
piano should have the same MTBF [Mean Time Between Failure] as the
piano itself.  It should not fail before the piano itself begins to

Still, the Pistonola (hilarious name: what did they call them after
changing the design -- Bellonola?  Their top of the line player a
Prima-Bellanola?) could play a piano because of the impulse factor
(a little piece of the total momentum), force times time.  That's
the same thing as mass times velocity.  So if they could get the
velocity high, they didn't need force.

My question however is, what pressure did they operate at?  If the
area of their feeder pistons can be measured and if that piston worked
directly from the top of the pedal without additional leverage, then
the ratio is a simple 1:1 divided by the area difference.  But I
suspect that the treadles are arranged a bit differently than that.
Would it be possible to see a picture of the pumping system?  I think
the key to understanding the method of this player is not in the
pneumatic pistons, but the treadles.

I also wonder, if these players are no longer working and the tubing
is still okay, then what stopped them?  Did they rust?  Are they just
clogged up?  Did the pistons disintegrate?  Are they made from
self-destructing pot metal?  Curiouser and curiouser.

Craig Brougher

 [ I just received a few more photos of the Pistonola from Mr. Evans
 [ which I'll add to the page at MMD Pictures site.  Each treadle
 [ is connected by a leather strap which runs up and over a pulley
 [ to pull up (vertically) on the feeder pump piston.  The feeder
 [ pistons appear to be about 3" diameter, while the graphite action
 [ pistons are exactly 0.5", as you surmised.  The cylinder blocks
 [ containing the action pistons are cast aluminum, rather rare in
 [ 1913.  Boyd later produced traditional player actions of wood and
 [ rubberized cloth; the demise of the Pistonola action was possibly
 [ due to high manufacturing cost.  The Pistonola pianos are quite
 [ rare today.  -- Robbie

(Message sent Fri 25 Feb 2000, 14:02:42 GMT, from time zone GMT-0600.)

Key Words in Subject:  Action, Boyd, Pistonola, Player

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