Hi All,  This is just a short follow-up to Craig Brougher's posting about
"quiet" vacuum pumps.

Some years ago, I had the opportunity to work on one of the Welte Turbine
Pumps.  It was still working when I got to it but it had started to smell
funny (ozone smell).  As it turns out, it was starting to burn up after
70 years.  I sent the unit to a specialist who found some worn bearings
and dust contamination.  The contamination was attributed to the felt
baffles which had become somewhat clogged over the 70 years.

As I recall, there were at least 7 stages (turbines) and 4 stages of
baffles in the unit (I'm still trying to locate the pictures I took but
I may have given them to the customer so all I still have are the
negatives) and they were made of an aluminum looking alloy.  The whole
unit was light weight as compared to today's pumps but the big difference
was the vacuum output.  This jewel produced 80 inches of water vacuum and
did not load down perceptively when capped (why that is, I have no idea).

I mention all of this because I, too, realize that one of the most
serious drawbacks to pneumatic players and reproducing pianos in general
is pump noise.  Even at best, the pump noise is obvious especially during
rewind.  (So I hope you solenoid folks understand that I do try to play
on a level field.)

Since the customer who owns this particular Welte is still an active
customer, I plan to approach her about removing the pump and doing some
analysis of the system.  It is my hope that I new version can be
manufactured at a competitive price.  Are there any financial backers out
there?

Musically,

John A. Tuttle