On Nov 15, 3:23 am, "Tom Gardner" wrote:
wrote in message

... Tom Gardner wrote:
[...]
Thanks to Mitsubishi selling China the technology to make really, really
quiet props, I don't know if it WAS detectable.

I remember reading about Toshiba selling propeller milling machines
to the Soviets back in the '80s. Did Mitsubishi do something similar
with China?

Slater

I think you're right, my bad.


Propeller machining technology is not THAT new.

I remember seeing a Toshiba vertical 5 axis milling machine at
Dominion Engineering in Lachine, Quebec in the mid 1970's. This
machine is/was a monster. The main cross beam was hinged in the
middle with one milling head on each half beam. This permitted the
angle of the milling planes to be adjusted for three, four, five, or
six bladed propellers for simultaneous machining on 2 blades.

This company was in the business designing and building hydraulic
turbines, and machining runner blades for Kaplan turbine runners was
part of improving the production and hydraulic efficiency of these
monster machines.

Fascinating stuff. Nowadays it is no big deal....the Chinese could
easily build one themselves and, I suspect, the operating software you
can get off the internet for a song. HSM types are machining gas
turbine compressor and turbine wheels in their basements!!!!

The time consuming part is the hydraulic model design, testing, and
optimization which has to be done for each different application.
Study of hydraulic similitude (it's been a LONG time!) can minimize
the number of physical experiments/studies required.

IIRC the USA submarine sonar operators were lamenting in the early
1980's that many of the Soviet ships were beginning to sound alike
such that they could no longer be identified uniquely by their
propeller noise, or pump noise in the case of nuclear subs.

Wolfgang