Der Synchrophaser!

How exactly does a synchrophaser work?

What is it measuring to make its adjustments?

Why does it have to be off for takeoff and landing?

What voodoo is contained therein (and what's the difference between a
mechanical and electronic version)?

TheSmokingGnu

On Apr 6, 12:50 am, TheSmokingGnu
wrote:
How exactly does a synchrophaser work?

An engine or engines are slaved to a master engine, in order to reduce
noise, usually by getting their propeller / turbofan beats to cancel
each other.

What is it measuring to make its adjustments?

Depends on type, but figure a set of position sensors. Super advanced
models also use noise sensors to dynamically adjust phase offsets in
flight.

Why does it have to be off for takeoff and landing?

Depends on model. Some don't. Older ones work by reducing engine
speed rather than boosting it, thus you could get into a downward
spiral, which is dangerous at T/O.

Kev

On Apr 6, 12:50 am, TheSmokingGnu
wrote:
[...] Der Synchrophaser!

Fellow old timers, remember this warning?

Alles Lookenpeepers!

Dies Machine is nicht fur gefingerpoken und mittengraben. Is easy
schnappen der springenwerk, blowenfusen und poppencorken mit
spitzensparken. Is nicht fur gewerken by das dummkopfen. Das
rubbernecken sightseeren keepen Cotten-pickenen hands in das pockets -
relaxen und Watch Das Blinken Lights.

:-)

"Kev" wrote in message
oups.com...
On Apr 6, 12:50 am, TheSmokingGnu
wrote:
[...] Der Synchrophaser!

Fellow old timers, remember this warning?

Alles Lookenpeepers!

Dies Machine is nicht fur gefingerpoken und mittengraben. Is easy
schnappen der springenwerk, blowenfusen und poppencorken mit
spitzensparken. Is nicht fur gewerken by das dummkopfen. Das
rubbernecken sightseeren keepen Cotten-pickenen hands in das pockets -
relaxen und Watch Das Blinken Lights.

:-)


That was nailed to a floor joist above my father's train set in the
basement.

Did you ever see this one?

PARKING VIOLATION
This is not a ticket, but if it were within my power, you would receive two.
Because of your Bull Headed, inconsiderate, feeble attempt at parking, you
have taken enough room for a 20 mule team, 2 elephants, 1 goat and a safari
of pygmies from the African interior. The reason for giving you this is so
that in the future you may think of someone else, other then yourself.
Besides I don't like domineering, egotistical or simple minded drivers and
you probably fit into one of these categories.

I sign off wishing you an early transmission failure (on the expressway at
about 4:30 p.m.). Also may the Fleas of a thousand camels infest your
armpits.

WITH MY COMPLIMENTS

On Thu, 05 Apr 2007 21:50:24 -0700, TheSmokingGnu
wrote:

How exactly does a synchrophaser work?

On a piston-pounder it is changing the propeller blade angle/engine
RPM via the prop governor. Some use a coil on the slave engine to vary
the spring pressure on the flyweight governor, some use a step motor
and a jack screw to change the OAL of the prop control cable to the
slave governor.

Have worked on turbo-prop and turbojet systems that use the same step
motor and jackscrew assy. On the jets, it varies the length of the
"throttle" cable...

What is it measuring to make its adjustments?

Again, on a piston-pounder there is typically a small pick-up coil on
the base of the governors, or in some cases sensing units inline in
the tachometer shafts.

On one set-up that I am familiar with the units on the tach shafts are
aligned with the propellers in a specific relation ship to each other,
I would assume to reduce "drumming" on the fuselage.

Why does it have to be off for takeoff and landing?

It has the potential to reduce the RPM slightly on the slave engine if
the master has an RPM sag.

Again, on the systems I am familiar with, the total "authority" of the
system is only around 100-150 rpm, so it isn't going to reduce it
much.

What voodoo is contained therein (and what's the difference between a
mechanical and electronic version)?

Have no idea, AFAIK all the box is doing is trying to match the
frequency output of the pickup coil on the master engine to the output
of the slave engine by tweaking the blade angle/RPM of the slave
engine.

TC

On Fri, 06 Apr 2007 14:32:17 GMT, wrote:

On Thu, 05 Apr 2007 21:50:24 -0700, TheSmokingGnu
wrote:

How exactly does a synchrophaser work?

On a piston-pounder it is changing the propeller blade angle/engine
RPM via the prop governor. Some use a coil on the slave engine to vary
the spring pressure on the flyweight governor, some use a step motor
and a jack screw to change the OAL of the prop control cable to the
slave governor.

Have worked on turbo-prop and turbojet systems that use the same step
motor and jackscrew assy. On the jets, it varies the length of the
"throttle" cable...

BTW, on the stuff I'm working on now, you can choose between synch'ing
either the fans or the engine cores. The RPM's are adjusted by the
synch box tweaking the slave engine computer electronically.

There are two RPM pickup coils for each source (fan or core). One goes
to the engine computer/synch box, the other drives the needles up by
the driver's seat.

In "normal" engine operation, all the power lever/cable changes is a
variable pot signal to the engine computer.

TC

Steve Foley wrote:

That was nailed to a floor joist above my father's train set in the
basement.

Did you ever see this one?

PARKING VIOLATION
This is not a ticket, but if it were within my power, you would
receive two. Because of your Bull Headed, inconsiderate, feeble
attempt at parking, you have taken enough room for a 20 mule team, 2
elephants, 1 goat and a safari of pygmies from the African interior.
The reason for giving you this is so that in the future you may think
of someone else, other then yourself. Besides I don't like
domineering, egotistical or simple minded drivers and you probably
fit into one of these categories.
I sign off wishing you an early transmission failure (on the
expressway at about 4:30 p.m.). Also may the Fleas of a thousand
camels infest your armpits.

WITH MY COMPLIMENTS

I used to have a book of those I carried in the car, looked just like
traffic tickets, probably back in the 70's!
Loved to put one under some nimrods wiper blade when they parked in two
stalls at once... d:-))

Cheers'n Beers.. [_])
Don

wrote:
On a piston-pounder...
TC

Those poor pistons! Maybe I should open a home for battered examples,
give them a place to rest while they reseat their O-rings, that sort of
thing. :P

Thanks for the info, TC and Kev.

One more question; as I am to understand it then, a lot of synchro
systems simply match the RPMs of the engines to achieve a consistent
harmonic, while more fancy-pantsy models can actually measure and shift
the phases so that they are cancelling (the least harmonic, in other
words). Or will the phases go to least harmonic naturally if the RPMs
are matched?

TheSmokingGnu

"Kev" wrote in message
oups.com...
On Apr 6, 12:50 am, TheSmokingGnu
wrote:
[...] Der Synchrophaser!

Fellow old timers, remember this warning?

Alles Lookenpeepers!

Dies Machine is nicht fur gefingerpoken und mittengraben. Is easy
schnappen der springenwerk, blowenfusen und poppencorken mit
spitzensparken. Is nicht fur gewerken by das dummkopfen. Das
rubbernecken sightseeren keepen Cotten-pickenen hands in das pockets -
relaxen und Watch Das Blinken Lights.

:-)


Probably posted in the window of just about every TV stations' Master
Control in the country.

Jay B

"Jay Beckman" wrote in message
...

"Kev" wrote in message
oups.com...
On Apr 6, 12:50 am, TheSmokingGnu
wrote:
[...] Der Synchrophaser!

Fellow old timers, remember this warning?

Alles Lookenpeepers!

Dies Machine is nicht fur gefingerpoken und mittengraben. Is easy
schnappen der springenwerk, blowenfusen und poppencorken mit
spitzensparken. Is nicht fur gewerken by das dummkopfen. Das
rubbernecken sightseeren keepen Cotten-pickenen hands in das pockets -
relaxen und Watch Das Blinken Lights.

:-)


Probably posted in the window of just about every TV stations' Master
Control in the country.

Jay B


Perhaps. It was very common at radio and tv transmitting sites.

Peter