Problems with Rapco dry vacuum pumps.

It would be nice to use a magnetic coupling, but the power
transfer in these pumps is too much. The mag coupling has been around
for years and the vac pump manufacturers would be aware of it. Another
problem with magnets: they'd be close to the magnetic compass, being on
the back of the engine in most cases, and we have enough trouble with
magnetic fields as it is when we go to calibrate compasses.
"abripl"'s solution of an electric drive, especially if it's
away from the engine, is alright as long as he doesn't intend to fly
IFR, unless he has a vacuum-driven turn coordinator. Most TCs are
electric, and with attitude and heading gyros relying on an electrical
source all attitude info would be lost if the electrical system quit,
which they can do at the worst possible times. I haven't yet dealt with
the new glass panels, but would hope that they'd have some backup
power; the ones I see have peanut gyros in the panel as backups.

Dan

"abripl"'s solution of an electric drive, especially if it's
away from the engine, is alright as long as he doesn't intend to fly
IFR, unless he has a vacuum-driven turn coordinator.

Actually it was not a solution for my vaccum pump but I simply went to
an electric horizon - removing the vacuum. I only use the electric
horizon (plus altimeter and speed ind.) as backup. I use Dynon's
EFIS-D10 for my primary flight instruments - and have the necessary IFR
certifications. You can see the panel on bottom of
http://www.abri.com/sq2000/choices.html

Most TCs are electric, and with attitude and heading gyros relying on an
electrical source all attitude info would be lost if the electrical system quit,

Oh that. I have a dual battery system and my EFIS-D10 has its own
internal backup battery to last an hour. The dual batteries have
40amp-hour total capacity and normal flight current is only about 12A.
Read more details at http://www.abri.com/sq2000

MAGNETIC pump drive

From:
Date: 23 Sep 2005 08:31:24 -0700
Local: Fri, Sep 23 2005 8:31 am
Subject: Problems with Rapco dry vacuum pumps.
Dan wrote:
It would be nice to use a magnetic coupling, but the power
transfer in these pumps is too much. The mag coupling has been around
for years and the vac pump manufacturers would be aware of it. Another
problem with magnets: they'd be close to the magnetic compass, being on
the back of the engine in most cases, and we have enough trouble with
magnetic fields as it is when we go to calibrate compasses.

Dan

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
http://www.manufacturingcenter.com/d...ustonemore.asp

The drives are manufactured by MagnaDrive Corp, Seattle, WA. Suited for
motors from 10 to 1000 hp, the company's drives and couplings,
according to Ron Woodard, MagnaDrive president and CEO, "also
eliminate hard starts and much
of the vibration associated with power transfer, allowing M-I/SWACO to
redesign their oil centrifuges with fewer control systems and with a
smaller footprint."
**********************
THEREFORE Dan,
Your torque limit is a design / weight problem, not a technology
limit. (Reggie)
************************************************** *************************************
http://www.sacskyranch.com/rapco.htm

The Edo(or Sigma-Tec) quill-shaft is designed to fail at 100
inch-pounds of torque,
whereas
Airborne drive takes (250 inch-pounds) to snap .

Therefore it's not a lot of torque required, and you would not
need the break away coupling as the magnetic field does that....
(Reggie)
************************************************** ***********************************

As far as the magnet compass problem
Beware of:
Alternators, especially permanate magnetic ones.
Elecrtic gyro instruments.
Too closely placed electric vaccuum pumps
and
Magnetized steel air frame structure.

Reggie

You're right. There would be plenty of torque transfer available for
a vacuum pump. Now someone needs to try it.

Dan