PSRU decisions to make

[Mike Davis]

Hey Mike,

My only concern with using engine oil for the PSRU also would be the
introduction of contaminants from one system to the other should either ever
have a problem. Both components are expensive items, I'd just hate to see
both placed at risk even if one itself has preformed flawlessly just because
of some unforseen problem with the other.

Mike

----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Thursday, June 26, 2003 7:54 PM
Subject: PSRU decisions to make

Now that I've ordered my PSRU I thought I could relax and enjoy the fact
that I finally decided on one. (The Firewall Forward CAM 500 helical
gear drive.) Now I have two more decisions to make. Do I have a vacuum
pump drive installed or just go with a belt driven one or even a
venturi? I have the option of using engine oil to cool and lubricate
the gears in the PSRU or I can go with a dry sump system. Apparently,
there is some difference in how it's set up depending on which way to
go. It seems like a dry sump would be better since the only heat
introduced into the oil would be from the PSRU itself. But using engine
oil would be a simpler installation and I wouldn't have to find room for
the PSRU oil sump. I wonder if anyone has any thoughts about that? I'm
inclined to go with a simple venturi which would be in keeping with my
continued "keep it simple" philosophy, and I would not miss a knot or
two in cruise. I've never flown with a venturi for vacuum. Can anybody
fill me in on their performance? Do they work well through the entire
speed range of a Super Rebel? Aircraft Spruce sells a 9"Hg venturi.
Hopefully it will still produce the 4-5"Hg I will need for the gyros
even at low airspeed.

Mike Kimball
SR#044

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[rickhm]

Mike,

I haven't had the time to dig into it, been travelling too much for work. I design medical equipment for a living and subsequently see lots of motors, fluid pumps, vaccuum pumps of all shapes and sizes (3 oz to 40 lb). I was going to attempt to find an electric vaccuum pump that would provide the appropriate flow at 4-5" Hg. Not sure what the flow needs to be, have not had the time to dig into that. My thinking here is that with an auto engine you can generate tons of electrical power. Hence it would be convenient to go the electric vaccuum pump route. I might be nice to hear other's thoughts and if anyone knows the required flow rate?

Rick Muller
SR70

-------Original Message-------
From: Mike Kimball <mkimball@gci.net>
Sent: 06/26/03 09:54 PM
To: murphy-rebel@dcsol.com
Subject: PSRU decisions to make

Now that I've ordered my PSRU I thought I could relax and enjoy the fact

that I finally decided on one. (The Firewall Forward CAM 500 helical
gear drive.) Now I have two more decisions to make. Do I have a vacuum
pump drive installed or just go with a belt driven one or even a
venturi? I have the option of using engine oil to cool and lubricate
the gears in the PSRU or I can go with a dry sump system. Apparently,
there is some difference in how it's set up depending on which way to
go. It seems like a dry sump would be better since the only heat
introduced into the oil would be from the PSRU itself. But using engine
oil would be a simpler installation and I wouldn't have to find room for
the PSRU oil sump. I wonder if anyone has any thoughts about that? I'm
inclined to go with a simple venturi which would be in keeping with my
continued "keep it simple" philosophy, and I would not miss a knot or
two in cruise. I've never flown with a venturi for vacuum. Can anybody
fill me in on their performance? Do they work well through the entire
speed range of a Super Rebel? Aircraft Spruce sells a 9"Hg venturi.
Hopefully it will still produce the 4-5"Hg I will need for the gyros
even at low airspeed.

Mike
Kimball
SR#044



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[Rebflyer]

Well Mike, if you decide on the ventui way, I just happen to have a 12" new
one. E-mail me direct and I'll make you a great deal. Curt N97MR



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[klehman]

Mike

The drive pad can also be used for a B&C direct drive permanent magnet
alternator. That can give you unlimited flying time on an all electric
airplane should you decide to go that route instead of a vacuum pump now
or in the future. I would have liked a drive pad!

I also definately like the separate oil systems with lubricant optimised
for each application. It may not be necessary if the psru has been
designed to use engine oil. The fact that you have a choice says
something though...

Ken

Mike Kimball wrote:

Now that I've ordered my PSRU I thought I could relax and enjoy the fact
that I finally decided on one. (The Firewall Forward CAM 500 helical
gear drive.) Now I have two more decisions to make. Do I have a vacuum
pump drive installed or just go with a belt driven one or even a
venturi? I have the option of using engine oil to cool and lubricate
the gears in the PSRU or I can go with a dry sump system. Apparently,
there is some difference in how it's set up depending on which way to
go. It seems like a dry sump would be better since the only heat
introduced into the oil would be from the PSRU itself. But using engine
oil would be a simpler installation and I wouldn't have to find room for
the PSRU oil sump. I wonder if anyone has any thoughts about that? I'm
inclined to go with a simple venturi which would be in keeping with my
continued "keep it simple" philosophy, and I would not miss a knot or
two in cruise. I've never flown with a venturi for vacuum. Can anybody
fill me in on their performance? Do they work well through the entire
speed range of a Super Rebel? Aircraft Spruce sells a 9"Hg venturi.
Hopefully it will still produce the 4-5"Hg I will need for the gyros
even at low airspeed.

Mike Kimball
SR#044

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[Bob Patterson]

Hi Mike !

I <really> like the "keep it simple" approach !! :-)

Probably best to keep the gear oil separate - I know
it's a pain, but at least you won't lose both engine and PSRU,
if one or the other starts shedding metal ! An oil filter for
the PSRU is also a "Good Thing"(tm) !!! (to collect the larger
bits !) ;-)

As for Venturis - GREAT IDEA !! I hate vacuum pumps
because they steal 3 HP, or so, ALL THE TIME, even when you don't
need the gyros. They are also one of the highest maintenance items
I've seen on aircraft !! Venturis mounted on the side of the
fuselage in the propwash will generate enough vacuum to spin up
the gyros, even on the ground, so there's no big problem with
speed. One often sees a panel mounted restrictor valve to regulate
the vacuum - fairly simple. Depending on how many gyros you are
planning to run, you might need 2 - generally, I recall that
a 4" venturi will run two gyros (DG & Horizon), while a 2" venturi
is only good enough for one small gyro, like a T & B. Personally,
I would go with an electric T & B, they're not to expensive, and
it's good to have 2 different kinds of gyro power - just in case
one dies in cloud ! Electric horizons are too expensive, and,
in any case, the new digital stuff is starting to appear - NO
NEED for ANY vacuum - all solid-state !! If you can hold off
a year or 2, these should become quite competitively priced !
(Heck, there's one built into the Garmin 196 already !! And you
get a GPS as well ! :-) )

One thing to watch, though - gyro instruments come in
2 flavours ! Those for pumps, and those for venturis - neither
will work properly with the wrong air source .... so I've been told.

.....bobp

---------------------------------orig.-----------------------
At 01:54 PM 6/27/03 +1000, you wrote:

Now that I've ordered my PSRU I thought I could relax and enjoy the fact
that I finally decided on one. (The Firewall Forward CAM 500 helical
gear drive.) Now I have two more decisions to make. Do I have a vacuum
pump drive installed or just go with a belt driven one or even a
venturi? I have the option of using engine oil to cool and lubricate
the gears in the PSRU or I can go with a dry sump system. Apparently,
there is some difference in how it's set up depending on which way to
go. It seems like a dry sump would be better since the only heat
introduced into the oil would be from the PSRU itself. But using engine
oil would be a simpler installation and I wouldn't have to find room for
the PSRU oil sump. I wonder if anyone has any thoughts about that? I'm
inclined to go with a simple venturi which would be in keeping with my
continued "keep it simple" philosophy, and I would not miss a knot or
two in cruise. I've never flown with a venturi for vacuum. Can anybody
fill me in on their performance? Do they work well through the entire
speed range of a Super Rebel? Aircraft Spruce sells a 9"Hg venturi.
Hopefully it will still produce the 4-5"Hg I will need for the gyros
even at low airspeed.

Mike Kimball
SR#044



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[Mike Kimball]

Now that I've ordered my PSRU I thought I could relax and enjoy the fact
that I finally decided on one. (The Firewall Forward CAM 500 helical
gear drive.) Now I have two more decisions to make. Do I have a vacuum
pump drive installed or just go with a belt driven one or even a
venturi? I have the option of using engine oil to cool and lubricate
the gears in the PSRU or I can go with a dry sump system. Apparently,
there is some difference in how it's set up depending on which way to
go. It seems like a dry sump would be better since the only heat
introduced into the oil would be from the PSRU itself. But using engine
oil would be a simpler installation and I wouldn't have to find room for
the PSRU oil sump. I wonder if anyone has any thoughts about that? I'm
inclined to go with a simple venturi which would be in keeping with my
continued "keep it simple" philosophy, and I would not miss a knot or
two in cruise. I've never flown with a venturi for vacuum. Can anybody
fill me in on their performance? Do they work well through the entire
speed range of a Super Rebel? Aircraft Spruce sells a 9"Hg venturi.
Hopefully it will still produce the 4-5"Hg I will need for the gyros
even at low airspeed.

Mike Kimball
SR#044



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[storchpilot]

Attn. Mike, you already have had some good input. I agree with Ralph B.
and bobp. IF you still have a choice, seperate oil supply for the PSRU
to avoid cross-contamination. The PSRU being the dirtier item, so to
speak. I still have the engine oil supplying lubrication to the Ross
Aero box, but I do have a filter in the return line. So far, so good.
All electrical is of course preferred, since you have the choice of two
alternators. ( I have two alternators on my Legacy engine, but so far
one is just along for the ride) and I do have an aircraft vacuumpump.
The problem is of course the price of an electrical AH and DG, good
grief. Not a bad compromise for the time being is that new all in
instrument, call it a "poor man's EFIS" , with the extra AOA pitot and
standby battery pack it still is $ 2325. Wait til the last minute and
the price may even come down some. See it at www.dynonavionics.com . I
would not go for venturis, that is really going way back, although
bobp's advice is the one to follow, if you still have to go that route,
get at least two, rather than one large one. Hope this helps, Geert
Frank



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[mike.davis]

I think I saw Mike and family with the camper and boat in tow on the way out
of town yesterday... so I'll add a little more information here that addresses
a few questions that have been raised.

Mike already has his flight instruments in his panel, to include an HSI he
saved from a previous airplane, and a vacuum attitude gyro... so going
electric is ruled out. His turn indicator will be electric because he is
planning to install the Navaid autopilot.

If Bobp is right about the instruments needing to be "for" a venturi, then
Mike may be out of luck there too.

Mike

On 6/28/2003 7:15 PM, MURPHY-REBEL@DCSOL.COM wrote to MIKE DAVIS:

I am curious about that 3 hp. Could there be a missing decimal point
there? I've had two different types of vacuum pump couplings apart and I
can't believe they could possibly transmit anywhere near 3 hp. at 3300
shaft rpm. Maybe 0.3...

I'd guess that a venturi might be even less efficient after allowing for
propellor efficiency etc.

Ken

Bob Patterson wrote:

snip
As for Venturis - GREAT IDEA !! I hate vacuum pumps
because they steal 3 HP, or so, ALL THE TIME, even when you don't
need the gyros.

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[klehman]

I am curious about that 3 hp. Could there be a missing decimal point
there? I've had two different types of vacuum pump couplings apart and I
can't believe they could possibly transmit anywhere near 3 hp. at 3300
shaft rpm. Maybe 0.3...

I'd guess that a venturi might be even less efficient after allowing for
propellor efficiency etc.

Ken

Bob Patterson wrote:

snip
As for Venturis - GREAT IDEA !! I hate vacuum pumps
because they steal 3 HP, or so, ALL THE TIME, even when you don't
need the gyros.

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[Wayne G. O'Shea]

We've been here before Mike with Bob stating there are two vacuum gyro
horizons! Never heard of this (although who knows for sure!!), other than
from Bob P., and I have been running an off the shelf RC Allen A/H and D/G
off of a 9" venturi for 8 years. Same model of instruments that are running
in Bob's C-FXWI off his 215CC vacuum pump. If he wants to get rid of that
pump (that I paid $700+cdn for) I'd be glad to switch it to a venturi for
him and put a plate over his pump drive hole (to give him his "3 horsepower"
back) so I can install it on my C-FOKM amphib for gyro installations!! ))
Remember though that either way you are going to be robbed!! Maybe more like
Ken stated at >POINT< 3 Hp (0.3hp) to run the pump, or 3 MPH from the
venturi drag!

I found I had to remove the vacuum regulator all together on my installation
to pull 4" vacuum at 100MPH. It's enough to keep them very accurate but to
be honest I never set the DG until on track from my GPS readings. I guess if
you ran a good high rpm while holding on the runway you might get them
spinning up enough to set before take off into the unknown. The odd time
from a rough strip though I tumble my A/H because it's not up to speed good
enough and gets bounced around on take off, but I never waste anytime
sitting still on the active.

Before you bother buying a vacuum regulator (if going with the venturi) see
what your guage is telling you in cruise and then see if you really need to
spend the money for one!

Cheers,
Wayne

----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Monday, June 30, 2003 1:31 AM
Subject: Re: PSRU decisions to make

I don't see why a vacuum instrument would care what the source of the

vacuum

is as long as there is enough. I'll look into it, but here's hoping that
there is no such thing as instruments for venturis versus instruments for
pumps. Also, someone mentioned that venturis only work when there's air
flowing through them so they are no good for IFR. I also don't get that.
There will be air flowing through the venturi as soon as the prop is
turning, and even more when the plane starts moving. Bob suggests that

the

prop wash alone is enough to spin up the gyros. I definitely want the
venturi to have spun up the gyros by the time I have rotated on takeoff.

I

don't intend to regularly fly hard IFR but I would like to punch through

the

occasional fog layer or fly an occasional approach to get through the

clouds

that are making if difficult to land at my destination. If a venturi can
handle that, I am definitely going with the simple, maintenance free
venturi.

Mike Kimball
SR#044


----- Original Message -----
From: <mike.davis@dcsol.com>
To: <murphy-rebel@dcsol.com>
Sent: Sunday, June 29, 2003 1:21 PM
Subject: Re: PSRU decisions to make

I think I saw Mike and family with the camper and boat in tow on the way

out

of town yesterday... so I'll add a little more information here that

addresses

a few questions that have been raised.

Mike already has his flight instruments in his panel, to include an HSI

he

saved from a previous airplane, and a vacuum attitude gyro... so going
electric is ruled out. His turn indicator will be electric because he

is

planning to install the Navaid autopilot.

If Bobp is right about the instruments needing to be "for" a venturi,

then

Mike may be out of luck there too.

Mike

On 6/28/2003 7:15 PM, MURPHY-REBEL@DCSOL.COM wrote to MIKE DAVIS:

I am curious about that 3 hp. Could there be a missing decimal point
there? I've had two different types of vacuum pump couplings apart and

I

can't believe they could possibly transmit anywhere near 3 hp. at 3300
shaft rpm. Maybe 0.3...

I'd guess that a venturi might be even less efficient after allowing

for

propellor efficiency etc.

Ken

Bob Patterson wrote:

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[Mike Kimball]

I don't see why a vacuum instrument would care what the source of the vacuum
is as long as there is enough. I'll look into it, but here's hoping that
there is no such thing as instruments for venturis versus instruments for
pumps. Also, someone mentioned that venturis only work when there's air
flowing through them so they are no good for IFR. I also don't get that.
There will be air flowing through the venturi as soon as the prop is
turning, and even more when the plane starts moving. Bob suggests that the
prop wash alone is enough to spin up the gyros. I definitely want the
venturi to have spun up the gyros by the time I have rotated on takeoff. I
don't intend to regularly fly hard IFR but I would like to punch through the
occasional fog layer or fly an occasional approach to get through the clouds
that are making if difficult to land at my destination. If a venturi can
handle that, I am definitely going with the simple, maintenance free
venturi.

Mike Kimball
SR#044


----- Original Message -----
From: <mike.davis@dcsol.com>
To: <murphy-rebel@dcsol.com>
Sent: Sunday, June 29, 2003 1:21 PM
Subject: Re: PSRU decisions to make

I think I saw Mike and family with the camper and boat in tow on the way

out

of town yesterday... so I'll add a little more information here that

addresses

a few questions that have been raised.

Mike already has his flight instruments in his panel, to include an HSI he
saved from a previous airplane, and a vacuum attitude gyro... so going
electric is ruled out. His turn indicator will be electric because he is
planning to install the Navaid autopilot.

If Bobp is right about the instruments needing to be "for" a venturi, then
Mike may be out of luck there too.

Mike

On 6/28/2003 7:15 PM, MURPHY-REBEL@DCSOL.COM wrote to MIKE DAVIS:

I am curious about that 3 hp. Could there be a missing decimal point
there? I've had two different types of vacuum pump couplings apart and I
can't believe they could possibly transmit anywhere near 3 hp. at 3300
shaft rpm. Maybe 0.3...

I'd guess that a venturi might be even less efficient after allowing for
propellor efficiency etc.

Ken

Bob Patterson wrote:

snip
As for Venturis - GREAT IDEA !! I hate vacuum pumps
because they steal 3 HP, or so, ALL THE TIME, even when you don't
need the gyros.

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[Bill Delcambre]

My experience is that the venturi will NOT produce adequate vacuum below
flying speed. For a departure, you'd better be able to depart and remain
VMC until the gyros are up and set, before entering the clouds. Propwash
will make em turn but not up to speed. Also, experience has taught that
vacuum pumps fail at precisely the most inoportune moment. Feel better?

All those neat solid state systems are looking better all the time, aren't
they?


Bill Delcambre
----- Original Message -----
From: "Mike Kimball" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Monday, June 30, 2003 12:31 AM
Subject: Re: PSRU decisions to make


I definitely want the

venturi to have spun up the gyros by the time I have rotated on takeoff.

I

don't intend to regularly fly hard IFR but I would like to punch through

the

occasional fog layer or fly an occasional approach to get through the

clouds

that are making if difficult to land at my destination. If a venturi can
handle that, I am definitely going with the simple, maintenance free
venturi.

Mike Kimball
SR#044


----- Original Message -----
From: <mike.davis@dcsol.com>
To: <murphy-rebel@dcsol.com>
Sent: Sunday, June 29, 2003 1:21 PM
Subject: Re: PSRU decisions to make

I think I saw Mike and family with the camper and boat in tow on the way

out

of town yesterday... so I'll add a little more information here that

addresses

a few questions that have been raised.

Mike already has his flight instruments in his panel, to include an HSI

he

saved from a previous airplane, and a vacuum attitude gyro... so going
electric is ruled out. His turn indicator will be electric because he

is

planning to install the Navaid autopilot.

If Bobp is right about the instruments needing to be "for" a venturi,

then

Mike may be out of luck there too.

Mike

On 6/28/2003 7:15 PM, MURPHY-REBEL@DCSOL.COM wrote to MIKE DAVIS:

I am curious about that 3 hp. Could there be a missing decimal point
there? I've had two different types of vacuum pump couplings apart and

I

can't believe they could possibly transmit anywhere near 3 hp. at 3300
shaft rpm. Maybe 0.3...

I'd guess that a venturi might be even less efficient after allowing

for

propellor efficiency etc.

Ken

Bob Patterson wrote:

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