Today's Message Index:
----------------------
1. 04:02 AM - Vibration(?) problems (Peter Cowan/Lexy Cameron)
2. 06:00 AM - Vacuum supply for back up gyros (Richard Goode)
3. 06:09 AM - Re: Vacuum supply for back up gyros (Archie)
4. 06:37 AM - Re: Vacuum supply for backup gyros (Gary Casey)
5. 07:10 AM - Re: Vibration(?) problems (AI Nut)
6. 08:25 AM - Re: Re: Vacuum supply for backup gyros (n801bh@netzero.com)
7. 10:16 AM - Re: Re: Vacuum supply for backup gyros (Ed Anderson)
8. 02:11 PM - Need known good mag (Charles Heathco)
Message 1
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| Subject: | Vibration(?) problems |
--> Engines-List message posted by: "Peter Cowan/Lexy Cameron" <cowcam@pipcom.com>
My "proven" Rotax 912 80hp "aircraft" engine has a very annoying
problem. At most rpm's it is fairly smooth but between 3800 to
4000 it feels like it is running very rough. Before I did some
updates to the gear box I described it as knocking it was that
bad. After the updates (overload clutch, new bellvilles etc) it
is just rough. It is not carb synch; it is not ignition. I have
checked the balance of the prop and set the pitch on the 72"
Warp. If I take the prop off and runn the engine it runs pretty
smooth with just a hint of vibration at the 3800 range.
Can anyone suggest what this means and the fix? I will double
check prop pitch and balance and I'd like to try a three blade.
Anyone know how significent the moment of inertia issue is which
PowerFin props say is one of their advantages over Warp?
And Hello ED. I'm watching the progress of a 75hp two rotor about
to be marketed.
Thanks
Peter
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Message 2
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| Subject: | Vacuum supply for back up gyros |
--> Engines-List message posted by: "Richard Goode" <richard.goode@russianaeros.com>
I have a 1914 Rolls-Royce Silver Ghost. Fuel pump is a small air compressor on
the engine pumping out 2 PSI pumping to top of the fuel tank, forcing the fuel
out of the bottom.=20
Prior to (I think) 1910 they had a bleed from the exhaust into the fuel tank to
give this pressure. It certainly worked, and I think the only problem was inconsistency
of the check valve - i.e. if it stuck open you lost air pressure and
therefore fuel. However I do not see how you get a vacuum from this same set
up.
Richard Goode Aerobatics
Rhodds Farm
Lyonshall
Herefordshire
HR5 3LW
United Kingdom
Tel: +44 (0) 1544 340120
Mob: +44 (0) 7768 610389
Fax: +44 (0) 1544 340129
www.russianaeros.com
dangerous content by the http://www.anti84787.com
MailScanner, and is believed to be clean.
Message 3
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| Subject: | Re: Vacuum supply for back up gyros |
--> Engines-List message posted by: "Archie" <archie97@earthlink.net>
Richard,
If you have the ability to read AutoCAD files,
I will send you my drawing of the extraction unit.
Archie
----- Original Message -----
From: "Richard Goode" <richard.goode@russianaeros.com>
Subject: Engines-List: Vacuum supply for back up gyros
> --> Engines-List message posted by: "Richard Goode"
> <richard.goode@russianaeros.com>
>
> I have a 1914 Rolls-Royce Silver Ghost. Fuel pump is a small air
> compressor on the engine pumping out 2 PSI pumping to top of the fuel
> tank, forcing the fuel out of the bottom.
>
> Prior to (I think) 1910 they had a bleed from the exhaust into the fuel
> tank to give this pressure. It certainly worked, and I think the only
> problem was inconsistency of the check valve - i.e. if it stuck open you
> lost air pressure and therefore fuel. However I do not see how you get a
> vacuum from this same set up.
>
>
> Richard Goode Aerobatics
> Rhodds Farm
> Lyonshall
> Herefordshire
> HR5 3LW
> United Kingdom
>
> Tel: +44 (0) 1544 340120
> Mob: +44 (0) 7768 610389
> Fax: +44 (0) 1544 340129
> www.russianaeros.com
>
> dangerous content by the http://www.anti84787.com
> MailScanner, and is believed to be clean.
>
>
>
Message 4
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| Subject: | Re: Vacuum supply for backup gyros |
--> Engines-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<While I do not fly with a turbocharger (yet), I do find your idea
certainly
sounds logical to me. However, I presume this technique would only work
while you are flying with boost? In other words, I can see it working when
the turbo is producing boost to normalize the manifold pressure, but my
question is what happens when you got out of boost such as throttling back
for descent??
Ed Anderson>>
It works just fine at light load. Under that condition it supplies the
instrument with atmospheric air and draws air into the intake manifold.
Under high load the air source is the compressor discharge and the outlet is
atmospheric. It also makes a graceful transition in that the instrument
runs with the inlet slightly above atmospheric and the outlet slightly
below. There was a question about getting moisture in the system and I
agree that the compressor discharge can contain some contaminates such as
trace amounts of oil or moisture. Will the instrument filter block that?
Remains to be seen.
For exhaust-powered systems moisture is a real problem, mostly I think
because the pressure supply is highly pulsating, much more so than the
intake manifold. Installing a "venturi" in the exhaust is probably not a
good idea - partly because the high velocity in the exhaust only occurs
during a high pressure pulse and partly because all things take power and I
wouldn't want to increase the engine back pressure just to get a vacuum
source for my instruments. And it would increase the back pressure - no
free lunch. One can get a "cheap lunch" from the exhaust if the negative
pressure pulse is harnessed, but this requires individual check valves at
each exhaust port. Upstream of the check valves these could be collected in
a reservoir to separate any water as suggested by someone.
Gary Casey
Message 5
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| Subject: | Re: Vibration(?) problems |
--> Engines-List message posted by: AI Nut <ainut@hiwaay.net>
Since the engine sounds smooth without the prop attached, it sounds as
if you're hitting a resonance zone. If strong enough, these can destroy
engine and prop on the ground, and cause you to crash if in flight.
Avoid that rpm range unless you can change the resonance frequency to
something above the engines upper rpm limit or down in the 300-500 rpm
range. That might be difficult in your situation.
Peter Cowan/Lexy Cameron wrote:
>--> Engines-List message posted by: "Peter Cowan/Lexy Cameron" <cowcam@pipcom.com>
>
>My "proven" Rotax 912 80hp "aircraft" engine has a very annoying
>problem. At most rpm's it is fairly smooth but between 3800 to
>4000 it feels like it is running very rough. Before I did some
>updates to the gear box I described it as knocking it was that
>bad. After the updates (overload clutch, new bellvilles etc) it
>is just rough. It is not carb synch; it is not ignition. I have
>checked the balance of the prop and set the pitch on the 72"
>Warp. If I take the prop off and runn the engine it runs pretty
>smooth with just a hint of vibration at the 3800 range.
>Can anyone suggest what this means and the fix? I will double
>check prop pitch and balance and I'd like to try a three blade.
>Anyone know how significent the moment of inertia issue is which
>PowerFin props say is one of their advantages over Warp?
>And Hello ED. I'm watching the progress of a 75hp two rotor about
>to be marketed.
>Thanks
>Peter
>
>
>
>
Message 6
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| Subject: | Re: Vacuum supply for backup gyros |
--> Engines-List message posted by: "n801bh@netzero.com" <n801bh@netzero.com>
For exhaust-powered systems moisture is a real problem, mostly I think
because the pressure supply is highly pulsating, much more so than the
intake manifold. Installing a "venturi" in the exhaust is probably
not a
good idea - partly because the high velocity in the exhaust only occurs
during a high pressure pulse and partly because all things take power and I
wouldn't want to increase the engine back pressure just to get a vacuum
source for my instruments. And it would increase the back pressure - no
free lunch. One can get a "cheap lunch" from the exhaust if the
negative
pressure pulse is harnessed, but this requires individual check valves at
each exhaust port. Upstream of the check valves these could be collected in
a reservoir to separate any water as suggested by someone.
Gary Casey
The exhaust style system is not plumbed into the head pipes, it is welded in the
collectors. That gives you a constant flow of gases passing across the venturi
tube. It is not the kind of venturi you are imagining,it is a 1/2" or so metal
tube about 3" long cut back at an angle. This design is used is 1000's of
race engines. A comparison is, have you ever seen the blow nozzles that attact
to an air hose for washing off things? This thing has two hoses, one connects
to the high pressure air supply and the other one goes in a bucket of detergent,
mineral spirits, etc. Maybe Archie can explain it a little better, or send
ya to a web site that shows pics of it.
ben
Message 7
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| Subject: | Re: Vacuum supply for backup gyros |
--> Engines-List message posted by: "Ed Anderson" <eanderson@carolina.rr.com>
Ok, I understand. Thanks for the explanation, Gary. Neat concept.
Ed
----- Original Message -----
From: "Gary Casey" <glcasey@adelphia.net>
Subject: Engines-List: Re: Vacuum supply for backup gyros
> --> Engines-List message posted by: "Gary Casey" <glcasey@adelphia.net>
>
> <<While I do not fly with a turbocharger (yet), I do find your idea
> certainly
> sounds logical to me. However, I presume this technique would only work
> while you are flying with boost? In other words, I can see it working
when
> the turbo is producing boost to normalize the manifold pressure, but my
> question is what happens when you got out of boost such as throttling back
> for descent??
> Ed Anderson>>
>
> It works just fine at light load. Under that condition it supplies the
> instrument with atmospheric air and draws air into the intake manifold.
> Under high load the air source is the compressor discharge and the outlet
is
> atmospheric. It also makes a graceful transition in that the instrument
> runs with the inlet slightly above atmospheric and the outlet slightly
> below. There was a question about getting moisture in the system and I
> agree that the compressor discharge can contain some contaminates such as
> trace amounts of oil or moisture. Will the instrument filter block that?
> Remains to be seen.
>
> For exhaust-powered systems moisture is a real problem, mostly I think
> because the pressure supply is highly pulsating, much more so than the
> intake manifold. Installing a "venturi" in the exhaust is probably not a
> good idea - partly because the high velocity in the exhaust only occurs
> during a high pressure pulse and partly because all things take power and
I
> wouldn't want to increase the engine back pressure just to get a vacuum
> source for my instruments. And it would increase the back pressure - no
> free lunch. One can get a "cheap lunch" from the exhaust if the negative
> pressure pulse is harnessed, but this requires individual check valves at
> each exhaust port. Upstream of the check valves these could be collected
in
> a reservoir to separate any water as suggested by someone.
>
> Gary Casey
>
>
Message 8
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<rv-list@matronics.com>
| Subject: | Need known good mag |
--> Engines-List message posted by: "Charles Heathco" <cheathco@comcast.net>
I have deceided to go with one mag and one electronic for now on my RV6a, and both
my mags are old and fear they are near end of service. I wonder if anyone
might have a known good mag laying around from an elec conversion they want o
sell. I now have bendix, could convert if have the wiring. my engine is O-320E2A
Charlie heathco, reply to mail
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