Today's Message Index:
----------------------
1. 04:17 AM - Was Nothing new then now propeller twist (David Joyce)
2. 06:24 AM - Re: Electical System 912S (rampil)
3. 06:27 AM - Re: Nothing new then .......? At least the Jabiru can't boil o (rampil)
4. 09:11 AM - Oil pressure (Fergus Kyle)
5. 10:30 AM - Re: Oil Pressure (Thom Riddle)
6. 11:21 AM - Re: Oil Pressure (Roger Lee)
7. 01:18 PM - Re: Re: Oil Pressure (Noel Loveys)
8. 03:07 PM - Re: Was Nothing new then now propeller twist (R.C.Harrison)
9. 05:09 PM - Re: Re: Oil Pressure (Roger Roy)
10. 05:46 PM - Re: Oil Pressure (Thom Riddle)
11. 06:12 PM - Re: Oil Pressure (Roger Lee)
12. 06:15 PM - Re: Was Nothing new then now propeller twist (Roger Lee)
13. 08:41 PM - Re: Re: Hello out There? (Denise and Rocky Whitman)
14. 08:50 PM - Re: Hello out There? (Roger Lee)
Message 1
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| Subject: | Was Nothing new then now propeller twist |
Bob & Ralf, There is the consideration that the central portion of most
props used on Europas will have a zero or negative angle of attack at speeds
over 100kts, which can't help the cooling!. Most props I have looked at have
a twist (taken as the difference between pitch at the tip and at 1/3
radius) of the order of 12 degrees. This is perfectly suited for a 1600mm
prop doing 2300rpm at about 35 kts, but at 115 kts at 2000 rpm you need
about 27 degrees twist to have every part of the propeller having the same
angle of attack in a uniform air flow through the propeller disc. It's not
likely that the tip will work too well at 27 degrees AOA, and if that is run
at + 5 degrees then the inner bit will be at - 10 degrees!
Props that I have looked at on Spitfires, Red Bull racers, etc &
fast turboprops various all have twists up in the 25 deg range. It is
interesting that the graph of twist needed for a given speed is not a
straight line, but a rounded top curve, rather like the course of a
projectile, so that for 1600mm prop, the figures I calculate are:
Knots: 36 61 100 130 184 246 307 at
2300rpm
Knots 31 54 88 113 164 214 267 at
2000rpm
Degrees 12 17 23 27 30 31 29
Twist needed
If you take the 2/3 radius point as having the ideal AOA then
with a12 deg twist the tip would have a pitch angle of 6 degrees less and
the 1/3 portion of 6 degrees more. That according to my calculations is what
you need at 36 kts, making our current props ideal for the initial
acceleration phase, but at130 kts, the twist is 15 degrees less than ideal.
That is to say that if the 2/3 point is ideally pitched the tip will be 7.5
degrees over ideal (and possibly stalled) and the 1/3 portion 7.5 degrees
under ideal pitch (and close to negative AOA).
On the other hand a prop with say 23 degrees of twist would be
ideal for 100kts but would be only about 5 degrees off perfect twist for 150
kts, and 6 degrees off perfect for60 kts.(with the AOA off-perfect for inner
and outer portions by only half these figures - probably still comfortably
in the working range for positive lift). The initial acceleration would of
course suffer. Going back to the original point we could hope that cooling
would be improved, as well as top speed and cruising fuel consumption.
I should say that these calculations are my own, based on the
angles needed to "screw" your way through a solid medium without slippage,
and are therefore fallible!! I would be interested to hear comments from
anyone with an insight in this area.
Regards, David Joyce, G-XSDJ
----- Original Message -----
From: "R.C.Harrison" <ptag.dev@tiscali.co.uk>
Sent: Tuesday, September 04, 2007 9:10 PM
Subject: RE: RotaxEngines-List: Re: Nothing new then .......? At least the
Jabiru can't boil ove
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| Subject: | Re: ngines-List:Electical System 912S |
RJ,
The capacitor is mandatory. The engine's charging coils put out AC
current which is "rectified" into positive going half sine-like pulses.
The cap is required to convert the AC into semi-smooth DC for all
your instruments, etc. This is standard power supply design.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132870#132870
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| Subject: | Re: Nothing new then .......? At least the Jabiru can't |
boil o
Gee,
If I stop the 912s in my Europa while holding, I can't hold the assigned
altitude. Of course, I don't have the glider wings yet ;-)
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132872#132872
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Thom, et al,
I am presuming you are thinking of excessive oil press when cold,
and coring of the cooler rad. I am out of touch but remember my instructor
insisting on my watching the oil pressure gauge after startup to see the
pressure drop because the thermostat opened the bypass valve to let warm oil
into the rad after several minutes - of course we're talking below zero
starts here.
What are your ideas re: the perils in winter starts - say near the
Great Lakes?
Cheers, Ferg
Message 5
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| Subject: | Re: Oil Pressure |
Fergus,
If I was any nearer the Great Lakes (Lake Erie) I'd be needing scuba gear. The
oil thermostat we installed on our 912UL is open about 10% until the oil temperature
starts rising and then gradually opens up to full open at 180F. Therefore
there is no abrupt rise or fall in oil temp due to quick opening and/or closing.
It never closes completely so there is always at least a little oil flowing
through the oil cooler. There are no perils in winter starts for this reason.
The oil temperature comes up a lot quicker with the thermostat than before
we installed it. It also keeps the oil temperature up to near normal during long
idle power descents, which was not the case before the thermostat installation.
A good investment.
--------
Thom in Buffalo
N221FA Allegro 2000 912UL
N197BG FS1/447
--------------------
"...as inquiry is the road to truth, he that is opposed to inquiry is not
a friend to truth."
Thomas Paine
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132913#132913
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| Subject: | Re: Oil Pressure |
Hi Fergus,
I agree with Thom. These little oil thermostats do not cause any significant drop
in temp when they open fully. I had this thermostat in my last plane and it
worked very well. I have another to put in my Flight Design Ct for this winter,
but the temps here in Tucson need to get below 100F first. LOL
Some thermostats do, but this particular one does not and it keeps the temps up
when idling in cold weather. Some do drop and when I flew my helicopter that
is what I looked for in the warm up is when the coolant temp took a sudden drop
of
10-20F.
--------
Roger Lee
Tucson, Az.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132921#132921
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| Subject: | Re: Oil Pressure |
Thom:
Is that the same oil thermostat sold by Air Wolf for the Rotax engine?
Noel
912 to be installed
> -----Original Message-----
> From: owner-rotaxengines-list-server@matronics.com
> [mailto:owner-rotaxengines-list-server@matronics.com] On
> Behalf Of Thom Riddle
> Sent: Wednesday, September 05, 2007 3:00 PM
> To: rotaxengines-list@matronics.com
> Subject: RotaxEngines-List: Re: Oil Pressure
>
>
> <riddletr@gmail.com>
>
> Fergus,
>
> If I was any nearer the Great Lakes (Lake Erie) I'd be
> needing scuba gear. The oil thermostat we installed on our
> 912UL is open about 10% until the oil temperature starts
> rising and then gradually opens up to full open at 180F.
> Therefore there is no abrupt rise or fall in oil temp due to
> quick opening and/or closing. It never closes completely so
> there is always at least a little oil flowing through the oil
> cooler. There are no perils in winter starts for this reason.
> The oil temperature comes up a lot quicker with the
> thermostat than before we installed it. It also keeps the oil
> temperature up to near normal during long idle power
> descents, which was not the case before the thermostat
> installation. A good investment.
>
> --------
> Thom in Buffalo
> N221FA Allegro 2000 912UL
> N197BG FS1/447
> --------------------
> "...as inquiry is the road to truth, he that is opposed
> to inquiry is not a friend to truth."
> Thomas Paine
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=132913#132913
>
>
>
>
>
>
>
>
>
>
>
Message 8
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| Subject: | Was Nothing new then now propeller twist |
Hi! David.
My hope for ground running is that the PFA will relax their 20 minute
requirement.....I managed 5 minutes taxi to the club house and it wasn't
safe to take off so I had to cool off prior to a expedited take off.
Accepting numerous suggestions that it will run cooler after say 50
hours all I have left to do is try to find an optimum ground running
condition.
The choke idea didn't cut much ice today !
When flying there's no problems with temps, coolant or oil.
With your edict below I'm wondering where I am now sitting with the
Woodcomp 3000SL (or whatever it is !) apart from taking over where
William had got to if you get my meaning?
Regards
Bob H G-PTAG
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of David
Joyce
Sent: 05 September 2007 12:17
Subject: RotaxEngines-List: Was Nothing new then now propeller twist
<davidjoyce@doctors.org.uk>
Bob & Ralf, There is the consideration that the central portion of most
props used on Europas will have a zero or negative angle of attack at
speeds
over 100kts, which can't help the cooling!. Most props I have looked at
have
a twist (taken as the difference between pitch at the tip and at 1/3
radius) of the order of 12 degrees. This is perfectly suited for a
1600mm
prop doing 2300rpm at about 35 kts, but at 115 kts at 2000 rpm you need
about 27 degrees twist to have every part of the propeller having the
same
angle of attack in a uniform air flow through the propeller disc. It's
not
likely that the tip will work too well at 27 degrees AOA, and if that is
run
at + 5 degrees then the inner bit will be at - 10 degrees!
Props that I have looked at on Spitfires, Red Bull racers, etc
&
fast turboprops various all have twists up in the 25 deg range. It is
interesting that the graph of twist needed for a given speed is not a
straight line, but a rounded top curve, rather like the course of a
projectile, so that for 1600mm prop, the figures I calculate are:
Knots: 36 61 100 130 184 246 307
at
2300rpm
Knots 31 54 88 113 164 214 267
at
2000rpm
Degrees 12 17 23 27 30 31 29
Twist needed
If you take the 2/3 radius point as having the ideal AOA then
with a12 deg twist the tip would have a pitch angle of 6 degrees less
and
the 1/3 portion of 6 degrees more. That according to my calculations is
what
you need at 36 kts, making our current props ideal for the initial
acceleration phase, but at130 kts, the twist is 15 degrees less than
ideal.
That is to say that if the 2/3 point is ideally pitched the tip will be
7.5
degrees over ideal (and possibly stalled) and the 1/3 portion 7.5
degrees
under ideal pitch (and close to negative AOA).
On the other hand a prop with say 23 degrees of twist would
be
ideal for 100kts but would be only about 5 degrees off perfect twist for
150
kts, and 6 degrees off perfect for60 kts.(with the AOA off-perfect for
inner
and outer portions by only half these figures - probably still
comfortably
in the working range for positive lift). The initial acceleration would
of
course suffer. Going back to the original point we could hope that
cooling
would be improved, as well as top speed and cruising fuel consumption.
I should say that these calculations are my own, based on the
angles needed to "screw" your way through a solid medium without
slippage,
and are therefore fallible!! I would be interested to hear comments from
anyone with an insight in this area.
Regards, David Joyce, G-XSDJ
----- Original Message -----
From: "R.C.Harrison" <ptag.dev@tiscali.co.uk>
Sent: Tuesday, September 04, 2007 9:10 PM
Subject: RE: RotaxEngines-List: Re: Nothing new then .......? At least
the
Jabiru can't boil ove
Message 9
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| Subject: | Re: Oil Pressure |
Thom, Buffalo does get cold but here in Boston cold as well but not as
cold. The thermostat that you have installed would that be the one
listed in the Lockwood catalog? I'm thinking of doing an installation of
a thermostat, any recommendation?
RJ
----- Original Message -----
From: Thom Riddle<mailto:riddletr@gmail.com>
To:
rotaxengines-list@matronics.com<mailto:rotaxengines-list@matronics.com>
Sent: Wednesday, September 05, 2007 1:29 PM
Subject: RotaxEngines-List: Re: Oil Pressure
<riddletr@gmail.com<mailto:riddletr@gmail.com>>
Fergus,
If I was any nearer the Great Lakes (Lake Erie) I'd be needing scuba
gear. The oil thermostat we installed on our 912UL is open about 10%
until the oil temperature starts rising and then gradually opens up to
full open at 180F. Therefore there is no abrupt rise or fall in oil temp
due to quick opening and/or closing. It never closes completely so there
is always at least a little oil flowing through the oil cooler. There
are no perils in winter starts for this reason. The oil temperature
comes up a lot quicker with the thermostat than before we installed it.
It also keeps the oil temperature up to near normal during long idle
power descents, which was not the case before the thermostat
installation. A good investment.
--------
Thom in Buffalo
N221FA Allegro 2000 912UL
N197BG FS1/447
--------------------
"...as inquiry is the road to truth, he that is opposed to
inquiry is not a friend to truth."
Thomas Paine
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132913#132913<http://forums
matronics.com/viewtopic.php?p=132913#132913>
http://www.matronics.com/Navigator?RotaxEngines-List<http://www.matronics
com/Navigator?RotaxEngines-List>
Message 10
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| Subject: | Re: Oil Pressure |
The oil thermostat I bought from summit racing
http://tinyurl.com/3bunxb
is made by Permacool.
http://tinyurl.com/3yrt5d
When you see the price from Summit Racing, you'll know why I bought it from them
rather than any of the aviation sources.
--------
Thom in Buffalo
N221FA Allegro 2000 912UL
N197BG FS1/447
--------------------
"...as inquiry is the road to truth, he that is opposed to inquiry is not
a friend to truth."
Thomas Paine
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132990#132990
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| Subject: | Re: Oil Pressure |
Hi Thom and RJ,
They are the same thermostat made by Permacool. I did happen to buy mine at CPS.
--------
Roger Lee
Tucson, Az.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132993#132993
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| Subject: | Re: Was Nothing new then now propeller twist |
Hi Bob,
So changing the throttle setting a little higher or lower did not help you?
--------
Roger Lee
Tucson, Az.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=132994#132994
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| Subject: | Re: Hello out There? |
Hi y'all,
Well, after 3000+ miles for the sign off break-in, I would say that a
flawless flight from
Texas to Idaho and back puts my 912S somewhere in my soul now. I've had
enough
$16,000 lycoming annuals. I've finally gotten myself back into something
in aviation
that makes sense and makes me smile. My Kitfox with a 912S purring on the
front,
twisting thru Moab Ut... Yeah, I had a good week.
Denise and Rocky Whitman
Kitfox 7, 4 years 912S
Comp.June,07
----- Original Message -----
From: "Roger Lee" <ssadiver1@yahoo.com>
Sent: Thursday, August 30, 2007 6:25 PM
Subject: RotaxEngines-List: Re: Hello out There?
>
> Hi Guys,
>
> I agree the good news as always is that the Rotax 912 just keeps on
> ticking, like a Timex, but we all need to consider the feeding and care to
> keep it happy for 10-15 years. If you could do something now for $25
> wouldn't that be better than $800 or more later.
> The idea of the first post was just to stimulate thought and for people to
> think about the future and maint. of their great engine, nothing more.
> Maybe to get more people involved in their own maint. of the engine.
> I have had a couple of 912's and think they are a great engine.
> Just want to help people keep their investment in good healthy shape.
>
> P.S.
> I'm not a Jabiru fan.
>
> --------
> Roger Lee
> Tucson, Az.
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=131939#131939
>
>
>
Message 14
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| Subject: | Re: Hello out There? |
Hi Rocky and Denise,
I glad to hear and see people are out enjoying life and flying both. You will like
the 912 for many years to come.
I'm also happy to see that all of us are sharing ideas, education and issues here
on the forum. I think it makes everyones life easier and more fun.
We don't have to share problems we can share our fun and trips, too.
--------
Roger Lee
Tucson, Az.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=133027#133027
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