Today's Message Index:
----------------------
1. 02:02 AM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (Gilles Thesee)
2. 07:03 AM - Re: Why exactly shouldn't you run a 914 without a prop? (AmphibFlyer)
3. 07:11 AM - Re: 914 Fuel Flow (AmphibFlyer)
4. 07:16 AM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (Gilles Thesee)
5. 08:13 AM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (Dave G)
6. 10:00 AM - 912s motor mount question (Dan Billingsley)
7. 11:33 AM - Re: 912s motor mount question (Robert Borger)
8. 03:18 PM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (Gilles Thesee)
9. 05:33 PM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (rparigor@suffolk.lib.ny.us)
10. 06:42 PM - Brake and Billet Pump updates (Robert Borger)
Message 1
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
Hi Ron,
> Now with the 91X engines you have a crankshaft, that twice per revolution gets
hit with the torque blow of two connecting rods trying to accelerate the crankshaft.
BTW this could be another discussion but connecting rods are more rotational
weight than reciprocating, in other words they too act for most part act
like a flywheel, not reciprocating weight like pistons moving up and down.
Not sure I got everything, but one point often neglected is torsional
*vibration *. It's what takes most of the engineering time when
designing and testing a new engine.
My point was, there is more to engines than just *weights* etc. A
crankshaft responds to torque variations by winding and unwinding in its
own very complex ways, and it takes many many test and engineering hours
to get things sorted at the targeted RPM an loads. Motorcycle engines
have massive crank throws/wheels to add to the flywheel effect. TheRotax
crank is much lighter.
Tempering with such a carefully balanced system is something one should
endeavour with utmost care and knowledge if long term (unfortunately
sometimes short term ;-) reliability is to be maintained.
> BTW if you really want to challenge the gearbox of a 914, after you just sinked
the carbs forget to connect the cross tube connecting the starboard to port
bank manifold.
Not willing to try this on one of the engines I'm operating ;-)
Best regards,
--
Gilles
http://contrails.free.fr
Message 2
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| Subject: | Re: Why exactly shouldn't you run a 914 without a prop? |
Gilles.Thesee(at)ac-greno wrote:
>
> > The engine has a flywheel; that is clear if you look at the Illustrated Parts
Manual, which is available online.
> >
> >
>
> The part you are referring to is the magneto/alternator rotor...
>
Giles, the link you supplied didn't work for me, but we're probably thinking of the same part. It's also used for the starter motor drive. Here's the most recent Parts Manual and the others: http://www.rotax-owner.com/index.php?option=com_content&view=article&id=108&Itemid=169
I don't know the weight or mass of the rotating parts attached to the crankshaft--probably
not a lot, even including the freewheel gear and the sprag clutch
housing (912/914 Illustrated Parts Manual, page 6-2)--but I watched Russ's 914
run without a prop and started it, worked the throttle, and shut it down myself,
several times. I was a bit surprised by how smoothly it ran--just as you can
see in Russ's video. As far as I could tell, the engine wasn't banging itself
to death or anything like that. I tried unbalancing the carbs slightly by manually
opening one throttle at a time, but all that did was cause it to lope
a bit.
The only noticeable difference was that the propless engine would accelerate very
quickly because there was almost no mass to accelerate.
=Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=294647#294647
Message 3
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| Subject: | Re: 914 Fuel Flow |
h&jeuropa wrote:
> ...We have a 914 with intercooler and Airmaster constant speed prop in our Europa.
When using 75% power per section 10.1.1.1 (5000 rpm 31 in Hg) we see fuel
flow of 7.5 gph... If we throttle back to 5000 rpm, 29 in Hg, fuel flow drops
to 6 gph... What fuel flow do others see? What power settings do others use?
...Jim & Heather
Jim & Heather, I generally cruise at about 4800 to 5000 rpm and 29 or 30 inches
in my relatively draggy SeaRey. I plan for 5 gph and have never exceeded that
amount in almost 900 hours. It burns a lot more during takeoff, but I've never
tried to measure the consumption then--don't have a fuel flow meter installed.
=Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=294648#294648
Message 4
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
Don,
>
> Giles, the link you supplied didn't work for me,
It seems to be working for me, try to copy and paste in your browser.
http://contrails.free.fr/elec_ducati.php
> but we're probably thinking of the same part. It's also used for the starter
motor drive.
>
Ah, then it must be the freewheel gear, a very thin gear with 50 teeth
and large lightening holes.
> I was a bit surprised by how smoothly it ran
>
The problem is, one cannot judge torsional vibrations just by eye or
ear, otherwise aero engineers would not resort to sophisticated sensors
and analysers, and their life would be easier.
Here are a few links which could be of interest to people with a
mechanical mind (no maths) :
http://www.enginehistory.org/NoShortDays/TV.pdf
http://www.epi-eng.com/propeller_reduction_technology/torsional_vibration_issues.htm
http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm
Best regards,
--
Gilles
http://contrails.free.fr
Message 5
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
Very interesting stuff, perhaps a bit weight in the case of EPI who are
selling a product and obviously would be making a case for the need.
However in the case where they show the extreme torque spikes they have
a prop on which increases the spike and the charts all are full throttle
applications which do the same. These large torsion loads and vibrations
may very well not present themselves in the case of a smooth idle at
virtually closed throttle, in fact it seems likely to me that they would
not.
Just to be clear, (and again I will never demand proof or challenge your
opinion) is it your feeling that running in the state people are
discussing here WILL cause harm, or merely a caution that harm MAY result.
A note of caution is always a good thing but my feeling is that
exercising caution does not always mean that we must not do something at
all. In the simplest case crossing the street requires caution, but the
solution would not be to stay home.
On 18/04/2010 11:16 AM, Gilles Thesee wrote:
> -The problem is, one cannot judge torsional vibrations just by eye or
> ear, otherwise aero engineers would not resort to sophisticated
> sensors and analysers, and their life would be easier.
> Here are a few links which could be of interest to people with a
> mechanical mind (no maths) :
> http://www.enginehistory.org/NoShortDays/TV.pdf
> http://www.epi-eng.com/propeller_reduction_technology/torsional_vibration_issues.htm
>
> http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm
>
>
> Best regards,
Message 6
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| Subject: | 912s motor mount question |
Thought I'd try for an answer here...
I am installing a 912s on my Kitfox IV. I have placed the 4 braces on the top and
bottom of the engine. The intake manifold is off as is the starter. I am still
having a fight with the water pump being in the way. Has anyone dealt with
this b-4 and did you have to take the water pump off? I sure hate breaking that
seal. Wondering if I'm just not holding my mouth right :>)
thanks in advance,
Dan B / Mesa, AZ
Message 7
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| Subject: | Re: 912s motor mount question |
Dan,
I don't know how much this will help you with a 912S & Kitfox IV, but you are welcome to look the the engine mounting I with through for my Europa and 914. It is covered in my Europa build gallery, Albums: Year 5 Q3 though Year 6 Q3. Perhaps there's something in the design of the Europa engine mount to Rotax ring mount that will do some good. You might also try the Europa web site ( http://www.europa-aircraft.co.uk/ ) under their Builders Assistance > Builders Manuals > 912 XS Jul 09 (Rotax 912 Installation) for more hints.
Good luck,
Bob Borger
Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S
http://www.europaowners.org/forums/gallery2.php?g2_itemId=60232
http://www.biplaneforumgallery.com/index.php?cat=10046
Europa Flying!
3705 Lynchburg Dr.
Corinth, TX 76208
Home: 940-497-2123
Cel: 817-992-1117
On Apr 18, 2010, at 11:59, Dan Billingsley wrote:
>
> Thought I'd try for an answer here...
> I am installing a 912s on my Kitfox IV. I have placed the 4 braces on the top
and bottom of the engine. The intake manifold is off as is the starter. I am
still having a fight with the water pump being in the way. Has anyone dealt with
this b-4 and did you have to take the water pump off? I sure hate breaking
that seal. Wondering if I'm just not holding my mouth right :>)
> thanks in advance,
> Dan B / Mesa, AZ
>
>
>
>
Message 8
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
Dave G a crit :
> Just to be clear, (and again I will never demand proof or challenge
> your opinion) is it your feeling that running in the state people are
> discussing here WILL cause harm, or merely a caution that harm MAY
> result.
What's for sure is that you'll use the engine outside what it was
designed for. May it cause harm, or will it cause harm, and to what extent ?
A few examples :
- The manufacturer says not to take off before the engine is thoroughly
warm. What if one just starts up and takes off ? May it harm the engine,
or will it cause harm ?
- The manuals say to never run with no oil. What if one omits to add
new oil after draining the engine ? May it or will it harm ?
In either case the engine will run sweetly and smoothly.
We have usually few means of knowing how much harm mishandling may cause
to a particular engine.
What's sure is there are dos and don'ts for engine management, and the
careful pilot/operator will do the dos and avoid the don'ts.
I personally do my best to handle engines as correctly as I can.
Best regards,
--
Gilles
http://contrails.free.fr
Message 9
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
Hi Gilles
"Just to be clear, A few examples :The
manufacturer says"
I am not advocating not doing what the Mfg.
says to do, nor am I advocate of always doing what the mfg. says to
do.Best gain all available information and make your own informed
decision. For example as the Mfg. recommends, I will use on my 914 series
with bypass fuel systems, with added Europa twist of adding a second
Andair 375 Gasculator to allow second pump to have ability to draw from
another source. I willl only use Wacker spark plug thermal conductive
compound. I will check Carbon Monoxide levels above 100% power. I will if
my life were threatened by the wastegate opening, would follow DO
procedure in operators manual to leave it closed until obsticle is
cleared. I can go on and on, but if anyone is not following the above
procedure does it make them unsafe or putting life and engine at
risk?If you don't follow Mfgs. procedure perhaps the answer perhaps
isyes, perhaps no, need to take on a case by case basis. Rotax is
not an absolute advocate of only flying a 914 with a differential pressure
gauge IMHO they should be. If you are not pretty certain, and not willing
to trust your life and your equipment to your decision then best follow
Mfgs suggestions, ALL OF THEM. One of my suggestions is to RTFM and at
least know and understand what Rotax suggests. Then follow everything,
unless like I,you too choose to question and research a written word
and do otherwise.
BTW, did you ever verify with Carbon Monoxide test
as suggested or required by Rotax (older serial number engines and if you
have a Intercooler it is a requirement) that you are running rich enough
on all 4 cylinders above 100% power? If you didn't use Carbon Monoxide
detector, how did you verify?
Ron Parigoris
Message 10
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| Subject: | Brake and Billet Pump updates |
Gents,
For those who are interested, I have updated the sections on the MDO
Brake Master Cylinder (MAITRE CYLINDRE DE FREIN =AB AU MANCHE =BB)
modification and the new Billet mechanical fuel pump for the Rotax 914.
The brake is almost completed. Monday or Tuesday, I'll go to the
airport after work and get it all connected up and working.
As for the Billet pump, it is closer but still has some issues to
resolve before I begin the actual installation. I have no doubt that
the Billet pump will work as advertised, it's just that no mod, no
matter how simple it sounds, ever goes easily.
Once I have the new brake system functioning and tested, I'll feel like
I can tackle completing the Billet pump.
Check six,
Bob Borger
Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S
http://www.europaowners.org/forums/gallery2.php?g2_itemId=60232
http://www.biplaneforumgallery.com/index.php?cat=10046
Europa Flying!
3705 Lynchburg Dr.
Corinth, TX 76208
Home: 940-497-2123
Cel: 817-992-1117
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