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litesellme(at)yahoo.com
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 Posted: Wed Apr 14, 2010 1:37 pm Post subject: Why exactly shouldn't you run a 914 without a prop? |
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They say if you run a rotax 4 stroke without a prop you will chatter the gear box; I believe its just BS. I test run all my rotax 914 engines without a prop and they never shed chips.
--- On Wed, 4/14/10, FLYaDIVE <flyadive(at)gmail.com> wrote:
| Quote: |
From: FLYaDIVE <flyadive(at)gmail.com>
Subject: Re: Re: Why exactly shouldn't you run a 914 without a prop?
To: rotaxengines-list(at)matronics.com
Date: Wednesday, April 14, 2010, 2:03 PM
--> RotaxEngines-List message posted by: FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)>
Guys:
Why are you becoming Theoretical Physicist and reinventing the wheel?
Here is two hunks of information that are prevalent and should be followed:
1 - In all my training with internal combustion engines in 45 years...
You NEVER run an engine with out a flywheel of some type or a load.
The prop is both a flywheel and a load.
Now if you don't believe this jump to item 2...
2 - Call up ROTAX and ask them: if they will warranty the engine if
you tell them that you ran it without a flywheel or a prop?
The reason for the flywheel or load is so you reduce or eliminate the
possibility of the engine RUNNING AWAY... Over reving. Have you ever
been to the race track and the drive shaft shears and WHAM.... One
hell of a runaway situation. That is one reason why they put
explosion blankets around the flywheel.
Barry
On Wed, Apr 14, 2010 at 9:51 AM, Gilles Thesee
<Gilles.Thesee(at)ac-grenoble.fr (Gilles.Thesee(at)ac-grenoble.fr)> wrote:
| Quote: | --> RotaxEngines-List message posted by: Gilles Thesee
<Gilles.Thesee(at)ac-grenoble.fr (Gilles.Thesee(at)ac-grenoble.fr)>
AmphibFlyer a écrit :
>
> I ran that very engine three days ago myself with no prop and it idled
> perfectly smoothly.
How do you qualify a "perfectly smooth" idle ?
My engine also idles perfectly smoothly (with a prop attached, though)
between 1100 and 1800 rpm, and yet Rotax advises against idling below 1400
rpm, due to stress and chatter in the reduction gear, which to date I have
never been able to detect.
Did you take special measures to ensure acceptable stress in the reduction
gear, or do you simply *think* things are okay ?
BTW our project uses *no* springs for the throttles, but push-pull controls.
And of course idle and full throttle stops.
Best regards,
--
Gilles
http://contrails.free.fr
http href="http://forums.matronics.com/" target=_blank>http://forums.matronbsp; - List Contribution Web Site -http://www.matronics.com/contribution
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ransman
Joined: 08 Aug 2008
Posts: 8
Location: Sweden
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| Posted: Wed Apr 14, 2010 2:19 pm Post subject: Why exactly shouldn't you run a 914 without a prop? |
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Interesting discussion!
Because I am not a rocket scientist
the only way I know is to read the manual.
it says:
"Never run the engine without a propeller installed as engine would
suffer severe damage by overspeeding.
Never fit propeller directly to crankshaft."
(this can be read at page 121)
http://www.rotax-aircraft-engines.com/pdf/dokus/d04050.pdf
/// Sauli
[quote] ---
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"Cum propris suis alis volat"
He flies with his own wings |
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rparigoris
Joined: 24 Nov 2009
Posts: 805
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| Posted: Wed Apr 14, 2010 5:51 pm Post subject: Re: Why exactly shouldn't you run a 914 without a prop? |
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Was turning over my 914 today to move around a little lubrication and figure I should make the point that the Rotax 914 does in fact have a flywheel. Gilles a while back you posted a picture of a crankshaft stating there is no flywheel. You didn't mention the picture that attaches to the aft (opposite the prop) end. #19 which is called by Rotax the Flywheel hub, and #1 Magnito ring that is a big hunk of metal that is attached to the outside OD of Flywheel hub. Together these components are in fact a substantial piece of rotating mass (flywheel). That said if you were to mount a 914 on a motorcycle, it would probably be OK as is, but for easier drivability, you may want more flywheel when operating at lower RPMs.
For sure if you used a new engine it would be one costly motorcycle!
Ron Parigoris
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