Today's Message Index:
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1. 06:33 AM - Re: Why exactly shouldn't you run a 914 without a prop? (AmphibFlyer)
2. 06:59 AM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (Gilles Thesee)
3. 02:04 PM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (FLYaDIVE)
4. 02:37 PM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (Gilles Thesee)
5. 02:37 PM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (jason Parker)
6. 03:19 PM - Re: Re: Why exactly shouldn't you run a 914 without a prop? (Sauli Aalto)
7. 06:52 PM - Re: Why exactly shouldn't you run a 914 without a prop? (rparigoris)
8. 07:21 PM - Rotax 914 with 160HP! (rparigoris)
9. 08:38 PM - Re: Rotax 914 with 160HP! (Richard Girard)
10. 09:19 PM - Re: Rotax 914 with 160HP! (rparigoris)
Message 1
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| Subject: | Re: Why exactly shouldn't you run a 914 without a prop? |
rparigoris wrote:
> I have read in the past you shouldn't run a 91X without a prop. Why exactly is
that?
> Here's a guy running a 914 without a prop, seems at low idle without flywheel
effect it isn't quite as happy as with a prop, but just a little higher it seems
pretty happy.
> http://www.youtube.com/watch?v=uksKDll6n7M
> Ron Parigoris
That's Russ Garner, a friend of mine. The reason Rotax says not to run their engines
without a prop is that they attach the carb springs to keep the throttles
wide open unless something pulls them closed. Russ has the springs on the other
way (which is standard for all SeaReys), so the engine idles very nicely
until you open the throttles manually. I ran that very engine three days ago myself
with no prop and it idled perfectly smoothly.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=294168#294168
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
AmphibFlyer a crit :
> 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
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
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@ac-grenoble.fr> wrote:
> <Gilles.Thesee@ac-grenoble.fr>
>
> AmphibFlyer a crit :
>>
>> 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
>
>
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
FLYaDIVE a crit :
> Why are you becoming Theoretical Physicist and reinventing the wheel?
>
Engineers do need physicists to do the calculations first ;-)
> 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?
>
Agree.
> The reason for the flywheel or load is so you reduce or eliminate the
> possibility of the engine RUNNING AWAY... Over reving.
Someone said he obtained a decent idle with no prop. What is unknown, is
the degree of torsional stress imposed on the crank, gears, etc.
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?
They say if you run a rotax 4 stroke without a prop you will chatter the ge
ar 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@gmail.com> wrote:
From: FLYaDIVE <flyadive@gmail.com>
Subject: Re: RotaxEngines-List: Re: Why exactly shouldn't you run a 914 wit
hout a prop?
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@ac-grenoble.fr> wrote:
> <Gilles.Thesee@ac-grenoble.fr>
>
> AmphibFlyer a =E9crit :
>>
>> -I ran that very engine three days ago myself with no prop and it idle
d
>> 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 140
0
> rpm, due to stress and chatter in the reduction gear, which to date I hav
e
> never been able to detect.
>
> Did you take special measures to ensure acceptable stress in the reductio
n
> gear, or do you simply *think* things are okay ?
>
> BTW our project uses *no* springs for the throttles, but push-pull contro
ls.
> And of course idle and full throttle stops.
>
> Best regards,
> --
> Gilles
> http://contrails.free.fr
>
>
le, List Admin.
=0A=0A=0A
Message 6
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| Subject: | Re: Why exactly shouldn't you run a 914 without |
a prop?
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
----- Original Message -----
From: jason Parker
To: rotaxengines-list@matronics.com
Sent: Wednesday, April 14, 2010 11:37 PM
Subject: Re: RotaxEngines-List: Re: Why exactly shouldn't you run a
914 without a prop?
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@gmail.com> wrote:
From: FLYaDIVE <flyadive@gmail.com>
Subject: Re: RotaxEngines-List: Re: Why exactly shouldn't you
run a 914 without a prop?
To: rotaxengines-list@matronics.com
Date: Wednesday, April 14, 2010, 2:03 PM
<flyadive@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@ac-grenoble.fr> wrote:
> <Gilles.Thesee@ac-grenoble.fr>
>
> AmphibFlyer a =E9crit :
>>
>> 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
Message 7
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| Subject: | Re: Why exactly shouldn't you run a 914 without a prop? |
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
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=294275#294275
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| Subject: | Rotax 914 with 160HP! |
Here is a Rotax 914 that claims to produce 160HP for 5 minutes. It is unquestionably
electrically dependent, unless you add Bobs mechanical fuel pump ;-) :
http://www.wired.com/autopia/2009/07/hybrid-aviation/
Ron Parigoris
Just to open another can of worms I wonder if this whirling mass is direct connected
to the non direct connected prop hub?
And another can of worms, do they get rid of the starter motor and save some weight?
And another can of worms, after 5 minutes of motor run, think they use the motor
in reverse to charge things at a much faster rate than 12 amps from the internal
generator?
And another can of worms, lets say you could use as a charger and can extract 15HP
* approx 750 watts thats over 11K watts! Boy seat heat, cabin heat and several
250 watt landing lights, nah make thata half dozen 500 watt landing lights
should not be a problem. Even though slightly inefficient Peltier AC/Heat instead
of just heat?
And another can of worms, I wonder if the power booster electric motor is happy
running on 10% Ethanol?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=294278#294278
Message 9
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| Subject: | Re: Rotax 914 with 160HP! |
Ron, I don't read anything in the article that says the prop isn't directly
connected to the gearbox. How would the motor work as a starter if the prop
weren't connected to the engine?
Starter motors are geared down on the order of 20 to 1, using the electric
motor as a starter would be geared UP 2.43 to 1. That belt is going to take
a beating transferring power at that gear ratio.
There is no free lunch and the motor used as a generator is going to need
some electronics to reverse it's polarity to feed out as a generator, not to
mention it won't be 100% efficient doing it so more power loses for the
engine.
Also not to mention that the 115 hp of the 914 isn't continuous power,
that's only for 5 minutes. Continuous power is only 98.5 @ 5500 RPM.
And about that regenerative power while descending. Typically geared engines
only increase a hundred or two hundred RPM when unloaded during a descent so
any power derived from the electric motor is going to come from burning
gasoline, not from being an airborne windmill.
Sounds to me like a lot of wishful thinking.
Hey, I've got a great idea, put electric motors on the main gear wheels to
get more power for the take off roll. Yeah, I want my plane to be able to do
burn outs, too. And maybe instead of ground loops we could do
drifting.......
Please take this in the humorous intent in which it is written. If you
really want that extra power for take off NOx injection would give the same
power for a hell of a lot less weight to drag around when it's not being
used.
Rick Girard
On Wed, Apr 14, 2010 at 9:19 PM, rparigoris <rparigor@suffolk.lib.ny.us>wrote:
> rparigor@suffolk.lib.ny.us>
>
> Here is a Rotax 914 that claims to produce 160HP for 5 minutes. It is
> unquestionably electrically dependent, unless you add Bobs mechanical fuel
> pump ;-) :
> http://www.wired.com/autopia/2009/07/hybrid-aviation/
> Ron Parigoris
> Just to open another can of worms I wonder if this whirling mass is direct
> connected to the non direct connected prop hub?
> And another can of worms, do they get rid of the starter motor and save
> some weight?
> And another can of worms, after 5 minutes of motor run, think they use the
> motor in reverse to charge things at a much faster rate than 12 amps from
> the internal generator?
> And another can of worms, lets say you could use as a charger and can
> extract 15HP * approx 750 watts thats over 11K watts! Boy seat heat, cabin
> heat and several 250 watt landing lights, nah make thata half dozen 500 watt
> landing lights should not be a problem. Even though slightly inefficient
> Peltier AC/Heat instead of just heat?
> And another can of worms, I wonder if the power booster electric motor is
> happy running on 10% Ethanol?
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=294278#294278
>
>
Message 10
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| Subject: | Re: Rotax 914 with 160HP! |
Hi Rick
I posted some of the notes TIC > but not completely.
I own two BMW Isettas. They incorporate Dynamos, put power in and they are a 1
to 1 electric motor for starting, reverse leads and then becomes a charger.
There is no speak of what electrical source they are using, but for certain it
comes at a weight penalty. If you have 40 HP available and use it for starting,
I don't care if you have a 5 to 1 ratio, it is going to crank a fairly low compression
4 cylinder 1.2 liter engine. I forget the watt output of starter motor,
but think it less than 1 HP. I mention that the prop hub is not connected
directly to gears but it is in fact connected. The dogs and pretensioned thrust
springs "give", but not too much. Just like you can turn motor by hand from
the prop, unless the electric motor has a spraigue type clutch I don't see any
reason it would not function as a starter. The problem I do see is you need
electronics so it doesn't spin things too fast at first with low oil pressure.
Nothing a PWM ESC couldn't easily handle. they are now very "smart", not requiring
sensors and vary timing to mapped configuration using RPM and load as factors.
It is a concept I think perhaps could have some validity. For instance lets take
a 80HP 912. Not the most peppy motor for short field take offs if pitched for
cruise. Lets keep things simple and keep fixed pitch prop, find a 15 to 20 HP
3 phase brushless motor and use the electric motor for take offs. Need be only
2 to 3 minutes that would allow 5750 RPM, kinda like a pseudo CS prop. Since
the duty cycle is limited perhaps could use a very small motor that spins up
high RPMs. Now with technology fastly moving lets say we use something like
Aerogel super capacitors for power. If you were able to get rid of starter motor
weight may not be too bad.
True you don't get something for nothing, but once in cruise could use that motor
to charge capacitors and aid meek internal generator capability.
Guess it should be called a 913DBMN (D for Dream But Maby Not)
When prototypes prove feasible, a integral starter, charger, WEP (War Emergency
Power) unit could be fit to the end of crankshaft instead of current generator/flywheel.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=294288#294288
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