Rotax RPMs

wrote in
:

On Nov 29, 3:31 pm, "Maxwell" wrote:

I haven't flown one, so I can't be certain, but I'm guessing it would
at least seriously hamper the engines ability to windmill during a
temporary fuel starvation, or carb ice situation.

If a Lyc or Continental dies due to carb ice, it isn't going to
restart either. It needs air and fuel to generate heat to get the ice
out, and a pilot who lets things deteriorate until the thing is dead
is faced with a forced landing whether it's a direct-drive engine or a
geared engine.
Continental has built geared engines: The GO-300, GO-480, the
Tiara (not too successful), and there are many geared radials. Most
have some RPM range where they're not comfortable, and some direct-
drive setups have the same due to prop resonance. The Cherokee 180
was one of them. There's a yellow arc on the tach: pass through it,
don't linger there. All will be well.
Geared engines are more efficient in terms of weight/HP ratio.
HP is a function of torque times RPM, so raising RPM gets more jam for
a small weight increase in the form of a reduction of some sort.
Gears, V-belts, timing belts, chains; they've all been employed. In
some engines it improves safety by taking the thrust and gyroscopic
forces off the crankshaft and putting them onto something more
suitable.
If it hadn't been for geared engines we wouldn't have had the
P-51, P-40, Spitfire, P-38, Lancaster, and many more. On the other
hand, the other side wouldn't have been such a threat.

Dan

Again, it goes back much further than that. Hisso had a lot of success with
their geared version of the 8VA back in '17...

Bertie

wrote in message
...

If a Lyc or Continental dies due to carb ice, it isn't going to
restart either. It needs air and fuel to generate heat to get the ice
out, and a pilot who lets things deteriorate until the thing is dead
is faced with a forced landing whether it's a direct-drive engine or a
geared engine.

Not true, been there and done it.

"Maxwell" wrote in message
...
I'm guessing it would at least seriously hamper the engines ability to windmill
during a temporary fuel starvation, or carb ice situation.

A windmilling propeller significantly increases your sink rate when your
engine stops making noise. Do you really want that? ...or would you rather
have more time to sort things out, and/or more landing options within gliding
range?

I know my choice!

Vaughn

On Nov 29, 3:47 pm, (Paul Tomblin) wrote:
In a previous article, said:

A quick Google search yielded this info on the engine used in the
Remos:

http://www.rotaxservice.com/rotax_en...ax_912ULSs.htm

Ok, I'm a little embarassed that I couldn't find that info myself.

Is a reduction gearbox seen as a reliability problem, or isn't that such a
big deal any more?

--
Paul Tomblin http://blog.xcski.com/
"Oh my G'Quan, they killed Koshi!" - Citizen G'kyle, Babylon Park

I don't think anyone really knows the reliability of this engine and
gearbox. It hasn't been in service long enough. I have been training
behind one in a Flight Design CT, and it is not a noisy engine at
all. When I watch a CT take off I am really struck by how quiet the
airplane is. Also the engine has altitude-compensating carbs, so
there is no mixture to mess with. In flight the engine is very
responsive and smooth. I know a lot of people are put off by the high
rpms, but if the engine is designed to run at those speeds I am not
sure that is really a problem.

My one comment on the gearbox is it has a harmonic resonance vibration
at about 1800-1900 rpm (taxi speeds) which is very noticeable. I try
to avoid that, and bump it up to about 2000, and it's nice and smooth
there.

Phil

Phil wrote in
:

On Nov 29, 3:47 pm, (Paul Tomblin) wrote:
In a previous article, said:

A quick Google search yielded this info on the engine used in the
Remos:

http://www.rotaxservice.com/rotax_en...ax_912ULSs.htm

Ok, I'm a little embarassed that I couldn't find that info myself.

Is a reduction gearbox seen as a reliability problem, or isn't that
such a big deal any more?

--
Paul Tomblin http://blog.xcski.com/
"Oh my G'Quan, they killed Koshi!" - Citizen G'kyle, Babylon Park

I don't think anyone really knows the reliability of this engine and
gearbox. It hasn't been in service long enough.

It's been around almost twenty years now!


Bertie

"Bertie the Bunyip" wrote in message
.. .
Phil wrote in
:

On Nov 29, 3:47 pm, (Paul Tomblin) wrote:
In a previous article, said:

A quick Google search yielded this info on the engine used in the
Remos:

http://www.rotaxservice.com/rotax_en...ax_912ULSs.htm

Ok, I'm a little embarassed that I couldn't find that info myself.

Is a reduction gearbox seen as a reliability problem, or isn't that
such a big deal any more?

--
Paul Tomblin http://blog.xcski.com/
"Oh my G'Quan, they killed Koshi!" - Citizen G'kyle, Babylon Park

I don't think anyone really knows the reliability of this engine and
gearbox. It hasn't been in service long enough.

It's been around almost twenty years now!


Bertie

Yeah, but other than that 20 year history, there is very little data. ;-)

KB

Phil wrote:
On Nov 29, 3:47 pm, (Paul Tomblin) wrote:
In a previous article, said:

A quick Google search yielded this info on the engine used in the
Remos:
http://www.rotaxservice.com/rotax_en...ax_912ULSs.htm
Ok, I'm a little embarassed that I couldn't find that info myself.

Is a reduction gearbox seen as a reliability problem, or isn't that such a
big deal any more?

--
Paul Tomblin http://blog.xcski.com/
"Oh my G'Quan, they killed Koshi!" - Citizen G'kyle, Babylon Park

I don't think anyone really knows the reliability of this engine and
gearbox. It hasn't been in service long enough. I have been training
behind one in a Flight Design CT, and it is not a noisy engine at
all. When I watch a CT take off I am really struck by how quiet the
airplane is. Also the engine has altitude-compensating carbs, so
there is no mixture to mess with. In flight the engine is very
responsive and smooth. I know a lot of people are put off by the high
rpms, but if the engine is designed to run at those speeds I am not
sure that is really a problem.

I'd like to get some more information on this.
The Rotax 912 has been in production since
around 1992 and the 912ULS since 1999. Should
be information somewhere.

I've heard that thousands of them have been
sold for drones and unmanned aircraft of various
types.

My one comment on the gearbox is it has a harmonic resonance vibration
at about 1800-1900 rpm (taxi speeds) which is very noticeable. I try
to avoid that, and bump it up to about 2000, and it's nice and smooth
there.

Yup. That's why there's a yellow band on
the tach. I try to never run my engine there.

Jim Stewart wrote in
:

Phil wrote:
On Nov 29, 3:47 pm, (Paul Tomblin) wrote:
In a previous article, said:

A quick Google search yielded this info on the engine used in the
Remos:
http://www.rotaxservice.com/rotax_en...ax_912ULSs.htm
Ok, I'm a little embarassed that I couldn't find that info myself.

Is a reduction gearbox seen as a reliability problem, or isn't that
such a big deal any more?

--
Paul Tomblin http://blog.xcski.com/
"Oh my G'Quan, they killed Koshi!" - Citizen G'kyle, Babylon Park

I don't think anyone really knows the reliability of this engine and
gearbox. It hasn't been in service long enough. I have been
training behind one in a Flight Design CT, and it is not a noisy
engine at all. When I watch a CT take off I am really struck by how
quiet the airplane is. Also the engine has altitude-compensating
carbs, so there is no mixture to mess with. In flight the engine is
very responsive and smooth. I know a lot of people are put off by
the high rpms, but if the engine is designed to run at those speeds I
am not sure that is really a problem.

I'd like to get some more information on this.
The Rotax 912 has been in production since
around 1992 and the 912ULS since 1999. Should
be information somewhere.

I've heard that thousands of them have been
sold for drones and unmanned aircraft of various
types.


There's been quite a lot of them on certified airplanes in Europe as
well as thousands on homebuilts round the world for quite some time.

It's pretty easy to check how well they work in the real world. Look for
airplanes for sale with the engine installed. If most of the airplanes
with around 1,000 hours on them have engines with about 500 hours on
them, well, you have your answer. But afaik, they work well and last a
long time.

Bertie

Phil,

I don't think anyone really knows the reliability of this engine and
gearbox. It hasn't been in service long enough.


Are you kidding? These have been in service in huge numbers for well
over a decade. The original Diamond Katana was introduced with them.
These engines are VERY proven. It may have happened outside the US (and
thus outside the advertising range of "Flying" and thus outside their
editorial coverage), but trust me, it still happened.

--
Thomas Borchert (EDDH)

On Nov 30, 9:34 am, Thomas Borchert
wrote:
Phil,

I don't think anyone really knows the reliability of this engine and
gearbox. It hasn't been in service long enough.

Are you kidding? These have been in service in huge numbers for well
over a decade. The original Diamond Katana was introduced with them.
These engines are VERY proven. It may have happened outside the US (and
thus outside the advertising range of "Flying" and thus outside their
editorial coverage), but trust me, it still happened.

--
Thomas Borchert (EDDH)

I thought the 912 was fairly new. I can't find a history of the
engine. Anybody know when they first came out?

Phil