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  #21  
Old March 25th 08, 02:47 PM posted to rec.aviation.homebuilt
Barnyard BOb
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Posts: 169
Default subaru diesel

On Tue, 25 Mar 2008 08:39:12 -0500, Barnyard BOb
wrote:


Morgans" wrote:


"Dale Scroggins" wrote

It's going to need a starter; diesels are hard to hand prop. And the
engine is not likely designed to handle thrust and gyroscopic loads.


Many auto engine cranks have done well with these loads, and no extra help.


Name 'em and define what you mean by 'no extra help'?

and need for a well-supported prop shaft, a nose-piece casting with
bearings and a prop shaft will be needed.


Not a given, IMHO.


YES.... 'a given' or something very close to one for safety sake.

Wait until it is being used, and see how well it does, is my opinion. It
will let us know, by how it does after it has been eXperimented with, I
believe. You may be surprised. I might be, too. Until then, keep an open
mind.


Aw phoof!

A promising answer or solution is always just around the corner.
In the meantime, I guess you can fly around in a baloon filled with
the hot air generated here!

- Barnyard BOb -


P.S.

Morgans....
Dunt waist yer tyme tellin mee howe too speal balloon, o-kay?

- Barnyard BOb-



  #22  
Old March 25th 08, 05:12 PM posted to rec.aviation.homebuilt
Morgans[_2_]
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Posts: 3,924
Default subaru diesel


"Barnyard BOb" wrote

Morgans....
Dunt waist yer tyme tellin mee howe too speal balloon, o-kay?



O.K., but I thought you were going for baboon! ;-)
--
Jim in NC


  #23  
Old March 25th 08, 07:54 PM posted to rec.aviation.homebuilt
Barnyard BOb
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Posts: 169
Default subaru diesel

On Tue, 25 Mar 2008 12:12:50 -0400, "Morgans"
wrote:


"Barnyard BOb" wrote

Morgans....
Dunt waist yer tyme tellin mee howe too speal balloon, o-kay?



O.K., but I thought you were going for baboon! ;-)

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

If I was mean spirited..... you would be corrrect.
I would have called you a hot air BABOON!

However, I'm still just the classic grouch, Jim!!!!

Bless you and all the world's Corvairs. 8-)


- Barnyard BOb -


  #24  
Old March 25th 08, 11:00 PM posted to rec.aviation.homebuilt
Capt. Geoffrey Thorpe
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Posts: 790
Default subaru diesel

"Dale Scroggins" wrote in message
...

"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote in message
news:N6adnXfOAtwpgHXanZ2dnUVZ_sWdnZ2d@wideopenwest .com...

...
Hmm. So the dozens of induction fires (some of which caused substantial
damage) that I've witnessed over the years are just as likely with a
diesel engine?


Probably not, since there is no fuel in the induction system.


10. Props are more efficient at lower RPMs, usually. Diesels have
torque to turn props slow in cruise, like a turboprop (1800-1900 RPM),
giving maybe another 5% efficiency gain, and a quieter cabin to boot.


Depends on how the engine was designed, not how the fuel is ignited.


Hmm again. So the burn characteristics of the fuel, the ability to inject
additional fuel after initiation of combustion, and the surplus of
available oxygen have no impact on engine torque curves?


On the contrary. The inabilty to mix the fuel with the air is the reason
that typical diesel torque curves flatten out at low speeds - a gas engine
can better use the air and generates more torque at the higher speeds. So
the TENDANCY is to select bore/stroke ratio's and displacements that favor
lower speeds in diesels. But there are lots of exceptions.

..
Wasn't the prospect of a relatively light weight diesel available to
homebuilders the point of this thread? No one knows if Subaru's diesel
will match the durability of a current-production avgas engine. However,
newer diesel injection methods have helped reduce internal engine forces,
so durable, light diesel engines are on the horizon.

What do you see as the advantages of diesel aircraft engines?


Primary advantage is fuel consumption - higher compression, lower pumping
losses (minor benifit for aircraft) and reduced heat loss due to the
stratified nature of the combustion all help to improve efficiency.
Increased fuel density also gives a boost to "miles per gallon" - but for
aircraft it's about "miles per pound".

Primary disadvantage is power to weight. Diesels are typically smoke
limited - they can't use all the air, so the power is limited - that's why
turbos are so popular on diesels. The higher combustion pressures also
require a heavier block and a heavier bottom end which, well, being heavier,
adds weight.

Secondary advantage is no ignition system. Secondary disadvantage is a
somewhat fussy fuel system (and, with a common rail system, you are just as
reliant on electricity as an electronic fuel injected gas engine). Probably
less of a problem for aircraft use when compared to small marine
applications - do a search on "fuel polishing"...

FWIW - look for the press propaganda on Ford's "Eco-Boost" - turbo charged,
direct injection, spark ignited gas - looks like they are shooting to get
closer to diesel fuel economy without the cost (diesel aftertreatment is
REAL expensive at the lower emission standards). Improving power to weight
lets them downsize the engine, down size vehicle componants, etc.

Of course, one could say that direct injection gasoline has all the
disadvantages of both gasoline and diesel engines. ;-)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

  #25  
Old March 25th 08, 11:18 PM posted to rec.aviation.homebuilt
Capt. Geoffrey Thorpe
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Posts: 790
Default subaru diesel

"Blueskies" wrote in message
t...
...

Why any sort of reciprocating engine?...small turboprops would be the best
solution of they can get the mass fuel flow problems resolved...


Nothing like the laws of thermodynamics and material limitations to ruin a
good party.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

  #26  
Old March 26th 08, 01:10 AM posted to rec.aviation.homebuilt
Capt. Geoffrey Thorpe
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Posts: 790
Default subaru diesel

"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote in message
...
"Dale Scroggins" wrote in message
...

"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote in
message news:N6adnXfOAtwpgHXanZ2dnUVZ_sWdnZ2d@wideopenwest .com...

...

...
What do you see as the advantages of diesel aircraft engines?


Primary advantage is fuel consumption - higher compression, lower pumping
losses (minor benifit for aircraft) and reduced heat loss due to the
stratified nature of the combustion all help to improve efficiency.
Increased fuel density also gives a boost to "miles per gallon" - but for
aircraft it's about "miles per pound".


Oh, I forgot, they can run on Jet fuel if the injector pump will tolerate
it...



On the downside, diesel fuel is good for growing algae, dunno about jet
fuel - but given the number of hanger queens at the typical airport, I
assume we will find out when diesels make a dent in the aircraft market.







--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

  #27  
Old March 26th 08, 01:46 AM posted to rec.aviation.homebuilt
Morgans[_2_]
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Posts: 3,924
Default subaru diesel


"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote

Nothing like the laws of thermodynamics and material limitations to ruin a
good party.


Yep. Small turbine engines are not fuel efficient, and yet they are
expensive. The materials are exotic, and so are the methods that have to be
used to construct the engine.

The gains that have been made with small turbines are amazing enough to me,
but they still have not gone to where they need to be, to be practical.

That said, I still want one of those rigid skydiving wings, with the 4 pack
of model jet engines! What a rush that HAS to be!
--
Jim in NC


  #28  
Old March 26th 08, 02:26 AM posted to rec.aviation.homebuilt
Peter Dohm
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Posts: 1,754
Default subaru diesel


"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote in message
news:mLWdneP7Q9QVCXTanZ2dnUVZ_sqinZ2d@wideopenwest .com...

Primary advantage is fuel consumption - higher compression, lower pumping
losses (minor benifit for aircraft) and reduced heat loss due to the
stratified nature of the combustion all help to improve efficiency.
Increased fuel density also gives a boost to "miles per gallon" - but for
aircraft it's about "miles per pound".


Oh, I forgot, they can run on Jet fuel if the injector pump will tolerate
it...

AFAIK, the newly demanded ultra low sulphur diesel fuel is nasty stuff for
the pumps, because the hurriedly implemented refining process also strips
lubricants from the fuel. I have no idea whether this will be a continuing
problem or whether other processes maintain the lubricity of the fuel.


On the downside, diesel fuel is good for growing algae, dunno about jet
fuel - but given the number of hanger queens at the typical airport, I
assume we will find out when diesels make a dent in the aircraft market.


I don't know about the kerosene based jet fuel sold here in the U.S., but
some of the foreign stuff is (or at least was) a feeding ground for
micro-organisms. The Eastern Airlines L-1011 that went down in the Florida
Everglades some years ago was apparently full of the stuff after having been
previously refuelled in Israel.

BTW, I'm glad someone remembers what a hangar queen is. ;-))

Peter


  #29  
Old March 26th 08, 03:12 AM posted to rec.aviation.homebuilt
cavelamb himself[_4_]
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Posts: 474
Default subaru diesel

Morgans wrote:

"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote


Nothing like the laws of thermodynamics and material limitations to ruin a
good party.



Yep. Small turbine engines are not fuel efficient, and yet they are
expensive. The materials are exotic, and so are the methods that have to be
used to construct the engine.

The gains that have been made with small turbines are amazing enough to me,
but they still have not gone to where they need to be, to be practical.

That said, I still want one of those rigid skydiving wings, with the 4 pack
of model jet engines! What a rush that HAS to be!



If you got the money, I got the time!



--
(remove the X to email)

It's never too late to be the person you might have been.
George Elliot
  #30  
Old March 26th 08, 03:18 AM posted to rec.aviation.homebuilt
cavelamb himself[_4_]
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Posts: 474
Default subaru diesel

cavelamb himself wrote:

Morgans wrote:

"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote


Nothing like the laws of thermodynamics and material limitations to
ruin a good party.




Yep. Small turbine engines are not fuel efficient, and yet they are
expensive. The materials are exotic, and so are the methods that have
to be used to construct the engine.

The gains that have been made with small turbines are amazing enough
to me, but they still have not gone to where they need to be, to be
practical.

That said, I still want one of those rigid skydiving wings, with the 4
pack of model jet engines! What a rush that HAS to be!




If you got the money, I got the time!





But YOU are doing the first flight!
 




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