Stupid hp to thrust question

He got a point!

"Gilan" wrote in message
nk.net...
there you go thinking again.
you just added something into the question that wasn't there
Just stick to the original question and the answer is still the same.

--
Have a good day and stay out of the trees!
See ya on Sport Aircraft group
http://groups.yahoo.com/group/Sport_Aircraft/

In article , "Mark"
wrote:

Does a prop turning at 2300 rpm on a 150hp motor produce more thrust than a
prop spinning 2300 rpm on a 100 hp motor ?




Insufficient data!

Constant speed prop?
Manifold pressure?
Zero wind?
Same atmospheric conditions?

[Ron throws his oar in]

On Thu, 4 Dec 2003 20:24:00 -0500, "Mark" wrote:

Does a prop turning at 2300 rpm on a 150hp motor produce more thrust than a
prop spinning 2300 rpm on a 100 hp motor ?

Assuming the engines are mounted on a ground test stand, and the propellers
are "normal" (no paddlewheels, etc.):

If the props are identical fixed pitch propellers, the same thrust is
produced. Both engines are producing the same power.

If the engines are NOT producing the same power, it is because their
throttle positions and the propellers. Either may produce more thrust,
depending on the combination of the two parameters. For instance, the 150
HP engine could have controllable-pitch prop at flat pitch....it might turn
2300 with the throttle barely cracked.

If both engines are producing their rated horsepower, the 150 HP engine
produces more thrust. Its propeller must move more air in order to absorb
the higher power at the same RPM.

Ron Wanttaja

On 04 Dec 2003 04:24 PM, Mark posted the following:
Does a prop turning at 2300 rpm on a 150hp motor produce more thrust
than a prop spinning 2300 rpm on a 100 hp motor ?

Yes, unless the 150hp motor is an automotive engine, in which case
bolting a prop to it will cause it to violently self destruct before
reaching 2300rpm. 8^P

Del Rawlins-
++++++++++++++++++

Smoooooch !


Barnyard BOb --
The more people I meet,
the more I luv my dawg,,,,
and George Carlin humor.

Ron Wanttaja wrote in message . ..
[Ron throws his oar in]

On Thu, 4 Dec 2003 20:24:00 -0500, "Mark" wrote:

Does a prop turning at 2300 rpm on a 150hp motor produce more thrust than a
prop spinning 2300 rpm on a 100 hp motor ?

Assuming the engines are mounted on a ground test stand, and the propellers
are "normal" (no paddlewheels, etc.):

If the props are identical fixed pitch propellers, the same thrust is
produced. Both engines are producing the same power.

If the engines are NOT producing the same power, it is because their
throttle positions and the propellers. Either may produce more thrust,
depending on the combination of the two parameters. For instance, the 150
HP engine could have controllable-pitch prop at flat pitch....it might turn
2300 with the throttle barely cracked.

If both engines are producing their rated horsepower, the 150 HP engine
produces more thrust. Its propeller must move more air in order to absorb
the higher power at the same RPM.

Ron Wanttaja


Typical static thrust for the engines in light airplanes is around
three pounds per horsepower, IIRC. This figure will vary somewhat with
prop efficiency and rated RPM. A lower rated RPM for a given HP will
produce more thrust, as less of the energy is lost to prop blade drag.
An example of this is the Thielert Centurion diesel now STCd for
the Cessna 172 N and P models, among others. It produces 135 Hp at
2300 instead of the 160 at 2700 from the Lyc it replaces, yet the
performance doesn't suffer at all. Drag is about 28% less on 16% less
power. These are my rough calculations and I'm open to correction. Try
http://www.centurion-engines.com/
Turning an engine much faster to increase HP has been a standard
trick of both auto manufacturers and aircraft engine makers, but so
much of the increased HP just goes into making more noise, especially
when driving a prop.

Dan

In article
, Orval
Fairbairn writes:


Does a prop turning at 2300 rpm on a 150hp motor produce more thrust than a
prop spinning 2300 rpm on a 100 hp motor ?




Insufficient data!

Constant speed prop?
Manifold pressure?
Zero wind?
Same atmospheric conditions?



Where do you get insufficient data? Question does not indicate a different
prop turning on the two engines. "A" prop indicates the same prop used on two
different hp engines turning at the exact same RPM with no indicated
differences. The resulting thrust will be the same.


Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

In article , ChuckSlusarczyk
writes:


Does a prop turning at 2300 rpm on a 150hp motor produce more thrust than a
prop spinning 2300 rpm on a 100 hp motor ?

If it's the same prop and it turns 2300 on a 150 hp engine the 100hp engine
won't have the power to turn it 2300. If it turns 2300 on the 100 hp engine
then
the 150 hp engine will over rev it and run away the prop. At 2300 rpm the
prop
will produce the same thrust regardless of engine but the 150 hp engine would
really like a bigger prop to use the remaining 50 hp.

see ya Chuck (ain't no free ride in airplanes) S



Ah Hell Chuck, you missed the point of the question here. The thrust produced
will remain the same in both instances regardless of the engine horsepower. If
indeed the 100hp engine is turning the prop at 2300 rpm and requires the full
100 hp to do so, the 150 hp engine is not producing full power to turn the
prop. A 1000 hp engine turning the same prop at the same rpm will still
produce the exact same thrust.


Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

In article , Dan Thomas says...

Turning an engine much faster to increase HP has been a standard
trick of both auto manufacturers and aircraft engine makers, but so
much of the increased HP just goes into making more noise, especially
when driving a prop.

Unless you have a redrive installed so as to be able to use the additional hp.

Chuck S

In article , "Morgans"
writes:


Ah Hell Chuck, you missed the point of the question here.

Bob Reed

I don't think the OP was asking a trick question. While you and I
understand the relation between thrust and HP, I do not think the OP has a
grasp on it. What was not said, was, "if I use the correct prop to get 2300
RPM at full power, will the 100 HP and 150 HP engine have the same thrust?"

On the other hand, I could be reading too much between the lines, and could
be completely wrong. If so, "never mind" :-)
--
Jim in NC




Now that is an entirely different question and the answer is likewise entirely
different. I was not reading anything extra into the original question (for a
change) and the answer would be no difference.




Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

"RobertR237" wrote

Ah Hell Chuck, you missed the point of the question here.

Bob Reed

I don't think the OP was asking a trick question. While you and I
understand the relation between thrust and HP, I do not think the OP has a
grasp on it. What was not said, was, "if I use the correct prop to get 2300
RPM at full power, will the 100 HP and 150 HP engine have the same thrust?"

On the other hand, I could be reading too much between the lines, and could
be completely wrong. If so, "never mind" :-)
--
Jim in NC