Stupid hp to thrust question

Hi All, thanks for the responses, was not meant to be a trick question but
definately a newbie question. I was curious after reading about people using
mazda 13b engines for various homebuilts, and porting them, adding on
various components to boost the hp from 200 to 260+. Seems at a point that
it's overkill if the 200 hp engine is going to provide you with the needed
ponies and rpms to accomplish the same as the 260 hp engine. What would the
advantge be of having the extra horsepower ?

Thanks,

Mark


"Mark" wrote in message
...
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 ?

In article , "Mark" writes:


Hi All, thanks for the responses, was not meant to be a trick question but
definately a newbie question. I was curious after reading about people using
mazda 13b engines for various homebuilts, and porting them, adding on
various components to boost the hp from 200 to 260+. Seems at a point that
it's overkill if the 200 hp engine is going to provide you with the needed
ponies and rpms to accomplish the same as the 260 hp engine. What would the
advantge be of having the extra horsepower ?

Thanks,

Mark



NOW you have asked the question the right way and will see some good answers.
The advantage of more horsepower is the capability of increased thrust, which
is not a factor of just the RPM but of the ability to convert the horsepower to
usable thrust using a prop geared to the output of the engine. Thrust is
created by the prop and is determined by the RPM of the prop, the length of the
blades, the number of blades and the pitch of the blades along with a host of
other factors. Assuming for one example the same number of blades, the same
RPM, the same length of blades, and other conditions for two engines and two
props, the higher horsepower engine will be able to turn a larger pitch prop
than will the lower horsepower engine and will produce more thrust.

Think of it the same way as a race care. The higher the horsepower available
from the engine, the higher the gear ratio that can be used and the faster the
top end speed.

PS: This is a simple answer to your question but many factors are involved.
The effort to increase a 200 hp engine to 260 hp may or may not be worth the
effort and the 30% increase in hp wil not produce an equilivent increase in
thrust or speed. I don't remember the formula for calculating the increase but
it is far less than anticipated.




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 in message
...
PS: This is a simple answer to your question but many factors are
involved.
The effort to increase a 200 hp engine to 260 hp may or may not be worth
the
effort and the 30% increase in hp wil not produce an equilivent increase
in
thrust or speed. I don't remember the formula for calculating the
increase but
it is far less than anticipated.

Speed increases at about the cube root of the HP increase, so:

(260 / 200) ^ (1 / 3) = 1.091 or about 9% faster with 30% more HP

But other factors to consider are the increased weight of a larger engine,
the increased fuel burn, and the weight of that fuel.

Eric

In article ,
"Eric Miller" wrote:

"RobertR237" wrote in message
...
PS: This is a simple answer to your question but many factors are
involved.
The effort to increase a 200 hp engine to 260 hp may or may not be worth
the
effort and the 30% increase in hp wil not produce an equilivent increase
in
thrust or speed. I don't remember the formula for calculating the
increase but
it is far less than anticipated.

Speed increases at about the cube root of the HP increase, so:

(260 / 200) ^ (1 / 3) = 1.091 or about 9% faster with 30% more HP

But other factors to consider are the increased weight of a larger engine,
the increased fuel burn, and the weight of that fuel.

Eric



Extra horsepower converts directly into rate of climb, assuming the same
weight and airspeed. Fuel consumption rises approximately in proportion
to horsepower; stability decreases.

Other factors in boosting phenomenal horsepower out of small packages:

Increased thermal load
Increased stress on all parts of the engine
Some high RPM ranges may not yield usable thrust because the prop tips
are in the transonic range, where prop efficiency decreases greatly.

RR Urban wrote:
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 ?

To paraphrase the question...

If I put 150 lbs of crap in a 100 lb bag, and 150 lbs of crap in a 150
lb bag, which bag is holding more crap?

nafod40 wrote:

RR Urban wrote:
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 ?

To paraphrase the question...

If I put 150 lbs of crap in a 100 lb bag, and 150 lbs of crap in a 150
lb bag, which bag is holding more crap?

OOooooooo..... *SO* close, and yet just off. I think you meant to say:
"If I put 100 lbs of crap in a 100 lb bag, and 100 lbs of crap in a 150 lb bag,
which bag holds more crap?"

Russell Kent

"Russell Kent" wrote in message
...
nafod40 wrote:

OOooooooo..... *SO* close, and yet just off. I think you meant to say:
"If I put 100 lbs of crap in a 100 lb bag, and 100 lbs of crap in a 150 lb
bag,
which bag holds more crap?"

That's an easy one - A 150 lb (capacity) bag holds more crap than a 100 lb
(capacity) bag.

I think YOU meant to say, "If I put 100 lbs of crap in a 100 lb bag, and 100
lbs of crap in a 150 lb bag, Which bag contains more crap?"

Rich "150 lbs of crap in a 100 lb bag is known as a 'Blivet'". S.

In article , nafod40
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 ?

To paraphrase the question...

If I put 150 lbs of crap in a 100 lb bag, and 150 lbs of crap in a 150
lb bag, which bag is holding more crap?



Damn BOb, you sure are full of CRAP! ;-)))))

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)

"Rich S." wrote:

"Russell Kent" wrote in message
...
nafod40 wrote:

OOooooooo..... *SO* close, and yet just off. I think you meant to say:
"If I put 100 lbs of crap in a 100 lb bag, and 100 lbs of crap in a 150 lb
bag,
which bag holds more crap?"

That's an easy one - A 150 lb (capacity) bag holds more crap than a 100 lb
(capacity) bag.

I think YOU meant to say, "If I put 100 lbs of crap in a 100 lb bag, and 100
lbs of crap in a 150 lb bag, Which bag contains more crap?"

Rich "150 lbs of crap in a 100 lb bag is known as a 'Blivet'". S.

Not so fast. If my eyes aren't deceiving me, the only change you made was
"contains" for "holds". English being an exceptionally slippery language, it
seems to me that those terms are synonymous. Makes it rather hard to give a
definitive answer to the original poster's question if we aren't clear on
whether "hold/contains" means "at the moment" or "at maximum capacity", which I
believe is the issue that nafod40 was attempting to illustrate with his
posting. I was only trying to show that nafod40's choice of numbers weren't
quite parallel to the original poster's question.

BTW, there's entirely too much crap in here. :-)

ob. aviation content: My Dad used to drop blivets from the B-52 he flew. :-)

Russell Kent

Bob Reed wrote:

Damn BOb, you sure are full of CRAP! ;-)))))

I'm sure NO ONE here, not even the crotchety old fool himself, will deny that BOb
is full of crap (sometimes), *BUT* it was nafod40 whom you (Bob Reed) quoted and
not BOb.

Russell Kent