stupid ?s

[TheMan5952]

Not sure how they measure it, Maybe the hook something on the shaft and that measure it. Not sure.

[Steve]

Brake Horse power is the power rating at the wheels and shaft horse power is measured at the output shaft of an engine. Most people use brake horsepower for vehicles because it is easier to drive it on a dyno than to pull the engine and hook it up to a water brake.

[TheMan5952]

Hey Steve, When I was reffering to shaft HP, I was talking about Helicopter Rotor Shafts.

[Steve]

Yep, SHP could refer to the power turbine out put shaft of a helicopter or any turbine engine, or crankshaft of a recipricating engine. I guess you could use it to measure anything that produced torque. As far as I know the only difference in BHP and SHP is where it is measured. SHP is at the source, BHP is at the wheels. By the way I like your reference to helicopters. I'm an Instructor Pilot for the CH47D Chinook in the Army. My website has some pictures from Desert Storm, if you want to see some serious SHP (7500 SHP).

[TheMan5952]

sweet, that sounds awesome.

They also have Net BHP and Gross BHP. Difference is at Wheels and at flywheel with all accesories (Alternator, Power steering pump, water pump, A/C).

[Porsche]

Your're a Chinook training pilot? That is so cool. Does it make the 7500 SHP from one engine or the two combined? What's the maximum load you've ever lifted? I heard the "Lumberjack" converted models can lift13T.

[Steve]

Thanks, It is alot of fun. The Chinook makes 7500 SHP with two engines. Actually the two engines can make over 10,000 SHP on a standard day at sea level, but that is limited by transmission torque limit of 7500. The extra power capability comes in handy at higher altitudes when the air is thinner and the engine power is less. I have lifted around 24,000 lbs but I didn't have much fuel on board. Normally full of gas it will lift 20,000 easy. Max gross is 50,000. The logging version is stipped down so they can lift more of a load. I think thier max gross may be higher also. If your interested I have some Chinook pictures on my web site.

[texan]

this is an excerpt from an older article of mine on compression science, it should answer the static vs. dynamic compression ratio question.



"Static compression ratio: the total amount of volume in the chamber at BDC vs. the amount at TDC (that's Bottom Dead Center and Top Dead Center, respectively). Now I gave some simplified versions of this in the last discussion to aid in explaining what I was talking about, but here's the actual formula...

Static Compression Ratio = (S+C)/ C
Where S= total swept volume and C= chamber volume, and...

Swept volume= (x² × pi) × stroke
Where X= radius of the bore (bore/2), and...

Chamber volume= cylinder head volume + gasket volume + piston volume + crevice volume

Now it's not important to be able to actually calculate these numbers yourself, as either Honda Motor Co. or your piston provider will have already done this.
What's important is to note that static compression ratio is entirely mechanical, being based solely on swept volume and chamber volume. Meaning that the amount of air flowing into the engine has no effect on static compression ratio. Now, for a quick explanation of VE...

VE (Volumetric Efficiency) is an expression of how much air is actually flowing into an engine vs. how much total air it can displace, and is always expressed as a percentage. For example, a Honda B16A motor has a displacement of 1.6L, so if you had 1.6L of air flowing into and out-of the motor at every 2 RPM (being that these motors are 4 strokes, it takes 2 revolutions of the crank to completely pump air in and out), you would have a VE of 100%. It's VERY important to know here that VE varies with RPM, as the engine's efficiency at flowing air is continually changing. In fact, VE is one of the most important factors to engine performance.

The entire torque curve can be indirectly expressed as a result of VE. The only reasons why it isn't directly proportional to VE are the air/fuel ratio, ignition timing, overall mixture homogeny (uniformity) and frictional losses. Other than that, the VE percentage is basically what makes the torque curve rise and fall on any dyno chart. In fact, it's basically a given to state that maximum torque output of any engine also comes at maximum VE. So OK, as VE rises and drops in an engine, so does power output. But what does that mean?

Well that question leads us to a concept called dynamic compression ratio, which is in truth, probably the most basic of all engine parameters. Th dynamic compression ratio is, simply...

Dynamic CR= static CR x VE

To illustrate, if you had a static CR of 10:1, and had a VE of 90%, you would have...
Dynamic CR= 10 x .9 (90% stated in decimal form), or 9:1 dynamic CR"



Now obviously the explanation as to what this means to performance and combustion dynamics has been left out, but this should give you all the math and background needed to understand each term. Hope this helps, peace.

[JD@af]

I was honestly going to research this tonight and post the differences. Guess I'll take this as another lesson on why not to put things off for too long.

Thanks for the assist, Tex!

[Bean Bandit]

good one Tex:bandit:

[Moppie]

Shp is a measure of the hp at the output shaft that the proppeler or rotors are attached to, not the output shaft of the engine(s).
This way it takes into account having two engine hooked together (as in the chinhook) or changes in torque through a gearbox, (most small planes use some kind of reduction drive).
Its usefull for knowing what size and pitch of propellar/rotor can be used, and how well it will preform.