=A0=20

James Watt came up with the Horse Power mea= surement in order to sell his steam engine to mine owners who used small ho= rses to pull mine carts full of coal up hill on narrow gauge rail tracks.

So, Horse Power is a measure of WORK.

The Watt used to measure the consumption in= electrical devices, is the same James Watt.

So, Horse Power can be converted to, or exp= ressed in Watts.

So, one (small) horse could lift 33,000 pou= nds of coal 1 foot in one minute.

So, one =93Horse Power=94 is then 33,000 po= unds lifted one foot in one minute.

So you need a time (one MINUTE) a distance = (one FOOT) and a FORCE to lift (33,000) pounds.

A single cylinder 2 cycle diesel with a str= oke of two feet (one foot lever to make calculations easy)

and a piston the size of a picnic table mig= ht be able to do this at one RPM, so, it would be a true

one Horse Power engine. It would weigh mayb= e 7,000 pounds in cast iron. A long way to go for one HP.

However through the magic of mathematics (s= ee Ed Anderson) we can build more useful engines, and just measure their ef= fectiveness in James Watt's Horse Power.

By juggling bits of formula around we can c= ome up with one even I can figure out.

One Horse Power is equal to Torque, a twist= ing (FORCE) At the end of a (ONE FOOT) lever times

Revolutions per (MINUTE). Revolutions gives= you the distance, because the torque is at the end of a one foot long leve= r, or one revolution is then one foot times Pi. D (the diameter of a circle= with a one foot radius) or two times Pi. Or 6.26 feet. So we divide the ou= tcome by 5252 (a constant because the little horse cheated by dragging the = load up a long hill not actually lifting it. So a bit of a fudge here ) and= we have all three items needed to replicate the output of James Watts litt= le horse or his steam engine.

Instead of steam to push our pistons or rot= ors about we use a vapor of gasoline in little explosions.

How much vapor determines the FORCE of the = explosion. So more vapor per explosion means

more FORCE against the piston or rotor, and= that means more torque. And that means more HP.

If we move the end of that one foot lever f= urther in one MINUTE, that means more HP. (WORK)

So more work can be had by increasing the T= ORQUE and by increasing the RPM, or both.

In a supercharged or turbo charged engine w= e just jam in more vapor to generate higher TORQUE per REVOLUTION and we ha= ve instant success with more HP (WORK).

We can increase the RPM which is the DISTAN= CE we push the end of that one foot long lever in one

MINUTE, and again we have instant success w= ith more HP (WORK)

The best (for high HP) induction system for= the rotary is the Periphery Port.

The factory made rotor housings for this ap= plication, but they are ridiculously expensive, so many folks manufacture t= heir own Periphery port housings.

The object is to maintain high velocity flo= w, so as the RPM goes higher, and the time available for the

vapor to flow into the passing low pressure= void created by the rotor move away from TDC becomes shorter.

A shorter time at any flow rate means a sma= ller volume per unit of time, of vapor will be inducted.

Turns and other shapes impinging in an indu= ction system cause energy to be lost. The lost energy appears as increased = heat, and lower velocity. The stock or Side Port engines have a turn in the= cast iron just before the vapor enters the engine. So that turn reduces ve= locity right where we want the highest possible velocity. In addition, the = ports in a side port engine are actually closed off by the side of the pass= ing rotor, so, for any RPM, the Periphery port engine has a massive advanta= ge over the side port engine, because the Periphery port is NEVER closed.

Porting a side port engine is an attempt to= increase the time the port is open at any RPM, so as to induct

more vapor per revolution. Longer time=3Dmo= re vapor

This increase of the port opening in three = directions also reduces velocity, so at lower RPM it reduces the amount of = vapor inducted. So, ported side port engines should have reduced low RPM pe= rformance.

And they do.

The later closing intake port extends the c= losing point well past Bottom Dead Center, where the volume of the working = chamber is getting smaller, and the pressure is going up. At low speeds par= t of the vapor in the chamber will be pushed back into the intake. At high = speeds the mass and velocity (Over 350 miles per hour) of the intake vapor = can overcome this pressure and more vapor will enter the chamber before the= port closes.

But we want best power from about 5,000 RPM= on up, so for most applications the low RPM poor performance is not a fact= or.

The STREET PORT is just an increase in open= point and a delay in closing point. A typical closing point for a stock en= gine might be 50 degrees After Bottom Dead Center, and a in a street ported= engine it might be 60 to 65 degrees ABDC. Better top end power, and some l= oss in low RPM power. It is called a Street Port because it is mild enough = to use in a street driven auto.

A big street port might move the open line = so far as to un-support the trailing end of the side seal.

The closing line might be moved to 70 degre= es ABDC.

Much improved top end power. Obvious loss i= n low RPM power.

A small Bridge Port might be of some value = in aircraft use if kept above 5,500 RPM.

A =93J=94 bridge port would be of no value = in aircraft use, because it has no power below 5,000 RPM

And without a controllable pitch prop, migh= t not even be able to pull a prop load into a usable RPM.

Converting Horse Power into thrust with a p= ropeller is best explained by Mr. Anderson.

However I have some thoughts.

When reved up from idle the prop is facing = a mass of air that is barely moving, so the fixed pitch propellers effectiv= e pitch is close to advertised. The prop tips may be slightly stalled.

As the mass of air in front of the propelle= r starts to move through the propeller, the effective pitch

Or, the pitch relative to the moving air ma= ss is reduced, and that un-stalls the tips, and that allows the tips or out= er part of the prop disc to become more effective at moving air and that is= WORK, and the added work load slows the engine slightly.

As the aircraft accelerates, the effective = pitch relative to the air stream is reduced, and this unloads the engine sl= ightly, and the engine RPM increases slightly. Once propeller thrust is equ= al to total drag

engine RPM will remain constant.

You can only go faster if you increase RPM = in order to increase thrust. Or, increase relative pitch to increase thrust= . Or, both.

Advertised pitch, is that blade angle relat= ive to the center-line of the crank shaft. Effective pitch is the angle of = the blade relative to the blade,s path through the airstream.

Propeller blades and wings are the same thi= ng. So, they both operate in relative wind.

Thus the controllable pitch propeller is th= e gold standard and allows the engine to be used at its best power RPM for = any airspeed.

The fixed pitch propeller is limited to a s= mall range of RPM, that only suits the engine's best power in one place= along that RPM range.

The same as driving your car all day in 2nd gear (for a fixed pitch prop) compared to driving all day with = an automatic transmission that keeps changing ratios based on load and thro= ttle setting. (For a variable speed, or controllable pitch propeller).

Thrust (FORCE) from the propeller (MASS tim= es VELOCITY) is the WORK done by the engine.

Or, I could be completely wrong.

Lynn E. Hanover