If torque didn't change and RPM
    >  didn't change you have the SAME HP.



Paul and all

Help me out here in relation to lighter rotors.
Clearly If torque didn't change and RPM didn't change then HP cannot change.
But could torque change given no other changes except the mass of the rotor?
This might be stupid, so please a little grace.

Because of the complexity of a rotors directional movement could we for
my sake think in terms of a piston in a cylinder. (sacrilege)
So here is my question.

Would a lighter piston require less “work” (due to it’s having less
inertia at any given velocity) in order to change it’s direction (up and
down/side to side) and so leave more of the potential energy from the
combustion event available at it’s crankshalf as torque?
And if this is so, then how would this translate to a lighter
rotor/eccentric shaft?

In anticipation of learning again how little I actually know.

Steve Izett
Perth Western Australia – Building Renesis 4 port Glasair SII RG

Torque is primarily controlled by the breathing ability of an engine at
any RPM. That is the same as saying the Volumetric Efficiency is good.
A good side port engine has about 160 foot pounds of torque. VE is around
85%. An organ pipe tuned p-port engine will jump up to about 200 foot pounds. VE could be as high as 120%.

There are some other minor factors such as the friction inside the engine.
Less friction more torque at the same RPM. The heat of the charge will also
affect the torque. Higher charge temperature lowers the mass of air getting into the engine. That is why people run inter coolers on turbo charged engines.

It is conceivable that an oil cooled  aluminum rotor running at 100 F below the temperature of a cast iron rotor could result in slightly more torque at any RPM because a higher mass of air could be getting into the engine. The downside would be slightly more fuel burn for a given HP (BSFC) but that is another story.

Lynn Hannover claims he gets more power by keeping the oil as cool as possible.
What might be happening is his oil cooled iron rotors are running at a lower temperature so a higher mass of air is getting into the engine.

BTW in case you were thinking airplanes fly on torque that is not the case.
Airplanes fly on HP alone. Prop torque is anything you want it to be using
a gear box.

Another up side to aluminum rotors is less weight is needed in the counter weights. Aluminum rotors and lower weight counter weights could save about
15 to 20 pounds per engine. The engine would accelerate more rapidly which might be a help to the drag racers.

Combine that with aluminum end housings and you are looking at a a turbo charged  engine that Doug can easily lift and that will put out close to 1600 HP at 23,000 RPM running on alcohol and nitrous oxide:)

Paul Lamar