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

   Paul,

   Has anyone tried making a rotor in two halves, machined from steel for
   minimum weight, E-Beam welding them together, then finish machining them?  I
   think they could be nearly as light as the aluminum rotors.

   Steve Brazil

Steve,

That is what my intention is. Either laser weld or braze together as a
two piece or three piece idea. With the type of steels we have out there
you can make the wall thickness pretty damn small in comparison to the
cast iron ones. All the durability with the same weight [as aluminum].

Rob Woods

What about stiffness Rob? You might set up some ringing when the engine fires which may lead to fatigue. The modulus of elasticity of cast iron is 14 million while that of steel is 30 million. Panel stiffness is the cube of the wall thickness as I recall.

Why not titanium? Ted is ready to build some if
you give him a dwg. Titanium can be welded in the right inert atmosphere.

Paul Lamar