> Among motor types, which give the best power ( energy per unit of > time ) to weight ratio ? > I am not going to consider reliability as a factor. > I am not including auxiliary items such as fuel tanks, air lines, > cabling, etc.The misleading answer may be "high pressure gas operated mot= or". A prime example of this is the "topping cycle" gas turbines used to supply the propellant for the Space Shuttle main engines. These sit "before the combustion "chambers proper in the main engines and essentially preburn some incoming propellant. They can be highly efficin\ent because of the high presseures they operate at. (About 4500 psi from memory).(Don't try this at home). The reason that this is misleading is that they are essentially a way to transfer the gas mechanical energy into propellant mechanical energy. All pumps are energy transferers - but a gas turbine is closer to the basic principles than some.=A0That said, the mass and volumetric energy density of the power source can also be about as high as anything else available. Hydrocarbons contain about 10 kWh/kg (or about 36 MJ/kg). Hydrogen about 3 times that from memory. Maybe more. Hydrogen volumetric density is low, but you asked about mass. Brain says that electric motor probably get best results from permanent magnet units as no energy is used in magnetic field production BUT field stengths have an upper limit set by best available materials (various rare earth magnets) and if you were happy to waste energy a wound field MAY get higher values. Power out is primarily a function of the amount of power you can get into the motor :-). This is translated into creating interacting magnetic fields. Simplistically, increasing voltage and decreasing current will tend to allow higher energy densities as resistive losses decrease with square of voltage, but here is a point at which other factors take over. =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 Russell McMahon 2009/10/16 NOPE9 > > Among motor types, which give the best power ( energy per unit of > time ) =A0to weight ratio ? > I am not going to consider reliability as a factor. > I am not including auxiliary items such as fuel tanks, air lines, > cabling, etc. > > Air motor > Electric Motor > =A0 =A0 =A0 Brushless > =A0 =A0 =A0 Stepper > =A0 =A0 =A0 Brush > =A0 =A0 =A0 AC Synchronous > =A0 =A0 =A0 Induction > Hydraulic Motor > Rubber Band Motor :) > Mystery Motor > > FOR ELECTRIC MOTORS > Short of using superconductors, what improves the P/W ratio for an > electric motor ? > I suppose running hotter with more current might improve the P/W. > Is the power a function primarily of the amount of current moving > through the motor ? > > Best > Gus > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist