4 ms·
Speaking of helicopters and specific power and weight and all that, it seems an article of faith that eventually an electromotive tail fan will be lighter than
by VLM 10y ago
Speaking of helicopters and specific power and weight and all that, it seems an article of faith that eventually an electromotive tail fan will be lighter than all equivalent reliability mechanical or pneumatic systems. I mean sooner or later as magnet strengths and VFD voltages approach infinity and VFD and motor mass approach zero, at some point the rube goldberg mechanics that make the tail rotor spin will be replaced by a near weightless power cable and electric motor.
You don't need a battery to spin a tail rotor... once the main disk stops spinning there isn't much point in keeping the tail rotor spinning.
A hybrid helicopter is an interesting concept, rather than zero torque the instant the engine dies and hope for good luck WRT autorotation technique, even merely giving the pilot 15 extra seconds of battery thrust would probably save some lives.
- kragen 10y agoPneumatic hoses are pretty light too, and pneumatic motors are usually a lot lighter and more reliable than electric motors of the same power. But maybe you're saying that this is merely a function of low voltages and weak permanent magnets, and we can expect electric motors to get a lot lighter? I guess that's possible; can you point me at some exemplary modern motors? I tried to write a thing here about the physics of the situation — saturation flux densities and layer-wound armatures and resistivities and dielectric strengths and so on — but then I realized that I don't actually understand the physics of electric motors well enough to say anything coherent. How are electric motors increasing their specific powers — is it just by higher RPMs, or is it a matter of more poles and/or better materials and geometries? What are the limiting factors?
- abecedarius 10y agoDrexler gets into electrostatic motor scaling in Nanosystems and presumably his thesis. I have no idea about the kind of designs made today, though.