{"id":8892,"date":"2014-05-16T23:37:31","date_gmt":"2014-05-17T06:37:31","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=8892"},"modified":"2014-05-16T23:37:31","modified_gmt":"2014-05-17T06:37:31","slug":"eas-viii-high-torque-efficiency-powerful-motors","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/eas-viii-high-torque-efficiency-powerful-motors\/","title":{"rendered":"EAS VIII: High Torque, Efficiency and Powerful Motors"},"content":{"rendered":"

David Calley heads Planet Rider LLC<\/a>, a design group working on a highly innovative three-wheel commuter vehicle that combines pedaling, electric power and aerodynamics to make for an exciting ride.\u00a0 Any resemblance between this machine and the average e-bike is like the difference between an early Rogallo wing and the Archaeopteryx.<\/p>\n

\"david<\/a><\/p>\n

He has made a significant notch in fuel savings for big rig trucks with the angular extensions you see on tailgates of trailers cruising America\u2019s highways.\u00a0 Fuel savings of five percent or more are a boon to fleet operators, thanks to Calley\u2019s patented design, now manufactured by ATDynamics<\/a>.\u00a0 He is also a member of the CAFE Foundation\u2019s advisory board.<\/p>\n

\"Trailer<\/a>

Trailer tail reduces big rig drag, cuts fuel use five or six percent<\/p><\/div>\n

Thus, it was informative to see his presentation at the eighth annual Electric Aircraft Symposium.\u00a0 His work on low-RPM motors using his simple transverse flux motor design enables excellent power and high torque from light-weight, compact motors.\u00a0 This fits the need to swing big, slow propellers for applications such as air taxis.\u00a0 He talked about a new motor topology for a coaxial design and for wheel motors that could help accelerate an air taxi to takeoff speed.\u00a0 Airbus is using similar wheel motors on its E-Fan prototype.<\/p>\n

\"David<\/a>

David Calley shows differences between different motor topologies<\/p><\/div>\n

Since airplane propellers are more efficient when less loaded, Calley sees the need for 51 to 100 meter per second (167.3 to 328 feet per second) tip speeds on large, slow-turning propellers \u2013 similar to helicopter rotors.\u00a0 Even the higher speed translates to only Mach 0.29 at sea level, generating very low noise.\u00a0 Compare this to smaller propellers turning at higher speeds, with tip speeds often approaching the speed of sound \u2013 and generating high noise levels in the process.\u00a0 This type of unacceptable racket must be avoided in air taxis, which will be taking off and landing in residential areas to be most useful. \u00a0Noisy propellers are also less efficient.<\/p>\n

\"David<\/a>

David Calley’s figures for weight and power output were impressive – then astounding<\/p><\/div>\n

Motors that can deliver high torque without reduction gearing would be great, and that\u2019s what Calley\u2019s high torque density motors deliver.\u00a0 His E-flight propeller motor, for instance, should be capable of putting out 55 kilowatts (73.7 hp.) for 20 seconds at 600 RPM and 438 Newton meters (323 foot-pounds) of torque.\u00a0 That should be able to accelerate a sky taxi to takeoff speed in a short distance, especially when complemented by a wheel motor using Planet Rider axial transverse flux motor (ATFM) topology, similar to the smaller model on the enclosed Planet Rider three-wheeler.\u00a0 He explained that such a motor could put out\u00a036 hp continuallyfor a weight of\u00a0only 7.6 kilograms (16 pounds), not too eye-brow-raising considering the strides made in more conventional radial and axial flux model aircraft motors in recent years.<\/p>\n

With cool operation, a high pole count ATFM development could, according to Calley\u2019s closing remarks produce up to 40 kilowatts per kilogram, or about 24 horsepower per pound \u2013 and for about $180 worth of electromagnetic materials.<\/p>\n

We wish him well.\u00a0 Low-cost motors that deliver big performance will go a long way toward making electronic flight ubiquitous \u2013 one of Dr. Seeley\u2019s goals for sky taxis.<\/p>\n