Ok guys

New to electrics but not RC flying.

What''s the difference between an inrunner motor and an outrunner motor. I''m assuming it has to do with application.

Danny

The most obvious difference is that in an outrunner, the fixed windings are on the inside, while the outer can holding the magnets rotates around the windings. With an inrunner, the fixed windings are on the outside, while an inner shaft holding the magnets rotates inside the windings.

- Jeff

Also, outrunners generally produce greater torque while spinning more slowly than inrunners. This allows for the use of larger props in applications requiring greater thrust and slower speeds. Inrunners are good for spinning smaller props at higher speeds in applications that require greater speed at the expense of thrust. You have assumed correctly.

Thanks Guys

Because of the torque difference mentioned above, outrunners are typically used to direct drive props, while inrunners are typically used with gearboxes to drive props. Although some inrunners are used to direct drive small props, especially in small, high speed planes.

Direct driving with an outrunner has the advantage of not having a gearbox that can generate noise and suffer mechanical failure. Using an inrunner with a gearbox has the advantage of flexibility, you can choose from a wider range of props, and adjust the gearbox ratio to keep your current draw within the limits of your motor/ESC/battery. With an outrunner, you have a more limited prop selection to keep under your max current limit.

Which motor (outrunner vs. inrunner) is more efficient = less watts/amps required to power the same direct drive ducted fan.

Is the 5100Kv outrunner a better investment at $63 or the 5100Kv inrunner introductory price of $35. Which one will outlast the other given the same use-care. Please explain.

5100Kv inrunner - http://www.hobby-lobby.com/brushless-eth.htm
5100kv outrunner - http://www.hobby-lobby.com/littlescreamers.htm