I see hundreds of electric cars and trucks for sale, sometimes almost a give away on Craigs list. It got me thinking ( why are we not using these cheaper give aways for aircraft use ). I dont know much of todays motors and esc's, is there a reason why they cant be used in aircraft ?
Car ESCs typically are heavier due to the large heat sink needed. Also they are often limited to 2S LiPo
You do have to ensure yo disable the reverse function if the ESC has it... Airplanes generally don't do well if you turn the prop backward.
The motors can work fine for aircraft especially if you want a high rpm.
There are still a lot of brushed motors used n RC cars. At least one of the official racing classes specifies a brushed motor.
Some of them probably 'could' be used if you were determined, but the cheap ones you refer to will invariably be low quality brushed motors and old tech NiCd batteries which are far heavier and have less performance than the brushless motors and LiPos we almost exclusively use in RC planes these days.
Car ESC's are also generally not very well suited to RC planes because cars have reverse, which is a big problem if engaged in flight!
I have used a car esc in my edf (haven't flown it though) it's rated up to 4s. Most escs for cars over 60 amps are 4s. Reverse wouldn't be good, but it would be neat to use on a large plane, if you could activate with a switch. On landings, hit reverse and it would slow you pretty quickly. As for fans, they can be removed usually. As they have a plastic box around them, they'll still weigh more, but not much.