a proper outrunner DOES produce more torque, it doesn't really have anyhting to do with Kv, it has to do with physics and design.
I dont see how they can make more torque than an inrunner. If you hold the outside of an outrunner, the torque on the 'inside' bit will still be the same (like an inrunner)
I've seen inrunners with silly low Kv and they still need a gearbox. Inrunners can typically handle higher RPM because the spinning portion has less inertia and a smaller diameter. Outrunners are usually RPM limited because the spinning portion is on the outside, and "distance from center" has a huge effect on centrifugal force that is created. Magnet timing also becomes an issue as the magnets are now travelling farther than a comparable inrunner.
All you need to know is that they produce more power
Nope. They produse more torque but less speed. Inrunners produce more speed, but less torque. This equates to the same amount of "power" or "work", it's just two different ways of doing it. If you want more torque from an inrunner, you need a gearbox to slow the output and give you more torque... To speed up an outrunner you need a gearbox to speed it up, but you lose torque. See the relationship? This is a common misunderstanding and it's why power output is typically calculated in watts.
An inrunner can develop lots of torque, as can any electric motor. But the outrunner design has a trick up it's sleeve that allows it to produce more torque at the expense of rpm. An outrunner has a larger "lever arm" so to speak... Imagine using a torque wrench but when you use it, hold the handle at the halfway point. If your hand moves 3 inches, and you need 20 lb of force to turn a bolt 10° you have accomplished some work at the expense of energy. Now, hold the same wrench at the end of the handle, and you need half as much force to do the same job, but you have to move further for the same "work". Having a longer "lever arm" makes the work of the motor easier, it gives it more torque. This is the exact same idea behind a gearbox, where it allows the same "work" to be accomplished by using less force at the expense of longer actuation distance.
Simple Physics says: Work = Force x Distance. Or, translated for our topic, Power = Torque x RPM. Given a specific power requirement, a motor with higher torque needs less rpm. A motor with less torque needs higher rpm for the same power... Get it?
Another way to visualize this concept is to imagine lifting a boulder. By yourself it would be impossible. But, with a 2x4 suddenly the situation changes.. You could rest the 2x4 over a log with the shortest portion under the boulder. You pull down 3 feet and the boulder lifts 6 inches. Viola!
The reason true outrunners are limited from high rpm is because the speed at which the armatures can be energized. Smaller motore can reach MUCH higher rpm than huge motors because of several reasons. One is the magnet to armature timing.
With a moderate size inrunner, the speed at which the magnets are moving past the armature coils at 10k rpm is... Lets say 50mph for an example. Lets say at 50mph the armature is energized perfectly as the magnet passes, and you get optimal power.
With an equivalent outrunner (lets say twice the armature diameter as an example) the same 10k rpm will mean the magnets are flying past the armature at 100mph! That's no good, way too fast. Slow the outrunner down to 5k rpm and the magents are now moving 50mph past the armature. Now we have the same timing, but the lever arm is now longer because the magnets have to travel a farther distance to achieve half the rpm of the inrunner. I believe an outrunner will typically have more poles, meaning more points of armature energization because the magnets are covering more distance, so you have more room for armature windings. This is the reason outrunners are considered to run so smoothly. This extra distance gives you more torque, just like 1st gear in your gar compared to 4th gear. Same power, but different output speed and different output torque.
im no motor expert yet but it seems the outrunner would run cooler because of its exposed external rotation
Brushless inrunners typically run more efficiently and can cool themselves better because the armature (winding) is against the wall of the can which acts as a heatsink.
Many people think outrunners are a godsend, not really. They are just a simpler way to get the same work done. They usually aren't as efficient, but they are lighter because there's no need for a gearbox. This functional simplicity and lighter weight make them the choice for most small-mid sized electric airplane pilots who are willing to lose a few % efficiency for the benefit of light weight and quiet, simple operation. Many people think inrunners with a proper gearbox are more efficient. They'd be right, however there's more parts to break. It's a tradeoff.
Wow that was way more than I wanted to type... If any of that doesn't make sense let me know and I'll try ti straighten it out...