Outrunner or inrunner

[gfm1135]

Why chose one over the other? Advantages disadvantages? Specific applications? Thanks!

[stifflkd]

I replaced a 4074 1400 Kv Turnigy 4 pole inrunner with a T600 1400Kv Turnigy out runner. They were close in weight and some what similar in size. The outrunner also cost about $12 more. I saw about a 3 to 4 mph increase with the outrunner, from 52 to 56. The biggest disadvantage of an outrunner is that they are difficult to cool. I use mine on a outboard, I do not think I would use one buttoned inside a hull but I think many do and have no problems.

[St3alth_Frenzy]

Out runners have more torque than a same sized in runner (the stator has a larger radius than and in runner) and they do run cooler when they can get not stale air (there like a big fan). In runners usually spin faster and are more efficient, but they do run hotter. It’s also easier to cool an in runner with water.

[stifflkd]

Two motors with the same Kv will have the same torque regardless of whether they are in or out. The larger stator radius will require less force (i.e. less turns) to generate that torque. However what it saves in coil resistance is offset by a higher no-load current due to the fact that a larger mass needs to spin. There are two parameters that determine efficiency, coil resistance and no-load current. My guess is the improvement in one is offset by the other.

Does a fan really work inside a sealed hull? It would think that it only pushes around the hot air already being generated by the batteries and ESC.

[St3alth_Frenzy]

thats what i meant by stale air (hot air, sealed hull, etc), the out runner can cool itself when it has good airflow inside the hull

[1945dave]

thats what i meant by stale air (hot air, sealed hull, etc), the out runner can cool itself when it has good airflow inside the hull

Well I suppose that is why you find outrunner motors in helicopters and generally inrunners inside sealed up boats.

[St3alth_Frenzy]

Also, dirt and outrunners dont mix, Dirt and rocks can get into them really easy. Inrunners usally dont have to worry about this because they have a sealed can.

[gfm1135]

Thanks for the responses. What prompted the question was i noticed Fightercat Racing sells primarly outrunner motors for their FE

[viper1]

Besides the difference in cooling capabilities, you could compare them remotely with the difference between combustion engines,
Consider the Inrunner a 2-stroke engine, higher revving, good for racing, less torque,
and the Outrunner a 4-stroke, more efficient, higher torque, but less peak power.

Not an ideal comparison i admit, but makes it easy to understand.

[kievyu]

inrunner good for high rpm application & outrunner have light weight 、more torque