Motor Size Definitions?

[JeromeF]

I'm buying some bits for a Depron plane and need some help with motor size definitions.

The kit says '400 Size B/L Motor'.

How do I relate '400 Size' to the physical dimensions of a motor?


The motor I've found which looks to fit - Dimensions: 27.6 x 11.5mm and 19g.

[Smoothound]

That sounds small for 400 size. I think they are normally around 25mm by 30mm

[Pipistrelli]

Jerome,

Its hard to relate brushed motor sizes across to brushless. Brushed motors usually relate to can sizes and even then motor performance can vary wildly.

You need to balance the airframe, so try and find out the weight of a 400 class motor and get towards that weight, it will help with CofG issues. I know from experience that a 300 motor is approx 45grams, so you need to be in that region or slightly larger, unless you can balance CofG with a bigger Lipo?

The other thing to think about is Kv rating, do you want to run a large prop (3D), so low Kv, or a small prop (speed) high Kv, or somewhere in the middle?

Hope this helps?

[JeromeF]

You need to balance the airframe, so try and find out the weight of a 400 class motor and get towards that weight, it will help with CofG issues. I know from experience that a 300 motor is approx 45grams, so you need to be in that region or slightly larger, unless you can balance CofG with a bigger Lipo?

I don't have the plane to hand but it will be Depron and the model appears to be able to have the lipo mounted in several places so CoG shouldn't be an issue.

Brought a 1450kv motor @ 49g which is in the same size region as Smoothhound mentioned.

The other thing to think about is Kv rating, do you want to run a large prop (3D), so low Kv, or a small prop (speed) high Kv, or somewhere in the middle?

Hope this helps?

I'm buying cheap motors like the one for my Formosa, RC Timer, from HK so I will get a selection of winds as I'm unsure what type of flying I want to be achiving. I'm really new to the Fixed Wing stuff - all a new learning experience! I have got my head around a calculator, sort of, to work out prop sizes for more thrust/speed etc but won't be sure what I want until it's in the air

Great help, thanks!