Looking at motors on hobbyking.
I'm wondering if this is too much motor for a 1/2A.
Turngiy 2836 3200kv at 7g this is about 2.5 ounces ?
Weight being a bad way to determine size but the second question I have is more alone the lines of apples to oranges. When you put a smaller prop on the rpm goes up but the amperage does too ,or so it seems.
So other than trial and error how do you know what a motor will do on smaller props ?


Dimension: 28mm x 38mm, 53mm(with shaft)
Weight: 72g  (kv3200) (not including connectors)
Diameter of shaft:�F3.17mm
Length of front shaft:�F14mm
Lamination thickness: .2mm
Magnet type: 45SH

Max performance;
Voltage: 3-5S
Prop: 70mm EDF (3~5 Blade)
Power: 650W
For 70 size EDF

Looking at motors on hobbyking.
I'm wondering if this is too much motor for a 1/2A.
Turngiy 2836 3200kv at 7g this is about 2.5 ounces ?

1 oz = 28oz, more or less.  Looking down, you mean 72g, or yes, about 2.5oz.

Weight being a bad way to determine size but the second question I have is more alone the lines of apples to oranges. When you put a smaller prop on the rpm goes up but the amperage does too ,or so it seems.

Permanent-magnet motors like these "want" to go at a constant speed when you drive them with a constant voltage.  Put no prop at all on them and they'll go as fast as they can -- their "unloaded" speed.  Hold on to their shaft with a Vice Grip and they won't turn, but (assuming you're putting full voltage on them, and until they burn up) they'll consume lots of current.

Smaller props are more like the "nothing at all" case, and will cause the motor to go faster than larger props, and to draw less current.

With a 'helicopter' ESC, the ESC regulates the motor speed, and just keeps pouring on the coals as necessary to keep the speed up.  In this case, as long as the batteries and motor have enough oomph the prop will spin at a constant rate -- but big props will need more energy, for which the motor will draw more current.

So other than trial and error how do you know what a motor will do on smaller props ?

You start with the manufacturer's recommended prop for the number of cells you're using, and you try various combinations.  Or better, you look at the "List your setup" thread in this forum, you find a plane with a similar weight, select yourself a motor with a similar Kv, use the same number of cells, and start with the same prop.

Dimension: 28mm x 38mm, 53mm(with shaft)
Weight: 72g  (kv3200) (not including connectors)
Diameter of shaft:�F3.17mm
Length of front shaft:�F14mm
Lamination thickness: .2mm
Magnet type: 45SH

Max performance;
Voltage: 3-5S
Prop: 70mm EDF (3~5 Blade)
Power: 650W
For 70 size EDF

Look at the power rating: 650W is enough for a 50oz model.  You want to look for a much smaller motor.

Have you said what your target all-up weight is?  With electrics, just about everything else you do flows from this.  Unless you're building a plane that's extremely draggy, or has an extremely high or low aspect ratio, then just about all of your choices boil down to deciding how much the plane is going to weigh when you're done, then multiplying that by a constant to find the motor and battery size.

Once you say how much you want it to weigh, tell us what models its most similar to in the "List your setup" thread, and how you think it's different.  There's a ton of information in that thread, all the way down to 1/2A.