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Motor size question.

MrGravey

Senior Member
#1
Take this motor as an example:

http://www.hobbyking.com/hobbyking/...Brushless_Outrunner_Motor_USA_Warehouse_.html

3530/14 is the listed size for this motor. I understand what they mean, what I don't understand is what changing those numbers changes. I'll clear that up a bit. If, instead of that motor, we took one that was 4042/14 what would be different about the performance of that motor? I get that these numbers denote the size of different parts of the motor. What does changing the size of those parts change about the motor?

Thanks for keeping up with my rambles to this point. You guys have helped a mortal ton already, hang with me a little longer and maybe I wont be asking 4 questions a day in a little while.
 

pgerts

Old age member
Mentor
#2
What is really interesting in the numers 35 30 14?
Diameter Length number of windings of the copper thread inside the motor ..............
OK diameter and lengt might perhaps be interesting if i want to put the motor in a nose of a glider or scale model.
For me the interesting numbers are
300W
34A
1150 KV
The power tells me the size of the plane i can use withthe motor.
The max current tells med the required size of speed controller and battery needed.
The revs tells med size of propeller (hight from wheels to motor) and final speed of the plane (only if its slowflyer or fast racer).
 

MrGravey

Senior Member
#3
Ok, so the numbers are just a size thing then?

How do you figure out how much weight the motor will be happy to carry? I understand more power is more weight lifted, but how much power per unit of weight?
 

pgerts

Old age member
Mentor
#4
The power / plane weight depends a lot of the type of plane.
100W /lbs 200W/kg total weight is about the limit for hovering a plane.
A scale "CUB" type requires less than 25% of that. The old original cub had about 40 kW power.

The weight of the motor corresponds normally to the power of the motor.
20-25 grams - about 80 W
50 grams - about 150 W
 

MrGravey

Senior Member
#5
The power / plane weight depends a lot of the type of plane.
100W /lbs 200W/kg total weight is about the limit for hovering a plane.
A scale "CUB" type requires less than 25% of that. The old original cub had about 40 kW power.

The weight of the motor corresponds normally to the power of the motor.
20-25 grams - about 80 W
50 grams - about 150 W
That thread has answered my questions perfectly. I now understand this a ton better. I have been around forums for a good while and I don't know that I have ever gotten more out of a thread so quickly. Thanks you guys a bunch.
 

robschonk

Senior Member
#6
A really great source of motor info is on this site:

http://www.headsuphobby.com/

Be sure to read his FAQ and guide.

For each motor, he lists the types of planes suitable and recommended props.

First class dealer with great service. If in doubt, call and discuss your needs.
 
#7
3530 , 4042 etc etc
These are meaningless, as some manufacturers have widely different model numbers for similar motors
Its as if they pull that number out of a hat :)
Also, power & max amps are often over-rated. Expect to use a smaller prop size than recommended by manufacturer. You can always use a bigger prop later if you dont have any overheating issues.

The thing I allways now consider is : ARE SPARE SHAFTS AVAILABLE
I have a box full of HKing motors with bent shafts with no replacement shaft available . Some of the orange turnigy motors have shafts about as strong as butter.
:D