Motors And the light starts to glow!

[murankar]

Please let me know if I got this right.

When choosing a motor one looks at things like the power (i.e. watts, amps and volts), the size and the Kv rating of the motor. Until today I did not realize just what the Kv rating actually means. Yes the higher the rating the faster the speed of the motor. But wait there's more the higher the Kv the less torque you have. Depending on the application of said motor a high Kv value maybe desired.

So what about in helicopters. I noticed that most heli's are being built with a "standard" 3500 Kv with a 13T/14T pinion. Then one day last week I decided to look at the Protos line. A high end heli made with plastic parts, their birds are configured with a sub 3000 Kv motor and a 16T pinion. I found this strange and could not figure out why. Until today, more torque. Which I presume is ideal for 3D flight.


please let me know if this is close.

 

[Tony]

That is pretty much it. If you look at the specs on the motor, you will notice that the wattage is higher on the lower KV motors as well. The magnetic field is what creates the power, and the bigger the wires on the armature, the more power they can handle, and the more magnetic field they will put out.

 

[murankar]

I still have much to learn on this stuff. I am glad I am figuring it out as I go. Now I know I have to make a change at real soon on my config. At the same time I am victim of poor description. But I will at some point I will move to a 3000 kv motor range.

 

[murankar]

OK a question just jumped into my head. What does higher torque mean in regards to head speed? I know that the head speed determines the amount of lift you get. So even though I increase my torque i still want to maintain close to the same head speed.

 

[Tony]

You need a head speed of at least 2000 rpm. When you are first starting, you won't need the torque. 3d pilots need the torque when they are pumping that cyclic pos and neg all the time and changing direction in pitch.

 

[Lee]

As Tony says, with 3D moves you need high torque to keep the motor rpms up. When i do Tick tocks for example, after 3 or 4 the motor has slowed down too much and i need to pull out.

 

[murankar]

OK I think I am starting to see things again. So for helicopters head speeds need to be in between 2000-3000 rmps. The sweet spot is somewhere in the middle. The torque is what allows you to perform more "stunts" more frequently due to faster head speed recovery.

I am trying to learn this quickly I guess.

 

[Tony]

If you learn too fast, you won't retain any of it. Just work on what you need to know at the moment then go from there. Unless you can retain things better than I can lol.

 

[murankar]

the last two years of college have taught me to learn and retain fast. When I want to learn something I wrestle it to the ground and hog tie it. You should of seen me doing stats 100. Man that was some long nights trying to understand some tough stuff.

 

[Lee]

The headspeed depends on the size of the heli too. A 450 will have a way faster HS than a 700

 

[murankar]

I noticed that the motors used on bigger helis have lower Kv values. Since I solved the lower Kv equation I am thinking it is for the torque, which maybe needed to get the weight to move. So what would the average H.S. be for lets say a 500 or 700? Also does the blade size also compensate for lower H.S.?