Question about motor

T

troyc794

Member
I am planning on building a HK predator 650.
http://www.hobbyking.com/hobbyking/...ng_Quad_Copter_Carbon_Fiber_Version_Kit_.html
I have been doing a ton of research on what motor to buy and I came across the Turnigy L3010B as my top choice.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=42693
This seems to be a relatively new motor and no data sheet to speak of other than the size. Would this be a good motor for a quad application? It says that its capable of generating 1650g of thrust but it doesn't say what the set up is. This will be my first build, but I want it to be capable of carrying a payload and have a lot of power and be capable of a decent flight time. I would rather just build a good quad now and not have to upgrade later.
Input is very much appreciated.
 
That motor was one of the contenders that I was looking at. The motor I asked about does fall into the recommended sizes, but its 1300kv and I wasnt sure if that would be an issue for the size i am after. I just don't want to have to upgrade the motor because its under powered.
 
The size isn't really where you should be concerned as far as performance goes. Plus there are usually adapters for different sized motors and a lot of the bolt patterns are the same anyway. Although, if there is a size recommendation, I'd abide by it to be safe. The kV rating is the the most important factor in choosing a motor. Most pancake or shorter/wider motors are more efficient and have lower kV numbers than their can style counterparts, but in the end, kV is kV regardless of the motor housing/design.

There is a HUGE difference between a 750kV and 1300kV motor. With lower kV motors and 4S batteries or better, you're going to be able to spin bigger props (10-12 inch). The motors will turn slower per volt applied, but the power will be smoother and you'll get more torque. With the frame size you're looking at, I'd definitely go low kV, bigger props. Once you choose a motor, Hobbyking often has prop data and whatnot, which should get you the rest of the way to a good decision on your power system. **I just went back and looked at the frame and it's recommending 11-12 inch props and 4S batteries, which means you definitely need to stay around 750-850kV with the motors.

There are other things to consider, like number of poles, build quality, etc., but those aren't as important and generally if the kV is right, you're good.

If you run higher kV motors, you'll turn smaller props faster, which would be fine for a smaller frame (more agility, responsiveness, and whatnot), but won't be as good for your big frame. From personal experience, I once went from a 450 to a 500 frame that had a lot more payload on it and initially ran 1200kV motors with 3S batteries from the first build. It flew okay, but it wasn't the best and the power system was really struggling. After putting lower kV motors, 4S battery, and bigger props, it flew like a dream. It was extremely stable and much easier to control.

The last motor you sent looks like it would be perfect.
 
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Wow. Thanks for that reply.
I will stick with a 750-850 KV motor since I am planning on the 12" props.
One thing that is throwing me off is my background is electronics and they are using things like KV for rpm/volt when that means kilovolt to me.
Also is the power rating simply what the motor can handle for voltage input and current?
 
Yeah, it's confusing. Also, the motor size numbers in the motor names mean different things between manufacturers sometimes. Some Hobbyking motor naming conventions refer to the outside diameter and length (height) of the motor or don't make sense at all. A lot of other manufacturers numbers refer to the diameter and length of the stator. The last motor you sent the link to doesn't make a lot of sense based on the numbering of the motor, so it's always best to look at the spec sheet.

BrushlessMotors7.jpg


Good info on brushless motors:

http://www.rcuniverse.com/magazine/article_display.cfm?article_id=1344

As for your other question, the power ratings are just what you think. Max amps and volts you can apply safely (without the motor potentially burning up). The watt rating is max amps multiplied by max volts and that's really just the max power you can put out with that motor safely. In the last motor you sent, the rated watts says 444 watts at 18.5 volts, but that's a mistake. They mean 14.8 (4 cell battery).

It's always good to size your ESC a bit higher than your motor, which is why 35A ESCs are recommended.
 
Great! Thanks again for the input.
I was confused (yet again) when it stated 444 watts @ 18.5 volts, but the motor was rated for 4s.
I think I have decided on a set up
For the motor...
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=39038
The reasoning is it has a larger shaft @6mm vs 4mm and they are a turnigy motor vs a no brand Chinese one.
For the ESC...
http://www.hobbyking.com/hobbyking/...Amp_Multi_rotor_Brushless_ESC_2_4S_OPTO_.html
Seems to be a good ESC and I get a discount on it with the motor.
The flight controller
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=39478

Now I just need the frame to come in stock so I can get this thing off the ground so to speak.
 
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