Best Quadcopter Motors : Choosing RC Quadcopter or Multicopter Motors Made Easy …
Choosing the best quadcopter motors is critical if you are serious about performance. Without the right motors, nothing else will maatter much. Your drone will simply not perform as it should. You might try rewiring, using a different set of blades, replacing the controller board or maybe even tinker with the frame. If your motor selection for your quadcopter is not right, your multicopter will not perform well. Motors have a huge impact on how the craft performs – perhaps a lot more than any other part or accessory.
Another reason why you will want to be careful in selecting the right motors for your quad is the cost. Motors can be pretty expensive – especially the brushless ones. Some of the specifications listed may sound complex – but don’t worry. This page will explain all of the complex sounding stuff and make the task of choosing the right motors easy and fun!
Here’s a list of features you would want to look for in motors for your quadcopter or multicopter …
Clockwise and Anticlockwise
It is best to choose motors that can rotate both clockwise and counter clockwise. Quadcopters have 4 motors – and for the highest stability, two of these rotate clockwise while the other two rotate counter clockwise. You can buy motors that are either clockwise or anti clockwise only, but that would make the craft a lot harder to fly. Sure, there are algorithms that can take care of the resulting instability for you, but these would be really hard to keep in the air if you are relatively inexperienced and choose to fly in the manual mode.How Many Poles?
You would need to have some understanding of what pole count of a motor is, but you would not want to fuss about this. While a motor’s pole count does make a difference, you do not have to worry too much about it because all of the intricacies are handled by the electronics.A motor with a higher pole count requires more voltage and produces more torque – or lift. But it also will have a lower rpm or revolutions per minute. You will want to use larger blades with these motors.
A motor with a lower pole count has more rpm and requires less voltage, but the corresponding output torque – or lifting power – is also lower. The propeller blades also have to be correspondingly smaller as well. These motors will not be able to handle larger propellers.
Quadcopters generally use higher pole count motors – outrunners – so that they can avoid using a gearbox. High pole count motors output a high torque – and this means a gearbox will not be necessary to increase the torque.
Kv value or RPM/volt :
This is a critical number you would need to pay attention to. As the number of poles in a electric motor increases, it’s Kv value – or RPM/volt – drops. You would want to note that Kv here does *not* mean kilo volt. Instead, it’s a constant that tells you the RPM of the motor when a potential difference of 1V is applied with no load whatsoever. The Kv value is critical when you want to calculate the load a motor will be able to carry.
Note : The notation is Kv and not kV. kV means kilo volt and is entirely different from Kv we are talking about here.
A motor with a 1000 Kv rating rotates at a speed of 1000 rpm when 1 volt is applied at no load. If it happens to be a 12V motor, then it will rotate at a speed of 12,000 rpm at 12 V under zero load.
Here’s another example : A 1000 Kv motor has a maximum rpm of 20,000 and is rated at 120 watt. The maximum voltage you will be able to apply to this motor will be 20000/1000 = 20 V. The amperes it draws will be 120/20 = 6 amps.
Another 4000 Kv motor has a maximum rpm of 40,000 and is rated at 120 watt. The maximum voltage you can apply will be 40000/4000 = 10 V. At maximum load, the maximum current this motor can draw will be = 120/10 = 12 amps.
You can see the second motor uses twice the current as the first one to output the same power, 120 W.
How does Kv value matter?
With a drop in Kv value, the torque produced by the motor increases. More torque means more acceleration, and more lifting power. Conversely, motors with higher Kv value produce less torque.For motors with higher Kv value, you will have to choose smaller propellers. With smaller propellers, you can achieve higher speeds, but efficiency will be lower.
On the other hand, motors with lower Kv value can handle larger propellers that can lift more weight, use less electrical current, are more stable – but have lower speeds.
If all of this sounds a bit confusing, this is what you will want to remember :
A higher pole count motor will have lower Kv value, can output more power and has less rpm. More power = larger propellers, more lift, higher acceleration.
A lower pole count motor will have higher Kv value, outputs less power, but has more rpm. Less power = smaller propellers, less lift and less acceleration, but higher speeds (because the RPM – revolutions per minute – is higher)
What pole count works best in your case? To answer that, you will have to do quite a bit of testing and see what works in your case.
Power to Weight Ratio :
You want to use a motor with a very good power to weight ratio. A motor with a power to weight ratio of 1 will be able to lift just its own weight – useless to be used for pretty much anything. On the other hand, a motor with a power to weight ratio of 5 will be able to lift five times its own weight.In general, you will want to use powerful but light motors.
Before you buy the motors, it will be essential that you calculate the lifting capacity of your drone. And you should choose the motors such that the quadcopter and the payload hovers at around 50% throttle. You should not choose motors that need to run at full power just to hover with the payload. That would mean the motors are getting pushed beyond their capacity and they most certainly will not last as long as they otherwise could. And that would also mean shorter flight times and less than satisfactory performance.
But you know what, doing those calculations is certainly not a walk in the park. More so if you are just starting out and do not yet have a sound understanding of all the factors that influence the performance of a quadcopter – and there are a lot many factors that need to be accounted for. Factors like the frame size, atmospheric pressure and temperature, diameter of your propellers, resistance of the battery, motor, controller and many more. If you do not take into account all of the factors while designing your drone, you will end up with less than desirable flight times and lifting ability.
Here’s one good way to understand how all of these influence your quad’c performance – play around with this excellent calculator and see what the key parameters will be at full throttle. Do this long enough and you will get an intuitive understanding of what your motor’s key parameters should be.
Thrust : As a rule of thumb, if you are designing a drone for longer flight times, the thrust should be 2 times total weight. But for aerobatics, thrust should be 3 to 4 times weight.
For long flight times : thrust = 2 x weight
For aerobatics : thrust = 4 x weight
Thrust also depends on the propellers you use. Larger propellers generate more thrust. A 12″ propeller generates significantly more thrust than a 10″ propeller.
If are really serious about calculating values like motor efficiency and thrust, you will want to take a look at this piece of software
Motor Type : Disc or Barrel ?
Brushless motors – the kind that’s recommended for use with quadcopters if you are really serious about performance – come in two types.1. Disc : Shaped like a disc, is lighter and generates a higher torque as it has a higher number of windings.
2. Barrel : Shaped like a barrel, is heavier and produces less torque.
But disc motors are also more expensive – which explains why they are not so commonly used.
In general, disc motors have more poles and lower Kv value. They can power larger propellers, consume less battery power, are more responsive, have reduced vibrations and noise – and are excellent for long, stable flights.
But disc motors can also be more expensive. Even small ones can cost $10 to $30 more than comparable sized barrel motors. And a quadcopter requires 4 such motors. Disc motors are really only for the professional hobbyists – like those who are into aerial photography or videography. These are generally not suited for folks just getting their feet wet and testing the waters.
Propeller Motor Combination :
This is perhaps the most important part of it all. Some people actually say you do not start by choosing the motors first and then suit it with a propeller – you do it the other way around. Choose the propellers you want to use, and then go about finding a motor that works well with it.Larger propellers generate more thrust, have higher acceleration and result in stable slights. Shorter ones have a lot of speed and are great for acrobatics.
To start with, you would need to decide what exactly you are designing the quad for …
If you are into acrobatics, you will need small propellers – under 8 inches.
But if you are into something like aerial real estate photography, your quadcopter will carry much heavier payloads like a gimbal mounted FPV camera and so you will need much larger propellers – more than 12 inches.
It’s really, really hard to design a quadcopter that does great acrobatics and carries a heavy, gimbal mounted camera
There are essentially two numbers you will have to pay attention to when choosing propellers – diameter and pitch.
Diameter : Larger diameter propellers generate more thrust, smaller diameter propellers generate less thrust.
Pitch : This is the distance traveled for a single complete revolution. Lower the pitch, more the torque. Lower pitch propellers also have a lot less turbulence, can carry heavier loads and result in lower power consumption and longer flight times. On the other hand, higher pitch propellers are generally used mainly for acrobatics and racing.
Ideally, you would want the pitch to be less than 5. If you use propellers with too high a pitch, your drone will start wobbling a lot and unless you are an experienced pilot, you can have trouble even controlling it.
Quadcopters are mostly designed to hover – and to achieve that, you will need propellers with smaller pitch.
In practice, it’s very hard to find specifications for the vast majority of RC motors on the market. You will be hard pressed to find torque curves for a motor of your choice and work out the math. It rarely works that way in the “real world”.
you should read some behind post to have best choice
No comments :
Post a Comment