Brushless Motors and ESCs

You can use any model aircraft equipped with a camera to measure distances on the ground. This is great for hobbyists interested in making their own maps, or if you’re just curious what the distance between two far apart objects is. With a little trigonometry (a gasp is heard throughout the room), all you need is to measure one angle and one distance. I’ll walk you through the math, it’s not actually that hard, and the end result is more than worth it.

What You Need

To do this project, you’re going to need a few materials:

• An RC helicopter, or RC airplane with 3 channel control or better – You’re going to need a stable platform to take pictures from. Helicopters are useful because you can hover in one position, but airplanes are cheaper. You might already have an airplane or helicopter around, but if you don’t, the Multiplex Easystar works well for this project. Note that to make a remote shutter function, more than 3 channels are needed.
• A lightweight camera, with remote shutter operation – You need to be able to remotely trigger the camera. This can be done a number of ways, but the simplest and most economical is to attach a servo to the top of your camera with rubber bands. Make it so that when you throw a spare channel switch on your transmitter, the servo arm will move and press down the shutter switch. As with any mod, feel free to create your own solution.
• A large protractor
• Some string and a weight – Clay works well as a weight, I’ll explain why you need it shortly.
• A drinking straw – You’re going to need this to build a sight for the protractor.
• Measuring Tape – You need to know the altitude of your aircraft, and to do this, you need to measure it’s distance from you. Landmarks with a known distance can also be used – consult any street map with a scale for these.
• A notebook / paper / pencil
• A friend to help – You can’t fly your aircraft and make measurements at the same time. Take a friend along to help you, and ask them to record the measurements.

The Math Involved

Now we come to the hard part – a little bit of math. You don’t really need to understand all these derivations, feel free to simply use the formula that I’ll give you. The problem is this: given an aerial picture, how can we figure out the scale?

We need the altitude of the airplane to figure out the image scale. This can’t be done directly, so we measure the angle (a), the distance (d), and use them to compute the height (h). This is a right triangle, and there are some handy trig functions that apply. In this case, we use the tangent function, which gives the ratio of the opposite and adjacent sides.  This is expressed as follows:

By taking the tangent of the angle a, and multiplying by the distance (d), we get the height (h). Here’s the formula that you would use:

So how do you get the angle? It’s simple: take the protractor and tape a piece of drinking straw to the flat bottom. Then attach a piece of sting to the bottom center of the protractor, so that it dangles straight down the 90 degree mark. Use the ball of clay to make a weight at the bottom of the string. Now, when you tilt the  protractor, the string will measure the angle. Be careful though: the angle with respect to the ground is not what’s read directly off the protractor scale. Reading the difference between the indicated angle and 90 degrees will give you the angle you need.

So why do we care about the altitude? Well, it turns out that the ratio of the altitude and the focal length of the camera is the image scale! You can find out the focal length of your camera by reading it’s manual. This is usually expressed in millimetres, so convert it to whatever  unit you have used to measured the distance, and thus the altitude in. Let’s put that all in a convenient formula:

And that’s the only formula you need. Just measure the distance, and the angle, know the focal length, and you’re done.

How to Do the Measurements

All that math was fun, but how do you actually measure distances using this method? I’ll illustrate with an example:

Suppose that you’ve just gone out to a field, and want to measure the distance between a tree and a building. The first step is to find a landmark you can fly over with a known distance. Using a measuring tape or map, you find that a nearby hill is 50 feet from where you’re standing. With a friend ready to measure and write down the angle, you launch your airplane and fly over the nearby hill, taking several pictures. Your friend sights the model aircraft through the protractor – straw device built earlier, and finds the angle to be 75 degrees.

Using a calculator, you find the altitude to be:

After landing, you download the pictures and print them full size, with no scaling. Your camera’s user manual reports that the focal length is 152 mm (millimeters). Converting this to feet is easy, just type it in Google or multiply by the number of feet per millimetre. 152 mm is 0.48 feet, so you plug that into the formula we derived earlier and obtain the following:

This means that distance measured on the picture is 0.000257 times as big as the real distance. You’re almost done: using a ruler, you measure the distance between the tree and building on the image to be 1 inch. Converting this to feet (because we want the distance between the building and tree in feet), gives a distance of 0.0833 feet. Now, multiplying this by 1 divided by the picture scale gives a final answer of 324 feet.

And that’s it – you’ve just measured the distance between two objects using nothing more than a RC aircraft, camera, and a little trigonometry. Just keep in mind that you have to know the distance between the airplane and you accurately for this to work – always take pictures right on top of the marker with a known distance.

© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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Brushless motors have almost completely replaced brushed motors. Their superior power and efficiency make them the obvious choice for powering your RC equipment.  Here’s what you need to know to use them, and some helpful info on how they work.

Brushless Motor Benefits

Before going into how brushless motors work, here’s why they’re useful:

• More Efficient – Brushless motors are much more efficient than conventional brushed motors. This efficiency has been measured to be between 85% to 95% better than brushed motors.
• Less electrical energy is wasted as heat,and more is used to do useful work.
• Reduced Noise – Brushless motors have fewer mechanical parts than brushed motors, so they emit less sound.
• Longer Lifetime – Fewer moving parts are in mechanical contact than in brushed motors, reducing wear.
• Reduced EM Interference – Brushless motors emit less energy as electromagnetic (EM) waves than brushed motors do. This contributes to their efficiency, and helps reduce radio interference.
• Torque, Voltage, And RPM Linearly Related – This means that the amount of torque or RPM produced by the motor divided by the voltage put in is a constant, making it easy to predict how much power you’re going to get.

How Brushless Motors Work

On a fundamental level, an electric motor’s only job is to convert electrical energy (like that provided by a battery) into mechanical energy, like the turning of a propeller or rotor blade. There are two basic facts that allow electric motors to work:

1. Electric and Magnetic Fields are Related - That is, every moving charge produces a magnetic field, and magnetic fields can produce electric charge.
2. Magnets Interact – Magnets will align when placed near to each other. All electric motors basically consist of two magnets. One of them is permanent, the other is a coil of wire that, when charged, becomes a magnet.

The motor is designed such that the magnetic fields produced by each of the magnets are always out of alignment, causing the motor axil to rotate. This is similar to what happens when you hold a permanent magnet to a compass – the compass swings position so that it lines up with the magnets field.

With the brushed motor design, the magnetic fields are kept out of alignment by turning on the different coils of wire that surround the motor axil in succession. Metal brushes make mechanical contact with the rotating axil and the contacts with each metal coil. As the axil rotates, the brushes contact different coils. The end result is that current flows through different coils at different times, constantly changing the magnetic field and rotating the motor shaft.

It’s here that we see the main problem with the brushed design: the contact between the motor coils and the brushes causes friction, which increases with speed. The metal coils wear out over time, and are prone to sparking. They can also ionize surrounding air, creating ozone. So how can we get around these issues? The answer lies in the brushless motor design. Instead of using mechanical brushes to turn on the various wire coils, an ESC (electronic speed controller) is used instead. The ESC switches the motor coils on or off rapidly, and is synchronized to the motor axil position.

Always look for an ESC with a capacity (measured in amps) greater than that of the motor you’re pairing it with.

Some Common Terms Explained

There are a number of special terms associated with brushless motors. Here are explanations for some of the most common:

• RPM – This is a measure of angular speed, or how fast something is rotating. A motor’s RPM is simply how fast it can rotate.
• KV Rating - Remember how we said that the relationship between voltage, torque, and RPM was linear for a brushless motor? It turns out that the number of RPM provided by each volt is the same, called  the KV number. The KV number’s useful because it let’s you figure  out how many volts you need to achieve a certain RPM, or vice versa.  For an example, a 980 KV motor powered by an 11.1 volt battery would  spin at 980 x 11.1 = 10878 RPM with no load. The KV rating always  assumes no load on the motor, so the actual RPM that your achieve  will be less than the one you calculate.
• Continuous / Burst Current – Continuous current measures how much current a motor can handle continuously, for an extended period of  time. Burst current measures how much current a motor can handle for a short amount of time, about a few seconds.
• Current Rating – This is the maximum current that a given motor can handle, measured in amps.
• Inrunner / Outrunner – These are the two major brushless motor  designs. An inrunner brushless motor has stationary coils, and a   rotating permanent magnet inside the coils on the motor shaft. An outrunner  brushless motor is the opposite, it has a rotating permanent   magnet, placed outside the stationary coils on the motor shaft . Outrunner motors have lower KV ratings, so they run at a lower speed with more torque. This could allow you to direct drive larger props without a gearbox. RC cars and boats tend to require inrunner brushless motors, rather than outrunners.
• Torque - Torque is a measure of angular force, or how much “push” a rotating shaft has.  Watt – This is a measure of power, or how fast energy is used.
• Volt – This measures electric potential, or how much “push” the electrons from a battery have. A greater voltage means that more   energy is being applied to a given amount of charge.

Choosing a Brushless Motor

Most airplane manufacturers will recommend certain brushless motors for different models. However, if this is not specified, a good starting point would be to check what other people are using locally,or search the web. We frequently visit RCGroups, RC Universe, and WattFlyer to see what the RC communities are using. If you have a brushed motor that you are replacing, choose a brushless motor that is the same physical size, and uses about the same wattage. To determine the wattage, multiply the current your old motor draws by the voltage it’s run at.

© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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Hacker has recently revised the design of their popular A20 series of brushless electric motors. The new Evo series features several interesting modifications, listed here:

• Revised Can Design – Hacker has revised the motor’s external case to allow for better airflow and cooling towards the back of the motor.
• New Stater and Magnet Material – Hacker has re formulated the material used for the stater and magnets in their brushless motors. The new material has a lower internal resistance, which gives the motors more power and efficiency.
• Collet Style Adapter – The new evo motors use a new style of prop adapter, which is more secure and easier to use than the previous versions. The new adapter also allows the motos to be more easily mounted either in front or behind an RC model airplane firewall.
• New Mount – All of the A20 series motors now feature a new type of mount which allows the new can design to work.

All of the Hacker A20 brushless motors except the A20XL incorporate this new design, including the A20, A20S, A20M, and A20L.

All of the A20 brushless motors we sell will be revised to this new design, so why not get one for your electric RC model airplane today?

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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The Multiplex Minimag is a durable foam RC model airplane. It has a 4 channel proportional radio system, and a brushed motor / NiMh battery power system. Many users of the Mulitplex Minimag add brushless motors and lithium polymer batteries for increased flight performance. This article will show you how to do these modifications yourself.

The RC Components You Will Need

We have put together a list of the best RC components to use for modifying the Minimag RC model airplane. You will need:

1. A Brushless Motor – A Himax 2815-2000 works well for this application.
2. A Speed Controller – Use a Castle Creations Thunderbird 36 amp ESC. It will provide plenty of power for the recommended motor, and will run off a variety of lithium polymer batteries.
3. A Lithium Polymer Battery – A Thunderpower 3 cell 2100 is a great battery to use. You can get up to a half an hour of flight time (depending on throttle management), and it fits neatly underneath the Minimag’s wing.
4. A Propeller – The brushless motor will need a different propeller. We recommend a 7 x 5 APC propeller.
5. A Charger – You can use either a Thunderpower 535C or a 610C charger. Each will allow you to quickly charge your battery at the flying field using a 12 volt power source.

Eventually we will sell all of these components in a kit. Until then, you can order them by clicking on the above links and pictures.

RC Components Installation Procedure

Many of these components will seamlessly drop in to the Minimag RC airplane where the original parts were. Follow this procedure when installing your improved power systems.

1. Remove the brushed motor, and install the brushless version. Be very careful not to damage the motor wires. All of the bolt holes from the old motor should match the new one perfectly, so just push in the brushless motor and bolt it on.
2. The 3 cell 2100 lithium polymer battery can be placed under the wing. Make sure that it doesn’t move in flight, and route its wires to where the electronic speed controller will be installed.
3. Connect the speed controller to the motor, battery, and receiver.

We hope that you enjoy the increase in power and flight time that this upgraded power system will give you. Feel free to post comments describing your own ideas, and let us know how this modification works for you.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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The Multiplex Easystar is a 3 channel, powered RC glider. The multiplex Easystar comes with a great set of equipment, including a 400 size motor, NiMh rechargeable battery and a proportional radio system. It has become very popular among RC aerial and UAV enthusiasts, because it is very easy to modify.

One of the coolest modifications involves replacing the included brushed motor with a brushless motor, and replacing the NiMh battery with a lithium polymer pack. Using a brushless motor will increase the speed of the Easystar, and let you carry payloads (such as cameras for aerial photography.) The lithium polymer battery will let you fly for up to a half an hour, or even longer if you can catch some thermals (warm, upward currents of air.)

Parts You Will Need to Modify the Easystar

There are several different combinations of brushless motors, ESCs, and lithium batteries that will work for this modification. Here is a list of the parts that we recommend. They have been chosen to minimize cost, and maximize performance. You will need:

1. A Himax 2815 2000 brushless inrunner electric motor
2. A 35 amp Castle Creations Thunderbird ESC
3. A 6 x 4 APC composite propeller
4. A Thunder Power 3 cell 2100 lithium polymer battery
5. A Lithium polymer battery charger. We recommend either a Thunderpower 535C or a 610C. Both of these chargers can use a 12 volt battery, or a 12 volt AC adapter. Suitable AC adapters are available on our website.

We will eventually offer these components in a set, but for now you can order them individually by clicking the links or pictures above.

Procedure for Modifying the Easystar

One of the great features of the Easystar is that it is easy to modify. Every component that we mentioned should fit perfectly, and the foam the Easystar is made of is superglue safe.

Follow these guidelines when installing your new hardware in the Easystar.

Motor – Remove the brushed motor by unbolting it. The bolt holes will match the new brushless motor, so simply insert it and bolt it in. Be extremely careful to not damage the motor wires when doing this. Feed them through the fuselage to where they will connect to the ESC.

ESC – Place the ESC in the fuselage, and then connect it to the brushless motor using the wires. It’s always a good idea to tape over the connection, so that it won’t accidentally disconnect in flight. Also connect the ESC to the Easy star’s receiver.

Battery – Use Velcro to secure the battery in the fuselage. Then connect the battery leads to the ESC.

Rudder – Because of the huge increase in power that the brushless motor provides, you might want to increase the effectiveness of the rudder. You can do this by simply gluing a business card to the rudder, and then trimming it to shape. Here is a picture of one such modification:

Benefits of Using a Brushless Motor and Lipo Battery for the Easystar

• Using a lithium polymer battery will allow you to fly the Easy star for very long periods of time.
• Lithium polymer batteries can be charged quickly and easily at the flying field.
• The brushless motor will provide much more power than the regular speed 400, and will last longer too.
• The increase in power from the brushless motor will allow you to carry payloads, such as a digital camera for RC aerial photography.
• The aircraft will perform better in all aspects of flight, giving you a more enjoyable flying experience.

This article has barely scratched the surface of the possible modifications to the Easystar. If you would like to learn more about these modifications, or learn how to do others, we suggest you read the rcgroups.com forums.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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The Hacker A20 Series brushless motors are the latest design using outrunner technology. Hacker A20’s are specifically engineered for high power and maximum efficiency using proprietary Hacker Brushless components of the finest quality. Hacker A20 brushless motors come in 4 types: Hacker A20-S, Hacker A20-M, Hacker A20-L, and Hacker A20-XL.

Hacker A20 Series Brushless Motors Feature

• Outrunner motor design uses no gearbox for lower weight
• Five to Seven times more torque than direct drive inrunners
• High torque means large propellers for greater thrust
• Rotating can/endbell provides excellent cooling
• Great cooling means very long flight times with Lithium Polymer cells
• Versatile mounting options for front or back mounting

Hacker A20-S Brushless Motors for RC Airplanes – Use With 2 Cell LiPo

Hacker A20-S brushless motors are developed for 4-8 oz. indoor slowflyers and indoor aerobatic r/c airplane models with 2 cell LiPoly batteries. The 12 pole “outrunner” type design creates a massive amount of torque, allowing larger direct drive propellers to be used without the need for a gearbox. Hacker A20-S motors feature oversize bearings, curved neo-magnets, and High efficiency stator design. These Hacker A-20-S motors produce the most power at lower current consumption than other popular outrunner designs! The Hacker A20-S brushless motors use a standard 3mm (0.118 in) output shaft.

Hacker A20-M Brushless Motors for RC Airplanes – Use With 3 Cell LiPo

Hacker A20-M series brushless motors are developed for 7-12 oz. slowflyers and aerobatic parkflyer model rc aircraft with 3 cell LiPoly batteries. The 12 pole “outrunner” type design creates a huge amount of torque, therefore larger direct drive props can be used without the need for a gearbox. These Hacker A20-M brushless motors features oversize bearings, curved neo-magnets, and high efficiency stator design. Hacker A20-M brushless motors produce the most power at lower current consumption than other popular outrunner designs. The Hacker A20-M brushless motors use a standard 3mm (0.118 in) output shaft.

Hacker A20-L Brushless Motors for RC Airplanes – Use With 3 Cell LiPo

Hacker A20-L brushless motors are developed for 12-18 oz. parkflyer rc aircraft models with 3 cell Lithium polymer batteries. The 12 pole “outrunner” type design creates a huge amount of torque, therefore larger direct drive props can be used without the need for a gearbox. This Hacker A20-L brushless motor features oversize bearings, curved Neo-magnets, and high efficiency stator design. Hacker A20-L brushless motors produce the most power at lower current consumption than other popular outrunner design. The Hacker A20-L brushless motors use a standard 3mm (0.118 in) output shaft.

Hacker A20-XL Brushless Motors for RC Helicopters – Use With 2 or 3 Cell LiPo

Hacker A20-XL brushless motors are developed for mini and micro sized electric rc helicopters. The 10 pole “outrunner” type design creates a massive amount of torque. This Hacker A20-XL brushless motor features a cooling fan, oversize bearings, curved neo-magnets, and high efficiency stator design. Hacker A20-XL brushless motors produce the most power at lower current consumption than other popular outrunner designs. The Hacker A20-L brushless motors use a standard 3mm (0.118 in) output shaft.

Hacker A20 Brushless Motor Applications

See our related article: Hacker A20 and A30 Electric Brushless Motor Applications

Where To Purchase Hacker A20 Brushless Motors

Draganfly Innovations Inc. sells a huge selection of Hacker brushless motors and Hacker brushles motor parts & accessories. They also sell Hacker brushless speed controllers, APC electric rc airplane propellers, Thunder Power RC Lithium Polymer Batteries, Voltage Regulators, Castle Creations Berg receivers, and RC Servos. Get all you need to power your electric RC airplane online or order by phone: 1-800-979-9794 / 306-955-9907.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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Hacker Opto Pro ESCs Require Their Own Battery

The Opto Pro series of brushless speed controllers by Hacker Brushless are a little different because they not have a Battery Eliminator Circuit (BEC) built in. The two Hacker Opto Pro ESCs we sell are the Hacker X-40 Opto Pro and the Hacker X-70 Opto Pro. This means the Hacker Opto Pro ESCs will only provide power to the brushless motor and will also not provide power to your radio receiver and servos. To power your receiver and servos you will need a dedicated receiver & servo battery pack. We recommend a Thunder Power Receiver Pack LiPoly Battery coupled with a 5.1V Voltage Regulator. When you do not have a second battery for the receiver the Hacker Opto Pro speed control will not function, will not beep and you will not notice any lights.

Properly Connecting a Hacker Opto Pro ESC

To properly install and connect a Hacker Opto Pro brushless speed control first connect it to the brushless motor and then connect it to the main flight battery. We recommend Thunder Power LiPoly batteries. The receiver lead coming from the Hacker Opto Pro ESC will connect to the throttle channel on the receiver. The servos will also connect to the receiver as usual. To power the receiver and servos connect a receiver pack battery to either the battery terminal or any open terminal on your radio receiver (RX). Once the entire system is connected properly with one battery for the receiver & servos and the other battery for the ESC and brushless motor the Hacker Opto Pro speed control will function normally.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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