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:
- Electric and Magnetic Fields are Related - That is, every moving charge produces a magnetic field, and magnetic fields can produce electric charge.
- 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.
The Blade MCX is a great RC helicopter, but a comprehensive guide on installing replacement parts seems hard to find. Here’s a list of all the parts that tend to break with crashes, and how to install replacements. Don’t feel bad about crashing your heli – even I’ve crashed a few times flying the blade MCX around the factory!
Replacing the Blade MCX RC Helicopter Flybar
The main flybar stabilizes the top rotor, and spins at a great speed. Because it’s built on top of the main rotors, it tends to fly off during a collision. Fortunately, it’s almost never damaged and most of the time can simply be snapped back into place. Should yours break for some reason, here’s how to install a replacement.
- Check the Flybar For Damage – There’s very little that can actually break on the flybar, but check it against this picture to be sure it isn’t actually damaged.
- Snap off The Flybar Linkage – You’ll find a small black linkage on the flybar (the plastic part, about 1 cm high, that dangles down freely), which connects to the top rotor blades. Snap it off gently, and place it somewhere where it won’t get lost.
- Lift off the Flybar – The flybar is held between a black plastic clevis (the plastic holder on top of the rotor shaft). Gently spread the clevis apart using your fingers, and lift the flybar out.
- Install the New Flybar - Slide the new flybars centre into the black plastic clevises between the top rotor blades. Line the plastic extrusions on the helicopter’s flybar up with the holes in the clevis and snap it into place. Do the same with the small linkage, snap it onto one of the plastic extrusions on the top rotor blades. It doesn’t matter which side of the top rotors you attach the linkage to.
Replacing the Blade MCX RC Helicopter Top Rotors
A severe crash can crack the top rotor blades. Repairing them with tape or glue isn’t a good idea, because it causes an imbalance that makes the helicopter hard to fly. Your best bet is to simply replace them – here’s how:
- Unscrew The Rotor Blades – Using a small Philips head screwdriver, remove the two small screws holding the top rotor blades. Be sure to set the screws where they won’t get lost or roll away.
- Remove The Rotor Blades – The top rotor blades lock into each other, gently pull them apart and remove them.
- Install the New Rotor Blades – At the top of the rotor shaft, you’ll see two black holes protruding outwards. Place each rotor blade (right side up) into the shaft, and snap them together. It is possible to put the rotor blades in upside down – don’t do this. Make them look the same as the bottom rotor blades.
- Re-install the Small Screws – Using a Philips head screwdriver, replace the two small screws that you removed earlier.
Replacing the Blade MCX RC Helicopter Landing Skid
The landing skid is one of the easiest Blade MCX parts to replace. It simply pulls off from the bottom of the helicopter fuselage. You don’t always have to replace a damaged landing skid, most of the time some thick or medium CA (super glue) can fix it perfectly.
- Remove the Rechargeable Battery – You’ll need to hold on to the battery mount to remove the skid.
- Remove the Skid – Grab the skid by the battery mount and pull it off gently.
- Replace the Skid – Install a new landing skid by pushing it’s two pegs (found near the battery mount) into the holes in the bottom of the fuselage. Be sure to do this gently – don’t damage the helicopter by using too much force.
Replacing the Blade MCX Inner Shaft
The inner shaft turns the top rotor blades. After a few crashes, the rotor head / hub where the flybar connects can become bent, or the inner shaft itself can snap. If you’re in a particularly bad crash and the inner shaft breaks, here’s what to do:
- Remove The Battery and Skid – The battery slides out, and the landing skid can be pulled off.
- Remove The Flybar – How to do this is mentioned above.
- Remove The Top Rotor Blades – This was also previously mentioned.
- Remove The Bottom Gear – On the bottom of the fuselage, you’ll find two white plastic gears. Remove the bottom one by loosening the screws on the silver washer glued to it. Don’t remove the little black screws completely because they are easy to loose. Just loosen them enough to let the bottom gear slide off. Then gently pull the bottom gear downwards and clear of the inner shaft.
- Pull Out The Old Inner Shaft – The inner shaft can now be slid out of the outer shaft by pulling it upwards.
- Insert the New Inner Shaft – Slide the new inner shaft into the hole on the top of the outer shaft – it should drop down easily.
- Replace The Bottom Gear – Slide the bottom gear onto the inner shaft so that it meshes nicely with the motor shaft gear. Tighten the small black screws that you loosened earlier.
- Re-Install All The Other Parts You Removed – Add the upper rotor blades, flybar, landing skid, and battery.
- Test it – Make sure that turning the upper rotor blades makes the lower white gear move. If it doesn’t, then the small black screws on the lower gear aren’t tightened sufficiently.
Replacing Blade MCX RC Helicopter Rubber Grommets On The Canopy
The Blade MCX canopy is held on with small black rubber grommets. These rubber grommets can sometimes fall off and get lost, but replacing them is easy – here’s how:
- Pick Up a Grommet – Yeah, I know this one sounds obvious, but picking up the small grommets without losing them is hard. The way that works best for me is to let one sit on a table, then press a finger down on it. The grommet should stick to your finger, and you can then place it where needed.
- Push the Grommet Onto The Blade MCX Body – Push the grommet onto the shafts in the fuselage using your finger. Doing this isn’t easy, and it may take several tries.
Publications Raving About Us May 21, 2009
Draganfly Innovations was awarded the SABEX (Saskatoon Achievement In Business Excellence Award) for our Draganflyer X6 Helicopter on May 14, 2009. Nominations for the award closed on March 19, and Draganfly Innovations was made a finalist on April 14. The Saskatoon Chamber of Commerce SABEX awards are designed to promote various aspects of business excellence in Saskatchewan. The SABEX awards fall under several categories, including innovation, customer service, and several others. The New Product Award is given to a business demonstrating exceptional performance in launching a new Saskatchewan-made product or device in the last three years, which is both original and currently available to customers.
Criteria for applying for a SABEX award include the following:
- Potential for Market Expansion
- Projected Product Life Cycle
- Uniqueness of Product
- Development and Developmental Stages
- Product Age
We’re very proud to be honoured with this award, and will continue to strive for business excellence.
Lithium polymer batteries are great for RC aircraft, but they have an explosive chemistry that must be treated with caution.
Prevent this from happening to your batteries by following these tips:
- Store lithium polymer batteries in a flame proof LipoSack while charging. - Charging your lithium polymer batteries in a flame proof LipoSack can contain a fire should it occur. It could mean the difference between a minor clean up and the loss of your house or car. Also make sure that the storage area is well ventilated.
- Read the manual – The importance of reading your battery and chargers manual cannot be emphasized enough. The battery manual will state the proper charging rates and times.
- Use common sense – Don’t charge batteries unsupervised. Even when you do everything right, incidents can occur. Also, do not charge lithium polymer batteries in your car. A flame out can be disasterous if it occurs inside a vehicle.
- Use the right battery charger – Charging a lipo battery with a charger designed for other batteries will cause problems, and will probably result in a fire.
- Charge lithium polymer batteries on a fire proof surface – It’s really important to charge lithium polymer batteries on a flame proof surface such as concrete. In the event of a fire, a fire proof charging surface will stop it from spreading, or at least slow it down significantly.
- Keep a fire extinguisher, or bucket of sand near the charging area – If a fire does occur, you don’t want to be running around looking for something to put it out with. Water will not help put out a lipo fire. Being a conductor, it will cause a short circuit and could even make the fire worse.
- Don’t charge lithium polymer batteries near flammable substances – Lithium polymer batteries are flammable enough as it is. Don’t make the problem worse by storing flammable substances near charging batteries.
- Check lithium polymer batteries for swelling prior to charging and each use – A puffed battery is unstable, and can be in danger of exploding. If you see a puffed battery, immediately disconnect it from the charger or aircraft and put it in a bucket of water. Dissolve a few tablespoons of salt in the water to aid conductivity, and leave the battery in the bucked for about 4 days. The salt water depletes any power remaining in the battery by creating a short, and it can’t catch fire while underwater. After the four days are up, take the battery out and cut off the connectors (which may come in handy for other projects). You can then dispose of the battery in the trash. The battery no longer contains toxic metals, won’t harm the environment, and by using the salt water you’ve guaranteed that it won’t catch fire. This should be done as soon as you see a puffed battery. You can’t salvage a puffed battery, the best you can do is to dispose of it safely.
- Never charge a lithium polymer battery in a model – If you charge a lipo battery in your RC airplane or helicopter, you are risking the total loss of your model. Only charge lithium polymer batteries on a flame proof surface, in a LipoSack.
- Make sure the charging leads are connected properly – Connecting positive to negative and negative to positive can cause a major fire.
- Don’t overcharge batteries – By their very chemistry, lithium polymer batteries cannot be discharged to a potential of less than 3 volts without damage. For the same reason, don’t charge them to over 4.2 volts. This means that you have to land your rc aircraft before the motors stop turning. Some aircraft come equipped with a voltage cut-off, others do not. If you don’t have a voltage cut-off, then land as soon as you sense the propeller or rotors slowing down.
- Double check that the charger settings are correct – Lithium polymer battery chargers require you to set the battery configuration. Ensure that this configuration matches the battery you’re charging, or else your lipo could get overcharged and explode. Some chargers automatically sense the battery configuration, but make sure that the setting is correct regardless. They have been known to be wrong on occasion.
- Balance lipo batteries – Lithium polymer batteries have balance connectors, designed to make sure that each cell in the pack has the same charge. If this isn’t the case, some cells can become overcharged and explode.
- Never let the battery leads touch – If the battery terminals touch each other, the battery will short circuit and, in most cases, be destroyed. If this happens and you get a puffed battery, dispose of it by following tip 9 above.
- Don’t ever store / charge lithium polymer batteries in your car – Unless you hate your car. Batteries can and do explode, and if this happens inside a vehicle the result is usually catastrophic. On a hot day, temperatures can rise inside the car and cause stored packs to rupture.
- In the event of a crash, remove the battery and supervise it for at least 4 hours – A crashed plane’s battery can appear fine, but can have an internal short circuit. This short circuit can cause an explosion, even hours after the crash occurred. A LipoSack is a great place to keep a battery that’s been in a crash. If enough time elapses and nothing happens, then your battery is probably fine. If you see puffing, dispose of it immediately following the instructions in tip 9 above.
Always use common sense, read the manual, and know the risks associated with lithium polymer batteries. Handled properly, the risk of a fire is relatively small. Store lithium polymer batteries in a LipoSack for additional saftey.
Product Announcements May 19, 2009
Mini RC helicopters are great fun, and a number of creative people on the web have found ways to improve, hack, or otherwise modify them. Here’s a list of some of the best mods we could find, credit for the ideas goes to their respective creators.
- Build An Awesome Airframe – Several users of rcgroups.com have reported that replacing a micro heli’s styrofoam airframe with cable ties works wonders for flight performance. I think the key’s in the reduced weight, letting the RC helicopter fly faster and higher. Some might prefer the original fuselages looks, others may like this minimal appearence. Make the new airframe using plastic cable ties available almost everywhere, and thick CA glue. Remove the old styrofoam fuselage with a sharp hobby knife, being careful not to damage the internal components, and then build up a new airframe with the cable ties. Here’s a picture showing one such airframe, click the image for a larger version.
- Print a Landing Pad – This isn’t really a micro RC helicopter mod, but printing off this RC helicopter landing pad gives you a landing practice area. Landing RC on a small target can be challenging, so this makes for a great RC helicopter game.
- Color Your RC Helicopter With Spray Paint – In most cases, micro RC helicopters are made of foam with a base color of white. You can use foam safe spray paint to give your RC helicopter a unique look. You can also use clear plastic to add a canopy.
- Build Your Own Fuselage – Most people have a few foam dinner plates laying around, which provide the perfect material for building micro RC helicopter fuselages. Remove the original fuselage with a sharp hobby knife, and build up a new one using material from the foam plates and a foam safe CA glue. This has been done many times, with some remarkable results. Here’s one of the coolest. You can find inspiration by looking at the many mod threads on rcgroups.com and similar sites.
We hope you enjoy doing these mods. Have fun with your mini and micro RC Helicopters!
The Blade MCX is an ideal RC helicopter for beginners. Here’s a list of 10 power tips to help you keep your Blade MCX in the air, and have fun flying it.
- Keep A Few Replacement Parts Handy – Accidents happen, and waiting for replacement parts to come in the mail can be a pain. When you order a Blade MCX, also order a few of the most needed replacement parts. These include the main landing gear, stabilizer fly bar, upper main rotor blades, and inner shaft. We’ll post a detailed how to for adding replacement parts to the Blade MCX shortly.
- Trim the Heli For Easier Flight – The Blade MCX transmitter has trim tabs that you can use to cancel out unwanted movement in flight. Apply trim by bringing the helicopter to a stationary hover, and letting go of the control sticks for a moment. Note the direction that the RC helicopter drifts in, and press the buttons near the transmitter sticks in the opposite direction to compensate. Each trim tab corresponds to the control stick it’s placed next to. Page 15 of the manual has detailed instructions for trimming the Blade MCX.
- Land Before LVC (Low Voltage Cut-off) – At low voltage cut-off, the RC helicopter’s red LED lights will start to blink. This means that the lipo battery is at a minimum voltage, and can’t be drained further without damage. Land immediately. Flying past LVC will damage the battery, and you’ll get shorter flight times as a result.
- How To Fly Faster – Flying forwards using only the pitch control doesn’t make the Blade MCX go very fast. You can increase speed by increasing throttle as you pitch forward, and by flying in a gradual left or right turn.
- Lubricate Moving Parts – If you have trouble controlling the Blade MCX, it could be because parts are not moving freely enough. Use a small amount of light lubricate on the moving parts near the rotor head to allow them to move more smoothly.
- Replace the AA Batteries Included With The Blade MCX – The AA batteries included in the box aren’t as good as those you can get locally. They work fine in the transmitter, but they won’t charge the Blade MCX battery nearly fast enough.
- Keep A Spare Battery Charged When Flying – Why interrupt flying to let the battery charge? If you have a spare battery for the Blade MCX, you can charge one while you use the other, reducing down time for charging.
- Keep the Main Shaft Clean – Foreign objects, especially hair can get stuck in the Blade MCX main shaft. This will make the motors struggle, and could stop them completely. Check for hair or other objects wound around the main shaft before flying and remove any you find with a pair of tweezers.
- Use Rechargeable Batteries in The Charger – Using rechargeable batteries in the Blade MCX battery charger will save you money.
- Close Doors And Turn Off Fans – Closing doors and turning off fans in the flying area will reduce drafts and make flying easier. The Blade MCX was not designed to handle any wind.
Product Announcements May 12, 2009
The Havoc Stinger is a new mini RC helicopter, based on the successful Havoc / PicooZ design. Features include:
- Available in three different colors, green/purple, yellow/orange, and blue/orange
- Powerful 50mAh 3.7V Rechargeable Lithium Polymer battery
- Charge time: 15-20 minutes
- Flight time: 5-9 minutes
- Battery charger is built into the transmitter
- Compatible with all of our mini helicopter parts
The coolest new feature is the glowing eyes and cool insect design, which are included in all three colour schemes. The mini helicopter parts are available in different colors, so you can add matching rotor blades and tail props to the Havoc Stinger.
The Havoc Stinger is for indoor flight only. You can add small amounts of weight to the nose or tail to make the Havoc Stinger move forwards or backwards more quickly.