Brushless FAQ
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Frequently Asked Questions

  1. What is a brushless motor?
  2. Can I run a brushless motor on my current ESC?
  3. Can I run 2 brushless motors on one brushless ESC?
  4. Do you run two motors in the E-Maxx?
  5. How much does going brushless cost?
  6. What speeds can you get with brushless?
  7. How does the run-time compare to stock?
  8. Is there good torque?
  9. Is there a special type for the RC car?
  10. What brands of brushless motors are there?
  11. Who makes the best system?
  12. Where do I buy brushless systems?
  13. How many cells do you run?
  14. What does the number of "turns" affect?
  15. Does my gearing have to change?
  16. What is the difference between sensored and sensorless systems?
  17. What is "cogging"?
  18. What is a "thermal"?
  19. Can I run a different brand motor from the ESC?
  20. What is a BEC and how can I use it?
  21. If I go brushless, do I need to do anything to strengthen the E-Maxx?
  22. All of my batteries have standard Tamiya connectors.  Can I continue to use those with BL?
  23. What about batteries?
  24. What about wiring?
  25. What should I look for on a controller?
  26. If my controller has adjustable current limiting, what should it be set to?
  27. Do I need to fabricate anything to run brushless?
  28. Where do I find 4mm and 5mm pinion gears for my large-shaft BL motor?

  1. What is a brushless motor?  A brushless (BL) motor has no brushes and no commutator (comm) to mark the timing for the motor.  It also has the magnets on the spindle, instead of around the can (as they are in brushed motors).  Some have described a brushless motor like a brushed motor turned inside-out.  I think that description is a bit confusing, personally.  Brushless motors require little to no maintenance and are said to maintain their strength and power for as long as the magnets hold their magnetic pull, which could be many years.  Brushless motors are incredibly efficient, losing only about 15% of electric current to heat.  Because of this efficiency, and the lack of resistance due to not having a commutator and brushes rubbing, the brushless motor is extremely powerful.  A brushless motor does not have brushes to replace regularly, or a comm to lathe, so the annoying maintenance factor is greatly reduced or eliminated.
  2. Can I run a brushless motor on my current ESC?  No.  Brushless motors rely on a microprocessor-controlled timing device and 3-phase MOSFET amplified power that exists only in special brushless motor speed controllers.  These special speed controllers are the most important part of a brushless system.  They are capable of "reading" the position and timing speed of a brushless motor by sensing the pulses of current through the wires that feed the motor, and reacting at real-time accordingly.
  3. Can I run 2 brushless motors on one brushless ESC?  Not for land use.  Since the electronic speed controller (ESC) is so busy reading the pulses of one motor, another motor in the loop would just confuse it.  It's not possible for sensored controllers like the Aveox to run 2 motors because of the sensor design intended to "read" a single motor, and although some airplanes can get away with running 2 motors on a single sensorless ESC, low-speed control and smooth starts are absolutely necessary in cars making it infeasible for land use.
  4. Do you run two motors in the E-Maxx?  You can, but it is not necessary.  Because of the amazing torque and power of the brushless system, a large vehicle like the E-Maxx can use just one motor system, and still improve performance over stock.
  5. How much does going brushless cost?  A brushless motor alone can cost anywhere from $90 to $250 or more.  The speed controller can cost anywhere from $100 to $500 or more.  How much you spend on a system depends on how far you want to take it.  Additionally, stock parts on an RC car are rarely developed to handle the intense increase of power that a brushless motor system offers.  You will probably spend quite a bit of money just strengthening drive-train parts, unless you go with one of the less-powerful brushless systems.
  6. What speeds can you get with brushless?  On average, a sub-$400 brushless system will bring the E-Maxx to around 35 MPH +/- 4 or so MPH, depending on the setup and weight of the truck.  It is possible for a mid-range single-brushless-motor system to push the E-Maxx to over 40 MPH, and even 45 MPH with larger single motors and a lot of battery cells.  A dual-brushless-powered E-Maxx could easily gear up because of the added torque of an additional motor, to exceed 45 MPH without breaking a sweat, and some of the more powerful dual BL systems are pulling the E-Maxx to speeds in excess of 50 MPH.  I, personally, think that anything over 35 MPH is useless in the E-Maxx, as a monster truck, but I shoot for 40+ MPH, just for fun.  In light street cars, speeds of well over 100 MPH have been achieved.
  7. How does the run-time compare to stock?  Because of the amazing efficiency of the brushless motor system, run-time will actually improve, unless it's geared higher than its optimum range.  Even then, it will be at or near stock run-time, with the additional power of brushless.
  8. Is there good torque?  I would estimate that the torque of a commonly used brushless motor is actually about double that of a standard 540 size brushed RC motor.  Where you get much of your power is from the low friction and high RPM of the brushless motor.  A brushed motor may top out at around 25,000 RPM, where brushless motors range from 35,000 to 80,000 RPM or more.  100,000 RPM is sometimes reached by these motors in competition for short bursts.  The brushless motors with lower RPM ranges usually have more actual torque than the higher RPM versions, which make them competitive in the overall results.  Some of the larger BL motors are torque monsters which pump out amazing power at even lower RPM ranges, even in the 20kRPM neighborhood.  Finding the delicate balance between efficiency and current-draw for your car is crucial.
  9. Is there a special type for the RC car?  Kinda'.  RC cars are harder on motors than RC airplanes (airplanes are where brushless motors are most commonly found).  Because of this, the physical structure of the motor must be strong.  Also due to the constant speed changes, they need to be very  resistant to heat damage.  The motor needs to fit the RC car mounting position and should have a standard 1/8 inch shaft for the common car pinion gear.  From the hundreds of brushless motors available, only a dozen or so makes will work nicely without significant modification to either the motor or the car.  Of the most popular models, the Aveox RC7 and Lehner car motors can be used without any modification except for making a small notch on the shaft for the pinion gear set-screw.  Hacker B50 series motors work very well too, but have some experiences of their end caps popping open.  For these, a dab of high temperature thread locker around the inner lip of the cap can be used to prevent further openings.  Hacker's new C50 series motors already have a notch on their 1/8th inch shaft and have reinforced super-size cans specially designed for the abuse of land use, and address the end-cap problems.  Also, many hacker motors ship with a 5mm shaft, so be sure to look for the motors that specify 3.17mm or 1/8th inch shaft.  Or, you could order specially drilled pinion gears that have been altered to fit a 5mm motor shaft.  Another consideration for cars is the motor's power under the number of cells you will be running in your car.  For example, the Hacker B50 8S motor runs nicely on 6-8 or more cells.  This would be a good motor for cars running a single battery pack.  The Hacker B50 12S motor, however, would need 12 or more cells to reach potency, requiring much larger or multiple battery packs.
  10. What brands of brushless motors are there?  There are so many, I won't list them all, but the most commonly used brushless motors for use in RC cars are:  Hacker, Aveox, and Lehner.  These, as mentioned above, require special speed controllers.  Hacker (Jeti), Aveox, and Lehner (BK) have great brushless speed controllers, and Schulze comes into the picture by producing outstanding ESCs that are capable of running these motors as well.  There are 2 more companies new to brushless systems, that should be mentioned.  Team Orion is releasing a sensorless BL motor system and Novak has released their first sensored BL system designed for light cars and trucks.  Aveox and now Novak remain the only BL systems of choice for RC cars, that are manufactured and supported in the USA.  Most others are based in Germany.  Many of the new Hacker products (C50 motor series and Car speed controllers) are distributed and serviced by Hacker USA in Arizona.
  11. Who makes the best system?  "Best" as in fastest, most expensive, best technical/customer support, highest quality and reliability?  There is no way I can answer that question with a definitive answer.  From what I've seen, the most popular brushless motor is the Hacker, and the most popular speed controllers are probably the ones from Schulze although Hacker's newly designed car controllers, the Hacker Master Car Sport and Car Competition controllers are quickly becoming the new top-sellers of brushless ESC for land use, due to their nice block case and built-in heat sink, along with the strong backing that Hacker is providing for their customers.  Because of the high cost of brushless systems, it's still not a widely visited topic by most RC car enthusiasts, and lacks a substantial amount of comparison information.  I will caution buyers to be aware of the lengthy service times experienced by users of the German Lehner (BK) and Schulze products.
  12. Where do I buy brushless systems?  Most of the time, you can buy the system from the manufacturer's web site.  There are resellers like www.aircraft-world.com who may carry the brand and type you're looking for at good prices too.
  13. How many cells do you run?  This depends mostly on the RPM per Volt rating on the motor and it's maximum reliable RPM, but also involves the capability of the ESC.  Since "cells" are rated at 1.2Volts and good cells put out about 1.1V under a load, you can calculate this for yourself.  If you're interested in a motor that has a max RPM of about 50,000 and it is rated at 3500 RPM/Volt, then 12 cells would be optimal.  For example, multiply 1.1V by 3500 RPM by 12 cells, and you get 46,200 RPM, which is within safe and powerful range for that motor.  Please note that typical good batteries will have an actual "measured" voltage of around 1.05-1.16 volts.  These actual numbers should be used when calculating the true RPM of the motor.  Consider, also, that the more cells (Volts) you run, the higher your Amps are, so your "spunk" or "torque" will be increased with motor systems that run on higher cell-counts.  For example, the Lehner Basic 5300 and Basic 4200 motors have the same peak RPM capabilities, but since the 4200 has a lower RPM/V and can run on more cells, it will have more torque than the 5300.  However, in small car applications, the 4200 will have lower top-end speeds on only 6 and 7 cells than the 5300 on the same number of cells.  Also, be sure the controller can handle the number of cells you plan to run.
  14. What does the number of "turns" affect?  In most brushless motors, the higher the number of turns = the lower the RPM/V rating.  This gives the motor a higher cell limit.  Generally, as mentioned above, the higher the turns, the more cells, the more torque you get.
  15. Does my gearing have to change?  Probably.  Although brushless motors have significantly more power than the dual stock motors in the E-Maxx, most popular models get a great part of this power from high RPM.  Different motors and different driving situations define the number of teeth you should run on your primary pinion and spur gears.  Your final-drive gear ratio does not need to be changed.  Usually E-Maxx folks start with a 14 tooth pinion gear and the stock 66 tooth spur gear to decide what they need to change to improve it, but that completely depends on your power plant.  Higher gearing = smaller spur gear and/or larger pinion gear.  Lower gearing = larger spur gear and/or smaller pinion gear.  To improve torque/acceleration and decrease temperatures, you'd go to lower gearing.  To improve top-end speed, you'd go to higher gearing.  On the flip-side of this, some of the more powerful brushless motor systems will actually be able to have your gearing raised.
  16. What is the difference between sensored and sensorless systems?  Sensored brushless motor technology has been around the longest, but it is still being implemented today because of its flawless control at low speeds and reliable rotation.  Basically, a sensored system (like Aveox) has a set of 5 sensors and cables, in addition to the 3 power cables on the motor.  These sensors constantly "talk" to the ESC, telling it what position the motor is in, how fast it's turning, and whether it's going forward or reverse.  This level of necessary communication usually decreases the maximum RPM of the motor system compared to sensorless systems, but this can be made up for by making the motor to have more torque.  Sensorless systems, like the Hacker and Lehner, read pulses of current in the power cables to determine rotation and speed.  Because of this, they tend to be capable of higher RPM, but may suffer "cogging" under a load at very low, starting speeds.
  17. What is "cogging"?  Cogging, as mentioned above, is a phenomenon that occurs with sensorless brushless motor systems at initial starting speed, and it goes away immediately after moving.  It's caused by the ESC taking a moment when you hit the throttle to "read" the motor position and react.  It can be described as a minor "glitching" or "jitter" at the moment you hit the throttle.  It can be decreased or almost completely eliminated by lowering the gearing.  Different ESC's can have different cogging symptoms too.  It's hardly notable if your system is set up correctly, but folks who plan to do low-speed high-power maneuvers like rock-crawling or intricate and detailed track racing, should consider the possibility of this affecting their fun.
  18. What is a "thermal"?  Almost all decent brushed and brushless speed controllers have a built-in high-temperature protection circuit.  A "thermal" is what happens when the ESC's temperature has exceeded the threshold of this temperature, and tripped the protection.  The ESC will temporarily shut off to warn you that it's getting too hot.  Some times this can be for just a few seconds so you can at least drive the vehicle back, or it could be until the temp has lowered to a comfortable level again.
  19. Can I run a different brand motor from the ESC?  Yes.  Most sensorless ESCs have adjustable timing and signal frequencies you can adapt to most popular types of brushless motors, including sensored motors.  You cannot, however, run a sensorless motor with a sensored speed controller.
  20. What is a BEC and how can I use it? BEC stands for Battery Eliminator Circuit.  It is an electronic device on the ESC that emulates a power supply and uses the main system batteries to power the receiver pack and servos.  With this device, you do not need additional batteries to power the auxiliary devices like the receiver, servos, and/or lights, etc.  It feeds a steady flow of around 5 Volts to the receiver system.  If you run a brushless system that requires over 10 cells, it is not recommended to use the BEC feature at all.  The high input voltage does not get divided well and can cause overheating in your speed controller.  Furthermore, in the E-Maxx, the steering servo requires so much amperage to run it, that you can cause additional heat in the ESC.  For over 10 cells, you should run a separate receiver pack, like the ones found on nitro'-powered RC vehicles, bypassing the BEC capabilities of the brushless ESC.
  21. If I go brushless, do I need to do anything to strengthen the E-Maxx?  Yes.  The E-Maxx is built to (barely) handle it's original stock power.  If you significantly increase that power, you will most likely be breaking and twisting drive-train parts.  It didn't take me long for the need to replace all of my wheel CVD drive shafts with MIP steel and center drive CVDs with SuperMaxx titanium, my transmission idler gears with SuperMaxx idler gears and my differentials with SuperMaxx 7.5 diffs.  With the increase in power, even that wasn't enough and further modification to the transmission is necessary to cope with the power.  Note, there are alternate, less expensive strong parts available for most of this, but replacing these parts with the same stock Traxxas parts will guarantee another failure at some point.  Also, if you hit a tree stump going 30+ MPH you will break more (other) parts than if you hit it going 20 MPH.
  22. All of my batteries have standard Tamiya connectors.  Can I continue to use those with BL?  No.  Brushless systems will draw more current than your stock motor system at bursts of throttle.  It's also more sensitive to resistance (loss) in your wiring.  You should use Dean's Ultra connectors or other zero-loss connectors instead.
  23. What about batteries?  Brushless systems are very sensitive to the types of batteries used.  You should stick with high-quality, high-output, low internal-resistance battery packs containing brand-name Sanyo, Panasonic, or GP cells for best results.  "Matched" batteries provide the best over-all performance but are absolutely not necessary for general use.  If your batteries are old or damaged, it's possible their loaded voltage is not enough to engage or properly run a brushless motor system.  Also, be sure they are getting a good charge.
  24. What about wiring?  Wiring is so important that if you're not willing to spend the time to be sure it's right, you should not venture into brushless power.  There is a very large possibility of a speed controller failure if even the slightest detail is over-looked.  The actual cable used should be of very high quality and of a thick gauge.  I use Deans 12 gauge "Wet Noodle" which is the best silicone jacket cable I've seen yet.  You must also be sure that there is minimal length in the wire both from the battery to the ESC and from the ESC to the motor.  Trim as much excess as you can while still allowing the connectors to reach.  The solder-points must be top-notch as well.  Be sure there are no air-bubbles and it's not "cold-soldered", which will appear hazy instead of shiny after cooled.  There are 3 wires between the motor and ESC.  It shouldn't matter which ones are in which order, unless specified by your manufacturer (like with the Aveox that must be in the correct order).  Some use the general rule-of-thumb to connect the middle wire to the middle wire and if your motor is not spinning the correct direction, switch the outer 2 wires only.
  25. What should I look for on a controller?  Since the speed controller is the most important part of the brushless motor system, it's essential that you use one suited for its application.  Light RC vehicles will not require as much current-flow to spin up the motor under the load, unless the motor you use is very small and over-worked.  Light cars won't need high-amperage controllers generally.  As the car increases in weight or drive-train drag with larger tires and so on, usually the motor's current-draw increases and so does the Amp draw needed to spin up the motor under the added resistance.  The controller should increase its Amp (current) capabilities to meet the demand of the motor.  As the vehicle size and drag becomes enormous as with the E-Maxx, there is a tremendous strain put on the BL system in bursts of throttle and start-up.  In this case the speed controller will need to be able to handle very high current and the heat created by the current.  Those high Amp, high heat, high cell-count controllers can be quite expensive.  Generally, the greater the Amp rating on the controller, the better it handles heat as well.  Cell-count capabilities are also important.  If you plan to run a motor on 12 cells, you should not use a controller rated at only 10 cells.  It may even be a good idea to get a controller that's rated beyond the intended cell-count for the peace of mind knowing it can handle the high voltage and extra heat.  Other things to look for and consider with the controllers are whether it has proportional brakes and/or reverse which may be important to you.  Many BL controllers are made particularly for aircraft and boat applications, which may not be suitable for land use.  Also remember that a sensor-type controller cannot control a sensorless motor, but a sensorless controller can run a sensored motor.  Last, but not least, your controller should physically fit in a safe, ventilated place in the vehicle.
  26. If my controller has adjustable current limiting, what should it be set to?  The current limiter not only protects the controller and possibly the motor, but can also help to improve run-time.  You should start with the limit set to the lowest Amp level and run it that way to see if it's sufficient.  Regardless of the limit setting, your top-speed will still always be the same because you're providing the same voltage to the motor regardless of Amp limiting.  If you find you need to increase the Amp limit, do so in increments until you find a position that is suitable for your driving needs.  Rarely, if ever should you run these types of controllers with an open limit.  If you are at the top setting and still need more power, it may be time to seek a higher-power motor system.  Don't try to make a system work harder than it's designed -- you will likely cause a failure in the motor or controller.
  27. Do I need to fabricate anything to run brushless?  Normally, no.  But, on some vehicles, it may be necessary to provide additional heat dissipation or cooling for the controller.  This would include adding heat sinks (like those found on computer chipsets), or a heat sink type shroud to help spread the heat out over a larger area, or a small DC fan, or even a combination of those.
  28. Where do I find 4mm and 5mm pinion gears for my large-shaft BL motor?  Several resellers stock these pinion gears.  Be sure to specify the pitch and number of teeth you are needing, when contacting them for the gears.  For example, 32-pitch for the E-Maxx.  www.rumrunnerhobbies.com , www.maximizerproducts.com and www.finedesignrc.com all carry those hard-to-find pinion gears.