Brushless conversion for the Piccolo
Brushless controller choices
Tail motor controller
One way bearing
OK, so what is a brushless motor, you ask? In any DC motor, the power needs to be switched between several sections of the armature as it rotates. In a brushed motor, this is done with the brushes. However, they are subject to wear, frictional losses, and electrical losses. In a brushless motor, there are no brushes (duh!) and the switching is done by the controller. It senses the position of the armature and switches the various windings as needed. Brushless motors come in two flavors.... sensored and sensorless. A sensored motor has internal sensors (duh again)that tell the controller where the armature is. A sensorless does not have sensors (duh?) and instead, senses the armature position by examining the voltage output from the idle phase. Sensorless motors are the norm these days, and are cheaper and somewhat lighter. They also can self adjust the timing to optimum for any speed. However, they can sometimes have trouble starting and can cause the motor to oscillate back and forth while starting. This is hard on the gears and mainshaft but it is the way things are. See One way bearing, below.
Converting a Piccolo to use a brushless motor has several advantages. First, you will have more available power and longer flights. More power because the brushless motor generally has a hotter wind and will produce more RPMs for the same applied voltage. And longer flights because brushless motors are generally about 10% more efficient than a similar brushed motor. And lastly, a brushless motor is essentially maintenance free. There are no brushes to wear out, and the only moving parts are the armature and bearings. It will develop the same power in 10 years that it does today.
So why isn't everyone using them? Well, they are much more expensive compared to a brushed motor, especially after you figure in the controller. Brushless motor require a special controller specifically made for brushless motors. They will NOT work with a regular controller and they will not work with the Piccoboard. By comparison, an Ikarus 295 motor costs something around US$17. An Astroflight brushless 010 costs US$75 and the controller costs anywhere between US$50 and US$120 depending on what you get.
So is it worth it? In my opinion, DEFINITELY. Once you fly brushless you will not want to go back, especially if you are flying collective pitch (either flybarless or the Ikarus version).
The three choices that I am aware of are the Astroflight 010 and the Hacker. However, I am only familiar with the Astroflight 010 so I will confine my comments to it.
The Astroflight 010 is available by itself from Astroflight and elsewhere for about US$75. It is also available with an Astroflight controller as a combination package for about US$120. However, this controller is a re-branded Jeti 06-3P and as of this writing (December 2001) has some quirks that make it questionable for heli use. See Brushless controller choices, below.
The motor is a drop in perfect fit in the Piccolo. All you need are two 4-40 machine screws. It fits the frame with no modification.
In general, you want to fly the smallest pinion that gives acceptable power. The Astroflight 010 has a 1/8" shaft, and pinions made for the Ikarus ECO8 fit it perfectly. I fly the 10 tooth pinion, but some have reported good results on the 11 tooth pinion too. These are available anywhere that sells ECO8 heli parts. I got mine from Dymond Modelsports in Oshkosh Wisconsin.
If you use the Ikarus method of mounting the battery, the pinion will work without modification. However, if you use the 2X4 stick packs that I use, the pinion will hit the battery pack unless it is pushed all the way onto the shaft. But it cannot sit that low with the stock grub screw because the grub screw hits the motor mounting bolt heads and/or the inner edge of the frame hole. You will probably need to grind off the inner end of the grub screw so that the screw clears the bolt heads and the pinion can sit farther up the shaft. This is an easy task on a Dremel or grinding wheel.
Brushless controller choices
The controller choices I am aware of at present are the Jeti 06-3P (about US$50), the ORIGINAL (see below) Astroflight controller (same as the Jeti but with slower throttle response), the Shulze Future 18be, and the Castle Creations Phoenix 10 and Phoenix 25.
I do not currently recommend either the Jeti or the ORIGINAL (see below) Astroflight controllers because they both have an annoying "step" in the throttle response at approximately the 75% power point. This step makes hovering at a constant altitude very difficult when the hover point coincides with the position of the step. In addition, the Astroflight controller I tried had a response time that was too long for use in a fixed pitch heli.
However, AstroFlight has recently been supplying a cut down version of the Castle Creations Phoenix 10 with the bundled AF010 motor. This controller is the same as the regular Phoenix 10 except that the only programmable option is the brake disable. As such, it is an excellent value and will work well in any micro heli. Throttle response, like the regular Phoenix series, is smooth and step-free.
The Schulze Future 18be (available in the US from RC-Direct) is an excellent choice although it is more expensive and heavier than the newer Castle Creations Phoenix line. The Schulze operates smoothly, starts reasonably (although a bit abruptly), and has given me more than a year of totally trouble free service. It is approximately the same size as the Piccoboard, and fits the heli well. Later versions seem to start smoother than the early version that I own.
The Castle Creations Phoenix 10 and Phoenix 25 are my current favorites. They both start and run as smoothly as any brushed motor. They have many programmable features such as automatic or fixed end points and a governor function for CP helis. They are lighter and less expensive than the Schulze as well. And they will run a CDROM motor beautifully.... something that the Schulze will not do.
Tail motor controller
While not directly related to a brushless conversion, the tail motor controller is important if you plan on running on 8 cells. A conventional ESC will eat the tiny tail motor brushes in short order on 8 cells. See also Tail motor in the Hints and Tips section for more detail. I strongly recommend using the JMP HF9 controller for the tail, since it operates at a very high frequency and outputs essentially pure DC instead of the chopped DC that conventional ESCs produce. The tail motor will last a LOT longer on 8 cells with the HF9 driving it.
Note that there is the regular HF9 and a special heli version that has 32 steps instead of the standard 16. Both will work, but the tail control will be smoother with 32 steps.
I use the Ikarus Mini Gyro with the case removed. When I bought it it was the only small gyro I could find. I see that Hobby-Lobby is now carrying the Ikarus Micro Gyro, which is even smaller, and no longer shows the Mini Gyro. I also understand that the GWS PG-03 is a good choice.
The Ikarus (and I assume others) has two adjustments. The gain is adjusted as usual.... use as much gain as you can use without the tail wagging. The zero or centering adjustment is adjusted so that turning the gain adjustment does not change the output. To make this adjustment, merely power up and adjust the rudder trim until the tail motor starts. Then vary the gain and watch the tail motor. If it speeds up or slows down, adjust the zero pot until the gain pot does not affect the tail motor speed.
Note that you can use the zero adjustment to offset the rudder channel signal and allow the tail ESC to arm if you do not have a transmitter with adjustable subtrims. However, if you do it this way changing the gain will affect the rudder channel zero point and possibly cause arming problems.
Wiring is fairly straightforward (unless you are retaining the Piccoboard for the tail functions). See this diagram for how I have mine wired (I show the pitch servo for collective pitch applications). Starting from the battery, the power is wired to both the brushless controller and the tail controller. I added two female connectors (same as used for the tail motor) to the battery input pads on the Schulze and mating male pins on the wires from the tail ESC. That way, the tail ESC plugs into the Schulze and I only need one set of leads to the battery. The signal lead from the brushless controller plugs into the throttle channel of the receiver. The signal lead from the tail ESC plugs into the gyro, which plugs into the rudder channel of the receiver. If the signal input to the tail ESC has three leads (the heli version of the HF9 only has one), it is a good idea to disconnect the (+) wire to prevent the BEC output from being connected to the BEC output of the brushless controller through the gyro and receiver.
You will need a transmitter with a free mix at a minimum, and I recommend a heli radio with a revolution mix function for best tail control. Since that is what I fly, I will confine my comments to that setup.
The Schulze controller is self configuring. You power up with the throttle stick at full throttle (to disable the brake)and wait for it to beep. You then lower the throttle to idle and wait for it to beep again. After the second beep, it is ready for use and has set itself to the throttle channel end points.
Note that it is imperative to disable the brake! If the brake is activated with the rotor spinning, you can strip the main gear and/or crack the mainshaft unless you are using a one way bearing.
The rudder channel is a bit more involved. First, set up the gyro per manufacturers instructions if there is a centering or zero pot. This will prevent gain changes from affecting the centering which will in turn affect the action of the tail ESC. Now you have to adjust the transmitter rudder channel so that the ESC will initialize. On my Futaba 8UAFS, I have the subtrim set to zero and the revolution mix set so that the first point is about -50%. This allows my HF9 to initialize. To set the other four points on the revolution mix curve, apply throttle and position the throttle stick so that it is on each mix point in turn, and adjust that point so that there is no yaw tendency. This can be done roughly by holding the heli and feeling whether it wants to yaw at each point on the mix curve. Fine tuning can be done by flying, and especially by flying with reduced gyro gain.
The Schulze controller (and others as well) are microprocessor based devices and have rather healthy interference fields surrounding them. This can be a mild to serious problem, depending on component placement. In addition, the motor wires are also significant interference sources... especially the main motor wires. I found that the interference was noticably reduces when I twisted the main motor wires together and kep them absolutely as short as possible. Mine are something between 1.5" and 2" long, and are routed directly to the Schulze controller which is mounted vertically with the motor wire pads facing the motor.
I also eventually ended up placing the receiver behind the mainshaft and away from the two controllers and gyro, which mount where the Piccoboard used to mount. Do a very careful range check before that first flight! I recommend placing the transmitter on the ground and holding the heli while you walk away from the transmitter, so that any glitches do not upset the heli. Watch the servos carefully for any early signs of trouble, since a massive glitch on the throttle channel can cause the motor to stop abruptly and damage the gears or mainshaft. Don't ask me how I know! You should get at least 20 feet of perfect operation with the transmitter antenna collapsed, and more is better.
One way bearing
While not required for brushless flight, a one way bearing will make startup much easier and relieve most of the strain on the mainshaft as the motor stutters on startup. It will also totally prevent any gear damage in the event of a sudden motor stoppage. And of course, it is required if you fly collective pitch and want to attempt an autorotation (NOT ME!). Note that the fixed pitch and collective pitch versions are slightly different due to the difference in mainshaft length.
There are two one way bearing kits currently available. A fellow in France (we all call him "Nath" because that is his username on the Piccolo BBS) has a nice one way bearing kit for the fixed pitch Piccolo and is in the process of developing one for the Ikarus version collective pitch Piccolo. The fixed pitch version uses a solid steel mainshaft and a machined plastic bearing holder that mounts under the main gear with two or four screws. Rumor has it that the collective pitch version will use a hardened solid steel shaft. Nath can be reached at: firstname.lastname@example.org. I have been using Nath's one way bearing kit on my flybarless brushless collective pitch Piccolo and it works great.
A Hornet flyer in California named Walt Ferar has also developed a really nice one way bearing kit for both the standard fixed pitch Piccolo and the Ikarus version collective pitch Piccolo. This kit uses a hollow (ie., light) mainshaft made from 316 stainess and a nicely machined aluminum bearing holder. The bearing holder has two tiny screws that project upwards and engage the spokes in the main gear without actually attaching to them. The bearing holder is held against the underside of the main gear when the mainshaft is pulled upwards and secured by the plasitc collar that holds the mainshaft in place (someone want to come up with a version of that collar with a setscrew? PLEASE?). Total weight is 5.8 grams, which is an approximately 4.7 gram increase over the stock setup. The kits are available from Walt Ferar for $50 as of December 2001.
I have had the best luck with the brushless controller, gyro and tail ESC mounted on the radio mounting tab on the front of the frame and the receiver mounted on the left side of the frame behind the mainshaft (on the other side from the roll servo). This avoids placing the receiver tooo close to the ESCs and reduces interference to a manageable level.
To mount the ESCs and gyro, I used a small block of balsa the same length as the brushless controller and as wide as the mounting tab. The brushless controller and gyro are rubber banded to each side of the balsa block with the tail ESC sandwiched against the brushless controller. This assembly is then slipped over the mounting tab and held in place by the rubber bands.
The receiver is mounted using velcro to a small piece of plastic sheet CA'd to the triangular area behind the mainshaft.
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