Tuesday, 4 October 2011

Electronic Speed Controller (ESC)

Scorpion Commander 6s 90A


The Scorpion Switching BEC Series Brushless Speed Controllers represent one of the best values in the speed controller market today. From the beautiful gold anodized heatsinks, to the unique metal containers that the ESC's are shipped in, everything about Scorpion Speed Controllers shows the company's commitment to quality. These ESC's are manufactured from top quality components, in a state of the art manufacturing facility, and are designed to provide years of trouble free operation.
Each Scorpion 6-cell Speed Controller includes a built-in Switching Style BEC circuit. This BEC provides a regulated output of 5.7 volts, and can deliver 3 amps of continuous current with 4 amp bursts. With a Switching type BEC, you do not need to de-rate the BEC as the input voltage increases. The full 3 amps of BEC current is available for any input between 2-cell and 6-cell Li-Po operation.
These new 6-cell Speed Controllers also offer a unique wireless programming system that is a first in the RC Model Industry. Unlike other ESC manufacturers, who require you to buy an add-on programming module to gain full functionality of the controller, Scorpion provides a full feature Programming Card with EVERY speed controller sold, at No Extra Charge!
The new wireless programming system consists of a postage stamp size IR receiver module that mounts in your model, and a credit card sized IR Transmitter that easily fits in your pocket or toolbox. The IR receiver plugs into the throttle channel of your radio receiver, and then the Speed Controller plugs into the IR Receiver board. To program the ESC, you simply flip the switch on the IR Receiver board to the program position, point the transmitter at the IR receiver board, type in the parameter you want to adjust and hit the Enter button. The IR board will give you a flashing light and a motor tone to acknowledge the command. Once you are finished programming, you simply flip the switch on the IR Receiver board to the Run position. This will re-boot the ESC and enter the new program into memory. After this is complete, you can fly your aircraft.
Programming your ESC has never been easier! There is no need to dig the receiver out of the plane, No need to unplug any cables, and no more dragging a laptop computer to the flying field! Programming your ESC is as easy as changing channels on your TV!
The adjustable parameters on the Scorpion 6-cell ESC's include many extra options not found on other controllers. These options include:

Low Voltage Cutoff: Adjustable from 5.0 to 25.0 volts in 0.5 volt increments

Brake Setting:
Adjustable in 5 steps from No Brake to Very Hard Brake

LVC Cut-off Type: 50% power, Pulsed Output and No cut-off are available

Motor Acceleration Delay: Slows motor response for use with gear box motors. Adjustable in 5 steps from 0.15 to 1.3 Seconds

Current Overload Protection: Can be turned on or off to suit your preference

PWM Frequency: Adjustable to 8KHz, 16 Khz, or 32 Khz

Soft Start Mode: Slows down motor spool-up for Helicopter use

Motor Rotation: Adjustable to normal or reverse rotation

Motor Timing: 6 options available, Auto Detect, 5°, 15°, 20°, 25°, and 30°

Governor Mode: For Helicopter use, 5 settings are available 50%, 60%, 70%, 80% and 90% throttle

Starter Boost:

For starting very High Kv motors that can be difficult to start
Scorpion Speed Controllers also include all of the ESC parameters clearly labeled on the heatsink assembly. Voltage range, current rating, BEC rating, and input polarity are all clearly marked to avoid any confusion. Scorpion 6-cell Switching BEC Series Speed Controllers are also backed by a 2 year manufacturers warranty against defects in materials and workmanship, so you can buy with confidence. For a total package of Quality, Performance and Value, use Scorpion Brushless Speed Controllers.
  • Scorpion 90A ESC
  • New wireless programming system
  • 6S                                   

Phoenix ICE 50 Brushless ESC


  • 34 volts max input, 5 amp output
  • Adjustable BEC output (anywhere from 5 to 7 volts in .1 volt increments)
  • Fully Programmable, with Heli Features
  • On Board Data Logging                 

Phoenix ICE HV 80 Brushless ESC


Welcome to the next generation of high voltage brushless speed controls from Castle Creations. We invented this class, Castle Phoenix HV series are the gold standard. Now we’re raising the bar.
Phoenix Ice HV controllers offer incredible reliability and flexibility for your high powered applications. Now available in 40, 60, 80, 120, 160, and 160 Lite amp configurations.
  • Ready to fly out of the bag, but users can tap into serious computing capabilities by connecting them to Castle Link software using a Castle Link or Field Link programming card.
  • Comprehensive heli feature set, including direct entry governor mode, autorotation with bailout, and soft start capabilities to protect your gearing (see the screenshot on the right for more details).
  • Opto isolated throttle cable helps reduce radio interference
  • Full data logging capabilities. Measure amp draw, controller temperature, motor rpms, battery voltage and ripple and more. Take the mystery out of electric flight!
We now offer the Quick Connect for more convenient data log downloading and adjusting controller settings. The quick connect is a special harness that allows you to keep the speed controller plugged into the receiver when connecting to the Castle Link. It has an extra 12" servo lead that can be placed wherever it is convenient to plug in the link, while your speed controller stays connected to the receiver. No more digging into your setup to get to the receiver just to pull off your data or change settings!
Designed in Kansas. Components manufactured in the USA, Mexico, and China.
Castle Creations, Inc. warrants this product to be free from manufacturing defects for a period of one year from date of purchase.


  • Recommended for helicopters and sport aircraft
  • Onboard Data Logging
  • Castle Link compatible
  • Opto isolated throttle lead
  • Handles up to 12S LiPo (50V) maximum input                         




Dimensions (LxWxH): 2.6x1.3x0.8" (40.6x33x20.6mm)
Weight (without wires): 2oz (56.7g)
Max Amps: 80 Amps*
Max Voltage: 50V - 12S LiPo or 36 Cell NiMh/NiCd 

  • Length: 2.8" (71.12mm) with capacitors
  • Width: 1.3" (33mm)
  • Height: 0.9" (22.9mm)
  • Weight: 2oz (56.7g)
  • Max Amps: 80A
  • Max Volts: 50V (12S Lipo, 36S NiCd/NiMH)
  • Phoenix
  • ICE HV
  • 80A Brushless ESC                      

Phoenix ICE 100 Brushless ESC


Welcome to the next generation of Castle air controllers, the Phoenix Ice series.
Phoenix Ice brings the ability to run at input voltages of up to 8S* (33.6) and use the built in switching BEC to output up to 5 amps of servo power all the way up to the 8S max*!

Switching BEC

The Phoenix Ice switching BEC output is factory set to 5.0V. Users may use Castle Link to select their desired voltage between 5.0V and 7.0V, in 0.1V increments.
Data Logging
Ice brings another incredibly useful feature, extensive data logging capabilities. The controllers are able to measure and record many parameters at sample rates that you choose between 10 samples per second and 1 sample per second. Data points include:
  • Battery Voltage
  • Battery Ripple
  • Battery Current
  • Controller Temperature
  • Controller Input Throttle
  • Controller Motor Power Output
  • Motor RPM
This data is stored directly in the controller and may be accessed once the run is over using the Castle Link USB adapter (sold separately) and Castle Link software (available free at castlecreations.com). The Max Log Size is 21,504 bytes, everything takes one byte except for motor rpm which takes two.
  • Logging 'Battery Current' at only a 1 sample / second - 358 minutes of logging time (almost 6 hrs)
  • Logging 'Motor RPM' at only 1 sample / second - 179 minutes of logging time
  • Logging everything at only 1 sample / second - 44 minutes of logging time
  • Logging everything at 10 samples / second - 4 minutes and 28 seconds

Two versions: 

Heat Sink 8S max input and Heat Shrink 6S max input

The Ice comes in two versions, standard version which is optimized for demanding RC heli and sport aircraft applications and a Lite version packaged in heat shrink for users with tight fuselages.
All Phoenix Ice are ready to fly out of the bag, no programming is necessary for most aircraft applications. The controllers are set at the factory for Auto Lipo detect/cutoff operation and they are tuned for optimum outrunner performance.
Advanced users will find the incredible programmability of the Phoenix Ice allows for performance characteristics tailored exactly to their desires.
Heli users are raving about the performance of Castle’s programmable helicopter modes which include options to directly enter desired governed headspeeds as numerical values! Every heli power combination requires slightly varying governor gains, Castle makes these easy to tweak and the net result is a rock solid tail.
Designed in Kansas. Components manufactured in the USA, Mexico, and China.
Castle Creations, Inc. warrants this product to be free from manufacturing defects for a period of one year from date of purchase.
  • Phoenix ICE 100
  • Brushless ESC
  • Data Logging
  • 100 Amp
  • 5 Amp BEC


* 34 volts max input, 5 amp output * Adjustable BEC output (anywhere from 5 to 7 volts in .1 volt increments) * Fully Programmable, with Heli Features * On Board Data Logging

Blade Tracking and Balancing for Remote Control Helicopters



WARNING: Tracking adjustment is a dangerous procedure. Keep at least 5m from the spinning rotorhead. It is also recommended to wear eye protection. 

Before following this section, if you are working on a new build, or have yet to mechanically set up the rotor head, please read this first: CCPM Mechanical Setup. It will make sure that you have a good setup on your machine before attempting to balance and track your blades. By the way, my blog will list the latest radio control helicopter guides and tutorials. Sometimes you will get lucky, and have perfectly balanced blades out of the packet. The same goes for tracking, you may not need to track your blades at all. Either way you should definitely follow this procedure to make sure they are operating correctly.

Blade Balancing

This is the easy bit. Essentially, when the rotor blades are manufactured, there might be very slight imperfections in the weight of each blade. Not noticeable to you or I, but once spinning at 1,800 rpm or more, this will cause vibrations in the helicopter. The greater the weight difference, the greater the vibrations.


Helicopter Blade Balancer

A blade balancer comes in useful at this point, you will need to bolt your blades on to it and see if they "balance". If they don't, its time to use the pretty stickers that came with the blades. On the lighter blade, place the metallic sticker at a point along the blade where it makes them balance about there pivot point. Just lay it on initially without removing the adhesive back. When you are sure of the position, fix it in place. You should now have a set of balanced blades. On to the tracking.


Blade Tracking


The first thing you need to do is see if they are actually out of track or not. Time to get out some blade tracking tape, or electrical insulating tape will do. Make sure any edges of the piece of tape are towards the trailing edge of the blade. That way the tape wont come off due to air getting under it. Ideally a different color tape on each blade. Again, if not, just make sure one is well marked.
You will now need to spool the RC helicopter up to a decent head speed, around that suitable for a hover. I personally strap the heli to a workbench, but you can also bring the helicopter into a hover around head height and check from there. What you are looking for is wether one blade bends more than the other. This will be evident as an obvious doubling of the imaged rotor blade edge. With one blade higher than the other. If this is the case you need to adjust some linkages, as your blades are not tracked.

The Reasons Behind Out of Track Blades

Why does this happen i hear you say?! Well, simply, like the balancing, there are very slight imperfections in some blades. So, when a large external force is applied to them they can behave differently. In this case it is one blade flexing more than the other. this is not the only cause, in fact, the more usual suspect, is that when you tried to get zero pitch in your blades during the CCPM setup. There may be some slight pitch in the blade that is impossible to get out during setup.

So, as you may well have guessed, if there is more pitch on one blade than the other, the it will generate more lift, causing it to flex more than the other, and fly higher than its counterpart. Luckily this is very easy to fix.

Effects on Helicopter Headspeed
One thing to think about is headspeed, if you want to get all technical. Say the blades are out by a random figure, lets say 10mm. You could adjust the links so the one flying low comes up to meet the top one, or you could do it the other way round. We have to consider how this will effect the headspeed. As we are changing the pitch of the blade. The safest bet is to raise, and lower each blade respectively by the same amount, so the tracking meets in the middle for the helicopter.

To sum up these effects: If you are happy for the headspeed to increase, the higher blade needs to be lowered. The same is true if you want a lower headspeed, raise the lower blade. As i said above, making them both meet by adjusting equally, will maintain your current hover headspeed.
To actually adjust your blades, you will need to change the lengths of the linkage rods that control the pitch to your blades. It is wise during this step to refer to the manual that came with your RC helicopter, as they can be different from heli to heli. I will provide below a quick guide on how to adjust these on a T-Rex 500 helicopter.
The Align T-Rex 500 Method

Helicopters sharing a traditional flybared rotor head will usually share the same linkages from the swashplate upwards. So the instructions for the T-Rex range will be similar, if not identical to that of other manufacturers. But again, always check in your particular helicopters manual, for vendor specific instructions.

WARNING: Tracking adjustment is a dangerous procedure. Keep at least 5m from the spinning rotorhead. It is also recommended to wear eye protection. 

So, after following the previous instructions with the heli running and inspecting the blades. Look at the path of the blades carefully. If they are rotating on the same path, no further action is required. If one is higher than the other, then apply tracking corrections immediately.
In the image to the right links C and D, connecting the top seasaw arms to the blade grips are used to adjust for regular/medium amounts of trim to blade tracking offset. E and F are to be adjusted if you need to trim out small amounts of deflection on the tracking.

The blade with the higher path has to much pitch. Lengthen links C or D, depending on which blade is out of track. As above, if it s slightly off track, shorten linkage rods E or F. Remembering if you want to keep the same headspeed as before adjustments, to bring one blade slightly down, and the other slightly up to meet in the middle.

If you have followed the CCPM setup, and this tracking guide, you should now have a good mechanical set up on your RC helicopter. Happy flying!


Sunday, 2 October 2011

Throttle and Pitch Curve Setup

RC Helicopter Pitch and Throttle Curves a Simple Guide

Introduction to Throttle and Pitch Curve Setup


Pitch and Throttle curves. People get to easily confused by this subject. It is mostly because they look for other peoples settings to use as there own, and don't truly understand the mechanics behind them. So when they don't work, they are unsure of what to adjust to rectify the problem, for instance if you are suffering from a low headspeed and "wagging" RC helicopter.
This subject is in fact very easy, and it just requires a little careful planning to get the perfect pitch and throttle curves for your RC helicopter. I will also briefly look at idle up pitch and throttle curves for the budding 3D pilot. My blog will list the latest RC helicopter guides and tutorials.
RC Helicopter Servo End Points
A little digression first, if you followed my previous guides, and in particular the mechanical setup guide. You will have seen we set the end points for the servo travel on the helicopter. It is useful to just spend a few minutes understanding how curves fit within those end points. When we have the servo travel set at 100%, we can increase or decrease that value, which then restricts or increases the servo travel. The pitch and throttle curves work within these pre-set end-points. So 100% at point 5 on a throttle curve corresponds to 100% servo movement if it is set to 100% as the end point, or 125% if set to this in the end point menu.

Graphical Helicopter Throttle Curve Menu 

So remember, pitch and throttle curves work within your end points. When we initially set up the radio system, we gave the pitch a linear curve. Normally most radios use a 5 point pitch and throttle curve, but some more advanced radios use a much higher granularity allowing for a higher resolution curve. So in a linear curve we have the 5 points corresponding to the 5 stick positions in a linear fashion. P1=0%, P2=25%, P3=50%, P4=75% and P5=100%.
How this information is displayed will depend on your particular hand-set. Some will display it as a visual graph, and also as you move the throttle stick, will also update the relative position on the graphs axis. Others will just list them as text, so P1, P2 and so on.

Pitch Curves
  After the mechanical setup, we arrived at a ±11° pitch range, with a linear curve this then means at P1 we have -11° pitch, and +11 degrees at P5, with a linear change between the two points. Crossing P3 at zero degrees pitch. It is possible to change these points to tailor how the pitch changes as we move the throttle stick. In normal mode we most certainly don't want -11° of pitch at zero throttle. But we do want this kind of pitch curve in idle up for 3D flying and upside down antics, but more on that later.

Graphical Helicopter Pitch Curve Menu
Getting back to end-points again briefly, we can use the throttle and pitch curves to set "fake" end points. So for instance if P1 is changed to 30% rather than 0%, then low stick now starts at a 30% value of the linear curve. So we will not get the full travel distance. This can be very useful. So with the pitch curve for normal mode flying you would make a higher starting point to make less pitch range between bottom and centre stick.
Changing P1 and P2 of the linear pitch curve, will allow us to reduce the negative pitch range of the helicopter. We are after a linear curve between P1 and P3, the same for the curve between P3 and P5, but at a different rate of increase. Ideally -3°, or -2° for P1, this means we wont slam the helicopter into the ground when trying to land, but also we need negative pitch to be able to bring the heli down in high winds.
The best way to set P1 and P2 is to use a pitch gauge. Attach it to the blade, and set P1 to when you read approx -3°/-2° of negative pitch. P3 will still be at zero degrees pitch, so set P2 halfway between the two. This is now your normal pitch curve Leave P3,P4 and P5 the same to match the idle up settings for these points. As the idle up switch is flipped whilst in the hover, so they need to match, usually at around 5°/6°. This normally corresponds to around ¾ stick for the hover.

Throttle Position Example Normal Pitch Values
P1 40
P2 45
P3 50
P4 75
P5 100
Throttle Curves
  In a RC helicopter, the motor doesn't always provide power in a linear fashion, especially electrics, the power band is normally quite high. If it was linear curve, it would match the pitch change exactly, which wouldn't work. If the rpm is low on the headspeed for the given pitch, we need a higher motor rpm to increase the head speed. As our pitch values are now set. (curve rising steeply then plateau). A symptom of low head speed is oscillating in the hover, we now adjust the throttle curve to give the correct headspeed at the appropriate stick position.
The idea now is to match the power band to the correct pitch, so at 11°, we need the maximum motor rpm, again we are in normal mode, so we need a curve with a high power band. Rising fast, and then levelling out, to provide the maximum power as loads are applied to the blades, and drag becomes a factor.
Ill give a "text book " example here, what we are looking for is for the throttle to ramp up sharply then flatten out. So this would be P1=0%, P2=50%, P3=80%, P4=90% and P5=100%. Remember as the throttle stick moves we are going through two curves, pitch and throttle. Both have an effect on lift, but our pitch values are fixed, so the throttle values are the ones that need "tweaking" in order to maintain the correct headspeed of the helicopter.

Throttle Position Example Normal Throttle Values
P1 0
P2 50
P3 80
P4 90
P5 100


Idle Up Throttle and Pitch Curves


So, now for the scary bit (although, it really isn't that scary!) idle up! So, eventually you will want to fly upside down. If you try that in normal mode you will have an expensive repair bill, and dented pride. So we need to adjust our pitch and throttle curves to take this into account, remember, we set the helicopter up mechanically to be able to fly upside down, but we did not allow for this in our normal flight mode. Luckily, modern computer radios allow you to have a second, and even sometimes a third set of curves, that you can swap to at the flick of a switch.

Idle Up: Pitch Curve
  So what we are looking for is the same amount of pitch but negative in the bottom half of the throttles travel as we have in the upper half for positive pitch, so lets say ±11°. This is simply our original mechanical linear pitch curve, this will allow for an equal amount of positive and negative pitch at the extremes of the stick movement. Set the idle up pitch curve to these numbers.

Throttle Position Example Idle Up Pitch Values
P1 0
P2 25
P3 50
P4 75
P5 100
Idle Up: Throttle Curves
Idle Up Pitch Curve  So as I said, we
need/want to fly upside down, and as pulling back on the throttle is now negative pitch, a linear curve on throttle would give zero throttle. We most definitely don't want this to be happening, in fact we want an increase in the motor to pull out from our manoeuvres as we press on through increasing negative pitch values.
This equates to a throttle curve looking like a "V" as we need the correct power from the engine at the appropriate pitch value. At mid stick, P3, we do not want 100% throttle, as there will be no load on the blades at zero degrees pitch, so we reduce the throttle here to stop the headspeed increasing like a banshee, we apply a linear increase either side of this, with P2 and P4 to match a linear curve. Similar to the normal mode, these values may need "tweaking" in order to get the correct head speed. We could also use a "U" shape, but the same theory applies and for this example we will concentrate on the linear increase either side of centre stick.
With these settings we will get an increase in rpm when the idle up switch is engaged, this is normal, and also the way it is normally kept. If this is unnerving, the throttle curves can be adjusted so at the ¾ stick position of the hover, when we engage idle up, they match to stop the slight and sudden jump in the helicopter.

Throttle Position Example Idle Up Pitch Values
P1 100
P2 95
P3 90
P4 95
P5 100
  So if you have followed the mechanical setup, radio setup, blade balancing, and blade tracking guides this should be the final step in the setup of the helicopters rotor head. The above examples are suitable for a wide range of RC helicopters, some may differ slightly, if in doubt, always refer to the manual, or a reputable on-line forum. You will find the members of this community more than willing to help you. Thanks for reading.


CCPM Mechanical Setup

CCPM Mechanical Setup





A good mechanical setup on the rotor head of a remote control helicopter, can be the difference between a model that almost flies itself, or one that is destined to hit the ground at high speed. OK, so they might be two extremes, but time invested now will be paid back ten fold. By the way, my blog will list the latest radio control helicopter guides and tutorials.

Radio Settings


First things first, start fresh on your transmitter, and select a brand new model channel, or if for some reason you don't have the luxury of multiple model memories, reset to factory defaults. This forces all trims to be reset, including the on stick ones, and sub-trims.

Some important tools for setting up the head on your rc helicopter
Go into your swash mix menu, and set the pitch, elevator and aileron to 50% swash mix. Set your swash type to 120 degree CCPM in the swash menu of the radio set (Yes, this "How to" is written for a 120 degree swash, from the swash up however, there are many similarities, so it will still be useful if you have a 90 degree swash). Lastly, make sure all other mix's are off, such as revo mix. Set all end points to 100% on the servo travel/end point menu.
Whilst setting up the helicopter head, we want linear throttle and pitch curves, so set these up now if this is not so. That is for the 5 stick points, 0%, 25%, 50%, 75% and 100% the throttle and pitch curves should match the stick values, going up linearly from 0% to 100%.

  Radio swash mix menu

Receiver and Servo Connections
Now, lets get everything connected. You may have all ready done this, but ill just skim over the essentials. I find it easier to use a standard receiver pack to power the servos and receiver whilst setting up. This saves having to incorporate the ESC and a LiPo. If you do choose the later option, ensure your motor wires are disconnected whilst working on the remote control helicopter. A good habit to get into, and essential for safety is to turn the transmitter on first, and then the receiver.
The servo towards the back of the swashplate is connected to the elevator channel on the receiver. The two forward servos can be connected to either the pitch or aileron channels on the receiver. Later mixing in the radio will sort out there orientations.

Servo Movement Directions
Now we need to get the servos and the swash moving in the rite direction. A modern RC helicopter CCPM swash is quite a complicated and confusing thing. But take some time and work carefully, and it most certainly isn't rocket science. The two tools we will be using are "servo reverse" and "swash mixing". The thing to remember is servo reversing works on only the servo in question. If you want to reverse multiple servo movements at the same time, you will need swash mixing.

Setup is based on servo horns being precisely aligned
The first thing to check is what happens when you move the control stick forwards on the cyclic. The swash plate should tilt forward. This means the elevator servo horn should rise. If it falls, and the helicopter swashplate tilts backwards, go into the reverse menu, and reverse the elevator channel. We want to do the same now for the left and right movement of the cyclic stick. It should tilt the swashplate left and right. As an example if we give full left cyclic on the remote control helicopter, the left hand servo horn should dip, and the right one rise, thereby tilting the swash to the left. If not, reverse the appropriate channels in the servo reversing menu.
Next, we want to see what happens when we increase the pitch, the whole swash should remain level (roughly, more on that later) and rise uniformly. If not, you will need to go into the swash mix menu, and reverse the value of the pitch entry, so if it is +50% change it to -50%. So to sum up, we need all 3 servo horns rising for up pitch, down for down pitch. Left cyclic should mean the left servo dropping and right rising, the opposite for right cyclic. Forwards elevator means the rear elevator servo will rise, and the forward pitch and aileron servos will fall.

CCPM setup, showing the alignment of the mixer arms on the helicopter
To correct a single servo use servo reversing, if all three are not moving in the correct order it can be corrected with swash mixing. We are now ready to move onto servo arm alignment on our remote control helicopter.

Helicopter Servo Arm Alignment 
Now it is essential to have followed the earlier instructions regarding correct initial radio setup. Make sure you have power to your servos, and the helicopter pitch/throttle is set to 50%, this needs to be as accurate as you can manage. You now need to get those servo horns on at 90 degrees. That is horizontal, or if you prefer, parallel to the ground. Now the grooves on these servo horns are not uniform, different horns, and different orientations will yield better results on your RC helicopters servos. Play around for a bit and get it as close as you possibly can.
Chances are you will have them nearly perfect, but not quite, that's OK, we can use sub-trims on the radio transmitter to correct for this. So head on in to the relevant section on your radio, and play around with the settings for each channel by a few notches until you can judge the arms to be at 90 degrees. A good tip is to line them up against the servo casing and use that to judge the alignment. Make sure to put the ball links on the inside of the servo horn, that is so the linkage will come between the servo horn and frame. Always remember to use loctite on these, as you don't want them coming loose during flight.

RC helicopter Swashplate leveling

Use the flybar cage to align the top seasaw mixer arms
Again, the pitch control should be at 50% for this step. I wont go into to much detail here, many people on many different remote control helicopters use different tools, tips, and techniques. Do whatever you feel is best. I do however recommend a swashplate levelling tool, they can be as cheap as a few pounds/dollars. The idea is, with the pitch at 50%, and all servo horns at 90 degrees, the swash should be perfectly level with the helicopter. If not use your tool, or judgment, and start adjusting the 3 push rods from the servos to the swash by a single turn, and re-measure. It is worth mentioning now always follow the manufactures instructions for the lengths of push rods as an initial starting point, some times they are spot on. Repeat this until the swash is completely level. You also now want to check that at 0% on the throttle/pitch stick on the transmitter the swash doesn't come down to far and hit the washout, also at bottom pitch, you should check the full range on the cyclic, as to make sure the swash doesn't hit the frame. If it does, raise the swash by turning all of the push rod linkages by the same amount, until these interactions are removed.
Now complete the construction of the rest of the head, as per the manufacturers instructions, up to but not including putting the blades on. Before moving on, you want a completely constructed head in order to set up precisely all the components. We will adjust out any irregularities.

Sea saw Mixer Arms
Some people think of this stage as being the hardest, but it is the simplest to be honest. Just take your time, and re-check your work. Essentially, all we are looking for is that the bottom and top sea saw mixer arms are nice and level when the swashplate is level and at 50% stick. To achieve this we need the flybar cage to be locked into position with an appropriate tool, an allen key as per Finless Bob, or judged bye. Arms needs to be straight and level with the bar of the flybar cage. This is achieved by adjusting the linkage rods going from the swashplate to the mixing arms at the top of the heli, lengthen or shorten to achieve the perfect balance.

The flybar paddles should be parallel to the edge of the flybar cage
Unlike the final push rods to the blade grip, these can be different lengths. It is an iterative procedure, where you adjust one set, see how it effects the sea saw arms, then re adjust. Each time getting smaller and smaller in adjustments until they are level. The top arms can be judged by lining them up with the flybar cage. The bottom ones by looking through the head to the arms on the other side, they should be parallel with each other and look at the alignment of the ball links on the mixer arms, repeat this on both sides.
The bottom sea saw arms can be adjusted uniformly by raising or lowering the swashplate linkage rods, applying the same amount of adjustments to them all at the same time, whilst the pitch is still at 50%.
Zero Pitch on Blade Grips
We would now like to achieve zero pitch in the blades at 50% throttle/pitch. This proceeds on the assumption your setup to this point is correct, including the aligned sea saw mixer arms. Put a set of blades on now. You will need to lock the flybar cage in position, check out Finless Bob's hack with an allen key to achieve this, or buy a tool, either way you need to have a steady and fixed flybar cage.

No pitch gauge? Easy, line it up by eye!
At this stage the blades should now have zero pitch, this can be measured with a pitch gauge, or judged by eye. If doing it by eye, and you have flat tops on the blade grips, you can line them up by eye, the flat edges of each blade grip being on the same plane as each other. You will need to take the button head of the top of the head. Another trick, is to take the blades of, and look at the bolt that goes through the blade grips that normally holds the blades on, this should be vertical.
If you have any pitch in the blades, adjust the very top most linkage rods to remove this, and re-measure. These rods should be identical in length, this is very important. So if one blade has more pitch than the other, something has gone wrong with your setup further down the head of the RC helicopter, so you will need to re-check this from the swash to the top mixing arms.

Checking Head Full Pitch Range
To do this put some blades onto the RC helicopter and measure the full pitch range over the full length of travel. Increase or decrease the pitch value on the swash mix. Taking note that the swash doesn't hit any of the other mechanics at the bottom or top of its travel. As we started with a swash mix of 50%, 70% should give roughly around 14 degrees of pitch. This will be a little to lively for a beginner. 60% swash gives about 11 degrees of pitch, which will be a good starting point for a RC helicopter pilot. As a reminder, when adjusting the full range travel on your helicopter, make sure the swash doesn't hit the washout or the frame during its travel. Similar to when we were adjusting our ranges in the sea saw mixer arm setup stage.

Another technique for getting zero pitch in the rotor blades

Flybar Paddles
I did notice when i was first starting out, that there wasn't much information on how the flybar paddles should be setup. Luckily, they are very simple. they should be of equal length from end to end on each side of the flybar cage. The leading edge pointing in the same direction as that of the blade (The paddles and blades should have there leading edger pointing in a clockwise direction by the way). Lastly they need to be flat and level, you can judge this by eye, line the paddle edge up with the top sea saw mixer arm, inside the flybar cage, they should be parallel to each other.

Checking for CCPM Interactions

It is best now to search for any CCPM interactions, this is due to not all servos moving the same amount, or linearly. This can be checked on the swash, but due to the mixing ratios, the paddles are much more sensitive to these interactions, so keep an eye on these while checking, you can use a small bubble level on one of them. Have the paddle perpendicular to the tail boom, and look for elevator interactions, do the same with it parallel to it to look for aileron interactions
When your pitch is at 50%, the helicopter blades should have zero pitch
If you spot any movements, go into end point adjustment section/travel adjustment section of your helicopters radio. So for instance if at full pitch the bubble moves backwards, apply an increase to the forward elevator end point in order to bring the bubble back to level, same goes for aileron interactions. You will still get in between CCPM interactions, but it is not overly important to fix these, getting full, bottom and centre the same is important, on digital servos we can get rid of this with P mixing but it is a task that is very time consuming.

Line the pitch gauge up with the helicopters flybar
The last step, reduce or increase pitch setting at max pitch in swash mix to get 11 degrees positive, if all links are correct at negative we should now have 11 degrees as well. This step is essential to finally check our setup. If more pitch is present in one direction, then something is wrong and we are getting some unwanted interactions, check and redo all of the links.

Cyclic Range
We are almost done now, and you will be able to breath easy. We want to adjust the amount of cyclic pitch available. Ideally we want 6 degrees in each direction, measured using a pitch gauge, the more pitch you have the faster the response of the model helicopter. As a beginner, you would be looking for a little less. As you have to add it to the total pitch of the blades in the first place.

Swashplate leveling tool
So if you have set your blade pitch range to +/- 11 degrees, you will now have a total pitch range of 17 degrees. Way to much for a beginner. As with this amount of pitch, collective management whilst flying will be a big thing. To adjust these ranges, use the radios swash mix, aileron and elevator mix to be precise, reducing the number reduces the throw of the swash, and the same for the opposite direction. You may have to experiment a little with this to get the right balance.
But if you have followed this guide word for word, you should now have a well set up, and ready to fly remote control helicopter. Good luck!


Saturday, 1 October 2011

Align Trex 450 Pro Super Combo Review and Build Guide



The T-Rex 450 Pro Super Combo is the top end Align RC helicopter. It shares very little of the core parts with the 450 Sport and 450 SE V2 varieties. Utilising a completely different frame design. Also it incorporates a tail servo built into the main frame, as opposed to being mounted to the tail boom.   It is aimed at the more advanced beginner or intermediate pilot due to its torque tube drive, as this provides more precise tail control, but also, increased costs in the event of a crash or boom strike. That being said, spares are plentiful, so this model can be enjoyed to its full potential without worry of high repair costs.
In keeping with the increased performance of the Pro version it comes with Aligns new more powerful motor, giving this little heli a very high head-speed, in excess of 3000 rpm. So it certainly has the power to allow the user to explore some more advanced routines. The performance will be talked about in greater detail later on in this guide, but for now it’s time to get on with describing the build and reviewing the model.


In keeping with the 450 Sport, Align are pre-building these models partially at the factory. With varying results, so it is imperative at the very least to check every meta-metal screw or bolt for loctite, and also to ensure that all bolts are tightly fastened. But more so, it is wise to strip the pre-built parts down (head, tail, frame) and start from scratch. This way we can ensure a successful build. Hopefully Align will stop doing this (as it takes longer to take everything apart) and pack it in the same way as the 500+ helicopters in its range. But obviously purchasing a pre-built ready to fly package will mean all of this has been done for you.


The 450 Pro goes together very well, with very little deviation from the manual. To that point, the manual itself is very good, clear computer sketches of the build process. The manual also serves as a good reference for any adjustments the owner needs to do during the lifetime of the helicopter. It also covers the setup clearly of the ESC and gyro.
Initially we start with the head. Again this is pre built mostly. But it is wise to go over each screw and make sure loctite has been applied and the screw is firmly tightened. The main points to consider at this stage are getting the flybar positioned correctly, so we have an equal amount of length on both sides of the head. Also, when screwing on the paddles, making sure that they are set to an equal distance as there counterpart on the opposite side. Otherwise vibrations may be evident leading to flight control issues. All of the control arms except for the upper mixers to swashplate are of fixed length and solid plastic. This removes any potential errors in measurements, and leads to a more accurate and pain free setup procedure later on.


Next we construct the frame. Again, removing all the pre installed bolts, and re-building the frame. The next part is very tricky if unaware of the mechanics and order of the build. The servos are arranged in such a way that if you are leaving the frame built as it comes from the factory. It is necessary to remove some bolts from the CNC servo supports, pivot them, and slide into place the rear elevator cyclic servo. As Align have incorporated the servo mounts into the bearing blocks. Otherwise it’s impossible to get into place. Another point is we should install the motor before the servos, as it is almost impossible to access the motor bolts with the cyclic servos in place.
We need to ensure the motor is in the rite position before securing. So at this stage we slide in the main shaft and attach the main gear. So we can line up the motor pinion with the main gear. Leaving a small gap between the teeth, so they don’t wear with the constant friction of close contact. Despite the tricky nature of this section, Align have done a good job in the design and construction of this section of the helicopter. Removing the front plastic battery holder also makes this part easier. The build is as expected much more involved than described, but described here are just some of the points that require a little extra care.


At this stage it is a good idea to do a large portion of the electronics install. As removing the frames bottom plate we have good access to the helicopters internals and we can route the cyclic servos to the front of the helicopter. Placing the ESC in the front of the helicopter under the battery tray. Installing the electronics at this point allows for a much neater installation as when the head, tail, and undercarriage is in place access can be tricky.
It is always a good idea to power up the receiver, either with a receiver battery pack, or via the ESC (remembering to unplug the motor cables) and check for the centre position of the servos, cyclic and tail. The servo horns can then be fixed in place knowing that they are at the central 90 degree positions, it also allows us to bind the receiver before replacing the bottom plate of the frame and sealing away the electronics. As with a small heli like this we need to make the most of all the space we have, and it is very limited on space.


The Pro version of the 450 includes a torque tube drive. This makes the construction of the tail easier in some ways. As we don’t have to worry about tail belts. But we must make sure the correct installation of the torque tubes bearings, otherwise we may experience stripped gears or incorrect operation. In the simplest form, it is applying some CA glue to the central point on the torque tube, and then sliding on the bearing (without dust cover) and fixing the bearing to the centre. Being careful not to get any CA glue on the bearing itself as we don’t want to hinder its operation. Next we need to apply the rubber bearing seating/dust cover to the bearing. We then coat this in grease, and ease it into the tail boom, sliding it into position.
The tail unit is checked for loctite and built as per the manual, it is then locked into place onto the torque tube. Remembering to slide on the pushrod guide rings before attaching the tail boom to the tail block on the main frame.


Now we have the tail in place and secure we can attach the head unit, sliding it into the bearing block and fixing the main gear in place with the supplied bolt. It should fit snug to the motor pinion, as we checked for this earlier. Also, as we checked for the servo centre positions, we can go ahead and attach the control rods from the swash to the servos. During the build we set them to the length given in the manual. This can be adjusted later whilst setting up the helicopter.


The gyro is placed in position at the top of the helicopter on the provided mounting platform by the swash guide. Mounting of the tail servo is straight forward, two of the screws supporting its mounting can be removed and it then pivots out to allow the servo to be screwed in place.                     


So with the build almost complete, the overall construction and quality of the components is exceptional. All parts go together well, and are of a high quality. A good tool set is essential, as using wrong size hex keys can strip the bolts. Now we just need to set up the helicopter, and then we can look at its flight characteristics.



Setting up this helicopter is very straightforward, the supplied blades are made of good quality carbon fibre, and the supplied set required no changes during balancing. With the suggested pushrod link lengths the swash is near perfect, requiring only minor adjustments to make it level. As mentioned before, due to the majority of the links being a fixed length, there is little room for error. Spinning the helicopter up and checking the blade tracking reveals an almost perfect track. Requiring just a turn of one of the pushrods in order to bring it into line. Remember, blade tracking is a very dangerous job, so always wear suitable eye protection. As mentioned before though, with any pre-built package all of these setup procedures will already be complete.


The T-Rex 450 Pro, once complete and mechanically setup requires some programming of the radio, and then it is ready for flight. Giving it a gentle pitch and throttle curve will result in a nice flying experience for the beginner. More aggressive curves will give a crisper 3D experience.


The ESC comes ready to fly from the factory with the default settings suitable for this model and for all round flight. To confirm, double checking  the audible cues at start up before spooling up the model. It’s also worth noting that the audible beeps are only heard with the motor plugged in, as it generates the noise. The gyro is very easy to setup, requiring very little input except for setting the servo travel distances and making sure the direction is correct.  


The Align T-Rex 450 Pro is quite rightly not a V3 of the original 450 design. It is a whole new beast. To that end Align have done a good job, producing a lovely little model, with much bigger aspirations. The quality of the build is excellent, and the helicopter performs excellent out of the box. That is literally the case, all that is needed is a receiver, transmitter and battery. The rest is supplied in the super combo.


Due to the new more powerful motor being used it has ample room for performance flight. A seasoned veteran would get just as much use for this as the beginner. The supplied Align GP750 Gyro and 35A speed controller are a good pairing, providing a reliable electronic basis. Pairing this with a Helicommand unit (as shown in the photos) can give the ultimate beginner platform, super stable and not requiring massive amounts of land to fly it in.
The actual flight performance should be good, the 450 Pro was designed by Jason Krause, so it happily pumps out the power even at +/-15 degrees of pitch the head doesn’t get to bogged down and remains responsive. The value of the super combo deal is also very good value when comparing it to the costs of buying the items separately. All in all a superb all rounder, and sure to give hours of enjoyment.



Friday, 30 September 2011

Controlling a helicopter

Controlling a Helicopter

Helicopters require a completely different method of control than airplanes and are much harder to master. Flying a helicopter requires constant concentration by the pilot, and a near-continuous flow of control corrections.
A conventional helicopter has its main rotor above the fuselage which consists of 2 or more rotor blades extending out from a central rotor head, or hub, assembly.
The primary component is the swash plate, located at the base of the rotor head. This swash plate consists of one non-revolving disc and one revolving disc mounted directly on top. The swash plate is connected to the cockpit control sticks and can be made to tilt in any direction, according to the cyclic stick movement made by the pilot, or moved up and down according to the collective lever movement.
But first, to explain how the main rotor blades are moved by the pilot to control the movement of the helicopter, we need to understand pitch.

The basics of pitch

Each rotor blade has an airfoil profile similar to that of an airplane wing, and as the blades rotate through the air they generate lift in exactly the same way as an airplane wing does [read about that here]. The amount of lift generated is determined by the pitch angle (and speed) of each rotor blade as it moves through the air. Pitch angle is known as the Angle of Attack when the rotors are in motion, as shown below:

This pitch angle of the blades is controlled in two ways - collective and cyclic.

Collective control

The collective control is made by moving a lever that rises up from the cockpit floor to the left of the pilot's seat, which in turn raises or lowers the swash plate on the main rotor shaft, without tilting it.

This lever only moves up and down and corresponds directly to the desired movement of the helicopter; lifting the lever will result in the helicopter rising while lowering it will cause the helicopter to sink. At the end of the collective lever is the throttle control, explained further down the page.

As the swash plate rises or falls, so it changes the pitch of all rotor blades at the same time and to the same degree. Because all blades are changing pitch together, or 'collectively', the change in lift remains constant throughout every full rotation of the blades. Therefore, there is no tendency for the helicopter to move in any direction other than straight up or down.
The illustrations below show the effect of raising the collective control on the swash plate and rotor blades. The connecting rods run from the swash plate to the leading edge of the rotor blades; as the plate rises or falls, so all blades are tilted exactly the same way and amount.
Of course, real rotor head systems are far more complicated than this picture shows, but the basics are the same.

Cyclic control

The cyclic control is made by moving the control stick that rises up from the cockpit floor between the pilot's knees, and can be moved in all directions other than up and down.
Like the collective control, these cyclic stick movements correspond to the directional movement of the helicopter; moving the cyclic stick forward makes the helicopter fly forwards while bringing the stick back slows the helicopter and even makes it fly backwards. Moving the stick to the left or right makes the helicopter roll and turn in these directions.
The cyclic control works by tilting the swash plate and increasing the pitch angle of a rotor blade at a given point in the rotation, while decreasing the angle when the blade has spun through 180 degrees.

As the pitch angle changes, so the lift generated by each blade changes and as a result the helicopter becomes 'unbalanced' and so tips towards whichever side is experiencing the lesser amount of lift.

The illustrations below show the effect of cyclic control on the swash plate and rotor blades. As the swash plate is tilted, the opposing rods move in opposite directions. The position of the rods - and hence the pitch of the individual blades - is different at any given point of rotation, thus generating different amounts of lift around the rotor disc.

To understand cyclic control another way is to picture the rotor disc, which is the imaginary circle above the helicopter created by the spinning blades, and to imagine a plate sat flat on top of the cyclic stick. As the stick is leaned over in any direction, so the angle of the plate changes very slightly. This change of angle corresponds directly to what is happening to the rotor disc at the same time ie the side of the plate that is higher represents the side of the rotor disc generating more lift

Rotational (yaw) control

At the very rear of the helicopter's tail boom is the tail rotor - a vertically mounted blade very similar to a conventional airplane propeller. This tail rotor is used to control the yaw, or rotation, of the helicopter (ie which way the nose is pointing) and to explain this we first need to understand torque.

Torque is a natural force that causes rotational movement, and in a helicopter it is caused by the spinning main rotor blades; when the blades are spinning then the natural reaction to that is for the fuselage of the helicopter to start spinning in the opposite direction to the rotors. If this torque isn't controlled, the helicopter would just spin round hopelessly!
So to beat the reaction of the torque, the tail rotor is used and is connected by rods and gears to the main rotor so that it turns whenever the main rotor is spinning.
As the tail rotor spins it generates thrust in exactly the same way as an airplane propeller does. This sideways thrust prevents the helicopter fuselage from trying to spin against the main rotor, and the pitch angle of the tail rotor blades can be changed by the pilot to control the amount of thrust produced.

Increasing the pitch angle of the tail rotor blades will increase the thrust, which in turn will push the helicopter round in the same direction as the main rotor blades. Decreasing the pitch angle decreases the amount of thrust and so the natural torque takes over, letting the helicopter rotate in the opposite direction to the main rotors.
The pilot controls the pitch angle of the tail rotor blades by two pedals at his feet, in exactly the same way as the rudder movement is controlled in an airplane.
NOTAR is an alternative method of yaw control on some helicopters - instead of a tail rotor to generate thrust, compressed air is blown out of the tail boom through moveable slots. These slots are controlled by the pilot's pedals in the same way as a tail rotor is. To generate more thrust, the slots are opened to let out more air, and vice versa.
NOTAR helicopters respond to yaw control in exactly the same way as tail rotor models and have a big safety advantage - tail rotors can be very hazardous while operating on or close to the ground and in flight a failing tail rotor will almost always result in a crash.

Throttle control

The throttle control is a 'twist-grip' on the end of the collective lever and is linked directly to the movement of the lever so that engine RPM is always correct at any given collective setting. Because the cyclic and collective pitch control determines the movement of the helicopter, the engine RPM does not need to be adjusted like an airplane engine does. So during normal flying, constant engine speed (RPM) is maintained and the pilot only needs to 'fine tune' the throttle settings when necessary.

There is, however, a direct correlation between engine power and yaw control in a helicopter - faster spinning main rotor blades generate more torque, so greater pitch is needed in the tail rotor blades to generate more thrust.

It's worth noting that each separate control of a helicopter is easy to understand and operate; the difficulty comes in using all controls together, where the co-ordination has to be perfect! Moving one control drastically effects the other controls, and so they too have to be moved to compensate. His continuous correction of all controls together is what makes flying a helicopter so intense. Indeed, as a helicopter pilot once said... 
"You don't fly a helicopter, you just stop it from crashing"!