A governor is a device used to maintain a constant engine speed and since the engine is connected to the rotor its rpm remains constant too. The big virtue of a stable rotor speed is a very predictable feel to the model helicopter controls. Everyone strives for this result through complicated pitch/throttle curve relationships. Add to this the cyclic to throttle mixes and the setup recipe can become complicated. If the helicopter is allowed to vary in rpm then the tail rotor thrust will vary since it is after all connected through the gear train. What this means is that the gyro must fight the rpm induced thrust changes plus all the other things it normally compensates for. If we remove but one variable then the gyro performance will improve.
The governor looks at one thing, rpm and for the most part it cares not what kind of G loadings the rotor sees. A normal or conventional setup cannot because its loading depends on gravity. If we climb under full power with a constant rotor rpm and then flip inverted with the same collective value then the rotor will over speed as the helicopter heads for the ground upside down. One situation is aided by gravity while the other is opposed. Often expensive tuned exhausts are used to control this issue along with piloting skill.
The practical benefits of the governor are less setup time, consistent setup under changing atmospheric conditions and often it can be an economically sound purchasing decision. Less setup time means more play value for the experienced flyer, lower tuning complication opens the hobby to those with limited setup skills and radio equipment. You will often hear some experts suggest that governors are not needed and that they refuse to use one. This is certainly true but many of us are not experts and prefer to concentrate on honing our flying skills and enjoy the hobby with the least amount of setup hassle. The performance value the modern governor affords places the helicopter very close to an expert setup.
The TJ engine governor is the latest governor to hit the market place. It does one thing, efficiently manage rpm. Sensing is by means of a hall sensor which is unaffected by ambient light as are optical devices. The rpm sampling is at the engine since its speed is highest. What this means is that by controlling a relatively wide rpm band will yield a very small change in rotor speed. If we have a 10:1 ratio then a 100 engine rpm variance will show up as a change of 10 rotor rpm. It is easier to directly manage 200-500 rpm than it is 20-50rpm. It is healthier to control rpm at the source. This also removes any possible issues with clutch slippage and gear train flex or give.
This governor installs electrically between the receiver throttle output and the throttle servo. It also requires a second channel to allow on/off switching and/or in-flight rpm changes. We sometimes like to change the rotor speed and go from a mild to wild flight mode. A higher rotor speed offers a faster more powerful cyclic and collective control. The ATV value of the second channel is adjusted to alter the governor rpm. This channel may use a switch or a variable knob, either choice will work.
Once you decide what rpm feels best then the ATV value may be left alone. Most people select a moderate speed for hovering and graceful flying and the high rpm setting for 3-D. If you have a three position switch you could have three speeds or two speeds and off.
The TJ governor works as well as the best on the market by anticipating a rate of change based upon historical data. By learning from the engine response resulting from governor corrections a more accurate rpm control is possible. One could accurately call it adaptive. What this means is that the governor becomes flexible in all installations and flight situations. The governor will also adjust to a flying style by virtue of its microprocessor. Practical benefits are a tighter rpm band width and with a quick response.
Some governors have fixed servo travel volumes and so the linkage setup becomes rather tedious to avoid binding and still allow full throttle travel. The Vario, Helimax and other governors come to mind. The TJ avoids this issue and adjusts its internal ATV to your setup during the initial installation. This is one reason why the Futaba GV-1 is so popular. Once stored the TJ needs not be setup again unless you change the throttle linkage. The magnet installs into the engine cooling fan and the hall sensor mounts to the engine mounting bolts using the supplied bracket. The control unit is tiny, taking little space and weight. The hall sensor is larger than the Futaba but has no case surrounding it so it actually looks smaller. Care is needed during installation since it is not contained in a protective case. This care amounts to radius bending of the wires and potting them to the mount with RTV. This reduces solid wire strain, holds them in position plus offers good vibration isolation. Using the other side of the hall sensor will allow operation with a previously installed Futaba magnet. Using two magnets in the fan allows lower rpm four-stroke operation. Magnets may be installed with C/A glue after cleaning with lacquer thinners.
The control unit has two LEDs one for entering the setup mode during boot up by way of toggling the aux switch and the other for checking the sensor air gap. The TJ instructions take one easily through a painless installation.
We compared the TJ to the popular top end Futaba GV-1 governor simply because it is the best unit on the market and the most expensive. While the TJ may not have as many bells and whistles it does perform at the same level so far as a governor goes. We verified measurements using two different engines/helicopters using both devices. This was done using a MA Skytach during various flying styles. While the GV-1 seemed a bit better in one regard the TJ excelled in another. So rpm comparison wise, we ended up with a stale-mate.
The TJ needs a completely free channel so if running a 6 channel system with a HH/normal gyro you will run into conflicts. Another single but variable speed TJ unit is available. Your choice is to either use a GV-1 or a single mode HH or a normal gyro with the TJ.
The TJ is small, cheap to buy, simple to use and big on governor performance. Acquire it for those reasons.
The TJ sensor may be economically adapted to the Futaba GV-1 if need be by the addition a 1K ohm resistor. The GV-1 sensor has an above average failure rate at the sensor casing and often these cases are hard to acquire. This is the main reason for the populatity of the after market optical sensors. The single resistor goes across the white and red wire on the TJ sensor. Thanks go to Paul Beard the manufacturer of the Throttle Jockey for this bit of helpful information.
· When using the Throttle Jockey for the first time or making changes to the throttle servo throw always perform the calibration operation.
· Always perform a range check after installing the Jockey.
· When starting the model, always keep the throttle below 25% to ensure that the jockey does not regulate the throttle.
· Set the failsafe of the throttle channel to the stop position of the engine.
Model Avionics “Throttle Jockey” Instructions.
The Throttle Jockey is a digital speed regulator for Model Helicopters. It uses an adaptive feed-forward control algorithm to regulate rotor speed. The Jockey monitors and regulates engine speed. There are two types of rotor speed regulators, ones that measure rotor speed from the main gear and ones that measure rotor speed from the fan. The main gear measuring regulators suffer from over speed any time the rotor system is unloaded. Engine shaft regulators in an unloaded rotor system will keep the engine speed constant. The Jockey continuously adapts to the response of the engine and the demands of the pilot. Aggressive throttle commands cause the Jockey to underdamp the control loop yielding a fast response to changing loads and slowly changing throttle command cause the Jockey to overdamp the control loop yielding a smooth response to changing loads.
The Jockey employs a pulse filtering system that cleans up any hits or glitches on the auxiliary and throttle channels if used on an FM system, but for best results use a PCM system.
The jockey is designed to regulate the engine speed between 9500 and 18500rpm.The actual head speed can be calculated by dividing the engine speed by the main gear ratio.
Rotor rpm = engine rpm / gear ratio
For example, a 9:1 gear ratio would yield a regulated head speed range of 1055 to 2055 rpm.
The modelavionics website (http://www.modelavionics.com) includes the latest information, setup tips and an on-line ATV calculator.
The jockey has 2 input channels, one for the throttle and for an auxiliary channel. The auxiliary channel is used to disable regulation and set the target regulation speed. The lead nearest the label is the Throttle connection to the receiver and the lead furthest from the label in the Auxiliary channel connection to the receiver. These connectors are compatible with both JR and Futaba receivers. On Futaba receivers, the brown wire should be oriented in the same polarity as the black wire.
The jockey has a sensor input and a throttle servo output. The header nearest to the label is the sensor input and the header furthest from the label is the throttle servo output. Note the polarity of the headers. On JR servos, the brown side of the lead should be oriented with the black square on the label.
During calibration, the Jockey measures the limits of the auxiliary and throttle channels. Once calibrated, the Jockey stores the measurements in non-volatile memory.
Calibration only needs to be performed when first installing the Jockey, changing throttle servo throws or after transferring the Jockey to a new machine.
· Setup the throttle servo operation so the travel (ATV) is a close to +/-100% as possible. Set the throttle curve to be linear.
· Set the Aux travel (ATV) to +/-100%, make sure that any mixing to the Aux channel is turned off.
· Set the throttle and trim to the low (stopped) position <- Important!
· Turn on the transmitter and then turn on the receiver.
· During the first few seconds of operation toggle the aux switch a couple of times.
· The green LED will flash indicating that the jockey has entered its calibration phase.
· With the throttle trim all the way down raise and lower the throttle then cycle the aux switch a couple of times.
· The jockey will extinguish the green led indicating that it has measured and stored these parameters.
To verify operation the throttle servo should operate normally. Verify the regulation enable threshold by raising the throttle stick above 25% of its travel and observe the green LED. It will illuminate indicating that regulation is enabled.
Aux channel operation.
The aux channel is usually assigned to a slider, pot or two or three position switch. The ATV of this channel controls the active state of the Jockey as well as the target speed. If the ATV in either direction is set to less than 5%, regulation is disabled. An ATV setting between 5% and 100% sets the target speed. 100% ATV is the highest target rpm (18500) and 5% ATV is the lowest rpm (9500). To verify operation, raise the throttle above the 25% threshold and lower the active ATV of the auxiliary channel below 5% and verify the Green LED is off. Alternatively, the ATV at each state of the aux switch can be used to set a different speed target. ATVs greater than 5% set the target rpm. 6% corresponds to 9500 rpm and 100% corresponds to 18500 rpm. On some radio systems, the auxiliary channel can be mixed with the flight mode switch. Different ATVs (or speeds) can be assigned to each flight mode setting using this method. Set the PCM failsafe to 0% for this channel.
Throttle channel operation.
Make the servo operating range as close to +/-100% ATV as possible.
Use backup throttle curves.
Set the flight mode/stunt/idle up minimum throttle settings greater the 25% so that regulation is enabled at all stunt throttle stick positions. (note that regulation can still be disabled using the aux channel).
Make sure that the engine can idle reliably when the throttle stick is below 25%.
Set the throttle hold below the enabled threshold so that regulation is automatically disabled during autorotations.
Set the PCM failsafe to the stop position of the engine.
Regulation is enabled only after all the following conditions are met:
1. The jockey has been calibrated.
2. The throttle is raised above 25%
3. The active auxiliary state ATV is above 5%
4. The engine has reached the target speed for more than 1 second.
The jockey uses a magnetic hall-effect sensor. The magnet is installed on the cooling fan of the engine and the sensor is attached to a bracket which attaches to one side of the engine mount.
Use the supplied Heat Shrink tubing and tie wraps to mount the sensor to the bracket. A dab of Cyno can be used to secure the sensor and tie wraps once the position has been set. The sensor is carefully bent over the top of the bracket with the writing on the sensor facing the fan (Note: The most sensitive side of the sensor is the side with the writing, however, if you have a magnet installed from a previous Futaba GV1 setup, the Jockey sensor needs to be oriented with the side without the writing facing the magnet).
The magnet should be mounted on the underside of the fan at a radius of 28mm (60 size) or 23mm (30 size) from the center of the fan. Drill a 4mm hole 1.5mm deep and epoxy the magnet to the fan. Do not use metallic epoxy such as JB-Weld, it will lower the performance of the magnet. Use a good epoxy with a 20min or greater curing time.
The sensor must be mounted a close to the magnet as possible. The sensor must be less than 2mm away from the surface of the magnet. The sensor is only sensitive to one pole of the magnet. To check the correct orientation of the magnet, connect the Jockey to the receiver and turn on the transmitter, connect the sensor and pass it in front of the magnet. The Red LED will toggle as the sensor detects the magnet. After installation, this method can be used to periodically check that the sensor and magnet are in range.
After power-up, the Jockey enters a 2 second boot sequence waiting for a toggle on the auxiliary channel. A toggle on the aux channel will cause the Jockey to enter the calibration sequence. Normally the Jockey will enter an idle state monitoring the sensor, throttle and auxiliary channels waiting to be enabled. Once enabled the jockey waits for the engine to reach the target speed set by the auxiliary channel state ATV. After 1 second, the Jockey will slowly and smoothly take over the throttle channel, regulating the engine directly. If the target speed is changed (by changing the aux state setting), the Jockey will acquire the new speed target setting. During regulation if the sensor malfunctions or the throttle falls below 25% or the aux setting is changed to less than 5%, the Jockey immediately and abruptly disables regulation, passing control back to the receiver.
Rules of regulation engagement.
The Jockey will only enable regulation after ALL of the following conditions have been met:
1. The Sensor, Throttle and Aux channel are operating correctly AND
2. The Jockey has been calibrated AND
3. The Throttle stick is above 25% AND
4. The AUX ATV is greater than 5% AND
5. The target speed has been reached.
After regulation has been enabled, the Jockey will pass control back to the throttle channel if ANY of the following conditions occur:
1. The Throttle stick is below 25 % (Throttle stick priority) OR
2. The sensor fails OR
3. The AUX ATV is less than (Auxiliary disable) 5%
Four-stroke engine setup.
Four-stroke engines run about half the speed of a two-stroke engine. Two magnets can be installed 180 degrees apart on the fan. This will cause the Jockey to regulate at half the setpoint rpm (4750 to 9250 rpm).
Regulation range: 9500 to 18500 rpm engine shaft speed. 4-stroke: 4750 to 9250 rpm
Control System: Adaptive, digital Feed-Forward
Resolution: 0.04Hz (2.26rpm engine speed)
Operating Voltage range: 3.56 – 8V
Operating Temp range: -40 to +85 degress C
Current Drain: 17mA @ 4.8V
Command oversampling: 8X
Nominal command: 1510us
Absolute range: 900us to 2200us
Disclaimer and Limitation of Liability
Specifications subject to change without notice.
Model Avionics shall have no liability or responsibility to the customer or any other person or entity with respect to any liability, loss or damage, caused or alleged to be caused, directly or indirectly, for equipment sold or furnished by Model Avionics.
Notwithstanding the above limitations, Model Avionics liability for damages incurred by customers or others shall not exceed the amount paid by the customer for the particular equipment involved.
Neither Model Avionics nor this document makes any expressed or implied warranty, including, but not limited to the implied warranties of merchantability, quality or fitness for a particular purpose.