GV-1 Basic Tips
Rotor rpm will change how a model helicopter performs and feels. A constant rpm will yield a constant feel. Because a higher constant rotor rpm will give more stability and extra cyclic control power for an aggressive flying style, in flight rpm adjustment may be desired. An rpm set to allow the engine to operate at its torque peak will give smooth and powerful operation. A good helicopter design must have the engine rpm accurately matched to the rotor speed by means of a correct gear ratio. Since the engine is governed and directly connected to the rotor both become controlled as one. Only rudimentary pitch and throttle curves are needed since the governor takes care of maintaining the selected rotor speed.
This GV -1 gizmos is meant specifically for controlling engine rpm to a value the operator has decided upon. It can store more than one rpm value all of which are user selectable from the radio transmitter. These three values are stored and programmed into the GV -1 memory by the user. The GV -1 can also be setup to give restricted variable rpm using an adjustable knob on a radio transmitter in conjunction with a free associated channel. In this case the endpoint rpm numbers stored in the GV-1 will determine the adjustable rpm bandwidth relative to what the knob does with the ATV.
Many helicopters use pitch and throttle curves to maintain a constant rpm with good engine loading. This method however cannot compensate for all flight situations due to rotor loading from changing G force and angle of attack. The blade angle of attack changes with the angle of the air flowing through the rotor and G loading also will change with the mass of air flowing through it. It is not just a blade pitch angle thing and becomes quite complicated at times. These are facts which I will not go into detail now, but suffice it to say through example that engine loading at negative pitch is different climbing out inverted as compared to falling right side up. With the normal pitch/throttle setup adjusted correctly the machine can still sometimes over or under speed due to changing conditions. A safe and correct rpm control will also mean the rotor system is not subjected to strain. Another very important result for the advancing model aviator using this governor is that no cyclic to throttle mixing will be needed to prevent rotor speed decay during aggressive cyclic manouvres.
The GV -1 was designed with everyone in mind, from the poor to the affluent. It will operate with the cheapest of radios or with the most expensive. By using a better radio you are able to have or access more features. In any case a constant rpm will be available no matter what radio you fly. The GV -1 will work with most popular radios provided the correct servo wiring is adhered to. Servos can be rewired as can the GV -1 plugs, or aftermarket adapter harnesses may be purchased.
The GV -1 manual is initially speaking not the best at explaining setup matters, but seems fine as a reference once you understand the device. For the average flyer starting out things like the mixture, battery failsafe, governor cutout features can and should be turned off at the unit.
The gear ratio for the specific helicopter, needs to be set in the GV -1 so that the numerical values on the display are indeed accurate. If this is not set accurately then the rpm will be governed or controlled to some unknown value.
The governor can be turned on and off using two programmable methods. The throttle servo signal position or the use of an aux/on/off channel switch may be used. To further complicate matters another input called the aux rpm input at the GV -1 can be used to alter rpm while the aux on/off input does only that…..on or off. The aux rpm input can also be used to turn the GV -1 off and vary rpm. This causes the same result as the on/off aux input but is simply performed by a different method. The reason for this is to free up the aux/on/off input of GV-1 should a mixture servo be installed.
There are various monitor functions to check for when or where the governor will be activated on and off. There is only one monitor function that checks all governor on/off switching and this is the one to pay attention to prior to operating the system. It is called SWCD . If you can only remember one thing this is it.
As can be reasoned the maximum number of rpm features or switching available will depend on your radio. The switch layout of you radio, the spare channels available and whether it has a variable knob for a spare channel will determine exactly what you can do with this governor.
Again, the governor has the ability to store three rpm settings internally which are programmed by the GV -1 keypad. By manipulating the ATV on the aux rpm channel using the radio transmitter we can actually vary the rpm with a dial or knob. By using only a three position switch with the aux rpm input we can access all three speed settings or two speeds with on/off switching.
Rather than wasting time on extensive installation details I suggest you follow the manual here. I encourage you to achieve a 97 flux or sensitivity setting by correctly mounting the speed pickup.Verification is at the GV-1 display screen labeled sen. Make the air gap no smaller than necessary to achieve this result as the magnets in the fan may rub and cause damage. A plastic fan can droop or flex under high rpm and thus reduce the clearance. Only one magnet needs to be installed and it is polarity critical because it has a “this side up”. The small imbalance will not be effective so save the other magnet for a spare. Mark the magnet before installing it using the sen screen to locate the outboard side. CA or standard epoxy works fine for bonding the magnet into plastic and metal fans. Stay away from ferris metal reinforced epoxies like JB Weld. Aluminum reinforced epoxy is fine though. Installing the unit in foam or on a velcro cushion will protect it from vibration. CSM gyro mounting tape is a very good alternative for this purpose.
The throttle servo should have the widest ATV possible and if this is not the case then adjust the mechanical linkages to meet this requirement. You should be doing this anyway with all model helicopter throttles. The system will still operate as low as 50% throw but resolution, setup adjustment flexibility, and accuracy might suffer.
The machine should fly fairly well on all flight modes in case the governor ever fails or turns off unexpectedly. You require a back up.
The following deals with the most basic setup. Should you need to install the unit on a system with no free radio channel then only two connections need to be made. The throttle servo will plug into the unit and the unit will plug into the throttle slot of the radio receiver. The speed you govern at will be set at screen rS2. Your gear ratio is configured at screen GRT. Go to Lmt screen and set idle, high and stop using the throttle stick and key pad. These points program the GV-1 exactly to your throttle ATV settings. This makes sure full servo travel or throttle values are used by the governor and that no over travel with binding occurs. It also sets the on/off throttle stick switching point. If you try to set the idle and stop points too close together or the idle lower than the stop an error will occur. Less than 50 % ATV will do the same thing. The Tst screen verifies travel volumes at the servo. Finally verify correct on/off switching at SWCD and ensure that in flight the throttle is set above the off point at all stick positions. The correct adjustment of the lowest idle-up point (or flight mode throttle curve) on you radio will assure this. Remember the thing is stupid and only does exactly what it is told. The throttle hold will automatically disengage the governor provided its throttle hold point is as low or lower than the governor off point set into the GV-1 during the throttle limit programming. Use the all important SWCD screen to check operation. The screen StSW must be set to INH to use the lower throttle stick position for governor on/off switching which is based on your limit settings. If you activate StSW in the unit then governor on/off switching will occur at about a half throttle stick non adjustable position. The idle up lowest point will need to be set higher to keep the governor turned on. What it comes down to is one method will allow you to turn the governor off with the throttle trim on the normal curve while the other will not…. or one allows you to select the on/off point while the other method has it fixed. In any event the governor will not acticvate until 70% of the programmed rpm is reached and the SWCD reads on.
When engaging the unit there may be a delay since the device needs to be at least 70% of the set rpm to come on. It also has a soft engagement delay that can cause it to appear to turn on at different stick positions depending how quickly rpm is brought up and if the engine is loaded rich prior to clear out to normal lean operation (warm up). Another reason for rudimentary pitch/throttle curve setup and good carb mixture settings. If using the StSW feature then the machine should be brought up to switching point (about hover) before the idle up is engaged to prevent an rpm spike.
Problems can occur if the engine is naturally unstable or an exhaust system causes it to become so. This will manifest itself as hunting or torsional oscillations. Sometimes changing rpm settings will remove the problem. Incorrect engine installations will cause trouble too. Running a 46 engine in a 30 machine with 30 sized blades is opening the door for problems. So basically if your machine is screwed up in these regards the governor will not unscrew it..
Some other old technology governors for models are shown that I have used. The Helimax unit samples rotor speed at the main gear while the Throttle Master senses engine rpm similar to the GV-1. The GV-1 is the best of the three, offering the most accuracy and best flexibility. The GV-1 works very well on both the glow and the gasoline powered machines. Futaba manual may be found here: http://www.futaba-rc.com/manuals/gv-1-manual.pdf
Since this was article written other products have entered the market with even better performance!