Wayne Mann
Senior Heliman
Location: United States of America
| Hi Tabb,
I will assume that your Jokers are electric powered? Also you didn't mention what servo that you are using, but one of the biggest improvements that you can make is to install a BLS251 brushless servo. These servos are as much of an improvement in tail rotor holding performance over the S9256 as the S9256 was over the S9251. The biggest difference in holding ability that you will see is when the model is sitting sideways to the wind. Typically the tail rotor wants to bounce back and forth with wind gusts. The better the servo on tail rotor, the less bouncing you will see. One my 06 Caliber 90s with the StaySee fuse, the tail rotor would bounce back and forth quite a bit with the old S9251, but it got dramatically better when I switched to the S9256 and when I went to the BLS251, the bouncing all but went away. The added benefit the BLS251 should be a lot longer life span and a lot less heat build up which destroys the brushed servos.
The next thing I would recommend you trying is to cut down your servo arm so that you can run more gain. 37% is a very low gain unless you are doing 3D type flying and you are trying to keep from killing servos. AP flying is generally not very hard on servos. With that being said I still run two tail rotor servos on my Kyosho Caliber ZG with them mounted on the boom, one in front of the other and mechanically linked together via push pull. Keep in mind that that is with two S9256 servos. I have not upgraded to BLS251 servo on the camera ship, yet. I am not sure if I will drop back to one servo with the brushless servo or not. I do not have enough time on the brushless servos on my contest machines to determine just how bullet proff they are. A tail rotor servo is the most likely servo failure that you have on a helicopter. The second would be the throttle servo on a gas machine. Anyway back to the subject. Most of the top F3C contest pilots use 90 to 95% gain for hovering and around 60 to 75% gain in aerobatics, depending on head speed. Also keep in mind that we typically run a two speed set up. Our hovering head speed is usually in the 1400 to 1550 range and our aerobatic head speed is between 1850 and 2100 for some of us. I find my Caliber ZG with a 800 mm long Rotor Techs is happist at around 1550. With a head speed of 1550 my Caliber is running 85% gain. It will tolerate 95%, but I back it down some to keep any visible twitchyness out. With a 37% gain you have a lot of mechanical gain in the system which also multiplies any free play or slop in the control system and puts a lot more load forces back into the servo due to the increased leverage that the system has over the servo when using a long servo arm. Gear sets and ourput shaft bearings will live longer with a shorter servo arm.
Next I would switch fromt 3D mode to F3C mode in the gyro. It will hold just as well without being so agressive around center.
Next I would recommend turning down your control power in the AFRs and turning up the expos. I don't know how your ships are set up, but as an example my Caliber ZG is set up on a buddy box system with two Futaba 14 MZ radios. When we are ready to shoot video or stills I get the model in position and once the camera man is ready, I flip one switch. This switch does many things. It turns on the gyros on the camera mount, gives the camera opperator control of the camera mount and gives the camera opperator control of the tail rotor. My self design camera mount does not have pan, it only has roll and pitch, with gyros. In MY opinion using the tail rotor for pan is a lot more precise than a mount with pan abilities. Unfortunately this puts a lot more strain on the pilot because he has to be able to fly the helicopter in forward flight with the helicopter traveling sideways and sometimes backwards. Depending on the speed of travel this can get interesting. Anyway we used to use a mount with pan control and one day I showed up at the field to begin preparations for an upcoming shoot and when I informed my camera operator that I have made my own mount and that we no longer had the ability to pan the camera itself and that he would now have control of the tail rotor he got very nevous. He is just learning how to fly a helicopter. But once we got in the air and he saw just how precisely he could control the pan axis on the camera he fell in love with the new system. To make the system very easy for him and to keep him from getting me into too much trouble I have the AFRs turn way down and the expo is set at 90%.
If your mount has pan then I suggest that you turn you AFRs down to where you have just enough control over the tail rotor to make turn arounds and crank up the expo so that the tail rotor is very dead around center so that you do not introduce any unwanted movements which are obviously seen in the video.
I hope that this helps and maybe it will give you and others some things to think about which will improve video quality.
Wayne Mann |
