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Oct 23, 2012, 02:25 PM
Folding Spacetime
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Properly setting up a V400D02

As most RCG members will tell you, a universal rule in this hobby is that RTF helis rarely are ready to fly safely out of the box--and the Walkera V400D02 is no exception to this rule. A misadjusted micro heli can be annoying and tricky to repair, but a maladjusted V400D02 is very dangerous and quite a bit more costly, too. You will be best served to make it a personal requirement to go through any new heli and perform a mechanical set up before even attempting to spool up. So how do we mechanically set up a V400D02?

The picture below shows a V400D02 that is properly set up. When the throttle stick is positioned at 50%, each of the servo arms is at a 90-degree angle to the servo casing, the swash plate is level, and the swash plate is positioned in the middle of its total path of travel along the main shaft. Additionally, the two grip links should be the same length, and adjusted so that both main rotor blades have zero blade pitch. Many beginners are uncertain how to make all of these adjustments. The following steps are intended to provide a formula for setting up the V400D02.

The first thing to do is unplug the main motor and the tail motor--this is the best way to prevent an accidental spool up and injury. With the motors disconnected, put the throttle stick to 50% in stunt mode (ST-1), and switch the receiver from WK mode to ADJ mode to turn off the 3-axis gyro. This will put the servos into their centered positions without the 3-axis gyro interfering. You are now ready to starting making mechanical adjustments. The following steps provide an easy way to get your V400D02 adjusted correctly and get you into the air.

1) Adjust each servo arm so that it is positioned as close as possible to a 90-degree angle relative to the servo casing. Do not worry that some of the servo arms may not be perfectly 90-degrees to the servo casing--no two servos center exactly the same way. Anyways, we'll take care of that below.

2) Adjust the lengths of the servo links so that the swash plate is positioned in the middle between the upper and lower limits of its travel along the main shaft. It is important to avoid binding of the swash plate at the extremes of its travel.

3) Further adjust the servo links to get the swash plate as close as possible to perfectly leveled. Since the servos are not all centered in exactly the same position, you will have to lengthen or shorten each servo link accordingly so as to level the swash plate.

4) With the swash plate leveled, adjust the lengths of the grip links to put the blades at 0-degrees blade pitch. The most straightforward way to check blade pitch is by using a pitch gauge.

5) Ideally, the grip links should be identically the same length. However, there may be instances in which you must further adjust the grip links to get the blade tracking adjusted perfectly. The objective is to have both blades set to the same blade pitch (e.g., 0-degrees), and to have the blades maintain the same pitch as they are hand-rotated along their 360-degree path. If the blade pitch changes as the blades are rotated, then the swash plate is not truly leveled.

6) This is a good time to check and adjust the blade pitch extremes. Your transmitter is already set to stunt mode (ST-1), and the pitch curve should be a straight line from a lowest pitch value (e.g., 0%) to a highest pitch value (e.g., 100%). Walkera has recently produced a variety of transmitters, some of which using different numerical schemes to measure pitch curves. On the TX 2801 Pro, however, the pitch curve goes from 0% to 100%. When the throttle stick is moved to 0%, the blades will pitch downward to their most negative value. Increase the pitch curve at that point so that the blade pitch is at the desired negative value. A typical value is -10 degrees. Setting high pitch is similar. Move the throttle stick to 100% and then reduce the pitch curve so that the blade pitch is +10 degrees. The rest of the pitch curve should be a straight line between the low and high pitch values, with 50% throttle corresponding to 0-degrees blade pitch as discussed above. As you gain experience, you may find that you want to change these values somewhat; but for now, we are discussing an easy way to get the heli adjusted.

7) You will need to set up the pitch curve for Normal mode, as well. An easy way to do this is to simply make the positive pitch portion of the Normal pitch curve the same as the positive portion of the ST-1 pitch curve that you set up in the previous step. Thus, both the Normal and ST-1 pitch curves will be identical between 50% and 100% throttle. Below 50% throttle, however, we want the Normal pitch curve to be a bit higher than the ST-1 pitch curve. For example, while 0% throttle in ST-1 gives -10 degrees blade pitch, in the Normal mode you may prefer to have -5 or -4 degrees blade pitch at 0% throttle. Some beginners may feel they need even less negative blade pitch at 0% throttle, but please don't be tempted to further reduce the negative blade pitch. Even in Normal mode, you must have some negative blade pitch, otherwise you will struggle to get the heli to descend and land.

8) Once you are confident that everything is adjusted as described above, power off the receiver and transmitter, and then make absolutely certain that you switch the receiver from ADJ mode to WK mode to turn on the 3-axis gyro. If you forget this step, you will most likely crash right from the beginning!

9) Make sure everything is properly tightened and threadlocked where appropriate.

10) Make doubly-certain everything is tight and threadlocked where appropriate.

11) Let the threadlock cure for 24 hours before attempting to fly the helicopter.

12) Double-check that the receiver has been switched from ADJ mode to WK mode so as to turn on the 3-axis gyro; if not, then do that now.

13) Assuming that you have not unduly changed the pots on the receiver, you are now ready to give the heli a test flight.

Many beginners that encounter problems with the V400D02 become convinced that the solution to their problems has to do with the pots on the receiver. Care must be taken here as turning the pots can actually exasperate existing problems, or even create entirely new problems. I have my pots pretty much in the middle between the (+) and (-). If you turn them up too much, the heli will develop a noticeable wiggling motion. When this happens, you will notice the skids jiggling or the tail quickly bobbing up and down. This behavior is the 3-axis gyro analog to 'tail wag.' The conventional wisdom has always been to turn down the gyro when the tail wags too much, and I have found the same advice holds true for these 3-axis gyros. Since I turned down my gyros a bit, the heli has been very smooth in flight.

The Tail Mix pot tends to be another source of confusion. Tail Mix controls the extent to which the tail is used in conjunction with the 3-axis gyro to stabilize the heli. My Tail Mix pot is turned more toward the (+) side because I do want the receiver to use the tail for stabilization purposes. Meanwhile, the Delay pot controls how well the tail responds to rudder commands. If you turn the Delay pot too much toward the (+), the tail will be sluggish. Turn the Delay pot too much toward the (-), and the tail will tend to be bouncy. My Delay pot is around half way between the (+) and the middle point between the (+) and (-). You want to adjust your Delay pot so that quick rudder commands stop clean and sharp with no tail bounce.

The above steps should be sufficient to get a beginner with a new V400D02 up in the air easily and quickly. For a much more thorough understanding, I think you should check out Finless Bob's articles and videos at Heli Skills and Setup 101. And concerning just the gyro Delay in particular, check out Gyro Delay 101.
Last edited by navigator2011; Mar 13, 2013 at 12:10 PM.
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