DH9116 Swashplate Level and Link Adjust
DH9116 Swashplate to Servo Arm Adjustable Linkage - Original Factory Lengths
Factory lengths for both servo linkages. To increase in length, turn clockwise (left). To decrease in length, turn anti or counter-clockwise (right).
The longest linkage with the outside (O.D) points of a digital vernier caliper should be 36mm (exactly 36.61mm), and with the inside (I.D) points of a digital vernier caliper the total overall length is 42mm (exactly 41.59mm)
The shortest linkage with the outside (O.D) points of a digital vernier caliper should be 26mm (exactly 26.32mm), and with the inside (I.D) points of a digital vernier caliper the total overall length is 32mm (exactly 31.21mm).
These lengths are base line measurements only. With these lengths, the heli should hover or take off with a drift backwards and to the slightly to the right.
Proceed to the next section, to mechanically fine adjust the servo arm linkages to get a perfect hands-free hover.
DH9116 Initial Basic Swashplate Levelling Procedure & Mechanical Trimming / Adjustment of the Servo Arm Linkages
Remove the canopy and find the plugs to the tail motor and main motor on the pcb and pull them out (making note of where they go), therefore disconnecting both the motors from the heli's battery power source. Connect the battery to the heli, turn on your tx and switch on / power up the heli and allow the heli to bind or sync with the tx, the servo's should flutter when it is bound. Centre all the trims on the sticks on the TX and center all the sticks.
Place the heli on a level surface and in a position, so you can see it comfortably, you are going to be doing this for 20 minutes or so. Make sure all the blades are in their shortest throw positions and the balance bar is level (a small line level fixed to the balance bar is perfect for achieving this). Look at the swashplate and ascertain if the top plate of the swash is at right angles or perpendicular to the main shaft. I find putting a long thin knitting needle or a bamboo "satay" skewer stick on the top plate exaggerates the angle and makes it more obvious. I have also found if you draw a thick horizontal and vertical line in the shape of a cross ("+") on an "A4" sheet of paper, then temporaily position it on a wall (making sure it is perfectly horizontally and vertically level before you fix it) directly behind the heli it can be used as reference marks for maintaining the alignment of the main shaft and the swashplate leveling "stick". Download and printout the "Swashplate Leveling Grid" pdf file, if you wish.
Adjust both servo arm linkages until the swashplate is level along the length of the helicopter, re-attach the linkages to the swashplate, and re-connect the tail and main motors and re-attach the canopy (re-attaching the canopy is important, because the weight of the canopy will affect the balance of the heli and if it isn't on, hovering without it will give a false drift backward).
Test fly / hover the helicopter. This must be done on a perfectly calm day or indoors well away from walls, etc, like a large shed or gym. Any slight breezes will influence or over-exaggerate any fine mechanical adjustments you make, and you will be "chasing your own tail" trying to get it perfect.
At this stage, we want to focus on the forward / backward drift, so focus on getting that as close to perfect as possible, DO NOT WORRY ABOUT ANY SIDE DRIFT. You should have an ever so slight forward bias as it takes off, not unlike a forward drift. If not, adjust both linkages one half turn at a time until you do (test fly / hover after each adjustment). If you find after each successive adjustment, there is in a middle point between forward and backwards and you just can't get it right, adjust it for a slight forward bias and then use the trims on the sticks to get it hovering perfectly and balanced against forward / backward drift.
When you have it trimmed to compensate for forward and backward drift, make a note of any side drift and what direction you move the aileron stick to correct that drift while it is hovering. If it is drifting to the left, the right (aileron) servo arm linkage is too high, if it is drifting to the right, the right (aileron) servo arm linkage is too low. There may be only one full or half turns to the link to bring it back, if the drift is severe, maybe it needs more turns, adjust the link one half turn at a time and test hover after each adjustment until the drift eliminated, if you find you can't get it perfect, fine tune it again with the tx stick trims, as required.
Last edited by stormforce; Feb 02, 2012 at 04:51 AM.
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