Blade tracking: note: This will only work if the swash-plate is 100% level (90 degrees to the main shaft)
OK now we have a nice level swash-plate and all our link arms and servos are nicely sorted out lets check our blade tracking.
Before we go any further I would recommend checking the length of the long connector rods that go from the swash-plate up to the rotor head.
They should be identical in length before you start.
Now to do this we will have to run up the helicopter to about 50-60% throttle remember that it will lift off at about 70% so take it nice and easy getting it up to speed.
Placing a length of wood or something similar under the helicopter but on top of the skids then pop a few heavy books on either side will stop it from accidentally taking off.
I have mine in a "lazy Susan" fastened in a tripod, basically it's an old hard drive with a aluminium plate fastened to the motor/bearing.
Credit to HeliEye for this idea.
This allows the helicopter to be fastened to a fixed surface while allowing it to rotate freely.
ok check that both of the dials/knobs on the top of the TX are set to zero and lets start her up.
Remember the steps?
1: Fully extend the aerial
2: Check throttle position is zero.
3: Transmitter (TX) on first.
4: Plug in the helicopter and wait till the gyro led is stable.
ok you have the heli restrained so lets slowly wind up the power, nice and slow now.
At 50-60% throttle looking along the blade they should look as one.
At 60% they should stay that way, but if your tracking is out then you will see two blades.
OK if you balanced your blades using a coloured tape have a look at the two blades and see which is the coloured one, high or low.
Top or bottom?
Ok one of the blades may look nice and straight and parallel with the tail boom. We'll use this one as our reference blade and alter the other one to get the tracking.
first picture tracking out red blade low. Second picture tracking ok.
It's hard to see in these pictures but because the red tape was on the lower blade it looks paler than if it was on top or level.
Ok wind her down slowly ( all helicopters are female. They make you smile, can cause extreme pain but overall just end up costing you money ) (c;
right so you remembered which blade was out ?
no!
ok go back and wind her up again.
ok so now you know which blade is out? yes?
nice one.
now was it higher or lower than the reference blade?
D'oh!
OK wind her up again (c;
Now you know which blade is out and which direction it is out.
( I could have said get a bit of paper and a pen but it would have blown away anyway while you were concentrating on the spinning blades
) You can disconnect the battery for a bit now, then drop the aerial and turn off the TX.
OK holding the blade that needs altering, run your finger along the trailing edge (the thin side) You will come to a lump on the blade holder it has a small connector rod on it, follow the rod up and you will see it's connected by another pivot bit to another longer connecting rod. This goes down to the swash-plate.
This is the bit we need to alter to change the pitch.
If you disconnect it from the swash-plate and hold it in your left hand (with the blade facing you) hold the fly-bar level and steady.
Now if you lift the connecting rod you will see that the pitch of the blade changes.
Lifting it gives more pitch and lowering it gives less.
So if we make the rod longer we add pitch to that blade and vice verse.
Now your blade was higher than the reference blade so we need to decrease the pitch. so Shorten the rod by half a turn (turn your wrist clockwise, we work in half turns as it is the minimum we can adjust at any time) and clip it back onto the swash-plate (don't forget that bit!)
Ok go back and do it all over again, make a note as to where your altered blade is . ie. higher or lower. We want it to look like a single blade remember.
OK so was it higher or lower?
still higher? ok wind her down throttle to zero and disconnect battery, TX off.
follow along the blade again, over the top and down to the swash plate. un clip and shorten another half a turn (wrist clockwise).
Repeat the process again.
If the blade you are altering then goes lower than the reference blade STOP there and turn the rod back half a turn.
At this point you could alter the other blade half a turn to bring it in line with the other one.
However if you find you cannot get them to track no matter what you do then your swash-plate is not 100% level you will have to go back and re level it before you can do the tracking. It should take no more than one and a half turns to get the tracking (assuming both long connector rods are were the same length)
If this doing this cannot make both blades level then your swash-plate is not exactly level. go back to guide three and follow it again.
If your tracking is close ie about 3 to 4 mm out then that's ok as it will only be there when hovering dead steady. as soon as you apply any cyclic (right stick) you will alter the tracking as you fly.
ok if we have the tracking sorted lets check the pitch.
For this bit it is safer to disconnect the motor wires.
What we are looking for is - pitch 0 pitch + pitch
A tip on using the pitch gauge, pop it on the blade and check with the nose of the helicopter to your left, with the blade sticking towards you. When you check for pitch make sure the fly bar (rod with small blades on) is at 90 degrees to the shaft.
Then holding the end of the gauge in one hand and the fly bar blade in the other, sight down the length of the blade and get the top edge of the gauge parallel with the fly bar.
While we do these measurements make sure the trim dial/knob in at zero and the idle up switch towards us (hence the motor disconnected).
ok first step should be done as we have the swash-plate level the blades should be zero pitch at 50% throttle.
result!
ok now at zero throttle
and full throttle
Looking great! we want an even as possible range, here we have +10 0 -8(ish) we could alter the height of the swash-plate at this point by half a turn on each of the push rods (shorter) this may give us the most desirable range of +9 0 -9, but it will fly like this just as well.
Now switch off idle up and re check the pitch.
You will now notice that all the ranges are different.
aaargh!
It's ok don't panic, this is because of the way the stock TX is set up.
The pitch can be altered by moving the hov.pit dial.
Let's see what range we have.
Minimum throttle:
Idle up on and hov.pit full negative: pitch = -10
Idle up on and hov.pit zero: pitch = -8
Idle up on and hov.pit full positive: pitch = -5
Maximum throttle:
Idle up on and hov.pit negative: pitch = +8
Idle up on and hov.pit zero: pitch = +10
Idle up on and hov.pit positive: pitch = +12 (off the scale)
So you can see how altering the dial alters the pitch, these are called pitch curves and will be discussed in more detail in future posts.
The stock TX has two pitch curves as such, one in idle up mode and one in normal mode. Both of these curves can be changed with the hov.pit dial.
For beginners the best setting for this dial is about ten to ten (as seen on a clock face) in normal mode. (idle up off, away from you).
Altering this dial also changes the rotor head speed, not by increasing throttle as such, but as the pitch gets less then the drag on the blades is less, so as there is less drag then the blades rotate faster for the same throttle position.
TOP TIP: You should always have at least -2 degrees pitch at the minimum throttle position, because if you are flying outdoors in breezy conditions the wind will lift your helicopter and if you have no negative pitch you won't be able to get the helicopter down!
So always have some negative pitch.
OK
The dreaded tail!
Setting up the tail for use with the stock gyro.
Step one the tail servo.
With the helicopter initialized and ready to fly, the tail servo arm should be at 90 degrees to the tail servo, this allows the best even travel of the arm.
a quick check for servo direction here.
Moving the left stick to the right should make the helicopter's nose move to the right and vice versa. In order to do this the tail servo moves pushing or pulling the long connector rod attached to the tail.
Direction of travel is this.
stick right - nose right - servo arm towards the body of the helicopter.
stick left - nose left - servo arm towards the tail.
If when you move the stick to the left and the servo moves towards the body then you need to reverse the tail or rudder servo ( the switch on the TX).
ok so we have the correct direction set up.... since we checked the tail rotor setup in part one we can move on to setting up the tail.
Step two the gyro
This is a basic rate gyro and can be upgraded to a head lock or head hold gyro.
The difference between the two is this.
A rate gyro will compensate for the torque produced by the main rotors and increase the pitch of the tail rotor to stop the helicopter spinning. However if a wind blows the tail then the helicopter will "weather vane" slowly and turn to face into the wind.
A head hold gyro does the same BUT if the tail is pushed away from it's position by wind etc the gyro will adjust the pitch of the tail rotor to keep it fixed in one position.
Thus maintaining a fixed heading regardless of wind direction.
It has a switch on it, this is normally in the reverse position if the gyro is mounted above the tail boom on the frame. Leave it there.
It also has an adjustable pot (screw) with a - + sign on it, this is the gain of the gyro I normally set it to full "+" clockwise first, then slowly decrease until I get the correct amount of gain.
Ok with the motor connected and the idle up switch forward or safely rubber'd up, throttle to zero, aerial extended, you getting into the habit yet?
Keeping the helicopter still and flat on the ground plug in the battery.
This allows the gyro to find it's centre so try not to wiggle it about yet.
The red led on the gyro will flash for a couple of seconds then stay on solid, this means the gyro is ready. sometimes it's best to leave the helicopter for a few minutes to get the temperature settled, especially if the difference in temperature between storing and flying the helicopter is great.
Cold car boot to warm sunny field (well not in the UK anyway more like a red hot car to a freezing field).
Ok gyro is set
Setting up the tail:
If you don't have a lazy Susan or similar then find some slippery floor and with the helicopter wearing it's training gear, place it in the middle of the floor, making sure that if it does rotate that it cannot come in contact with anything.
Any pets should be locked out of the room until you are done.
OK gently bring up the power, the helicopter will want to spin anti clockwise against the torque of the motor and rotors (Newton's law of motion).
Try to keep the tail in one place by using the rudder (left) stick left and increase the throttle to about 35 - 40% note which way the helicopter wants to spin if left alone.
If it wants to turn nose right it has too much rudder at neutral point so we need to loosen the two screws holding the tail servo on the tail and very slightly move the whole thing a fraction towards the tail. Tighten the screws and try it again.
Once the helicopter is more or less keeping the tail in one position, it will slowly move in a direction or creep. you may find that the tail wags when you move the rudder and stop, this can be lessened by decreasing the gain pot on the gyro a tiny bit.
Any changes made to the gyro will require it to be switched off then re initialised so the easiest and safest way is unplug the battery, THEN adjust the gain pot, power up and try again.
So adjust the gain pot bit by bit until that tail does not wag when you release the rudder after moving it. At this point the helicopter may want to rotate again, just repeat the servo move a bit to correct this. It's a case of getting the right amount of gain with the right amount of tail pitch.
sorted ?
Hey your ready to fly!
Have fun and take your time.
Recommended reading " Rad's flight school" just google it.
read the forums and above all take your time and have fun.
If I have missed anything here please tell me.
Massive thanks to all the guys at Heliguy.com for letting me do this, especially Alex for putting up with my frequent visits.
I'm getting a video camera soon, so I can do some begginers lessons, your first hover etc.
so stay tuned.
Gary G. aka Anti.
_________________
My RC stuff
my youtube
Last edited by Anti_A on Sun Apr 27, 2008 3:21 pm; edited 2 times in total
