Rebuilt Lama V3

[bryont]

Hello,
I am fairly new to RC Helicopters. I had a Lama v3 awhile ago and crashed it. It sat for a long time and recently I dug it out and I built it up again with new xtreme motors and parts.

Now it has violent Rudder control issues.

The lower blades spin clockwise and the upper blades spin counter clockwise.

I have adjusted both the uper and lower radio adjusments all over hte place and I still get violent Rudder problems.

Any help or places I can check for more information?

Thanks,
Bryon

[bryont]

After reading many threads and continueing to play with the two adjustments. I have started to get it to hover. However I am not sure the 4-1 is working correctly. If I tap the rudder somtimed it will go into a violent CW spin.

Any Idea of what I should try now? Any Advice or sites to sugget I read?

[AndrejaKo]

Hi there! Sorry, but this sub-forum almost seems abandoned.

Anyway, there are several things you can do, so I'll start by listing them.

1. bad 4-in1 settings - this one looks most likely to me - decrease gyro gain!
2. bad blade settings
3. bad gear meshing
4. damaged shafts
5. motor problems
6. bad transmitter settings

So let's start eliminating issues from the beginning. First on the 4-in-1 unit you should have two potentiometers. One will be marked gain and the second will be marked proportional. Set the gain to the minimum and test the movement range of the proportional, then set it to middle. This should make sure that both motors get same amount of power and that the gyroscope isn't making any problems.

Next, make sure that the blades are completely set straight. If you usually lift off with loose blades, tighten them temporarily.

This should have decreased amount of problems with first two causes. Now try to lift off. Expect the helicopter to yaw while lifting off. You may need to add rudder a bit, but there shouldn't be any violent changes. If everything seems fine, move to the bottom. The gyro instructions are there.

Now we're getting in the more difficult to fix territory. Unfortunately, from the pictures of the main frame, I can't see if you can see the gears when looking at it from side, so we'll be extra cautious.

Remove tail, flybar, battery and blades. You may want to leave the blade grips on the shafts, but it isn't necessary at this moment.

Now turn on the transmitter and connect the battery while it is outside of the helicopter. Slowly add throttle until the motors just start moving contineously and observe how the shafts are spinning. First look for any vibrations. Check how the shafts are rotating. You should clearly see one shaft and all parts should be centered. Now take a look at the gears on the bottom of the helicopter. They should stay level while rotating. If you can't see the gear of the outer shaft, remove the inner shaft and then take a look. If you can't clearly see the rotations, slowly add more throttle until you do. Keep in mind that you should be adding as little throttle as possible, because small parts can fly off if they aren't properly connected.


Next and last step is damaged transmitter. It could be sometimes giving bad data about the position of the sticks. If you needed to remove the inner shaft in the previous step, put it back. Connect the battery and slowly add a bit of throttle so that the motors start moving. Now start moving the rudder stick, a bit at first and start increasing the movement. Look at the inner and outer shafts and make sure that they are following the commands you're sending. Leave it running for a while in various rudder positions and various throttle positions. Also at one point push the throttle all the way and look if the green light on the 4-in-1 unit turns red. It should turn red at almost full throttle, but if it does so earlier, it could indicate problems with motors. I haven't overloaded my 4-in-1 unit for long, but it could be that some sort of internal safety is acting. Next, if you have the "soft dog" cable used for connecting the transmitter to the computer, use it and take a look at the movement of various axes as you move the stick. The transmitter may be detected with more axes than 4, but only 4 should respond to stick movements and shouldn't be jerking when moved,

Next take a look at the motors themselves. Both should have two small probably orange multilayer ceramic capacitors on them, like on panels 2 and 3 here. They should be soldered to the motor, so take a look at the soldering. If the joints look bad, motors could be sending more interference than expected downstream to the 4-in-1 unit. They may also have a PTC thermistor on them which would probably be bigger than capacitors and square. When the motors are running, carefully touch the part. It should be cool, but it may be hot. If it is hot, that could indicate a problem on the motors. They increase their resistance with current and work by limiting the current going through the motor. They should normally be acting in cases where the motor is stalled and is getting voltage from full throttle, but for some reason could be activating sooner than expected.


Finally, we have a section about the 4-in-1 unit settings. It has two settings, the gain and the proportional. The proportional should be set to middle now and the gain to the minimum. If you can, find a large indoors area where you could test it. Fully assemble the helicopter, set the throttle trim on the remote to the minimum position, center the rest and lift up the helicopter to say 1.5 meters. This part is important to minimize the ground effect. Hold the height. Now pay close attention in which direction the helicopter is spinning. Land and remove the battery. If it for example was spinning clockwise, move the proportional counter-clockwise a little bit then reconnect the battery and lift off again. Do so until you have almost eliminated spinning of the helicopter on its axis. Don't bother with any slow spins now, because they depend on the battery condition.

Second part would be to set the gain. The gain should be in the lowest position in which it can counter helicopter's own spin and effects of wind. If you set the gain too high, you'll get quick powerful rudder movements. This is because the gyro is trying to compensate for the smallest movements and is doing so by creating too big rotations and then it tries to compensate for problems it created and so on. If the gyro is set too low, wind and changes to the battery voltage will keep the helicopter slowly spinning.
So start increasing gyro until until the violent movements start. Then decrease it slowly until they stop.

EXTRA BIT: Here's how to set the proportional perfectly. The correct setting depends on the battery voltage and throttle position. So first step it to take a look at LiPo discharge curve. For example, there's figure 6 from this site. Just take a look at its shape. Numbers will be slightly different if your case, so you'll want to measure them. As you can see, there is a part in which the voltage slowly drops from around 3.7 V/cell to 3.4 V/cell. This is the part of the voltage curve that lasts the longest and you'll want to have your proportional setting set to have the best ratio during it. So first get a multimeter that can log data on a computer. Then connect it to the parallel charging port of the battery. One line should go to one end of the port and the second to the other. Connect the battery to the helicopter and slowly run it while logging the data until the motors cut off. Now take a look at the graph and find the point where the voltage starts to linearly decrease. Note it. Now recharge the battery and fly the helicopter a bit, then land and check the battery voltage. When you get near the point you previously marked, set gyro gain to lowest position and quickly set the proportional setting so that the helicopter doesn't spin. After that, you can set the gyro to counteract the rotation as I previously explained.


If none of the steps help, then I have no idea what to do.

[mnwizard]

Excellent post AndrejaKo!

Hey Mods! Looks like sticky material to me!

[bryont]

Thought I would post some photos

[AndrejaKo]

Unfortunately, I can't say what the potentiometers are used for. Experimentation may help determine their use, but I'm afraid that they might be used to fine tune the frequency of the receiver.

Can anyone with more experience offer some help here?

[bryont]

Since I rebuilt my Esky Lama V3 I have a bunch parts. Anybody who was going to purchase a few items should look at this: I have them listed on Ebay.

http://cgi.ebay.com/ws/eBayISAPI.dll...:L:LCA:US:1123

I'am selling all of this as one package.

1Landing skids Used
1Package B blades (2) new
1Package A blades (2)new
2B blades used
1A blde used
1Canopy Used
1inner shaft used
3Inner shaft (new)
2Package lower outer shaft and links ( new)
1Blade grip set Used
1Blade grip set new
1Pair motors A & B Used1
Plastic swash plate used
1Fly Bar Used
1Lattice tail frame new
1Lattice tail frame used
1Reciever with TX crystal used channel 54
2 Lower outer shafts used

Esky metal lupgrade parts
1 Purple metal swash used
2 Metal blad grips used
1 Inner shaft used
1Blade grip set used