Quadcopter rotor and blades question

[MZ_per_X1]

First, I apologise if this has been asked a hundred times. I have read forums and experimented myself. 

I would like to make a quadcopter for a kerbal to discover Kerbin but no luck. The quadcopter just sits there, blades spinning. Sometimes the blades rev up then slow down, other times they spin but stall for a second before continuing, 

I understand that two opposite rotors go in normal direction and blades set to normal deployment. The other two rotors anti clockwise and blades inverted. I have a Kal 1000 and I think I set it right. Torque and RPM. The other  Kal is set to blade authority and mapped to throttle (reflecting blade deployment). 

I am not 100% what I am actually doing. Most people talk about authority limit, play position, etc but I can't find anything that actually tells me what is what. Yeah, it's a shame that the DLC didn't come with a 200 page guide book. I'm not going to lie, I'm not an expert on robotics. 

Can someone please give me some advice on how to lift and fly a quadcopter? 

 

 

[BigFatStupidHead]

Have you built a working helicopter yet? There's some good tutorials for that kicking around the forum. Also, try downloading a working helicopter to dissect. Once you have the basic principles down, a quadcopter isn't any more difficult to make than a helicopter.

[Vanamonde]

How about the obvious problem? Does it have enough thrust to lift itself? 

[MZ_per_X1]

On 11/4/2020 at 9:32 AM, BigFatStupidHead said:

Have you built a working helicopter yet? There's some good tutorials for that kicking around the forum. Also, try downloading a working helicopter to dissect. Once you have the basic principles down, a quadcopter isn't any more difficult to make than a helicopter.

I have used a rotor on a boat to propel it forward. It was confusing then. I think the different functions of the Kal 1000 are not straightforward and intuitive. For me at least. 

I downloaded a few crafts to study but I can't get them to lift either. My set up looks fine but the controller does not behave as I set it up according to the video tutorials. 

1 hour ago, Vanamonde said:

How about the obvious problem? Does it have enough thrust to lift itself? 

Difficult to say. I'm on console. But will play a bit on computer at the weekend. 

[Guest]

You don't need a KAL for a copter. Just bind the deployment angle to one axis and the motor torque to the main throttle, and start out with the blades deployed to 0 degrees. Adjust angle up for up-ness, down for down-ness, and keep enough throttle to keep them spinning, and you're good.

[MZ_per_X1]

On 11/5/2020 at 8:19 PM, Brikoleur said:

You don't need a KAL for a copter. Just bind the deployment angle to one axis and the motor torque to the main throttle, and start out with the blades deployed to 0 degrees. Adjust angle up for up-ness, down for down-ness, and keep enough throttle to keep them spinning, and you're good.

I will definitely try this then. I'm OK with deployment angle, torque and throttle. I guess why I'm scrambling around so much is because I don't understand what axis means and what it means to 'bind deployment angle to one axis' .  Does it mean an action group? 

 

And what does play position mean? 

 

Edited November 7, 2020 by MZ_per_X1

[Guest]

I'd suggest you forget about the KAL for now. It can be useful later, but now it's just adding complications.

Here's how you do it:

1. Select the rotor blades
2. Set them to "deployed"
3. Set the deployment angle to 0
4. Open Action Groups
5. Look down in the list, there will be an "Axes" section that includes things like "Main Throttle," "Left/Right,", "Up/Down", "Forward/Back" and so on. (These are from memory, the labels might be slightly different, but you'll see them.)
6. Click on "Up/Down".
7. Click again on the rotor blades.
8. You'll see a variety of options pop up in the action group pane. Select "Deployment angle."

That's it. To test that you did it correctly, fly your craft and use the up and down keys (I/K by default). You should see the blade angle change.

Then do the same for the "Main throttle" axis and "Torque Limit" on the motor spinning the blades.

[MZ_per_X1]

I was kinda on the right track. I also found a craft file to study. The aerodynamic overlay however shows green lines on one side pointing up and down on the other. I know they should be pointing up on both sides but I don't know what causes this. I didn't change anything on the craft file and according to the video should have lift up on both sides. 

[Guest]

The craft was probably broken by an update, they messed with the prop blades a few times. It looks like the deployment angle or variant on the starboard rotor is wrong: the leading edge (silvery) points down, whereas on the port one it points up. 

If the problem is that it's the wrong variant (clockwise/counterclockwise), fix that. Otherwise invert the deployment angle.

Also, mirror symmetry is kind of semi-broken especially with prop blades, you'll probably have to remove the motors from symmetry and set the axis bindings for them and their blades separately.

[AHHans]

17 hours ago, MZ_per_X1 said:

The aerodynamic overlay however shows green lines on one side pointing up and down on the other. I know they should be pointing up on both sides but I don't know what causes this.

The green arrows in the aerodynamic overlay show the rotation direction of the blades, not actual forces. This is used to determine when and in which direction the blades need to deflect when used as cyclic or collective control-surfaces.

The red (drag), yellow (control lift), purple (artificial rotor lift), dark blue (airfoil lift) and light blue (body lift) arrows show actual aerodynamic forces. Unfortunately it's hard for me to see from your screenshot if these (the yellow and purple arrows) are in the correct direction. But I'd guess that on the rotor on the left they are pointing downwards.

[AHHans]

P.S. I just checked my Basic Quadcopter ng, and, indeed, the deflection directions changed between KSP 1.8 and 1.10. I updated the craft file on KerbalX to work with the new version.

P.P.S. I just noticed that the left landing gear wheel in your screenshot is fully depressed, while the right one isn't. So, yes, that rotor is thrusting downwards...

[MZ_per_X1]

Yeah I'm a bit colourblind Those neon green and yellows always confuse me. 

 

Thanks for the comments. I will look at it again. 

This is the craft I am studying (if I remember correctly): 

Craft file in description.

And the same guy had this craft as well.

When I loaded this craft, I had the same issue. So it might be an update that messed this up? (That's not helpful when someone tries to understand how this works

 

[AHHans]

23 minutes ago, MZ_per_X1 said:

So it might be an update that messed this up?

As I wrote, either with the update from 1.8 to 1.9 or with the update from 1.9 to 1.10 the directions of the rotor blade pitch was changed.

But you can change them outside the editor, so "just" switch on the aerodynamic overlay, and toggle the "invert" button until the arrows point in the right direction.

P.S. You might need to switch on the "advanced tweakables" in the game settings.

Edited November 9, 2020 by AHHans
added P.S.

[MZ_per_X1]

Thanks guys it makes sense now. It is really odd that they changed the rotor settings. Well, you learn every day.