building a helicopter

[king of nowhere]

after much strife i finally managed to build an helicopter that actually lifts from the ground.

 

unfortunately, that's all it does. it's too unstable, so after eaching a speed of a few tens of m/s it starts going out of control.

not to mention it is practically impossible to control. i don't have any direct way to regulate the engine power. i set up an action group to activate all four rotors simultaneously, but that's it. i heard people writing about putting the rotor control on the main throttle, but i have no idea how to accomplish this.

any help?

[Wobbly Av8r]

If my own experiences are any guide, the most common error would be assuming that large changes in motor torque or blade angle change are needed... neither is usually true.

To control the throttle, you need to place all the motor torque control in the "Throttle" Action Group - this allows the motor torque to be controlled with your standard SHIFT / CTRL or Z / X keys.

Place all the rotor blades in whichever "Translate" Action Group makes the most sense to you (I have mine controlled by the H /N keys since, when flying a helicopter that has no RCS, turning ON the RCS allows me to control the blade angle instead.)

Finally, limit the amount of blade angle to less than 20 degrees, probably more like 15 or less... I would experiment with maybe 3 to 5% torque on each motor and 3 to 8 degrees of blade angle for a LOT of lifting power with your design above... YMMV.

 

[king of nowhere]

1 hour ago, Wobbly Av8r said:

If my own experiences are any guide, the most common error would be assuming that large changes in motor torque or blade angle change are needed... neither is usually true.

To control the throttle, you need to place all the motor torque control in the "Throttle" Action Group - this allows the motor torque to be controlled with your standard SHIFT / CTRL or Z / X keys.

 

that would be great, but how do i do it?

 

Quote

Finally, limit the amount of blade angle to less than 20 degrees, probably more like 15 or less... I would experiment with maybe 3 to 5% torque on each motor and 3 to 8 degrees of blade angle for a LOT of lifting power with your design above... YMMV.

honestly i tried that design simply because i couldn't make an helicopter lift, and so i wanted to at least be sure it wasn't lack of litfing power...

[Wobbly Av8r]

22 hours ago, king of nowhere said:

that would be great, but how do i do it?

So the Action Group page is selected by one of the four icons in the upper left when you're in the VAB or SPH that looks like two tools in an "X";

When you select that icon, you will see three columns on the left side of the screen: Action Groups, Group Action, Selection - you select ">Main Throttle" for this example;

Click on one of the motors on your ship and assuming you placed the motors with 4-way symmetry, all 4 motors will highlight in blue, and you will then have a couple of motor entries in the "Selection" column;

Select the "<Set Torque%" text in the "Selection" column and it jumps to the middle "Group Action" column - now the torque of the motor (within the bounds you set for the part through it's PAW [Part Action Window]) is bound to the main throttle control.

 

The same thing applies with the blade angles but the control would be the % of deploy rather than torque, and the Action Group you might want to bind it to would be ">Translate U/D".

Hope that helps...

Edited August 10, 2020 by Wobbly Av8r

[king of nowhere]

1 hour ago, Wobbly Av8r said:

So the Action Group page is selected by one of the four icons in the upper left when you're in the VAB or SPH that looks like two tools in an "X";

When you select that icon, you will see three columns on the left side of the screen: Action Groups, Group Action, Selection - you select ">Main Throttle" for this example;

Click on one of the motors on your ship and assuming you placed the motors with 4-way symmetry, all 4 motors will highlight in blue, and you will then have a couple of motor entries in the "Selection" column;

Select the "<Set Torque%" text in the "Selection" column and it jumps to the middle "Group Action" column - now the torque of the motor (within the bounds you set for the part through it's PAW [Part Action Window]) is bound to the main throttle control.

 

The same thing applies with the blade angles but the control would be the % of deploy rather than torque, and the Action Group you might want to bind it to would be ">Translate U/D".

Hope that helps...

it works! it works!!!!!

now the atmosphere is no longer an obstacle to my exploration

 

i don't know if it became stable in flight because i moved the solar panels to a way that would not make a sort of parachute, or because i reduced the incidence angle of the blades. i suspect both. anyway, it climbed up to 15 km before running out of electricity

anyway, now my helicopter flies really well. now i can start developing a more serious version, one that can be packed into a spaceship and have a less limited authonomy.

Edited August 10, 2020 by king of nowhere

[Wobbly Av8r]

Glad everything's coming around!

Blade angle is probably one of the most significant things - they "max" out around 8-12 degrees; more than that they don't create more lift (emulating a stalled condition) so that's a good place to start.

FWIW, I used two of the motors you're using (I think they're the -16 light rotor?) and two of them with blade "B"'s x 4 each, lifted over 18 tons of weight at 20% torque and deployed to 3 (actual degrees are indicated on the PAW) blade angle, to give you an idea of the ratio and importance when building helicopters. Reaction wheels can make stability much, much easier...