[WIP] Tandem Rotor Helicopter- Answered, pics soon

[BrickbyBrickTechnic]

Hello,

My latest project will be a tandem rotor helicopter. But I have a few questions before I can really begin to build:

1) Do the swashplates turn on 2 axes (front to back, side to side) or just side to side?

2)Do the anti-torque pedals control the rear rotor only?

Thanks. I hope there's a heli expert willing to help. As soon as I have answers, pictures will be posted.

Thank you!

BbBT

Edited March 22, 2018 by BrickbyBrickTechnic

[brickless_kiwi]

Need to use laptop not phone but yes and yes though for pitch change the swash plate moves up as the disc of rotation works 90 degree out from the controls 

Edited March 22, 2018 by brickless_kiwi

[BrickbyBrickTechnic]

50 minutes ago, brickless_kiwi said:

Need to use laptop not phone but yes and yes though for pitch change the swash plate moves up as the disc of rotation works 90 degree out from the controls 

Great, thanks! I will update my control system accordingly.

[steph77]

OK,
This question is for me, having already studied in depth the subject.

It is important to understand how a tandem rotor helicopter works.
Unlike a conventional helicopter, tandem helicopters use their two rotors continuously to steer the aircraft.

In practice I will break down each movement by explaining what setting is used at the rotor level:

1. To go up and down
The pilot pulls on the collective pitch lever, the two swashplates move down together to increase or decrease the lift of the two rotors simultaneously: the aircraft goes up or down

2. To advance in a straight line.
The helicopter uses a differential of lift between the rear rotor and the front rotor. By pushing the broomstick forward, the pilot increases the collective of the tail rotor while decreasing the collective of the rotor before: the helicopter advances.

3. For lateral translation
By tilting the broom stick to the left, the pilot varies the cyclic pitch of the two rotors in the same direction (the two swashplates tilt respectively left and right together: the helicopter moves left and right

4. To rotate on the spot,
The pilot pushes the rudder left or right. This action causes the swashplate to move left and right, but not together, in contrast to each other. This action has the effect of creating a lift imbalance between the left front and rear right of the aircraft which induces a static rotation.

In Lego, the big challenge is to build the control system between swashplates and cabin controls. I realized this command mixing system, here is what it looks like ( see video below). This prototype must obviously be compacted to fit into a credible model:

The basic principle is that the mixing is done on two stages. The first mixing stage takes the collective components, the second the cyclical components. There are four inputs to this mixer:

The first is that of the general collective step. By actuating the two branches of the mixing system move forward and back together.

The second entry is related to the forward / backward action of the joystick. It varies the two branches of the first stage of mixing a contrario.
The third entry takes the first cyclical component. It is connected to the lateral movement of the joystick. Its action has the effect of varying together the second mixing stage.

The last entry takes the rudder and has the effect of varying the second level of mixing a contrario.

At the output there are two settings per rotor. Each has a collective component and a left / right cyclical component. No rotor has a forward / backward cyclic component.

I hope I have been clear for this long explanation.
Regards,
Steph.

 

 

 

EDIT:

here is a detailed view explaining the video:

EDIT: here is what it could look like once compacted:

 

And finaly the cut view of the real chinook commands:

 

Enjoy ;)

Edited March 22, 2018 by steph77
completion of information

[BrickbyBrickTechnic]

Wow @steph77 . Thank you so much for this wealth of information. Not only did I learn something, I completely understand because your explanation was very clear. I appreciate it very much and now have all the info I need to complete the control system. 

I will post pictures tomorrow.