Sunday, February 27, 2011

Week TechVideo, 2011 #08 - LEGO Zeppelin

Sandra Almeida (Cassiebsg) is a Portuguese AFOL, living in Denmark. As could it not be, she participated in the '2011 LEGOWORLD Copenhagen, DK' and sent us this nice video (among a thousand others...) from the LEGO Technic/MINDSTORMS Zeeplin flying around.

There were a few similar models hovering...
I've seen two different models, as you can realize from the video and photo below.



I tried my self a similar contraption a few months ago and tested it at the last Hispabrick, in Barcelona. The new 89509 blades from LEGO Education 9688, Renewable Energey Add-on Set were quite promising... However I didn't had the idea to use such helium balloons and of course it didn't lift off!...



But it was quite funny to observe at least a very small vertical impulsion and getting the proto-heli spinning around.
Definitely far from the required to defeat all the weight from the structure, motors and propellers. Even hanging the tethered batteries by hand (video still to produce...).

Some observations though...
  • Higher gear rations produce more rotational speed, hence more impulsion, but the inertia is also too high and the current drawn makes the PF rechargeable battery to cut-off after a few seconds or to slow down considerably, to be more precise.
  • Propellers with 3 or 4 blades also perform better, because of exactly the same effect (high speed RC motors were used, like those in the air powered car from Barman). 
  • A tail rotor is required to prevent the heli to spin, but adds a lot of weight and zero contribution to vertical impulsion.
    To have it balanced without a tail rotor, we would need the same blades but with the opposite pitch, in order to build counter-rotating propellers (LEGO, please!...).
    It is something possible to achieve with the actual blades and some angled connectors, but unfortunately this means extra weight, less performance and a too complicated design.

Not yet time of having a model made entirely of LEGO, able to fly autonomously.


Edit:
Marc-Andre Bazergui (bazmarc) [1, 2], Canadian, member of QUELUG, member of MCP4 group and known for his MINDSTORMS models, left us a comment with another video he produced, featuring the Zeppelin (Blimp) flying over, at LW2011DK.
The video also features a small interview with the authors (Kenneth Madsen and Lasse Lauesen) where they explain the basics of their project and where we got to know the software was made in Java, there is an NXT made remote control, to flight the blimp and one on-board camera which produced fantastic aerial images from the event.
From Marc's comments we also learned that "the NXT moves on the rail only to adjust the initial balance (if one balloon has more helium, move NXT to counterbalance etc..) Also very important is that to make the RC motor efficient, Lasse had to design his own motor controller".

See the magnificent video bellow and look later for further info about this project, at the authors website www.brickit.dk.



Last Update: 2011.Mar.01 08:30 CET

6 comments:

william said...

Do the two main propellers in the front also travel along the main rail?

Conchas said...

Don't think so, as it is also not required.

The main rail seems to have the only purpose of arranging room to hold the two ballons.

AVCampos said...

Regarding the helicopter you created: it has too much weight to the rear, and applying power to the main rotor would make the device tilt instead of homogeneously taking off. For comparison, real helicopters have their centre of gravity in the middle, where the engine is. The tail in the rear is balanced by the crew compartment in the front.

For this application (and for the sake of simplicity: any variation in one of the rotors has to be compensated by the other), I think it is simpler to have a tandem configuration, like the PicooZ Tandem Z. In fact, this helicopter is particularly suitable as an example, since its twin rotors, like the LEGO blades, have equal pitches, not symmetrical, and spin in the same direction. This is compensated by the rotor axles not being completely coplanar: if one of them is vertical, the other is slightly tilted to the side, to provide just enough lateral thrust to overcome the tendency to spin. The problem is to reproduce the "twisting" with LEGO parts in a light way...

This is something really worth investigating: if only the set the blades come in wasn't so expensive! :(

Conchas said...

@AVCampos,

You're right about the weight at the rear and its effects.
It was added just after realizing there was no way to make this thing to lift off, even a bit, as an experiment. This way it was possible to prevent the spin, at least. :)

The non coplanar Tandem configuration looks promising to try... At least to see till where it let us go. :)

Marc-Andre Bazergui (bazmarc) said...

Hello, I was lucky to interview and make a movie of the 2 guys who made the NXT Flying Blimps... the NXT moves on the rail only to adjust the initial balance (if one balloon has more helium, move nxt to counterbalance etc..) Also very important is that to make the RC motor efficient, Lasse had to design his own motor controller. Check out the video http://www.youtube.com/watch?v=GefwcBUioAE and later on when they post details of the C5 project on www.brickit.dk THANKS

Conchas said...

@Marc

Thank you for the information added.
The video is great and contains useful information.

I've just edited the post, to add this information and video.

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