I was already crazy...DIYDRONES made it worst ! The story...part 2

This is part 2. To avoid ending up trapped in the twilight zone read Part 1

Hey Guys! First, I have to confess. I lied... It did not started by looking and drawing on an autocad 2009 computer screen.

It started with some delirium about designing a different kind of quad. I talked about it to my partner and we both agree that variable pitch quad was something to consider. Before many of you start screaming about complexity I would like to give you my position about it.

The venerable 4 motors / 4 ecs quad is the way to go for simplicity, affordability and quick fun.

It is the perfect platform for what it is intended for. Some are dreaming about a quad entering a contest like the outback challenge but we all know that autonomy is not what a quad is made for.

Also, redundancy is null in a traditional quad. Loose one motor and zap it goes. Loose a prop and zap it goes again. Lets pushed it further, what would it be like to have a quad to do 3D flying like a TREX 450 helo? And maybe a very different kind of 3D flying? What would it be like to have a quad flying with the speed and the autonomy of a plane? What would it be like to have that kind of quad doing it with absolute redundancy and also with total safety to surrounding peoples and infrastructure?

That is where you will say I have got crazy. My friend and I have the intention of proving you right about this craziness by proving you wrong about the limitations of a quad.

One last word, this one about KISS (keep it stupid simple). It is my opinion that you can KISS a simple design by design, OR, you can KISS a complex system by a simple design. Both result should be targeting a different mission and be good at it. DIY does not keep one from making it a complex but efficient system. Alright, money can do that so that is why we also added that requirement to our project.

You can now see that we are indeed crazy and some of you probably are to. Those one will understand that a guy can't sleep over some crazy ideas and some times find the solution in the middle of the night. That is what happen to me when at 2 o'clock in the morning I saw 4 penny's standing side by side on the night table. ZLAMM ! Here is the simplest way to have 4 rotors turning by opposite rotation pairs. You all know that it is a requirement for yaw control of a quad. Many have tried to figure it all and it was there, costing only 4 cents.

So now, talking about affordability... What looks just like a quad arm but with a variable pitch head? Many of you again thought about that but a few tried it. You are right, an helo tail boom seems to fit the profile. And what is the most common helo with easily available, affordable parts? The trex / clones family. Just check on eBay, it is crazy what our Chinese friends can do for almost nothing. If you want some quality, you guys from the US are pretty good at it although a little bit expensive. But hey ! you get what you need for the place you need it.

Ok now for my Fans Club, here some more details... Please understand that the next video clip is showing an hand drilled crude prototype never intended to fly. It was merely a proof of concept for a gear train and also maybe a dream catcher. If this is bothering you and your are disappointed, I will stop right here, just let me know...

To move in any one direction will require different amounts of pitch in the lets say front right and left rear rotor. These are spinning at the same RPM correct? To keep the model stable in forward flight this will require mixing the front left and right rear rotor proportionally up to airspeed X. X being the airspeed limit of the lifting capability of the two retreating rotor systems. Above this airspeed the model is for sure to pitch at a 45 degree angle relative to the direction of flight. In most rotary wing systems the blades can hinge this changes the vector of the blades and allows for a more equal amount of lift.
If I’m not explaining it right see this link.
http://en.wikipedia.org/wiki/Dissymetry_of_Lift

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Comments

Paul Marsh October 2, 2010 at 10:50am

@Mario--No need to admit anything yet. Let the rest of us keep guessing--you're stimulating us to think.

Now, assuming those booms do rotate and the rotor heads tilt, I was also thinking of the smooth pan you could get as you mention above. I don't really know much about how tradtional quads are controlled, so maybe they can also rotate in place, but maybe not as stabilized as your design would allow. So, it looks like you've got a quad V-22 Osprey tilt rotor in works--not that you have to admit that. :)
Mario October 2, 2010 at 10:24am

Paul, also, let say that if there are tilting rotors and assuming that the thrust of only two of them is enough to sustain level flight, not only would you get a stabilized platform but also a pan and tilt platform
Mario October 2, 2010 at 10:12am

Paul ! Are you trying to make me admit that there is rotating booms? :)
Paul Marsh October 2, 2010 at 10:08am

This might not have been an intent of the design, but could be a benefit. Those rotating booms which will allow the rotor heads to tilt could make for a very stable camera platform. The quad could translate right and left or forward and backward without having to tilt the entire frame. In station keeping scenarios, such as crowd surveillance, this would make for a very stable camera platform. Make sense?
Wil S October 1, 2010 at 9:32pm

To move in any one direction will require different amounts of pitch in the lets say front right and left rear rotor. These are spinning at the same RPM correct? To keep the model stable in forward flight this will require mixing the front left and right rear rotor proportionally up to airspeed X. X being the airspeed limit of the lifting capability of the two retreating rotor systems. Above this airspeed the model is for sure to pitch at a 45 degree angle relative to the direction of flight. In most rotary wing systems the blades can hinge this changes the vector of the blades and allows for a more equal amount of lift.
If I’m not explaining it right see this link.
http://en.wikipedia.org/wiki/Dissymetry_of_Lift
Mario October 1, 2010 at 8:50pm

Hey Wil S !

Sorry, I don't se what you mean. Could you be more specific?
Wil S October 1, 2010 at 8:47pm

I’m not bringing up cyclic input I am pointing out dissymmetry of lift. I think it will cause the model to pitch about the 45 degree access relative to the direction of flight when flying in an x pattern.
Mario October 1, 2010 at 7:56pm

@ John

John,
Yep my friend ! You are right. Just like a regular quad...
Mario October 1, 2010 at 7:50pm

@ Chris

Chris, I have also a stupid imagination... just watch me going...
Mario October 1, 2010 at 7:47pm

@ Wil S

To my knowledge, one of the reason for cyclic on a rotor is to reduce the angle of attack of the blade moving forward while the vehicle is also moving forward. This is to avoid the rolling moment around the longitudinal axis caused by a shift in the pressure center of the rotor disk.

If the quad is moving in a X configuration, this effect is neutralized by the fact that pressure center is moving opposite direction on the contra rotating rotors.

Regards,

Yep ! We are going variable pitch (just like collective) with constant speed (governed motors).

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