Heavy lifting VTOL technology, frames.

I just tried to edit my post and I hope that all the comments didn't get deleted.

If so, I will have to go back through what I had, and try to add them in. oops sorry won't do that again.

There are fundamental principles such as:

Maximizing airflow, Minimizing weight, Frame Rigidity, Vibrations(mode, frequency, amplitude, localization), Torque.

In the arms specifically: There are torsional from the blades spinning, and lever forces, from the lift generated.

Compression is generally to be avoided, it can fail in a big way, so be careful with it. Oversize is better.

There are probably others so feel free to add. Those are common to all frames.

Most copters use a round boom or arm. This is bad in a wind tunnel. And if they get damaged, you have to replace the whole thing. My suggestion is to use vertical arms, allowing the downward force of the propeller to have the least resistance. Having vertical arms and using thin extruded aluminum not only make it easier to fabricate, it also makes it eco-friendly because you are not wasting fiberglass or carbon parts. You can bend the aluminum back into the proper shape effortlessly.

The torsion forces can be converted into bending/lever forces by appropriate locations of mounting points. This will increase stability because torsion is a pain to deal with. Tension is the best for most thin metals so trying to keep that in mind, putting some parts in tension will reduce needed material. Using a steel or similar wire around the arms will provide tension force against any torsion or bending because any individual arm's movement will be transferred to the other 3, causing them to act as a rigid body, it avoids sending vibrations down the arm.

By having the arms come to a central point, there is symmetry in the forces involved, makes them easier to design around.

If this is helpful at all, a thank you will do, and if you have anything to add, I will keep a record here AND in my heavy lifting design files, which will be used to make the next version of the ADrone. And I won't leave you out where credit is due. Collaboration is the future and we can do it together!

here is the work I am talking about, this is the first version, I know I am late to the drone field but that's no reason to quit.

http://www.instructables.com/id/Aluminum-sport-X-copter-frame-desig...

Views: 5531


MR60
Comment by Hugues on October 9, 2014 at 11:07am

Nice diy project. 

I also tried, mostly unsatisfactorily, aluminum designs. My main personal take away from these Al designs is awful vibrations propagation.

Comment by chrisa on October 9, 2014 at 12:44pm

I really hate to delete other people's posts, but Someone posted an attacking and non-related comment, but it did have one good observation so I will post that(mean parts taken out).

Mr.Schmit

Since the airflow below the propeller travels in a helical path (not straight down), the arms are keeping the direction of airflow perpendicular to the ground.  The air flow is hitting the sides of the arm producing more lift. .  Once you transition to forward flight, the flat arms become "wings" that will increase the flight efficiency much more than round tube type arms.  These flat arms will also increase the effect that wind has on your machine.

Comment by chrisa on October 9, 2014 at 12:47pm

The proopgation of vibrations, is something I can relate to.
I have the understanding that a better wave propogation means that the material has a

great transfer of energy, which means in the physical world, that it is more rigid,

or stronger. The goal was to design a frame that is as strong as possible, while

staying light. I believe this is the strongest frame for its weight that is possibe.

The vibrations are around 3rd or 4th on the list of priorities, for me.
They are relatively low, Low enough to have stable video from the i4 which uses a

rolling shutter, causing waves in the video. There are minimal waves in the video and

it is very stable video. It could be better, so I am looking at gimbals now, probably

will put a little foam in between and that should do it. If there was a heavier camera there would be no problem. I am using a phone so it feels like it weighs less than the foam its attached to.

Thank you       for noticing that this frame is super cheap. that was important to me

as well, because if it costs too much nobody will buy it.

I like the suggestion of an H design but it will be a little different forces

involved so a total redesign. I'm willing to work on it though.

I am glad that DIY stands for do it yourself
Some people think it means Don't Invite Yourself


Moderator
Comment by Gary Mortimer on October 9, 2014 at 12:51pm

Please do not edit posts if this gets out of hand we will ask you to close the thread. At DIY Drones we believe people own their own words and should be prepared to stand by them. 

Comment by chrisa on October 9, 2014 at 12:52pm

It does not look heavy lifting, but consider this a scale model because WHY would you start out with a full size to experiment?

It can be scaled UP or DOWN. The arms are still stable using the same base, with 24" arm length, which I find amazing.

Comment by David Locascio on October 9, 2014 at 1:19pm

Can you explain a bit more about how you're eliminating torsion? I'd think the arms would want to twist at the motor end as a reaction to the propeller, and am not sure how fastening solves this.

Comment by MHefny on October 9, 2014 at 9:13pm

Thanks for the article, I liked the vertical bars, I have my own design please check this design for rigidity

it is super strong and never bends at all :)

Comment by Euan Ramsay on October 9, 2014 at 11:39pm

Hugues is onto something re: vibrations. As a keen cyclist (8000km a year), I have ridden 6061 frames and recently carbon monocoque designs. And the ride comfort of the carbon frames is leagues ahead of the Alu frames - this is all down to the vibration absorbtion properties of carbon.

Having said that, you do need good lengths and layups for it to be effective, but some of the inherent properties will be evident in even the simple and short deployments in multirotor frames. Apart from the critical or compression failure behaviours of carbon, carbon tubing is an extremely effective system for multirotor use. The 25 and 30mm tubing is notable for its large surface area for clamp mounting, and large motor fitment.

Comment by R. D. Starwalt on October 10, 2014 at 4:40am

Good to see MHefny still around! He did *much* work with software and his controller. I enjoyed his discussions and explanations.

Any project, unless for fun, should have specifications.

You will never be able to determine if you project meets goals or specifications with them.

Do I always have a set of goals and specs? No. I do a lot of projects for fun (nobody else thinks they are fun - another subject in itself) and for the learning experience they provide.

The multirotor world is exploding with new people that have a wide variety of experiences and backgrounds. Some people have given up on trying to market a product. Some people are looking for a niche portion of the market. I simply enjoy it and the challenge it provides...as well as the ability to blow leaves around my yard without a rake.

-=Doug

Comment by R. D. Starwalt on October 10, 2014 at 10:14am

You might have seen my Instructable... HERE is the DIYD blog link about some of it (last year).

-=Doug

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