Economical Multi-rotor That Can Lift 15 pounds for 20 Minute Flight

Hello Everyone,

I am also writing this post because I need something, and I think its possible to do. Recently I attached the new Ronin MX, A Hyperspectral Camera, An Intel Nuc to a DJI S1000. Needless to say, the payload was around 14 - 15 pounds without the 22,000 mah batteries. Flight times ranged 3-5 minutes, and ESC, motors, batteries, wires were hot after flight. The system is not efficient. 

Is there Is there anything or has anyone built anything that is under 5,000 dollars?  I am posting this because I see a lot of bright minds on here, and I have yet to see a post that someone shows how to make a system that will most effectively lift

I am posting this because I see a lot of bright minds on here and I have yet to see a post that someone shows how to make a system that will most effectively and efficiently lift a 15-pound payload. It would also be awesome to see people's most effectively system that carry 2, 5, 10, 15, 20 pound payloads. Correct me if I am wrong, really all we need is motor size how many and what set up, preferred ESC and size, batteries needed for 20 min flight.  

Lets see what you got! We are at an interensting time where sensor technolgy is getting smaller and lighter. Hyperspectial that I put on my craft 5 years ago was 300,000 dollars and weighed 50 pounds. 

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Hi Tom,

It sounds like you are right around the max take off weight for the S1000 at around 24 pounds.

And sure you can build your own for less than $5000.00 that can handle that, as James says above.

You could actually probably get the necessary lift with even a quad copter with sufficiently large props and motors.

With the configuration James suggested and the size props and appropriate motors in an X8 format you could likely lift well over a twenty pound payload.

Coaxial props themselves cost between 10 and 20 percent in efficiency but if you want maximum lift, that is one way to get it.

I'm going to suggest 2 alternatives.

1. Since you already apparently have an S1000 try to make your equipment lighter instead.

Multispectral cameras often carry a lot of extra weight in robust cases and unnecessary features.

If you bought a cased NUC, get rid of the case and see where else you can cut back weight.

The S1000 is a decent handling multicopter and if you can make it work you are ahead of the game.

Bigger multis with bigger props handle and respond more sluggishly.

2. If the weight loss idea doesn't appeal or can't achieve sufficient savings, look seriously at UAS helicopters.

They are way more efficient than a multi because of that huge rotor and typically capacity, performance and endurance is greater too.

You really should not be flying under the conditions you have described, you are undoubtedly overheating motors and ESCs and you could easily be exceeding your batteries max C values.

If you keep trying to fly that way, you will need ALL new equipment very soon.

Best Regards,

Gary

As James stated above, that setup will get you the performance you desire. However, I disagree that you can do it for $5,000. Just the motors, escs, and props will set you back more than $5,000. Factor in the cost of a frame, autopilot, batteries and chargers and a more realistic estimate is over $10,000 just in parts.

I know a thing or two about these big machines because I have built a few of them. KDE 7215 motors, KDE 95A ESCs, Tmotor 29x9.5" props on a custom airframe with a pixhawk. Also worth noting that these large machines take a bit of effort to setup and tune. When you factor in all the time and materials it takes to get one of these larger machines built, you are probably better off buying a pre built machine (like James stated above). This machine was built for a commercial customer that is using it in invasive plant control.

Thanks

-Brian

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Nice frame Brian. Was this self built or is it a comercially available frame ?


Brian Riskas said:

As James stated above, that setup will get you the performance you desire. However, I disagree that you can do it for $5,000. Just the motors, escs, and props will set you back more than $5,000. Factor in the cost of a frame, autopilot, batteries and chargers and a more realistic estimate is over $10,000 just in parts.

I know a thing or two about these big machines because I have built a few of them. KDE 7215 motors, KDE 95A ESCs, Tmotor 29x9.5" props on a custom airframe with a pixhawk. Also worth noting that these large machines take a bit of effort to setup and tune. When you factor in all the time and materials it takes to get one of these larger machines built, you are probably better off buying a pre built machine (like James stated above). This machine was built for a commercial customer that is using it in invasive plant control.

Thanks

-Brian

The frame is custom built by my company for use in agricultural settings. The frame itself is waterproof and dustproof (IP54), and is designed to carry a large range of payloads. It also provides isolation for the pixhawk from the large rotor wash that these machines generate. When you get to props of this size, you cannot have the pixhawk exposed to the rotor wash or you will get very poor Alt Hold performance because the barometer gets false readings from the prop wash.

Something worth mentioning is that we are getting pretty good flight times with this setup, approx. 32 minutes with a 20lb payload, and almost 50 minutes with a gopro, Tiny2 gimbal, and Connex HD video link. That is with standard LiPo batteries (we could probably get longer flight times with a low C battery, the system only draws ~1.5C in operation).

I am not as familiar with the parts that James mentioned above, but it sounds like they would probably work with your setup. I have a few Tarot frames and they are of good quality, especially for the price you pay.

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Great Frame design Brian.

And certainly if you build top drawer with KDE and parts like these, $10,000.00 add up really fast.

Best looking heavy lift multi I have ever seen.

Really serious CNC aluminum central hub.

And I really like the aerodynamic motor spars, I have thought for a long time that that is how they should be made and it has been disappointing to me how almost nobody thinks about it.

Round is twice as good as flat, but aerodynamic can reduce the loss to a tiny fraction.

Most all the DIY ones use flat plate which is absolutely the worst and even DJI and Yuneec just use round or oval.

The injection molded ones could easily cut the losses in half by simply using a more aerodynamic shape and even the round carbon fiber tube copters could benefit enormously if only somebody would start selling economical aerodynamic shaped tube versions.

Your Aero overwrap seems a really good alternative, are they Kydex?

Best Regards,

Gary

Gary, good eye! There are a few advantages to using the airfoil shape, the first of which is reducing the drag (by an order of magnitude when compared to a round tube). The second advantage is that the airfoil shape reduced vibration due to vortex shedding, which can cause some nasty vibrations on a large copter such as this one.

The arms are full carbon fiber, we selected the airfoil profile based on the airspeed from the large props we are running. There are machined aluminum hardpoints bonded into the tubes. This allows for a much lighter setup than using a round tube with a faring. The airfoil shape is actually more structurally efficient than a comparable round tube, which is just a bonus with this design.

The body of is machined from a single piece of aluminum, and is significantly lighter, stiffer, and more durable than the plate and tube designs of pretty much every other heavy lift copter out there. The body also acts as a heat sink for the electronics as well.

The whole copter was designed to overcome the shortcomings we found with off the shelf units. We wanted a machine with better flight times, smaller footprint, and better durability than was found in the off the shelf frames.

I know this machine is a bit more than Tom was looking for, but I believe he would be very satisfied with the performance (especially when carrying heavy/expensive multispectral camera gear)

Yeah, that's an interesting design there Brian.  What is your company name?

Rob-

my company is called RMD Systems. We are a contract design firm primarily dealing with aerospace mechanisms. A few years back, we were contracted to build a small sprayer system for a UAV for use in an agricultural setting. After operating the system and getting feedback from the customer, we realized that we needed a vehicle with better performance to fully exploit the tank system.

I should probably post my own blog instead of hijacking Tom's thread, sorry Tom!

Nice Brian we wait your post :)

Thx Brian for explaining your frame design. will you produce a smaller version for 16" props? would be interested.

Hi Brian,

Of course the improvement in efficiency is obvious.

But I can also certainly understand, how especially with the big slow props and high mass and periodic pressure waves from them on the spar, that broad low to medium frequency high amplitude periodic asynchronous vibration could be a serious problem and be hugely reduced by the aerodynamic shape.

I am wondering if you still don't run into some negative effects simply because of the out of phase coaxial blade interference especially when maneuvering or climbing or descending.

With those big slow props I would think that might still get a little choppy sometimes.

Just a question relating to my own impressions, wondering at the real life importance of the issue.

You seem to have been one of the first to put together a really well designed serious large multicopter.

From what I know now, I think your large X8 copter probably represents the reasonable upper limit of multicopters.

For practical purposes, larger hovering UAVs are probably generally going to be better as helicopters.

You are at the top upper diameter fixed pitch propeller wise that will work effectively and provide an acceptable response rate for a hovering vehicle.

I suppose you could make a Coaxial 10, 12 or even 16 using the same components, but I think a properly designed heli would have the edge, both handling better and being more efficient.

In any case, hats off, you have set the bar.

Best Regards,

Gary

Hugues-

The idea behind the design was to have a modular frame assembly that would support a variety of layouts, from a quad to flat octo to an X8. For example, a version with 16" props would use the same electronics housing (the 'big money' part) and would use the same airfoil shaped booms, just shortened. Based on the interest in this thread I will put together my own blog post in the next couple of days.

Gary-

Our main motivation for going with the airfoil shaped booms was actually vibration reduction. We ran a few CFD simulations while we were still in the early phases of the design, and the pressure drop across a 30mm boom is substantial, even at the lower air velocity from the larger props. Factor in the larger mass of air impinging on the boom, and you have a recipe  for large vibrations.

In our testing, we have not noticed any strange behavior compared to any other X8 (ie no weird vibrations, uncontrolled movement, etc). I agree that the asynchronous phases of the props are very difficult (if not impossible) to model, but so far in our testing it seems to be a non issue.

The machine climbs and descends very well, and is extremely stable, even in the wind. We intentionally flew with no payload on a windy day (15mph, gusting to 20mph) and the machine seems to be pretty much unaffected.  I personally believe that the airfoil boom acts like a stator in a jet engine, and helps to align the flow from the upper prop to the lower prop, increasing the efficiency of the lower prop (although I have no scientific proof of this either way).

As for your comment on helicopters, I am in total agreement. Once you scale to larger sizes, a swashplate will always have a better response than a large fixed pitch prop. A variable pitch multirotor is a solution looking for a question, and has all of the negatives of both a single rotor helicopter and a multicopter (although I would still like to build one someday just for the challenge of the gearbox design).

Thank you for your compliments, our intentions were to develop the best heavy lift multirotor platform, bar none.  I will post some better pictures and technical information in the next few days.

Thanks

-Brian

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