Weight capacity and lifting loads

[Joseph Martinez]

I am so very new to all of this. Is there some sort of formula to figure out how powerful motors need to be and what batteries are required to lift a certain weight? I'm thinking like a few handfuls of nails, so nobody has to run back and forth to the truck or up and down multi level construction sites. If I wanted to lift 5 lbs. where can I figure out all the math? I don't mind doing the math, I just don't know where to start.

 

[Meta4]

I am so very new to all of this. Is there some sort of formula to figure out how powerful motors need to be and what batteries are required to lift a certain weight? I'm thinking like a few handfuls of nails, so nobody has to run back and forth to the truck or up and down multi level construction sites. If I wanted to lift 5 lbs. where can I figure out all the math? I don't mind doing the math, I just don't know where to start.

Drones are very weight sensitive and a 5lb weight would require a large and quite expensive drone.

 

[Joseph Martinez]

Drones are very weight sensitive and a 5lb weight would require a large and quite expensive drone.

I know that much, what I don't know is where to figure out how much of a beast I would have to build. Would it have to be a hexarotor, octo, maybe four giant rotors would do, but how much battery would they drain.

 

[AH-1G]

I know that much, what I don't know is where to figure out how much of a beast I would have to build. Would it have to be a hexarotor, octo, maybe four giant rotors would do, but how much battery would they drain.

there are other anomalies to take into consideration, weather such as wind, density altitude on hot days, ( Density Altitude Calculator - English/Metric ) these will have an affect on the batteries performance.

 

[Tim Jones]

You need to know your all up weight and then calculate backwards
My DIY lifts off at about 8 lbs

So here is a good tool, it is free but if you are going to be trying to do these calculations I would pay the small annual fee for an account.
Basically you start with your all up weight
Then put the vehicle specs in for a known vehicle and it will tell you what you can roughly expect in flight time
If you are building, then start with your battery size, motors and props to estimate what you need
typically lower KV motors with larger props will get you longer flying times with more lift.

eCalc - the most reliable electric Motor Calculator on the Web for RC Pilots

 

[PatR]

Designing a heavy lifter is an art unto itself as you need to establish the range of weights you want to carry before you make any component selections. Estimating a rough all up weight allows review of motor sizes and quantities that can lift the weight, but it then gets a bit more complex when you start designing in safe "head room" for the system in the event of a motor/prop/ESC failure. If the system needs to be able take off at total weight at between 45% to 55% throttle to leave room for maneuvering, flying against the wind, higher density altitude use, and allow remaining motors to pick up the slack in the event of a motor failure. eCalc is a good general reference, along with performance data sheets from manufacturers.

It's a bit of work to lay out system requirements but it can be fun if you're into making things for yourself.

 

[Tim Jones]

Yes fun and distracting. If I had the money i would just pay a builder.
But I am glad I built mine. I know that system through and through. Developed my own maintenance schedule for every Flight, 20 hour, 50 hour 100 hour maintenance
the fun one is checking all the frame screws for tightness

 

[PatR]

Indeed!

 

[R.Perry]

You mentioned taking supplies to upper floors on a construction site. If this is the purpose how many people are going to be working in the vicinity of your drone operation? I think it is a great idea, just remember under part 39 you must avoid overflying people and that could very well throw a wrench into your idea.

 

[LUIS MARTINEZ]

I am so very new to all of this. Is there some sort of formula to figure out how powerful motors need to be and what batteries are required to lift a certain weight? I'm thinking like a few handfuls of nails, so nobody has to run back and forth to the truck or up and down multi level construction sites. If I wanted to lift 5 lbs. where can I figure out all the math? I don't mind doing the math, I just don't know where to start.

If you are looking at stock UAS, all manuals have the bird weight and the Maximum Takeoff Weight (MTOW). That's a quick and dirty place to start. Of course, other factors also come into play, FARs, wind, density altitude, etc.

 

[PatR]

I’m forced to disagree with what is stated in factory manuals. I have yet to see a consumer drone manual list a max take off weight, or MTOW. What they list is the weight of the aircraft as equipped by the manufacturer, not MTOW.

Most consumer drones have a very limited weight capacity over and above the listed weight as they are designed to provide the best performance at that listed weight and reserve weight capacity was not a design consideration as extra weight impacts flight time, aircraft stability, and in current center loaded throttle designs, the ability to maintain hover at center throttle stick.

Where designing a multirotors intended for transporting “freight” is concerned the best way to accomplish that task is to work backwards. Establish how much weight it will have to carry then add in average weights of the various components needed to build the unit. Build in an error factor that errs to the high side. Once you have an estimated all up weight, which includes the “freight”, you have what’s needed to make motor, ESC, propeller, and battery selections.

 

[LUIS MARTINEZ]

I’m forced to disagree with what is stated in factory manuals. I have yet to see a consumer drone manual list a max take off weight, or MTOW. What they list is the weight of the aircraft as equipped by the manufacturer, not MTOW.

Most consumer drones have a very limited weight capacity over and above the listed weight as they are designed to provide the best performance at that listed weight and reserve weight capacity was not a design consideration as extra weight impacts flight time, aircraft stability, and in current center loaded throttle designs, the ability to maintain hover at center throttle stick.

Where designing a multirotors intended for transporting “freight” is concerned the best way to accomplish that task is to work backwards. Establish how much weight it will have to carry then add in average weights of the various components needed to build the unit. Build in an error factor that errs to the high side. Once you have an estimated all up weight, which includes the “freight”, you have what’s needed to make motor, ESC, propeller, and battery selections.

 

[Fred Garvin]

........Where designing a multirotors intended for transporting “freight” is concerned the best way to accomplish that task is to work backwards. Establish how much weight it will have to carry then add in average weights of the various components needed to build the unit. Build in an error factor that errs to the high side. Once you have an estimated all up weight, which includes the “freight”, you have what’s needed to make motor, ESC, propeller, and battery selections.......

Then you have a starting point for designing an airframe geometry, based on load dimensions, that will stabilize the COG and safely carry that load.

 

[LUIS MARTINEZ]

You are wrong....

From the M600 Manual 2017 page 50:

 

[ArrUnTuS]

It's an exception Luis, with what it's worth the M600 is very good to put it. But what he means is that all manufacturers do it including DJI because you talk about the M600. The M600 is a professional drone that allows large cameras and therefore you have to specify that data, the weight of the payload can vary a lot. The rest of drones that have limited payloads omit it because "only" you can put their payloads. And the weight of the aircraft is close to the MTOW to give maximum performance for what it can support.

 

[LUIS MARTINEZ]

It's an exception Luis, with what it's worth the M600 is very good to put it. But what he means is that all manufacturers do it including DJI because you talk about the M600. The M600 is a professional drone that allows large cameras and therefore you have to specify that data, the weight of the payload can vary a lot. The rest of drones that have limited payloads omit it because "only" you can put their payloads. And the weight of the aircraft is close to the MTOW to give maximum performance for what it can support.

Pointless. The OP stated he was looking to lift 5 lbs, no Phantom or Mavic is going to do that. The responder stated " I have yet to see a consumer drone manual list a max take off weight, or MTOW. "
Incorrect information as shown. the rest is just noise....

 

[R.Perry]

How about the Xfold dragon x12 rtf

• Designed specifically for professional level aerial cinematography
• Fold up frame design, light and easy to travel with
• Ready to fly in minutes on set in tough locations
• Fit most professional gimbals with slide forward / backwards option for perfect balance and most efficient flight
• Payload spreads on large surface area with square short booms for perfect balance and efficiency
• Recommended propeller size: 26"-30"
• Cameras: 2x RED for 3D, Arri Alexa, Alexa M, F55 and similar size cameras
• Will fly single Red Epic up to an hour
• Anti-Vibration Isolation for smooth videos
• Up to 100lb payload capacity safe (140lb stress)
• Changeable frame to Quad, Hexa, X8 or X12 configurations

A deal at 32,000.00

 

[PatR]

The M600 is not a “consumer drone” by any stretch of the imagination. Nor does it fit within a class of drones that would fit within a classification of a “majority.” It’s one of a relatively few professional/enterprise drones designed to allow payload flexibility, with a price few consumers are willing to pay. If you were to review the data sheets for the majority of drones being marketed at the consumer level you would not find a listing for MTOW.

Any drone with a selling price over $4,000.00 is not one commonly found among the masses and typically one built using a much wider set of design considerations than common drones.

 

[ArrUnTuS]

@R.Perry I didn't know the Xfold Dragon X12 rtf, I looked a little over until I saw the price. I have seen $36,000. I have quickly finished my look at that drone ????

Luis, after reading your answer, you made me doubt. To doubt if I had read the conversation well, English is not my native language, but after doing it again, I have read it well. The M600 is a professional drone and not a consumer drone. I think that PatR has made it clearer than it seems to be what I had made.

MTOW is relevant only in drones designed to put custom payloads as is the case with the M600. For other drones that are not designed for that purpose it is not relevant because it is the manufacturer who determines the weight of the payload. Based on the total weight of the aircraft, it designs the propulsion systems and does so in such a way that it will squeeze the maximum potential of the aircraft leaving very little room for manoeuvre for the payload to have a significant extra weight.

When I analyze the needs of a drone that I'm going to mount, now I'm mounting an 800mm hexacopter, since weight is a fundamental factor, I calculate all the weights, the aircraft and the different possibilities of the payloads I want to mount. Once known the maximum weight that the aircraft will have in total, payload included, it is necessary to calculate which is the propulsion system (engines, variators, propellers, battery) more optimal for that aircraft, but always adjusting it as much as possible with margin to have the lowest possible consumption and the duration of flight is as long as possible. As data, the propulsion system is calculated to be 2.5 times the maximum weight of the aircraft. This allows all kinds of manoeuvres to be carried out safely (we are not talking about freestyle or inverted flight, racer, etc).

This is what big manufacturers do, because they are going to leave room for manoeuvre if it goes against their interests that their aircraft be the best?

 

[PatR]

Getting back to the original question, the solutions are complicated. The first thing to factor is cost versus benefit. How much value will be obtained by using a drone to deliver articles at a construction site? How much time is on average spent by personnel delivering small articles to drone accessible locations at a construction site? How often would the platform perform those duties? How many job sites will it be used for? What is the estimated useful life span of the drone? Those are important because they need to become more economical and efficient than using lower wage human labor, and general labor is pretty cheap even when factoring in indirect and over head labor expenses. We’ll also need to factor in the hourly wage of the drone operator, which would likely be higher than the hourly cost of unskilled labor.

Next you need to determine how much money can be expended in building such a drone? That cost forms the basis needed to amortize and balance the cost per flight against human labor. Using that very expensive $36,000.00 drone as a cost foundation we can see it would take a great many deliveries before any money could be saved instead of using a human.

After obtaining answers to the above we can establish the average size and weight of the articles we want to deliver. Alternatively we could use a maximum drone cost and find an existing drone that fits within the cost category and use that drones’ lift capacity to establish a maximum cargo capacity, but that limits your selections to what is currently available. You would still need to determine cost versus benefit to to learn if the concept is practical.

It will take an awful lot of 1lb. nail deliveries to offset the cost of even a $2,000.00 drone. If human labor costs $15.00/hour and indirect labors factors at 1.3 times the direct cost, and human labor averages 30 minutes/delivery, you’ll have to perform 99 one pound delivery flights before just the cost of a $2,000.00 drone is recovered. Add in the wage cost of the drone operator and that number is much, much greater.

Once you have the payload size and weight you can move on to an airframe? How big? If lifting only a pound or so a 500mm-600mm rig would be adequate. You won’t need a fancy video camera and its associated weight, an FPV camera to see here it’s going is more than adequate. If the intent is to carry heavier cargo the frame has to be larger, starting somewhere around 700mm-800mm. Add the average weight of a flight controller to the weight of a frame, FPV camera/video transmitter, and cargo weight. If you want to jump forward a bit you might add the weight of a couple 6S, 8000mA batteries to that total as it’s likely you’ll end up going with a 20V-22V system.

Now you can peruse motor and propeller manufacturer performance data sheets to learn which motor and prop combinations provide the thrust needed to fly the machine. You know you’ll need at least 4 motors (6 would be better if safety is a concern) and the total motor count needs to provide, at minimum, double the amount of thrust needed to lift the weight. Don’t forget to add the weight of the motors, props, ESC’s, and wiring (12 ounces for wiring is a good starting point) to the total system weight, which will generate a more than a few headaches in power necessary for weight calculation revisions. e-Calc becomes very helpful at this point as it can estimate system efficiency and flight time using you component selections. It’s not absolutely accurate but it provides enough accuracy to determine if your design selections can function well enough to meet general performance parameters.