Short flight times, in the hope of increasing made it even worse. Please explain what to do!

I have a small camera that weights 80g, but my issue is gimbal!
I will probably buy the frame @xfacta suggested.

But if there is any option to make a smaller frame work with my current camera and gimbal, and still get at least 15 minutes of flight time, please tell me.

Agreed, but that frame weights 450g! Thats too heavy because if I add battery, gimbal , camera, fpv and everything else it will probably weight around 1.6kg which again, brings me in the same problem, more weight less flight time!

isnt that the opposite of what I want?

Actually, what do you guys think about this frame?
https://www.amazon.com/Readytosky-Quadcopter-Stretch-Version-Landing/dp/B01N0AX1MZ/ref=sr_1_2_sspa?dchild=1&keywords=Carbon+Fiber+Drone+Frame&qid=1622711902&sr=8-2-spons&psc=1&smid=A1LU71BLX914GS&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE4QU8xNVNVTFpVRkwmZW5jcnlwdGVkSWQ9QTA0MTI5MDUxWFlVRkFBMEkwUzhTJmVuY3J5cHRlZEFkSWQ9QTA4MDEzMzUzNTE2NDNISDZENE1ZJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

NOTE: CHANGED LINK TO OTHER FRAME!!!
Seems that in the description of that frame there is exactly what I need, or not?

Also this are the motors I want to buy, seem compatible with the frame!
https://www.ihobbies.es/dji-motor-phantom-2212920kv-p-1-50-1339/

and these props:
https://www.ihobbies.es/helices-12x42-dji-negras-1cw--1ccw-p-1-50-1342/

The last two links (motors and props) are from a local shop near where I live!

@Allister @xfacta @dkemxr

What does the $3 subscription to eCalc tell you? Seriously, if you work with it for awhile you will have a good handle on what’s possible and what’s not.

This is how I build a multirotor:
Pick a frame/prop size and battery power.
Select motors appropriate for the prop size.
Build it and weigh it w/o a battery.
Buy a battery with a weight that equates to ~50% or less Hover throttle at TOW.

I still haven’t buy the subscription but using the free version it tells me 12-17 minutes depending on weight

@xfacta @dkemxr

I have a question before definitely buying frame. If the frame supports 2216 motors, which other motors can you put on it?

I have DJI 2312 960kv and will buy original propellers, maybe bigger if possible.
Which frame can be used with these? Any recommendations?

P.S: I don’t have ECALC license yet, Okay?

Thank you for your help!

Those are meant for 10" props on 3S. You could try 11" props and buy a frame that fit’s them. 11" is the largest that will fit on the cheap F450 frames.

Hi Yaros,

I will try to give you some advice that is closely related to your quad, rather than general stuff and recommendations like “throw it all away and start anew”.
I built a quad that is quite similar to yours: A clone F450 frame, 3S 5Ah battery, with gimbal and camera. The main difference in add-ons is that mine doesn’t have LED strips, but instead has a cargo dropper built around a micro servo.

But I did calculations and a “market research” before buying the parts, to save some weight. I ended up with a total weight of 1345g, which is better than what you got, but still rather on the heavy side. That gives me 16A current drain in flight, and about 10 minutes safe flight time. After those 10 minutes the battery still has quite a bit of charge left, but the voltage becomes so low that there is little thrust margin left, so that the quad might lose stability, and I prefer to land, for safety. My plan is to make my bird lose a considerable amount of weight, but keep the 3S scheme, with the same motors, ESCs, etc.

I will analyze your setup part by part:

The frame: The F450 clones are HEAVY and SOFT. This is the most important thing to replace. The problem is that I can’t find any really good frames in this size. What the market offers are frames cobbled together from simple carbon fiber tubes and plates, using massive (heavy) junction blocks, many individual parts, and lots of screws. These frames are stiffer than the F450, but most are even heavier! They are usable ONLY when combined with a 4S battery, and motors and props suitable for that, to make a heavy but powerful quad. I don’t like that. So my plan is to make my own monococque carbon fiber frame. It won’t be beautiful, but I expect to be able to build a 450mm frame that weighs only around 100g, while being much stiffer than the F450. The downside is that it won’t be crash-proof. Maybe you might want to do the same.

Motors: If yours are too crappy, you might want to replace them. But I haven’t seen much difference in efficiency between cheap and expensive motors. The difference seems to be more in terms of balance, hub pecision, ball bearing quality, and the like. I use the Readytosky 2212, 920 KV. They are cheap, need balancing, the nut thread is so loose that balancing needs to be done after mounting the prop, but the efficiency is good, and they are well matched to a 3S battery and 1045 props. These motors look identical to those red DJI ones, and very likely are the same, but far cheaper because they don’t have the DJI brand label on them!

Props: I bought five different types in 1045 size, and one 1047. The types range from the cheapest plastic props, to expensive carbon fiber props. I measured their performance on a test bench, measuring thrust versus power consumption versus throttle setting, using the same motor and ESC, fed by a fixed 11V from a power supply. The results are very interesting: There is almost no difference in efficiency between propellers of the same diameter!!! There are significant differences in other areas, for example, up to 20% difference in the power take-up and thrust for the same throttle setting, for two props having the same nominal 4.5 inch pitch. But what counts for flight time is the efficiency, and for all practical reasons, all props I tested are equally efficient!
There were large differences in balance and vibration. Interestingly, the cheapest plastic props were best in this, while the most expensive carbon fiber prop was worst! Probably because by being stiffer, any blade disalignment transmits greater cyclic forces to the shaft, while a softer propeller blade tends to flex into the position dictated by centrifugal force while transmitting less force to the shaft.
Also there was some difference in weight. The most lightweight prop was a cheap plastic one, the heaviest was a glass-filled plastic one, and the carbon fiber ones were in between.
So, my advice regarding props is opposed to what you will often read: I recommend to use cheap lightweight plastic props.

Regarding propeller size: Physics dictate that for a given static thrust, the largest propeller is the most efficient one. So when you want longest flight time with a multicopter, you must use the largest props that will fit the frame. 10 inch props are often used with the F450 frame, because they are plentiful, but if you can find 11 inch ones, they should be noticeably more efficient.
The propeller pitch should be enough to provide the thrust you need, and no more, because an overpitched prop is less efficient in terms of static thrust. For a normal weight F450, and KV920 motors, and 3S battery, 4.5 inch pitch is OK. If you can make your drone very lightweight, then it would make sense to use slightly lower pitched propellers, to get a little more efficiency.

About ESCs: You seem to have bought large, heavy ones. If so, you can shave some grams away by replacing these, and maybe also improve efficiency. Before buying, I compared electrical specs, size, weight and cost, and chose the Littlebee Spring Dshot 2-6S 30A ones. And I’m toying with the idea to save several grams of weight by using the 20A versions instead. But I would first have to compare the efficiency, because the smaller ESCs will probably cause more voltage drop. In that case, the lower efficiency needs to be evaluated against the lower weight.

Battery: I chose a 3S system because suitable components for it that fit the F450 frame are most widely available, and because this allows me to directly power the video system and gimbal, without requiring additional voltage regulators. That saves weight.
Balancing capacity against weight and cost, I opted for a 5Ah battery. And since this quad would load the battery only at 8 to 10C during full throttle, the lowest C rating battery I could get was plenty (20C rating), and saves a little bit of weight over a higher C rated battery. So the only “wrong” thing I see in your setup is the use of a battery with an unnecessarily high C rating, but the impact of this on weight and thus flighttime should be small.

Controller: I chose the Pixhawk clone (2.4.8). There are lighter options available, but I was attracted by the many features of this controller. You might consider replacing your old APC. There are many very good choices now, with some very lightweight, inexpensive, highly integrated controllers.

Radio: I used a Flysky iA6B receiver, despite its size and weight, because it has diversity reception and much better sensitivity than the lighter options. Keep in mind that I was only looking at low-cost parts. My point was not to use the best parts in existence, and no matter the price, but to use parts that have a good performance/price ratio. Which Flysky receiver are you using?

Camera: I suspect that yours is much to heavy. Looking for a lightweight, reasonably priced camera that could serve both for FPV and for high quality video recording, I ended up choosing the Runcam Split 3 micro, despite the split feature (it comes in two parts, joined by a short cable) is inconvenient in my case. The video quality of this camera is NOT what I really want - it’s a fake full-HD obtained from a 2MP sensor - but I thought it was a reasonable compromise. Because it was clear from the start that my drone would be overloaded if I installed a much heavier camera on it. Apparently you just went ahead and installed a relatively heavy camera, and that was a mistake.

Gimbal: All ready-made gimbals I found are far too big and heavy for this drone and camera. So I bought two lightweight gimbal motors, an inexpensive 2-axis controller, and made my own brackets. You might want to do the same.

My cargo dropper was made from a micro servo and a lightweight hook mechanism. I had to add a BEC to power that servo… more weight… but that added BEC also provides more reliability, since it acts as backup power for the Pixhawk. Since you don’t have this, that’s a point in favor of your quad. You are saving about 20 grams there…

I also chose a small and lightweight FPV transmitter, and a pagoda antenna for it. I can’t see what transmitter you are using, but at least I don’t see anything enormous in your photo…

Telemetry: I used a Minim-OSD to put the telemetry on the video downlink. I did not use a separate MAVLINK radio, to save weight. Did I understand correctly, that you have such a separate telemetry radio? If so, do you REALLY need it?

Landing gear: Just two styrofoam blocks to raise the front of the quad when sitting on the ground. This is lighter, and far more stable, than adding any tall legs. Your bamboo legs are probably quite lightweight, but the more you can shorten them, the better…

I shortened all thick wires to the actually required length, to save weight, and I directly soldered them instead of using connectors, which again saves some weight.

What I can suggest about your drone:

  • Keep the 3S system.

  • Keep the 5Ah battery you have, but when time comes to replace it, see if you can get a lighter one, even if it has a lower C rating. Don’t use the 2.3Ah battery, which is simply too small to get a reasonable flight time. The flight time depends largely on how much of the total weight is battery weight, and a quad that large, with a 2.3Ah 3S battery, has too little of its total weight in the battery.

  • At least for now, keep the motors and props, as probably there isn’t much to gain there.

  • Remove those useless LEDs. Althought they surely aren’t very heavy nor consume a lot of battery power, every bit of weight and power drain matters!

  • Shorten those overly long motor and battery wires.

  • Consider replacing those big ESCs by lightweight ones.

That’s the easy part. Now the difficult part comes:

  • Replace that heavy, soft, wobbly frame, by a lightweight and stiff one. You will have to make it. Laminating it from carbon fiber cloth and epoxy resin, over a styrofoam core carved into shape, is a method that can be used at home, and results in a very lightweight and stiff frame. Or maybe you can cobble together something from bamboo, glued together using carpenter’s white glue, that is stiffer and lighter than the F450. Replacing the frame is the single most important you can make!

  • Consider replacing that camera and gimbal by lighter parts. And consider mounting them in the front of the quad, rather than below, so that you don’t need long legs. To do so, you need to shift the battery backwards for balance.

  • Do a razzia to shave off every gram, and every fraction of a gram, of unnecessary weight! I intend to do the same on my quad. Things like shortening wires, removing the plastic boxes from electronic modules, replacing connectors by solder joints, and so on. The golden rule is: If you care about every milligram, then the grams will care for themselves!

  • Finally you need to make sure that your drone is well balanced, so that all four motors work equally hard. This gives your quad the best ability to stay in the air when the power margin is getting critical. Because as soon as the first motor runs out of power margin, your quad will fall out of the sky. Good balance means that the center of gravity should be in the same location as the center of thrust. Not on one side, not in front or behind, and not above nor below! I stress that latter point. When the center of gravity is far below the center of thrust, then as soon as the quad tilts, two motors have to work much more strongly than the other two. This consumes your power margin, and makes the quad lose control. You have the battery on top, and that’s fine, but your camera+gimbal assembly looks heavy and is installed below the quad, so I would assume that the center of gravity is too low.

In old times, a low center of gravity was good for pendular stability. But a quad controlled by Arducopter has its stability in the controller! It’s best off with neutral passive stability, that is, the center of gravity up in the propeller plane, and exactly in the middle of it.

I see that you would like to mainly change the frame, motors and ESCs, and keep the camera, gimbal, etc. This route will probably lead you to a bigger, heavier frame: A larger but lighter carbon fiber frame, much larger propellers, motors suited for those large propellers (lower KV, larger diameter, flatter). Even with the larger props, the heavy quad with only a 3S 5Ah battery will still limit you to short flight times…

There is no way around the fact that to get a long flight time, a lot of the total weight must be the battery. Say, making the battery 40 to 50% of the total weight is a reasonable starting point. So if you want to keep a heavy (?) camera and gimbal, you will probably need to use a larger battery, and design everything around the new weight goal. Above the weight range of an F450.

My plan of action to improve my quad, and which is probably also valid for yours, if you can make up your mind to it, is this:

  1. Consider the 3S 5Ah battery, with 10 or 11 inch props, as the size and weight reference.

  2. Calculate or measure the thrust versus power consumption of this setup.

  3. Decide how much flight time you want. Look up that point in the measured or calculated curve. This will tell you how much thrust you can get, during that desired flight time. This thrust is equal to the total weight allowed for your quad.

  4. Build the absolutely lightest frame you can, that is stiff enough.

  5. Get the lightest flight controller, and auxiliary modules necessary to get a functional quad.

  6. Weigh all the parts so far. The difference between the total allowed weight calculated in point 3, and the total weight until here, is the total weight allowed for add-ons like camera, gimbal, FPV transmitter, lights, grabber, decorative elements, etc.

  7. Find a camera, gimbal, etc, that fits within that very small weight allowance.

If the whole exercise gives an impossible result, it means that your flighttime expectation is unrealistic, and you have to re-do the exercise!

OK, enough… See the web page about my quad to see more detail about my setup. Look specially at the camera stuff, because I do think that that’s what makes the main weight difference between your quad and mine. If your camera delivers better image quality than mine, and you want to keep it for that reason, then do consider a slightly larger frame, at least 12 inch propellers, and a much larger battery.

This is my quad:

http://ludens.cl/aeromod/uglybird/uglybird.html

Good luck!
Manfred

2 Likes

Wow! That’s a great and detailed answer! I will listen to this and all of the advices you guys posted above.

@Manfred While I agree with most of what you said, I believe that changing to DJI original motors from my no name crappy ones will make a lot of difference, because they are a lot more efficient, maybe not so much compared to your motors, that claim to be a copy of the phantom 2 motors, the motors I bought (I talk about the new ones I got for rebuild) are the original phantom 3 motors made obviously, like the drone itself, by DJI.

The frame I selected is the S500, one of them on amazon that has great weight (if we compare to other frames this size) and everything I need! Hope it works! Used ecalc to calculate that it will fly for 12 minutes with my smaller battery and 18 minutes with my larger battery, while it seems a little unrealistic for 3s power, I hope it is how eCalc predicts!

Thank you everyone for your help!
Will update you on the topic when the rebuild is done and I fly for the first time!

Yaros.

I broke my self flogging away at the old APM based 'copters, until I realised that the advice Dave and others are trying to give us is accurate and true.

I did reasonable performance occasionally by using the right low cost components, but it’s a lot of work, and the best way to enjoy this hobby for me it seems, is to buy a decent sorted 'copter to USE, whilst running the learning experience in parallel. I’m personally quite keen to trade all my junk soon for a pair of 3DR Solo’s soon having had excellent operational results using a toy quadcopter that runs the same pixhawk based Flight control system. I flew 2 flights a day for 90 days with total reliability, saving the requirement to change the tiny machines motors, using a pair of Sky Vipers a while ago, a safety record unmatched by ANYTHIING I tried with the older APM system. And Dave knows, “trying” I was over on the CX20 forum…

I did mainly 450 size copters using 10 inch props and all the cheap bits that mostly were close to being “successful” and one tip I did find was that the horrible nylon curved legs will bodge onto any airframe and offer superb crash resistance and lightness compared to anything more beautiful. Hobbywing escs seemed to be reliable and inexpensive a few years ago, and I bought at least one copter that crashed because the motor bearings had worn out or the shaft was bent causing such high vibrations that the APM was throwing a “wobbly”. Note: The chinese manufacturer can use either the metric or imperial sizes on their small motor components… One size does definitely not fit all when you start ordering shafts and bearings.

Like Dirty Harry says, “a mans gotta know his limitations”!

1 Like

Which one is that? I just checked Amazon, and looked at the stated weight of seven of those S500 frames. They range from 405 grams without landing gear, to 498 grams total. And that’s heavier than the F450 clone frames!

When I enter the data of my quad into eCalc, as closely as I can to the actual parts, I tend to get slightly more pessimistic flight time predictions than what I really get. But it’s pretty close.

I think it’s just the matter of better distributing weight

Optimal weight distribution allows to keep the copter in stable flight down to a lower battery voltage, and that surely helps. But what I mean is that if you replace your S450 frame by an S500, while keeping the same prop size and the same battery, your flight time will go down, not up! Because you will be adding roughly 100g of weight.

If you use a carbon fiber S500 frame, along with larger props, suitable motors, and a larger battery, then flight time should improve.

And with a well optimized monocoque frame, flight time should improve further, because such a frame can be much lighter while still being stiff. Of course, nobody is selling such frames…

I wonder why this thread is still rolling. It’s the most basic of concepts related to multirotors.

So… sad news guys! I built the S500 quadcopter with new motors, props and the 2300 mah battery and it works, but only for 5 minutes of flight time! I might need to tune the PIDs and that might help, but still that’s not much AT ALL compared to what Ecalc calculates, which is 10 minutes! The weight is more than I expected! 1450 grams with battery and gimbal

Any suggestions? And those motors can’t support 6S BTW

I don’t think so. What motors and props? Is that a 4S battery?

Dji 2312 960kv Phantom 3 motors with Original Phantom 3 propellers
3s battery

What are these Phantom 3 propellers?

Amazon.com: DJI Original 9’’ CW+CCW Props 9450 Self-tightening Propeller 4 Pcs for Phantom 3 Professional / Advanced / Standard Quadcopter: Camera & Photo

Not from what I see. eCalc calculates 5.6 minutes of Hover time, 4.5 minutes of mixed flight time. And a Hover throttle of 68%.

So you built another Flying Pig and it’s performing exactly as expected.

Corrected for 9.4/4.5 props. Still a pig.

Or as we jokingly say here in the states:
turkey