The quads in question are the Hubsan H107D and H107C.
On a 380 mAh battery, the H107D flew for a little over 4 minutes, while the H107C flew for a little over 10 minutes. I suppose the difference is due to the FPV camera that is always on on the H107D. There is a camera in the H107C, but it is on only if there is a microSD card installed (and I do not have one yet).
On a new 500mAh battery, the H107D flew for over 6 minutes, much as I expected given the flight time on the 380 mAh battery. But the H107C flew for only 8 minutes on a new 500 mAh battery. I do not understand why.
Is there a good resource that shows the math relating the key properties of the batteries, the motors and propellers in use to the flight time? (I am no stranger to complex mathematical models; I am just a stranger to this sort of engineering.)
I haven't done enough testing to provide statistically significant results (I have 5 500 mAh batteries, supplied as an upgrade to the 380 mAh battery they come with, so I could spend weeks testing enough to get statistically significant results), but this result has me puzzled. I know the 500 mAh battery is longer and heavier than the 380 mAh battery (but both fit the Hubsan quads I have), but should that result in such a reduction in flight time? I thought the bigger battery should result in a longer flight time. Did I waste my money getting the 'upgraded' batteries?
Thanks
Ted
Replies
Thanks Gary,
I had no idea he'd made junk. I was just astonished that he'd obtained a flight time of over two hours. I'd have thought that to get such a result, he'd have spent a fortune on really good components, as well as a lot of time designing and redesigning different aspects of it. I had this, obviously mistaken, notion that you had to have good components and a good design to get a good result.
I guess the first question I'd have is, "Who makes the best components I can consider?" What would be the top 3, or top 5, manufacturers of good motors, ESC's and FCs? And does anyone make a good, small proximity sensor: something that can detect small objects a few tens of meters away, but which would allow you to mount half a dozen on a small quad, even one as big as a Blade 200 QX? All of the proximity sensors I have found so far that could be useful are so big they'd really only be suitable on quads that are half a meter or more across.
Next, I spent much of the weekend watching reviews of RTF quads that are on the market today: mostly DJI, Walker and Blade. I know the Blade 350 QX was junk when the first version of it was released (at least according to some, according to others, it was just the propellers that were junk), but the reviews I saw (and I watched a lot of them) report that all the problems Blade had initially were solved and that the result, with the 350QX2, compares well with the DJI equivalent. Actually, the reviews I saw showed no significant difference between the three in the 350 class (though one professional photographer was not impressed with the gimbal on the Walkera and Blade). granted some claimed one or another was 'better', whatever that means, but their claims were not borne out by either the video they showed or the data they presented (as if they had a religious devotion to one manufacturer or another). But the important thing was that all three could comfortably stay aloft for 25 to 30 minutes. Some of the tests included tests of the ability of the quads to hold position in windy weather (with gusts in excess of 25 mph in the one test I watched), and others showed rather aggressive flying. Thus, I plan on getting both a Walkera 350 and a Blade QR 350 QX2 to study what they did (and to both learn better how to fly well and just to have fun flying - something that is so much safer with their return to home function, which, in the tests I watched, performed admirably).
One last question. With a view toward making the frame lighter, so most of the copter's weight comes from the battery and motors, I have been looking at the feasibility of making an airframe using primarily carbon fibre tubes (motived by the observation that birds' bones are hollow). I would drawn your attention to www.cstsales.com. They have carbon tubes, ranging from .07 mm outer diameter, through 1.0, 1.5, 2.0, 2.5, 3.0 mm and up.they also have carbon fibre plate, from just over half a mm think on up. I was astonished at how light those things are. I have also read about incredibly strong adhesives that can be used with this material. So, I had an idea that one can make airframes for quads, hexacopters, octocopters, &c., using the tubes of appropriate lengths for the bulk of the airframe, and the carbon plates to join them, the plates would be used for motor mounts, as well as for mounts for the electronics. I would suppose that the carbon plates used to make the motor mounts would have to be close to the thickness of the tubes, because the strength comes from the combination of the tubes, the adhesive and these plates fastened as strategic positions. But with the use of so little material to make the airframe, the plates used to make the mounts for the electronics does not need to be so thick. I would suppose one could use these materials to make a frame as tough as the Pheonix airframe but that weights much less. I DID, though, find a way to use a little geometry to make the use of fittings and adapters completely unnecessary. The ONLY things in the airframe I have conceived are the tubes, the small plates, and the adhesive. thus, the limitations I have seen regarding use of carbon fibre tubes do not apply to this concept. But, as a scientist, I know I need a few experiments to see if it will work, and what it's weaknesses are.
I am not looking to make an airframe that can survive crashing from a height of 100 m full speed into an asphalt parking lot and survive. That would be silly and unrealistic. I am, rather, looking to see if I can make an airframe that handles as well as a Blade or Walkera quad (I have seen videos this weekend of pilots making those things do things I would be terrified to try, at least for the moment - but don't ask me to find them again as I didn't know how to save the links to the videos, links that existed only in the media player and not in the web browser), but with an airframe which is a fraction of the weight of a Pheonix airframe so that more of the weight comes from the battery and motors.
Don't get me wrong. I will be starting with spare parts from a Hubsan to make a Hubsan, and then I will make a kit from either 3DR or DJI, or both, and maybe more than one, and then I will make one from the Pheonix airframe (and hopefully I can get all the parts as spare parts, so I don't have to buy a Blade 200 QX and rip it apart to make the one using the Pheonix airframe). But then, what is the next step. I am starting my research into the potential of an airframe using carbon fibre tubes, to see if I can get a copter that is lighter still. I am just at the beginning of reading up on this, and don't expect to even begin crafting such an airframe until well into next year.
To this end, I have actually, finally, found several books, written within the past couple years, on aerodynamics, especially copter aerodynamics and UAVs. I have my reading cut out for me.
Regarding my experiments with carbon tubes and carbon plates, do you have a sense of what diameter tube would likely be appropriate for a quad the size of a Hubsan H107, and what would likely be appropriate for a quad the size of a Blade 200 QX? And what thickness of carbon plate? The 1 m tubes are all less than US$6, and the carbon plates I'd work with range in price from US$ 10 to US$ 30, so I could just experiment with them all, in different configurations, to see what is sufficiently strong.
This is very much an experimental, R&D effort, and I don't expect significant results for at least a year. And I hate the notion of buying junk, so I would repeat my request for information about the manufacturers of good quality parts. I do not want my experiments sabotaged by inferior parts.
Thanks for all the information you have provided.
That is a cool looking quad, though. But it looks kind of naked. Is it possible to put a thin shell on it without significantly adding to it's weight? But, I guess if it is built to do serious work, it doesn't need a pretty shell.
Thanks
Ted
A further thought re 3D printing,
You want maximum flight times, that means light strong frames.
3D printed frames are heavy, not very strong and excessively flexible, that is at direct odds with producing a copter with optimal flight times.
Propeller diameter is king for efficiency, the smaller the diameter the less the efficiency.
Propeller design matters a bit, but not very much in comparison to diameter.
3 Bladed props can be more efficient at carefully chosen prop speeds than equivalent diameter 2 bladed prop, but a larger 2 bladed prop will always be more efficient than any smaller prop.
Of course given relatively correct selection of pitch in both cases.
Best,'
Gary
Thanks Gary,
Is it necessarily true that 3D printed frames are too heavy and flexible, or might that be an artifact of the primitive state of the technology at the moment? Is it not possible to use such a technology to print carbon fiber or nylon frames (and using thin hollow tubes rather than solid bars - to aim for strength combined with low weight)? If not, how are good frames made with good precision. I fear if I tried to make a frame or body by hand, the neuropathy in my hands would prevent me from making perfectly balanced propellers or perfectly symmetric frames with absolutely correct angles between the parts of the frame. Sadly, I no longer have the strength and dexterity in my fingers that I had when I was young, so without a computer controlled machine, some kind of robot, precision work may not be a viable option when it comes to fabricating parts (this is why 3D printing holds such an allure for me).
One question comes to mind. If excessive flexibility can kill efficiency, there must be an upper limit on propeller diameter. In order to accommodate a larger propeller for a given body, one might give the copter longer arms. But if you do that, I would expect that as they are increased in length, the arms would become too flexible (or too brittle) because of their length, and may at the same time contribute too much to the total weight of the copter. So what would the optimal ratio be between the size of the copter body and the length of the arms, and thus the diameter of the propellers? Also, with regard to the geometry of the copter, should the arms not be long enough that the propellers do not blow down on the body, but rather beside it? If so, perhaps the arms of a quad or a hexacopter or an octocopter ought to be roughly the same length as the radius of the propellers (just thinking that now, I checked the arms and propellers on my quads and every one of them has arms that have a length equal to the radius of the propellers). If the efficiency of a copter is largely defined by the area covered by the spinning propellers, then perhaps a large number of smaller propellers, driven by small efficient motors, might be more efficient than a small number of larger propellers driven by large and thus heavier but perhaps more efficient motors; at least within limits. It seems obvious comparing a quad or hexacopter with a copter with only one or two rotors, but I have my doubts about going beyond 8 arms with 8 or 16 rotors (I wonder, now, if it helps or hurts to have two or more propellers that cover overlapping areas - witness the Y6 geometry of the Walkera Scorpion, and IIRC 3DR has a Y6 hexacopter). Thoughts?
Thanks again,
Ted
3x blade GF5030 added to much stress for my stock motor on stock V929 coreless motor. I'm not good at math but i've experienced using various type of prop blades and pitching factor on various motor types to match its endurance since i come from background of 3D plane flying that emphasize matching the right blade for 3D flight. I use this for V929 and 262 variant multirotor: http://www.hobbyking.com/hobbyking/store/__28464__GWEP5443_Orange_R...
This prop have slender and flexy tips allow it to cut through wind easily, narrow profile balde to allow increase RPM spin and reduce drag which increase motor efficiency and maneuverability. Stock prop looks like huge wings which is why most stock owner have problem flying abrupt in the wind and float away by the winds.
The reason for V929 is because it could bind with long range capable Turnigy 9X radio for precision handling and higher radio frequency wattage, V929 board also offer simple 3 axis gyro for "loose" maneuvering than rigid 6 axis so i could swiftly fly in the wind without the flight control board taking full control over my flight.
I don't have much experience with Scorpion but i'll stay away from Walkera's electronics since our club have piles of them back stores...that include their 350 size.
The reason why i didn't 3D print propellers for small quads because its too small and brittle, the rough 3D printing surface will causes too much friction and drag. 3D printing ABS/PLA ink material also brittle. 3D printing not always a permanent solution for building a proper airframe. Raw stuff like blocks of foam, carbon rods or sheet of plastics can be a best DIY solution if you are handy with it. Despite having a 3D printer i still make parts from carved foam and bunch of hot glue. 3D printing parts sometimes can be inefficiently heavy in mass compare to DIY material.
Btw here my 3d printing channel for your reference: http://www.thingiverse.com/3dxl/designs
When building or choosing a quad, just keep "KISS" Keep it Simple Setup. Too much sensors, gyros and complicated FC board just added weight, complexity, maintenance, performance and ruin the joy of flying. The pilot will determine the success of every flight not the hardware itself. By keeping your quad KISS you can start explore from there and grow step by step to advance multirotor flight regardless what size.
I have bunch of autonomous FC boards but my simple cheap quad manage to get the job done manually while my buddies on DJI phantom 2 struggles hard. :D
Hi David,
So, I would infer that the benefit, or disadvantage, of the 3x blade GF5030 depends on the capability of the motor. The chap who advised the use of the 2X GF5030 reported that it significantly improved the performance of his Blade 200 QX. So, I guess the thing for me to do is get both and see which provides the best performance. Right? BTW: How did you measure the stress the propeller placed on your stock motor? I.e. How would I tell if using it caused to much stress relative to the 2X GF5030?
I guess the take home message from what you say about propellers is that when I experiment with them, for a given motor, longer and thinner, and more flexible, is likely to be better; given that the motors on the small quads spin so fast.
So, from what you say about the V929, the V222, that I understand is to replace it, is less desirable for you because of it's more current electronics/flight control software?
My take on your assessment of 3D printing tiny parts is that you don't think the 3D printing technology is up to the task yet. Would that be fair?
You will have to point me to resources that talk about the DIY methods you mention using foam, carbon and sheets of plastic. Is it not the case that these carbon rods you mention are stronger and lighter than most other materials that might be used for the same purpose? How, especially, would you make a frame, on the one hand, and propellers on the other, from them? Or can you? I am a bit concerned, though, about manual processes as I have a neuropathy that affects my hands and feet. In addition to perpetual pain, and inaccurate sensing of temperature (which can be dangerous when cooking or using tools that can get hot - there are people with my condition that have lost limbs from injuries due to acidents during such activities), it is difficult for me to do precision work with my hands. That is why, for example, I appreciate computer assisted flight more than you apparently do. And, my fall back solution to limitations to computer assistance in anything is to apply my mind to the software engineering (something I have been doing for decades in other disciplines), to see if I can make the software more effective, rather than try to force my hands to do something my neuropathy doesn't readily let them do. If a decent FC board helps me not crash, so be it. With my hands, that may be what it takes for me to enjoy flying. You see now, why the idea of having a computer deal with the precision work in making small parts appeals to me. I can wait until the technology (and materials used for printing) have improved to the point where it can handle these requirements. In the mean time, I can either try my hand at making parts, or simply rely on parts that exist for different quads that are out there.
Hmmm, I find your take on Walkera interesting. The only reason I have looked at them, and in fact have a couple coming, is that they were highly recommended by folk here in Canada.
I like Einstein's take on simplicity. He said to keep things as simple as practicable, but no simpler. He had observed that the simplest 'solutions' are often as poor as the most complex ones, and that the optimal solutions were as simple as the system considered permitted without overlooking or ignoring anything.
If I observed you and your buddies with your respective quads, what I would do is pick your brains about what you did and why, as well as analyze the properties of your respective quads, and then use that information to figure out how to make the software better. What you would then observe is that the next generation of DJI Phantom would perform better: certainly not as well as you, given what you'd have learned during the time I did my thing, but much better than the current generation does. And, of course, the process of miniaturization means that it is just a matter of time before all the electronics required for FC systems will fit on a PCB the diameter of a small pea (at which point the impact on weight would be negligible).
It is true that this technology carries a cost, but the fact is that computers today are much more reliable than they were when I was young; and one the size of your phone can do more than could a super computer back then.
For me, now, the joy of flying is just to be able to complete a flight without crashing into anything (I just started a coupe weeks ago). ;-) It IS an addicting activity!
Thanks
Ted
ecalc .ch
Also - small batteries like that tend to get weaker after every use. So older batteries don't charge up as much.
Thanks
What size battery does not have this problem? Or does it apply to all LiPo batteries?
I guess, from what has been said so far, I am looking for a flying battery, with some number of light motors that turn relatively slowly and that have over-sized propellers. Right? But where do I find such things?
Hi Ted,
The explanation is that a given motor equipment, a given ESC, a given prop design and all of the combinations thereof result in a global "efficiency" that can vary a lot.
So in your case the extra capacity of a new battery translate into more weight with probably such a bad efficiency that you actually loose flight time (for ex your ESC draw exponentially more amps because of the weight increase; they were probably already optimized for a given weight with the smaller battery)
Hi Ted,
Although not much use for the little Hubsans, Xcopter calc will let you "configure a number of multicopters" and see what flight time you might expect to get.
http://www.ecalc.ch/xcoptercalc.php?ecalc&lang=en
The little FPV Hubsan is pretty heavy in relation to the propeller size and is thus pretty inefficient.
Generally, the bigger the propeller swept diameter and the slower it can turn at hover the higher the efficiency.
But that also requires motors that are designed to have their peak efficiency at that RPM and power output.
Generally battery weight makes up most of the weight in a copter designed to fly for extended periods and it is important to balance maximum reasonable prop diameter and motor efficiency at a given weight to achieve an optimally efficient copter at hover.
By far the most important consideration on multicopters is their hover efficiency, they are "normally" flown very close to their hover efficiency.
With the exception being extreme acrobatics or very gusty winds.
One of the problems with the current crop of very small copters is that they tend to use too small a prop diameters and too high a motor speeds for optimal efficiency.
Also, the brushed motors on the Hubsan are way less efficient than brushless ones like say on the Blade 200QX which is a fantastic small quadcopter in spite of still having too small a prop.
Even though peak motor efficiency may be similar, typically brushed motors are only optimally efficient at one speed and fall off rapidly on both sides of that speed whereas brushless maintain much higher overall efficiency at all speeds.
The motor efficiency I speak of here is not a small effect, it can be 2 to 1 or worse.
Big props, efficient slow motors, as little unnecessary weight as possible.
Generally Quadcopters can be more efficient than copters with more motor/prop units because the 4 larger props can actually have greater swept area than more smaller props in a similar area.
Best,
Gary
Hi Gary,
Thanks.
I don't suppose that there is a tutorial on how to use that page you have the link to: especially with regard to where I find the data to enter into it. I ask half in jest. I am sure I can figure it out, but I am not sure where I'd find all the data I'd need.
I wasn't aware that the motors in the Hubsan are brushed motors. Are there brushless motors I could replace them with? Are there other propellers, perhaps larger ones or ones with more blades, that I could put on my Hubsan's? They fly very well, and I am learning quickly how to control them; but the learning would go faster if the flights weren't so short.
As for the Blade 200 QX, I read one of the reviewers on amazon remark that he put larger propellers on it and he observed much better results. He said he used gemfan 5030 5" x 3" propellers. Is that as good a choice as he reported, or is there a better choice? I did a search on amazon.ca for those propellers and found only XT-XINTE carbon fiber paddle Mini 5030 propellers (I have no idea if those are the same thing that he used but by a different brand).
Based on what you said, I'd hazard a guess that propellers that have 3 or 4 blades may provide even more efficiency, perhaps depending on their geometry. I guess this amounts to asking if a greater number of blades on a propeller can compensate for not having a larger radius? Would that intuition be close to being right? But then, where could I find (slightly) larger propellers, perhaps with more blades, that would fit (or that could be made to fit)?
Is there a good source that provides these properties of motors that you describe for motors that are available for small multirotor copters, so that I guy like me has a hope of finding a good combination of motor, propeller and battery?
I am finding that the batteries and motors I have been provided by vendors have print that is too faded, or in a very tiny font, so my old eyes haven't a hope of being able to read them. I have a bunch of LiPo batteries, all 3.7 V, ranging from 250 mAh to over 300 mAh, and I can't tell the one from the other, and they are all so similar in size I can't even use that to distinguish them. And, the vendor gets them in bulk and distributes them in clear plastic, unlabelled, bags!
Thanks
Ted
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