The CyberQuad

[x0054]

10% efficiency isn't bad at all, especially once you optimized for weight, prop size, electrical draw, etc. On a 20 minute quad 10% is extra 2 minutes. I'll look foreword to that article.

On a side note, looking at your design, I can't help but picture it all incased in a plastic ball with just 4 feet sticking out, painted all black, like the death star

 

[FinalGlideAus]

Those are some neat numbers, and I'm very curious about the results if Cyber can make the measurements! Very interesting.

Cyber, what is TCE?

And yes the prop does matter, but I guess these measurements need to be done 'ceteris paribus', or 'all else being equal'. So, start with a fresh battery, do the hover test with the extra cardboard on the booms for the extra drag, then mount the same cardboard on the top of the frame (so the weight will be equal) and do the measurement again.

It's a neat little quad, dude!

Yes I'd be keen to see some tests like that also where the only variable is the boom width. I have in the past done some thrust tests on the bench and changing from 30mm wide booms to 10mm wide booms using a 9' prop only yielded a 1-2% increase in thrust. It would be good to see an efficiency test to see if it had similar or different results.

You can do the numbers till you're blue in the face but real world tests show the proof is in the pudding. Fluid dynamics ain't that simple.

I'm really keen to see that little alien bug in the air I must say Cyber!

 

[Cyberdactyl]

I'm pretty disappointed in the AfroSlims. I found they will desync on 4S. Here is a 22 second video catching one in the act. You'll hear the motor desync 16 seconds in. I had to record a few times to catch it, but that's certainly enough to not trust them.

The good news, if there is any, is it has yet to occur with 3S, and I now have run around 15 3S packs through it.

I'm curious if flashing to newer firmware will help. I bought these in early June, so I imagine the firmware is most likely a version or two back.

 

[Cyberdactyl]

Had some Labor Day fun. I have some old 0930 tri-blade props I don't see ever using, so purely for fun and curiosity, I decided to try something Cranial suggested. To cut them down and put them on the mini. . .

They work. . . after a fashion. I can't seem to get them perfectly balanced. I have them darn close, but the vibration is still moderate. With such an extra wide chord, I made them 4.5". I did a couple ultra short, 'Spruce Goose' "proof of concept" flights of about one minute each. It was a cool experiment, but they'll come off after I get some video.

Also tried the GoPro tabs I put on the front. I added it for the unlikely option of using the GoPro for FPV. Works OK, but I'm uncomfortable putting $400 out in the open like that.

Now, on to the more pleasant discoveries. I've been noticing when my mini flies faster and faster forward, it's taking less elevator to keep it level at speed. It's flying a bit like hydrofoiling, where pushing the throttle higher makes it 'float' upwards with no elevator input. It's been hard to evaluate this phenomenon in detail because it's been horribly hot and I have yet to go to a field where I can push the throttle close to wide open for more than a second, but I believe it's getting deflection lift. The vertical flat booms tilt forward and appear to actually be gaining some lift as opposed to the booms of box-type mini where the booms are laid flat. As those fly faster and faster forward, the booms will actually push the quad down as it deflects the air stream upwards.

Another tidbit I ran across. I knew having thin booms in planform were energy saving and efficient, but had no idea how much.

Below is an old MIT education video from the National Committee for Fluid Mechanics comparing planform area in an airstream. What literally blew me away is how critical it is to have an airfoil IF you want ultimate efficiency, and not just a small planform in the airstream. And to stress that in spades, is the comparison of an airfoil of macro size, compared to a thin wire . . . Check it out at time 04:35.

I must admit, I was a little doubtful of my results in the videos I shot a few months ago comparing boom planforms, but now believe they are much more accurate than I suspected.

 

[FinalGlideAus]

Yes as I've been saying before the round arms are pretty much the worse you can have. That's why racing sailboats have airfoil shaped masts.

While I've always believed the difference in efficiency from extra thrust is very minimal with the vertical booms but there will be a noticeable positive effect in performance during FFF as top speed increases. At lower speeds it won't make much of a difference but with the speeds my quads are starting to do the effect becomes exponential.

 

[Cyberdactyl]

I think my next project of small MRs will be an ultra light vertical boom quad with the Naze32 I just got. I suppose I could just remove the cage on the current mini, but I really want a small FPV model when the cooler weather comes in a couple weeks. Now, it's torture with fogging goggles and mosquitoes you can't swat because your hands are busy and your eyes are covered.

Plus I think I'll do it in 3mm CF instead of 2mm. The 2mm is a tad too thin to get crazy. I'm going to need some ESCs that can handle 4S, maybe I can talk the queen into giving the nod on me spending $100 on four postage stamp pieces of electronics.

 

[Balu]

Hm. But the horizontal flat booms on the mini quads should be bad then too? If you tilt them forwards they will not only provide more drag, but also push the copter down?

 

[Cyberdactyl]

Flat booms are horribly inefficient, eating between 15-20% of the available thrust. Even my 2.93mm wide booms in planform, which I assumed would lose maybe 2-3% is probably double that. But I'm thinking the grooves made by the shrink may be producing an unintentional boundary layer which may help a percent or so on one side of the boom. I have thought about covering the booms with an airfoil shaped piece of 0.28" thick Kydex. That would add around 4g per boom, so it might be worthwhile, especially in fast forward flight, inching closer to my original idea of a true racing quad.

As to wide horizontally flat booms deflecting the airstream up, and pushing the quad down, I would say a definite yes.

It's probably worse than that, in that a ragged low pressure bubble is formed on the underside of the boom causing dynamic "lift", but down, not up. But as was said above, translational velocity losses (actually moving and not hovering) is inconsequential when the air speed is low.

The inefficiencies really come into play once the boom moves into regions where the boom tilt grows from forward speed, and is probably directly proportional to the sine angle off its original flat angle. Then, you have a double whammy of the the quad's forward speed driving it into the ground along with high motor rpm increasing the inefficiency by attempting to pound the boom into the ground.

 

[FinalGlideAus]

Sorry Cyber but a 15-20% thrust reduction is total hogwash. Yes there is gains involved but as I have already proved with my practical tests many months ago, going from a 30mm wide boom to a 10mm wide boom on 9" prop only yeilds a 1-2% gain in thrust. That is a far cry from your continued statement of 15-20%. There has been more than one person ask that you do a practical test to compare flight times or thrust amounts where the ONLY change on the quad is the boom width and as they have stated it is very easy to do. Until you do this then you are just guessing. You can't just read a few texts and start quoting numbers about your quad.

That said, I do agree with the positive incidence of the booms produciñg lift....kînd of. With vertical booms there will be a positive AoA compared to the flat booms which will have a negative AoA in FFF which will have some effect but... With such an extreme AoA there will be far more drag than lift as the boom will be essentially in a stalled state. Put your boom in a wind tunnel at 45deg and have a look at the results. Remember that an airfoil (and the boom is a very crude airfoil) will always stall at the same AoA. Plus... Forward airspeed will greatly change both the characteristics AND effectiveness of the vertical booms. I would put forward that at the speed the minis are flying generally now the effect is minimal. Once you start getting some real speed I.e. Going past 100-150km/h then the effect exponentially increases.

There some downsides to vertical booms too. Durability is one. Looking at the angle most quads crash into solid objects, a vertical boom now is at it's most weak angle and is more prone to breaking on impact. You can't win a race if you're broken.

As for separation layers , laminar flow and so on I think we need to look at what it is we're hauling through the sky. It's like a helicopter. You can streamline it a bit but it will never be efficient in terms of boundary layers. Plus things don't scale down well in fluid dynamics. That's why you don't see laminar airfoils on model aircraft because it's impossible to achieve.

Cyber, please don't take my comments like I think your project is a waste of time as I'm actually really interested in it and I do think you're on to something and believe proper racing quads in the future will have vertical booms but you need to quantify your figures with actual tests where only the parameter you are testing has changed before quoting figures etc.

 

[Cyberdactyl]

I never said vertical booms are durable, that is an entirely different issue. And I would agree, most especially the way I mounted my motors.

Ok, that was an easy one and out of the way.

However, I'm not sure what it would take to make you see the reality of blocking the thrust column with a flat plate is a severe detriment to overall thrust.

As to your test, and based purely on a mathematical reduction, I showed it was in error, and most likely empirically incorrect, but I didn't see the actual test. I won't go to "hogwash", but I'm not sure how you're getting that magical 465g of thrust from an entirely covered disk ...or... what the efficiency curve would look like to arrive at 100% loss once the disk was entirely blocked. I certainly don't want to think you believe an entirely blocked disk still provides thrust.

My tests didn't do it. The MIT video apparently doesn't do it. So I guess we'll have to disagree and let those interested in improving efficiency be the judge.

 

[FinalGlideAus]

You have said there is an improvement of 15-20% in thrust by going to the vertical booms and also the same in efficiency. The simple way to prove those numbers you have theorized is to measure total thrust and hover flight time on the quad as is and then add foam or something very light to the booms to widen them to 10mm and redo the test. That is how I did my test and came away with a result of 1-2% so please tell me how the test was in error when the only variable was the aspect I was testing. Others have asked you for this test to be done before as well but you have ignored them. Until you do this you can't quantify your findings.

If you simply stated you were building these arms to improve drag then I would be right behind you but I can't agree with you when you start pulling numbers out of thin air just because you watched a few university videos.

I'm happy to redo and document my thrust test if you wish me to. It is a simple test. Your mathematical tests are based on a solid cone of air that can't escape the cone but air and fluid dynamics don't work that way. Otherwise why bother with wind tunnel tests at all? Shouldn't the numbers be on the money???

 

[Cyberdactyl]

For goodness sakes, quit with the smart-a** quips. You know full well I've been doing at least since early spring. The "university video" was posted yesterday. And I almost always use the ~ approximate symbol in front of virtually every percentage.

You can do the test over, but at this point I don't really care. But would be curious what you perceive is the efficiency curve to get to 100% loss from the numbers you quoted on 4/27.

 

[FinalGlideAus]

Pardon?? There is no smart Alec punn's intended. If you don't wish to prove your hypothesis then that is fine but it remains a just that until you do and the numbers really don't mean anything. Once again, I believe you are on the right track but I don't get why you ignore or get your back up when people ask for tests to prove your numbers?

The efficiency curve and thrust efficiency is what is which is very fldifferent for each application you put it into. That is why I like practical tests. It's a bit like the weather guy at the last gliding nationals who said the weather for the task on the day in question was going to be blue because his computer models said so but if he'd only looked outside he would e seen the cu forming as he was talking.

 

[FinalGlideAus]

Anyway, I can see that I am not helping you progress your thread here so I will try my best to stay silent from now on in this thread. Please continue your great work and I do really wanna see that quad in a video just because it looks so cool!

I apologise for upsetting you which I obviously have...

 

[cranialrectosis]

I just wanna see the video with the chunky looking little meat grinders on.

How did that fly? You said there was vibe but with a tri-blade there is always vibe. Did you leave a vapor trail when you did a punch out or what??

 

[cranialrectosis]

I'm pretty disappointed in the AfroSlims. I found they will desync on 4S. Here is a 22 second video catching one in the act. You'll hear the motor desync 16 seconds in. I had to record a few times to catch it, but that's certainly enough to not trust them.

The good news, if there is any, is it has yet to occur with 3S, and I now have run around 15 3S packs through it.

I'm curious if flashing to newer firmware will help. I bought these in early June, so I imagine the firmware is most likely a version or two back.

What do you suppose the copter does in the air when the motor makes that little 'jorp' sound?

 

[jhitesma]

What do you suppose the copter does in the air when the motor makes that little 'jorp' sound?

In my experience...generally fall out of the sky and hit the ground. If you're high enough you might be able to recover, but usually it means dirt nap.

 

[Cyberdactyl]

In my experience...generally fall out of the sky and hit the ground. If you're high enough you might be able to recover, but usually it means dirt nap.

Yep, I took it to work to show the guys early last week the unique sound and over did it by holding the throttle wide open a bit too long and exploded a prop and crashed. I knew it was likely and stayed over overgrown weeds so there was no damage.

I'm pretty sure the tips are resonating like a reed in a tuba.

The one I built for my brother does that too, but at a lower pitch. He has those purple 1300KV Rctimer motors with some cheap HK super flexible props. When I went to see him over Labor Day, I asked if he was ready for stiffer props and he said no. He said he still wanted his training wheels. .

I'll get some video of the stubby props but the video will be anti-climatic since applying any throttle above hover gets the cage to vibrating. And that's after spending a fair amount of time balancing them.

 

[cranialrectosis]

As I understand it, the KISS ESCs don't do this.

Is the difference the firmware or the hardware?

 

[Cyberdactyl]

I'm using TC's and simonK's love child, the $13 AfroSlims.

But understand, it's the cheap HK props. The HQ 0645 props don't do it and work outstandingly.