Hi All, Just pulled this image in from SUAS News (Thank you Gary) to illustrate a few really good concepts that it incorporates and talk about better Multicopter design a bit.
This copter has a lot of things right and is really a study in design excellence.
1. Most obvious is a sliding ball full enclosure camera Gimbal, very pro and really something we should be striving for.
2. The motors are on the bottom under the arms: More aerodynamically efficient with no prop wash interference and very little intake interference. Noticeably increased flight times and greater lift capability and much quieter.
3. Large slow high efficiency props and pancake motors: These are way more efficient than faster motors with smaller diameter more conventional props.
4. Carbon fiber aerodynamic frame arms: Again more aerodynamically efficient, light and strong.
5. Fully enclosed framework and a simple spring loaded landing gear that provides as little interference with the prop wash as possible.
Basically this quad incorporates the best design features I have seen so far and definitely provides food for thought.
I thought it might be worth soliciting comments and other thoughts about optimal multicopter design techniques.
Best Regards,
Gary
Comments
@Denny "The more motors you have the less efficient it is". That's not entirely true.
See Andrew's comment, "Then there are ducted fans (EDF) most all of which have the hardware on the intake side...could that be wrong? "
More ducts=more efficiency.
Air intake is super important and shouldn't be underestimated :-)
:)Denny Rowland , Im doing a similar thing now in Uganda, but bird nests are in trees and is only a small percentage of my work. Doing it for fun was great but when it becomes a job and doing it day after dreary day, it makes you want to just get a foamy and get back to basics again. Shouldn't complain tho, I do consider myself blessed and should be more thankful:) Thanks to Chris and the 3DR team that got me going on the APMV1.0 all those years ago!
Choppy
I had an interesting assignment last year which was to photograph hundreds of Vulture nests on the side of some vertical cliff faces that led down to the sea. I had to fly within 3 feet of the nests so that the eggs could be counted which demonstrated the effect you are talking about the closer you get, the greater the Bernoulli effect drawing you in closer and closer. I was operating from a small rib in the sea so that I could view from below and judge my distance. It was a very tough job.....
@Andrew Rabbit, Thats where I was partly getting my conclusions from, ducted fan theory/ white man magic. Any impediment or intake reduction can reduce airflow thus need more power for the same amount if thrust.
The other area is from doing a helicopter CPL course and I remember when I wasnt sleeping or staring out the window something about Vortex Ring State and how walls or anything close to the tips of the rotor blades can induce more VRS and give the sensation you are being dragged into the wall . Just maybe when I get home to OZ, I'll do a test on long and short arms?.....Too many projects.....
With the use of a tri-copter and Panasonic NCR18650B or the GEB8043125 batteries. An endurance of well over two hours can be expected. The Tri-Copter has a vane steering system so no rear motor steering is required.
The more motors you have the less efficient it is.
The endurance model forms the basis for a cameraship with APM2.6 and the new style gimbal. It will have persistent stare capability for at least an hour. With a locked in pointing accuracy of .005 deg.
Hi All, with Simons test showing negative results, could it be possible that the induced airflow above the prop disc has been impeded by the center section airflow being turbulent? Maybe the arms can be longer to eliminate any chance the body is producing less than ideal conditions for the entire disc area to receive vertical airflow from above?
Yes Oliver I did, the props stayed the same, only the motors were inverted.
Sorry for confusing you.
@Andrew I gave my TBS away after one of my customers handed it down to me.
No offence Trappy, i don't like it, but thousands of people do, so that's cool :-)
Simon
I have done some lift tests for an endurance attempt that I will be doing with a tricopter. The current best motor prop. configuration I have tested is with the multistar 390 kv motor and the 16.5 foxtech supreme prop. With the motor on top of the arm I get at 400 grams of lift a current draw of 31 watts. with the motor underslung it is 30 watts. A slight improvement but the arm on my test rig is only 5/8" square section. In comparison to say the new 25min endurance Phantom Vision this motor prop. was tested at 400 grams of lift and it drew 67 watts. So nothing very spectacular there.
This rig is also able to measure vibration levels which has led to some further gimbal design innovations. The normal brushless gimbal controller is able to control another type of motor. Known as the voice coil actuator the name is taken from the use of this type of device which vibrates a paper diaphragm in your speakers. however they have applications for accurate and very fast linear movements. The problem with brushless motors is that they have very poor torque hold and are not linear. The use of coil actuators are found in all mill spec. inner axis camera stabilizers which attenuate some vibration frequencies as well as small highly accurate movements, typically only a few degrees. I think a separate discussion is needed for this.
The carbon chassis is just a TBS Discovery frame that I knicked off the web. The arms are identical in dimensions to the DJI Flamewheel whatever they are. I need to put a bit more work into the design as well as figuring out how the motor mounting and cooling will work - I have a few ideas here - but the arms can be attached to anything that uses these pick-up points - in Solidworks at least, for now.
Nice link MarcS :-)
I shall try that John and be more thorough, i just wanted to prove my point.
Now that looks awesome, Like a spider.
I have a problem with frames that have battery weight in the bum and camera up front.
I think a copter needs to be symmetrical, the only gain having a frame shape like above is my camera is clear of view.
Which huge positive, but the negatives for me personally out weigh them..
Still it looks sexy :-)
Simon
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