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May 18, 2014, 02:24 AM
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Discussion

Large APM Tricopter Fun


Several of us were discussing the portable multicopter for long duration flight with gopro gimbal. I've always flown quads, hexas and y6 but never a tricopter. just somehow, I never managed to build one mostly because I've always thought servo was added complicaton and my favorite multies were y6 anyway. one of the motivation was that I really like y6 and I was hoping that i would gain some of the benefit of Y6 without too much penalties

In the past, tricopter was popular because it could be built using cheap rates gyro without any special board. Also, motor/esc was more expensive compared to servo. After some research, may tricopter owners also stated that tricopter flew more like airplane or heli compared to true multicopter which tend to be very axial in turns. As long time heli flier, I really like how smooth heli can be flown, so, I decided to go for building a 15min flying tricopter with gopro gimbal and video downlink system using APM 2.6 flight control using 3.14 firmware.

I had few Dualsky 5010-9, which is 390kv motor with 15-4 prop, tunigy trust 6S esc flashed to bs.fet (simonk) , Tower Hobby TS160 servo (standard size digital cheap servo mostly because I had a new one and wanted to try cheaper, just to see if it will fly ok with it. had some nicer servo as backup just in case ) initially setup to run at 5v, but since changed to 6v. Since portability was desired, I needed the arms to be foldable. anyway, it took couple days to put this together and total weight with camera/gimbal and 6S5000 pack came out to 2.5kg . While standard servo is bit overkill, I really wanted this setup to be robust workhorse flier.

Initial Ecalc estimation flight time came to 16+ min hover and 9 min mixed flight. I find ecalc to give decent rough approximation and I figure I can probably get 15min of light flying with it. Tail pitch control unit was modified from some metal robotics parts. it worked out really well in that it is very smooth and solid. at 2.5kg, I am right at 50% throttle (or bit less) plenty of power


Initial flight was with default pid and mode switch setup to alt-hold, loiter and RTL using 4S pack. (no gimbal so total weight was 1800gm or so) taking off in alt-hold mode is not recommended for first flight as take off can be quite erratic. but it actually flew fairly well with default setting. bit too much wobble in gust though as I really don't like high P Stablize value so I dropped that down from 4.5 to 3.6 and raised the gyro P value slightly. this allowed it to settled down nicely the way I like. I've since raised the tail servo voltage to 6v from 5v and mounted the 3 axis gopro gimbal. (which should improve stability bit more)

after several pack and tuning/dialing the tricopter in, I have to agree that it flies a lot like heli more than multicopter. very smooth and controlled. Partly it is because it is bit larger sized and when I nose down for forward movement, it can build up speed fast. also I can fly very slow controlled flight. In alt hold mode, it literally zips about very nicely and holds loiter well. (as good as any) in gusty wind, it does wobble a bit, but with lower Pstab, the wobble is slow and not a problem (I prefer bit of wobble over shakes) it does fly fast forward very well. The motors come down totally cool after 5min flight, so I am not taxing the power pack at all. in fact, I am bit under recommended load for this motor. (which is setup for 50% throttle)

I should be able to get some inflight video over next few days. i am looking forward to having something that is relatively portable, with good duration and reasonable weight. may be this is bit overkill for gopro though and if I were to build another one, I may consider slightly smaller motor with 13" props on 4S5800 pack and try to go for sub 2kg setup with mini servo for tail but I am happy with how this one turned out . Still, 15" props sounds wicked at 6S speed and it is very solid flying platform. (much better than quad with similar disk loading) I just love seeing the back motor move as it yaws about and it has tons of power on 6S.

anyway, I had to do some work to tame the vibration, but I think I am getting there for video. I still need to tune my gopro gimbal before getting a nice flight in. I am pretty hopeful as last flight looked pretty good. Currently, this weight 2490gm with 3 axis gimbal and 6S5k pack. current draw is about 25amps. (less than 5c) for hover. should fly 15min and 17 min with 5800 pack. My goal is to mount rx100 camera and it should still fly 13min if I am careful about gimbal design. with 6S5800 pack. This should gives me comfortable 10min flight with reserve.


I've also built a slightly smaller version with 13" props. and move the gopro to this. this will run 4S5800 pack and still gives good flight time. the larger setup will be getting the apc 16-5MR props and will be carrying a nex5 I will adjust the front LG on that one to be bit longer to carry the gimbal.

I've thought about building a bigger unit. something with 22" prop and heavy load, but I just don't have the need for something that big

the rear esc is mounted inside the frame directly in line with the back tube.
Last edited by askman; May 28, 2014 at 07:24 PM.
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May 19, 2014, 05:30 PM
Destroyer of G-10
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finally after 2 days of tuning, I am happy with the setup.

I had to turn down my Stalbize roll/pitch P value 0.33 and my rate roll and ptich is set to .15 with rate yaw set to .18


Only thing that is not solid is alt hold. it seem to drift bit up and down. so I changed my throttle p to .6 and I to 1.2 as well as alt hold P bit higher as well and the alt hold became totally solid.


anyway, it does not wobble at all during descending or gust. flies like it is on rail. very agile with solid tail. I really think it flies as well as my Y6 now without the flight time penalty. I am actually thinking about mounting a 2 axis brushless gimbal and RX100 on it now and building a slightly smaller tricopter for the gopro gimbal.
Last edited by askman; May 19, 2014 at 10:23 PM.
May 28, 2014, 07:11 PM
TBs are GO!....FAB....no..FPV!
Phelec's Avatar
The photo I would really like to see (3rd one) is so dark. Can you take some more in better light? I would like to see how you mounted all your electronics.
May 28, 2014, 07:29 PM
Destroyer of G-10
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as I've updated in the first post, my escs are mounted so that rear one is inside in line with back tube. the other two eac for each front arm is mounted up front. this is same for both. APM is mounted on top below the battery plate. battery is mounted up top.

I've been playing with different propsize and I find that 13" is perfect for 2.1kg tricopter about 400 sq inch of disk area and 2100gm about 5gm/sq in. I've tried 15" prop but it really did not like heavy wind. (about 4gm/sq in) but it was more efficient.

I have built 2 unit with 13" prop, the second one will be getting the rx100 3 axis gimbal that I am working on while the larger unit will get nex5 gimbal. there are other options though, so I am thinking about what is possible. the 5010 motor can easily run 20" x6 electric prop if I go 4S and that would keep it under spec. props gets expensive but only need 3 same type. if I do that, I can easily run 4S 2P 5800 and fly for 13-14 min with big gimbal. (about 1.8kg load) hmm. possibilities. will have to rebuild it larger though to clear 20" prop. possibilities. I only have pair of 6S and loath to get more 6S packs since most of my stuff runs 4S. so much choices XD
Last edited by askman; May 29, 2014 at 12:43 AM.
May 29, 2014, 04:31 AM
TBs are GO!....FAB....no..FPV!
Phelec's Avatar
Thanks for the extra photos and specs.
Jun 05, 2014, 11:30 AM
Destroyer of G-10
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I've done more work on the tricopters. I've been doing lot of work on prop efficiency vs wind performance and I've found that 3S is much better with bigger prop. I've gone 14" APC MR prop on the smaller setup on 3S and planning on testing 16" APC MR on this. on the larger setup, my plan is to run 18" APC MR prop on 4S (390kv motor) . I've also changed the tail tilt unit using aluminum parts I've had from gimbal production. I've also upgraded to MKS burshless servo on the tail and it is smoother/better flying. while it flew well with cheaper servo, it just is more solid with good servo on the tail. I will post pics later on.

I have another blog coming on prop efficiency and how to setup multicopter for longer duration.


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