Problems after F550 heavy lift conversion

[Cheezweezl]

Hey guys. Just found this forum and I'm glad I did. So I've been flying my f550 for a few months with zero issues. I bought it used and the gains were set up beautifully. Very smooth machine.


So now I want to add a gimbal and start flying something a bit heavier than a gopro. So I bought AVROTO motors and the arm extensions for the 550. I'm still using the dji esc's.


Ok so here is the problem. The throttle seems to go crazy at about 75%. When I say crazy, I mean it ramps way up, the copter does a front flip and goes down. The first time it happened on launch. A couple of the motor wires came out during the crash. I attributed it to bad cheap carbon props that maybe vibrated a wire loose. On my second attempt, I replaced the props with APC's that I first balanced. I also dialed the gains way down per advice from the hobby store clerk. This time it launched fine. It flew a little wobbly but wasn't far off. When I went to give it some throttle for a quick climb, it made a loud noise, flipped upside down and crashed. Lost an arm and the top plate is done but otherwise looks ok.


I noticed that that both times this happened, it seemed like I lost all control. When it flipped during launch I immediately cut the throttle and attempted to stop the motors. It just kept going for a few seconds. Then when it happened in the air, I did the same thing but it just kept revving out of control.


I dunno, it was flying beautifully the day before I did the upgrade. Any ideas?


for reference..


old setup: f550 with red motors and 8" dji props. Dji 30a esc's. Pulse 4s 3700mah 45c packs. Naza-m GPS Dx8.


New setup: f550 with carbon arm extensions. Avroto 2814 770kv motors. Dji 30a esc's. APC 11x4.7 props. 3s 6300mah 25c packs. Naza-m gps. dx8


While I am fairly new to MR, I've been flying RC planes for 12 years. So I know my way around balancing props, soldering stuff, and of course, crashing!!


P.S. I've very quickly decided that a heavy lift kit for the 550 wasn't the best idea. Moving to a carbon frame ASAP...

 

[gtranquilla]

I had similar issues with my F550 as a consequence of upsizing the motors. The flight controller cannot figure out what to do when the IMU sensors are affected by heavier vibration. As a test case simply use for Kyosho Zeal tape to isolate the IMU sensor from the airframe..... if the problem disappears, then you know it is vibration causing your problems.... then eliminate the vibration at source (not as easy with more powerful motors). Also isolate your RC receiver as an extra precaution. The magnitude of the vibration is a the angular momentum which is the imbalance weight x rpm x radius of the imbalance...... increasing very rapidly with larger motors.

Hey guys. Just found this forum and I'm glad I did. So I've been flying my f550 for a few months with zero issues. I bought it used and the gains were set up beautifully. Very smooth machine.


So now I want to add a gimbal and start flying something a bit heavier than a gopro. So I bought AVROTO motors and the arm extensions for the 550. I'm still using the dji esc's.


Ok so here is the problem. The throttle seems to go crazy at about 75%. When I say crazy, I mean it ramps way up, the copter does a front flip and goes down. The first time it happened on launch. A couple of the motor wires came out during the crash. I attributed it to bad cheap carbon props that maybe vibrated a wire loose. On my second attempt, I replaced the props with APC's that I first balanced. I also dialed the gains way down per advice from the hobby store clerk. This time it launched fine. It flew a little wobbly but wasn't far off. When I went to give it some throttle for a quick climb, it made a loud noise, flipped upside down and crashed. Lost an arm and the top plate is done but otherwise looks ok.


I noticed that that both times this happened, it seemed like I lost all control. When it flipped during launch I immediately cut the throttle and attempted to stop the motors. It just kept going for a few seconds. Then when it happened in the air, I did the same thing but it just kept revving out of control.


I dunno, it was flying beautifully the day before I did the upgrade. Any ideas?


for reference..


old setup: f550 with red motors and 8" dji props. Dji 30a esc's. Pulse 4s 3700mah 45c packs. Naza-m GPS Dx8.


New setup: f550 with carbon arm extensions. Avroto 2814 770kv motors. Dji 30a esc's. APC 11x4.7 props. 3s 6300mah 25c packs. Naza-m gps. dx8


While I am fairly new to MR, I've been flying RC planes for 12 years. So I know my way around balancing props, soldering stuff, and of course, crashing!!


P.S. I've very quickly decided that a heavy lift kit for the 550 wasn't the best idea. Moving to a carbon frame ASAP...

 

[Cheezweezl]

Thanks!!! So do you think moving to a beefier frame will help this?

I was looking at the tarot 680 and the similar sized bumblebee. Any thoughts on this?

 

[gtranquilla]

The primary reason for a larger frame is to allow for more prop diameter which makes it possible to improve increase both the maximum flight time and weight of the payload.
A smaller airframe forces you to select higher motor rpm and/or props with more pitch (both are less efficient)

Use eCalc for Multirotors to run thru multiple scenarios to gain a perspective on what you need. Start with your goals defined for AUW (all up weight) and preferred total flight time.
http://www.ecalc.ch/xcoptercalc.htm?ecalc&lang=en

Thanks!!! So do you think moving to a beefier frame will help this?

I was looking at the tarot 680 and the similar sized bumblebee. Any thoughts on this?

 

[Cheezweezl]

thank you for the reply. yes, that is what i was going for when doing the 550 arm extensions. i wanted to run big props on lower rpms for more torque, less speed. i noticed after installing the extensions and the bigger motors, the arms seem to have a lot of flex which seems to me to be a bad thing. my question is will the stiffer and lighter carbon frame help with my vibration issue, or make it worse?

 

[gtranquilla]

That is an excellent question but it has a very elusive answer......
Each type of material has it's own natural resonant frequency with carbon fiber composite being substantially higher that wood or polymide etc. and the dimensions also play a roll. Much depends on which frequency is affecting your IMU sensors, other electronic components and camera which can succumb to jello effect at specific frequencies. Even using wood versus cf props can shift these frequencies toward or away from the ones that cause the most harm. Eliminating the source of the vibration is your best solution. The remaining alternatives are to use vibration dampening and/or vibration isolation. Dampening can be done by sandwiching different materials together, each with a different resonant frequency as done with full size helicopter rotor blades. Engineers can use Comsol Multiphysics or equivalent software to control these factors even before developing a scaled prototype.

The problem with dampening is that it tends to add parasitic weight to the MR airframe as does vibration isolation, i.e., use of hollow rubber balls etc. Overall Carbon fiber provides the best solution as it has one of the highest strength to weight ratios of any material making the MR airframe extremely light. etc.

thank you for the reply. yes, that is what i was going for when doing the 550 arm extensions. i wanted to run big props on lower rpms for more torque, less speed. i noticed after installing the extensions and the bigger motors, the arms seem to have a lot of flex which seems to me to be a bad thing. my question is will the stiffer and lighter carbon frame help with my vibration issue, or make it worse?

 

[Cheezweezl]

that is an excellent answer. so it seems i have some serious tuning to do. and i'm learning that the bigger my ship gets, the more complicated all of this is.. but i want to eventually make some money doing AP, so i am in for the long haul. i'm convinced that i don't want to waste anymore time on the f550. i only plan to scale up from here and the 550 seems to be at it's limits or beyond.

with that said, i am looking for some advice on carbon frames (and anything else, really). i don't have droidworx or cinestar budget at the moment. i was looking at tarot and bumblebee. i can spend $300 on a frame at this point but that's about it. any words of wisdom?

thx

 

[gtranquilla]

I would recommend avoiding some of the cheaper carbon fiber airframes and holding off until you can afford the Cinestar 8 Octo basic frame that is sold on AliExpress.com..... search for octocopter and look for the one called cinestar 8 sold by FamousHobby shop in China........ But until then for a proof of concept MR airframe that will do an excellent job check out the RCT800..... from RCTimer..... Mine is shown in the photo here.View attachment 14654 It was specifically designed using eCalc to get me 15 minutes flight time and excellent aerial videos using a Hero GoPro3 Black c/w 2 axis brushless gimbal Martinez controller. I did aerial videos with it of an 18 hole golf course and would do mre except that winter weather has ended the golf season now.

that is an excellent answer. so it seems i have some serious tuning to do. and i'm learning that the bigger my ship gets, the more complicated all of this is.. but i want to eventually make some money doing AP, so i am in for the long haul. i'm convinced that i don't want to waste anymore time on the f550. i only plan to scale up from here and the 550 seems to be at it's limits or beyond.

with that said, i am looking for some advice on carbon frames (and anything else, really). i don't have droidworx or cinestar budget at the moment. i was looking at tarot and bumblebee. i can spend $300 on a frame at this point but that's about it. any words of wisdom?

thx

 

[gtranquilla]

Here is a high quality Hexacopter airframe hub in your price range.....
http://www.aliexpress.com/store/pro...copter-Center-Plate-SET/109347_930816543.html

With this you can always select some cheap aluminum tube from your local hardware store, build a flyable system then upgrade later to Carbon fiber arms etc. as you see fit.

that is an excellent answer. so it seems i have some serious tuning to do. and i'm learning that the bigger my ship gets, the more complicated all of this is.. but i want to eventually make some money doing AP, so i am in for the long haul. i'm convinced that i don't want to waste anymore time on the f550. i only plan to scale up from here and the 550 seems to be at it's limits or beyond.

with that said, i am looking for some advice on carbon frames (and anything else, really). i don't have droidworx or cinestar budget at the moment. i was looking at tarot and bumblebee. i can spend $300 on a frame at this point but that's about it. any words of wisdom?

thx

 

[Cheezweezl]

thank you for this info. i couldn't find one called "cinestar" sold by famoushobby but i did find this one this looks like an exact knockoff of the real cinestar. can i expect similar quality? for $600, it seems a little too good to be true. or is the actual cinestar just way overpriced? in the film industry there are chinese knockoffs of lots of expensive items. i've bought some of them and while some clearly don't measure up, some have been right on the money.

 

[gtranquilla]

I purchased the Cinestar 8 from FamousHobby Shop via AliExpress and could not be any happier. I suspect these come from the original manufacturer consigned to built these for Cinestar or FreeFly. Quality is absolutely tops. But if you dig in to the total component pricing there is not much of a discount overall...... according to some.

thank you for this info. i couldn't find one called "cinestar" sold by famoushobby but i did find this one this looks like an exact knockoff of the real cinestar. can i expect similar quality? for $600, it seems a little too good to be true. or is the actual cinestar just way overpriced? in the film industry there are chinese knockoffs of lots of expensive items. i've bought some of them and while some clearly don't measure up, some have been right on the money.

 

[Cheezweezl]

Great!!! I assume my avroto's will work ok on that frame. Any esc you'd suggest?


Sent from my iPhone using Tapatalk

 

[gtranquilla]

If you are examine the details on Quadrocopter USA website for the ARF Cinstar kit you will see they are pushing a $700 power distribution kit complete with 8 ESCs and an ESC programming module. The same can be achieved for well under $400 by purchasing Turnigy Multistar OPTO 45 amp Escs and a $2.00 programming card. Also if you look closely it appears that FamousHobby is selling the basic frame kit at a very good price (almost a loss leader) but gets back at you when you try to add the camera gimbal system c.w. landing legs..... these start around $1200!!!

One other item to keep in mind. The FamousHobby Cinestar8 kit includes a hokey power distribution plate..... just toss it and buy a HungryBoard power distribution module from HobbyKing for $15 and make some minor mods for a superior solution that can handle high current requirements without any issues. http://www.youtube.com/watch?v=_jPEyoc-F0Q

thank you for this info. i couldn't find one called "cinestar" sold by famoushobby but i did find this one this looks like an exact knockoff of the real cinestar. can i expect similar quality? for $600, it seems a little too good to be true. or is the actual cinestar just way overpriced? in the film industry there are chinese knockoffs of lots of expensive items. i've bought some of them and while some clearly don't measure up, some have been right on the money.

 

[gtranquilla]

Not sure.... I'll let you do your homework on that one. But what I can say is that I am designing to use 8 Turnigy Multistar 420kv 22 pole motors in conjunction with 15 x 5.5 CF paddle props and 8 Turnigy Multistar 45 amp OPTO ESCs all powered with parallel 6S 5000 to 6000 mAH LiPos for an expected flight time of 20 minutes with a Hero GoPro3 Black on a 2 axis Brushless Gimbal system..... but can accommodate a micro 4/3s Panasonic GH3 or even a small SLR...... would have to changeout the 2 axis gimbal system for larger cameras however.

Great!!! I assume my avroto's will work ok on that frame. Any esc you'd suggest?


Sent from my iPhone using Tapatalk

 

[Cheezweezl]

Man you are a fountain of good info. I owe you a beer!!!

So running the low kv motors on 6s is advantageous to higher kv on less cells I'm guessing. Buys you what? Flight time? Lifting power?


Sent from my iPhone using Tapatalk

 

[gtranquilla]

I have over 30 years experience in industrial electrical engineering including 10 years in industrial automation including wireless SCADA so Multirotors and just recently completed my HAM amateur radio course......so motor and speed control and PID loop control are NOT unfamiliar areas.

As the need for motor torque increases it becomes necessary to raise, not just the amp rating, but also the voltage level in order to remain in the sweet spot for electrical system efficiency..... basic laws of physics..... and as Forrest Gump would say......"that's all I am going to say about that"!

Have fun with your projects and do not be afraid to learn all you can.

Man you are a fountain of good info. I owe you a beer!!!

So running the low kv motors on 6s is advantageous to higher kv on less cells I'm guessing. Buys you what? Flight time? Lifting power?


Sent from my iPhone using Tapatalk

 

[Cheezweezl]

Smarter than me on the subject for sure. Im a cinematographer with a long history of crashing planes. So a chance to merge the two addictions is a chance I must take.

Cheers and thanks again for the info. Extremely helpful ;-)


Sent from my iPhone using Tapatalk