I thought i would share my hexacopter build with the world, it's not finished as of yet but it is getting there.
This is my second multicopter build; the first being a quadcopter which i may make a build log about as well but basically it was to see if my choice of building materials etc would hold up with the hexacopter project.
Components I am using:
- NTM Prop Drive 35-36A series (1800k/v @ 875W)
- HobbyKing Redbrick 80amp esc
- Ardupilot Mega board
- Megnetometer
- Xbee Pro Telemetry
- GPS Module
- Spektrum DX8 tx/rx
- 10x4.5 props
- Carbon Fibre square tube 6mm
- Carbon Fibre sheets 300x300mm
- M3 nuts,bolts etc
- 3Amps @ 5v Micro UBEC
- Turnigy 5Ah 3cell (11.1V) LiPo (x2) (havent purchased yet)
- Assortment of silicon wire (24awg, 14awg, 10awg, 4awg)
- Assortment of plugs etc
Thought i'd better edit the post and add some of the first pictures i had taken...
Now only if i had access to a laser cutting or CNC machine... one can dream i guess. Main chassis plates:
Motor "mounts". Yes you may say i did a poor job of the mounts (not very well designed) but i wanted a light mount (so i could keep frame weight to a minimum) and something nice looking. I didn't go the modular approach with any of the frame design as i didnt see the point in my circumstance. to change the motor incase one breaks there are 4 phillips head screws i can undo to get it off. The roughly cut x-brace under the motor was to see how well it would work with a brace there. The gap between the 'shafts' on the arms is taller now and the x-brace is nicer to look at ;)
Getting ready for the assembly of the frame :)
Bog roll there was to wipe off excess locktight and i was sick at that stage and we had run out of tissues...
A third of the way there... thinking this thing is going to be huge. Always looks bigger off paper
Mainframe assembly complete. motors attached and escs placed where i think they should go.
Comparison next to my quadcopter:
Power distribution looms:
I will upload more pictures as i make progress. i will receive a new esc next week as well as the rest of the components i'm waiting on.
To do:
- Battery tray (another sheet of carbon fibre (hexagonal in shape) that will be suspended underneath the mainframe centre)
- Landing gear (not sure on how to tackle this yet)
- Connect electronics
- Find a method to mount the Arducopter Mega in between main frame CF sheets (throught the hole in the top sheet)
- Make up some brackets to mount GPS, Xbee Pro, Rx onto
- Probably numerous other small things
I would put down weights and stuff but as i havent finished the build it is a bit hard to say, but weights so far and projected weights are:
- Mainframe with escs, motors and all heavy wiring = 2100 grams
- Mainframe by itself = 600 grams
- Battery weight = 860 grams (10Ah)
So total flying weight im hopeing for is 3000 grams but i've given myself a worst case senario of 3500 grams.
Total lift with 10x4.5 props = 17.4kg (i was hopeing for more but because they are such high rpm motors the best props i wasn't able to find in both puller and pusher)
So worst case senario power:weight is around 5:1 so i could get around a 10kg maximum payload i guess (still gives me a 2:1 power to weight); I would have to wait and see about that though.
I tested power consumption of the motors with around 3.5kg of weight and i calculated i will have around 15 to 20 minutes flight time without a payload and i have made enough room for 20Ah of batteries if i want that bit extra flight time.
So far im happy with the frame and its strength. it takes considerable force to even move the arms and bend it.
If you want any pictures taken of it and uploaded i'm happy to do so and any feedback would be greatly appreciated and if you have any questions i will do my best to answer them as soon as i can.
Regards,
Jamie Good
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UPDATE:
So after a couple days of work and study i have had a part day to work on the hexacopter. Today i had my first flight (didn't go above 1 metre from the ground). There will be a couple hours of PID 'tuning' to do to get it to fly nicely. At the moment hover is at about 35% throttle (thats with a linear throttle curve). My hover power consumption estimations were a bit out as in hover the maximum i recorded was 54 amps (instead of my initial prediction of 40 or so amps) so my flight time with 10Ah of batteries wont be what i predicted.
The main components adding greatly to the weight I still have to make/install are landing gear which i hope to do as lightly as possible and i need to add another CF 'layer' to hold the batteries (unless i figure out another nice,clean way to hold batteries). so im hoping i will only have to add another 300 grams or so... fingers crossed.
I was wanting a video to post now but as my partner wasn't home and i dont have a proper camcoder etc (have to use our phones) i will need to wait for her to get home. Hopefully my batteries will be charged and it will still be light by that time so im hoping i can upload one tonight.
If anyone knows of an easy way to tune the PID values could you please let me know? as of now i am flying, landing, adjusting (up or down as needed) which is very time consuming and annoying.
Thankyou,
Jamie
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UPDATE:
Second ever flight. I changed the PID values a little to make for a 'smoother' flight... but they are a long way off from where they should be. Again if anyone knows an easy way to tune them it would be awesome if you share them.
Hopefully i can get these settings calibrated and frame finished so i can upload a proper flight video for everyone. Can;t wait to get a camera on it!
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UPDATE:
Took the copter out again today to show a couple mates. Still haven't touched the PID values but i plan on doing some tonight after learning that i can adjust each value via channel 6 (the pot) on my Tx, which should make things easier. All components are still sitting ontop of the chassis which isn't ideal as the IMU isn't level with the copter but i can just compensate with the controls :P.
Nice windy day at the beach :).
"Can it land on the table?"
"I Guess..."
Flying in a Garage... dont you just love Prop wash?
Also here are some pictures taken from the day. Please excuse the mess sitting ontop of the chassis :)
After a couple minutes of tidying the electronics i have a couple things where they should be...
Also while i'm thinking about it, i need a way to tell the orientation of the thing while its up in the air... i was thinking maybe some fluro orange tape or paint and make an arrow or line underneath a couple of the arms... any ideas?
Comments
Really very nice frame !
Thanks for the info, I didn't know that props could go that fast.
What type of 10x4.5 props are you using? The "official" SlowFly types?!
BTW: that's really plenty of thrust!
Wow, a lot has happened since my last comment. I'll try answer as many questions as i can.
First off the torsion through the arms is minimal, if you try to twist them it takes a reasonable amount of force to twist them however i am not conerned about this at all because there is major force really twisting the arms, all i can think of are small vibrations from the motors not being balanced or the props being off. i have a prop balancer and i plan on balancing all props to the best of my ability.
Thinking about it now i would have preffered to use a larger carbon fibre tube, maybe two 12x12mm or larger CF square tubing as it would have allowed faster progression and a less complex frame, but i had the 6x6mm CF rods on hand and i decided to go with them.
The high k/v nature of the motors i am not worried about... it really just means i need a different prop compared to a low k/v motor. My quadcopter had 800k/v motors for which i used 10x6 props for. We can argue all day long about energy requirements of higher k/v motors but overall we will come to the same result.
When i first received the motors and controllers (was my first order) i made a rig to test produced thrust and i also purchased a 100Amp power meter. I was getting around 2900 grams of total thrust out of these props (although this test was close to the ground so the "efficiency" of the propellor is increased, therefore i would expect a little less thrust up a couple meters up).
Once the frame was completed i also mesured my power usage. I connected my watt meter, battery etc (didnt have ardupilot connected) to all 6 motors. I added a bit over 1kg to the body of the hexacopter (to make up the maximum estimated flying weight) and placed it on a set of scales. I increased motor rpm until there was a reading of 0 on the scales (meaning the hexacopter was supporting itself) and looked at the current draw. It read at around 42amps.
Now if i have 2x 3cell 5Ah batteries it will give me a total of 10Ah' of capacity. so i calculated flight time:
42/10 = 4.2 --> 60/4.2 = 14 minutes flight time (highest weight estimation)
Therefore i concluded i would have between 15 to 20 minutes of flight time if i had 10Ah of batteries (i am fairly certain that the completed hexacopter will weigh less than my max prediction).
Now Mr Aranghelovici i don't appreciate your responses to my post. If you wish to provide critisism, feedback etc to myself can you please do so in a pleasant manner.
I won't be doing another test of the motors i am using so i can take a video of it as proof to you that they can achieve said thrust/power levels as i think it is a complete waste of time.
The components used in this build were not purchased just because they looked cool, there was thought, and planning involved, i dont believe i need to go through them with you considering the way you've gone about your comments so i'll leave it there.
As i said before in the post, i am open to feedback and CONSTRUCTIVE critisism if done so nicely. If no one agrees with anything i have said in this post feel free to let me know and i'll be happy to discuss it. No one knows everything and everyone can learn off each other... isn't that what forums are all about?
Hopefully i can help readers and commenters can help me.
Weight Scale (field test) indeed...
I am concerned about the high Kv as well.
The thrust figures you tell, are the theoretically calculated, or field tested somehow?
PS: Like the nice and simple Pwr distro design!
@ Renato Aranghelovici , I own two of those motors, reach 3,8 Kg trust wooooowww (4s) but I must agree about the torsion, I'm going to copy this setup, but gonna use 1 square tube of 12mm (carbon fiber) istead the 4... lets see it soon...
Well, after an 5 hours search at ebay, I found a chinese dealer of Carbon Fiber, named "happychoice2009" lots of tubes, square tubes and sheets, and even props, I'am going to ask if he could make the 10x3 Ok....
May I point out to the good Mr Aranghelovici that we are not on facebook here?
Here we are all peers, newbies and veterans alike and we converse in a gentlemanly and amiable tone. It is quite in order to put forth criticism if it is performed in a sober and respectful manner.
Perhaps, if we ask him prudently jpknobel will tell us how he came to his conclusions about the performance specifications that he is expecting? If it turns out that he can be proven wrong we may correct his mistakes and all will benefit from the proceedings.
These are good points- things that the OP may not have considered.
Don't take offense- we're just trying to squeeze some knowledge out of you to help a possible noob. ;)
Try to keep spirits up :)
Wow, that's harsh. :) Can you point out some specifics? You know, to help out? Are you concerned about torsion of the arms? Weight? High Kv motors?
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