Have been building up a basic octocopter (already have other quads) based on cost looking to eventually go to a nice frame.

Whilst the Hobby King frame is nasty and cheap it is a start and for under $40 it seems OK (yes it has its problems)

My intention is to figure out best prop motor configuration for longer flights, etc.

Hobby King Octocopter frame - landing gear is woeful!!!

Turnigy 35-36 910kV propdrive motors with prop drive adaptors

12x4.5 props - at present

30 Amp Turnigy plush ESCs (wiring needs tidying)

2 x 3300 Turnigy 4S batteries in parallel

HK antivibration foam (orange) under a range video mount with APM 2.5 on top

Waiting for external compass and to mount GPS at present

Turnigy 9XR radio, FRSky module and receiver

3DR radio link


Intention is to put my brushless gimbal with Sony NEX5 on it for some video just for fun.

Have not done a compassmot or compass calibration to date but did actually fire her up and see what happens.

Jumps in the air alot more aggressively than the quad and the noise is a bit frightening, response to throttle was a bit more sensitive than expected. Was really stable in windy conditions during initial tests. Remarkably more stable than smaller quads I am used to.

Have not looked at tuning so far as only preliminary tests on stabilise.

Anyone looking to do the same thing happy to share experience or any advice or considerations are welcome.

Cheers 

Brian

Views: 4721

Comment by R. D. Starwalt on August 8, 2013 at 5:59am

Big build.

Is that a slab of foam rubber under your APM mounting plate?

-=Doug

Comment by Brian Donovan on August 8, 2013 at 6:07am
Comment by R. D. Starwalt on August 8, 2013 at 6:23am

Thought so. Dubro markets the same type of material in a few different thicknesses. HERE is one seller. I picked mine up at the local hobby shop but probably could also find it at a fabric store or sewing department.

I am trying a section of it on my 2nd scratch build, documented on Instructables HERE. Double stick 3M tape holds the foam to the APM on one side and to to the upper most (for now) plate.

There has been robust and lively debates on vibration preventing/mitigation on other threads. I hope to maiden the 2nd build soon and will take a look at the logs and compare the results to my rigidly mounted APM2 on my 1st scratch build. That aircraft is documented in my blog section HERE.

Build on! Fly often!

-=Doug


MR60
Comment by Hugues on August 8, 2013 at 9:01am

nice. what is the total weight without battery ?

The landing gear for such beast is indeed a problem that I have experienced with my X8 (Octo quad coaxial). Because of the weight and span of these crafts, the landing gear needs to be really solid and stiff. However that goes against being light.

I have tried to build my own landing gear based on openbeam system (squared aluminium beams that can be attached quite easily between each other at various angles). It was a really nice result but not stiff enough for the craft : it vibrated too much, especially in torsion.

I would also think about a cover on top of your electronics (to protect APM against sun light and heat which is known to cause issues).

Comment by Magnus von Rosen on August 8, 2013 at 11:24am

Hi Brian,

just to let you know, Iv'e been fiddling with the same setup since Christmas, just now getting it to fly good.

Also Hobbyking X930 frame, Turnigy 3536/9 (910kv) motors, 30Amp Afro ESC's, 2x 4S 3300mAh Nanotech, and an APM 2.5+, now running Arducopter 3.0.1.

Only last night I "cracked" both my loiter problem, and the landing gear.

Mine was going all over the place in Loiter, and RTL made you want to run for your life. The key to loitering was changing Loiter P from 1 to 2, and Loiter-I from 0.2 to 0.1. 

After that, loiter was pretty stable even in a slight wind, it would stay within 10-20cm. (a couple of inches?). Also tried an RTL which seemed to be doing well. I was going to try it some more, but while I was messing with the laptop and the Octo was in Lioter at 10 meters, it suddenly descended and went down within a few seconds.

Why? Because my Power Module is broken and awaiting warranty exhange, and I had forgotten my LiPo-beepers at home, the batteries got drained. One is now severly "puffed".

Anyway, drop me a mail if you want to exchange ideas and experiences!

Kind Regards

Magnus, Sweden

magnus@vonrosen.nu

Comment by Magnus von Rosen on August 8, 2013 at 11:29am

Here's mine from yesterday. As you can see I'm also using the 9XR and FrSky.

I bought parts from the Turnigy HAL-platform to protect the electronics and make it tidier.

Using 10x45 props for now, it was extremely trigger happy with 12" on. Perhaps I'll switch back to 12" when I have more weight on it.

The broken landing gear has been CA:ed with carbon inserts over night, now back and ready for new crashes!

Comment by Brian Donovan on August 8, 2013 at 2:49pm

Hugues - weight is 1.9kg without batteries, cover I have to do but sorting out GPS mount. Also might weld up an aluminium landing gear as cannot use the HK one.

Magnus - Thanks for the reply. Good to hear someone else has the almost exact same thing. Will start to mess PID tuning this weekend. 12" props, your description of trigger happy is much more accurate than mine. I think I will swap the props to 10" for more testing and as you suggest when more weight will go to 12" and see how that goes. Does look mean with the 12" props though.

Have to put on a cover so will look also at the HAL parts.

I have a lipo alarm coming from J-Drones. Also I have a Y connector to the batteries I don't like as if it fails I have nothing. Think I will solder another lead straight to the power distribution board. The concern I also have on the APM PM is the size of the wires and how delicate it is....this powers the APM and receiver so I am thinking this may need to be looked at.

The thing is so big compared to the small quads must be frightening when it crashed!

Comment by Magnus von Rosen on August 9, 2013 at 1:31am

Brian: Make sure you calibrate your ESCs, mine was hopeless before that, with my Turnigy Plush 40Amps (now replaced).

Do them all at once, with props off! https://code.google.com/p/arducopter/wiki/AC2_ESC

I was about 50 meters away when mine crashed, so not scary, more "what the heck is it doing, I did not request a decline?!". :)

Also, a great tip is to flash Open9X into your 9XR and do these two settings:

1. Use two switches to set 6 different flight modes: http://diydrones.com/profiles/blogs/mode-switch-setup-for-turnigy

2. Get the flight mode presented in the LCD of the 9XR (only works for 5 flight modes, so I have "loiter" in two of them) http://diydrones.com/profiles/blogs/setting-up-open9x-to-show-curre...

I got the HAL base plate and filed down the edge to make it fit into the HAL sallad bowl (top cover). This gives me an extra floor to build on. I also make my own suspension for vibration dampening of the APM. Hobbyking foam and wife's rubber bands, double, seems to work.

GPS is outside of bowl for extra reception.

Comment by Magnus von Rosen on August 9, 2013 at 1:38am

Also see about flashing your ESC's with SimonK firmware to get more responsive motors. This is why I changed from Plush to Afro, I did not succeed in flashing my 40A Plushes. I think the 30A ones are easier to flash.

This made a world of difference form me, it's much nicer and calmer now and doesn't move about when I try to maintain a hover. It was like it had a will of it's own before, going here and there in all direction during Stabilize hover. Now, not at all.

For PID tuning, I have only changed the Rate P but honestly, it's hard to tell if 0.12 or 0.15 is better. Both seem to work fine. Perhaps there is a more noticeable difference when in wind.

/Magnus

Comment by Brian Donovan on August 9, 2013 at 1:54am

Hi Magnus

Already done my ESC's. Might look into the SimonK firmware as you suggest even if it means replacing ESC's

My radio I reflashed with ER9X as per my old radio. Mode switches I have as you suggest already.

HAL bowl not sure I like to I might just mould/ vac form one.

My GPS is going to go on a DJI mount from goodluckbuy to get it and the compass up and away.

That landing gear still has to go!

Cheers

Brian

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