Okto XL - total loss, now I need a new one

[nataq]

Hey all,
I´m new here in this forum. So: "Hello" ;-).

I just made my worst mistake in regard to multirotors, killing my 3 month old Okto XL. All my fault - not even a flying mistake, incidentally I just pressed the wrong button on the radio control (reversed channel1 while it was standing on the floor with motors running - and it was crashing full speed into the ceiling of my photostudio, turning round and full speed into the floor). Had a hard time turning off the motors since I didn´t realize I reversed the channel.
Well, it´s a total loss - at least I don´t want to lift off with any of the parts anymore, they just look too messed up.

OK, so here I stand at the start again with some more experience than 3 months ago, looking for your help on what to buy.

What I liked on the Okto XL was the rather light weight
What I didn´t like too much was altitude hold (I saw much better on the net) and the feeling it gave me when I put my 5DII down below - it just soared as if it would explode anytime (sure that might have only felt that way, but still it didn´t give me the highest trust level.

I wish you guys could help me making a decision on what to buy - what are the pros or cons of your systems (knowing MK

• I will use it mainly for filming and photography. Perhaps the heaviest piece of Equipment it will lift is a 5DII with 17-40L lens - so around 1,5kg.
• still would be great if there was still some comfort lifting that weight though, because with the 5D, the Okto XL was already pretty "busy".
• If possible I want to keep it below 5kg all together
• I´d prefer 8 motors due to redundancy
• I was already playing with the thought of a 5s-upgrade before the copter crashed, so maybe that is an option.
• I´m also playing with the thought of getting a 3-axis gimbal (HiSight SLRII is also pretty destroyed)
• I´d say a maximum price would be around 5.000€ all together, but I still need to make up my mind if I want to spend that much.
• I´ll definitely not buy an RTF - I didn´t when I first purchased the OktoXL and learned a lot in that time, so I feel more confident now to build a system.
• It would be great if it was easy to disassemble since I want to travel with it.

That´s it, people - I´d really really appreciate your help.

Thanks in advance,
Wolfgang

 

[ovdt]

Hello Wolfgang,

MK's Okto XL kit is pretty light, it gives a better flight time when compared to other heavy lift frames with the same components. But the weak side of MK kit is, it needs quite good modification to make it a decent video craft. And instead of HiSight, I'd go for CineStar gimbal or AV200. I'd prefer Cinestar gimbal at this time.

So, if I were to build a new Okto, which I'll start in a few weeks, I'd choose these components:

* MK electronics.
* CineStar 8 frame or a custom frame if you can build one.
* CineStar gimbal or AV200
* Tiger MT2814-770KV motors (which are pretty smooth and reasonable priced) and each motor has around 2.2 kg thrust. It will be more than enough for lifting 5D Mark II. If you want more lifting capactiy, you can go with Tiger MT2820-830KV, 5s Lipo and 12" props. This is another option.
* JXF or Xoar wood props (14x4) (for 4s setup)


For a perfect Altitude Hold, I'd recommend you to use a transmitter like Graupner MX20 which has a throttle stick with spring. When the "Altitude Hold min gas" setting is adjusted properly with your payload, and Vario AH is used, you'll have a decent AH.

The downside of the MK Okto XL frame is, their Lipo holder is just crap. You need to use other landing gear like Droidworx Extended Landing Gear to get rid of it and gain some solid space for camera mount connection. This would be another route if you don't want to spend $1.5K for a good frame. Also it would be hard to dissamble.

 

[nataq]

Hey there,
wow - you seem to have a big lot of experience. Thank you so much for the insight.
CineStar 8 was something I was looking at - the only downside I see is that the total weight is going to be well over 5kg (11 pounds). And that would require a start permission here in Austria for every single flight from what I read. Even for training and calibration flights.
Other than that yours sounds like the perfect setup.

 

[Bartman]

a lot of the problems with MK altitude hold I think come from misunderstanding what it is supposed to do. You can't just park the throttle somewhere and expect it to stay right there.

There is a setting where you tell it how much to reduce the throttle when it exceeds the set altitude. if it's too low it drops too quickly and if it's not low enough it doesn't really respond well enough. if your throttle setting is too high (the stick is too far forward) it will use that to get back up to the set altitude and blast through the desired altitude only to come rattling back down. too low though and it will descend.

So the trick is to watch what it is doing and adjust the throttle so it is just above what it needed to hover. With this and the correct reduced throttle setting in MKtool, it will hold altitude pretty well and even let you move around a bit without drifting down or bobbing up and down.

Bart

 

[ovdt]

Hey there,
wow - you seem to have a big lot of experience. Thank you so much for the insight.
CineStar 8 was something I was looking at - the only downside I see is that the total weight is going to be well over 5kg (11 pounds). And that would require a start permission here in Austria for every single flight from what I read. Even for training and calibration flights.
Other than that yours sounds like the perfect setup.

If the weight is the main concern, maybe you need something custom basing on OktoXL frame. Customization will base on what camera mount you are going to use. If you use Av130 or AV200, you can directly purchase Droidworx Landing Gear. No need for other customization.

For instance, if you decide to use CineStar gimbal with MK OktoXL frame, you need to make bunch of mods.

1. Find a way to put batteries top of the electronics stack. You need some spacers and a very thick fiberglass / carbonfiber plate.
2. Find a way to put NaviCtrl + GPS on one of the arms. (You're doing this because you moved the battery to the top)
3. And put the Cinestar Gimbal to the bottom. Maybe you need to drill a few more holes to the mounting plate of the camera gimbal.

You can modify your current radio so it can also have a throttle stick with spring. No need to change. That's for more comfortable AH. I also advise you to read MombasaFlash's post for vibration solution:

http://www.multirotorforums.com/showthread.php?1611-camera-mount-vibration-looking-for-solutions&p=17270&viewfull=1#post17270

There are lots of combinations, so take some time to think wisely.

 

[nataq]

Bartman,
thanks a lot for the input. I was just working on a solution for the AH that´s why I was flying indoor and modified the radio settings - I wish I had seen your post before I started. Explanation on AH on the MK site is rather bad imho.

ovdt,
thanks again! I like the idea with the spring enabled in the current radio - I´ve disabled it because most of the people seem to do that. But now that I think about it again, I want to give it a try.
I´m currently leaning towards a complete Cinestar 8 set (frame, motors and 3-axis gimbal)
Regarding the vibration dampening on the OktoXL. I made a huge lot of tests and different modifications with the OktoXL (some didn´t work, but some worked pretty well) - and I had a really nice and lightweight system in the end with gel blocks.

Regarding vibration on the Cinestar: is the system ready to use, or does it require modifications on vibration dampening too?

Thanks again you two!

EDIT:
one more thing: when using the Cinestar 3axis gimbal with a second radio for the cameraman - is it possible to set nick of the gimbal with the left "throttle-stick" (sorry for my english).
With the OktoXL and the HiSight SLR II I used teacher mode of the radios and it wasn´t possible with Graupner MX-20 and Graupner MX-16 to set individual controls.
If so, how would the gimbal obtain nick and roll compensation from the flight control?

If it´s not possible, I might try to use the damaged flightCtrl from the wreck (there is no risk for using it for the gimbal, so I might give it a try). But would that work as a second unit?

 

[ovdt]

EDIT:
one more thing: when using the Cinestar 3axis gimbal with a second radio for the cameraman - is it possible to set nick of the gimbal with the left "throttle-stick" (sorry for my english).
With the OktoXL and the HiSight SLR II I used teacher mode of the radios and it wasn´t possible with Graupner MX-20 and Graupner MX-16 to set individual controls.
If so, how would the gimbal obtain nick and roll compensation from the flight control?

If it´s not possible, I might try to use the damaged flightCtrl from the wreck (there is no risk for using it for the gimbal, so I might give it a try). But would that work as a second unit?

The downside of using 3-axis gimbal and second operator is, you need a seperate controller which will handle the compensation of the Roll/Tilt axis. Yes you can try your Flight Ctrl but I think you should use some special firmware, I'm not sure about it.

With 3-axis, you are dividing copter into two parts. No cables should pass from these parts. They can twist while panning. That's why you need two controllers on the craft. There are plenty of gimbal stabilization units coming into play. You'll have bunch of choices in a month, don't worry about it.