Tricks to make S800 work great.

Joepapa

Member
Hi Guys. New to the forum, but not to the craft. I decided to post a positive S800 thread, because based on all that Ive read, the S800 is junk, but Im here to give others some hope. I have an S800 with Evo arms and the new landing gear vibration dampeners. I decided to put a GoPro Zenmuse on it while we are perfecting our 3 axis AlexMos gimbal to fly a 5D Mark III. The GoPro Zenmuse, being very low mass, was extremely sensitive to any vibrations, and lead me down a long road of 2 months to sort it out. I knew if the Zenmuse was experiencing vibrations, so would the Wookong, as both were mounted to the landing gear to benefit from the DJI vibration dampeners made for the S800.

In the end, despite balancing the new style DJI carbon props, and dynamically balancing the motors, jello and vibs were killing the video, and my confidence in the S800. The decal on the motors certainly throws them out of balance, and a little tape in the right places really smooths them out.

My brother is a custom fabricator in the automotive world, and often works with carbon fiber and fiberglass lay ups, and I showed him the youtube video of the carbon fiber arm mod. We decided to attempt it, and it was actually easy enough. This made the arms unbelievably rigid, but didn't solve the vibration issues at all.

Since both of us come from 3D helicopters, we have flown 450, 500, 600 and .90 size helicopters for years, we know how critical blade tracking is. Since the S800 15 inch blade tips come very close to each other, I thought about how flexible they were, and realized how during yaw and other inputs, some blades speed up, others slow down. As the tips flex up and down based on RPM, they don't track in the same z axis as the neighbor prop, and I quickly started to see that this is where a bunch of vibration could come from. I ordered Seacraft prop adapters and Xoar wood props. Despite being very well balanced out of the packages horizontally, the vertical direction on the prop balance test showed all the hubs to be out of balance. After fixing that, the first test flight showed the best video out of the S800 I had ever seen. I should have started with the props, but it took me weeks to figure out the flexing of the props was a much bigger issue than I thought.

In the end, with 15000 mah 6S packs, it hovers perfectly at mid stick, gives me a solid 23 minutes of runtime, and has between 20-30% left when I land. I have no concerns of this thing flipping over and crashing, and we have done tests where we weighted the craft to nearly 20 pounds to see if any problems would arise when we add the retracts and 3 axis SLR gimbal. Other than a Center of gravity change in the Wookong software for the IMU and GPS, no problems.

Hope it helps others.

Joe
 

Hi Joe, interesting article. I presume DJI give you those foldable props so you can transport it easily?
Where did you get your Seacraft prop adapters and Xoar wood props?
I live in France, I wonder could I get them easily here...
Thanks,
Louis
 

Teamflail

Member
Thanks for the information Joe. I have an Alware Streak frame, I know not top notch, with 14 inch props. Have most of the jello and vibration removed but I think the APC props are flexing quite a bit. I have some Xoar wooden props on the way and am hoping that will take care of a good portion of any extra vibration. I will make sure to balance both the blades and hubs, per your recommendation.
 

deluge2

Member
I don't think the OP has folding DJI props, he has an s800 with EVO arms, not an s800 EVO.

I don't think there are any adapters to allow 3rd party blades on the new EVO motors, at least not yet.

Steve

Hi Joe, interesting article. I presume DJI give you those foldable props so you can transport it easily?
Where did you get your Seacraft prop adapters and Xoar wood props?
I live in France, I wonder could I get them easily here...
Thanks,
Louis
 

Joepapa

Member
Yes, Deluge2 is correct. I do not have the folding props. Just the EVO arms and Vibration dampeners. I would be guessing, but I doubt the EVO motors are any different. Im willing to bet they just have a different hub mounted to them to allow for the folding props.

I am interested in the idea of 400 KV motors, as the 320kV motors are not perfectly suited to 6s Lipo with regard to RPM. A 320KV motor could handle more voltage, which is not an option on existing DJI electronics. The 400kv motor is more appropriate, should accommodate more payload, and may possibly even be slightly more efficient power wise, however I wouldn't mind testing them to see for myself.

On another note, I have the A2M IMU coming in tomorrow from RC-Drones.com to replace the Wookong IMU (v1). Ive read positive things about it and hope to experience and even higher level of precision. Keep you all posted.
 


deluge2

Member
Looks like the OP has the A2 IMU coming to use with his WKM, not the full A2 system. I suspect may be a v2 WKM IMU because I would be surprised if A2 IMUs are available separately at this early stage in the A2 system introduction. Both of these IMUs share the same machined aluminum case (though with different indicia). I have asked DJI dealers, but have not yet received clear answers regarding whether the internals are, or are not, identical.

Steve

Super stoked to hear about your findings with the A2 system! Cheers!

https://vimeo.com/74500759
 

Joepapa

Member
You are correct. Its the IMU V2 which should be the same as the A2 IMU.

Here are my findings...
Ive tried it mounted two ways, one in the main frame area (the original IMU location) and the other was on the horizontal mount that is included with the EVO vibration isolators.

I have decided to leave it on the external mount, so it can benefit from a totally vibration free environment.
Gains are much higher than original IMU...
I set Pitch, Roll and Yaw to x3 and adjusted while flying, then disabled remote adjustment and enabled remote adjustment on altitude, and so on.

I arrived at 250, 250, 250, 175, 130, 130
My s800 weighs just under 16 pounds with 15000 MAH 6S and Gopro Zenmuse

The conditions lately here in New England have been very windy and not ideal for video, however, with these settings, the s800 is very easy to fly and hovers in wind with stunning precision. Almost as if it stationary.
Before, when switching from GPS to Attitude, the s800 would drop about 1 foot of altitude. With the new IMU, it doesn't do this anymore. Wow, they have obviously made it more precise.

Lastly, I decided before filming yesterday to spend some more time confirming prop balance, and after a hour I have made each Xoar perfect. If you walk to the s800 while hovering and touch the landing gear, it feels like the craft is not running. Zero vibration. Because of the smoothness, I was able to remove a lot of extra measures I had made to dampen the zenmuse and Gopro.

In the end, I realize clearly that the s800 isn't a piece of garbage, its the props. They flex and do not track straight. It took a lot of time to figure this out, but now I feel like the s800 is professional level video. We are working on a gimbal to fly a Black Magic 2.5K camera, and I expect the S800 to be close to 20 pounds. I have no concerns of flexing, as the carbon fiber arm mod has made them rigid beyond belief.

Keep you guys posted.
 

Joepapa

Member
More good experiences guys. The wind has died down, we dialed back the gains to 200, 200, 200, 175, 130, 130. Video during a hover we shot last night literally looks like a still photo. Im seriously considering the bluetooth LED so we can adjust gains without having to constantly connect to the laptop, disable orientation control and reassign gains. As of now there is no way to disable the cam tilt in the H3-2D and use that channel.
 

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