Calling all Compass 6HV helis with SK-720!

[Castel]

Originally Posted by J0hnny007

I'm actually out of town right now and have the servos at home to install when I get back. They will be running at 8.4v regulated off the bec them dual step down to 5.2v for the tail. I'll get her airborne in a couple weeks with pics. I actually opened my frames and mounted all wired and the power bus between the frames.

Good to know, thanks for the reply! My setup is the same as yours with the power bus inside the frames for a tidy look although I didn't open the frames (maybe it would've been easier, it's tight in there!). I have a few pictures of my build in my build thread for reference if it helps:

https://www.helifreak.com/showthread.php?t=298482

I will be really interested in hearing how you do with your maiden and how it flies! Good luck with it a couple of weeks from now.

[boltor]

Originally Posted by Castel

can you tell us how your vibes look during the playback?

I get in the order of 2-4 (in V2.4 terms), sometimes marginally higher. I'm a sport flyer - loops, rolls, flips, careful inverted, so not a good measure of vibration. Looking forward to seeing the new vibration logging on V3.01 and will report back.

Originally Posted by Castel

How high do they go on hard maneuvers?

sometimes up to 5, but rarely

Originally Posted by Castel

What RPM are you running, governed?

N=1900, FM1=2000, FM2=2100. Do most of the flight in FM1.

Originally Posted by Castel

Did you set the phasing as in the manual?

[UPDATED] Yes. +4 needed.

Originally Posted by Castel

I guess you are using the stock 20mm servo horns, do you get any pitch up during FFF? Any bobbing on sharp elevator inputs?

Using Dubro horns, but yes, 20mm. No pitch up or bobbing.

[boltor]

Originally Posted by heathy

Boltor, Johnny whats your vibes @??

I need to know if low vibes are achievable before i jump to Mikado

Heathy - sorry to hear of the crash. I get 2-4 typically, but sometimes up to 5. I don't get too worried about this as everything seems to work fine.

Going to Mikado? I'm about to get another SK-720 for the Protos, given the way its worked with the 6HV.

[Castel]

Boltor thx for the detailed reply. My setup and vibes are similar to yours. The onlystrange thing is that in order to get absolutely 0 interaction of elevator with the blades lengthwise as in the setup in the manual I needed -4 degrees of phasing. At 0* it's small but it is there.

Did you have to adjust any particular gains or just TX gain to make the cyclics
good? I guess you also have 12*/10* collective/cyclic?

[boltor]

Originally Posted by Castel

Boltor thx for the detailed reply. My setup and vibes are similar to yours. The onlystrange thing is that in order to get absolutely 0 interaction of elevator with the blades lengthwise as in the setup in the manual I needed -4 degrees of phasing. At 0* it's small but it is there.

Did you have to adjust any particular gains or just TX gain to make the cyclics
good? I guess you also have 12*/10* collective/cyclic?

Castel - my apologies, I wasn't accurate with the answer on phasing. Just hooked it all up and found it was actually +4. Interesting it is +ve and yours was -ve.

Yes, 12 deg / 10 deg approximately.

The only thing I need to sort out now is to get the SK-720 governor working (seem to have a 200 rpm difference for some reason) - see https://www.helifreak.com/showpost.p...5&postcount=69

[heathy]

So i have 0 phasing , and between you 2 + - 4 ,
How is this worked out, got to admit its something i didn't even check as leaving @ 0 was mentioned in the compass forum, due to this being built into the head!

Very odd

[Castel]

Thx Boltor. It might be that I am confused and I have +4, my bad gotta check. That +4 makes sense.

Heathy, I initially had it at 0 but saw some precession when in hover, the heli was doing small circles (toilet bowl effect I believe they call it?). With +4 it's fixed.

[Colonny5]

This is a great thread and will help me as I am in the middle of my build. My setup currently has the following:

- SK-720 with powerbus, v 3.0
- Hobbywing 70A ESC
- Hyperion Atlas DS20x-SMD Cyclics, DS20x-GCD Tail
- Stock dampers
- Stock tail blades
- CC BEC Pro

Heathy, I am guessing since we are using the same servos I should remove the spacer on the pitch servo? And how did you mount your tail servo, from the outside or the inside? Mine is currently mounted from the outside with the small white spacers that came with it.

[georgi UK]

=] its a brilliant thread, we need more like this!!

georgi UK

[johnjonfenomenon]

johnjonfenomenon
- SK-720 with powerbus, v 3.01
- Hobbywing 70A ESC
- kbdd lime dampers
- Align DS610 cyclic DS620 Tail
- KBDD Extreme edition 96mm tail blades
- Western Robotics Hercules Super BEC
-Edge 623 FBL blades

Issues occuring at the moment
1) SL. seems like I have a cold calibration on my gyro sense
as when the heli is on the bench, It is detecting motion on the aileron, elevator, and rudder. Over time as it sits longer the readings go higher and this in turn makes SL useless as it will bank the heli. This has been confirmed by Art and my sk will be sent back in for repair.

2) Tail wag while using the governor feature.
My rpms are set at
1650
1950
2100

Gyro Tail gain 40
Governor gain 35

[boltor]

Two test flights today with the new V3 software, including the use of the SK-720 governor. I have always used the CC ICE 80HV governor, so was interested in a comparison.

Both good flights, although noticed a little wag in the tail. Not much, but enough of a difference from previous flights. I had the following gains:
Rate: 66%
Hold: 53%
Acceleration: 1%

I have previously posted about an error in the RPM reading on the CC ICE data viewer. I now think that I had previously set up the governor in the CC ICE incorrectly - was using a low ratio (9.45), not the correct ratio of 10.4. This (I think) led to a low head speed and hence the higher gains needed. Now I have the right RPM (FM1=2000 RPM), this gain was too high and led to wag. So, I just need to reduce the gains to fix for the next flights.

Below are the two logs - one from previously using the ICE CC governor, and one from today using the SK-720 governor. As you can see, the SK-720 holds its own very well (and that's before CC release new software to deal with external governors). Note that I was using the recommended heli mode / fixed endpoints / accel gain = 10 for the CC ICE.

So, overall, the V3 governor seems to work well. Just a little tweaking of the tail gains required to reduce the wag.

SK-720 Governor:


CC ICE 80HV Governor

[boltor]

@Castel - you can update me in post #1 to V3 software now, thanks.

[Castel]

Hi guys, thanks to all for the replies. I am typing on my phone, I'm on a roadtrip but I'll be home in 2 days. I'll update the first post as soon as I am back on my PC!

[heathy]

Originally Posted by Colonny5

This is a great thread and will help me as I am in the middle of my build. My setup currently has the following:

- SK-720 with powerbus, v 3.0
- Hobbywing 70A ESC
- Hyperion Atlas DS20x-SMD Cyclics, DS20x-GCD Tail
- Stock dampers
- Stock tail blades
- CC BEC Pro

Heathy, I am guessing since we are using the same servos I should remove the spacer on the pitch servo? And how did you mount your tail servo, from the outside or the inside? Mine is currently mounted from the outside with the small white spacers that came with it.

I have mine on the outside and no spacers, just screwed it to the frame, also the instructions say to use 2 spacers for the pitch servo, this pushes it out too far making the links @ angles. So no spacers needed here!!

Just checked my tail servo ball spacing too, its @ 13mm [ think i said 15mm before ]

[Castel]

Colonny5, good luck with your build! I added your info, I hope this thread helps, Heathy has almost your same setup and he has no strange behavior issues so it's a good reference point. Let us know how it goes!

Originally Posted by gmcallister

=] its a brilliant thread, we need more like this!!

georgi UK

Thanks Georgi!

Hey Boltor, I updated your info for v 3.0, thanks for sharing your info and the log graphs. Good that v 3.0 seems to be working good for you.

Heathy, I used the spacers. You mentioned 2 spacers, are you referring to a single one on each side of the servo right? That's how it's supposed to be, it sounds like you were trying to stack 2 on each side? Regardless I don't think it matters or that you should change anything, you have no bad behavior effects so you are good . My tail ball spacing is 15mm... it's working as is so I won't change it .

[Castel]

John, I updated your info as well, interesting that you are not using the stock blades. Let us know about your issue and how you fixed it. Once you confirm when it's back from Skookum, I'll add it to the first post for reference.

For your tail wag with the governor, do you have a pulsating throttle or is it constant? I ask because we have the same ESC, I tried it but at the default 50% Gov gain it was giving me a pulsating throttle which created tail wag. I reduced gain all the way to ~15% and I think it made it worst. Increased it to ~65% and it was better but couldn't keep on testing. Let me know what you end up using as I would like to cross-check and see how you fixed it. Also, what sensor are you using, Hyperion, EagleTree, Spektrum?

[heathy]

Originally Posted by Castel

Colonny5, good luck with your build! I added your info, I hope this thread helps, Heathy has almost your same setup and he has no strange behavior issues so it's a good reference point. Let us know how it goes!



Thanks Georgi!

Hey Boltor, I updated your info for v 3.0, thanks for sharing your info and the log graphs. Good that v 3.0 seems to be working good for you.

Heathy, I used the spacers. You mentioned 2 spacers, are you referring to a single one on each side of the servo right? That's how it's supposed to be, it sounds like you were trying to stack 2 on each side? Regardless I don't think it matters or that you should change anything, you have no bad behavior effects so you are good . My tail ball spacing is 15mm... it's working as is so I won't change it .

Ivan,

Its the black rectangular spacers that the instructions say to put behind the servo tabs and on top of the frame, pushing the servo out, 1 on each side!
The hyperions don't need these as it makes the link angle inwards. Looking front on.

I watched the finless build vids, and he mentioned it too, so had a look at mine. Sure enough he was right!!

All 3 are perfectly straight.

[Colonny5]

Originally Posted by heathy

I have mine on the outside and no spacers, just screwed it to the frame

My build is slow going doing what I can when I can. What I noticed so far is the Hyperion servos have a small rib on the screw tabs between the holes so I can't mount the tail servo flush on the frame from the outside unless I use a small spacer. I hope that wont matter much to the tail. The other thing I noticed is my tail pitch slider is a bit rough not smooth at all. First thing I will try is some oil and see how much that helps.
Also does anyone have a photo of how they have their power bus mounted? Routing wires seems to be a little frustrating to me.
Anyone experience anything negative with using the stock (warped) gyro mount?

[boltor]

Originally Posted by Colonny5

Also does anyone have a photo of how they have their power bus mounted? Routing wires seems to be a little frustrating to me.

Current setup is shown below. Took a bit of time to get the wiring sorted. Note that the curent update with the Hyperion phase sensor is not shown.

[boltor]

Originally Posted by Colonny5

The other thing I noticed is my tail pitch slider is a bit rough not smooth at all. First thing I will try is some oil and see how much that helps.

Suggest:
1) Resize the ball links on the tail grips if you haven't already.
2) If the slider is still stiff with the tail grip ball links popped off the balls, disassemble the articulating arm that connects the slider to the tail case and file/sand down the areas where the pieces rub together.

(see https://www.helifreak.com/showthread.php?t=283784)

sorry for OT, not really SK720 related (but it will get you in the air quicker and enjoying the magic of the SK720 so all good!)