New Sab 700's with tail bob and shake issue on V8

Hello, I have run into an issue with the tail bobbing up and down and sometimes shaking side ways on my two new SAB 700 heli's. One is IlGoblin Pro and the other is IlGoblin KSE. KSE is 3 blade and suffers more from the issue. I posted on Mikado facebook, and Alex Wiehenstroth asked me to capture details and post here... I have added much more detail after his message:

----Alex Wiehenstroth: Sanjeev Joshi please write down the following things + copy your text from here to our forum to solve your issue together with the vbar development team. -heli - servo type - RPM - head dampers -flight values (whole model setup) - servo frequencies Thanks and much appreciated
----
servo types on both: Theta full size C1 on collective (333, 1520), T1 on tail (560, 760). Tail was set to 500, 760. RPMS tested from 1640 to 1950. Head dampers stock from kit -- 90 O rings + Delrin B dampers
My full history is this. I originally purchased 6 Evo links (pro, rescue) on V7. After website was working again, I upgraded all 6 to V8. Two of them on SAB Competition 420, Two of them on Kraken 580, and two of them on the two SAB 700's. My Kraken 580 has an upgraded tail (one tooth less in tail pulley and larger tail blades). The Krakens and Compeition 420 are flying amazing on V8. With my two 700's I have spent collectively at least 20 flights (between 2) to stop the tail shobing and sometimes shaking. On my brand new KSE I also replaced the tail feathering shaft and tail main shaft in case it was a mechanical problem. I tried head gains from 20 to 140, using stick direct from 40 to 20 and stop support from 20 to 40. The symptoms never went away completely. It was less in flying and much more visible when stopping or hovering. It also went down with increase in rpm. At 1950 rpm the bobbing was less than at 1700 but it never went away. If I managed to reduce it, when the wind changed, it came back again. I finally changed my KSE to v7, and used default settings except agility 120 and style 70. I tested KSE from 1700 to 2100 rpm, absolutely no head bobbing or shaking. I did not even reduce the gains while using this tri-blade. At this time, I feel my Kraken and 420's (4 heli's) are happy on V8 but my SAB 700's are happier on V7. Can you please help address? In terms of full set up data - I dont know how to give you since both are now on V7, but perhaps Mikado team can take it from the Cloud? I love Mikado and I am already a much better pilot in a few weeks. But it will be good to solve this V8 issue at lower rpms. Thank you.

Hi,

please try lesser refresh rates, on the head, like 200 Hz or even 166 Hz, start over with your preferred base setup (...) Button, and report back.
Could be that you can then up your overall gain significantly, and adjust with Control response, and fly happy ever after

I'm afraid it seems that some servos seem to work better with lesser refresh rates than the recommended/possible one, and Theta has come up a couple of times already.

3-Bladed has been different always, ran lesser overall gain if I recall correctly, so I'd be curious what's possible now after you get the servos tuned in properly.

Best,

Eddi

Born to fly ...
forced to work.

Ok I will try lower frequency on servos. Two questions:

1. is there a difference between how V7 and V8 work with Theta servos since even my tri-blade KSE is happy on default settings on V7?

2. Also note, my Kraken 580’s are both flying with low profile full size theta servos. Amazing flying on V8 any rpm. Would there really be a difference between how V8 works with full size Theta servos - low profile vs standard? Or you think it’s combination of servo, heli size and V8?

Ty,

Sanjeev

Hi Sanjeev,

there is a huge difference in fact, V8 is all-new when it comes to the control loop, sensor sensitivity, and filtering.
This is also why you basically can't convert a V7 setup into a V8 setup but only carry over the basic setup values.

And then, there seems to be a huge difference between full size servos (also other brands) and midi or low profile, too.
There was a customer with low profile KST recently who reported similar issues, while the full size KST seem to be an all-purpose weapon.

I think there's a difference between understanding 333 Hz (333 instructions per second) and how they are handled (servo's internal control loop, how they position, accelerate, decelerate, filter, regulate, whatever servo things they do, and also the electrical and mechanical layout (gearing)).
Tests with a flying school proved that some servos were simply not up to the task (at full steam) but behave pretty well if you manually tune them better/closer to the frequency the rotor system is working at.
Before V7 the VBar's swash plate servo frequency defaulted to 144 Hz for a reason but with V7 and now V8 on VBar EVO, the revised control loop can actually benefit from higher frequencies, ... if the servos and the overall package can deliver

At best, it would only be a software thing, which could be fixed by an update from the servo manufacturer.

I mean, with the full size, they have proven that they can

—Eddi

Born to fly ...
forced to work.

I understand. In my case low profile is ok but standard is a problem and only in V8. Thats what has me confused.

Hm, weird.

I'm curios how it turns out.

I mean, both have their right to exist, the proper tool for the respective application, where there is also model size and weight and inertia as well as the rotor head, geometry, dampening, even the blades ... fortunately, the VBar can be set up in very different ways, and pretty easily, and still pretty broadband, the sweet spot is still rather a sweet barn door, size-wise

—Eddi

Born to fly ...
forced to work.

Yes, will test in next two days - i dont have any useful internet at flying site so have to come back home and make the switch to V8.

Take your time, I'm not going anywhere soon

Born to fly ...
forced to work.

At the field and I managed to update my Sab IL Pro Miami to V8. 722 blades, 25T upgraded tail pulley. YGE ESC, full size standard Theta servos. This heli is flying great on V7 with just defaults, i just tested. After switch to V8, even at 166 Hz on cyclic, there is a tendency for the tail to bob… its a bit less but its still there. Its like V8 simply does not like my set up while V7 is happy with it. It looks like I have to stay on V7 with my set up until the issue is resolved. I am not technical enough to have a discussion with servo manufacturer. Somebody might say - all our servos work on V7 (low profile and regular), low profile works great on V8, regular does not, and what do you want us to fix?

Also wanted to add that I tried playing with cyclic gain - to eliminate the issue at 166 hz. Gain has to too high and not much fun to fly.

I am pretty sure your Direct value is too high. Set it to the same value you had on V7 in the Optimizer Parameter. Keep at 166 Servo Rate for now. Keep Control Response at 50 for these tests.

so long ... Uli
http://www.vstabi.de



1 mal bearbeitet. Zuletzt am 07.07.2025 21:56 von ulrich.

I tried 40 this time, was not enough. I had 3 banks set up earlier today to test once - on 722 blades, stick direct 40, 60, 70. Earlier than this (on other days), i had dropped stick direct all the way to 20. I mean, I can probably figure out a combination of really low stick direct, very high cyclic gain, add a bunch of stop support etc to mostly mask the issue. But whats the point? Its not enjoyable to fly it, I really tried what I could today. Knowing that my heli’s fly amazing on Vbar V7, ikon, Spirit, etc - a core fix is needed for this fbl - servo interaction. None of my other heli’s including both of my Kraken 580’s on full size but low profile Theta servos needed anything to fly well on V8. What I am doing with my other heli’s is polishing, a little here or there but they fly great on defaults. On these 2, i am working to get them fly acceptably. Thats a big stretch.

Hmm, strange. If you do like i wrote above, i cannot see a explanation why it works on V7 and not on V8. If i understand its bound to the specific servo type? Any Chance to change the servos to another type?
On the other hand, if V7 works perfectly on these, why not stay with it. We support both versions.

so long ... Uli
http://www.vstabi.de

Yes i am planning to stay on V7. At least right now, not worth spending a thousand dollars to replace servos with those that work with V8.

Hi again,

even if it's not directly related, I want to share a story from a Swiss customer: he was complaining about some similar issues, on an F3C machine. Tried the same, with similar underwhelming results. Since—what I assume—he's sponsored by GDW, he got another two sets of servos of the same type, and the third worked with default settings. Story goes, there could be (software, me thinks) differences with one batch of those.

I'll contact him again to see if there's more information, or if we can get our hands on those—if it makes sense—to investigate.

Kind regards

Eddi

Born to fly ...
forced to work.

Ok thank you. I have an order for servo spares I put on hold with helidirect because I am not sure what to get for spare servos. From your testing, are there some standard full size 8V that absolutely work with default settings on V8 on 700 size? Its a shame about Theta, they seem so good.

Hi again,

I'm still on Savox and Futaba, from another age, so I can not give proper (current) advice, first hand.

But when looking at our team pilots, particularly Marik and Alex Wiehenstroth, they seem to be happy as clams, with KST (full size, and not sure if 8 V and/or already 12 V).

I had had a chat with Uli, earlier, and he kind of confirmed that some servos, and particularly midi or low profile, seem to struggle with the amount of instructions and acceleration requests V8 allows. But that's V8 for you, now the weak link or bottleneck is somewhere else.

On the other hand, even if it's an extensively revised control loop, the parameter Control Response is probably one to give another look.
If you want (or need) similar to V7 you'd set it to as low as 30-35, and see a huge improvement (with the bobbing) but also loose much of the control/authority you could have on top, with V8.

Best,

Eddi

Born to fly ...
forced to work.

Ok thank you. I will ask on facebook. That may invite a lot of interesting responses but i have already paid helidirect and might as well get something future proof.

I have tested full size Theta Kenny Ko edition servos (12V version) on a Henseleit TDF and they work perfectly with V8 with zero issues and have set the refresh rate to 333Hz on the cyclic servos.

It might be more heli specific than a servo issue. Have had a few SAB iL Goblin customers that have had similar issues in the US, but no complaints from other makes of helicopters. Maybe try hard mounting the Evo instead of the rubber damped mount.

Cheers

VControl, VBar on all.
TDR, TDR2, TDF, TDS and TDSF
Peter

Hi TY! Yes hard mounted. I also installed the D15 pivot head on one of them, replaced brand new tail parts in the other, and upgraded tail pulley on both to see if that would help. Servo seems to be the driver. Not just the servo brand but also the model. My flying buddy also has ILGoblin Miami but on Torq HLX and seems to be ok. My low profile full size Thetas are amazing at 333 on 580 size Sab. I have heard of 3 positive experiences with Kenny Ko 12V, and one experience not positive. I see other examples of even 400 and 500 size Goosky’s with issues, and these are other brands and models of servos.

Also perhaps, target head speed and pilot tolerance play a big role. Some pilots fly 2100 and above on big heli’s and for them the bobbing at 1700 - 1900 may be a minor thing since they don’t spend much time at 1900.

For my spare servos from helidirect, I ended up ordering Torq HLX full size since my flying buddy has no problem with them on exactly the same heli model ILGoblin Pro Miami, it was confirmed. He has kept his Goosky RS7 on V7 for now.

And for now, I am really enjoying flying both my 700’s on V7 Pro / Rescue with my Evo+ radio. I love the Mikado system and it has already made me a better pilot in a month. The remaining 4 Sabs are on V8 having a great time.

The flying school was mine and I'm producing right now a setup guide for the V8. it will also come out in English, not only German.

The higher the headspeed, the better 333hz is working and yes, some servos working better with 333hz, than others.

But even the "weapon" KST X20-2208 is working much better with 166 hz, than 333hz. After my meeting with Uli 15. june I optimized over 30 helicopters of clients and five or six had the KST X20-2208. Doesn't matter the helicopter, 166 hz was always working the best.

To be honest, the best servos where not KST X20-2208, it were the veeeery expensive MKS X8. And they also performed best with 166 hz.

Of over 30 helicopters since then only two helicopter were working the best with 333hz. It was an old Henseleit TDF with old Graupner HV servos and a Goblin RAW 700 with old Hitec HV.

But the head if the TDF is veeeery soft snd the gain with 1600 rpm was 200 and with 1900 it was 18x.

So the reason 333hz was working the best was in my opinion not because of Graupner HV servos, it was in my opinion because of the soft mechanic and head.

But it could also be the servos, what would be weird, because both Hitec and Graupner HV are quite "old".

Don't worry, KST, GDW, MKS and others had all better performance with 166 hz, than the Hitec HV in the Goblin RAW with 333hz.


Please have all a little bit patience. I'm already working at the setup guide video, but it's really a huge project that can't be finished in a few days. especially because I'm also producing it in English additional.

But it will come out this month, promised

The method is not only working with low rpm, also with high rpm. I let it slso test by several pro pilots and Alex Wienstroh was really pleased by the performance of my helicopter and also pilots like Carl Henning Siebert.

Carl flying my Specter

Have a nice day,
Daniel from Helischule Gonzalez

Ty, looking forward to it!

If you can, try Theta low profile full size on a 580 Sab or similar. It have it set to 333, although I have not tested 166. What I can tell you is that it is simply incredible on V8 at stock settings. My flying buddy and I have many heli’s. It is absolutely the best performing heli on V8, even better than the 700’s!

At the same time, reason I switched to Mikado a month ago was the superior performance and simplicity of the overall system. If pilots really need to carefully set up V8 based on a detailed training video because of some servos, perhaps there is a change that needs to be made?

I always wondered why Ikon / Brain asks about models for heli, servo, blades etc. i am assuming they set defaults based on that. To get a heli flying well, you simply follow the wizard., and that works well for all my heli’s and servos. Then you might tune the PID’s further.

Hi,

thank you Daniel for your insights.

Unnecessary note: why again was VBar running at 144 Hz for, like, ever, and we had the mantra that it's simply mathematics and physics, that higher refresh rates won't necessarily bring a significant gain

Now, for some or many (particularly aggressive, high rpm) applications, in the meantime, it does, but if you want it most precise, and if you fly more conservative heat speeds, not necessarily low rpm though (is what I gathered from one of Daniels already existing videos and comments), less can be more.

Cheers

Eddi

Born to fly ...
forced to work.

Hi,

to sum up some things mentioned above:
Helis, RPM´s, dampening systems of the rotor head, servos, blades and framerates are different on mostly every heli.
Even a heli and servos change after the first 20 flights but also after 100´s of flights (dampers wear out, Potis of the servos get worse, a crash happens and so on).

@sanjeev joshi once you do the next test @V7 and V8 firmware, please be so kind and take a video of your behavior and send a link to that video here (youtube for example). Are you attending this year´s IRCHA?

About servos and frequencies: 166/200Hz do not solve all problems at all, this lower framerates can make a difference in some use-cases. A lot of 3D Pilots for example pilots competing in Master class set up their helis different than sports pilots and use very different values when comparing the setups (framerates always high (333Hz), control response high (65-90), higher direct controls)).

I set up about 50 helis on V8 so far including all our beta V8 pilots, Team "Thailand TOM Motor", Tareq, Pilots from the US and so on.
All Pilots use framerates of 250Hz or higher (swash plate) for the best result of their flying (sports/ F3C flight styles all included). These are different helis all over the bench like SAB, XL-Power, Goosky, OMP, Mikado and others, so literally every manufacturer producing helis these days...
For tail, all Pilots use 500-1000Hz (regarding to the servo specs).
These Pilots were running KST, MKS, GDW, Thetha, Savox servos, so as well many different ones.

@ sanjeev joshi As you see there is no *golden rule* for settings and setups but I am sure we can figure out your problem after we saw the video.
Please also "talk" to us during the video to get the best understanding.
Please attach a picture of your heli as well (are you using the dampers for the flybarless mount on your iLGoblins?, please send a picture as well)
Which ESC are you using? Are you using VBar Govenor? Did you plug in the RPM signal cable from your ESC to the "RPM" Port of the VBar?

Waiting for your reply

Hello, I am not sure about IRCHA, will look it up.

I already have a video, its not easy to see on video taken by the phone, but it is very obvious to all the observers there - I had two observers / pilots with me for the initial flights. I will talk with my friends and see if we can come up with an approach using some very high resolution video camera. Otherwise I will post what I have.

vbar is mounted on both 700's with the double sided tape, I have not used the soft mount because that can cause issues some times. Simple install, wires to the back. I even loosened up the wires once just to make sure the wires were not causing an issue.

Hobbywing and YGE ESC's in the two 700's. Both using the vbar telemetry cable into the little port on the side.

I use hot glue on all my installs - from the wire / telemetry connections on ESC to all connections including telemetry connection on VBar. Nothing is coming loose for sure.

Just flipping to V7 fixes the issues for both heli's. I adjust a few preferences but thats just fine tuning.

One thing that has been on my mind is that since I am new to heli's, my heli's are very new. Lets say 15 to 20 flights max on both 700's. I am using stock 90 O rings and B type delrin dampers on the head.

In my case, my elevator bobble on hard stops on my Il Goblin Pro was fixed by changing from the FBL soft mount to the hard mount option

I will move one of my 700's to V8 again to produce a video for Alex. I have shared pictures of my heli set up via facebook with him.


I am currently using agility 140, style 70, and rest are v7 defaults. What settings do you want me to use in V8 to match the V7 settings? My hope is that if I am using equivalent settings, heli should be fly similarly, not worse in V8.

Ty,

Sanjeev

Hello, just of curiosity, I connected a Theta C1 (standard profile) and Theta DH1 (low profile) to the programming card to see what default settings were. Many critical parameters are the same but DH1 has a dead band of 16 where as C1 has 24. As you recall, DH1 is perfect on 580 size on V8. C1 has issues on V8 on 700 size. So my question is this.. given the up/down bob behavior, should I try to change the C1 setting? I cant imagine why a low profile would have a lower band than a standard profile... recommendations?

SOLVED!! Here is the link to the short video on youtube. IlPro Miami, 722 blades, 25T tail, absolutely stock settings on V8 running at 1700. Previously this would bob up and down very clearly. Now you can see in this video, it is locked in! Sure, I might be able to fine tune further but the basic heli set up is flying amazing on V8.

While I have not heard back from Theta, I inspected the factory settings on my Theta servos. The low profile full size DH1 which I use on kraken 580 fly amazing on v8, and these have the following settings from the factory:

P 53
D 26
Dead band 16

flies amazing.

I then inspected two sets of C1, full size standard profile. One was from a few months ago. That had:

P 53
D 26
Deadband 26

A slightly more recent set has:

P 53
D 53
Deadband 16

Without knowing anything about the firmware changes, I guessed that this was an issue of incorrect settings from the factory. I also saw a post on Mikado face book where somebody else was complaining about two mini servos coming with different settings. So it was possible.

I then changed C1's to match my DH1's:

P 53
D 26
Deadband 16

With these simple changes, heli flies amazing on V8! I am very happy this is solved, and I thank the Mikado team for continuing to push me to look at the servos.

Along the way, I have spent money replacing brand new parts on new heli's because many times it is a mechanical issue. I have spent 20+ flights trying to get things to work.

Finally feels good to have a fix.

It seems the Pros have worked with setting changes to make it fly ok, but that has been masking the core issue. Its much better to fly with stock settings rather than keep increasing head gain, keep increasing stop support, keep lowering stick direct etc.

This also explains why even with Kenny Ko 12V, some pilots say flies with stock great, and others say it takes work to tune out the bobble.

I wish more was done by servo manufacturers to catch such issues in a year's worth of testing. There are many pilots struggling with Theta, I am going to post on Theta, Sab, and Vcontrol facebook so people know what to do.

Many thanks again to the Mikado team for the assistance here.

https://youtube.com/shorts/XDbsk0_cm_k?feature=share

Wow, never expected this. Many thanks for your consequency to track down this. Its a very valuable piece of Information for other customers as well!

so long ... Uli
http://www.vstabi.de