New Products Flash Sale
Thread Tools
Old May 19, 2015, 09:17 AM
airboss/oc is offline
Find More Posts by airboss/oc
California Style
airboss/oc's Avatar
United States, CA, El Mirage
Joined May 2007
1,519 Posts
JPF , I got the X6 servos for swash and HBL880 for tail
airboss/oc is offline Find More Posts by airboss/oc
Reply With Quote
Sign up now
to remove ads between posts
Old May 19, 2015, 12:46 PM
A VIKING is offline
Find More Posts by A VIKING
Registered User
A VIKING's Avatar
Joined Mar 2012
1,508 Posts
SK7200BE Tail Gain Adjustments on 3 Bladed Tail

Been figuring out the gain adjustments on the Skookum installed in my Urukay with the help of the guys over on the HF Skookum forum.
I had adjusted the gain up to 70 at first thinking that was good enough and was also thinking of the warnings I had heard that the three bladed systems requires a much lower gain number to prevent oscillation.

In my case not so.
My tail gain ended up all the way to the top of the adjustment at 100 before I saw an actual tail wag.
This is with a tail rotor speed of 9960 RPM and stock Urukay blades.
Tail servo is Savox SB-2272MG
Tail control rod is on the inner most hole on the horn of the tail servo which nets numbers of 100 for both left and right slider movement which is optimum.

So with the gain backed down to 95, I have an awesome tail, super fast, crisp and stabile in movement. Super happy with it.

I have learned that just because other FBLs I have used start to wag the tail at 70, that doesn't mean they should all fall into that number vicinity...in this case 95 works perfect for a gain with my setup.
A VIKING is offline Find More Posts by A VIKING
Last edited by A VIKING; May 19, 2015 at 12:53 PM.
Reply With Quote
Old May 19, 2015, 02:03 PM
airboss/oc is offline
Find More Posts by airboss/oc
California Style
airboss/oc's Avatar
United States, CA, El Mirage
Joined May 2007
1,519 Posts
thanks for the info Viking
airboss/oc is offline Find More Posts by airboss/oc
Reply With Quote
Old May 19, 2015, 02:40 PM
A VIKING is offline
Find More Posts by A VIKING
Registered User
A VIKING's Avatar
Joined Mar 2012
1,508 Posts
So let me tell you the beginning of this Gain story with the Urukay...and just because this happened on the Urukay doesn't mean it was or is an issue with the Urukay, it could have happened on any RC ship because it was generated by hearing reports and heeding them and not completely understanding my FBL.

When I first built the Urukay it was completely new to me, I knew nothing of it's tendencies because of the 3 bladed system.
I had heard many times to start very low with gain numbers...so you wouldn't find yourself in a catastrophic oscillation.
These are pretty intimidating words to hear when you just dropped a load of cash on a new ship and really didn't want to see it disintegrate in it's first few flights.

So I started way low in both tail and cyclic gain at around 40.
Yup, it's a real loose ship at a gain of 40 with the Skookum so I carefully up the gain numbers to tighten it up, always hearing in the back of my head, too high a gain will destroy the three bladed ship.

I increased the gain to 70 which from what I have heard was way to much, but it flew pretty well except it had what appeared to be a little wag in flipping maneuvers and I would lose the tail flying backward.
I thought, well there you go that's as high as you should push it because its starting to wag the tail a touch.
So from there I continued to fly it. I was disappointed in myself because I had this beautiful ship that I flew like crap. I flew my 770 way better than the Urukay.
I thought that it's a new ship and I needed to get used to it.
Time past and I sucked with it all the while thinking how much better the 2 bladed 770 flew.
In a word it felt loose.
Didn't want to increase the gain...because it might explode!
Finally I said to hell with it and started bumping up the tail gain numbers.
It wasn't until I ventured into 80 plus in gain that the ship really came alive and the wag I saw in flips went away. Now I sit at a very happy 95 in gain with the SK720BE.
You know what...it flies better than the 770.

Only brining this up so others may not fall into that trap.
Keep in mind this is with my setup and your outcome may be completely different with your setup.
I just got to the point and said screw it, let it blow up, I'm not flying it like this any longer...and boy am I glad I took it farther in gain. The ship looks like its on a razors edge and not wallowing around on top of a bowling ball.

If you don't like what you see...experiment, it's better than remaining mediocre with your flight.
A VIKING is offline Find More Posts by A VIKING
Last edited by A VIKING; May 19, 2015 at 02:50 PM.
Reply With Quote
Old Yesterday, 04:13 PM
Luvmyhelis is online now
Find More Posts by Luvmyhelis
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,429 Posts
The bigger they are, the heavier they are, the more gain values they need. Also, the Savox tail servo is so so in the hierarchy of big powerful and fast tail servos. Not to dish them, but I have flown with these and no longer do. Still have friends flying them. The MKS/Outrage versions take much lower gain values side by side.
My big 800 Triabolo feels like an albatross compared to my 700 or even 800 two bladed Gobby. But big and graceful more describes it compared to fast and nimble like the rest of mine. My gain values on my Gob 800 are higher than all the rest of my Gob fleet. Also, on my Triabolo, my control rates are maxed to boot. With values 1/3 lower on my 700s, they are scary twitchy fast. Just today, I am ordering repair parts for my Tri, as it shattered the aluminum main gear hub about four weeks ago in flight, and am seriously playing with the thought of down grading the size into a 700 class to get it more nimble.

The difference between Sab here and MC is in the details and strength of their drive trains however. Where Sab rules. On my Triabolo 800, they limit my pitch to just over 10/10, which severely effects how nimble it handles. On their 700, you can ramp it up to normal. All due to fears of drive train weaknesses or limits under loads. Had Sab come out earlier with their tri systems. All as a result of our conversations over at HF about this. I would have one today instead.

My max tail gains are still just around 65 before getting dicey.
Luvmyhelis is online now Find More Posts by Luvmyhelis
Reply With Quote
Old Today, 06:35 AM
A VIKING is offline
Find More Posts by A VIKING
Registered User
A VIKING's Avatar
Joined Mar 2012
1,508 Posts
Interesting insight LMH, thanks for posting.
Bigger ships = Bigger gain...makes sense.
I have to like my Savox servos.
I had a Savox tail servo fail on my Warp 360 which was the catalyst for me buying my first Goblin 770...way to go Savox!
Went again with Savox again as the servos of choice on the big Goblin because of their torque output for the money.
Closing in on 800 flights with Savox in the Goblins with not a whimper.
I do keep a close eye and ear on them along with taking temperature readings after every flight, which I would do with any servo manufacturer.

As far as the so-so performance of Savox...you haven't seen me fly.
I'm not even at the so-so level of 3D performance yet so the servos abilities outpace my ability to out perform them.

I have big plans this Memorial Day week end to increase that skill level, maybe all the way up to so-so...I can dream can't I?
A VIKING is offline Find More Posts by A VIKING
Reply With Quote
Old Today, 09:27 AM
IntegrityHndywrk is online now
Find More Posts by IntegrityHndywrk
IHW Heli Division
IntegrityHndywrk's Avatar
United States, FL, Palm Coast
Joined Mar 2012
8,021 Posts
Quote:
Originally Posted by A VIKING View Post
Interesting insight LMH, thanks for posting.
Bigger ships = Bigger gain...makes sense.
I have to like my Savox servos.
I had a Savox tail servo fail on my Warp 360 which was the catalyst for me buying my first Goblin 770...way to go Savox!
Went again with Savox again as the servos of choice on the big Goblin because of their torque output for the money.
Closing in on 800 flights with Savox in the Goblins with not a whimper.
I do keep a close eye and ear on them along with taking temperature readings after every flight, which I would do with any servo manufacturer.

As far as the so-so performance of Savox...you haven't seen me fly.
I'm not even at the so-so level of 3D performance yet so the servos abilities outpace my ability to out perform them.

I have big plans this Memorial Day week end to increase that skill level, maybe all the way up to so-so...I can dream can't I?
About the only time I crash anymore is when my servos fail. I beat the crap out of them these days so I'm lucky if I get 300 flights out of a $100 servo. So because the coreless motors keep failing. I decided to bite the bullet last night and get some of the newer Brushless high torque BK cyclic servos.

They list at $145 each, but I got a deal on them for buying 3. I got 3 of them for $390 shipped, which is something like $130 each with shipping included. Then I wake up this morning and noticed a new deal for 10% off... I should have waited dammit.. For being so expensive, I really hope that these brushless motors last a lot longer and don't run hot. Or at least I hope the brushless motors have magnets rated high enough to take the heat combined with Florida's existing, nearly 100F OAT. I guess time will tell..

When i bought the servos I had the choice of high speed or high torque brushless servos. I imagine the gearing is different or something, not sure. But the high torque ones nearly doubled my torque, but I loose 0.03 on speed. Not so shabby. However the high speed servos retained the same speed as the cyclic servos I'm using right now. But it only added about 80-100 oz-in of torque. I was a little tossed up between the two. But then i decided that the higher torque would probably be more beneficial with my heavier X7 helicopter than more speed... Both seem to be an upgrade, really. What do you guys think?
IntegrityHndywrk is online now Find More Posts by IntegrityHndywrk
Reply With Quote
Old Today, 06:16 PM
airboss/oc is offline
Find More Posts by airboss/oc
California Style
airboss/oc's Avatar
United States, CA, El Mirage
Joined May 2007
1,519 Posts
the best servo I ever used is the MKS , they have superior holding power and 0 slop ! have tried every servo and thought most were ok till the MKS were first installed in my hotliners ,jets and helis. there is no comparison but you will pay for the quality.
airboss/oc is offline Find More Posts by airboss/oc
Reply With Quote
Old Today, 08:48 PM
Luvmyhelis is online now
Find More Posts by Luvmyhelis
Professional heli wrecker
Luvmyhelis's Avatar
United States, WA, Spokane
Joined Oct 2010
4,429 Posts
Quote:
Originally Posted by airboss/oc View Post
the best servo I ever used is the MKS , they have superior holding power and 0 slop ! have tried every servo and thought most were ok till the MKS were first installed in my hotliners ,jets and helis. there is no comparison but you will pay for the quality.
Yeah, I am def a total MKS freak. I also had the rare opportunity to get to chat repeatedly with Thomas, who owns the USA MKS. From what I understand, I had the very first Mks servo in the U.S. way back when, when I was modding 450s. The thing simply ripped. But, I also believe in trying other brands and comparing. Nothing did, but, out of all the pilots I do know. Just how many need that responsive of a servo? I admit they totally blew me away earlier. Now I am just spoiled. But run three separate brands of servos now, oops. make that five.

Martin, as I said, one of the guys I fly with is also running Savox on all his big birds. The only time he has had issues, was when we tried to fly one winter close to zero outside. And either his BX freaked out, or his servos locked up from the cold? It was an uuooogly crash and even uuuglier day. But he is a gentle 3d sport guy. Silky smooth. My own early release HK mag induction style servos also gave me grief that day that I was field testing. I will never, never, ever, never fly in that kind of cold, ever again... Did I say never?

Integrity, ouch, that is some serious money. Soo glad I am not building much anymore. If I had unlimited $$$ laying around to burn, I still would love to handle a set of the MKS X8s. OMG. Brutal. (not that I would or could use their performance). Just give an old show car builder like me anything anodized or polished. Aluminum? I need a cold shower.......
But from what I hear, the BK servos should do a great job! Congrats

The way I have come to look at it is this. Any guy that builds and flies helis. That is pretty cool.
Luvmyhelis is online now Find More Posts by Luvmyhelis
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Article SAB Heli Division - Goblin 700 Review CSpaced Large Electric Helis 51 Nov 19, 2013 10:23 PM
Sold Brand New & unfinished GOBLIN GOBLIN 500 RED x5heli Aircraft - Electric - Helis (FS/W) 3 Apr 30, 2013 11:37 PM
Video INSANE RC Heli- The Goblin 700! RobscoRC Electric Heli Talk 1 Apr 15, 2013 12:05 PM
For Sale ProHeli Blade MCPX / MCPX BL Goblin Canopy Fuselage mGoblinX Goblin Style Howeroll Aircraft - Electric - Helis (FS/W) 8 Apr 07, 2013 06:11 PM
For Sale ProHeli Blade MCPX / MCPX BL Goblin Canopy Fuselage mGoblinX Goblin Style Howeroll Aircraft - Electric - Helis (FS/W) 1 Apr 01, 2013 01:18 PM