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HelicopterFlybarless Rotor Head SystemsV-Bar › Whipping Tail, even after much troubleshooting
12-17-2013 09:51 PM  3 years agoPost 1
Sam2b

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Seattle, WA

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If you would, please, read my original thread you will see all of my details. I'm suffering chronic tail whipping, up to 180 degrees.

Original thread: http://www.vstabi.info/forum/read.php?26,107841

Thanks.

_Sam B_
Team MSH USA * Protos Max * Xpert servos * Cyclone Blades * ProgressiveRC * VoltMagic * Ecalc

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12-17-2013 10:08 PM  3 years agoPost 2
AWittleWabbit

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O.C., CA

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Hey Sam,

I don't know anything about the 700, but have you thought of moving the ball out another hole? If I read right, your travel is 120 both ways in the vbar, right? That coupled with relatively high P and I values makes me think there is not enough mechanical gain.

Just a thought, I'm curious as to the problem as well. After V bar, almost everything else whips to me. I hope you get it solved.

Heli-itis sufferer.

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12-18-2013 01:08 AM  3 years agoPost 3
LaDon

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Fort Dodge .Ia

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Ok first thing I would do is go to 115 tail blades. If we run 105s on ours it won't hold squat. Your p gain and I gain seem pretty high. Also do you turn off the optimizer after a couple of flights? If not that will mess with you too. Also what tail servo are you using?

Team Jr

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12-18-2013 01:50 AM  3 years agoPost 4
Sam2b

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Seattle, WA

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Thanks. Yes, I turn off the optimizers (tail and cyclic) after 1 flight of tuning it.

True the P & I is high, but in an effort to help the matter with 105mm blades. I can reset to defaults when I try 115mm blades again soon.

My instincts also tell me to just use 115mm and call it good. I admit the issue happens less with 115mm in the past, but I am trying to get away with 105mm after watching Jamie Robertson's flights. He doesn't reply to my PM's, so I assume he's running a box stock kit including 105mm tail blades, and maybe a 22T torque tube gear (or even 21TT for faster RPM). However, it may be apples-to-oranges completely if Jamie does not use Vbar (and silverline).

Regarding the 120 limits, I've already tried a longer (rigid) servo horn to allow the limit to be ~100,100, but the problem still persists. So maybe that's not a major contributor (just a guess based on trial and error so far). Note: when I say "limit", I mean the maximum value in the Vbar until the slider hits the hub on the workbench with left-rudder input.

Revisit the vstabi link above and see the video clip at 0:33 to see the maneuver I do that makes my tail whip.

_Sam B_
Team MSH USA * Protos Max * Xpert servos * Cyclone Blades * ProgressiveRC * VoltMagic * Ecalc

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12-18-2013 03:09 AM  3 years agoPost 5
LaDon

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Fort Dodge .Ia

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Jamie is flying the vbar also on his competition helis I believe. You didn't say what you had for a tail servo. Also Mikado has a very good tail belt but you do have it good and tight so it cant slip. I didn't hear it in the video so I am betting that is not it. Did you set the vbar in rate mode and set the tail linkage so the servo don't center and then have to go to holding the tail? Just a thought. I am not sure what it really is. If it was me I would be trying everything starting from making sure it is smooth as silk to changing the servo and going to the 115 blades. It is a neat looking flight tho.

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12-18-2013 03:39 AM  3 years agoPost 6
Sam2b

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Seattle, WA

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Thanks again for the input. I'm looking for anything anyone has to say, so this is great. I did write in the specs list a BLS251 tail servo. I have also tried the auto-trim hover which also does center the tail slider for the right amount of right thrust similar as the method used in the past with rate mode (as per Ulrich). But even then, the issue persists. (Damn powerful electrics!)

I will install 115mm tail blades, do an auto-trim hover, then an optimizer flight, turn off optimizer, then fly again. I'll report back, and even with video. I should have taken a video of my exact issue.

I'm open to more thoughts, so keep'em coming.

_Sam B_
Team MSH USA * Protos Max * Xpert servos * Cyclone Blades * ProgressiveRC * VoltMagic * Ecalc

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12-18-2013 12:12 PM  3 years agoPost 7
LaDon

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Fort Dodge .Ia

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I don't think the auto trim flight sets the tail. You need to do that in rate mode and then set it mechanically and then put it back in heading hold

Team Jr

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12-18-2013 03:16 PM  3 years agoPost 8
Clarence Creer

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Dallas, Texas

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Sam2b

Let me help you out. I pm'd you.

Team Kontronik Team minicopter/PeakAircraft
VTeam EvoPowerBattery

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12-18-2013 04:15 PM  3 years agoPost 9
Clarence Creer

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Dallas, Texas

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edit. Wrong model.

Team Kontronik Team minicopter/PeakAircraft
VTeam EvoPowerBattery

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12-18-2013 05:12 PM  3 years agoPost 10
knightofcarnage

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chicago

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If you would, please, read my original thread you will see all of my details. I'm suffering chronic tail whipping, up to 180 degrees.
did you watch MrMel video how what cause this exact issue he describes.

Here the steps i take to tune that tail.
1) Do you know how to enter trim mode? Lots of ppl i know that use the vbar they have NOIDEA how to start auto trim.

2) first make sure you are in 80 to 110 on the trim setup menu for both directions.
3) I use the auto trim to figure my mechanical neutral point. want you need to do is hover they guy around with holding the sticks. I usually do it in a garage so there is no wind. Next you take a look which direction the auto trim add the trim. Then i counter the auto trim by mechanical shorting or lengthening the tail pushrod. Reset auto trim and do it again. you will get to a point where the auto trim is not adding much trim. (You and start with 4 deg offset). If you get to this point you tail will be almost right. Only thing that might cause you issues if you I gain/Pgain and Tcomp.
4) If you can use the governor feature from vbar. It works really well on electrics , kinda tricky on nitros but sill works fine.
4) this also works for main rotor but you end loosing you swash plate level positions.

I can take my hands off my 700E DFC Pro and my 450L. No tail wag nothing.

One more thing what version software are you running. There was a bug 5.3.x where that tail would loose its hold because of an overflow issue. I had this issue myself before the patch. This was last year.

Also i like to point out there are some extra hidden features on minivbar with control panel that you can't see with software. I will not mention which ones because i don't want them to be NERFED

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12-18-2013 06:37 PM  3 years agoPost 11
LaDon

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Fort Dodge .Ia

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Did you read this? It is from vstabi website. I seen the part about the tail shaft on the logo. You may have already seen this but I thought I would thro it up here

http://www.vstabi.info/en/node/254

Team Jr

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12-18-2013 07:21 PM  3 years agoPost 12
knightofcarnage

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chicago

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Did want to add also the speed controller can cause tail issues. If I'm reading the orignal post it's an turnagy esc. I'm assuming you are running gov mode.

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12-18-2013 09:22 PM  3 years agoPost 13
Sam2b

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Seattle, WA

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Hi, knightofcarnage. Yes, I do know how to enter trim mode. Not to boast, but I'm mostly advanced with Vbar knowledge.

I spoke with Ulrich in person at IRCHA 2012 and he did say the trim flight also centers the tail, hence the 3rd trim bar for "rud". The misconception comes from autotrim documentation only talking about the main rotor (cyclic) trim. They should mention the tail, in my opinion.

I've also done as you said (for the tail): do a trim flight, take a look, make mechanical changes, reset, repeat until no tail trim was made. Then disable auto trim.

Yes, I'm using the Vbar gov as listed in my setup on the original thread. This ESC is mostly fine with the Vbar gov, and originally used by MrMel. I followed his setup instructions for this Tunigy HV120 ESC exactly. (however there is a separate un-related issue of the ESC throttle input not being linear as the vbar's throttle output, but again not related to the tail issue, I'm sure)

I am running the latest firmware & software 5.3.4.x, so I believe I do not have the overflow bug. Also, I've recently have done a totally clean setup on the Vbar software, including hitting reset on all setup screens, and overwriting all banks with the new setup.

After watching Mr Mel's tail tweaking video, that is when I increased the I gain to trying reducing the whipping. It did help a little, but I didn't want to use too high of values. He also mentioned right away to start with lowering the torque compensation and

LaDon, thank you. I have read that page on tail rotor & linkage, and I've verified I have things correct as per its check list, including the torque precomp in the correct direction.

I think that covers all of your points outlined. I'm grateful for you sharing! I'm open to any more ideas too.

_Sam B_
Team MSH USA * Protos Max * Xpert servos * Cyclone Blades * ProgressiveRC * VoltMagic * Ecalc

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12-19-2013 12:53 AM  3 years agoPost 14
LaDon

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Fort Dodge .Ia

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I guess the thing I noticed was the thing about sanding the shaft down a few thousands. I didn't know that about the tail trim thanks for pointing that out but I think it is a lot faster to do it the old way in rate mode. I can see where that way is really good for someone that isn't maybe very quick at reacting but my kid is quick with the thumbs so I do it the old way.

Team Jr

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12-19-2013 12:35 PM  3 years agoPost 15
LaDon

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Fort Dodge .Ia

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One thing I would check is that servo has nylon gears in it. One thing I ran into after Ryan stuck the tail in the ground I put new gears in it. Had to do that a couple of times and didn't get all the little tiny plastic teeth out of the servo. One got caught in the metal main gear and it had a catch in it when it went by a spot. I don't know if this could be the problem or not but it is something to check. It maybe is that it might just have a bad gear in it.

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12-19-2013 01:52 PM  3 years agoPost 16
Richardmid1

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Leeds, England

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Definitely at 1900rpm you want either 115mm tails or the 700 nitro 21T tail counter gear to bring the ratio up to 1:4.95.

If you have also upgraded a V2 tail box to the new style pitch slider mechanism you no longer get enough tail pitch against torque. I had to machine off a good 2mm from the hexagon end of the slider tube.

60% of the time, it works every time!

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12-19-2013 02:19 PM  3 years agoPost 17
Ronald Thomas

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Gainesville, Fl, USA

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Tail needs more leverage as Richard stated. You maybe running 1900 HS but if you add enough pitch that HS will drop a little and all the leverage is gone on the tail. A bigger disc or more TS/HS should solve that. If you change to either I would start over at the factory settings and adjust from there. I run 115s on my 700s and they tail is rock solid….of course I don't run 1900 either

Team MikadoUSA 480XXTreme, 550SX, 600SX, 700XXTreme, 800XXTreme!!

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12-19-2013 02:55 PM  3 years agoPost 18
knightofcarnage

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chicago

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For lower HS I use 21t from the 700n dfc it give you about 400 more rpm 4.95 gear ratio.

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12-19-2013 08:33 PM  3 years agoPost 19
Sam2b

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Seattle, WA

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All interesting info. It appears my 1900 RPM head speed (and proportional tail speed) is a large factor according to what you guys say. I specifically upgraded to the black 22T gear for this very reason thinking it would help, but amazingly not. Imagine my struggles with the prior 24T! I have a 21T new in the packaging for future experimentation, so maybe that day has come.

I'll tell ya I have almost 45 degrees right thrust already if I use a travel value of 120 in the Vbar! Are you saying that is not enough? If the servo is actuating a that full throw, I think the blade is stalling at the point. So what tail blade pitch degree is "enough"? Additionally, if the blades ever actuated 45 degrees of right thrust, the motor would strain very bad, and possibly even snap the torque tube if not first the gears, or even boom!

I do not have the latest tail case (Pro DFC), but have not upgraded to the new pitch slider. (I have have upgraded to the new solid 6mm tail shaft & bigger hub.)
If you have also upgraded a V2 tail box to the new style pitch slider mechanism you no longer get enough tail pitch against torque. I had to machine off a good 2mm from the hexagon end of the slider tube.
I was convinced this was a vbar/travel issue, but your suggestions help me consider other possibilities. It's interesting that another reputable pilot actually recommended to try using LESS throw on the pitch slider (left rudder with the torque, in addition to right rudder throw. 15mm on the servo horn, and 100,100 on the vbar). I haven't yet tried those settings, but open to try several hardware/software combinations to accommodate perfect performance at 1900RPM

I believe 1900 RPM is a reasonable RPM because with my Trex700 nitro I ran 1950 RPM (hardly much difference), flybar'd, Spartan Gyro, 105mm blades, and a tad less tail gear ratio than my current 22T MOD 1 gears. Yet it held so perfectly and never ever EVER whipped or blew out no matter how ridiculous collective & cyclic input I gave, even on a very windy day when I purposely tried to challenge the tail in this way. With that 700N's configuration, it was absolutely unwavering. The differences between that 700N's & current 700E's hardware is, increased motor torque, increased mass/weight, JR tail servo, Vbar tail gyro, Vbar gov. I would expect the same unwavering performance with the Vbar on the 700E.

That all said, I HAVE experienced the vbar yield an unwavering tail with the Vbar 4.x tail gyro (black) on my 600E and 600N. The feeling is awesome when you can throw anything and everything at the tail, and the piro rates are absolutely consistent, no whipping, and never a blow out. After having that sort of performance, anything less is not fun at all, and destroys my confidence in the heli. I like to pirouette a lot in my flights, including several traveling pirouetting maneuvers that challenge the tail a good deal.

_Sam B_
Team MSH USA * Protos Max * Xpert servos * Cyclone Blades * ProgressiveRC * VoltMagic * Ecalc

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12-20-2013 01:30 AM  3 years agoPost 20
knightofcarnage

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chicago

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I believe 1900 RPM is a reasonable RPM because with my Trex700 nitro I ran 1950 RPM
True but don't forget one thing. The electric is much heavier then a nitro. My DFC weight in at 11.5 to 12 pounds where the nitro is is around 8.5 to 9 pounds. Also i notice the sweet spot on 700E DFC for my flying style is around 2150. I do use 21T even with head-speed passed 2050 mostly because I'm to lazy to switch it back to 22T. But if you are going to run below 2050 you should switch 21T and have your gear ration 4.95. But also just as percussion i would switch to the new tail shafts. Higher tail RPM does put extra stress on the tail.

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HelicopterFlybarless Rotor Head SystemsV-Bar › Whipping Tail, even after much troubleshooting
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