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View Full Version : tail kick at spool up.......help need advice


finfan882002
03-02-2009, 11:02 PM
ive tried everything.... i have a trex 450 and gy401 with 9650 tail servo.....the belt is tight... im at soft start on my cc35 and im gettin a bad tail kick counterclockwise at spool up.... any advice?

Slyster
03-02-2009, 11:04 PM
Do you mean is suddenly start spinning around like crazy? Switch the reverse switch with a screw driver on the actual servo.

Jasmine2501
03-02-2009, 11:44 PM
He posted the same thing on RCGroups... pretty sure he's talking about the 'normal' tail weirdness, when it spools up. There's a point where the tail just doesn't have enough speed to work right, but the torque on the main blades is pretty high. If it's like in my video here, it's totally normal...
1707288

finfan882002
03-03-2009, 12:08 AM
nice flyin.....i hope to do fff and circles soon.....i have more of a jerk to the right at spool up

finfan882002
03-03-2009, 12:17 AM
what soundtrack is that or ur video?

MavriC
03-03-2009, 03:35 AM
I have my 450 setup to hover in "normal" mode (gyro) perfectly, without drifting... I did this, cause a lot of Heli's if not most when starting on a grassy type of surface, the gyro and the Heli don't agree with each other. As soon as you lift off a little, you'll get a slight kick from the gyro suddenly getting control.

I flip throttle hold, while arming the ESC with the battery. This also tells the gyro that it's in "heading hold" mode. Once that's done, I flick off throttle hold, putting the gyro in "normal mode", spool up, and lift off without any kick what so ever.

Once in a hover, I flick into idle-1 then idle-2.

Mind you, I can still lift off in idle-1 or idle-2 but there is a slight kick. This isn't noticeable on a smooth surface keep in mind. Only grassy type surfaces, that can "hold" the skids slighty, hence interfering with the gyro's ability to work. But this is nothing to be truely concerned about.

I do it this way so I have the benefit of lifting off in either "heading hold" or "normal mode".

Rick.

Skarn
03-03-2009, 08:10 AM
Hey,

Do you move the heli at all after plugging in the battery? Once the gyro initializes, if you move it somewhere...like say to a different place to actually take off and fly, this will happen if the tail is not exactly where it was when the gyro initialized.

Skarn

Jasmine2501
03-03-2009, 10:20 AM
Carlos Santana and John Lee Hooker doing "The Healer" - good flying music.

I think you might be right - I moved the helicopter after initializing, so maybe the gyro was trying to find the spot where it was when I turned it on. Either way, I think you just have to deal with the tail yourself until it spools up to speed.

Arsenix2001
03-03-2009, 02:45 PM
I had the same problem with my GY401. Bad kick at lift off, sometime uncontrollable. MOST likely, no garauntees it is either vibration or EMI. I balanced the hell out of everything and added a 1/8 mild steel plate under the gyro sandwiched in foam. No more kick, dont know if it was no more vibes or the shielding that fixed it but just a few ideas.

pwoodyp
03-03-2009, 03:30 PM
dont know if it was no more vibes or the shielding that fixed it but just a few ideas.
Probably in your case it was a vibration issue as the GY401 case is pretty much shielded from EMI buy virtue of what it made out of.... shielding is built in :YeaBaby:

MavriC
03-03-2009, 04:28 PM
Once again, if you arm the gyro in "normal mode" via a throttle hold condition, you will not have this problem even if you move the Heli to a different location after connecting your ESC up to the battery.

Try it, you'll see.

Rick.

Jasmine2501
03-03-2009, 05:18 PM
The GY401 will not initialize correctly in normal mode.

MavriC
03-03-2009, 05:35 PM
The GY401 will not initialize correctly in normal mode.

Yes, we all know that.

That is NOT what I'm saying.

You ARM the ESC/gyro in "heading hold" mode with the throttle hold switch in a condition to allow the gyro to be in "heading hold". Once that is done, when you flick off the throttle hold switch, it puts the gyro in "normal mode".

Going into idle-1 and/or idle-2 puts it back into "heading hold" but in idle-0 or normal flight mode, the gyro is in "normal mode" not "heading hold".

As long as the 401 is ARMED in "heading hold" you can come in and out of "headind hold" "normal mode" at will.

Steps for lift off in "normal mode"
1 - Turn on TX.
2 - Flick throttle hold.
3 - Connect batt to arm ESC and initilize gyro in "heading hold".
4 - Don't move heli until things have armed properly.
5 - Move heli to where ever you want to lift off from.
6 - Flick off throttle hold (puts 401 in "normal mode".
7 - Lift off, and you will NOT get any tail kick.
8 - Go into idle-1 or idle-2 as you wish (putting 401 in "heading hold".

Steps for lift off in "heading hold"
1 - Turn on TX.
2 - Flick throttle hold.
3 - Connect batt to arm ESC and initilize gyro in "heading hold".
4 - Don't move heli until things have armed properly.
5 - Move heli to where ever you want to lift off from.
6 - Flick up to idle-1 (heli stays in "heading hold".
7 - Move collective to mid stick or zero pitch.
8 - Flick off throttle hold allowing heli to spool up.
9 - Lift off, and you "might" get a tail kick via skids holding firmly onto grassy surface (will not happen on a smooth surface).

In either case... you have the choice of lifting off in "heading hold" OR "normal mode".

I've been flying for 4 years like this, with several heli's right up to a 600CF with a 611 gyro. Not a problem with tail kick on any of them.

Follow my steps, and you will not have a problem.

Hope that helps.

Rick.

Jasmine2501
03-03-2009, 05:44 PM
Seems like a lot to go through for a problem that isn't even a problem?

MavriC
03-03-2009, 05:47 PM
Seems like a lot to go through for a problem that isn't even a problem?

If it wasn't a problem as you state, then why did the poor guy post it in here asking for advice/opinions?

Alot of steps? Count the steps/procedures the next time you go to fly... it's perfectly normal that many steps to get your heli into the air.

He was asking about a tail kick. I told him what was causing it, and wrote the fix for HIS situation.

Simple really.

Jasmine2501
03-03-2009, 10:16 PM
I don't consider it a problem and I've seen a lot of helicopters do it, but like you say it probably is because I moved it - but it could indicate a deeper issue with the gyro settings or something, so it's definitely a good question.

MavriC
03-03-2009, 11:00 PM
I don't consider it a problem and I've seen a lot of helicopters do it, but like you say it probably is because I moved it - but it could indicate a deeper issue with the gyro settings or something, so it's definitely a good question.

It's not a "problem" per say... more of a "what was that" or "why did/does it do that"...

Kinda like "why does my car pull to one side when driving down the road" sorta thing.... it's done on purpose that way, for safety sake. In case one falls asleep at the wheel, the vechical will drift to the ditch, not uncoming traffic. But, the driver will still ask... why and will want to know the answer to this. Sure it can be corrected upon request, but most don't.

Anyway...

Next time you move your Heli, the tail will move and hold it's last postion. During spool up, the ground holds the heli, and once it gets light on it's feet, there is a sudden jump, then the gyro kicks in and catches it. However, lifting off on smooth surfaces, this is a less occurance. The heli slides slightly and the gyro reacts instantly... you'll only see a slight tail drift from rotor torque, not the "snap" as in lifting off in grass.

Lifting off in "normal mode" this does not happen, cause the tail is centered, even after moving the heli to your desired position. Keep in mind that you have to have a heli set up to hover in "normal mode" with the tail linkages set up properly to allow this. Seting up this way, allows for a rock solid hover in "normal mode" because the tail is setup mechanically. I personally prefer this tail setup as it's "mechanically" proper.

Some just set the tail hub to center with the 401 and leave the tail holding up to the gyro. I don't. I setup the tail so that in a "normal mode" hover, it's drift free, from a mechanical non-drift setup. I then teach or get the gyro to learn it's new "home" position, and when I flip in "heading hold" via idle-1 and idle-2 there is no tail movement difference... but now I'm in "heading hold".

It's nice to be able to have the option(s) at spoolup based on the surface I'm on.

Rick.

Jasmine2501
03-04-2009, 12:18 AM
Yeah that's what I do. I never run it in normal mode, only used that for set up. I only fly in idle-up mode so I suppose I just deal with it. I use the normal mode only to spool it up and I flip it to idle-up mode as soon as it's up to speed.

Skarn
03-04-2009, 08:44 AM
Mavric,

I believe you can accomplish the same thing by simply flipping the rudder stick back and forth three times....it "resets" the gyro.

Skarn

MavriC
03-04-2009, 12:01 PM
Mavric,

I believe you can accomplish the same thing by simply flipping the rudder stick back and forth three times....it "resets" the gyro.

Skarn

Yes, it does re-center the tail blades, but won't stop a slight kick in a grassy situation.

Rick.

mmarian
03-05-2009, 02:16 PM
I am not shure if we are talking about the same thing here but I have Jazz ESC and I believe that the kick has got something to do with governor mode. When the HS reaches the set value by TC settings in you Tx, the ESC makes a few quick and rapid adjustments, getting the desired HS in governor mode. The motor stops accelerating suddenly and the torque it generates during acceleration changes suddenly as well. As we know gyro tries to compensate against these forces and this sudden torgue change causes the tail to kick before the motor finaly settles in the pre-set HS. That is my lame explantion but it makes sense to me. Once in take off, all is fine and tail is steady.