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Old Nov 12, 2006, 04:12 PM
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Honeybee CP2 full separates tail trimming question with detailed setup pictures

Hi everyone,
I have a question about the tail setup for those of you who have done the brushless tail setup with a heading hold gyro. Particularly the Eflite G90 with a Castle Creations Thunderbird 9 amp ESC and Feigao long can brushless motor using the stock geared setup. I've read and searched and some people do have to hold left stick to keep the tail from turning, but I didn't find any trim setup issues and specs.

My problems is this. So I got the itch to do the full brushless mods last night and had the parts sitting for a few weeks since I ordered it from bphobbies. I installed everything and wire it up and get it flying. No problems til I try to trim it out. I'm cranking my subtrim on my Futaba 9C to -101 ( to the left )for the rudder and adjusting the right rudder trim to +24 while the gyro sensitivity gain is set on +65 heading hold on my TX. No revo mixing of course! The tx throttle hold is also set with a rudder offset to keep it from spinning left at nearly half throttle on the tail motor. My Thunderbird 9 is also programmed with a NiCad/NiMh setting so I don't the get the tail cutoff and spin out of control ( my main motor ESC signals when power dies down so no need to lose the tail ). I've tried my old settings also with the brushed separates thinking it wasn't going to be off my much, but didn't workout.


I'm not having issues with flying this heli, but was wondering if anyone else is having these types of extreme settings on their setups once doing the brushless tail mod. It has TONS of tail authority and hovers like the tail has more control over the mains. Rock sold and very stable. This is just hovering indoors BTW. I will take it out soon.

I should mention that I've run the the brushed separates tail with the stock motor wired with a resistor and a Zener diode so that it get just over 9 volts and nothing more so the motor will last longer. With this setup, I had to only set the subtrim to around 30 for the rudder and timmed the rudder to the right very little during flight. This setup held well for hovering and basic flight, but never attempted any type of 3D.

Setup:
Eflite G90 Heading Hold Gyro
Eflite Park 370 4100Kv Main motor with integy steel 8 tooth pinion (from 1/18 scale R/C cars)
Century Autorotation main gear
Eflite 20 Amp BL ESC
Berg 7 receiver
Hitec HS 56 cyclic servos
Feigao long can tail motor with stock tail setup including stock pinion modified to fit
CC Thunderbird 9 BL ESC
Thunder power 910 and 1320 batts. Cg is beter with 1320, but higher AUW
Futaba 9C Super TX


Here are some pics so you guys can see the heli is setup properly:
TONS OF WIRES!!
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Last edited by wkma7six; Nov 13, 2006 at 01:06 AM.
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Old Nov 12, 2006, 08:34 PM
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South Windsor
Joined May 2005
390 Posts
That is a beautiful setup. I love the cable routing.

The gyro should hold the tail in heading hold mode if you have about 1.52 ms PW going in to it. If you have a Castle link you can hook that up to the Berg to see what the pulse length is. I also think you have a fuction in the 9C where you can see what you are sending out on Ch 4.

The HH gyro is going to send out whatever pulse length it needs to the speed controller in order to hold the tail in place. I bet you have some other mix or similar that is causing the ch4 PWM to be off neutral.

I doubt that the zener has any benefit. There is an inherent limit in how much power you need/can feed to the tail. In average it uses something around 10W. Brushless motors don't fail from over current (within any relevant limits) The failure mode is that the magnets getting demagnetized from excessive temperature.

I did not fully understand how the resistor was connected but if it is in series you will reduce the gain in the control loop since increased current will decrease the voltage, it is effectively like a motor wounded with to thin wire. An other problem you can get is that the speed controller cuts out if you have a current surge. Put a fuse before the tail speed controller if you have concerns. (2A auto fuse will proably be a good choise)

Are you sure you are in HH mode and not in conventional gyro mode. You could disconnect the gain wire and use the pot on the G90 to verify. It almost seems like that from your post.

Ulf
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Old Nov 13, 2006, 01:03 AM
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Quote:
Originally Posted by tribologist
That is a beautiful setup. I love the cable routing.

The gyro should hold the tail in heading hold mode if you have about 1.52 ms PW going in to it. If you have a Castle link you can hook that up to the Berg to see what the pulse length is. I also think you have a fuction in the 9C where you can see what you are sending out on Ch 4.

The HH gyro is going to send out whatever pulse length it needs to the speed controller in order to hold the tail in place. I bet you have some other mix or similar that is causing the ch4 PWM to be off neutral.

I doubt that the zener has any benefit. There is an inherent limit in how much power you need/can feed to the tail. In average it uses something around 10W. Brushless motors don't fail from over current (within any relevant limits) The failure mode is that the magnets getting demagnetized from excessive temperature.
I did not fully understand how the resistor was connected but if it is in series you will reduce the gain in the control loop since increased current will decrease the voltage, it is effectively like a motor wounded with to thin wire. An other problem you can get is that the speed controller cuts out if you have a current surge. Put a fuse before the tail speed controller if you have concerns. (2A auto fuse will proably be a good choise)

Are you sure you are in HH mode and not in conventional gyro mode. You could disconnect the gain wire and use the pot on the G90 to verify. It almost seems like that from your post.


Ulf

Thanks Ulf
Oh, this setup with the zener diode and resistor was with a brushed setup. There is still a 3.5 amp fuse still hooked up that is stuck on the rear servo in one of the pics. Ignore that I guess. I was just using that as an example of what seemed to be non-extreme settings with the former brushed system versus the current brushless system. My dilemma is with the brushless setup

It is in HH mode. I've used both the adjustment pot and the transmitter GY sensitivity adjustments. I like having it on the TX so I can adjust while in flight, though I know I shouldn't in the air.
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Old Nov 13, 2006, 01:37 AM
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I got it, should have reead more carefully, I assume the zener arrangement is a simple snubber to reduce arcing?

It should be totally transparent for the system if there is a brushless or a brushed speed controller on the tail The only thing I can think of is that there is some auto calibration of the range that causes trouble for you.

Ulf
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Old Nov 13, 2006, 02:25 AM
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yes, that diode and the resistor were there to limit voltage going to the original brushed motor. You're right, it should be transparent to the settings.
I'm thinking because the output of the new BL system has more power and since I'm using the stock tail gearing, maybe I have too much tail authority and can't counter it enough by using the trim settings? Does that make sense? Maybe I'll try trimming the diameter of the tail blade a bit to reduce the amount of air being moved while the motor can run at its higher potential such as a direct drive motor with a small prop can do. But how much exactly to take off? The size of the tail prop now is the same diameter as my MX400/ Trex tail blades. I'm open to suggestions.

Update: I flew it tonight in near darkness with no wind and had a crash while the heli drifted into the darkness and trying to dial in the tail at the same time. Minor crash and is now fixed. Tried it again indoors and is now in working order again.
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Old Nov 13, 2006, 03:23 AM
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I had similar issues with a v small heli (#52) when I put a brushless tail on. Probably even more due to using a rate gyro format. I don't go by numbers or what 1.5mS is supposed to do, I go more by what the goal is. I found for instance, a non linearity in rpm curve of the esc and tail motor etc. In my case far more issues had to be addressed, like tail into tail mixing, for unequal yaw offset curves which then gave equal spin rates etc. I used rudder mixed gyro gain offsets which were unequal in left/right for further equalisation.
It's so easy to get 'natural' spin, you just shut the motor off. The other way is a little harder, you need power on top of the neutral torque level. Immediately you have a big offset. Then you need equal reaction time effects, one way you have tail assisted by torque, the other against it. More offsetting, if you can get it.
If you get the motor running at too high an rpm in a stable mode, come the time you need a lot of power, it won't be there to have. It would be interesting to see the 'firmware' mixes that are used in 4in1's. I bet they would be suprising.
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Old Nov 14, 2006, 03:25 PM
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I think I have found my answer with the prop trimming. Thanks to Macrotor and the rest of the guys in the thread that did all that testing.

Here's the link:
http://www.rcgroups.com/forums/showt...8&page=5&pp=15
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