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Old Jul 01, 2011, 11:15 PM
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Center of Gravity (CG)

There's been a lot of discussion about CG lately, as we are all trying to get the V200D01 from pitching-up when coming out of forward flight or in windy conditions. It seems that pitch-up plagues flybar-less helis. I don't experience it with my flybar heli, nor do I hear about it being a problem with flybar helis. One cure for the V200D01 is to move the CG forward a little.

There are very complex studies and very simple methods for checking or changing the CG. Good references are at www.rchelicopterfun.com for all helicopters, Dsobbe's post #572-575 & #581 at http://www.rcgroups.com/forums/showt...282125&page=39 regarding the V200D01, and his post #17 on THIS blog.

Normally, CG is centered at the main shaft. You may change CG by moving equipment or adding weight ahead, or behind, the center-mast. By doing so, the heli becomes nose-heavy or tail-heavy. Tail-heavy is not good! Nose heavy seems to help smaller helis with 3G stabilizing gyros to counteract pitch-up, whereby the nose lifts upward when coming out of foward flight (FF). Some say that it is because the 3G system on the Walkera V200/450/500 D01's are lower-tech compared to Align's 3GX systems, but that's an argument for another day.

Measuring the CG:
The amount of weight and the distance that the weight is placed from the main shaft, changes the results that you get.

*The amount of weight can be measured.
*The distance of the weight, from mast-center, can be measured.
*The CG "offset" can be measured.
*The performance results can be monitored.

There are two ways that I know of:

1. Use a balancing rod (lower rod in photo below), placed through the frame of the heli. Move the equipment or add weight as desired. Lift the heli by the balancing rod and mark the position of the rod when the heli balances. Measure the distance from the mark to the mast-center and you now know the CG offset in inches or millimeters. Measure the amount of weight and its distance from the mast-center for reference. Monitor the results.

You can also use this method by placing the balancing rod under the rotors when they are turned length-ways to the heli.

2. The method that I use is "angle of degrees". By holding a disengaged rotor, while turning the heli on its side, the results are as follows:

*Level- CG is on mast-center
*Nose points downward- CG is forward of the mast-center
*Tail pointing downward (bad idea)- CG is behind mast-center

You can move equipment or add weight to change the angle. Then, simply monitor the flying results. Add, shift, or remove weight as needed, to achieve desired flight results.

For me, I like to keep it simple because I have to "think" all day at work. So for me, it is either is a LITTLE nose-heavy, VERY nose-heavy, or somewhere in between. It either "pitches-up" in FF, or it doesn't. When everything is adjusted and well, I make a note the angle.

The above examples refer to Lateral CG. There is also Verticle CG considerations. Maybe we'll dive into that another day. But that's a topic better explained by Dsobbe! (hint)

***SEE POST #55 FOR CG MODIFICATION PHOTOS!***
.
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Old Jul 03, 2011, 04:27 AM
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Hello.
I have reviewed and set as my new V200D01 comentais, now makes a coaxial stationary, but when I fly has a drift, always correct to stabilize it.
Is there a trick to not have this effect drift?
Thank you.
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Old Jul 03, 2011, 10:04 AM
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Quote:
Originally Posted by gemini673 View Post
Hello.
I have reviewed and set as my new V200D01 comentais, now makes a coaxial stationary, but when I fly has a drift, always correct to stabilize it.
Is there a trick to not have this effect drift?
Thank you.
Begin with your Trim is set to 50% for Elevator and Aileron (right-stick, left and bottom switch) and Rudder (left-stick bottom switch). Throttle trim set to 0% (left-stick right switch).

Which way does it drift? Does it drift in a hover or when moving forward?
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Old Jul 03, 2011, 12:09 PM
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The drift is forward and sideways.
when I go forward, I have to counter to stop it, not just release stick, same thing happens when I turn in flight.
Derivatives are always in flight, counter to always correct.
Maybe I'm used to the nobility of cb180z.
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Old Jul 03, 2011, 01:18 PM
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Quote:
Originally Posted by gemini673 View Post
The drift is forward and sideways.
when I go forward, I have to counter to stop it, not just release stick, same thing happens when I turn in flight.
Derivatives are always in flight, counter to always correct.
Maybe I'm used to the nobility of cb180z.
That's an easy fix! Go to Page #1 of this blog. See Step Two- levelling. That should do it!

Keep in mind that the helicopter will continue in the direction that you last commanded it to go. You must give opposite stick in order to stop the the heli from continuing.
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Old Jul 05, 2011, 03:39 PM
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spinning out of control

I fly my v200 and then after a few seconds it begins to spin left (if flying tail in, tail wants to swerve to the left).

I feel like perhaps one of the gears is slipping. From the naked eye, none of the tail gears are stripped. Do I need to make them snug? Do I need to clean them out? It will fly fine, but I feel like after a while, it will spin out of control.

What could be the cause of this? SHould I just replace all 4 tail gears anyway?
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Old Jul 05, 2011, 10:49 PM
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Quote:
Originally Posted by guynexdoor View Post
I fly my v200 and then after a few seconds it begins to spin left (if flying tail in, tail wants to swerve to the left).

I feel like perhaps one of the gears is slipping. From the naked eye, none of the tail gears are stripped. Do I need to make them snug? Do I need to clean them out? It will fly fine, but I feel like after a while, it will spin out of control.

What could be the cause of this? SHould I just replace all 4 tail gears anyway?
Sorry, I was offline all day.

It is probably the TAIL SLIPPING that's causing the problem. There's two possibilities.

1.) Since the gears look okay, I would first try snugging them. If you decide to order/replace gears, replace them all, but save the old ones that do not appear damaged. Also, when you take it apart, remember to look for the two gears that have a washer on them. Only two of the four have them.

2.) Second possibility is the Tail shaft. I had the same thing happen and all my gears were fine. As it turned out, the Carbon Fiber (CF) shaft had broken inside the tail boom at the very end. It would slip now and then and cause erratic behavior.

Hope this helps!
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Old Jul 06, 2011, 09:18 PM
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Tail positioning at power-up

Start by ensuring that the tail-gears & tail-drive-shaft are in good condition and snug.

* Set the Flight Mode switch on the Receiver to ADJ
* Servo: power-up and let the servo center wherever it wants, then unplug battery. Don't move the servo after that.
* Servo Horn: install Servo Horn as near to 90 degrees as possible, within a tooth.
* Steering Bracket: adjust the long tail linkage until the position of the "L" shaped steering-bracket is 90 degress to tail boom and tail shaft
* Tail Blades: should be at 0 pitch upon power-up.
* Set Receiver Flight Mode back to WK.

Important: Be sure to set your Trims back to 50% BEFORE you power-off the TX. Otherwise the TX will ADD the old Trim setting to the "centering" each time you power-up. Eventually, the servo binds and burns out or you lose partial control of rudder.
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Old Jul 06, 2011, 10:00 PM
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Getting better at Flying..

What's next you ask?

I've been flying for 6 months now. All my previous instructions and settings are to help those learning to fly or wanting to tame their helicopter. After you've mastered all the flying techniques from the "Flight School" at www.rchelicopterfun.com, then you can start adding a little more ELEV-AILE EXT and RUDD EXT for doing circuit flying. Gyros stay the same because they simply "balance" the heli.

When is it time? When you go out everyday and fly without crashing and you can do all your orientation manuevers, all nose-in manuevers, circles, pirouettes, and circuits.

Make very small adjustments (almost un-noticable changes) until you are comfortable with the increased response of your V200D01. Here is a tiny adjustment I just made tonight to the AIL/ELEV Extends and to the RUDD Extends after six months of flying. ELEV-AILE is hardly noticable from the previous settings in post #31

Happy flying!
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Old Jul 10, 2011, 09:51 PM
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Center of Gravity & Battery Modification

What started out as a way to move the CG of the V200D01 slightly forward, in order to eliminate pitch-up, has another advantage, ease of use!

Dsobbe and I were tossing around ideas for changing the CG. He decided that moving the battery forward or backwards, like Align does, is a good way to change CG. As it turned out we weren't the only ones who have tried it. However, Dsobbe came up with the 11/16" forward without added weight low on the frame and it works!

My Modification:
I started by cutting out the crossmember in front of the frame. I stuck some "normal size" velcro (fuzzy side) on top of the landing gear strut. Then, I stuck small pieces of "micro velcro" (hook side) onto each battery. It's a nice and clean installation and holds the battery securely!

Two advantages came from this modification:

1. The heli does not Pitch-up" when coming out of FF or circuits, WooHoo!
2. It's much easier to swap the battery and power-up each flight.

Try it!

Another awesome Mod to correct pitch-up is Dsobbe's shaft-collar mod! See post #822 at http://www.rcgroups.com/forums/showt...282125&page=55
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Old Jul 11, 2011, 07:25 AM
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Very neat mod! Slipping a piece of an old, or sample, credit card between the velcro pieces easily separates them and will allow quick insertion and removal of the battery.
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Old Jul 11, 2011, 08:09 AM
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Quote:
Originally Posted by dsobbe View Post
Very neat mod! Slipping a piece of an old, or sample, credit card between the velcro pieces easily separates them and will allow quick insertion and removal of the battery.
Good Tip! Thanks for all your input on this Mod!
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Old Jul 16, 2011, 03:10 PM
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V200D01 Gone Wild!

Back on Post#32 I showed you the Z180 Blades that I ordered accidentally. They're 1/2 inch longer each, adding 1 inch to the rotor span. Well, I tried them. It's all good now, but...

...when I first left the ground with these blades, the heli went NUTS! I mean almost totally out of control! So, I shot it up in the air to give me enough time to switch "on" Dual Rates. I got it back to Terra-Firma, but not without a fight. It was like wrestling a swordfish in the deep sea.

Long-story-short.. I had to re-adjust both ELEV/AILE & RUDD Extends; plus adjust all three Gyros ELEV, AILE, & RUDD. It's all good now, nice and stable again. Whew!

The downside is that when I go back to the shorter blades, I'll have to re-adjust everything all again. That is the one downside to electronically controlled stabilization (flybarless) helis. If you change something, you have to re-tune the electronics. My flybar'ed CP 450 never needs adjusting. You fly it, bring it home, go fly again, without ever having to change a thing!

Happy Flying!
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Old Jul 17, 2011, 02:13 PM
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Quote:
Originally Posted by HeliGriff View Post
Back on Post#32 I showed you the Z180 Blades that I ordered accidentally. They're 1/2 inch longer each, adding 1 inch to the rotor span. Well, I tried them. It's all good now, but...

...when I first left the ground with these blades, the heli went NUTS! I mean almost totally out of control! So, I shot it up in the air to give me enough time to switch "on" Dual Rates. I got it back to Terra-Firma, but not without a fight. It was like wrestling a swordfish in the deep sea.

Long-story-short.. I had to re-adjust both ELEV/AILE & RUDD Extends; plus adjust all three Gyros ELEV, AILE, & RUDD. It's all good now, nice and stable again. Whew!

The downside is that when I go back to the shorter blades, I'll have to re-adjust everything all again. That is the one downside to electronically controlled stabilization (flybarless) helis. If you change something, you have to re-tune the electronics. My flybar'ed CP 450 never needs adjusting. You fly it, bring it home, go fly again, without ever having to change a thing!

Happy Flying!
I had a similar experience with those same blades. But, not as radical as yours. Otherwise, I didn't notice any appreciable change in flight performance between the long and short blades. Then, I trimmed them to the same length as the stock blades. But, being very flexible it was difficult to set and hold tracking. I ended up throwing them out.
Since being able to adjust the battery position I've noticed that very small changes, +- 1/8", will effect gyro fine tuning. Nothing major. It's most noticeable when doing a pirouette. It just drifts during rotation. I'm wondering if I have the Ail/Ele gain turned up a little too high. But, if I turn it down any more pitch becomes sensitive in all flight modes. Any suggestions? Or, am I hitting my head on the limits of flybarless stabilization.
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Old Jul 17, 2011, 04:17 PM
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Originally Posted by dsobbe View Post
I had a similar experience... It's most noticeable when doing a pirouette. It just drifts during rotation. I'm wondering if I have the Ail/Ele gain turned up a little too high. But, if I turn it down any more pitch becomes sensitive in all flight modes. Any suggestions? Or, am I hitting my head on the limits of flybarless stabilization.
Well, we are running different batteries and our CG's will be a little different. So it's hard to compare exactly. For example, my pirouettes are actually better with the battery mod than before! Before, my heli wanted to backup in a pirouette. Now it stays on point. The bottom line is yes, you may be exceeding the forward CG limit for your heli, the way it's setup and the weight of equipment you're using, if you push it any further away from the mainshaft.

Did you see the Align 3Gx system has pirouette stabilization?
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