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Old Nov 09, 2011, 10:33 AM
bobepine's Avatar
Joined Jun 2011
7,400 Posts
Mini-HowTo
Genius CP 6 Axis Solutions

Introduction

Since the Genius CP hit the market, just recently, a vast majority of people who tried to fly this heli have experienced stability issues when flying in 6 axis mode. The reports vary from severe ailerons and elevator drifts to light drifts that can sometimes be eliminated using flight trims and subtrims. Very few people reported having a stable heli in 6 axis.

From new out of the box, most pilots reported having a left/backward drift with varying degrees of severity but there are also reports of helis drifting right and forward as well, though left and backward drifts have been reported a lot more frequently.

While some people made due with trims subtrim and program mixes, others gave up trying to fly this heli in 6 axis mode and moved on to flying in 3 axis mode as it has generally been far more reliable and stable for most pilots.

Long discussions have taken place to establish an understanding of what this 6 axis sensor is supposed to do and how it works. A consensus has been reached that the 6 axis sensor essentially acts as a plumb bob. What this means is that when the heli is tilted in any direction, the 6 axis sensor commands the alierons and elevator throw to compensate. In simple words, when the heli is tilted, the swash plate moves by itself to correct the tilt automatically. This is the main difference between 6 axis and 3 axis because in 6 axis, the swash plate movement when tilting the heli is minimal. The pilot has to do the corrections manually whereas in 6 axis, the heli corrects itself automatically. This also means that in 6 axis, the heli can not fly inverted like it can in 3 axis. There are limitations to the 6 axis sensor, however, and it shouldn't be expected to stabilize the heli with the same accuracy as a 4 channel heli that uses a weighted stabilizing flybar. The genius CP remains a CP heli even in 6 axis mode.

Different fixes and theories have been tested in an effort to improve the drifting issues the Genius CP suffers from in 6 axis mode. benmlee has been advocating modifying trimming the foam on which the receiver is mounted to in order to reduce vibration. He believes that vibration affects the 6 axis sensor and that by reducing the receiver vibration, the heli flies better in 6 axis. Benmlee recognizes two separate issues in 6 axis mode which he categorizes as follows.
1-Hard drift: This means the heli drifts heavily and gains momentum rapidly making it very difficult to fly. (This has been experienced and reported by many posters, many of which decided to scrap the idea of using 6 axis and are now flying in 3 axis happily with no drifting at all.)
2- Mild drift: This means the heli still drifts but mildly and on many occasions this can be helped with flight trims and subtrims. (This has also been reported by many posters, many of which still make due and keep flying in 6 axis. Mostly beginners, indoor flyers or precision flyers.)

benmlee adds that while reducing vibration to the receiver helps solving the hard drift issue, this fix has its limitation because it does not eliminate the constant mild drift. You can read about ben's work here: http://benmlee.com/Genius_6axis_Fix.htm

Personally, I went a different route in trying to solve the drifting issues in six axis without making a distinction between a hard drift and a soft drift. I consider both issues to be the same issue but with varying degrees of severity. As such, both issues inherently required the same solution.

In this thread, I will write about some tests I did. I will also post images, videos and explanations regarding what I did to fix my heli and I hope other people can benefit from this information. If you decide to tackle your 6 axis issues with similar or different methods, you are free to post your work and your findings, here, as well. Questions, comments and polite well-meaning criticism are also welcome.

Regards,

Chris
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Old Nov 09, 2011, 10:33 AM
bobepine's Avatar
Joined Jun 2011
7,400 Posts
Development

Development

Initially, my heli wasn't flying well in 6 axis. It was drifting left and backward, and after a few crashes and hard landing, the drifting became severe so I switched over to 3 axis and decided to forget about 6 axis.

Soon after, I broke my landing gear and decided to make my own. It was made of aluminium and it was quite heavy and stiff compared with the original skids. It looked like this:



One night while flying indoor I decided to give 6 axis a try again, and to my surprise the hely was flying well. Being a beginner CP pilot, I crashed often and I had to straighten my metal landing gear often. I eventually noticed a pattern depending on which way the skids were bent. I ended up posting a video where I create right drifts and left drift at will by simply bending my skids. I concluded that the heli had to be leveled with the ground when binding with the receiver i order to fly well.

This led other people to test binding the heli on an angle and even tooppled on its side. No one was able to replicate my results. I seemed to be the only person who had different flight characteristics when I bent my landing gear one way or another to tilt the heli during the binding process. In other words, very few people agreed with my findings that the heli had to be leveled with the ground during the binding process. That's because I was wrong.

I ended up having a discussion with livonia bob who hellped me understand the different implications between tilting the heli and only tilting the receiver. Without doing any tests per se, logic was telling me that bob was right. I then tried attaching weights to one side of the skids only to see if perhaps my landing gear was too heavy and affecting the center of gravity. Of course, putting weight on one site of the heli only caused the heli to drift, and I then concluded that indeed bob was definitely onto something and that my results were different than anyone else because I was the only one using heavy metal skids.

I later changed my mind one more time when I was attaching metal skids to a bare-bone frame because I noticed that the metal of the skids was way stiffer than the plastic frame and if I bent the skids, the soft frame would bend immediately and stay bent while held by the metal skids. What this did is when the front of the frame twisted as I bent the metal skids, the angle of the receiver was altered. In other words, bending metal skids was bending the frame and tilting the receiver.

From there I decided to follow bob's insights and I built the first version of the adjustable tray for the Genius CP receiver. It looked like this:

It was not pretty and it was heavy but it worked! I was able to create a drift in any direction using no trims on the transmitter simply by adjusting the adjustment bolts. At that point, I knew I had found a solution but it had drawbacks. It was simply too heavy resulting in short flight time and premature wear on the main motor. That little motor was running hot.

I then tried using a thin aluminium tray instead. I also removed the nuts and used lighter springs instead. It looked like this:

It looked better but it was still too heavy. I was trying to think of what I could use instead of the bolts as adjusters. OnceAFly suggested using micro servo linkage and until now I haven't found anything better or lighter. It then looked like this:



Still too heavy, although the linkage reduced the weight by a lot. I don't remember who(sorry) but someone suggested using carbon fiber for the tray instead of aluminium. Jasonjetski sent me some carbon fiber plate but before I received it, a friend happened to have some and he gave a bit of it to me. The next version of this modification looked like this:



Then I decided to drill holes in the tray to make it lighter and OnceAFly suggested using small springs from cigarette lighters. This lead to the latest version of this modification which looks like this:





The total weight of the modification is 0.7 grams which is quite acceptable.

I'm reserving other posts, below, as I will most likely make some more modifications to this design in time.

By the end of the week, I will have shipped kits to make this modifications to ten people. 6 of them are members on rcgroups and 4 of them are people who contacted me on YouTube and who I offered to help. I don't charge anything for them and I don't plan on making too many more because it's bad for my health as I don't have the proper equipment to work with carbon fiber.

If you're a beginner pilot who doesn't have the option to fly comfortably in 3 axis, you can contact me and I might be able to help you get your heli sorted so that it will fly well in six axis.

Finally, here's a couple videos of how I put together this modification and a flight video to show how a beginner pilot manages to fly a CP heli in 6 axis mode.

Here's hoping this will help some of you enjoy your Genius CP in 6 axis mode.

Regards,
Chris

Genius CP -How to -6 Axis fix (Part 1) (6 min 11 sec)

Genius CP -How to -6 Axis fix (Part 2) (2 min 47 sec)

Genius CP with modded tail rotor blade (6 min 55 sec)
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Last edited by bobepine; Nov 13, 2011 at 07:58 AM. Reason: Adding content
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Old Nov 09, 2011, 10:34 AM
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In this post, I will show some adjustments made to the receiver tray and what it does. I will show this without rebinding the heli to the transmitter and I will also show this when rebinding the heli to the transmitter. Video should be uploaded sometimes in the next few days.

Regards,
Chris
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Last edited by bobepine; Nov 09, 2011 at 11:49 AM.
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Old Nov 09, 2011, 10:35 AM
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Here's what I believe is the 7th design (V7) of this mod. This time I'm using 2mm. CF rods and solo pro grommets to hold the tray in position. The rear adjuster is still linkage because It's too hard to reach back there to adjust grommets. The grommets are super tight on the 2mm shafts so they don't move. This is harder to adjust than the linkage version of this mod. The grommets are so tight that I can't use my fingers to adjust tilt. I need to use a flat screwdriver to push up or down on the grommets. The benefit is that the tray stays put really well once it's adjusted right, I think it looks nicer (personal preference), and for those who are worried about vibration, this is a lot better as the CF tray is held between two layers of rubber instead of a stiff metal linkage. Makes no difference, though. Vibration hasn't been an issue with any and all versions of this modification.

For this version, I'm back to using only molding tape to attach the RX to the tray. It's stiff and it doesn't allow the RX to move. As such, the adjustments I make to the RX tray stay put much better. All in all, ups and downs. I like the linkage because it's quick to adjust, but being on springs, the tray can tilt a bit if I pull too hard on the battery lead or if I push on the tray when installing the canopy. This newer version is more difficult to adjust but the adjustment doesn't allow unwanted tilt beyond what I adjust.



Best,
Chris
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Last edited by bobepine; Nov 13, 2011 at 08:18 AM.
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Old Nov 09, 2011, 11:25 AM
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Old Nov 09, 2011, 02:15 PM
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Great thing that You created new thread. Ill post here my review of Your CF tray as soon as it arives. Thanks again and keep up the good work!
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Old Nov 09, 2011, 03:41 PM
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Nice job Chris! it was rough at the onset but your persistence has yielded a verifiable result. i am glad you are flying and sharing with us.
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Old Nov 09, 2011, 07:04 PM
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Well, I'm confused. Your modification would seem to suggest the gyro simply needs to be level when you start up, or am I missing something?
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Old Nov 09, 2011, 07:20 PM
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Nice! Good to see all under a page for easy reference thanks Chris and i will post my review once i get the package
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Old Nov 09, 2011, 07:26 PM
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It the Rx controlling the level of this heli when you bind. So if you put your heli tilted to one side when u bind, the heli will drift to the other side.
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Old Nov 09, 2011, 07:56 PM
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Just to share with you guys on the RX holder i have make while waiting for the chris cf holder hehe. Feel free to comment!


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Last edited by OnceAFly; Nov 09, 2011 at 08:14 PM.
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Old Nov 09, 2011, 08:36 PM
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Quote:
Originally Posted by OnceAFly View Post
Just to share with you guys on the RX holder i have make while waiting for the chris cf holder hehe. Feel free to comment!



Is anyone with a 2801 compatible genius using an adjustable rx tray? I would like to see if the tray solves the problem for those versions too.
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Old Nov 09, 2011, 10:55 PM
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Good writeup bobepine.
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Old Nov 09, 2011, 10:58 PM
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This certainly makes things much clear. It was just getting impossible to follow what was going on in the main thread.
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Old Nov 09, 2011, 11:55 PM
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Quote:
Originally Posted by Balr14 View Post
Well, I'm confused. Your modification would seem to suggest the gyro simply needs to be level when you start up, or am I missing something?
bebopine is saying that when the RX is switched to operate in 6-axis mode, the RX uses it's 3-axis accelerometer to determine how level it (the RX) is, then the RX sends commands to the EL and AIL Servos to try and reposition the swashplate's/heli's orientation to level (make "plumb" with the Earth's center of Gravity) itself (the RX) all the time. In 6-axis mode, the RX doesn't care about its history (how, when, or where it was before), all the RX cares about is its angular orientation with respect to "plumb" (Earth's center of Gravity) at that moment, and will always send commands to the EL and AIL Servos to try and position itself (the RX) so it is "plumb" with the Earth's center of Gravity.

If the RX is not physically positioned to be perfectly "plumb" with respect to the Main Shaft, then when in 6-axis mode, and it tries to level itself (the RX), the Main Shaft will be off at an angle (not "plumb" with Earth's center of Gravity). Having the RX plumb with the Earth's center of Gravity, but not the Main Shaft, will result in the heli having a constant drift in the direction that the Main Shaft is "off" axis from the RX.

bebopine's mod allows physically "dialing" in the RX's angular orientation with respect to the Main Shaft. Ideally the RX's PWB (accelerometer) should be positioned/orientated to be perpendicular with the Main Shaft.

Also for optimum performance/control, technically the RX should be positioned/oriented to have its AIL and EL axis's aligned with the heli's/swashplate's AIL and EL axis's as well.

I believe having the RX properly aligned in all 3 axis orientations, should also improve operation in 3-axis (Gyro) mode as well.
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Last edited by i812; Nov 10, 2011 at 01:39 AM.
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