simple words :: simple content

It has been almost half a year since I have started with my flybarless project. For those who are interested in my very first flybarless build log, visit here.  So far, I have been very happen and satisfiied with the performance of the SK360 unit.

“It’s simply cheating!”

This is the phrase I always use to  summarize the performance of the SK360. It flies so smoothly even when the wind is pretty strong. Flips and inverted flights are so much easier to execute with external factors such as wind minimized. For the price I paid, I’m totally satisfied with the flybarless unit.

However, I always feel that there is a feeling of sluggishness when I have sudden pitch inputs on my collective. At first I thought it was the servos which are getting old and weak, but later I realized that it was possibly due to the design of my flybarless head.

From the above picture, it can be seen that the grip arms are pretty prone to flex. It is bolted on with a M3 cap screw, which I believe is the cause of all the sluggishness as when sudden pitch is given, the grip arms will flex momentarily. Thus, i’ve decided to treat myself with an upgrade!

There were a few choices, 3DX flybarless rotor head, RJX flybarless head, kasama cyberhead and FBH flybarless rotor head. Well, the choice was pretty simple actually, FBH flybarless head is very expensive, hence it is out of the picture. Kasama cyberhead is very nicely designed, but the reaplacement spindle costs US$15 excluding shipping! And the parts are not well supported currently, hence I decided to give it a miss. RJX’s flybarless head is butt ugly, so why would I want to punish myself Thus, I’ve left with the 3DX flybarless head I made my order through my favourite overseas hobby shop, readyheli.com.

The parcel came within a week! Look at all those mints

Everything needed for the build:

The 3DX head uses JR Vibe 50’s spindle. First,  the trust bearings are fixed into the spindle.

The spindle with the trust bearing is then pushed into the main grip. There are already radial bearings fixed into the main grips when they arrived.

Grease it up!

The picture below shows the 3 different type of stand-offs from the align pack. The one used for the 3DX head is the MIDDLE one.

Bolting the grip arms to the grips…

Installing the swash driver arms. One thing I like about the 3DX head is that it is designed with an integrated swash driver. Hence, I do not need to modify my washout base and arms to make one like in my previous flybarless build.

*take note*: Somehow, when the swash driver arms (plastic part) is fixed on, the direction of the arms are reversed. Hence, you need to use extra force to force it into the metal balls of the swash plate. I’ve checked with other on RR forums, and it seems that they are also doing the same thing.

Fixed onto my eRaptor! I had some difficulty in align the holes of my raptor’s main shaft and the holes in the 3DX main rotor hub. I had to file of around 0.5 to 1mm off the main shaft before the hole aligns. Another design problem I guess. I hope something will be done about it.

One of the greatest difference between this 3DX flybarless head and my old flybarless head is that the height of the grips is greater. 3DX flybarless head is 105mm from the top of the frame, whereas my previous raptor flybarless head is 95mm. I’m not sure what differences is it going to make, but i’ll test it out soon.

3DX with my custom design A123 eRaptor lower frames

Just more pictures to enjoy!

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One of the few problems that I faced when I moved to a flybarless raptor is the inability to set the pitch of the main blades. When setting the pitch on helicopters with flybars, the flybar is used as a reference line to measure the pitch of the blade. However, now that it is no longer being used, I have to find another line of reference.

Some methods proposed by the members of HF and RR includes placing the helicopter on a flat surface, and using the background horizon as a reference line. For me, I personally stuck a temporary flybar on top of my main rotor hub to act as the reference line. Although all these methods requires the helicopter to be on an absolutely flat surface, which means that a slanting table will cause the pitch measured to be inaccurate.

Recently, readyheli.com brought in stocks of a digital angle guage by Wixley. I decided to purchase one myself and attach it to my present thunder tiger pitch gauge. This digital Angle Gauge can also be purchased from Soaring Composites (recommended).

There were some suggestions posted by other users of this digital angle gauge to convert it into a digital RC heli pitch guage. Here some some pictures of it.

Here is my version of it. I hope that this will useful to all those flybarless pilots out there.

As mentioned, I am a proud owner of a Thunder Tiger pitch gauge. It has been serving me very well all these years, and I don’t intend to throw it away just because I’ve gone flybarless. Hence, I stripped it apart and stuck the digital angle gauge to the piece where it clamps onto the blade.

To make sure that the digital angle gauge is straight, i aligned the top edge of the angle gauge to the button of the “clamping mechanism” of the TT pitch gauge. And there you go! DIY Digital Pitch Gauge!

To use it, ensure that the helicopter is placed firmly onto the ground, or table top. You need to ensure that the helicopter will not wobble or shake while you are setting the pitch or zeroing the digital pitch gauge. Next, place the DPG (Digital pitch gauge) on the boom of the helicopter and zero it. This is on the assumption that the helicopter designed such that that the boom is perpendicular to the main shaft.

Now that the DPG is zeroed, you can now use it to set the pitch of the helicopter. Again, make sure that the heli is in the same position as when the DPG is zeroed.

Hope this helps!

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Around 6 weeks back (yes 6 freakin weeks),  I crashed my eRaptor (flybarless) due to lost orientation while trying some inverted flight. Basically, the heli plunged into the concrete drain tail-in. Hence, the boom was shoved into the heli’s main frame and as a result, I basically bad to rebuild the heli.

Although I already purchased the parts and spares prior to the 6 weeks delay, but exam was around the corner and hence I didn’t manage to find the time to rebuilt. On the side, I was also thinking of changing the flybarless head’s design include some levers instead of having a direct link from the swash plate to the grips.

One of my favorite designs was the one by Caotri @ Helifreak. Here is a picture of this design, and the build-log can be found here.

However, after struggling with the washout levels from thundertiger’s Raptor 30/50, I decided that it was not a good implementation for the Raptor series heli. This is mainly due to the following reason:

1. Too much slop introduced when using indirect linkage
2. There was an issue with the phase, with resulted in some cyclics interaction. Although this can be solved using the software mixing provided by SK360, however i rather not mingle with it.
3. It looks pretty ugly.
4. I had to reduce the swash mix to around 20%, which is really too little, in order to attain a -/+10 degrees of pitch. This is not acceptable as the swash movement will be too small, which may result to insensitivity of the pitch.

Hence, after much consideration, I decided to go back to direct linkage for the time being. On the other hand, i realized that thunder tiger has a upgrade part: PV0040 which is a very good fit to extend the grip’s post to minimize the delta angle.

PV0400:

Completed flybarless rotor head. As you may have realized, I milled off the top part of the main rotor hub which was previously used to attach the flybar. It looks much neater nice

On the side note, I decided to try Align’s Trex 600 series’ tail rotor grip. I’ve read from forums and heard from local flyers that the results were pretty good when they used it as a replacement for raptor 30/50’s tail rotor grip. One thing to note is that the Trex 600’s tail rotor grips includes TRUST BEARINGS! Which is one of the main reasons why Kasama and QuickUK’s tail rotor grip upgrades are so popular.

Picture of the trex 600’s tail rotor grip on my eRaptor. Its a perfect drop in.

Ready to fly again… and yea.. i know the canopy is pretty battered, but I’m going to change to a fibreglass one very soon. Check back soon

Oh btw … wordpress 2.7’s image insertion into posts still sucks like all previous versions. Wake up developers…

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I’ve added a build log for my eRaptor SK360 flybarless conversion. Check it out by clicking on the link on the right menu of this page. Or if you are lazy, please click here.

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