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Posted by Flyingboats | Sep 03, 2015 @ 04:39 AM | 1,427 Views
My trusty old V912 deserves a blog update. Having been crashed, bashed and thrashed for over 2 years, it's reached the absolute pinnacle of V912 performance heights this week with the latest mods. The flight before work yesterday was fixed pitch nirvana, smooth, responsive, powerful and utterly composed. Here's the flight video and the roundup on how the 912 has become flybarless, as well as double brushless...

V912 2xBL & FBL with Extreme 200SRX blades, 1st outdoor flight (5 min 55 sec)

After playing around with both flybar and the Tarot ZYX FBL unit, I decided it was time to chop the flybar off, and go full electronic stabilisation. Achieved this by glueing and melting the mixer arms to the blade grips, and hacksawing the top off the head. First indoor hover resulted in cyclic shakes, so after dialling back the FBL cyclic gains, we were set to go. First gentle outdoor flight wasn't bad, but put it this way, there was plenty of room for improvement!

V912 Double Brushless & Flybarless -Slow steps towards good flight (3 min 46 sec)
...Continue Reading
Posted by Flyingboats | May 30, 2015 @ 03:18 PM | 2,175 Views
I've read where a couple of guys added 3 axis flybarless controllers to flybarred fixed pitch helicopters. Comment was that it improved the flight characteristics. Decided to give this a go on my brushless 912, so removed the old orange receiver, built a base under the heli, then slung the ZYX underneath. Mounted an Orange satellite receiver on the helicopter's side and away we go.

Also changed the tail ESC to a HobbyWing unit (same as a Plush 10A) flashed with BLHeli. Tail response is way better although have now discovered the tail motor bearings are wobbling, so the combination of ESC and tail motor appears to be the issues I had previously where I couldn't get the brushless tail dialled in nicely.

Haven't finetuned the ZYX settings at all, just used their mild settings, but it flies better than ever. You definitely have to fly it more like a 3 axis/CP, although a heavier flybar would provide more stabilisation (this one is sub 10 grams).
Only issue is getting the nose up when swooping down. Had several crashes after this footage was shot.

Next step is to get rid of the flybar altogether! Will swap out the shaft/bearings and head with FX71 parts. Should be a useful weight saving, plus the negative aspects of the flybar will be removed. It won't self stabilise, but that doesn't worry me as I fly 3 axis regularly. The age of the flybar has ended!!

V912 ZYX with flybar (4 min 28 sec)

Posted by Flyingboats | May 02, 2015 @ 04:56 AM | 1,667 Views
Used the local school grounds for a parkfly this morning. I'd maidened my 450 last weekend in the backyard so wanted some room to see how it flew compared to my micros. Had some cracking flights with it, the little screamer Hisky HCP100S plus the FP FX071C.

All was good until the last battery through the 450, when I experienced a servo or linkage glitch as it was flying right towards me..... A rebuild is required!
450 Servo glitch and crash (2 min 25 sec)

Earlier flights with the 450 were excellent!
450 Precrash Flights (2 min 35 sec)
...Continue Reading
Posted by Flyingboats | Mar 28, 2015 @ 02:20 AM | 2,519 Views
The little Hisky Fixed Pitch 100 has become my favourite backyard helicopter at the moment. After following the RCGroups team's suggestion to add spacers for increased blade pitch (it was seriously lacking throttle response before), plus adding some HCP100 bullet blades to compensate for the stability loss through lower headspeed, the HFP100 has been transformed.

I tried a 6 axis V2 and was incredibly disappointed. The 6 axis makes it forgiving for a learner, but meant that lean angles were severely restricted and it slid it's way round corners instead of banking nicely. In comparison the 3 axis V1 is a delight, you can tilt it on it's side, point the nose at the ground, or even pull loops.

Favourite Backyard Flier Hisky HFP100 V1 (2 min 41 sec)

Posted by Flyingboats | May 19, 2014 @ 03:45 AM | 8,141 Views
I wonder what it is about the V912 that still grabs me? Despite flying micro CP's, and having a 450 sitting almost ready to fly, the V912's keep providing fun. So what are the attractions:-
  1. It's a nice size heli, big enough to see at a distance, small enough to fly at home
  2. They're tough! 12 months of flying my original, and despite a heap of nasty crashes I'm still on the original set of main blades!
  3. They fly well enough stock to be fun, but poorly enough that they're rewarding to modify (unlike the V922/HCP100 which flies hugely better, but is much more limited on how much you can improve it)
  4. They're fast enough with some mods to provide good entertainment
So after the aborted 3S experiment, I decided it was time to go brushless. The brushed motor failure rates were annoying me, and in particular the tail motors which just didn't keep up with my flying.

It's now been a couple of months since the first test flight, and interesting to look back on the experience. Definitely hasn't been an easy journey, primarily because I've struggled to get a gyro working decently. Even now the tail is still wagging around, although the heli is quite flyable. I wouldn't recommend this setup (different receiver with separate gyro) unless you have a decent programmable radio, and are prepared to put the time into learning how to set the parameters up on the gyro, and the radio. That aside it has been a good learning experience!

The gyros I tried were a GA250, HK401B, and finally a Tarot GY550. Worth mentioning that the reason I went to a separate receiver was because the V912 receiver board has restricted the servo response so dramatically, so I wanted to see how different servos and "full" travel would work.

So after a little development here's how the beast looks today, and how it was flying in the weekend.

Double Brushless V912 -Getting It Dialled In... (4 min 32 sec)

Posted by Flyingboats | Aug 19, 2013 @ 05:01 AM | 6,652 Views
OK Guys, notes on the 3S conversion. A disclaimer first though -this could be a really dumb idea, and could end in your helicopter going up in flames, or components otherwise suffering from a short life!! You may be better off putting the money into a good brushless setup instead, but I couldn't resist giving it a try....

Got a quick flight in on dusk last night, and a blast around the park at lunchtime today. Yes it's fast, but the main motor mosfet is getting pretty hot (surprise, surprise!). After consulting one expert at work today he's suggested adding a heatsink and heatsink compound to the fet. Also the fet heats up the moment the battery is plugged in (I've removed the switch), and theory is that when the motor is not running and low motor speeds are where the fet gets hottest. It also trips/cuts out if you open the throttle gently, so getting off the ground involves connecting the battery and binding, then lifting off quickly. Once in the air it seems OK.

So, onto the build:-

Rhino 3S 750 MAH
HB CP3/CPX 370 motor
Uprated wire, soldered direct to PCB
Sanded some width of the trailing edges of the main blades
HB DD tail motor
HB tail rotor (note the grub screws didn't fit!)
HB tail fin and motor mount Reading
Posted by Flyingboats | Jul 04, 2013 @ 04:57 AM | 5,115 Views
I've had a heap of fun since starting into RC helicopters 18 months ago, and reading all the fine posts in RC Groups. Early on I couldn't believe all the mods people were doing to the V911's, but 12 months later I find myself doing the same thing with the V912, and having almost as much fun with this as flying it!

Out of the box the 912 was a bit of a bus, with really low cyclic response, but a fast bus nevertheless! Had been experimenting with servo arm extensions to see what sort of travel I'd like, and broke into the servos and tried different resistors across either end of the feedback pot. Ended up with 2.2K resistors (largest on hand) increasing throw by around 70%.

Took the bits into work the following day, and one of the engineers was kind enough to solder in PCB mount 4.7K resistors. Throw is about 2.5 times stock (measuring distance point to point on outer hole, ~10.5mm's) so I can dial it back with the 9x. Unfortunately one of the resistors was protruding a little and broke off on reassembly Tried resoldering, but found I needed a new resistor as it had broken.... Dang but they're small!

Even with the servo extensions I'd been getting really small bank angles (maybe 25 degrees right, and 15 left). So as well as modifying the servos I moved the battery up higher to raise the centre of gravity.

The resistors extended the range of movement massively, but also shifted the centre position. I biased the servo centre position to get a little more throw backwards and to the left.

These are what I used in the servos:-

The results:

Servo movement:
V912 Servos (0 min 49 sec)

Test flight:
V912 Backyard Flight & Mods (4 min 7 sec)