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Posted by Flyingboats | May 19, 2014 @ 03:45 AM | 5,178 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 | 5,005 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 http://www.hobbyking.com/hobbyking/s...poly_Pack.html
HB CP3/CPX 370 motor http://www.banggood.com/Wholesale-Es...3-p-51340.html
Uprated wire, soldered direct to PCB
Sanded some width of the trailing edges of the main blades
HB DD tail motor http://www.banggood.com/Wholesale-Es...5-p-51343.html
HB tail rotor (note the grub screws didn't fit!) http://www.banggood.com/Wholesale-Es...1-p-50434.html
HB tail fin and motor mount http://www.banggood.com/Wholesale-Es...6-p-...Continue Reading
Posted by Flyingboats | Jul 04, 2013 @ 04:57 AM | 3,235 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:- http://www.digikey.com/product-detai...3-1-ND/2402115

The results:

Servo movement:
V912 Servos (0 min 49 sec)


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