250 - headspeed, pop and bog

[TracesOfNut]

Hi All,

My first flight of my 250 was just to hover. It got 3:30 with cells down to 3.7v. The battery is a 370mah 6s, so I expect shorter flight times than the 3s 850mah I used before. But I was hoping for more.

[ As I am typing I am not so sure on the flight time. I was just checking head speed and I think I turned off the transmitter at least once so the 4 minute timer may have been reset. I will check again, but the rest of the post is still valid. ]

I tested it with some 'pitch pumps' and heard the motor slow down a bit. This was to be expected thought as the esc doesn't have a governor mode controller and I had a flat throttle curve.

But, if I am going to learn some 3D on this heli, what head speed is considered minimum. Are these little blades less sensitive to high head speeds?

I think it got 4000rpm at 85% throttle measured with a tacho at zero pitch. I am using a 15t pinion on a scorpion 2206 that is running at the equivalent of 3800kv. Would I see a benefit from a 16t pinion? I wonder if the motor isn't being loaded up enough at the moment.

I rewound the motor and am not really sure if the result is better or worse than the original. I measured it at 1900kv. At the end of the test flight, none of the bits were any more than slightly warm. The motor was barely above body temperature. When I was running 3S, the 850mah nano tech was suprisingly warm and I think the motor was as well. So I am happy that more of the battery power is making it to the blades.

I am trying getting the weight down, which I know will help. and am going to try different battery options to make a lighter pack. The Robird controller also has a weight I can remove (and a governor, I just remembered). I think the AUW is a bit under 340g.

In summary (if you made it this far)...

What headspeed should I be aiming at for light 3d, Will a 16t pinion help extract more power from the motor?

Thanks for your patience and time.

[myxiplx]

I run a 16t pinion and have it governed to 4200rpm for 3D in my garden, and 4500rpm for crazy power.

It'll tic-tock quite happily at 4200 without any bogging. At 4500rpm I reckon I could do 30° tic-tocks if my fingers were good enough :-)

[TracesOfNut]

I retested my flight time this morning with a full charge and the governor in my Robird G31 set.

After 6:30 of hovering around the front yard, the batteries were down to 3.2 volts per cell. I hadn't planned on going that long, but I was trying to work out some weird tail behaviour. Other than the tail which was twitching every now and then, it flew quite nicely.

This time, the battery came down warm. A bit less perhaps than on the 3s setup. It is hard to tell.

So, it looks like 4 to 5 minutes will be ok. I am still not convinced that 6S is worth it for my flying style. I have enough to make another two batteries, so I will stick with it for a while.

I will try the 16t pinion and tidy up the tail a bit next.