My 450 PRO v2 FBL FPV build

[aForcefulThrust]

I like to live life on the edge

[hga77]

Originally Posted by aForcefulThrust

Why the lower kv rated scorpion motor and 13t pinion? Is that the best for 4s?

I'm gonna try answer this in a weird way so please bare with

One of our main objectives for successful fpv is - max endurance (increase our flight time). To achieve this we must follow a few rules:

1. Lower Head Speed
By lowering our headspeed, we increase our flight time. We lower to a headspeed that we and the heli are happy with. In other words a) enough headspeed to mantain a hover for a given blade pitch b) enough headspeed to fullfil our flying style and needs, ie. your acceptable performance c) enough headspeed to make our power system happy (ie. increasing efficiency out of our motor/battery/esc/blades). Doing so will let us acheive the optimum head speed for our requirements.

Why does lowering the headspeed results in increased flight time? The simple answer is a lower headspeed means lower current drain (lower amperage draw). This equals longer flight time. Low KV motors are more suitable for those applications since they usually have a higher Watts capability by having the luxury of being able to run higher voltages. This translates to a much lower amperage draw on say a 4s 2500KV motor than a 3s 3500KV because the power system is working off of higher voltage. All this because:

Watts = Volts x Amps

To change headspeed our best bet is changing the pinion, changing the motor, or changing both. We can ofcourse lower the headspeed with throttle curves etc but this is not a good thing to do because we will end up straining the motor/esc. Electric motors work most efficiently when running at around 85%-95% of their maximum rpm. Running a motor at 2500rpm when it's rated at 3500kv isn't effecient. The motor will loose power in the form of heat because it is not designed for this headspeed, resulting in lower flight time. We want less power consumption, less power waste, giving us more efficiency, more flight time.

2. Reduce weight as much as possible
Easy!

3. Scale flying
We are not interested in 3d flying such as inverted or high performance cyclic/pitch controls. Just hovering and doing large circuits in normal forward flying (and possibly some fast forward flying). So no need for high headspeeds, no need for a high rated kv motor. This will keep low power consumptions, longer flight times.

4. Bigger non- 3d blades increase effeciency
For this it's advised to increase torque from the motor so we can rotate those bigger/heavier blades better. To do this we add more volts. So, running a 4s system is better in this case since we will get more torque. We can also improve tail authority by stretching the boom and putting on slightly larger tail blades (we need this because we are using larger main blades).

Originally Posted by aForcefulThrust

Why the lower kv rated scorpion motor and 13t pinion? Is that the best for 4s?

Hopefully I've answered this above.

4s means we will be pulling less amperage. Every heli has a miniumum amount of power (eg. Watts) to maintain a hover.

Let's say, a 450 heli requires 200 Watts to hover.

Watts = Volts x Amps

3s
200w / 11.1v = 18amps

4s
200w / 14.8v = 13amps

Although a 4s will be heavier that a 3s with equal mah. But again you get the benefit of running lower current, higher voltage and having your 4s batteries potentially lasting/living longer than a 3s.

Originally Posted by aForcefulThrust

If I understand this corectly, the lower kv motor will turn slower, and the 13t(vs 15t stock) pinion will reduce headpseed ever more, so dosen't this kind of make upgrading to 4s kind of pointless? What if I just ran at a lower throttle curve instead of getting a lower kv motor?

I might have answered this above.

Good read:
http://www.chopperaddict.co.uk/chopp...t-tips-34.html

Good calculator:
http://www.ecalc.ch/helicalc_e.htm?ecalc


I'm no expert so guys please correct anything I said

[aForcefulThrust]

Thanks for the detailed response!! Helps explain allot!

She recently had a bad crash where she lost power for unknown reasons about 100-150 feet up. Video Tx was destroyed in the crash, so FPV gear is off for now I will get a 1.2ghz Vtx when I get a new one I replaced the ESC thinking that could have been the problem. So I'm half way to a 4s or 6s setup



After changing the ESC, I did a small test flight about a min long, and the motor was noticeably hotter then it ever was with the old ESC. Could this be a problem??

I'm still waiting on my usb link to set up governor mode.

[aForcefulThrust]

OK guys, I got a problem!

First time really flying it after the last crash, and the heli lost power AGAIN!!!

Once again, I was about to do a loop, started pulling back, and it just lost power! The servos were still working, bc I could level it out on the way down.



Thats the graph of when it crashed.. The only thing I notice is current spiked right when RPM's dropped. I'm thinking my motor may be bad, but I'm not sure. I could really use some help with this bc I'm stumped! 2nd time she just lost power and fell out the sky, After the first time I replaced the ESC. This is NOT fun lol... need to get her fixed!

[l14m]

Mmm I had the same or similar problem about a year ago.

Are you using the bec from your esc or a separate ubec. I was using the built in bec on my align 35 or 30 amp esc and with all my fpv gear and servos running through it I was getting brown outs. I've now fitted a scorpion esc and a separate ubec and have not had any problems since. You can also try a 470uf cap plugged into your Rc rx which will help with spikes and stop many brown outs.
Hope this helps.
Regards Liam

[l14m]

Here's a link to one.
http://www.fast-lad.co.uk/store/perf...p-p-11613.html
Regards Liam