Jumping from 3s to 4s? || ADVICE NEEDED ||

[Montiey]

So..
I am having a blast flying my 3D printed micro quad around FPV with an AIO cam on the front. I notice it's sluggishness much more in FPV than LOS. My first question is… Is it overweight? All up without a battery, the weight is 186g.

It's 170mm, running Emax RS1306 motors with 3x3x4 props, DYS SN 16A ESCs, and a Naze32. I recently added the CM275T camera, but it's so teensy I can't feel the difference.



The battery is a 1300 3S, it weighs 112g. If the jump to 4S would help me, would I be looking at a battery of the same capacity, or smaller? I wouldn't want to add that much more weight of the extra cell, as I would be trying to get more power

Here are the two options I found, I can't make a conclusive decision of what capacity to use at 4S voltage:
https://hobbyking.com/en_us/turnigy-nano-tech-1300mah-4s-45-90c-lipo-pack.html

https://hobbyking.com/en_us/turnigy-nano-tech-1000mah-4s-45-90c-lipo-pack.html

 

[Ricci]

Weight should not be a problem with 3 blade 3040 props the emax has 340g thrust by 11.5 A, so all fine 100mah or 1300 mah it2 your decision 300mah dont will increse the flight time but add more weight.

 

[ElectriSean]

I think I would go with the 1000mAh myself, 1300 seems huge for a 3". How is your flight time on 3S?

 

[Montiey]

On 3S, I get about 4 minutes. I realized I should check to make sure that my step-down module can handle that voltage, too. If so, I'll look around for a good deal on a 4S 1000. EDIT: 7 to 21V input (I should be fine )

The HQ 3x3x4 props are good, in my opinion, but does anyone happen to have a magic prop for this motor on 3 or 4S? A couple of test sheets make it seem like this is optimal, but you never know.


…I also made the mistake of flying a battery that was already dead, today. I got about 4 seconds.

 

[PsyBorg]

I would go with an 800 - 1000 mah max size battery and would probably drop down to 3x3x3 props to start. I think if you drop down to 800 mah 3s with higher c rating you will notice a nice enough difference to not need to jump to 4s and retuning and changing props and all that.
Also going to tri blades will help a lot as well. 4 blades is a lot of weight to turn on high kv motors.

 

[Montiey]

I have some GF 3x3.5x3s I used originally. I had to go to 3x3x4s because I wasn't getting any usable power (with a really weak 1300, however). What's your reasoning for using more passive props and a smaller battery? Emax's own test data makes it seem like the 4 blades give the most power. I don't have any batteries smaller than my 1300s that could handle the 4000kv motors, but I'll test the 3 blade props again with my current setup.

 

[PsyBorg]

Sorry that was a typo. That should have been 3x4x3 on the smaller battery. I will bet you see a better result going back to the 3x3.5x3 now that you have the quad tuned so the motors are getting into their power band more. Should be similar or slight drop in power with longer flight times as the motors wont be sucking up as much amps to turn the weight.

I just had a look at the spec sheet for them motors. The 3x4x3 props on 4s give the most bang for the buck according to their spec sheet. That gives 340 g thrust with an efficiency of 2 g per watt.

The 3x3x4 props you are using on 4s give only 315 g thrust with 1.77 g per watt. Using the same props on 3s brings the efficiency up to 2.34 g per watt. So you are actually already on the best set up for the quad for power to weight. You have a thrust total of 242 g x 4 for 968 g IF all conditions are perfect.

So if you stick with motor / prop combo you use now and drop the battery weight you will get a nice improvement as the actual current draw will go down. This will bring the flight time per mah up as well. If you go smaller prop bigger pitch you will also get an improvement as the 3x4x3 props put out at 2.35 g per watts. Your power to weight drops but you get better real usable g per watt. At 182 g x 4 is only 728 total that is still more then enough to move the quad nicely and give good flight times. You will stay higher up in the rpm band but it will be producing more usable thrust. Thus dropping battery weight will bring the flight time per mah up as well.

Sluggish in FPV confuses me.. do you mean over all speed in the goggles looks slow or the reaction of the quad seems slow? If its reaction that seems slow then its your tune. Which could also be the lack of flight time you think you should have. If it is perceived speed in FPV that could be because you are used to sims with wide angle FOV and are now flying in 4:3 with smaller FOV.

Kids flying sims are flying 25 degree camera tilt and 35-50 speed settings with 100 degree FOV and look like they are cruising fast in videos. I fly 55 degree tilt and 85 speed settings with 50 degree fov and I look like I am going slow in a sim but in reality I am doing way faster.

 

[Montiey]

I ran some flights with the 3035 x 3 props. Way more power! I can run my packs down to 3.7v in 5:10 now, too. I don't need 5 whole minutes of flight time, so a smaller pack would be smart.

You mention that the HQ 3030 x 4 props are optimal, but I don't understand why that doesn't translate into my flights. Should've mentioned I have the 4000kv model, too. When I say sluggish, I mean strictly throttle power. Coming out of any loop, I have to punch the throttle really hard to maintain altitude. The 3035's feel better, but I still want to find a better prop, if one exists.

Edit: What about RotorX RX3040 Tri-blades? I found many positive reviews, and prop test data seems to support this. Maybe I'll order a set and try my luck

 

[PsyBorg]

Recovering from a loop and having to hit the throttle harder is the same thing I deal with on my Gremlin. Too much weight. You either have to drop weight most likely at the battery as thats the largest contributor. Or change the throttle center like I have to compensate for the muscle memory I have built flying more powerful quads so I physically place the stick in the same way I do on the big ones but the power out put in the quad is a bit higher.

Changing prop size and pitch will change power and efficiency but not where the "power band" is for the quad when weight and inertia are being factored in. All those numbers are from static testing under specific conditions.

 

[Montiey]

That seems about right. I transferred the electronics from my printed frame to an RCX H148CF.



All up, it weighs 180 grams without a battery. I have 2 more packs to test; a 850mAh 3S, and a 1000mAh 3S. I did a punch out test to the top of a 400ft radio mast to see if the weight would make any significant difference. Funny enough, it takes 8 seconds to get to the top, no matter the pack.

As you mention, the agility of the quad was increased a little bit with the lighter battery.

Blackbox file (1000mAh, 850, 1300, 1300, then 1300 respectively)CLFL_BLACKBOX_LOG_Montiey_%28RCX%20H14_20170831_180508.bbl.zip

 

[PsyBorg]

So is there a smile on yer face now? or are we still searchin for MOAR POWAH!!!

 

[Montiey]

M O A R P O W E R


I still can't quite hover at 1500 throttle; I think that's my goal.
In other news, carbon bounces much better than PETG :black_eyed:

I can't tell the difference between the 850, 1000 and 1300, except for a slight agility boost at the start of the flight. Towards the end, everything is the same, and all I notice is a shorter flight from the 850- not so much from the 1000.

 

[Montiey]

I got the RX3040T props on today. They are slightly more punchy, and definitely way faster. I can see how the agility of the quad really only comes down to weight- the change in thrust isn't enough to make a difference there.

Now my 400ft tower punch takes only 6 seconds instead of 8. I can also get a stable hover only at mid-throttle, which is cool. Amp consumption is higher, of course. I brought a couple of 1300s, a 1000, and an 850mAh 3S. I totally forgot I was flying the 850 and brought it down to uh… 3.1v…

For the sake of flight time, I would much rather stick to 1300 or 1000mAh batteries since I can't see a clear advantage with smaller 3S packs.

 

[ItMightFly]

I totally forgot I was flying the 850 and brought it down to uh… 3.1v…

Completely understandable! I couldn't stop laughing though. Glad you have figured most of it out. Hope to see final results!

 

[Montiey]

Now I just wish I had a DVR.