Motors in the shop not 4S compatible ?

TonioFlite

Junior Member
Hello, I just received my Quadcopter D pack from Flite Test, and I see that on the motors, there is written that I have to use smaller props with a 4S battery. Could you tell me why ?
Can't I use the same (10 x 4.5) provided with the pack to use with my 4S battery ? I don't see why this would actually be a problem ...
Thanks !
 

Craftydan

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higher voltage -> higher RPM -> higher current draw if you use the same prop = burnt motor.

As you step up in voltage, you'll need to step down in prop size to lower the load on the motor. If the original prop was properly sized, however, you will still gain an increase in thrust on the new smaller prop because it's spinning ~30% faster.
 

TonioFlite

Junior Member
Ok so it is impossible for me to use my 4s battery with this Emax 2213-935kv motors provided by Flite Test with those 10 x 4.5 propellers...
I understand you told me it would be with SMALLER props, but as my goal is aerial photography, I am affrait that smaller props would make a less stable image... don't you ?
 

Craftydan

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Impossible? No. Potentially damaging? Absolutely.

Less Stable? Not at all. So long as the motors aren't being strained, yet have a high enough RPM to respond to changes, the stability will depend more on the flight control board (FCB) and ESCs-- there is a tendency of longer prop -> greater stability, but that doesn't make getting a clean image impossible at all. It will increase the agility of the platform, but the increased responsiveness can be managed in the chosen FCB. On the flip side, the higher voltage pack can give you longer flight times and larger cargo capacity (those two trade between each other).

The higher RPM will work against you in vibrations (which leads to Jello), but every rotorcraft will vibrate, even when you do your best to clean it up. You will have to have some form of vibration isolation on your camera in either case.

Are these motors inappropriate for AP? No. Are there motors better suited? Sure, but these are good middle-ground motors for a medium sized quad -- capable of being pushed aerobatically on a light-but-large platform, but equally capable of a modestly heavy lift. Your FCB and ESCs will play more into this than this motor/prop combo.

I suppose my overall point is don't expect clean video out of your maiden flight (although I recommend you don't maiden with camera gear anyway) -- your first few AP videos will look terrible. They might look amazing to you at the time -- that's great -- but looking back you'll see how far you'll come. Improve the tuning on your FCB, continue to reduce vibrations, and continue to improve isolation. Every positive step you make the video gets just that much cleaner.
 

TonioFlite

Junior Member
Well thanks very much for these detailed answers !
So yes I should buy 8045 propellers (it is written so for 4s on the motors I received, instead of 1045 for 3s...). Actually it's pretty cheap and I guess you're right with the FC / ESC combo > Motor / prop combo for the Stability I need... I have an APM mini board with GPS which is kind of more accurate than a simple Naze 32 for the "tuning" and everything you're talking about (at least I hope so..!).
And now for the ESCs : those provided by Flite Test in my Quadcopter D pack are " EMax BL Heli 20 amp, with BECs" so I hope you will tell me they will provide a good job for the goals I am setting for the future, but it would also be welcome if you'd have to tell me "No ! They're good for beginners but you'll soon have to buy some new ones... and also some new motors by the way..." ;)
At least I know they accept 4S battery, but yes I'm quite new in the Hobby and I hope I haven't bought everything wrong...
Thanks again
 

joshuabardwell

Senior Member
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It's far from a given that a larger prop will be more stable. The stability of the platform depends on many factors, but in as much as the props are related to stability, smaller props may be more stable. Smaller props spin at higher RPMs and have less inertia. This means that the FC can change their speed more rapidly to adjust their thrust output. The reason that you think of larger props as more stable (IMO) is that larger props are typically associated with larger copters, and larger copters are more stable simply because they are more massive.

There is a bit of a balancing act between the size of the copter and the size of its props. A larger copter needs to have larger props because it needs more thrust to get into the air. The larger props are slower to change their speed, which makes the copter less responsive, but that is counterbalanced by the fact that the copter is more massive, so it is more inherently stable. If you were to somehow build a 500 gram mini with 10" props, you would probably find it to be less stable than the same copter with 5" props.

When it comes to a camera platform, the tuning of the flight controller should be the dominant factor in how stable it is, assuming no wind. Hovering in still air is easy regardless of your prop size. When wind comes into play, a heavier copter will be more stable than a lighter one, and a copter with small props will be more stable than a copter with larger props.
 
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TonioFlite

Junior Member
Ok thanks a lot !!! You guys give very quick and clear answers :D
So for my other configuration/setup questions : will my ESCs limit me or not really ... ?
 

Craftydan

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For now, not at all.

For the long term . . . probably not.

They're not "the best ESC ever made" by a long shot, but they're really not bad at all.