Downside to picking a slightly larger motor?

[Pumpkinguy]

Let's say I pick a slightly larger motor than I currently require with the thoughts of using a larger camera in the future. Let's say with the current setup it gives me a 35% hover. Is there any downsides to that? Thx

 

[eskil23]

I guess that a overpowerd drone can be a bit jumpy in flight. I would try to use smaller props. It is easy to change to larger props if you need to lift more weight if you got the power.

 

[Carapau]

ESCs unless they have active freewheelinig don't like be powered too low-it can cause them to heat up pretty quickly. That's why in SR builds people aim for the 50-80% mark for the heli's constant throttle setting.

 

[R_Lefebvre]

Carapau, I don't think it's quite that simple. The overheating problem in heli motors which are over-geared has more to do with current than it does simple throttle application. In a SRH heli application, throttle is used to control rotor speed. If your pinion is too large, and you are using low throttle to keep the rotor at the right speed, the result is a huge current, even though the throttle is low.

In a fixed pitch situation like a multirotor, the load scales with the throttle application. So no ESC overheating should occur. 35% hover throttle is not at all uncommon.

Pumpkin: Biggest downside to a larger than necessary motor, is that it won't be efficient at lower loads. The exact same machine, with smaller motors, will actually fly longer.

 

[Carapau]

I stand corrected!

 

[Pumpkinguy]

Thanks guys. I am glad I went with the larger motors. When you start building you quickly notice that your AUW is gonna be heavier than first calculated.. All these 20 gram things you never thought of add up. Also, I may change gimbals and cameras. It's gonna be perfect with 16" props and I can take even more load with 17 or 18's. Cheers.

 

[PeteDee]

Mind you using larger motors means they are heavier so you need the larger motors/props to carry the weight.......

 

[Pumpkinguy]

It's neglible. 300 grams more for all 6 motors but they give 3000 grams more thrust.

 

[PeteDee]

Quite seriously, you gave stuff all info and used the word "slightly' as to how much larger the motors you were talking about....... and 300 grams and 3Kg more thrust, hardly "slightly" is it?

 

[Pumpkinguy]

I went from from a kde 4014-385 to then next larger motor 4215-465. I guess you are right. Slightly was not the right word as there is a big gap between motors. However they are closer in thrust when you compare 18" prop on the smaller one to 16" prop on the larger one, cheers.

build http://multirotorforums.com/threads/gryphon-1000-hex-build-with-ecalc-data.21951/

 

[PeteDee]

Hey all good mate, on the smaller MR's lower weight is absolutely key, on the bigger MR's you have more wriggle room and slightly bigger can gain quite a bit of performance.

 

[Pumpkinguy]

View attachment 22072 Here they are. Just waiting on bullets

 

[PeteDee]

Very nice, don't forget to post up pics of the finished and flying beasty.

 

[Pumpkinguy]

I have a build log going on here. It will be a beauty for sure. I just doubt it will fly. Lol

 

[Old Man]

Just use a larger, heavier battery if you end up with a sensitive throttle. Built a 1200mm kV 170 quad that without a payload required addition of 5.5kG of ballast to tame the throttle.

 

[twistedshifter]

It should fly better in gusty winds. Higher the thrust to weight ratio the better in unstable air. At least that is what I have experienced.