4.5 gram servo (class)

[Konrad]

There has been some discussion about the 4.5 gram class of servo here.

Blue Bird servos at Aloft Hobbies

Now that it looks like KST is destroying their distribution network, it is time to look for another servo brand. I’ve loved the MKS servo but their price structure didn’t make them a good value for my ships or my style of flying. Futaba doesn’t offer the range of servos I use. And historically...

forum.alofthobbies.com

I'd like to open it up to a wider discussion inclusive of all brands. What has driven my interest in looking at the 4.5 gram class is the need to give the FAA the one finger salute and stay under 250 grams all up weight.

Historically I've used this class of servo in my rubber band to R/C conversions. These often are little more that R/C guided free flight modes. But as of late I've actually had some high performance type modes in this weight class.

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www.hippocketaeronautics.com

I thought I had used just about every brand of 4.5 gram servo, but looking at Aloft's sales page I see I haven't. In the old days 20 years or so ago I used a lot of analog 4 to 5 gram servos. I've come to the conclusion that the digital servo is far superior. I also like the idea of using a single cell lipo and metal gears would be nice but not critical.

So I'd like to ask what are your opinions or experience with these 4.5 gram class servos?

I've had real good luck with the Emax brand but have never used these. Anybody know how the amplifier performs on a single cell lipo?

Emax ES9051 Servo - 0.8Kg (11.11 oz in), .09 sec - 4.1 grams

5 grams, digital, inexpensive.

alofthobbies.com

Another no nonsense brand in PowerHD. Anybody know how the amplifier performs on a single cell lipo?

Power HD 1440A - Micro Servo - 0.8 kg (11.11 oz-in), .09-sec - 4.4g

The Power HD 1440A Micro Servo is designed from the ground up with small models in mind.

alofthobbies.com

Nether of these is spec'd for 3.7v but many servos such as the BMS101DMG will work and work well on a single cell lipo.

Since I'll be using servos off spec I really rely of burning in my servos before using then particularly if I'm glueing them into the airframe. I got into the habit of burning my servo when I learned that my Multiplex radio offered this function. I see that most servo testers now offer something close to this.
Most servos fail with in the first 3 minutes of use. How often do you hear the servo failed on the first flight with the result being the loss of a model on the maiden flight. Most electrical components will fail early if subjected to over heating during the assembly process. With the small size of the servo board it is easy to over heat things particularly when soldering on the leads. To weed out these premature failures I burn in my servos for 5 minute free running them on the bench. I also do a second burn in for a minute or so after the installation to make sure there are no issues with the hinges and linkages.

Servo Tester

Servo,Tester,STV2.3

alofthobbies.com

So another question is do you guys subject your servos through some kind of acceptance criteria before installing them into your airframe? And if so how does this criteria look?


All the best,
Konrad

 

[Hank GB Z]

Hey Konrad,


I use those Emax 5 g servos in my Mint 2 on 1 s. Speed is fine for me and I’ve not had any brown out issues running the DSMX rx on 1s.
Though I am diligent about checking the battery before flying.

Personally I’ve used those emax 5 g servos in several thing lately and I like em. Can’t beat the price. I had one of those power HD servos go bad But that was after many flights.

Hank

 

[Konrad]

Thanks Hank.

I know you and I use to use a lot of Hitec servos. I'm thinking the HS50 but I recall you going to even smaller like the HS35. In your opinion where does the small Emax fall?

I find that generally the Emax servo (digital) is much better than the same priced and sized Hitec analog servo. (Ok, the Hitec is about 50% more expencive)

On the single cell how far down do you let the voltage go? I run between 4.2v an 3.65v. I try to change out the battery at 3.85V.

 

[Hank GB Z]

Konrad,

I don’t like the Hs-35. It’s expensive and the gear train is very weak. The emax is a better servo in those regards. I haven't tested the speed or the power of the servos side by side, i just tend to buy differnt types when i see them. But bassically i can get 4 of the emax servos from Aloft for the price of one HS-35. Now the HS-40 is bigger but it's much more economical and it is ok. It's more like an HS-55 replacement. My friend Chris is using Hs-40's in an HLG he made but he's using a circuit to step up the volts to 5v from 1 cell lipo. He says it works well but he's right at the max for amps on that circuit he's using. I'll see if i can find that a link to the circuit he's using.

I go to about 3.85v as well. Honestly i've never pulled the battery to charge it while at the field. I'm normally done flying for the day before i get to that point. Now on the slope that might be different but it's hard to find just the right slope conditions for that little glider.

Hank