Caution: Savox SB-2271SG Cyclic Servo Bench Test Results

[Chris Sexton]

Video pretty much explains it. But I got a PM from Rob Cherry and a call from Dave with Anythingheli.com today about my Savox servos. I decided to bench test mine like Rob did, and I am not pleased with the results.


NOTE:
For those who might be watching this for the first time, if you read a couple pages in we discussed that what you are seeing in this video ISN'T an RX Brown out, but me applying way more torque than rated and stalling the aileron servo. See Rob Cherry's video posted later for the real issue.

[ame]http://www.youtube.com/watch?v=a2oIbm7EwnM[/ame]

[Chris Sexton]

OK Well public speaking isn't my forte, "um" and "excuse me" are not keywords for this video

[ragtop01]

I'd try higher voltage on the bec. Higger voltage means lower amps. Do the servos get hot?

[Chris Sexton]

Rob had the same results with a Quasar 75V BEC

[Rob Cherry]

Higher voltage with servos has the opposite result. They operate faster thus drawing even more current.

But none the less, this has now been confirmed to happen with two pilots. I've tried a quasar 75v bec on 6S, 12S inputs and from 5v up to 8.4v to the servos. Same with bec pro v3, all combos. Couple of quick pitch pumps and brownout! With an RX pack, it's solid, no brownouts. These servos have no ramp time, no wait period, instant on power surge drawing spikes that brown out even the largest and newest BECs.

My vbar log reports low voltage, system pauses for half a second while it browns out. Satellites start blinking afterwards. Not good!

Watching the video, yours behaves slightly different than mine. My system locks up during the brownout, and the satellites blink, notifying the user a brownout has occurred. Can you confirm this Chris ?

[Chris Sexton]

Sounds like an RX pack is in my future then. At least this will allow me to keep flying!

It's not that I don't like RX packs, I just prefer not to have to remember to charge something other than flight packs. Oh well.

[xfactor6]

Well i just tried this test with my 1267sg running them at 7.4 through bec(gryphon quasar), and they were fine. In comparison they are only a little bit slower and a little less torque than 2271. must just be those servos? Could it be the fbl unit? I have ar7200bx so not sure what everyone else has?

[Chris Sexton]

Rob's is VBar and mine is AR7200BX.

[vr360]

Hey Chris,

Sorry to see you guys are having this issue. A friend of mine is running the Savox on cyclic and tail but he is using the slower Cyclics. No issues thus far.

Knowing that the Align DS servos are power hogs, and they are savox rebranded servos, This is no shock to me at all.

Although the speed and torque numbers of the Savox are impressive, they still have some slop right out of the box. They do develop more slop over time much like the Align's.

For the same price, actually cheaper with the 3pack that outrage now offers, go with the 9180's on the Cylic. The outrage MKS rebranded are great. I transferred the 9180's and 9188 from my 700e with 90+ flights and when inspecting them there isn't a single bit of slop AT ALL! These servos were beat into submission quite a bit over the last 20 flights too.

You might also want to check the actual voltage coming out of your BEC pro.

If you have a mutimeter you can also do some load testing as well.

[Chris Sexton]

Originally Posted by vr360

Hey Chris,

Sorry to see you guys are having this issue. A friend of mine is running the Savox on cyclic and tail but he is using the slower Cyclics. No issues thus far.

Knowing that the Align DS servos are power hogs, and they are savox rebranded servos, This is no shock to me at all.

Although the speed and torque numbers of the Savox are impressive, they still have some slop right out of the box. They do develop more slop over time much like the Align's.

For the same price, actually cheaper with the 3pack that outrage now offers, go with the 9180's on the Cylic. The outrage MKS rebranded are great. I transferred the 9180's and 9188 from my 700e with 90+ flights and when inspecting them there isn't a single bit of slop AT ALL! These servos were beat into submission quite a bit over the last 20 flights too.

You might also want to check the actual voltage coming out of your BEC pro.

If you have a mutimeter you can also do some load testing as well.

Yeah I was originally going to put the Outrage 9180s on the cyclic, and I might yet go over to those. These Savox got some great reviews and were a bit cheaper at the time. For now I have my LHS soldering GURU soldering me up a custom RX harness long enough to reach from the nose to the back where my AR7200BX is setting. I will bench test again with RX pack and post my results.

[frito169]

You arent trying to power your servos through the beastx are you if so that is your issue and that would be the case with all hv servos.
when running hv servos through the beastx you need to get your +/- servo feeds from outside the beastx. They are not designed to pass through that much current. On my setup only the tail servo gets its power passed through the beastx, the cyclic Are wired directly to my 2s 7.4 V battery.

[vr360]

Originally Posted by frito169

You arent trying to power your servos through the beastx are you if so that is your issue and that would be the case with all hv servos.
when running hv servos through the beastx you need to get your +/- servo feeds from outside the beastx. They are not designed to pass through that much current. On my setup only the tail servo gets its power passed through the beastx, the cyclic Are wired directly to my 2s 7.4 V battery.

The BeastX powerbus should be pretty sufficient. I know for a fact the Vbar's internal powerbus is capable of handing HV with very high current draws with ZERO issues.

In this case, if Rob is having issues with the vbar as well, there is either an issue with the BEC pro or the servos have serious back EMF. My guess is the servos have serious back EMF/over current draw.

If you were bridging from a receiver to a beastx and using only one input for power into the receiver I would see an issue. The power bus, If I remember correctly, on the beastx just shares whatever power is imputed to the system and distributes it in parallel along all the channels.

[Chris Sexton]

Either way, Rob thought of that. He wired the power direct from the BEC still browned out. Seems RX pack is the way to go. Not a big deal, will help get my nose balanced with my light packs.

[frito169]

The beastx power bus was designed for passing power for 4hv servos but in many cases there is too much draw which can cause brownouts, beastsx recommends running power separate in this case. So anyone running hv servos should not run their leads directly to the beastx you need to bypass the beastx w/ your+/- feeds.

[Rob Cherry]

Originally Posted by frito169

The beastx power bus was designed for passing power for 4hv servos but in many cases there is too much draw which can cause brownouts, beastsx recommends running power separate in this case. So anyone running hv servos should not run their leads directly to the beastx you need to bypass the beastx w/ your+/- feeds.

That's all fine and dandy, but I did that already.

I really love these servos, I'm ok with the fact that they draw power fast and furious, it results in uber sick response time. I've never seen a servo with this much torque and speed. I've been using the original outrage servos in my X5, 0.05 speed, these seem just as fast or even faster. They do have a tad bit of slop, but less slop than the stock X7 swash has. I'm waiting on my ABEC 5 replacement bearing, that should tighten things up around the swash area.

I currently get 4 flights from a 1300 2S RX pack. 2 is optimal to keep the voltage higher. This is a fair trade off for lightning quick servos, which I need.

[Harrow]

You guys are talking about a 'brown-out', but the other two cyclic servos keep moving in the video while the third is stationary, so it can't be a 'brown-out' in the strict sense, otherwise all three cyclics would be affected the same. Something strange going on for sure though. What would make only one servo stop then come back? Wouldn't it have to be something going on internally to the servo? Since it comes back, is it some sort of internal circuit self protection?

[Chris Sexton]

well its a max amp issue. the other two are getting power, just not enough for the third. At least that is how I look at it.

If add pressure to the other side of the swash, the right servo would probably stop.

[akamullen]

From what Rob told me his servos would all just stop, it was a actual brownout.

[whittb]

Interesting test. I currently run 2 sets of these servos on my Whiplash and Furry 55. I have never had any stoppage issues running them with a 2S lipo straight into my full size V-bar unit. They are very fast and stronger than the torque servos. The slop is minimal and the replacement cost is good as well. I also run dual battery inputs into the V-bar units just to makes sure I do not over load the connectors.
I did however have one of the HV tail servos fail midway thru a flight. I was lucky that the tail stopped in a position that allowed me to auto without to much trouble. Had it stopped in another position, I would have been screwed. Amain hobby replaced the servo for me.

[akamullen]

Originally Posted by whittb

Interesting test. I currently run 2 sets of these servos on my Whiplash and Furry 55. I have never had any stoppage issues running them with a 2S lipo straight into my full size V-bar unit.

There is no problems when run with an RX pack. Its when tested on a BEC that the problems arise.