Max servo acceptable idle current
 

Hello
I have a CARF SU-30 that has 25 servos in it (!).
What would be an acceptable idle current draw (no controls being moved)?
Mine is drawing around 3.0 amps. I can go ahead and start trying to find out which servos may be binding, but it will take some effort to do so. Wondering if this current draw is unusual for these a plane with this many servos.
See chart.
https://cimg6.ibsrv.net/gimg/www.rcu...edf8fa8ac8.jpg
Spikes are not an issue as all current for the motors are flowing true the Royal.

3.0A is too high, I set up a CARF SU-27 with the slats and had 1.2A total sitting with flaps down (least load) my Mephisto has 16 servos and sits at 0.8A

Dave

Yeah you need to find and fix the problem for sure. If I was drawing over an amp just sitting there I’d be concerned.

Great info, how did you retrieve the amp draw graph. (I'm a Core user)

thanks

Am

I though this was excessive, but it’s good to have confirmation.
It was not too hard to isolate. I have three issues to solve:
1- Left elevon- two servos using the Royal servo matching are not well synchronized.
2- same with the right elevon
3- bad servo for the left main door

I will see how can I correct the elevons matching without removing the linkages. The servos are buried in the fuselage and can’t see how to easily get there.
Bought the plane used, so learning about it as I go along.

The graph comes from the Powerbox terminal software used to analyze the Core flights logs. check the Powerbox forums...

thanks

This is why I love Sbus servos, save so much head ache by matching right in the servo and can save a ton of channels

You may want to consider using a inline ammeter one servo at a time. This allows one to isolate the culprit(s) quickly. For ganged servos I start furthest from the fuse to set the surface where I want it. Then set the inner servo for minimum current. Kind of old school. But I believe in KISS and it works.

Good idea. I have hard ganged dual servos on my Airworld Hawk stabs. and for set up I put an ammeter, Hangar 9 , in EACH servo cable. With one servo disconnected I set the lead or Master servo for travel required. I then match the second servo as close as possible to match the leaders travel. I then hard connect the second servo. I then adjust the center and end points of servo 2 so that BOTH meter readings are identical and at their lowest value, ,ie not fighting each other. The currents are then checked and adjusted if neccessary at intermediate points to ensure exact matchings throughout travel.

It was dead easy with the Weatroncs servo curve adjustments, 4096 0points IIRC, so should be no problem with Core.

Another current reduction techniqueI have found useful is to spray all moving parts of the control circuit with silicone spray as used on plastic curtain rails, results can be quite amazing and costs nothing.

I have heard of a couple of Airworld Hawks being lost due stab. failure, I am fairly sure this was due to servo failure due mismatch resulting in servo burnout and lockup.

Perhaps another advantage of using dual ammeters and a radio capable of making tiny sdjustments is to adjust travel points of one servo until the current just starts to rise a tiny amount. This compensates for any gear lash and reduces the chance of control surface flutter developing.

Mine are still going strong after 12 years, touch wood !

Anyway, back to my morning coffee !

I agree with both above - an ammeter on the servos to match for reduced load and no fighting. It also helps you identify when a single servo is working too hard on a surface that is sticking, or driven against the stops.

Unfortunately, the Hanger 9 ammeter is no longer available and I haven't been able to find a suitable replacement that is as easy to connect. Anyone know of one?

Bob

I used this one....good for gang servos (up to 4)

https://cimg0.ibsrv.net/gimg/www.rcu...25ee6f12c.jpeg

Hi
When servos are matched at PB, there are only 3 points where they really match - Neutral and both end points. In my TD Hawk, I have 2 ganged servos in the stab, but I am connecting those to the PB to different channels and make the elevator function in a knob. Ithen match the servos in a PMix using 18 points in my 18MZ. Have done that in several planes with several hundreds of flights and no problems

Nuno