Dual servos on Y cable redundancy issues

Hardware
1

Good day all.

I’m busy with a redundant setup with a APM plane using two servos on each aileron and elevator.
The idea is that if one servo burns out, the other one is still functional.

So far what I tried was putting two servos on a Y cable and adding a fuse on the “+” line (on each servo wire) and I’ve tried it on the “-” line as well.
I’ve got a already blown out servo to test this.

Connecting the working servo first to a servo tester on a Y cable to make sure it works, its set on auto (continuously moving) Then another working servo is added on the other end of the Y cable and it’s also working.
Then I remove one working servo and add the burnt servo.
The conclusion is that the fuse blows out (does its job) but at the same time, the other working servo also stops working. When I disconnect the blown servo, the working servo works again.

I’m using Hitec HS-65MG servos to test with 3A fuse.
Note that each servo will be working on its own surface (independant)

Is there a workaround? I’m not keen on adding a power box of some sort as I’d like to keep the system as light as possible.

Thanks in advance

2

Interesting.
As to why the good servo stops working, the only reason I can see is that the bad servo shorts out the signal, else I dont see why it should stop working.

It is possible to mechanically mix 2 servos, for example using pulley wheels so each servo can move the output. The problem is that a servo may stick in a non central position. In that case the other servo needs to compensate.
Therefore the position of the output must be known.

There are redundant servos available, but you will probably pay a lot:

http://www.volz-servos.com/English/Redundant/

http://www.pegasus-actuators.com/products/redundant-actuators/