843 servos position defines neutral - why centering springs on pump lever?

[chili81]

After some fiddling I understand pretty well how my 843's servo controlled steering works and I've got creep and centering springs all adjusted pretty well.

The one thing that befuddles me is that there is a centering spring mechanism connected to the main pump arm/lever (the 'throttle' arm). I dont understand what this does...

The position of the lever is dictated by the servo piston position. Once you move the servo to a position, the lever is going to stay in that position. It will only return to neutral when servo returns to the neutral position you adjusted it for. The spring is not going to move the servo or the lever if the servo doesn't want it to.

Does this make sense? Hard to describe if you aren't already familiar with the setup.

The only thing I can think of is that the server isn't a simple standard simple hydraulic piston and simple standard control valve spool that I'm used to (oil goes in one side - it moves one way.... spool in neutral, it stays fixed, oil goes in other side, it moves back). Maybe this is a different type?

Anyone understand what i'm talking about and how it works?

 

[chili81]

In case anyone ever is confused as I was - it's pretty simple - the servo isn't a typical spool like you have on lift or curl where it locks into place when you release. It moves when you push one way or another, but then the cylinder is essentially free to move either way when the spool is in the neutral position. If it was a basic standard valve it wouldn't work - that's why it isn't!