Why are Vectors so wobbly?

[Foxster]

I loved the new Vector when we first got it but I am losing enthusiasm for it. It simply makes rockets wobble so much!

Now, I know it has a lot of gimbal but setting the max gimbal so that it has the same amount as, say, the Skipper or Mainsail does not fix things. The Vector still flexes about too much. This seemingly being exaggerated if working alongside some aero attitude control.  

Could it be that the Vector has a faster switching between its max gimbal lock...or something else?

 

[Plusck]

Perhaps it is the gimbal speed (I generally turn down max gimbal to about 10%, which is still hard for SAS to control, but haven't really noticed whether it then goes to max gimbal in 10% of the time for full lock or not...).

In the .cfg file, the Vector has a value "gimbalResponseSpeed = 8" which doesn't appear at all in the Skipper' file.

Also it is a 1.25 part, so the joint is weaker than a 2.5m part. And it is generally attached to a 1.25m stack, which again adds weaker joints above it. This certanly contributes to wobble.

I'm not sure how mass is modelled on moving parts, but could it be that the game models the mass of the engine being thrown from side to side?

There is another value in the .cfg files that I don't understand: for the Skipper it is "gimbalTransformName = thrustTransform" and for the Vector it is "gimbalTransformName = Nozzle". The Rhino has the same as the Vector, while the Swivel has the same as the Skipper...

[Rocket In My Pocket]

Try using Claw's stock bug fixes: http://forum.kerbalspaceprogram.com/index.php?/topic/87737-ksp-v105-stock-bug-fix-modules-release-v105a3-27-dec-15/

It adds tweakable gimbal speed and such. (As well as lots of other great fixes.)

Quote

+ ModuleGimbalPlus (Plus) (27 Dec 15) - (STATUS: Minor Update) - Description: Currently contains the following Plus options (no StockFixes required).
     - (Plus) Activates gimbaling speed (gimbal speed is ENABLED by default, when ModuleGimbalPlus is active).
     - (Plus) Adds gimbal speed tweakable
     - (Plus) Adds toggle to enable gimbal response speed

 

Edited January 10, 2016 by Rocket In My Pocket

[Snark]

The problem with the Vector is that not only does it have that huge gimbal range, but it has a gimbal speed, (as previous posters have pointed out), unlike pretty much every other engine in the game.  The other engines have gimbal speed disabled, so they all gimbal instantly; the Vector doesn't.

There's nothing wrong with slow-speed gimbaling per se... except that the SAS stability code in KSP isn't equipped to handle it, so the thing goes berzerk.

You can easily mod the engine to stop using gimbal speed, if you like (assuming you have ModuleManager installed, which you almost certainly do if you're running any mods at all).  Just create a .cfg file (can have any name you like) somewhere in the GameData folder that has the following content:

@PART[SSME]
{
	@MODULE[ModuleGimbal]
	{
		@useGimbalResponseSpeed = false
	}
}

In the same fashion, you can insert "@gimbalRange = 2" right next to @useGimbalResoponseSpeed to change the default gimbal amount to 2 degrees (or whatever number you like).

 

Alternatively, if you'd like to play around with a modded Vector that has been repurposed as a rocket engine rather than a shuttle engine (gimbal changes, and others), you could try this mod. 

[Plusck]

I found this thread: http://forum.kerbalspaceprogram.com/index.php?/topic/46553-engine-gimbal-reaction-speed/

From that, and particularly from Texel's second post, the "gimbalResponseSpeed = 8" means it should be quite fast to gimbal (but for SAS it obviously isn't fast enough).

Also from that same post, gimbalTransformName refers to the part that actually is seen to move: "thrustTransform" means it is just the exhaust cone that moves, "Nozzle" is presumably a sub-part of the engine (since I don't see the whole of the Rhino moving to show thrust vectoring). I'd guess this is irrelevant to the question here and is visual only.

Edited January 10, 2016 by Plusck