Station Ripping Itself Apart

[Stickyhammy]

So I docked 4 full jumbo fuel cans to my station just fine. Unfortunately when I decouple my last fuel can deliver ship from the station the entire thing starts to wobble and eventually shakes itself apart. Sometimes a fuel can explodes. I took a video of it happening but until it uploads here is a screenshot of the station. Maybe someone can explain why its going crazy without seeing the video.

Here is the video:

https://www.youtube.com/watch?v=ZJ1iv7acO38&feature=youtu.be

Edited June 8, 2014 by Stickyhammy
Added Video

[Stickyhammy]

Update. I took the top ship with the fins back to Kerbin just fine. No wobble. Tried to take the fuel can delivery ship off next and the station ripped apart and exploded. Going to try to undock the extra fuel can as well as the ship. Also should note I had turned off SAS, stopped the Cupola modules torque and made sure the reaction wheel was offline. The station still went crazy.

[TechnicalK3rbal]

Any parts clipping? Also any mods?

[Claw]

Try shifting some of the fuel out of one of the orange tanks. I've seen several instances of quad orange tanks around a common node coming apart. Changing the mass distribution sometimes seems to fix it (or at least keeps it from wobbling itself apart).

As many times as I've seen this, I still can't figure out what is happening. I can see that you have Srs mounted to smaller structural components. Sometimes that makes the connection weaker, but I can't say that's causing a problem. Just make sure nothing is clipped anywhere near the ports or other connection points.

[Stickyhammy]

I just moved one orange can to the other end of a different orange can. Good thing the cans have docking clamps on both ends. Doesn't look as nice but it doesn't wobble either. Now I need to build an inter-planetary cruiser to collect that 10,000 fuel.

Still wondering if its just a bug that a station cant have 4 spokes.

[Stickyhammy]

I took my original station design into the launch bay to inspect it for errors. I don't know how this happened but I found the problem I think. On the right side spoke there is a docking clamp between the hub and the structural component. That is the side that makes it wobble. I will remove it and see if that fixes the station. I just dread trying to move that 10k fuel from one station to the other No way I can dock a new fixed station to the old station... Or can I.... If nothing else it would be interesting to try.

[Starwaster]

I just moved one orange can to the other end of a different orange can. Good thing the cans have docking clamps on both ends. Doesn't look as nice but it doesn't wobble either. Now I need to build an inter-planetary cruiser to collect that 10,000 fuel.

Still wondering if its just a bug that a station cant have 4 spokes.

No, they can have 4 spokes.

in fact if you download the GingerCorp station hubs on Curseforge you can have stations with six spokes. (eight total counting top/bottom). Or three.....

[Claw]

Yeah, that docking port will definitely contribute to the wobble.

Glad you got it sorted out.

[Stickyhammy]

I forgot something very important! All Kerbal Space Stations come standard with a claw module. I had it on the station in the first place just to make it 20% cooler. Turns out it is useful after all! I took up the new station design with 4 empty cans with struts to keep them from falling apart. It made for a very stable package without that wobble from the port. I took the cans off station A because I thought it wouldn't make orbit. Tried and failed three times. This time it made it with no issues. Just need to transfer the fuel over and DE-orbit the old station.

[davidpsummers]

I had wobble in my station. I turned off all SAS modules but one and it stopped.

I understand that when one has SAS modules trying to keep the station orientated you can get resonances. The station flexes a bit as they torque it, the SAS responds to the motion, which torques it again, so it flexes some more. It the new flexes are "in time" with the old, the torques just add to the flex faster than it can dissipate and bad things happen. The solution is to keep the SAS from being in resonance. You can change where you control the station from (which give is a different point to judge from) or the distribution of controlling modules (RSC and SAS, modules and capsules) until you break up the resonance. That is, IMO, what you did when you changed the design.

It is like the Tacoma Narrows Bridge. Small vibrations are the right frequency add up until it falls apart.