Cubic Octagonal Struts = catastrophe.

[Vanamonde]

Fellow players, allow me to give you a word of advice. Do not use the cubic octagonal struts on the same vessel that has any docking rings.

For ANYTHING.

EVER.

I built a small rover that uses them for suspension. This is what the rover should look like.

I flew about a dozen test flights to Mun and Minmus without a hint of trouble of any kind. But as I docked a couple of them to my interplanetary ship, I noticed that the wheels would jiggle suddenly when I came out of warp. That was troubling, but no harm was done, so I flew the ship to Tylo and set an orbit. Upon exiting warp in Tylo orbit, the rovers tore themselves to pieces. As you can see in this pic, those delightful little cubic struts jerked so violently that they actually ripped themselves off of the rover core and went flying off into space.

I spent about 6 hours this evening flying these things to Tylo, but there was nothing left to do but discard the rovers that were the primary reason for the mission.

As others have discovered, having cubic octagonal struts in an assembly that also includes docking rings can cause strange rotations that have caused vehicles to flip while sitting on the surfaces of worlds, but apparently, it can happen while in space as well, and on small vessels, it is not just a nuisance but catastrophically violent.

Right now I am keenly resenting that this forum does not allow swearing.

[thederper121]

Not sure if this thread belongs in KSP fan works.

[Vanamonde]

Yeah, me either. I posted it in general. WTF?

[sal_vager]

I had much the same occur with tiny lamp addon for my station, seriously it was just a mini port, an octo strut, another mini port and a light on the side.

Thing nearly tore my station apart with the rotation, in a panic had to find and click the port to undock it, flinging my delivery craft dozens of meters away.

Rebuilt the lamp with an oscar-B fuel tank instead, and it was fine.

Both the octo and the cubic are reported to have this issue, and it's usually when a port is attached directly to them.

[Themohawkninja]

Can't say I've had any problems with octo struts.

[Vanamonde]

Can't say I've had any problems with octo struts.

Kateteochi first brought my attention to the problem, and as far as he could tell, it ONLY occurs when you combine those particular strut pieces with docking rings in the same construction. My experience bears this out.

[Landge]

I've had that problem using the covered docking port attached to a cubit strut attached to the side of a tank. That was before Squad added the radial attachment part (I don't recall the name). My spaceplane went into convulsions and ripped it and the station apart when I docked to my space station.

[DChurchill]

Can't say I've had any problems with octo struts.

I've had some wierdness based on certain configurations. Others, not so much.

Building a non-powered lander chassis for a rover for Duna. Basically an X with lander legs on the ends and a Mk16 chute in the center, rover on a stack separator underneath. I put the smaller chutes on the 4 corners of the X over each leg and it's fine until the lander touches down and I blow the stack separator. The lander then proceeds to shake itself apart and explodes. I redesign it a little so that it's basically the same, except that I put a "crossbar" of cubics through the center and mount chutes on the ends of those. Works fine. Except that I'm down 2 chutes, which I hope won't be a problem when I come down through Duna's atmosphere. If the chutes don't get it slow enough, it's going to be a smoking hole.

If I had it to do over again, which honestly I do but I want to try this, I wouldn't use cubics at all.

[automcdonough]

my lightweight wide wheelbase strategy and your findings are at odds. I'm uncomfortable with this.

(i have not had issues though. except for a time-warp krakken visit once)

[Sirrobert]

Wouldn't that tiny little rover thing only go in circles with that wheel setup?

[Vanamonde]

Wouldn't that tiny little rover thing only go in circles with that wheel setup?

Nope. They all point front/back.

my lightweight wide wheelbase strategy and your findings are at odds

Did you dock it to anything after launch? Not undock it from an assembly from the VAB, but dock it to something else after launch?

[Sirrobert]

Nope. They all point front/back.

Did you dock it to anything after launch? Not undock it from an assembly from the VAB, but dock it to something else after launch?

My bad, only looked at it quickly

[Eric S]

As I understand it, the problem comes from when the ship has to reorganize the parts tree. This happens to one of the two craft whenever you dock two craft, they become a single parts tree. Parts of the craft that gets subsumed that are between the real craft root and the docking port wind up having to change their parent part, and some parts, notably the cubic octagonal strut have problems with this, for some reason.

[CCKinnison]

so - struts BETWEEN the base modue of the unit, and the port, would be the problem? Hmm. I may have to test this by putting the struts on the other side of the starting piece.

[Vanamonde]

The struts were not between the core parts of the docked ships in the mishap I posted. Incidentally, when I landed another one of that mission's rovers, I found that it had a broken wheel. I suspect it slammed into another part during that spastic jerking. But the result is, 3 of the 4 rovers on this voyage were wasted by the cubic strut problem. The really aggravating thing is that if I had discovered it before undocking the rover, I could have sent a crewman out to fix the flipping thing.