Tri-Coupler to single

[KerbMav]

There seems to be no way to make this work ... only one engine will stay attached, the other two will rip loose and float away.

Edited September 6, 2013 by KerbMav

[numerobis]

People have had success docking two tricouplers together in space, but indeed, in the VAB, you get one attachment and two loose parts.

[rryy]

When the fairings jettison from the engines, they crash into the others which cause some to rip loose. Try rotating them with Shift+Q and E so when the fairings decouple, they don't crash into the other engines.

[Johnno]

It depends how you build it. You'll only have one 'parent' attachment, meaning you can have a tricoupler that splits into three, but you can't connect a tricoupler to three things at once, only one of them will be attached. With enough struts and a bit of planning you can get them to stay together, but it depends entirely on what you're trying to do.

[Sirrobert]

Did you build it from the tricoupler up, or with the tricoupler as last part?

If the coupler was the last part, than only 1 engine IS connected, and the other 2 not

[Afross]

im pretty sure it is impossible to add parts onto couplers that go from a higher number to a lower one in the VAB. i really wish this would change at some point in the future because it restricts what you can build. unfortunately you might just have to find another way to build that rocket so it doesn't have any coupled stages.

[DavidPolak]

Actually worked for me

(http://image.noelshack.com/fichiers/2013/26/1372620445-screenshot9.png ; http://image.noelshack.com/fichiers/2013/26/1372620448-screenshot12.png)

[KerbMav]

Did you build it from the tricoupler up, or with the tricoupler as last part?

If the coupler was the last part, than only 1 engine IS connected, and the other 2 not

I build from the payload down, but i first attached the tricoupler so I could equip it with the three docking clamps and then flipped it around to attach at least one clamp - hope was that on the launch pad the other two would magnetically attach themselves - flight went well until separation of the stage under the three nuke-drives.

When the fairings jettison from the engines, they crash into the others which cause some to rip loose. Try rotating them with Shift+Q and E so when the fairings decouple, they don't crash into the other engines.

I tried that, the "split" facing outwards - not outwards enough?

[Vanamonde]

A while back, some very clever person figured out a way around this problem. (Sorry I don't remember who it was; the post was wiped out in the forum massacre.) Build the lower tri-coupler assembly like this,

so that each piece only has the 1 parent part that Unity requires, then rotate it and save the design before going to the launch pad. When the software assembles the ship on the pad, all 3 pairs of docking rings will link quite solidly when physics kicks in. I've used this and it works pretty well.

[HoY]

Look at the first video in my signature and you'll see the same as was mentioned above, except in 1600p video lol.

If you look at the playlist on my YouTube channel you'll also see the method used for switching from 3 engines down to a single engine under them using a similar process. It's not in the tutorial thread because it was just a quick reply type thing to a similar question that you just asked

Edit2. I just took a closer look at your picture, just make sure you rotate the engines so that all of the fairings will jettison out sideways, not radially inwards and outwards. If they do that the 3 halves that go in will most likely continue to sheer off the engines. The way around this problem is not to actually put decouples under these engines it's to have the decoupled in between them mounted to the tank above them. This usually means using engine clustering instead of the tri-coupler

Edited June 30, 2013 by HoY