totm ssptember 2020 The Rubiks Cube (Kube?) Project

[dnbattley]

For your predilection:

 

[cubinator]

Congratulations! As a fellow KSP Rubik's Cube engineer, I'd like to see what's inside. Does it use any mods? How many parts is it?

Most importantly,

did you manage to do it without using docking ports?

Edited August 6, 2020 by cubinator

[dnbattley]

7 hours ago, cubinator said:

Congratulations! As a fellow KSP Rubik's Cube engineer, I'd like to see what's inside. Does it use any mods? How many parts is it?

Most importantly,

did you manage to do it without using docking ports?

Thanks! And sure thing: I've posted the craft file on Kerbalx https://kerbalx.com/dnbattley/Rubiks-Kube, if you want to take a look. It is fully stock (plus DLC, naturally). The version there is slightly upgraded from this with control added via action groups.

In terms of operation, it abuses the self interaction toggle functionality to make this a single craft (no docking ports/decouplers) using tiny servos (the most "cubic" pieces in the game) as the fulcrum, which rotate each piece (these in turn are each attached via three unmotorised rotors to give full 3-axis movement), with further guide parts fixed to the core, and also to each side servo, becoming "active" in turn depending on whether the piece is moving or not moving at the time.

I originally tried making a version based on the real design of a cube, but this approach had significant benefits in terms of part count and controllability.

Edited August 7, 2020 by dnbattley
clarification

[vyznev]

12 hours ago, dnbattley said:

In terms of operation, it abuses the self interaction toggle functionality to make this a single craft (no docking ports/decouplers) using tiny servos (the most "cubic" pieces in the game) as the fulcrum, which rotate each piece (these in turn are each attached via three unmotorised rotors to give full 3-axis movement), with further guide parts fixed to the core, and also to each side servo, becoming "active" in turn depending on whether the piece is moving or not moving at the time.

That's really neat! After downloading the craft and studying a bit, I think I mostly get how it works. The one thing I'm still puzzled about is how you seem to have managed to keep the rotors that the cubes attach to from getting gimbal locked. I tried looking inside, but all I see is an octagonal strut crammed full of rotors clipped into each other, and trying to pull them apart wasn't very helpful either.

Sometimes it would be really nice to have some way of selecting a part in the editor and having it highlight (or even switch to) that part's parent. Just saying…

[dnbattley]

3 hours ago, vyznev said:

<snip>...an octagonal strut crammed full of rotors...

Thank you! I put the model together in as modular a way as I could, which was necessary for the times the KAL bugs out and forgets all its instructions... The way to dissect it is, 1: offset the large servos outward, 2: move the octagonal piece upwards (this exposes the "fixed" supports that the sides rest on when static), and then 3: look for the side of the motors that selects all three axes and offset this motor - this will separate out one of the moveable cubes (either edge or face), and all sets of 3 axes motors were deliberately oriented the same way. Provided you keep the offset on grid mode everything can be offset back into position, and it was this precision that allowed the gimbals to work.

I now have a save game crammed with subassemblies for all of these parts I put together...

[James Kerman]

Congratulations @dnbattley, this engineering masterpiece has been awarded thread of the month.

[dnbattley]

16 minutes ago, James Kerman said:

Congratulations @dnbattley, this engineering masterpiece has been awarded thread of the month.

Thank you very much: I'm honoured!

[sturmhauke]

actual photo of @dnbattley posing in front of my brain:

[dnbattley]

47 minutes ago, sturmhauke said:

actual photo of @dnbattley posing in front of my brain:

Haha: thanks!

With all this very kind recognition, I was reminded to upload some unshared footage* I had lying around of the final version of the cube being used:

* I think I'd used some of it for an animated gif on the reddit forum, but never got around to properly arranging it.