Hi Twisty Puzzles fans,

Barbell Cube is a challenge for intellectual weight lifters. This puzzle has two Rubik's Cubes that are connected through an intricate gear system. If you turn a face on one cube, a face at the other cube will follow. However, the connections between the two cubes have no symmetry. This makes solving this puzzle extremely difficult. Let's say Rubik's Cube squared. Unfortunately, the prototype has failed.

A lot of work has gone into the design of the gear train. The connecting rod has seven layers in total. The inner layer connects the two spherical cores. The outer layer connects the two opposite white faces of the two cubes. The other five layers have gears to connect specific faces. For logistical reasons, I dyed the five sets of gears red, orange, yellow, green and blue, matching with the colors of the faces. This way, I could keep track which gear drives which face.

The gears are so-called "double chevron gears", as invented by car maker Andre Citroën. This gear design has the advantage that the gears do not slip sideways and that they can handle a lot of force. They also generate less noise than regular spur gears because of their continuous meshing.

The gear trains work really well. They never jam or touch adjacent gears.

The big problem of the prototype is friction. It is well known that 3D-printed nylon creates much more friction than e.g. mass-produced injection-molded ABS. In this prototype the friction is too much. At each face, the center pieces is connected to a gear with a square pin-hole connection. If I force a rotation, then the square hole in the gear deforms and the connection is lost.

There are two direction in which these problems could be approached.

1) The gear train could be made of 3D-printed steel.
2) The Rubik's Cubes could be made of 3D-printed polished nylon SLS.

The steel would result in a much stronger gear train. The polished nylon SLS is a technology that Shapeways is working on, based on their White Strong and Flexible material, that should have very smooth surfaces. There is a lot of cost involved in this, so I am opening this project up for sponsors. Please contact me if you are willing and able to risk to $2000 for the potential to own the first working prototype of this design.

Watch the YouTube video.
See the puzzle in my Shapeways Shop.
Read more at the Shapeways Forum.
Check out the photos below.

Enjoy!

Oskar

Nice concept Oskar, although it's a shame it didn't work. The gearing mechanism looks extremely complex however, and I must complement you with the ingenious mechanism. Though this puzzle didn't work, don't get disheartened.

My god Oskar, can your puzzles get any more complicated? Just because some suggests an idea, you don't have to go and make it I suggest a network of 500 different twisty puzzles across the whole world which are interconnected by quantum entanglement so that when one turns a random number of the others do as well.

BTW, a small typo in your post, the name is Citroën.

Oh yes, great idea. And don't forget to read my signature

That's I think, less complicated than the 17x17 at least.

This is great idea, but it's a shame it didn't work.

On a different note, how much does it weigh?

We need a more robust method to make this work:

Five minute warm up spin (30km/h) on the exercise bike.
Ten sets of 20 sit-ups.
Use the Barbell Cube and do 25 repeats (alternating side, front, and overhead).
Half an hour swimming to tone, relax and line the muscles.

Optional: Five sets of 10 pull-ups.

*Then* this puzzle will work 100%, guaranteed!




Pantazis


PS. On a serious note, this structure is building now a connection
between puzzle designers and... magicians!

That shaft is longer than it needs to be (all adds friction), does it need to be so long? Also maybe thin metal bearings inside the shafts to create a thin gap and reduce friction?

Yes, the material is too rough: if the cubies were a light smooth material like the GuHong it would turn the second one easily, but the problem might be the first one buckling then.

You want to link 4 in a circuit, don't you! I read your mind.

Good luck with this,
Burgo.

The friction is in the cubes, not the gear train or shaft.At each side, there are four gears in a circuit. So per color there are eight gears.

Oskar

Awesome! Strange how one cube works, but the other one is unable to affect the first.

I hope you can find a way to overcome the friction, and I am VERY excited to hear about POLISHED WSF! That will open the door for many new concepts, if it can keep the precision of normal WSF

Good luck with the next prototype, I hope you can find a sponsor...

Masterpiece!!!

Sadly in the database there already is a puzzle called Barbell Cube.
When the time comes I will solve this by calling it as "Oskars Barbell Cube"

Anyway: Awesome concept.

I just realised that this Barbell Cube could be the basis for this evil puzzle proposed back in 2005.
The question is whether an external mechanism could be more efficient (in terms of friction)
than an internal.






Pantazis

Have you tried lubricating the mechanisms? A little silicone oil or grease might help solve these friction problems.

I dont think so. The 3d printed parts have texture on them and as you see after he lubed the 17x17, it did not improve it a lot (my opinion) He might need to use molds(I dont know) but I doubt it would work.

On my puzzles using WSF, I have sanded, primed, sanded and then and spray painted them using gloss black, which results in a nice shiny finish. I don't know how well the paint would stand up to the rubbing, but if you wanted to see if you could make the prototype work, then maybe this is a possibility.

To me, this begs the questions... Is there a mass-produced injection-molded ABS 3x3x3 that you could adapt your mech to? Steal the corners and edges off of that and just print the other parts. There are so many different 3x3x3's out there I think there is a chance you might find something that would work.

This 3x3x3 has room for a ball core. It might work.

Just an idea,
Carl

I love it! I hope you will try again and get it to work...

Then you could try this same mechanism in my Molecube.