I designed a replacement core for the QJ Domino that fixes the problem of the spring resisting rotations or unscrewing itself. It costs $12 for white and black

http://www.shapeways.com/model/576848/8 ... 38de835470

I made it so that the center the spring normally comes out of rotates around a piece that turns with the other center. So the screw itself no longer rotates, but you can still tension it.

cool i might get one

Is this guaranteed to work with the QJ 2x3x3? Because if it is, I will definitely buy it. Only problem is it costs more than it would cost to buy a new 2x3x3.

Actually this is guaranteed not to work... just by looking at the shapeways model you can see the design will not only not work, but also won't be able to be printed by shapeways.

@MrShanko: you should probably stop trying to have people prototype your puzzles for you, especially when it is clear they will not work. This is not the first time. Try contacting one of the forum's designers and make him check your files etc. Also, don't use google sketchup, it's a terrible option ^^

You make me very sad, but I know that you are right.

@mrshanko: Listen to Greg, he knows what he is taking about.

Couldn't you just use a small washer between the spring and the plastic?

I'm missing something. I don't have a QJ Domino so maybe that's it. But for my own education, may I ask why this won't work? If Shapeways couldn't print it, I would think that would have been caught when he uploaded the model. Just feel like I'm missing soemthing obvious and not sure what it is.

And I certainly agree with the advice of prototyping your puzzles before you offer them for sale. I do that with all of mine as I'm never sure how well they'll work till I've tested them.

Thanks,
Carl

It's very hard to say from the pictures on Shapeways that this wouldn't work and it's definitely a bit careless to make that claim without backing it up. Though, one potential problem is seen here:The axle is about the same size as the square piece it fits in to. This tells me that the walls near where the circle is tangent to the square must be very, very thin (one pixel is approximately 0.25mm). Shapeways will not print anything with <0.7mm walls and it's not likely this will pass that test. And even if it does, there likely isn't enough tolerance for them to fit together.
There is no rule against offering something that's not been prototyped (though I don't think it's a very good idea) and it's up to the buyers to decide what they will buy and not.

But then, isn't it easier to simply use a bit of glue or Loctite to prevent the screw from unscrewing?

I was saying it doesnt work because of the 0.7mm walls. I don't know why I didn't say it ?

I was really just looking for a replacement core for my QJ 2x3x3, and I was too lazy to make one on Inventor. I had lost my core when I was playing with it one day in public and it had unscrewed and parts went everywhere. I basically ran around and picked all the pieces up but must have left the core.

Could you tell me why? I've been using it for several years and it's very precise in my opinion.

Sure, SketchUp is good for a lot of things and is very intuitive to use. Designing twisty puzzles may not be one of them. It is almost universally agreed that parametric software like SolidWorks is best and indeed, nearly all 3D printed puzzles today are designed in it.
SketchUp makes it very difficult to play around with your designs and find the right proportions for the mechanism, it does not enable you to properly fillet pieces, does not make it easy to precisely specify and check measurements... And also it tends to produce files that have problems like inverted normals, non-manifoldness,...
Once you have tried real CAD software like SolidWorks there's no turning back. I have tried quite a few programs (SketchUp and AutoCAD) myself before coming to that conclusion.

With all due respect, you have a lot of designs listed on your Shapeways shop but you have never actually printed anything so we are clueless as to any of them actually work the way you intended. And it does like quite a few of them would have problems.
Once you need to take in to account filleting, tolerances, wall thicknesses,... SketchUp becomes very difficult to use. Even using non-orthogonal geometry like Dodecahedrons and the like is tricky.

But, use what works for you! Gus has been making some pretty nice puzzles using SketchUp lately.

Sure there's a lot of things that you have to be careful with in SketchUp, but there's not one thing you mentioned that I haven't learned to deal with. I've updated the model and should be uploading very shortly.

Re: SketchUp vs the rest.

SketchUp is easy to learn and good for certain things (like being free). Its OK for designing add-ons for existing puzzles, but doing fillets and shells can be a problem. I've only done one complete puzzle (Hexaminx) and that was a real pain. Making shapes manifold can be a problem, but once you know a few tricks it is not so bad.

Parametric 3D software like Solidworks and Inventor (I've use both through work) has a very steep learning curve, but pays dividends in the long term. Being able to link critical dimensions, create formulae in a spreadsheet, undo actions and re-do them in a different order are essential if you are designing a brand new puzzle. The shells method of puzzle design would be impossible without this sort of software.

That being said, because of the price of SW and IV, I am stuck with SU for the time being