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Forum - I'm thinking of running my second youth GBC class in ten years, but have some questions

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Overview > Great Ball Contraption > Great Ball Contraption Discussion > I'm thinking of running my second youth GBC class in ten years, but have some questions Write a reply

The first class was amazing. The kids learned far more than even I anticipated. Almost all of those students are now engineers and computer scientists.

The first time we used Zamor spheres, which turned out to be problematic. The size is not ideal for a GBC. This time I'd like to use the same balls used in adult collaborations, but I'm having trouble sourcing them. I see them at Bricklink, but they are expensive. We want to do a 12-module loop, which would require a fair number of balls. I'm thinking 120 minimum. Does that sound about right? Any idea where we can get that many balls at a reasonable price? The class is starting to price itself out of existence.


Posted by 2604:2d80:8035:803c:51aa:fe6d:48c5:7c14 on 30 April 2016 at 19:42.

The biggest problem with the Zamor spheres is not their size rather, it's that divot at one pole. In both cases, it's certainly possible to engineer around those limitations - you make your channels a bit wider, and your slopes a bit steeper.

Alternatively, you would probably get away with half your proposed number of balls. It depends a bit on the size of the modules, but 10 balls per module is a rather densely populated Contraption. So long as all modules have at least a few balls on them, it's just as interesting.

Hope that helps. Owen.

Posted by Captainowie on 1 May 2016 at 01:24.

Thanks, Owen, that does help.  :)

The divot didn't give us much trouble, but the Zamor spheres turned out to be an awkward size for many mechanisms. They are just a bit too big to fit smoothly through a 2-stud opening, but rattle around loose in 3-stud openings causing an inordinate number of jams and drops. The Zamor spheres sit too high on 2-pin supports, often falling off, making tread lifts unreliable. When we had a lot of trouble, I looked more carefully at GBC videos and realized how many modules depend on that snug 2-stud spacing. It's surprising how much difference a slight change in diameter makes. I didn't know that when I decided Zamor spheres were close enough in size to soccer balls.

That isn't to say it can't be done. We did it 10 years ago, but it was a real challenge for the 12-17yos. Since this group might be a bit younger, I'd like to remove that particular challenge if possible.

Halving the number of balls would help. A lot of balls made a very exciting and fascinating GBC loop, but we could compromise on that for the sake of cost.

Posted by on 1 May 2016 at 03:01.

I was certainly surprised at how much of a difference the change in diameter made! I found that using these were great for making chain lifts. Two examples from my past include and - but I agree that Zamors are inferior to the standard balls, and if you can remove one source of frustration then you probably should.

I've found that the more balls on a Contraption, the higher the spill rate, so while it might be exciting and fascinating for a while, the number of balls naturally comes down to something that's more maintainable. That number is different for each Contraption, and usually lower than I initially expect.

Good luck, and let us know how you go.


Posted by Captainowie on 2 May 2016 at 07:46.

I'd agree that you need less than 120 balls for a 12 module loop, but there is a large amount of dependence on the modules. Pumps need balls to 'prime' them, and effectively remove those balls from the loop. But for basic testing, I'd want at least 5 balls per participant, just so everyone can be testing at once. Ideally, everyone gets 30 and can test for surges, but that is a lot of balls.

Do you have a local LUG that can help?

Posted by on 9 May 2016 at 19:44.