Lego: An attempt to distinguish soccer and basketballs by their rolling traits

I try to sort the two kinds of LEGO balls, soccer balls and basketballs, without a light sensor.
Rolling-down speeds of the balls depend on their groove features.
BGM:Petite
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My website
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[@PandemoniumMeltDown]

Yet again, proper scientific experimention yields results. Success!

[@emilellenius]

A few more slope segments and balls being released more frequently and this would be a great sorting machine.

[@thehaytch]

Great explanations. Also why did you start a new channel? The other one is going really well

[@michaelwade4835]

Maybe he didn't want this on his main channel because it technically isn't a full build, just an experiment

[@hugosantos5908]

I wonder what will happen if you had in mind the wear of the balls due to the intense use of them during the GBC tracks.

[@GimmeMyHandleBack]

This is amazing!

[@ArsMan064sLegoTechnicCreations]

Very interesting. Thank you

[@halutti]

面白い

[@ma2227yamana]

バスケボールがバラバラ過ぎて草

[@Sam_596]

What would be really interesting would be meta-statistics about how the shape of the distribution changes with the number of slopes.

[@ねこ-s5m]

すごく分かりやすかったです！！自由研究金賞しか取ったことなさそう

[@PlanetGBC]

very glad to see new experiments out there

[@letsbricktheworld4213]

Really impressive ! Great job !

[@BrotherCreamy]

Since the landing point of the soccer balls is almost never less than 70mm, but basketballs is sometimes less than 70mm, why not have multiple tracks one after the other, where there is a gap of say 60mm from the end of one track to a receptacle that feeds into the next track. so any balls that don't make it to the end are collected into one bin (for basketballs), and the rest are collected in a bin at the end (for soccer balls). This way, with a 10 track system, if a basketball has a 30% chance of having a

[@MrTrevortxeartxe]

You could also run the first experiment several times over to filter your results to a higher degree of accuracy. I'm sure you could get to 99% with just 3 or 4 runs. Perhaps a longer ramp or a further drop would do as well. I would have liked to see a fully analogue machine with no EV3 or digital mediation. Great work, either way!

[@jimstanley_49]

I think using the gate from the EV3 setup might also clean up the results of the first experiment. Tiny differences in how he releases the balls may have an impact on their speed/fall distance.

[@ゆうがた-i9e]

GBCの基礎であろう、支柱の組み方と必要なパーツがわかりやすくてとても参考になりましたｗ すごいメカももちろん見たいんですけど、基礎中の基礎がなかなか見当たらなくてありがたいです。

[@dizekat]

Lego roll-spectroscopy and ball isotope separation... I'd never have thought that up. I wonder if you can get to high separation by dividing into 3 streams and recycling the middle stream, or if some variation in the balls themselves would prevent it.

[@nathangrange8473]

Need more of these please. Esp. building techniques and why you'd do x and when you'd do z etc...

[@KnightIA]

Turn on subtitles to see some text!

[@jero37]

I noticed a behavior of the basketball with its indentations perpendicular to the axis of rotation as it sped up over a longer track moved toward an orientation with the lines parallel to the axis, I wonder how long a track would need to be for all basketballs to reach that orientation.

[@rizalardiansyah4486]

This sorting system can even be upgraded to use mechanical timers that is properly calibrated. Genius!

[@steelyray]

I suspect the differences lie in the internal molding quality of the balls. The basketballs seem to vary more, suggesting that some had their first moment of inertia off-axis from the rolling direction on some slopes.

[@mescalinum]

Very ingenious as always. But I thought that you don’t need to wait until the first ball has arrived to the end before sending the second ball. You only need to wait for the worst-case scenario (e.g. sending the slowest ball, then sending the fastest ball) time. It is a bit more tricky to figure out how the lane can be occupied by how many balls and how to queue the commands at the end-of-lane switch. Would love to see that in action.

[@dinoscheidt]

Nice example to explain stochastic / statistics to students 🤔

[@佐野美菜子]

B

[@trancongnguyen1252]

very nice approach

[@lumirbaca1831]

Super.

[@岡村隆史-x2y]

ニコニコの動画も全部ようつべにのせた方がいいと思う

[@jimstanley_49]

It looks like the basketballs have a hole in them parallel to the grooves, but the soccer balls are plugged. Assuming that both balls have a hole passing through the center and the soccer balls have the ends plugged (but not filled through), I can see the cause of the difference: inertia. Inertia is an object's resistance to acceleration and is directly related to its mass: more mass, more inertia. A _spinning_ object's _rotational_ inertia is related to how far the center of mass along a given radius is from the center of rotation. For example, a solid flywheel with uniform weight distribution (cm = r/2) has less inertia than a "spoked" flywheel with the same mass, but most of it concentrated around the outside (cm = 4r/5.) Soccer balls with the same hole through the middle, but with plugs at both ends, will have higher inertia than a basketball when the hole is parallel to the rail. (If the plugs are not exactly equal, being unbalanced could be enough to overshadow the advantage.) When the hole is perpendicular to the track, both balls have almost precisely the same distribution of mass, with the plugs (being so close to the center of rotation) contributing only a tiny amount of influence. This is why some basketballs were fast enough to finish in the middle of the soccer ball distribution on a straight track. Having more inertia means the ball will travel at a more consistent speed, despite irregularities in the track. If the track has turns in it, the soccer balls will have more consistent speed overall than the basketballs, but the basketballs will also spend more time in an advantageous orientation over several turns than on a straight track of the same length. Having multiple chances to reorient with the grooves perpendicular to the track evens out the basketball distribution.

[@msk6003]

how about launch multiple balls at once?

[@AquaAdAstra]

Different content I’d assume.