Hoody

The idea behind is really nice - I personally dislike the 4-guiding-rails design. In the version shown the segments need clamping support by cable ties, another drawback. May the guy improve his design further and solve the stability issue.

It makes me sad to hear about this. Condolences to you and your family.

The evoluation of math teaching: http://www.mathematische-basteleien.de/kartoffeln.htm#Versionen Oh, how I love this stuff. In the German section there is also this version: Integrierte Gesamtschule 1999: Ein Bauer verkauft einen Sack Kartoffeln für 50,-. Die Erzeugerkosten betragen 40,-. Der Gewinn beträgt 10,-. Unterstreiche das Wort "Kartoffeln" und diskutiere mit deinen 15 Mitschülern aus anderen Kulturkreisen darüber. Waffen sind dabei nicht erlaubt. I try my very best to translate it: Integrated comprehensive school 1999: A farmer sells a bag of potatoes for $50. His production costs are $40. His profit is $10. Underline the word "potatoes" and discuss with your 15 foreign class mates. Use of weapons is not allowed.

Same to Steph: Were the spirits free of lies?

Is this the orignal lyrics? I could swear he sings "your legend never did."

That's perfectly right.

Is it already time to give an answer? I hope I got it right myself: "Which direction will your neighbour give me to the village?" the wanderer asked one of the two men. The man immediately pointed to the right. The wanderer took the other way and arrived at the village later on. Why? If he asked the always-tell-the-truth-guy he will get the direction NOT leading to the village because the always-tell-lies-guy is his neighbour and since he always lies he would give the wrong way. If he asked the always-tell-lies-guy he will also get the direction NOT leading to the village because the always-tell-the-truth-guy is his neighbour and since he would give the right way the liar does his job and falsifies the result. Besides that we still do not know which of the two is the liar - in fact they keep their secret.

Oh, I think there is one effect that requires much more attention: It is the small/bigger pairs of magnetic balls. It is just a matter of 1/10 mm to adjust them so that they *just* do not attract the other pair but when they get a slight push then the magnetic force does the rest. And the most stunning effect then is that after they hit, the impulse is still high enough to tare them apart and push the next steel ball against the magnetic force. This is really fine art and "beyond ingenious". This guy is more than just playing with physics.

I think it is just a hype. There have been already marble run activities in the web (the so called "rolling ball web") but disappeared from the internet. Other pages are still available but those are rarely spread. But building runs yourself is so easy to everybody. You just need marbles (or balls) and can use everything you have in the house or garden or ... And you do not worry with the physics behind for the simpler runs.

Welcome to TanithElite The toy remembers me to what I had as a young boy - maybe I should go and get one of those for my kids.

I fully agree.

You are welcome.

" The Man in the Elevator" I already knew. "The Coal, Carrot and Scarf" I personally found obvious for itself but the remainder ... some are really funny when reading the solution. Let's try this one (maybe my writing is not as perfect as should be): Two men are sitting at a junction. It is known that one of them always tells lies, the other one always tells the truth. But nobody knows which of the two is the liar. One day a wanderer arrives at the junction. He wanted to head to the village but there was no sign to direct the proper way (left or right). Only the two guys to ask. The wanderer just took a short rest, then asked one of the two men exactly one question and from the answer he knew immediately which of the two ways leads to the village. Can you figure out which question the wanderer asked?

Please keep in mind that the glass marbles have tolerances in diameter and maybe you need to sort the bigger ones out or widen the hole a little bit.

Definitely. Friction of the pivot bearing is crucial here. Extremely lightweight constructions even could use paper for the tilting lever device. Dedicated to your bowl: the entrance needs also to be adjusted so that the ball will not hit it after its first round otherwise it looses much energy (velocity, height) and this reduces the spinning time. The walls of the bowl - their inclination - together with the banking formula give you an estimation on the necessary entry speed. The exit hole could get a sources of issues, too. Having it as small as possible gives the best effect until the ball disappears but causes blocking when two or more balls arrive simultanously. Here the timing of the balls arriving at the bowl needs to get adjusted well.

I see. My estimation gives roughly 0.67g per 8mm glas ball - oops, this is pretty few. 16mm glas balls roughly have 5.3 g which is pretty well enough for a switch. 8mm steel balls roughly give 2g each. Maybe you just build some switch models outside your box to find out which construction works well with 0.67g. You are really creative here.

It seems to be open to the public (meanwhile?). To leave a comment I just scrolled down to the end and there is the usual field for this purpose. I am using Firefox, a relatively new revision. But any other browser should work also. I forgot: Welcome Shellkat!

Still while enjoying your progress ... Why do you need the weight of steel balls? The switches?

Hi Bud, welcome aboard.

After you finished sawing you might file / rasp the edge to get it more smooth. I prefer to sandpaper my wood pieces with grain size (correct?) 80 to 240. Sandpaper or abrasive cloth is so wonderfully flexible for these jobs I prefer it over any file. If you need a precise flat edge, it might be an idea to pin the sandpaper on a tabletop (a small board will just also work) and then rub the piece of material against it as long as necessary. The sanded piece then gets as flat as a pancake. I am really curious about how your switches will look alike when you finished them. This you need to try out. There is not only the splitter itself, but also its tilt and how the marbles are coming in to it. The marbles themselves are neither perfectly balanced nor a perfect sphere so it really is not predictable if splitting will work well. On the other hand any not so perfect 1:1 ratio is also fine. Just give the rarely used track some more bonus points A practical use could be a device that is not capable of high throughput to be placed in the sparsely populated track. I nearly forgot: your downward coil is quite more complicated then it looks later on! The more your marbles descent, the faster they get. The faster they get, the more banking they need to stay on the track. Maybe it is not the kinks alone that throw out your marbles but also just the speed and the tiny radius?

Most of the spiders my kids call Thekla - thanks to "Biene Maja": https://en.wikipedia.org/wiki/Maya_the_Bee

Thekla is having her lunch.

Must be a Pinocchio wasp - with its looooooooong nose