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The Hui Stick

Jun 05, 2021
The eleventh Curiosity Box is now shipping. I'm talking about ferrofluid, an Archimedean device. I can't give away all the items, but you will also receive one of these if you subscribe. This is a hui

stick

. Also known as a gee-haw whammy mulch. Also known as the Ouija windmill. Oh yeah, it's creepy. It's just a small rubbing

stick

and propeller stick that has a propeller on one end and notches on one side. Now when you rub the lever along the notches, the propeller lever will vibrate and the propeller will spin, but the direction it spins will obey your command.
the hui stick
All you have to do is say the magic word. Hui. Hui! Hui! Hui? WHO? MY? How does it work? Well, that's what we're going to talk about today at Michael's Toys. To see how the Hui staff works you have to get closer or I could get closer to you. Now here are my hands and let's pretend they are your hands. When you hold the propeller lever, you hold the rub lever through the notches on the other one, but you don't simply rub the rub lever through the notches like this. No no no. The trick is to hold the lever this way so that when it fits into the notches you can press against the propeller lever from one side with your index finger or from the other side with your thumb.
the hui stick

More Interesting Facts About,

the hui stick...

So while you rub the notches, you are also dragging a finger and constantly pressing one finger against one side of the stick or the other. And that is what the direction reverses. See this. I will start. Let's start with my thumb. I'll try to separate them so it's very obvious when it changes. Here I go. I'm pushing. I'm constantly pressing against the right lever with my thumb and now here goes the notch action. Nice! We've got some rotation and that's counterclockwise, but now I'm going to shift so that my finger, my index finger, is pressing against the left side of the propeller lever.
the hui stick
Are you ready? Boom. Oh! Investment! Pretty cool, huh? but how does it work? Well, to start this investigation let's talk about how the propeller lever moves when the notches are rubbed. Well, that should cause some up and down movement. Vertical, straight up and down. Except not exactly. No matter how hard you try, there will always be a small mistake. Even if it's just the width of an atom, horizontally and that's really all it takes to induce a little bit of rotation. You can try this at home. Take something like a pencil and a roll of tape or some other ring-shaped object.
the hui stick
Pass the pencil and try to move it only up and down. No matter how hard you try, rotation will always occur. Only if you are able to move the pencil up and down through the exact center of mass of the ring, so that you are only pushing it up and down, you will not get the rotation, but the slightest error introduces a torque that causes rotation and then a feedback loop makes it stronger and stronger. This is exactly what is happening with the hui stick. I don't know if you can tell, but the shaft that connects the propeller blades to the propeller lever is much thinner than the propeller bore.
Here is an example that has been deconstructed. You see, that shaft is pretty thin and the hole in the propeller is pretty big. This means that as the shaft bounces, it actually bounces inside the propeller hole and can push and drag the propeller through friction. To see how exactly those propeller lever vibrations work, we got some great slow motion footage. This is how we do it. I took a laser measure that shoots a laser beam, there's the dot, and I grabbed it with the same hand as the hui stick and projected the laser dot onto a wall on the other side of the room so that when I stroked the notches, both laser measure and the hui stick would vibrate together and I could see how it vibrated.
Now, when I don't even press a finger against the propeller lever, I still have a pretty chaotic movement. The propeller lever doesn't just vibrate up and down. Sometimes it goes in circles, but it's a mess. It is definitely not controlled. But if I press my index finger against the left side, the laser pointer moves clockwise. And if I press my thumb against the right side, the laser pointer rotates counterclockwise. And because the shaft has room inside the propeller bore to move, its circular motion easily translates into propeller rotation. But why does putting a finger on the side produce a circular motion?
Well, many articles have been written about how a hui stick works and not all of them agree with each other. Many explanations simply say that this happens and don't get into the actual mechanism, but I have done some experiments of my own and would like to present some of my findings and this is what I think is important in the functioning of a proper hui stick. I think it doesn't just matter which left or right side you press your finger on. It also matters which top or bottom side your finger presses against. And here's why. Suppose this circle is a front view of the propeller lever like this, right?
So we look at it directly and the assembly in the middle is the shaft in the middle that the propeller sits on. Now if this is the hui stick, as I rub the notches, the stick is pushed up and down. It is pushed down when the club is at the top of a notch and then when the club flies up because of course my hand is holding it and it produces torque to keep it in contact with the club which rubs, goes up and then It is pushed down when the stick is above a notch. Then it goes back up when I'm in a notch and so on up and down.
But when I drag a finger along the hui stick, my finger is slightly on top. Good? I'm not going to get any lower than the middle of the stick. I'm at the top. And look what happens. Two pairs. Two torques because when I press a finger against the lever like this I am creating a torque that causes rotation in this direction. But of course the lever doesn't keep turning in that direction because my stabilizing hand is pushing the other way. It produces a buttress that holds the lever in one position. And it is the interaction between these two pairs that causes the spin in a particular direction.
And here's why. Let's go back to our big circle. If this is the hui stick and my finger, let me take off this cap and my finger will be here. Let's say my finger is up here. Producing a push, a force, a torque in that direction and my stabilizing hand is producing a torque in this direction. When the notches are rubbed and the lever goes up and down when it goes down, it temporarily disengages from the torque of my finger and now the torque of my stabilizing hand gains and moves slightly this way before coming back up and reengaging with my finger and through.
The finger constraint is pushed this way only to be pushed down away from the finger where the torque of my stabilizing hand plays a much more dominant role and so we get a rotation like this. Rotation that is counterclockwise when viewed from the front. Let's see if this can be confirmed by experiments. I'm going to put my finger on the upper right quadrant as seen from the front. Are you ready? Upper right quadrant seen from the front. Will I receive counterclockwise movement towards you? Yes. Now, if I put a finger instead, let me erase this so we have a nice, clean diagram.
If, instead, I rub my finger on the other side at the top so that my finger is right here. That's a big extended finger. If I put my finger here and push this way, what happens is that as the notches rub and the propeller gets stuck, oh wait, if my finger pushes this way, then my stabilizing hand will produce counter-torque on the opposite direction. address. This is very important. So the hand holding the back of the club always turns it in this direction. So, oh yeah, let's take this one. Now when the propeller lever is moved down because the friction lever has reached the top of the notch, it is disengaged with the torque of that finger and pushed this way.
Then it flies up, reengages with the finger and that torque brings it back this way and so on until we achieve a clockwise rotation. Will a finger dragged across the top left side result in clockwise rotation? I think we already know the answer to this question. I'm going to rub my thumb along that side, which for you is the top left side and we'll get a clockwise rotation. Pretty impressive. But if this is true, that means that it should matter whether I'm above or below the center of the club because if we restart our diagram here by putting a finger not at the top right or top left, but at the bottom, like for example here, Push Against lever this way means that we have to produce a torque moving in this direction with our stabilizing hand.
Wow, I'm not a very good drawer, but I think the point should be made pretty clear. Now, when the club is pushed down by the friction of the notches, it catches on this finger and is pushed in that direction, but then it flies up and now that counterweight of that stabilizing hand pushes it a little to the right and so on. successively. then we get a clockwise movement. We got counterclockwise movement when my finger was in the upper right quadrant, but in the lower right quadrant we should be seeing clockwise. Let's try and experiment. I'm going to start by putting my finger in the lower right quadrant.
I'm going to press against that dial while I rub the indentations. We should see some turnover and we do. We see a clockwise rotation, but now I'm going to move my finger to the upper right quadrant. And change direction. Likewise, if I rub my thumb along the upper left quadrant, I get a clockwise rotation, but if while doing this I manage to move my thumb toward the lower left quadrant, I reverse the directions. Very cool. Very cool. If this explanation is true, then we should not have a controllable direction of rotation when a force is applied from which the vertical up and down motion of the vibrating rod cannot escape.
To test it, I created a hui comb. It's like a normal rubbing stick, but it has these teeth that allow me to apply torque directly 90 degrees from the up and down movement caused by the rubbing of the notches and because these teeth are quite long when going up and down , do not disengage the propeller lever from that pair as you would with a finger. Now let's see what happens here. I'm going to start by applying torque on what for you is the left side of the lever. And we have some turnover, but look what happens when I change.
No reversal. Well, here comes the strength of the left side and now the right. I'm really pushing, but the propeller lever can't escape the force and therefore can't take advantage of the interaction between the opposite direction of torque from one hand and the opposite torque from the stabilizer hand, which is what I think which leads to rotation. Please, when you get your hui stick, do your own experiments. It's a blast and a really good workout, especially for someone with weak hands like me, so have fun, stay curious, and as always, thanks for watching. By the way, the shirt I've been wearing all this time also comes in box eleven.
I talk about cardinal and ordinal numbers on how to count beyond Infinity and I love cardinal numbers. Cardinal. It's a great word and it's a great bird. Cardinals are a very common sports team mascot. In fact, my high school, Blue Valley Middle School, was and is the Cardinals. So we started thinking what would happen if we made a t-shirt that looked like a t-shirt or that represented a sports team but not just the cardinals but the transfinite cardinals. Now, the smallest transfinite cardinal, the smallest amount of infinity is, of course, Aleph-Null and there is the symbol for Aleph-Null.
Aleph-Null is how many integers there are. It's how many whole numbers there are. It is how many even numbers there are and how many odd numbers there are. That's why I wear this shirt with an infinite sense of pride. And I hope you do.

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