How to Make a Pencil Move in a Mysterious Way




About: Phil Davies
This describes a method I came up with for giving spin to a pencil, allowing it to cruise horizontally in a mind-boggling way.

Step 1: Type of Pencil

Any pencil will do, but avoid the built-in erasers. Lighter pencils are better than heavy, round pencils are slightly better than hexagonal.

For reasons explained later, it's better if the pencil is sharp. However, watch out for eyeballs when throwing sharp pencils!

Step 2: Holding the Pencil

Hold your hand in the position you would use to prepare for clicking your fingers. This is usually with your longest finger against your thumb.
Place the tip of the pencil in between these digits, such that when you do click your fingers you will be rolling the pencil.

Step 3: Launching

Click your fingers. The pencil will start to spin, but also the pencil will start to exit from the grip of your finger and thumb, and in so doing will engage its narrower parts in your grip, decreasing the torque on the pencil, but increasing the rate of rotation.
The pencil will leave your hand with such spin that it will hum.

Step 4: Style

Use various throwing actions: start with pencil hanging down, and throwing it underarm as you spin it makes a log which is impossible for others to catch. Hold your arm out horizontally to your side, with the back of your hand facing forward and the pencil in line with your arm, moving your arm forward as you spin it. This launches the pencil straight forward with a load of backspin, which gives it lift. It can fly quite slowly in a straight line. When you get it right it's really quite amazing.



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    19 Discussions

    im having a problem viewing the videos every time i try i have to restart my computer (quicktime and other sof ware is up to date) any one elce having this problem?

    9 replies
    infodudechicks dig me

    Reply 11 years ago on Introduction

    I've put them on my youtube account: "onlyinfoexists" - you could watch them there, soon I'll have another go at referencing them from here.

    Ok, I've tried that. I can't see the embedded videos myself, but there seems to be a space left where they should be. Perhaps they're not available from youtube yet.

    I guess this is an anglo-american difference, but it sounds about right. That thing you do that makes a noise as your middle finger goes smacking off your thumb.

    I dig it. Just gathered about 14 pens and pencils and works with both. I found that if you remove the ink tube from a bic pen it makes it lighter and "floats" a little further. Cool instructable.

    1 reply

    11 years ago on Introduction

    So, the trick is backspin? That would be the magnus effect then, definitely better with a smooth pencil.

    I once saw a chap throw a ping-pong ball with so much back-spin that it actually looped in mid-air. He used a device similar to my Cracker Chucker, but made out of a length of pipe lined with high-friction rubber.


    1 reply

    Reply 11 years ago on Introduction

    Yeah it's in the backspin. You can throw it in the more natural way, outwards from your chest, to get topspin and it usually turns around to head straight for the floor.


    Reply 11 years ago on Introduction

    Ok, I just made a clip which shows it in flight. There are other flight patterns and maybe some closeups I can add when I get help with the videocam.


    Reply 11 years ago on Introduction

    I could use a video as well. Not because my pencils are on the other side of the room, but because I just don't get it. (In other words, I'm stupid, not lazy.)