Overbalanced Wheel (Fake Perpetual Motion Machine for Fun)

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Introduction: Overbalanced Wheel (Fake Perpetual Motion Machine for Fun)

Of course, perpetual motion does not exist. But lots of great inventors, including Leonardo da Vinci, played around with the idea so I feel like I'm in good company. I think anyone who is interested in engineering, mechanics, and physics or the history of these fields will enjoy building this project.

I've always been facinated by the "Overbalanced Wheel", which is basically a wheel with weights that slide or move from a position close to the center of the wheel to a postion near the edge of the wheel as it turns; basiclaly shifting more weight to one side of the wheel to keep it turning in that direction.

I decided to build my "Overbalanced Wheel" out of an old CD (always great for DIY projects), some screws and metal brackets I bought at Lowe's and a few "secret" components that will be revealed in Step 5.

NOTE: Don't look ahead to Step 5 unless you want to take the fun out of perpetual motion!

First, check out the video!

Step 1: Materials & Tools (Non-Secret)

Non-Secret Materials Needed:

1 - CD
8 - 6-32 Cap Nuts
8 - 6-32 Screws
8 - 6-32 Washers
8 - 6-32 Nuts
6 - 1/2" x 4.5" x .035" Metal Mending Plate (Lowes 364404)
4 - 1/2" x 1-1/2" x 1-1/2" Metal 90D Plate (Lowes 364311)
1 - 1/2" x 3" x .035" Metal Mending Plate (Lowes 364323)
1 - 2" Metal Gear Shaft
1 - 1" Diameter plastic gear (to fit shaft above)
2 - Rubber grommets (same diameter as gear shaft)

Non-Secret Tools Needed:

Drill
Cutting Tool
Dremel
Screwdriver
Pliers
Hot Glue Gun

Step 2: Designing and Building the Wheel

My Wheel Design

I decided to cut slots in the CD and use weights made of screws, nuts, and metal caps to slide back and forth in the slots. I figured the slots needed to be angled from the center of the CD out toward the edges so the weights would slide "out" as each slot reached the falling edge and slide "in" as each slot reached the rising edge of the CD when turning clockwise.

STEP 1: Lay out the design on paper by dividing the CD into eight equal sections.

STEP 2: Add a 1/8" hole 1/4" from the edge of the CD for each dividing line.

STEP 3: Measure half the distance between each hole and the center of the CD and add another 1/8" hole for each dividing line.

STEP 4: Join the holes to make a 1/8" slot for each hole pair. (See the first photo).

STEP 5: Cut out and tape the pattern to a CD. See my note at the end about protecting the CD while drilling and cutting.

STEP 6: Drill the holes first being careful not to crack the CD.

STEP 7: Use a Cutout Tool with a 1/8" cutting bit to make the slots between each set of holes. Make sure you securely brace the CD and cut in a slow, smooth motion. Otherwise, you will likely crack the CD.

STEP 8: Clean up the slots using a Dremel. The weights must slide freely, so be sure to remove any burs or narrow areas in the slots.

STEP 9: Hot glue the plastic gear to the back side (label side) of the CD making sure to center it. I added a piece of silver tape under the gear to hide the gear teeth from the front of the CD. Some CD labels cover this area so the tape won't be needed.

STEP 9: Insert screws, washers, and cap nuts through the slots. The cap nuts should face the front (shiny side) of the CD.

NOTE: As you can see from the photos, I scratched up the surface of the CD quite a bit during the building process. In retrospect, I should have protected it better during drilling, cutting, and sanding.

Step 3: Building the Frame

I built a simple triangle frame using hobby metal from Lowes.

STEP 1: Assemble a triangle using three 4-1/2" flat plates and two 90 degree plates leaving the top screw & nut out.

STEP 2: Assemble a second triangle as shown in figure 2.

STEP 3: Add a 3" flat plate to the back of the frame to stablize it.

STEP 4: Insert the wheel by sliding the the gear shaft through the top holes in the frame.

STEP 5: Add 90 degree plates to each side (3rd hole up) to further stablize the frame.

STEP 6: Insert grommets on each side of the grear shaft to keep the CD centered in the frame


Step 4: Testing It Out

Since we've already established that perpetual motion is impossible, I didn't expect this to work. However, I had no idea it would fail so miserably! Fact is, IT DOESN'T WORK AT ALL! It doesn't even start to work when I give it a nudge. If I spin it fast, it will run about as long as a wheel with no weights at all; maybe not even as long as that.

Now that that's over, please move on to Step 5 where the real motion begins...

Step 5: The Real Deal (Non-Perpetual Motion)

SPOILER ALERT - If you haven't gone through steps 1-3 or you want to keep believing in perpetual motion, please don't read this step.

Okay, so perpetual motion failed miserably. Now it's time to add some real motion to the project! I wanted to hide all of the electronics behind the CD (and remember the CD has slots cut in it), so everything had to be small; very small!

My first thought was to use a simple DC motor with a battery and a switch. But there is no good way (that I could figure out) to make it turn slow enough (and with enough torque) to resemble perpetual motion. I tried a potentiometer, gears, and PWM. Nothing worked to my satisfaction. 

So I decided a servo and microprocessor were needed, but they had to be very SMALL. The smallest servo motor I could find was the HD-1440A from Pololu . This is a great little servo with plenty of torque.

Next, I needed a really small microprocessor to handle the PWM to drive the servo at the desired speed. For this, I used a Teensy 3.0. Luckily, I happened to have a Teensy on hand since I was a contributor to their successful KickStarter campaign. The Teensy was perfect for this project; very small and easy to program (Arduino compatible). Plus, as a bonus, the Teensy has a special feature called "Touch Sense" that let me start and stop the wheel by simply touching the frame. This way I could give the illusion of starting the wheel by giving it a nudge!

Secret Materials Needed:

1 - Teensy 3.0 Microprocessor
1 - Teensy Arduino IDE
1 - Mini servo (HD-1440A)
1 - USB connection to a computer
1 - Small plastic driver gear
1 - 1/2" x 2" x .5" Metal Slotted Angle (Lowes 364266)

Secret Tools Needed:

Solering Iron
Helping Hands

Step 6: Preparing the Servo Motor

As with most servo motors, this one was configured for 180 degree motion. I needed continous rotation to turn the wheel, so I hacked it as follows:

STEP 1: Remove the two small screws from the bottom of the case.

STEP 2: Cut the label along the seam near the bottom of the case and gently pull the bottom cover loose.

STEP 3: There are three wires that connect the circuit board to the potentiometer. Detach those wires from the POT.

STEP 4: Since we only need the wheel to turn in one direction, you can just solder a 2k (approx) resistor between the two wires indicated in the photo. I had to experiment a bit to figure out which two wires needed to be connected to give a clockwise rotation.

STEP 5: Cut the access leads and cover the resistor with electrical tape (or shrink wrap) and carefully put everything back in the case.

STEP 6: Hot glue the plastic drive gear on top of the very small gear of the servo. Be sure to center this gear. I used a small nail in the center to line them up while glueing.

Step 7: Programming the Teensy

Before programming the Teensy, you'll want to download the Teensy Loader and  Teensyduino add-on for the Arduino IDE. After that, copy this simple sketch, compile, and load your Teensy. Notice the "touchRead" command that senses touch by reading capacitance. More info is available here: http://www.kickstarter.com/projects/paulstoffregen/teensy-30-32-bit-arm-cortex-m4-usable-in-arduino-a/posts (search for Touch Sensing).

#include <Servo.h>

// Overbalanced Wheel
// Using Teensy 3.0
// by Mike Soniat
// 12/24/2012

Servo servo;
int servoSpeed = 170;
int servoPin = 14;
int touchPin = 22;
int touchReading = 0;
boolean isStarted = false;

void setup()
{
  Serial.begin(9600);
  servo.attach(servoPin); 
}
 
void loop()
{
  touchReading = touchRead(touchPin);
  if (touchReading > 3000)
  {
    isStarted = !isStarted;
    delay(500);
  }
  if (isStarted)
  {
    servo.write(servoSpeed);
  }
  else
  {
     servo.write(0);
  }
  delay(20);
}

Step 8: Connecting the Servo to the Teensy

The next step is to wire the servo to the Teensy and add a wire for the "Touch Sense" feature.

STEP 1: Cut the connector off the servo wires and solder the wires to the Teensy board as follows:
  • Brown (-) wire: Solder to any GND pin. I used the one at the bottom center of the board.
  • Red (+) wire: Solder to either of the 3.3V pins. I used the one next to the GND pin at the bottom of the board.
  • Gold (signal) wire: Solder to any "PWM" or analog pin. I used pin 14.

STEP 2: Solder a length of wire to any "Touch Sense" pin. I used pin 22.

Step 9: Putting It All Together

Now, it's time to add the non-perpetual components to the "perpetual" ones.

STEP 1: Place a piece of double-sided tape on one side of the servo and attach it to the angle bracket.

STEP 2: Attach the angle bracket to the back of the frame as shown and adjust the postion of the servo gear to mesh with the CD gear.

STEP 3: Place another piece of double-sided tape on the back of the Teensy board and attach it to the back of the frame as shown.

STEP 4: Run the "Touch Sense" wire around the top of the board and attach it to the frame as shown.

STEP 5: To hide the USB power lead from sight during operation, cut a slot in a box or other base and run the USB cable up through the slot to the Teensy board. Tie wrap the cable to the frame if needed.

STEP 6: Turn the base around and you're ready to amaze your friends (as long as you keep them a few feet in front of it)!

Here's the video again in case you missed it in the Intro:

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    62 Comments

    how long does it turn for without the motor, after given a bit of a push

    I had no intention of perpetuating stupidity. I said right up front that it was "for fun". I also thought it was an interesting project and many people here seem to agree.

    It was interesting and clearly demonstrated at least part of the fallacy of the perpetual motion.

    i agree alot of fun misleading us dont lie based on your failures keep at it until u succeed and then make a instructable i firmly believe this does work u just have to make it correctly lol

    I am one of the agreeers! I think the process of building a perpetual motion machine, and then seeing it not work, is an excellent way to learn about the conservation laws of physics.

    You can here the electric motor in the background.

    If this device was called a variable fulcrum machine, no one would have any objection. It translates pure g's into motion at a rate determined by the average distance of the load arm over the average distance of the effort arm. I made some graph paper, modifed the shapes the Leonardo used, did some calcs, and found that you might expect an output of about 2/11 of whatever weight you use. That doesn't take into rpm, which will top out, but an increase in speed is an increase in output. Just remove the backslashes to see for yourself. The calcs are on the preceding page (use the wikitrail) \http\:\/\/princetonweb.org\/Neighbors\/pmwiki.php\?\n\=Overunity.Project1013-c

    I like this even tho its doesn't work. But what seems strange to me is every one thinks there is no perpetual motion machine when if you look down at your feet your standing on one. The earth.....?

    7 replies

    Er, the earth is slowing down and would ultimately fall into the sun as its orbit decays (if the sun doesn't turn into a red giant first and swallow it up first - likely).

    Possibly the Universe itself recycles and might be considered to be perpetual motion. No-one knows the answer as yet.

    According to historical records, Earth days and years were shorter than they are today. Either our clocks are suffering a temporal anomaly or the Earth is really slowing down.

    The earth is slowing down because of tidal locking with the moon (there's a what-if.xkcd about this), not necessarily from friction. Space is very close to a perfect vacuum, so the friction effects are negligible.

    Not so. Solar winds and the magnetic fields are known to have non-neglible (but small) effect. Given enough time and lack of meteors hitting the Earth to speed it back up, the Earth would eventually stop spinning

    I didn't mention friction in this case, just that the Earth's rotation and revolution are slowing down. If you want to argue about Luna and tidal forces, do a basic Google check on tides in different areas, and you will find that the data does not match with Luna/tide theory. Some bodies of water exhibit FOUR tides a day instead of the "traditional" two.

    Sorry, I said that badly in my first comment. I didn't mean to contradict you, just to add clarifying information in the last sentence. Anyway, tidal locking doesn't have to mean actual tides in water. The moon is tidally locked with earth, so the same side always faces us, and the moon probably hasn't ever had significant amounts of water. Also, that's pretty cool about the four tides a day, although I suspect that's more due to harmonics in the water basin and delay between the passing of the moon and the actual high tide.

    When it comes to tidal harmonics, you have hit the nail on the head. Most of the moons in our system are "locked" so that only one side faces the host planet. However, Luna is the only one that has such a slow orbit that it never goes "retro-grade" in relation to the Sun.

    If you increase the number of slots will that increase the spin speed?

    I agree! That is such an awesome project! Well done!

    I agree! That is such an awesome project! Well done!

    I agree! That is such an awesome project! Well done!