Small Motor Creations 5 - Flywheel

The Flywheel is an unseen hero with so many amazing abilities. They are used in everything from Uninterruptible Power Supplies to the Attitude Control systems of spacecraft. A Flywheel's angular momentum can be used to to resist or impart a rotational force, or to store large amounts kinetic energy for reuse.

The mechanism behind this flywheel doesn't get much simpler. Its a spinning disk of mass contained within and enclosure. One of our little Fa-130 Motors spins the flywheel, and the enclosure lets us experiment without interrupting its rotation.

So what can we do with our flywheel?  Well first and foremost, It makes a great gyroscope.

The spinning flywheel is resistance to changes in in it angular momentum. So you can easily balance it on its edge. Interestingly, because there is so much energy in the momentum of the spinning wheel, it will keep balancing on its edge for about a minute after power is removed.

Electrical energy is being converted to kinetic energy by our little motor. That kinetic energy is stored in the momentum of the flywheel, and can be converted back to electrical energy.  Like most DC Motors, the our little Fa-130 will also function as a small generator. To test this we'll need a voltmeter. Hammerspace has a nice one from Fluke. 

With the Battery connected, the circuit shows 1.033 Volts.  Where using a 1.5 Volt D-Sized Battery, but the voltage is being drawn down by the current demands of spinning the flywheel.

When the battery is disconnected, the meter shows 0.338 Volts. That is voltage being generated by our motor as its being spun by the flywheel. This little motor makes a poor generator, but we're still recovering almost a third of what was initially in the circuit. 

As the Flywheels slows, the voltage produced drops. After 30 seconds, the flywheel is only producing 0.042 Volts.

This has been an interesting experiment, and if I get the time to revisit it I'd like to couple the Flywheel with an electronic controller to make a rudimentary Reaction Wheel.

Download the Flywheel Files From Thingiverse: www.thingiverse.com/thing:557984

FA-130 Size Motor At Pololu: www.pololu.com/product/77

Small Motor Creations 4- Impeller Pump

The Impeller Pump is a simple example of a mechanism that is essential to industrialized society, but is almost never seen.  Impeller pumps are found a garden fountains and basement sump pumps, water treatment plants, and anyplace else liquids need to be moved quickly and efficiently.

The principle behind the Impeller Pump is identical to the earlier Vacuum project.  The FA-130 motor spins Impeller blades, imparting centripetal acceleration on the water and throwing it outwards at higher pressure. This high pressure water exits through the outlet.  For and impeller pumps blades need to be submerged for it to function. So our little motor is going to getting wet in this project.

My knowledge of the complexities of and impeller pump is limited, so this project is a bit of an experiment. We're going to test what effect the diameter of the rotor has on the output of the pump. 

The smallest pump has a rotor diameter of 20mm, the medium size pump had a 30mm rotor, and the large pump has a 40mm rotor.

The pumps outlets are all sized to accept a piece of 4mm tubing. To test the pumps, I timed how long it takes each one to move 1 liter of water from one container to another. 

As a control, I used the 4mm tube to siphon 1 liter of water from one container to the other, which took 27 Minutes 8 Seconds, or 36 mL/Minute

The 20mm Pump moved 1 liter of water in 4 Minutes and 44 Seconds, or 211 mL/Minute

The 30mm Pump moved 1 liter of water in 5 Minutes 48 Seconds, or 172 mL/Minute

The 40mm Pump moved 1 liter of water in 9 Minutes 28 Seconds. or 105 mL/Minute

Alright, So all three of these pumps suck...

Its interesting that the pump with the smallest rotor diameter moved water the fastest. I speculate that the smaller rotor is accelerating less water at a time, letting it spin faster and move more water overall.

Download the Pump Files From Thingiverse: www.thingiverse.com/thing:545388

FA-130 Size Motor At Pololu: www.pololu.com/product/77

Small Motor Creations 3 - Vacuum

The Vacuum is a humble cousin of the mechanism you'll find in everything from your Dustbuster to a Roomba. A spinning rotor creates an air pressure difference, drawing air in through the nozzle and exhausting it out through the slots. Dust and dirt are drawn in with the airflow, and captured by a filter.

The rotor is attached to one of out little FA-130 motors.  As the rotor spins it imparts centripetal acceleration on the air between the vanes. The air is flung out, creating an area of low pressure at the rotors center. The suction nozzle attaches directly over this area of low pressure, and air exits through the slots around the outside of the Vacuum's body.

A small piece of toilet paper make a simple filter to capture the dust we pick up, otherwise it will just be blown out the exhaust. The Toilet paper is captured between the body and nozzle, with the excess torn away.

So how well does our tinny motor vacuum work? We can use a handful of sawdust from the Hammerspace dust collector to test it out. 

Well its no Dyson, but that's not half bad for our tinny little motor and a few hours of work.

Download the Vacuum Files From Thingiverse: www.thingiverse.com/thing:539986

FA-130 Size Motor At Pololu: www.pololu.com/product/77

Small Motor Creation 2 - Dart Thrower

The Dart Thrower is a simple version of the flywheel mechanism used in pitching machines and battery powered Nerf guns like the Barricade.  The principle of operation is simple.  Two flywheels are spun in opposite directions by the motor. The gap between the flywheels is slightly smaller the the diameter of the dart, and they will grip it as it passes between. Energy is transferred from the flywheels to the dart, and it goes forward, quickly.

The motor is directly attached to one Flywheel and the other is spun by the interconnecting gears. The gears spin the two Flywheels spin in opposite directions.

Now we have to see how well the Dart Thrower works by testing how far it can throw. I created a stand that grabs the bottom of the motor and holds the it pointed up 30 degree. Its taped to the floor, so it wont move during the test.

I used the Hammerspace workshop floor as a handy premade reference grid.  The floor tiles are 12 inches square, and for a bit of added precison, I laid down a tape measure staring at the base of the thrower.  

We're going to fire 10 darts from the Dart Thrower, which will give us a good idea for how far it can shoot using out little FA-130 size motor and 4.5 volts.

From above we can see that the darts cluster between 6 and 12 feet downrange. The furthest dart is 147 inches from the launcher and the closest at 70 inches.  The average of all the darts is 122 inches, or a little more then 9 feet.  Not bad for out tinny little motor.

The Dart Thrower is Sized to use Nerf N-Strike Style darts

Download the Dart Thrower Files From Thingiverse: www.thingiverse.com/thing:534969

FA-130 Size Motor At Pololu: www.pololu.com/product/77

Small Motor Creation 1 - Ducted Fan

A Ducted Fan is a little like an electric jet engine. They are often used in model aircraft to in place of jet engines, and hold a place of honor in every sci-fi and futuristic aircraft I've ever scene.  Ducted fans offer the promises of high power densities in small protected packages without all those unshrouded propellers tips whipping about. 

A Ducted Fan is made up of three primary parts: the impeller, the shroud, and the motor.  The motor is of out little Pololu FA-130 Motors.  The impeller blades are fixed a 45 degrees and the hub is large enough to cover the face of the motor. The shroud is a bit trickier.  For the ducted fan to work properly it has to come as close to the spinning ends of the impeller as possible without touching. It also has to have enough strength to hold the motor in place as it spins. I designed the shroud to have a 0.5mm gap between its inner surface and the impeller blades.

I wasn't expecting much from this project, Ducted Fans are notoriously hard to design. So I was shocked when it shot across the table after I applied power.  This little puppy produces some thrust!

We can quantify the thrust produced using a small digital scale and a test stand.  The test stand holds the Ducted Fan above the surface of the scale, so it can pull in air.  The fan is installed face down, with the exhaust pointing up.  Any thrust produced will push down against the surface of the scale through the test stand.  Thrust will be quantified as an increase in the weight registered by the scale.

To keep things simple, I set up the Ducted Fan, test stand and batteries on the scale and used the tare function to zero them out, so at the start of the test, the scale reads 0.000kg.

With the fan running the scale reads 0.012kg.  This little Ducted Fan, made from a $1.99 motor and some 3D Printed Parts is producing 12 grams of thrust! That's shocking!  In this test i'm running the motor at 3.6 volts, slightly above its design spec.  The Fan and motor weigh 24 grams, so it producing half it own weigh in thrust.

I wonder what would happen if I swapped this basic 130 size motor for one of the models design for high speeds?

You can download the Ducted Fan and the Test Stand from Thingiverse.

Ducted Fan: http://www.thingiverse.com/thing:530911

Test Stand: http://www.thingiverse.com/thing:530914

The FA-130 size motor I used is available on Pololu: www.pololu.com/product/77

10 Simple Creations With Motors

Digging through my project box, I found a stash of  Mabuchi FA-130's that I bough from Pololu long ago. 

Mabuchi FA-130's are great little project motors. The 130 size is commonly used in toys and inexpensive electronics, and they are available in a variety of voltages and ratings. These motors are rated at 1.5v to 3v, have a free running speed of 12,300 RPM, and cost $1.99 from Pololu.

I'm going to use these motors as the basis for 10 simple creations over the next few days. Each creation will make the this simple motor do something useful.

-Michael