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# Plasma Car Success!

Reverse (Fall 2013)Sean Murray

Reverse Engineering ended with a triumphant cheer as we succesfulyy built our own plasma car (a toy car that turns centrifugal force+friction into forward motion--no motor or ramp required!)

The team showed an impressive will to tinker, and finally locked in the correct relationship between the axis of rotation and the wheels.

Below find video of the first working plasma car, dedicated to our peerless collaborator Nik!

# Reverse Engineering: Plasma Cars!

Reverse (Fall 2013)Sean Murray

After wrestling with short-circuiting toasters and solar cells that seemed hellbent on shattering, we're closing the Summer/Fall session of Reverse Engineering with a big, mechanical challenge: Plasma Cars!

It's a toy car that uses only inertia, friction and centrifugal force to move forward (at quite a clip!)!

We're off to a good start, and have one session left to try and get a working car.

Stay tuned!

# Reverse Engineering: Last Day of Solar Cars

Reverse (Fall 2013)Sean Murray

Daylight Saving Time ends this weekend, so this is the last time our 4-5:30pm class would have enough sunlight to test solar-powered cars as we worked on them.

Some of use had the satisfaction of actually testing cars, while others scored victories making working solar panels, cutting axles with the rotary tool, and mounting motors.

# Reverse Engineering: Building Solar Panels to Power Motors

Reverse (Fall 2013)Sean Murray

We're trying to reverse-engineer the solar-powered toy car. We've dketched our designs and broken the build into discrete steps. Today we focused on building the solar panel that would power the motor.

The motor requires at least 1 volt of charge, But each cell maxes out at 0.5V. However, if you string cells together in series, you get a solar panel  where

Voltage = 0.5 * NumberofCells

Awesome!

The sunlight is less intense by the time we meet in the afternoon, so we decided to make our panels' voltage capacities twice as much as the motors' voltage requirements. At four 0.5V cells in series, the panel produces 2V. Three folks finished and successfully ran the motor off their panels!

Here's a fun thing to think about. Why should a series wiring of the cells increase voltage (V), and parallel wiring increase current (Amps)? Why not the other way around?

# Reverse Engineering: Into the Sun

Reverse (Fall 2013)Sean Murray

Having acheived hands-free toasting last week, this week we started in on a new challenge: reverse-engineering Ben's solar-powered toy car.

Our goals in this new project are to explore

--a new source of power (DC from photovoltaic solar cells instead of AC from the wall outlet)

--a new type of resistance (revolution of a motor rather than heat from wire)

--a new type of work (motion instead of heat.

Next week we'll solder our solar cell "fuel" sources, before connecting them to motors and wheels!

# Reverse Engineering: Look! No Hands!

Reverse (Fall 2013)Sean Murray

Last week we learned the basics of circuits and built functioning heating elements. At the last minute of class before clean-up time, we held a piece of bread above on of teh elements, and watched it become toast.

But holding bread while it toasts is tedious, and a little dangerous. So, this week we challenged ourselves to build hands-free toasters. I.e., toasters that hold the bread for you!

"I think my base is about to catch fire..." Parker notices a design flaw.

# Reverse Engineering: Building Heating Elements

Reverse (Fall 2013)Sean Murray

Nik began today with a great, hands-on intro to circuits. After a brief intro to concepts of power source, load, and closed and open circuits, we felt a little more confident about wiring our own toasters.

We guessed that the "load" in our circuit was the nickel-chromium wire. When it resists current, it heats up and toasts bread. The challenge for today was to complete a working heating element.

In the end most teams completed a working heating element--and Ben and Parker's (below) toasted a piece of bread (held over it by brave volunteer Keaghan (not shown)).

# Reverse Engineering: Toaster Re-Assembly

Reverse (Fall 2013)Sean Murray

We had the second law of thermodynamics working against us today. Toasters, like most matter, tend towards chaos. Order is unlikely. Taking toasters apart is pretty easy and very fun. Putting toasters back together is difficult.

But, still pretty fun.

"This is a lot more parts than I remember!" -- Frances

We had brief discussions on how, exactly, a toaster uses heat generated by (electric resistance) to crisp bread Right before cleanup time, as well as short circuit safety and "bare minimum functionality"--a term to guide us to the simplest toaster possible.

Just before cleanup time, Kai and Earnest had successfully looped nickel-chromium wire around a fireproof mica sheet, and demonstrated that they'd built a complete circuit. At 1/10 the voltage, it worked great!

# Reverse Engineering: Toaster Disassembly

Reverse (Fall 2013)Sean Murray

Inside the humble electric toaster lies a history of engineering. Each resistor, spring, lever and circuit board is an exhibit in a tiny museum of problem solving.

We began by testing our toasters and reviewing the Rules of Taking Stuff Apart.

Kai and Earnest disassemble the "chassis". Clever manufacturing abounds--most of the joints are bent metal tabs--an inexpensive alternative to fasteners.

Next week, we'll try to put the toasters back together.

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