| This is how the project began. I went to the store in quest of a
battery-powered car of some sort. One that preferrably used only one or
two AA batteries. This one took two AA's in the transmitter, two in the
receiver. Perfect. I'll explain the low voltage requirement later .
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New in package
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| Some disassembly required. Further progress required
dissassembly. This unit was very cheap, held together with only a few
phillips screws. Thank you, New Bright™! (I wonder if their oil lamp
logo is any coincidence.) |
Let the hacking begin...
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| Down to the elecronics. I chose to leave the radio control stuff
intact, in case they would be of any use. My intentions were to modify
the unit so it would be easy to power the entire system with the
thermoelectric module--including radio control, or just power the motor
for basic propulsion. |
Getting ready to modify
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| A twisted pair of red and black straight off of the battery terminals,
and a pair of yellow and green straight up off the motor terminals.
I'll let you guess where these wires came from. (Give up? Okay, they're
telephone wires.)
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New wires soldered in
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Originally intended to provide refrigeration in 12 volt portable
coolers, these modules will also generate electricity when heated on
one side and cooled on the other. And a handsome quantity, too--not
just microvolts. Together, they will produce about 3.2 volts open
circuit with the grease burner under them. Powering the jeep with drive
wheels raised, that drops to about 2.4 volts--the same as two NiCD AA's.
This toy jeep originally ran on only 2 AA batteries, so the voltage put out by these two thermoelectric modules was very nearly the right voltage to power the motor. There wasn't enough power to run the radio control electronics, however.
I got these on ebay a while ago for around $15 each as I recall.
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Marlow thermoelectric module
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I used two of the Marlow SP2348 modules in series for the heat to
electricity converter. I used white heatsink grease to make a good
thermally conductive bond between the two heatsinks. Actually, the
bottom heatsink (the hot side) was just a flat plate of aluminum, about
1/16" thick.
The cooling side was a leftover heatsink from an
old UPS (uninterruptible power supply), you know, the type they use for
power backup on computers. |
Mounting the modules to the heatsink
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| Since the cheap plastic construction of the donor car would not be able
to stand up to much heat, I took some aluminum flashing and folded up a
box which fit neatly into the passenger compartment (roll bars, seats,
and dashboard had to be removed). The thermoelectric module assembly is
visible to the left. |
Flame box for vegetable oil burner
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| I didn't want the tea light bouncing around in here and sloshing putrid
oil all over the pristine interior of my newly converted grease car, so
a simple holder was devised, also of aluminum flashing. |
Tea light holder
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| My wife burns these at an approximate rate of 2.88732987234 per month, so she was happy to donate one to the cause. |
Used tea light cup for burner
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| Boy this stuff is nasty. It was sorta cold from being out in the
garage, so it poured out in chunks. Note to self: The same thing would
happen in the fuel tank of an automobile. |
Fill 'er up with grease, Charlie
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| I got some votive wicks at a local craft store to use as the wicks. I
knew it would take more than just one wick, from some preliminary
testing with an ordinary white-wax tea light. |
Tea light in holder
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| Simpler is better. I've tried all sorts of different ways to vaporize
and burn veggie oil. Lots of failures. This one works. Not very
serviceable though, because the wicks burn down as the oil level drops,
and they need to be replaced. |
Six-wick oil burner
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| The heatsink/thermoelectric module unit is held on with some heavy duty
spring clips. It can easily be unclipped and attached to other
heat-powered projects. (An oil-powered transistor radio is next on the
list!) |
Complete unit with heatsink
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Here's a movie clip
(9.63MB quicktime .mov, Sorensen 3 codec) of the Jeep spinning its
wheels on the test bench, and then motoring under its own power. There
didn't end up being enough power to operate the radio control system,
so all it can do is drive in a straight line. I think that with some
gear reduction and steering servo upgrades, this could be overcome also.
(For best results, right-click the link for the movie clip and choose "save link target as" to save it to your desktop.) |
Motoring under its own power
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Projects 
