A two-stroke gasoline engine made from the compressor of a fridge!
It was while describing how he engineered his own hall-effect-triggered, ignition-control module that we knew Joachim Hall, or Makerj101 as he’s known on YouTube, was perfect for Hot Rod Anything. The 22-year-old engineering student started off admitting that he learned more from the prolific online streaming service than in any textbook: “I read very little, so most of the knowledge I’ve gained is from YouTube and the internet,” he explained. “I usually look at YouTube first, and if I find nothing else, then I’ll find an article to read. I try to give back by sharing my builds and experiments on there.” It was through finding Stirling engines that he began his path toward building his own internal-combustion engine.
“My dad’s an engineer, so he always taught me how to take things apart and rebuild them. I was 14 or 15, and I found out about Stirling engines on the internet and thought to myself, ‘What are these magical machines that run on no combustion?’ And then I found out that they were really simple to make,” Joachim continued. “From there, I went to build steam engines, and while building those, I found out how to make a successful piston out of JB Weld.” While he moved on to more complex machines, Joachim built his channel’s audience (60,000 subscribers), which provided not just encouragement but also valuable feedback.
This brought his learning curve from Stirling engines, through steam engines (where he mastered making pistons out of JB weld), and into internal-combustion engines with his copper-pipe-based build in 2016, which became something of a viral hit. “I had taken compressors apart before and found they had the perfect cylinder, piston, rods, and crank, and I wondered if it could be converted into a two-stroke. My copper engine worked, so it couldn’t be that hard; that was just a first attempt and I was wingin’ it,” he joked. “An internal-combustion engine is a lot simpler than people think. So that’s what I’m trying to prove, that you can build an internal-combustion engine in your backyard with very minimal stuff.”
To build this engine, he narrowed down his toolset from the soldered copper-pipe engine to the most basic of handtools and skills. Other than a hacksaw and drill, everything Joachim used to build the intake and exhaust ports, cylinder head, crank case, and carburetor could be bought from the “tool” isle at a grocery store—he stuck to simple screwdrivers, pliers, adjustable wrenches, and clamps to machine and manipulate the compressor into a two-stroke. The compressor was first disassembled before the block was ported for the intake and exhaust ports. After sorting that, the reed-valve cylinder head of the compressor was replaced by a cut-down IBM computer heat-sink, which was also drilled for a spark plug.
Now that the compressor could breathe like a two-stroke, it was time to give it fuel. A crank case was built to seal the exposed rod and crankshaft, and a block of extruded aluminum scrap was drilled into a simple one-barrel carburetor with a barrel-valve throttle. For now, the ignition is sourced from a neon-sign transformer, but Joachim explained how he could build his own transistorized ignition control module before we began talking about how to use a self-ignited automotive coil. The irony between curiosity versus practicality was not lost on us, but building what you want with what you’ve got is the spirit of hot rodding.
Specs
Manufacturer Tecumseh
Model AE155AL
Type Reciprocating compressor
Type now Piston-port, two-stroke gasoline engine
Displacement 8.85 cc
Bore 2.54 cm
Stroke 1.75 cm
Compression ratio approx. 8:1
Crankshaft diameter 19 mm
Carburetor bore 4.7 mm
Venture bore 3.1 mm
Fuel jet size 0.5 mm
Intake port 6.5mm x 5.0mm
Transfer port 9.0mm x 5.0mm
Exhaust port 9.0mm x 5.0mm
- The cylinder head is an aluminum heat-sink that used to cool an IBM processor. About two-thirds of the fins’ length was shaved to create clearance for the head bolts and spark plug.
- The carburetor is a 3/16-inch bore with a 1/8-inch venturi, and it uses a 0.5mm mechanical pencil tip as the jet. This carb was machined with just an electric drill, where the 1/8-inch hole was drilled first and a 3/16-inch bit was used to bore out the carb to a select depth from both sides. This leaves enough of the 1/8-inch hole to create the venturi—the bottle-necked portion of a carb that increases air velocity, therefore dropping air pressure enough to suck fuel (though metered jets or nozzles) into the air charge.
- One crucial modification to the newly made crankcase was this access plug, which allowed Joachim to remove the connecting-rod cap fasteners. It’s forward-thinking modifications like this that are key to a practical conversion.
- The original bearing cap was used, but it was remounted on an aluminum plate to seal the crankcase while also creating a path for the intake port.
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