four stroke

3 Articles

Fridge Compressor Turned Into Capable Little Four-Stroke Engine

December 2, 2020 by 18 Comments

Never underestimate the power of a well-stocked junk bin. Along with a TIG welder and mechanical ingenuity bordering on genius-level, all of which come to bear on this fridge compressor to four-stroke engine build.

The video posted by [Let’s Learn Something] is long, but watching it at double speed doesn’t take away much from the enjoyment. By using a piston-type compressor, a lot of the precision machining is already taken care of here. Adding the intake and exhaust valves, camshaft, timing chain, carburetor, and ignition system are still pretty challenging tasks, though. We loved the home-made timing chain sprockets, made with nothing more than a drill and an angle grinder. In a truly inspired moment, flat-head screws are turned into valves, rocker arms are fabricated from bits of scrap, and a bolt becomes a camshaft with built-up TIG filler. Ignition and carburetion are cobbled together from more bits of scrap, resulting in an engine that fired up the first time — and promptly melted the epoxy holding the exhaust header to the cylinder head.

Now, compressor-to-engine conversions aren’t exactly new territory. We’ve seen both fridge compressors and automotive AC compressors turned into engines before. But most of what we’ve seen has been simple two-stroke engines. We’re really impressed with the skill needed to bring off a four-stroke engine like this, and we feel like we picked up quite a few junk-box tips from this one.

Continue reading “Fridge Compressor Turned Into Capable Little Four-Stroke Engine” →

4-Stroke Clock Fires On All Cylinders

February 11, 2018 by 8 Comments

We love a good clock build around here, especially if it tells time in a unique way. This 4-stroke digital clock designed by [lagsilva] takes the checkered flag in that category. As it displays the time, it also demonstrates the operation of an internal combustion engine. The numbers take the form of pistons and dance an endless repetition of intake, compression, combustion, exhaust.

The clock’s digits are made from two LED matrices driven by an Arduino Uno and a couple of MAX7219 driver boards. The dots that form the digits move up and down the matrices in 1-3-4-2 firing order. As each piston-digit reaches top dead center, its number lights up. This makes it easy to see the firing order, even at higher RPM values.

Our favorite thing about this clock is the variable RPM setting. There’s a 10k pot around back that adjusts the speed of the pistons between 100 and 800 RPM, and it’s configured to accurately represent piston movement at each increment. Floor it past the break to watch the clock rev up and slow back down.

Although it’s difficult to read the time at 800 RPM, it’s awesome to see a real-time visualization of cylinder movement at the average idle speed of a passenger car. We think it might be neat to rev the engine another way, like with an arcade throttle lever or a foot pedal.

If you like the idea of a constantly-moving clock but prefer an analog readout, take a minute to look at this clock without a face.

Continue reading “4-Stroke Clock Fires On All Cylinders” →

The DIY Open Crank Engine Moped

October 16, 2014 by 50 Comments

Anyone can strap a two-stroke engine on a bicycle to create a moped. But [robinhooodvsyou] has created something infinitely more awesome. He’s built an inverted open crank engine on a 10 speed bicycle. (YouTube link)  As the name implies, the engine has no crankcase. The crankshaft, camshaft, and just about everything not in the combustion chamber hangs out in the open where it can be seen and appreciated.

[robinhooodvsyou] started with an air-cooled Volkswagen cylinder. He filled the jug with a piston from a diesel car. Camshaft, flywheel, valves, and magneto are courtesy of an old Briggs and Stratton engine. The cylinder head, crankshaft, pushrods, and the engine frame itself are all homemade.

Being an open crank engine, lubrication is an issue. The crankshaft’s ball bearing is lubricated by some thick oil in a gravity fed cup. Even though the engine is a four-stroke,[robinhooodvsyou] adds some oil to the gas to keep the rings happy. The camshaft and connecting rod use Babbit bearings. While they don’t have an automatic oiling system, they do look pretty well lubricated in the video.

Starting the engine is a breeze. [robinhooodvsyou] created a lever which holds the exhaust valve open. This acts as a compression release. He also has a lever which lifts the entire engine and friction drive off the rear wheel. All one has to do is pedal up to cruising speed, engage the friction drive, then disengage the compression release.

We seriously love this hack. Sure, it’s not a practical vehicle, but it works – and from the looks of the video, it works rather well. The unmuffled pops of that low 4:1 compression engine reminds us of old stationary engines. The only thing we can think to add to [robinhooodvsyou’s] creation is a good set of brakes!

Continue reading “The DIY Open Crank Engine Moped” →