LEGO Vacuum Engines

Overview
A LEGO vacuum engine (LVE) type of LEGO High Volume Low Pressure Engine that uses a vacuum cleaner as its source of air flow. It is the most common type of LEGO HVLP engine on platforms such as YouTube because of the widespread availability of both a vacuum cleaner and the LEGO parts to build it.

Variation in Terminology
In the first 20 years of LEGO High Volume Low Pressure Engines, the term LEGO vacuum engine was the term used by the LEGO engine building community to describe HVLP engines. However when engine builders began experimenting with boosting engines using sources of both positive and negative pressure airflow, like that of a wet/dry vac, the all-encompassing term HVLP was adopted to avoid confusion as to whether an engine ran on suction or positive pressure. Many still affectionately use the term LEGO vacuum engine (LVE) as a term to describe the HVLP category of engine even if their airflow source used to power the engine is not a vacuum cleaner.

The founder of the lego vacuum engine
Erin Lassley is the inventor of the lego vacuum engine. He built the first lego vacuum engine in the winter of 1994 and ran the engine by blowing into it from his lungs. In the 1980s he first came up with the idea of building a lego steam engine with a heated pot of water and a vinyl tube. That failed and air compressers where to much so he used a wet dry vac to power his engines.

Single valve system
[SVS] is a type of lego vacuum engine where the valve is directly conected to the crankshaft and is 90 degrees off-set. The valve has two stages the first is when the valve is at TDC which alows the vacuum to suck the air out of the cylinder. The second stage is when the valve is at BDC and closes off the vacuum from sucking the piston up. The flywheel helps the engine go through the stages and keeps the engine running smoothly.

The piston and valve
4 by 4 studs is the most common type of lego piston since its durable, light weight, and minimum fiction. This piston allows for good airflow since the piston size is equal to a common size of a house vacuum hose nozzle. Also the 4x4 piston doesn't need a very strong vacuum to get good RPM’s.

The size of the valves depends on how big the piston is for example a 4x4 piston engine needs a 4x1 valve. Typically lego vacuum engine valves use a 1.5 stud crankshaft piece which allows for a speedy engine. Lego vacuum engine valves uses 1x1 with holes on the outermost studs of the valve during the first stage since it keeps the valve stable but still has good airflow. Lego L shaped tile pieces are used on the top of the valve during the second stage so it can block the vacuum from sucking air out of the cylinder and while letting in air from the top.

Construction
Unlike LEGO Pneumatic Engines (LPE), and LEGO Pneumatic Fake Engines, LEGO vacuum engines, the piston-cylinder assembly of a LVE is brick-made. This gives it the advantage of scalability and a wider variety of possible designs.

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Types of LVEs