If you are not familiar with Colin Furze and his jet fueled shenanigans consider this your baptism by fire. This crafty ‘Brit is famed for his creative and outlandish projects, usually involving some form of home brew fabrication and junkyard parts. Furze builds jet engines from turbochargers, duct tape, and dryer tubing — and uses his mechanical abominations to power everything from mobility scooters to shopping carts.
Among Furze’s passions is the simplest internal combustion engine ever devised — the pulse jet. Originally devised as an aviation propulsion system in the early days of jet-fighter aircraft, the pulse jet relies on pure scavenging and flow harmonics to operate. These tubular engines manifest in various configurations but are generally divided into two categories — valved, or valve-less.
The traditional valved pulse jet is nothing more than a tuned length of tubing, an expansion chamber to act as a burner can, fuel delivery system, ignition source, and a reed valve like that found on a two-stroke engine. Upon start-up the ambient pressures and temperatures are equal inside and outside of the engine — but when combustion is fueled inside the tube, and air is fed one-way through the valve, a harmonic pulse is initiated that sustains the engine.
As the air/fuel burns it expands before being necked down through the outlet. This compression accelerates the gasses and the velocity combined with a little help from Bernoulli’s principle creates a low pressure which draws in more fuel. Similarly to how a properly engineered exhaust system functions on a car engine, exhaust pulses are designed to evacuate the burned gasses and leave a low pressure in the cylinder in preparation for the next charge.
This video example demonstrates the simplicity of a valve-less pulse jet engine — which believe it or not has no moving parts. The theory and function remain the same as the valved engine but the system must be tuned in length to properly balance the give and take of intake and exhaust pulses while perpetuating operation as long as fuel is supplied.
Ever the mad scientist/lovable anarchist, Furze opted to point his massive jet to the east and his French neighbors. The deafening roar of the jet is sublime and profane simultaneously — and we love it. The orange glow of the engine reminds us of the intensive thermal energy fueling the expansion and growling from the flared trumpet like some kind of otherworldly beast.
Without any sort of accessory or drive possibilities the pulse jet is good for one thing only — thrust! Although the physics are a little tricky to wrap your head around, and Newton’s third law, “For every action there is an equal and opposite reaction,” still applies, the valve-less pulse jet will propel whatever you are possessed to attach it to — be it a go cart or airplane.