Robert “Bob” Maddox builds pulsejet-powered machines—including the three-engine kart called the Beast. A pulsejet is an air-breathing engine that produces thrust through repeated combustion; it is not a rocket and does not carry its own oxygen. The Beast is less a practical road vehicle than a homemade engineering spectacle, built around the heat, noise and unusual character of its engines.
How Robert Maddox got into pulsejets
Maddox’s official biography traces his interest in thrust-powered machines to childhood: at age ten, he built rocket-powered balsa airplanes using Jetex motors. He says his focus later shifted to pulsejets after a skydiving experience in 1991 brought back a memory of seeing a schematic for the German V-1’s pulsejet engine.
In an EngineLabs profile, Maddox described the idea that came to him during a freefall: “In the early nineties I started sky-diving and I was thinking (in freefall) I need a jet or rocket on my chest to go faster!” The profile says he learned from photographs, articles and model examples rather than formal engineering training, then developed his own engine designs and approaches to fabrication, fuel delivery and ignition.
EngineLabs reports that Maddox described an early engine as producing 50 pounds of thrust. That is his account of a particular engine, not an independently verified or current performance figure. His projects have also included a mini bike, a twin-engine trike and a jet dragster, according to the Maddoxjets video listings.
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#1 Best Overall
- ⚡ Experience Raw Pulse Jet Propulsion – Harness the simple, powerful principle behind early jet technology! This pulse jet engine delivers around 500 grams of thrust with higher combustion efficiency than a standard internal combustion engine. Feel the power and hear the distinctive roar of a real, working jet engine designed for advanced aerospace and vehicle models.
- 🛡️ Advanced Lightweight & Durable Construction – Engineered for performance and resilience. Made from carbon steel and aluminum alloy with high-temperature resistant 304 stainless steel pipes and valve plates, it's built lighter and tougher. The black high-temperature coating and enlarged fuel injection chamber are designed to maximize thrust and durability for the enthusiast.
- 🛠️ Complete Ready-to-Run Kit for Immediate Operation – Get started with everything you need. This RTR (Ready-to-Run) version comes as a complete set including the engine, 20 complimentary high-temperature valve plates, fuel tank, hose, atomizing sprayer, ignition starter, and battery compartment. Just add gasoline and batteries to begin.
- ⚠️ For Expert Use Only – Critical Safety Information – This is a serious, high-performance model for experienced hobbyists only. It produces extremely loud noise (~130 dB) and must only be used outdoors. Gasoline is hazardous; operation requires a safe, open area free of flammables and expertise in model modification. The valve plates have a limited lifespan (approx. 1-5 minutes of total runtime).
- 🔬 A High-Impact Educational & Display Piece – An awe-inspiring model for understanding jet propulsion. It serves as a profound scientific educational tool and a striking desktop display for serious tech enthusiasts. Ideal for inspiring advanced projects, but recommended only for those with significant mechanical experience and understanding of safety protocols.
What makes a pulsejet different from a rocket?
A pulsejet creates thrust through intermittent combustion: air and fuel burn in repeated pulses, sending hot exhaust out of the engine. It breathes atmospheric air. A rocket, by contrast, carries the oxidizer needed for combustion, so it does not depend on drawing oxygen from the surrounding air.
Pulsejets are often described as simple engines with few or no moving parts. That simplicity does not mean every design is identical. Maddox has built both valved and valveless engines. EngineLabs describes his valved designs as using custom reed-valve assemblies, with machined cages and spring-steel reeds; it also discusses fuel-dispersion and ignition challenges. Those details describe Maddox’s engineering work, not a universal pulsejet layout or a do-it-yourself construction guide.
Rank #2
- The pulse jet engine is a type of jet engine known for its simple structure and higher efficiency compared to conventional engines. Initially used in missiles, it can be applied to various aerospace models and vehicle models.
- Made of carbon steel and aluminum alloy for enhanced durability and lighter weight. The hollowed internal channels adopt stainless steel covers, resulting in a weight reduction of 4 grams. High-temperature resistant 304 stainless steel pipes reduce weight by 15 grams.
- Featuring high-temperature resistant 304 valve plates for extended lifespan by an additional minute. Designed with a black high-temperature resistant coating for an attractive look. The enlarged injection chamber provides a thrust of around 500 grams, aiming to offer enthusiasts a lightweight, high-thrust pulse jet engine.
- Wide Applications: An amazing model suitable for tech enthusiasts, family, friends, and childrens holiday presents. It serves as both a scientific educational toy for understanding aircraft engine principles and an inspiring tool for kids science projects, nurturing curiosity and creativity. Perfect to be a cool desktop art piece as well.
- Notes: Loud noise at 130 dB. Recommended for outdoor use only. Avoid igniting high-pressure outside the engine, because it could catch fire. Expertise in model modification is necessary for installation. The valve plate lifespan for this engine is appr 1-5 minutes. Exercise caution for individuals with limited manual dexterity.
The Beast’s engines are tube-like, and Road & Track’s January 8, 2025 feature describes them as having no moving parts. The sound is part of the appeal: Maddox told the magazine, “The pipes are musical instruments, basically.”
Inside the Beast pulsejet go-kart
Road & Track describes the Beast as a go-kart-like vehicle with three pulsejets mounted behind the driver. Its reported components include a homemade chassis, go-kart wheels, rear suspension assembled from go-kart parts, steering and disc brakes. A heat shield separates the driver from the engines.
Rank #3
- The pulse jet engine, a type of jet engine, with a simple structure and higher combustion efficiency compared to regular internal combustion engines, was initially used in missiles. Suitable for various aerospace and vehicle models.
- Made of carbon steel and aluminum alloy for enhanced durability and lighter weight. The hollowed internal channels adopt stainless steel covers, resulting in a weight reduction of 4 grams. High-temperature resistant 304 stainless steel pipes reduce weight by 15 grams.
- Featuring high-temperature resistant 304 valve plates for extended lifespan by an additional minute. Designed with a black high-temperature resistant coating for an attractive look. The enlarged fuel injection chamber provides a thrust of around 500 grams, aiming to offer enthusiasts a lightweight, high-thrust pulse jet engine.
- Easy to Operate & Long-lasting: After adding fuel and installing the battery, securely start the engine. Comes with a complete set of equipment: engine, battery compartment, fuel tank, fuel hose, etc. Prepare batteries and fuel are the only additional requirements.
- Wide Applications: An amazing model suitable for tech enthusiasts, family, friends, and teens holiday presents. It serves as both a scientific educational toy for understanding aircraft engine principles and an inspiring tool for teens science projects, nurturing curiosity and creativity. Perfect to be a cool desktop art piece as well.
The same feature says the kart starts on gaseous propane and uses liquid propane and diesel for acceleration. These are details of the Beast as covered in that report, not a fuel specification for all Maddox engines or pulsejet vehicles. The engines produce substantial heat and noise; Maddox summed up the trade-off to the magazine: “They’re inefficient, and they make lots of noise and heat.”
The vehicle’s homemade chassis and adapted kart hardware make it look familiar at a glance, but its three-engine arrangement changes the experience entirely. Maddox’s account, as reported by Road & Track, frames the build around the enjoyment of making and driving it—not fuel economy or everyday transport.
Rank #4
- ✤The pulse jet engine is a type of jet engine known for its simple structure and higher combustion efficiency compared to conventional internal combustion engines. Initially used in missiles, it can be applied to various aerospace models and vehicle models.
- ✤Through moving parts and a mechanical structure started by electronic devices, the model can demonstrate and showcase the working principle of the pulsating jet engine. You can start the model and observe the operation of the jet nozzle, the combustion process in the combustion chamber, and the exhaust from the tailpipe.
- ✤High-temperature resistant valve discs are selected to increase usage life by around 1 minute. The engines exterior is made of aluminum alloy, creating an aesthetically pleasing appearance. Enlarging the fuel chamber space allows for a maximum thrust of approximately 2000G, aiming to provide aviation model enthusiasts with a lightweight and high-thrust pulse jet engine.
- ✤This engine model is easy to operate & durable, after adding fuel and installing batteries, secure the engine for startup. The package includes all the necessary equipment: engine, battery box, fuel tank, fuel lines, etc. Only batteries and fuel need to be prepared.
- ✤This is an incredible model suitable as a holiday gift for technology enthusiasts, family members, friends, and children. It can be used as a scientific educational toy to study the working principle of aircraft engines, provide material for childrens science projects, inspire curiosity and creativity, and serve as a cool desktop decorative art piece.
Materials, plans and what is not established
EngineLabs says Maddox rolled sheet made from 304 stainless steel during his development work; Road & Track also mentions stainless steel among the materials used in his builds. Neither source establishes a universally suitable sheet thickness or a material specification for someone else’s engine project.
Maddoxjets’ official site promotes engine kits and plans. WIRED also reported on April 26, 2011, that Maddox sold do-it-yourself plans for engines and projects. Those sources establish that plans have been promoted and sold, but they do not establish current prices, stock, or support terms.
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- 🚀 Micro Pulse Jet with 500g Thrust - This ready-to-run micro pulse jet engine delivers approximately 500 grams of thrust, built from lightweight carbon steel and aluminum alloy. Hollow stainless steel channels and high-temperature 304 stainless steel reduce weight, making it perfect for model power systems and striking desktop displays
- 💨 Complete RTR Kit, Just Add Fuel & Batteries - The box contains everything needed: the pulse jet engine, electronic ignition starter, fuel tank, fuel hose, atomizing sprayer, and battery compartment. Simply add gasoline and batteries, then start the engine effortlessly—no complex assembly required
- 🔧 Durable Upgraded Components - Equipped with high-temperature resistant 304 one-way valve plates and a black heat-resistant coating for extended lifespan. An enlarged fuel injection chamber ensures reliable performance. Includes 20 complimentary spare valve plates to keep you running
- 🎓 STEM Learning & Eye-Catching Display - Serve as a scientific educational toy to demonstrate real pulse jet principles, inspire curiosity, and support STEM projects. Also a captivating desktop art piece that showcases internal combustion engineering in motion
- ⚠️ Safety & Operation Advisory - Produces extreme 130 dB noise – outdoor use only. Gasoline fuel is hazardous; keep away from flammables. Valve plate lifespan approx. 1–5 minutes. Requires modification experience; not suitable for those with limited dexterity. Clean fuel nozzle promptly. For experienced hobbyists aged 15+
The available reporting does not establish an independently measured top speed or performance test for the Beast. Its reported engine details and layout are useful for understanding the build, but they should not be mistaken for a verified speed record or a complete technical specification.
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