Pulse Jet Engine Question

When I was younger about 1966 the local hobby shop had a pulse jet engine with NO air intake and NO reed valves. It came with box and instructions. I can not remember who made it. The engine was bullet shaped with no air intake at all. The combustion chamber was about 1 1/4" diameter with a model airplane glow plug in the side, fuel connection, tire pump connection. I can not remember what type fuel it used might have been alcohol or model airplane fuel. The instructions said connect the fuel line to the fuel tank, connect the battery to the glow plug, pump the tire pump and the engine will fire. Pump the tire pump several times and when the engine gets hot it will run on its own. Exhaust pipe was about 7/8" diameter maybe 1" dia at the most. Total length was about 16 inches long. I remember thinking, this thing won't work. Does anyone know anything about this engine?

When I was in college I did some research on Pulse Jet engines. I found some excellent information in the SIU college library. After WWII the US did a lot of research on pulse jet engines. One of the engines shown in the book had no air intake and no reed valves. It said that when the engine fires the exhaust blows out of the exhaust tube producing a vaccuum inside the engine. The vaccuum will suck in more fuel. The fuel line has a one way check valve. The vaccuum sucks air into the engine backward through the exhaust pipe where it mixes with the fuel and fires again from the heat of the engine. It also said this engine is not as powerful as an engine with reed valves the main advantage is the engine has no moving parts.

Ron B.
F4Fguy

I don't know the specific engine you remember,but there were several model engines like that.I wasn't aware that any had reached hobby shop outlets,as most were mail order,cottage industry types.The principle is sound(no pun intended)and was even tried "full scale"for drones,missles etc.

The principle is the same as the Dynajet.It's basically a tuned pipe with the frequency tuned to evacuate the burnt gasses and on the return wave ram fresh air and compress it while mixing with fresh fuel to start the next cycle,pretty much the same as a tuned exhaust does.The "pump until it's hot" requirement is to stabilize average gas temperature to bring the wave speed to the frequency of the pipe.Therein lies the big problem(besides noise) with pulse jet engines,they only run at one speed,determined by the acoustics of the pipe.I must add that at least one developer claimed to have over come this drawback by throttling the fuel supply.

Operation sounds very similar to that of a "Pop-Pop" boat. The ones you run with a candle under a flexible boiler and 2 tubes running out under the water.

There was also a jet made from a CO2 capsule. You filled it with fuel, lit a fire under it, and it would squirt fuel out into an "augmenter tube" where the fuel lit off, warming the air and producing a teenie weenie amount of thrust. Apparently all it was good for is swinging itself around on a well pivoted and counterbalanced arm.

Pop Pop Boats! I played with those in the bath when I was a little kid. I remember I liked going shopping with my mom as I usually got a Pop Pop Boat or a nickle glider. If I was really good I got one of the fancy, $1.19 rubber-powered planes that even had wheels!

Cheers,

>Operation sounds very similar to that of a "Pop-Pop" boat.
>The ones you run with a candle under a flexible boiler and 2
>tubes running out under the water.
>
>There was also a jet made from a CO2 capsule. You filled it
>with fuel, lit a fire under it, and it would squirt fuel out
>into an "augmenter tube" where the fuel lit off, warming the
>air and producing a teenie weenie amount of thrust.
>Apparently all it was good for is swinging itself around on
>a well pivoted and counterbalanced arm.

My buddy once installed one of these Co2 / Augmenter Tube motors, made by the "MEW" Company (Minnisota Engine Works) I think, in an aluminum ice cube tray ..... he then set the whole rig in his bathtub of dead calm water ..... the engine was totally doing it's thing and the ice tray remained absolutely motionless ...... apparently this motor develops zero thrust?! I have a spanking new one somewhere in my collection, I will post a photo later.

MEW engine .... photo

>MEW engine .... photo

Tell me about this engine.
How does it work?
What type fuel does it use?

I assume the pan on the bottom is a heater for the engine. Fill it with fuel and ignite it sorta like the old time gasoline blow torch use to work.

I saw one of these engines sell on ebay about a year ago. The final bid price was quite high. I placed one rather low bid. This is not the engine I remember from the hobby shop.