I dont build them, but I am very interestd in the workings, especially
pulse and ram jets, so simple. I noticed on a past scrapheap challenge
where the object was to build a jet dragster, that the Navy team used
what they described as a ramjet, with the input as well as the output
facing rearwards. The simple diagram showed a restricted pipe wih no
valves in front, so it wasn't a pulse jet. I'm going quietly mad tring
to figure out how it worked!.
Anyway, don't think you are any more nutty than the American scientists
who've just done a couple of amazing things with scrams.
Nunce excretia in extractum est. (Appropriate this thread ?)
"Tom Jacobs" wrote
I didn't see that episode, but what you describe does sound like a type of
Did it have a short input pipe and a long output, connected by a U-bend and
both pointing rearwards?
If so, the working priciple is about as follows (I think):
Fuel is injected and ignited near the bend. Initially, this only goes
"whoosh" in both directions until the available oxygen in the pipe has been
consumed. But because the iput/output pipes are of unequal length, the blast
of hot gases will set up a draft through the pipes, as it quickly vents
through the intake pipe but has some way to go in the longer output. It's
kind of like a ram charger, if that makes any sense; it relies on the
momentum of the blast to keep going down the pipe for a short while after
combustion has ceased, thus setting up a draft that sucks fresh air in
through the intake.
As fresh air then enters the combustion area and mixes with fuel, the
process is repeated, and if everything is properly tuned it will start
running at a steady (and very noisy) pulse with a fair amount of thrust
The main problem with these, from a propulsion standpoint, is that the air
intake has to point rearward in order to produce any thrust at all since it
blows in both directions. As you gain speed, therefore, it will extinguish
itself from lack of air. Apart from that they're brilliant machines: no
moving parts, and lots of noise ;-)
The only real engineering challenge when building one is AFAIK to get the
lengths and diameters of pipe just right, as it has to be in tune almost
like an organ pipe. Also, the fuel to air raio must be just right if you
want it to start from cold; I guess a blower could be used to get it going a
bit easier though.
Many thanks to both Amund, Duncan, and everybody else for information. I
have been going on about that program to friends and anyone else who
would listen, since I saw it. I shouldn't have to eat too much humble
pie though, as I don't think very many of them were actually listening.
Thanks again, and, as I also tell everybody I know, this is THE site for
informative help and assistance.
Nunce excretia in extractum est.
The expert on that show was Bruce Simpson, who runs a news site at
and has a pulsejet powered gokart of his
very own. I wouldn't drive it... Drop him a line at editor at
aardvark.co.nz. Top bloke
Those jets work on a tuned pipe principle, so there is no need for
valves - the harmonics do all the work.
Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane
I have a catapult. Give me all the money, or I will fling an enormous rock at
Some useful links.
Many (small) turbine links:
-> select from options in blue frame to the left
You guys do know that the first turbine for RC planes, built by Kurt
Schreckling and published in a German RC magazine in the mid 90's, had a
compressor made out of plywood and carbon?
Met vriendelijke groet ;) Ron van Sommeren
near Nijmegen, the Netherlands
----- Original Message -----
From: "Al Doyle"
Sent: Thursday, April 08, 2004 1:25 AM
Subject: Any other Jet Engine builders?
haha, you guys are funny. No offence but you dont really have a clue what
you are on about.
It was a pulsejet but a valveless. It was of a lockwood hiller design.
It works by injecting fuel into the combustion chamber and ignighting it,
this goes wish out boat ends and creas a vcaume in the combustion chamber
were air is sucked in and mixed with fuel and automaticly ignights. all the
exolosions make a pulsing noise hence the reason it is called a pulsejet!