Pulsejet engine!

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I built this little pulsejet about 3 years back. It was one of my first TIG projects. I found it in the garage today and thought I'd share some pictures with you guys. It's all 304SS, the straight sections are 20ga tubing and he cones are made from 22ga sheet. It runs on propane. Puts out about 5lbs of thrust, be good for a model plane. It's 30" long, 2" diameter at the tail, and weighs about 2 pounds.This little guy is SO freakin loud... You can hear the echo for a good 3 seconds after the engine is shut off. I'm sure people 5 miles away were wondering what that god awful noise was.Here's some pics.Here it is running.Here's what happens when you give it a little too much fuelMiller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:HOLY CRAP!!!!!Did you make sure to donate to the volunteer fire dept. this year??Is the fuel line wrapped around the tube in order to vaporize the LPG?Man, that's somethin' else.  Have you thought about cannons?  Those little signal cannons are pretty neat too."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Hey farmersamm. On a larger engine, that drinks liquid propane, having the fuel line coiled around the tailpipe to heat the propane is very beneficial. On this little engine it isn't needed at all, it was just an easy way to help stabilize the fuel line and injector. The engine gives off some wicked vibrations, and if the injector wiggles around it will kill the engine, resulting in a ginormous fireball out the tailpipe.You know, I built a little black powder cannon in high school metalshop, got an A for it.   Those were the good 'ole days. If a kid tried that nowadays he'd be arrested, and expelled, over a little noisemaker.       I wish I knew where that little cannon is, I haven't seen it in years.Miller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:Sounds about right.  Kids build a spud gun, and they wanna throw the kids, AND the parents in jail."Any day above ground is a good day"http://www.farmersamm.com/
Reply:I wonder if I should mount a pair of those on the back of my car?You know - To do my little part in expanding the use of alternate fuels.
Reply:Does wonders for tailgaters."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by denrepI wonder if I should mount a pair of those on the back of my car?You know - To do my little part in expanding the use of alternate fuels.
Reply:Jet powered canoe, what will you think of next.Miller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:Originally Posted by denrepI wonder if I should mount a pair of those on the back of my car?You know - To do my little part in expanding the use of alternate fuels.
Reply:First time I've seen Vise Grips griping a Vice!"One of the things we have to be thankful for is that we don't get as much government as we pay for." (Charles Kettering)Mitch 180 (NZ)Lincoln SAM-400-220 + ?-400 Fordson Major + 2 x Tractapac Humber 80 + Procut 40 PlasmaMiller Spectrum 375
Reply:Interesting.  But although the engine only weighs 2 pounds and you get 5 pounds of thrust out of it, you had to stick 40 pounds of propane tank there to get a few minutes worth of running!  Sort of kills the whole thrust-to-weight ratio needed for flying things.  The best laid schemes ... Gang oft agley ...
Reply:This is sick! I love it. To bad you dont have video of the first try. I picture the test crew a loooong way away.Airco 300 squarewaveMig welding center...Powcon sm300/LN 25Powcon sm200/PD lHypertherm PM 1100Miller AEAD 200LE W/LN25 FCand now another sm200 pd l combo.
Reply:Originally Posted by MoonRiseInteresting.  But although the engine only weighs 2 pounds and you get 5 pounds of thrust out of it, you had to stick 40 pounds of propane tank there to get a few minutes worth of running!  Sort of kills the whole thrust-to-weight ratio needed for flying things.
Reply:Originally Posted by Joe HsnipThey have also been used extensively for military target drones.During WWII the Germans developed a missile powered by a giant pulsejet. The V-1, also called a buzz-bomb.
Reply:I was a jet engine mechanic.I do not see any way for air to enter the engine.A pulse jet or ramjet as air coming in the front. The pulse jet as louvers that open and close.Interesting anyway.BTW  How did you figure out the lengths of the divergent duct,convergent duct, and pressure transducer?AWS certified welding inspectorAWS certified welder
Reply:Some months ago, a friend sent me a link to a site about these engines but I didn't save it. A quick search just brought up the following site which, at a quick glance, seems to have plans and formulas:  (It does look similar to the earlier site)http://www.pulse-jets.com/So far, I've resisted getting started with this too.
Reply:Donald, this is a valveless pulsejet engine. It does not require the petal valves that a valved jet does. Fresh air enters through the short intake tube on top of the engine. That particular engine is based on a chinese design from the 1950's.Lots of people confuse them with ramjets, but they are almost nothing alike. For a ramjet to operate it has to be moving at a very high speed, most will only operate at supersonic speeds, there have been some (innefecient) subsonic designs though. A pulsejet can operate statically, and draws its own air. Proper acoustics is mainly what enables this. They are quite complicated, and very interesting. Valveless pulsejets operate with NO MOVING PARTS whatsoever, it's almost like magic.Pulse-jets.com has a wealth of information, by far the best place to learn about them.Last edited by Joe H; 09-26-2008 at 04:58 PM.Miller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:I wanna build one that will run on cordwood.I figgure if it won't work then at leaste I could get an alternate energy subsidy.