metal jam jar experiments

[steve]

I made a simple jam jar out of sheet metal in school today and I plan to do some experimentation on it to see what I can do to increase the thrust. I found the easiest way to take thrust measurements is simply to put the engine on a digital scale, zero it, then light it. It currently produces about .2 oz of thrust at about 20-25 cycles per seccond.

I ran it a couple times on methanol after school and was pleased to finally have a jar that wouldn't shatter after 8 secconds. Anyway, I will try to put an anular fuel feed on it tomarrow and test it with diferent fuels. then I will mount various pipes and augmentors over the hole and see what happens!

If you get bored and feel like building one of these it is 5.5in tall and has a diameter of 3in with a 31/64in hole (1/2in would probbably also work)

I know this isn't particularly exciting or revolutionary but I'm having fun and I might just learn something.

[steve]

I will be welding on the annular lip feed system on monday and testing it with several fuels (acetlyne, mapp, propane, methanol gravity feed) to see which will generate the most thrust. before I can do that, I need some Idea of how to start it. should I pour methanol in the bottom and then gradully introduce the other fuel while it is running, or can it be started by turning on the gas and lighting it quickly?

[Mike Everman]

Hey, I'll make one too. Try making a disk out of cotton fabric, soak in meth and let it plaster itself to the bottom of the jar. You can reach in and flatten it with a pencil, it sticks nicely. It is the quick way to make it run on it's side. I suspect that when it gets hot enough, you could feed the "wick" on the bottom just about any liquid fuel by way of a needle valve on the bottom.
We'll have to make some rc cars for these to power!

[steve]

Glad to see you are interested! will you be using a lip fed system or the soaked fabric method?

this thing is great for demonstrations- I fired it off at least 5 times during school on friday. It is really fun to see people's reactions to it, especially when I don't tell them what it is going to do before I light it. (hehe)

when you build it I reccomend that you don't make an extra large base like I did and that you use an oxy torch to weld it. I did this with the micro reynst and it came out much better and had no leaks.

[inventor30]

Sometimes we dont know what we have.......
I had a home made wood stove built out of a 30 gallon oil drum (in 1979)
It had a 6 inch stove pipe connected to the top, which ran no more than 8 ft to a chimney (concrete) As it was getting cold, and I was nearly out of wood, I cut an old refrigeration tank in half, put it inside my wood stove and poured in about a gallon of used motor oil which came from the crankcase of my auto. Now for all you who dont know these things, remember the following. The refrigeration tank was essentially a 3 gallon thin steel pail, setting inside the wood stove with a gallon of oil in it. Second, motor oil will not burn, without some coaxing. So I built a small wood fire outside the pail and threw a rag into the oil in order to light it. I closed the door and was fine for about 10 minutes..........when I noticed the stove glowing(it never did that) so I looked inside...the oil is biling furiously...the rim of the pail is glowing...and things seem to get hotter by the second.......so I did the only thing that seemed reasonable at the time......I closed the air inlet on the stove door. That was the first time I ever saw an oil fired valveless pulse jet......The stove rattled. jumped thumped, and squirted fire around the door in a regular thump thump thump pattern, as it sent perfect black smoke rings up the chimney. I solved how to make a valveless pulsejet run on motor oil that day.....and thought for sure I would burn the house down. I hosed the stove down with water, and down the chimney and eventually got it cooled down and the fire out. Took me 25 years before I actually understood what happened that day. JC

[steve]

First of all welcome to the forum and seccond, WOW! that must have been amazing to see! How loud was it?

Have you built any pulsejets (besides your accidental one) since then?

[Nick]

Hi, and welcome.

Like the Jam Jar jet, you might like to see the videos i made of mine which include annular meths delivery.

have fun

Nick

[Nick]

sorry forgot the link

here it is http://www.pulseweld.dsl.pipex.com/videos.htm

[steve]

I've seen those videos, incidentally they were what inspired me to build my reynst!
Unfortunately my attempts to run it with anular lip feed were a dismal failure. When I turned on the fuel it just flooded in, the engine sputtered and died while spraying methanol everywhere. Could you explain how your system works so well?

[Mark]

Sometimes we dont know what we have.......
I had a home made wood stove built out of a 30 gallon oil drum (in 1979)
It had a 6 inch stove pipe connected to the top, which ran no more than 8 ft to a chimney (concrete) As it was getting cold, and I was nearly out of wood, I cut an old refrigeration tank in half, put it inside my wood stove and poured in about a gallon of used motor oil which came from the crankcase of my auto. Now for all you who dont know these things, remember the following. The refrigeration tank was essentially a 3 gallon thin steel pail, setting inside the wood stove with a gallon of oil in it. Second, motor oil will not burn, without some coaxing. So I built a small wood fire outside the pail and threw a rag into the oil in order to light it. I closed the door and was fine for about 10 minutes..........when I noticed the stove glowing(it never did that) so I looked inside...the oil is biling furiously...the rim of the pail is glowing...and things seem to get hotter by the second.......so I did the only thing that seemed reasonable at the time......I closed the air inlet on the stove door. That was the first time I ever saw an oil fired valveless pulse jet......The stove rattled. jumped thumped, and squirted fire around the door in a regular thump thump thump pattern, as it sent perfect black smoke rings up the chimney. I solved how to make a valveless pulsejet run on motor oil that day.....and thought for sure I would burn the house down. I hosed the stove down with water, and down the chimney and eventually got it cooled down and the fire out. Took me 25 years before I actually understood what happened that day. JC

That's a good story. I once heard a very similar account in an old western novel by Zane Gray or Louis L'Amour of a fellow who built a roaring fire in a pot-bellied stove with chimney pipe. He slammed the door shut on the stove and a terrible howling feedback sprang to life, the door acting as a valve in some way resonating back and forth as well. Ah, nothing like a good Western involving pulsejet-like activity in a quiet old cabin in the desert or something. Almost as good as box of bullets in a fire to wake one up.
I've read of a college demonstration of a 4 inch diameter verticle duct perhaps 15 tall with a large Bunsen burner inside a 1/4 of the way up it. It purrs away softly until a tuning fork of a certain frequency is struck from clear across the room. This little tuning fork kicks the duct into a terrible roar vibrating chalk boards and frightening the spectators. I read this demonstration in book at our university when searching for books on sound.
In a way, I guess a large valveless pulsejet could do "kind" of the same, purr with an abundance of propane sprayed into it until a quick blast of starting air sets up a resonating feedback or typical running mode. It would be neat if there could be a way to conjure a pulsejet to life using a tuning fork though, singing flames of some sort.
I once made this 11 inch long pulsejet with a .003ths single flapper reed. I'd prime the inside of the jet and light the tail. It would gurgle or buzz quietly like a bumblebee was caught inside it, running on fumes. Then after some time, perhaps 10 seconds, the flame would advance up the tail, and kick it into a really impressive whine. You could often hear the frequency walk up as the flame was able to advance, or go from the purr to exponential in a quick choke or two. The little reed was very sensitive I guess and admitted/flexed just enough air in the intake to keep the flame in the tail at bay for awhile. Remember, I would just light the tail end after priming the jet. The reed valve plate was just a washer with a screw to hold the petal valve down with. I polished the washer to a mirror smoothness though. I later made my Logan out of this same size of combustion chamber, 3/4 inch galvanized plumbing pipe, actually the little sections of pipe are referred to as nipples.
Mark

[Nick]

I've seen those videos, incidentally they were what inspired me to build my reynst!
Unfortunately my attempts to run it with anular lip feed were a dismal failure. When I turned on the fuel it just flooded in, the engine sputtered and died while spraying methanol everywhere. Could you explain how your system works so well?

Hi Steve,

Glad you like the vids. Ok the trick with fueling the pot is to reduce the flow of fuel to the barest minimum. it isnt evident on the video but i have a needle valve controlling the flow. The way forward for you i think is to start off where i did and get a small pipette so you can drop fuel one drop at a time at the lip of the pot once its already running on some meths you put in there earlier, some meths will spray out again but some will be drawn into the pot and it should "rev up" as each drop is delivered. Once you have satisfied yourself about how much fuel is required get a steel washer with a central hole the same size as the hole in the pot and drill a 1.5mm or 2mm hole through it near its outside edge, this is to fit a small feed pipe into, i used copper from a model shop as its cheap and easy to use and bend. Now stick the washer on top of the pot with the holes aligning, just use silicon to attach it and seal around the outer edges, there should be a very small gap under the washer so that fuel entering via the feed pipe can spread around the pot intake and is sucked into the pot. adapt the feed pipe to run from a resevoir of fuel so its gravity fed and maybe use a bit of soft plastic pipe in lie somewhere so you can clamp it to control fuel flow. Next you need to think about cooling.

Have fun and keep us posted.

Nick

[steve]

Thanks for the info!

BTW the salt idea was really great, I tried it out and made a video- enjoy!

[Mark]

Very nice Steve, I liked the sodium yellow demo very much. Boric acid powder, cheap and at any pharmacy, makes a nice green and copper sulfate is nice too. Calcium salts can make a good red.
Nick, I like your chimney and pulsating tubing effect. My little Logan use to pulsate my pink colored silicone tubing with methanol when I bled the pressure off the tip of the head of the jet to feed alcohol into the side port. With larger tubing it would rev up and down erractically from the springy fuel feeding.
Mark

[dangerranger01]

So, how do you make one of these jam jars? I think it is an awesome loking/sounding jet. Thanks in advance

Grant

[EDIT]What i mean is how do they work, can i use just any jar put a hole in it, stick some methonel in it and light it on fire? sorry

Grant

[Tom]

Grant,
look around. If you are still oblivious to the numerous instructions within all of these threads, use the search. Also, we have the option to edit previous posts, as i have done with yours, see the difference?

Tom