Valved Reynst

[PyroJoe]

Here is a concept for a valved Reynst style jet. I wanted to see the opinions on it, and if any one has tried this avenue yet.

Thanks in advance,

Joe

[pezman]

Hey, that's pretty cool and it just might work.

It is more-or-less the same idea as a fog-horn, only in reverse. In fact, it might be possible to build one of these from a fog-horn -- I think that the diaphragms are often metal.

[PyroJoe]

Good suggestion, I'll look into fog horns.

[larry cottrill]

I agree with pezman - that is a very sharp idea.

There is one possible problem: I think Mark has reported that jam jars with "oil canning" (popping in and out) lids don't work well. However, don't let that discourage you - even if it turns out not to work as planned, we could all learn some things from this if you're careful in reporting your observations. And it could work surprisingly well and astound everyone!

Good luck!

L Cottrill

[Rossco]

Just a little observation here.

The parabolic curved horn, or just megaphone shape, resonate in their inteded use best from the small end out to the bell. Obvious.
BUT in terms of a pulse jet, it seems to resonate better ass about! Intake at the capped off large end.
Now, this could be a good thing for a reynst, very interesting.
The large end would definitely need to be the top. As far as my experiments have gone, they dont go well with an overly large base.
I would say that the mixing votex over expands and goes caotic... or something.
The small end really is very small in a horn tho, enough for fueling?

Let me know if you cannot find one. I have two nice chromies on my truck, and i could do some NON DESTRUCTIVE testing.
Otherwise, i would be very happy to see somone else do it before i even pull mine apart.

Rossco

[Mark]

A lot of glass jam jars run fine with flexing lids, but something like a soup can that has a flexing top and flexing bottom, especially on the larger cans, that seems to be a killer for resonance. But perhaps nothing is written in stone, a top and bottom lid might work together to sustain feedback, I just haven't found that to be the case with soup cans and the like. I have also found that some thick lids ruin the jam jar effect too, if you every come across a quarter inch thick plate of steel for a lid. Maybe the thickness of the hole doesn't swirl/mix the air flow as well. I don't know.

I had arranged a typical oil can with 4 inch snorkel and when I lit it, the bottom would flex and build feedback so fast it just went off like a gunshot when I lit it, even with a seeming ample short exhaust tube that you wouldn't think could ever produce such a deafening bang. Nothing confining about the arrangement in the least.

In the same way those of you who have toyed with a Dynajet and tire pump might have witnesses how loud a single backfire can be when the jet is warming up and about to catch. There is something about the flexing reed that catches/tricks the phase in such a way. For if you just hold/seal your hand over the head of a Dynajet, just take the head off and mist it with methanol you can get it to crack/bang bark just by lighting the tail which is pretty loud, but you can't get that certain gunshot high amplitude report that sounds like a heavy duty backfire report from some automobile.
Maybe Larry or other Dynajetters could add something to this, it's just amazing how loud a Dynajet can be with a single backfire when conditions are just right, it sounds as if the gunshot report was made from something much larger in size.

[PyroJoe]

I've never seen my jam jars/cans have that type of feed back.
That must be a sight.

I'll start work on the nozzle this weekend. Dust off the little lathe.

Here is another design, I've lobbed off the lower half of "de Laval Nozzle"

making a simpler design, should be self converging on its own.


My biggest concern is detonation. I plan to use less than the 7/16" diameter hole I normally use with a little larger chamber. Has any one had a detonation with these things?

I also haven't had much luck with snorkles, jars that will normally run till the break will only run a couple of seconds to flame out with a snorkle.

Some pointers on snorkles would be much appreciated.

Thanks for the comments, I'll post results as they occur.

[Rossco]

Detonation in a reynst... Detonation in anything pulsejetish, HA, i wish.

Rossco

[PyroJoe]

Detonation= Large combustion chamber + choked flow+ oxidizer in the fuel



One of the first DIY rocket engines of my youth detonated.

I was smart enough to keep behind a barrier while testing, but will never forget that first detonation!

[PyroJoe]

No oxidizers, No detonations, No worries.

[Mark]

The jam jar in the middle of the second picture, the kind of large one, is only rated for 5 atmospheres, so I have a very long wire and I stand behind a tree when I spark start it. I don't think it would blow up on me, but I like to play it safe just in case. In the past I posted a few good graphic stories of people dying from cutting into a 55 gallon drum that just had window washer fluid concentrate vapor or some other combustible.
The beer keg runs poorly as a jam jar, chuffing slowly on a liter or so of methanol in the bottom, but the initial whoosh is impressive. It chuffed long enough to heat up and darken or form a slight gold sort of patina on the sides of the keg. The neck has this rim in it, you can kind of see it in the first picture, that I think is messing up the in/out action. I either have to sleeve in a snorkel to make the throat flush or grind out that inner lip. At least it would be worth a try.
Just keep in mind, deflagrations or confined gases can go bang in a big way if you exceed the strength of the container. I once had a large paper mache' ostrich egg. I drilled out a half inch hole in the pointy end and misted it with methanol. It went bang in my hand, stinging the heck out of my fingers when I lit it with the other hand, thinking it would jam jar instead of blow/split apart. It struck me as funny although I could have lost an eye, very unlikely but maybe. ha
Mark
http://www.chemaxx.com/explosion14.htm

CAUSE OF DEATH
"The medical examiner’s report stated the probable cause of death as severe traumatic head injuries."
http://www.public-health.uiowa.edu/FACE ... T-033.html

[PyroJoe]

BEJEEEEZ thats a big keg.

[tufty]

Mark, has Bruno been visiting you? Tell the truth now :)

[Mark]

The keg is big for a jam jar but it's not really a big keg. It holds 7.75 gallons or ~29.3 liters. I was just reading on the keg that it will rupture at 60 psi, closer to 4 atmospheres now that I think about it. I don't know if that means the top or bottom flies off or what. ha
Since the little narrow keg is 11 inches wide, I would say there is roughly 5,700 pounds of force on the top or bottom at 60 psi, but who's counting.
Danger Will Robinson. ha
http://crave.cnet.com/8301-1_105-9726954-1.html
http://youtube.com/watch?v=xK0Wk7mBKLs& ... ed&search=

[Eric]

Yea I learned a good thing is to make the top plate removeable, and not even really mounted on, when dealing with big jam jars.

A metal plate with a hole drilled in it, held down with some weights works great, if the pressure gets too high, the top rises up and lets out pressure, then the plate lowers back down, sort of acting as a giant pressure release / valve and keeping it from turning into shrapnel

I had a little 1 gallon stainless pressure sprayer that I tried to run as a propane jam jar, made a deafening boom, and my ears were ringing for quite some time like a grenade went off beside me.

Eric