Mike's Build Log

[Mike Everman]

Cool, Mark, I'd love to do some experiments with with one of your snorkelers!

I've got a new massive spreadsheet developing for pulsating combustor design. I've been getting cold and hot frequency measurements and matching them with theory.

One of the interesting conclusions is, for my family of pocket jets in several scales, the cold frequency is 85% of an equivalent length straight pipe, and the hot running frequency is 1.6x that, within 4hz.

Having a reliable snorkeler would let me check the Helmholtz side of the sheet. I'm just now recording jars without a snorkel to check against the Ocarina frequency equation, but i need fresh fuel and less humidity for some strong runs. My salsa bottle jar is about 300hz cold and runs weakly at 80hz.

So far its each to its own equation, straight pipe pulsejet to simple open pipe equation, jamjar to an Ocarina treatment, and a snorkeler to Helmholtz equation. I'd like to find a grand unified theory that blends them all, Trying for a super Reynst pot.

[Mark]

Tonight I ran a 20 ounce paintball snorkeler holding it sideways maybe at a 30 degree angle in my hand with a hand towel for insulation. You can get a feel for how it runs that way tilting it up or down ever so gently to speed it up or make it more steady. Then immediately after it stopped after a good run I relit the snorkeler with a Bic lighter as there's invariably fuel left over and it's evaporating fast, maybe close to boiling inside the bottle thus making a tall candle flame effect if you were to just set the tank on the table. It kind of makes a woof sound when you relit it, lighting the escaping fumes that is. But the neat part is at night if you tilt this molitov cocktail looking bottle sideways preferably out in the yard, the methanol in the bottle flashes when it hits the hot snorkel and you can make a good 10 foot long fireball. This one only had a 6 inch snorkel but with the 10 or 11 inch snorkel I'd say you could effortlessly conjure a 15 foot long whoosh fireball flamethrower that would startle the uninitiated, just by relighting and tilting the bottle after a long run, the long run which gets the bottle and snorkel really hot. You can actually feel some thrust from the whoosh.

I was toying with that little sound augmenter today too, just to familiarize myself with it again to see what the ideal distance is from the tip of the snorkeler where it makes the most sound so that you could experience it. I haven't played with the snorkelers in several months. It quickly occurred to me it's about three inches out that the sound becomes painfully apparent and it dawned on me it won't take you anytime at all to find the sweet spot, the augmenter isn't fussy, just hold it in your hand and funnel that snorkeler air through it. I don't know where that sound comes from but it's stunning, like flipping a switch. All the augmenter is is the top two inches of an aerosol can, that folded seam or ring and a few inches of necking can wall. I wish though it was winter because the snorkelers make a much more aggressive sound and are quite snappy in cool dry air. In the humidity they don't run nearly as long and bog down sometimes but you should be able to get a smile from the snorkeler effect regardless. You can also cup your hand around the exhaust about 4 inches out, make your hand into the shape of the letter C and then it's fun to modulated the sound by changing the shape of your hand quickly back and forth or whatever tune you want to play. But the hand isn't nearly as loud as the aerosol can cone but your hand can make it noticeably squawkier than the plain snorkeler exhaust.

[Mike Everman]

Yes, augmenters weight heavily in my plan. That should be interesting. Any way you slice it, noisier means more thrust.

I just took a first step toward a closed end version of my pocket jet. Twin snorkels for you, Mark. ha
It's tough (or maybe impossible) to make it acoustically identical to it's valveless parent, my 5.4 lb pocket jet. A closed end only has the odd harmonics, and the pocket jet is strong in the second. My current theory is that this is a phantom strength, and that the intake and exhaust are alternating, making us think the second is strong.

This PLA material will warp in a warm car, but for a brief bark of methanol, it survives just fine. I did lose half an eyebrow trying to blow it out though!

It makes a nice bark at the end of this video: https://www.youtube.com/watch?v=QvW-uHTTerE

[Nick]

Hi all,
great work with the latest engine Mike- the Jam Jar /closed end concept is looking very promising.
Speaking as the layman's layman of course- ref the spinning action looks great! they are very picky about running but I wonder if this is a function of the liquid fuel being spun out to the sides and messing with the fuel mix.?
From my (very amateur) experiments I found you can run them on propane (20 mins was my best)- no easy by any means but possible.
Of course its a whole new can of worms trying to fuel with a gas from the bottom of the cylinder and with the rotational vortex induced into the fuel air mix by virtue of the spinning action - the mind boggles at the complexity of that.
looking forward to seeing more on the new engine!
Cheers
Nick

[Mark]

I think the twin exhaust idea in whatever perfected form will be a thrust maker. And It's sort of venturing into the typical intake/exhaust motif of a valveless pulsejet, the line of demarcation blurred. I remember some drawing of an elongated combustion chamber and two equal length and diameter exhausts at opposite ends, some valveless pulsejet design where the exhausts bent and point the same direction. It was on some single piece of paper with a bevy of valveless shapes that were said to run. The drawings struck me all the quirky ways you can bend and stick/morph pipes on a combustion chamber, sort of a tree of life for valveless pulsejets.

Along those lines and probably left field I noticed something long ago that was odd about a stubby zinc-coated/galvanized snorkel used for the piglet snorkeler. First a quick background clip.
https://www.youtube.com/watch?v=2Pp2CefdXVw

So I wondered if a shorter snorkel might by some miracle start to segregate inflow and outflow over time as it heats up as in this account. Maybe it was the sunlight playing tricks on my eyes or more likely I haven't thought this one out logically. I saved this long ago but never posted it (I don't think) because I wasn't sure what's going on. If I did post it a thousand pardons. So here it is ...

I was watching another youtube video on zinc oxide changing color when heated and it caused me to revisit my piglet snorkeler video out of curiosity. I vaguely recalled that the yellow color wasn't uniform. If you look at it at the 6 minute mark, the tube isn't yellow but around the 7 minute mark or so when I move to the other side there is a yellow color. So it seems possible that the galvanized snorkel is acting as a thermometer where the snorkel is segregating an in/out airflow. In the U.S. Navy's Project Squid papers there's some schlieren photography where they say as the exhaust is heading out the tail of a Dynajet and becoming rarefied, inflow is simultaneously occurring around the edges of the exhaust pipe choking the flame. At any rate it's not a slug of air going in in a perfect piston manner and then leaving in the same coherent fashion I don't think. There' s some obvious chaos too as you can hear random intermittent popping sounds in the combustion cycle.

So "perhaps" the Zn0 coating on the galvanized snorkel is acting as a thermochromic indicator, and that the hot exhaust is exiting more so to one side and the inflow taking another. There's this other convection idea with a candle where granted the in/out flow is at a much slower rate with the cardboard divider creating two snorkels in effect. But would a snorkel jet have this propensity to adopt the same duel flow scenario? Or what if by random chance one side of the snorkel heats up more than the other, would that start to reinforce a pattern of airflow where one side favors inflow and the other outflow? I guess you could gun the snorkel with one of those infrared thermometers to see if there was any truth to this supposition. It could be that the yellow is forming on one side for some other reason, but it's at least a curious little detail as to what might be going on. And then too, it seems possible a different length or diameter snorkel could set up an entirely different set of circumstances, not allowing for the same sifting and sorting if that's what's going on. Or it could be a combination of events, the pulsating combustion partially adopting one bias then another. Maybe after an initial circumferential inflow, the hot and cold gasses start to take sides.

Candle in a tube with cardboard strip
download/file.php?id=13207

Gray side
https://www.youtube.com/watch?v=KUYgTN1 ... 8GFAw#t=6m
The opposite side (yellow)
https://www.youtube.com/watch?v=KUYgTN1 ... 8GFAw#t=7m

As an aside, I was eating some oysters for lunch and recalled this. ha
http://www.healthaliciousness.com/articles/zinc.php

[Mike Everman]

Yeah, that candle in a tube sets up what they call a thermal syphon used in some geothermal systems.

The mind boggles at air going in one and out the other at the same time, which is certainly the case on the parent motor. Maybe its where this idea breaks down, as I just dont have enough volume to be springy enough for them to be simultaneous. Theres a glimmer of something here, but I don't know what it might be yet!

Hi Nick! Next is metal and propane fueling, so might be picking your brain there. I've been expecting to fuel it at the intake transition like a normal pulsejet, but its anything but normal and may not like that!

[Mike Everman]

https://youtu.be/LRFPkJVMt1M

The bark in slow motion. Very interesting things if you go frame by frame. A little butane ball of fire at the end.

[Mark]

Sizing up the 12 ounce thick aluminum paintball tank against a Budweiser bottle it seems like the narrower Bud Light bottle could actually be wider than the CO2 tank internally because the tank has thicker walls. The O.D. of a Budweiser bottle is 2.32 inches and the paintball tank around 2.52 inches. It's not as tall as the paintball tank however, I'd guesstimate an inch shorter. But seeing how similar they are I tried again to snorkel a Budweiser bottle and it revved up better than I thought it would although not like the zippy paintball tank. But if there was a way to splice or thread the light aluminum snorkel I made and thread it onto the beer bottle in a favorable way it'd probably have enough thrust to lift it's weight albeit these bottles like to run somewhat sideways and not upside down or even in the vertical. It's such a hassle to want to make a shape and not have the resources or willpower to design or mold something elegant that fits the bill. I like the simplicity of the methanol fueling in the bottom of the bottle but it's not an ideal method.

At the risk of boring everyone let me just say the tiniest variation in snorkel airflow will make or break a design. For example I tried to make a second 12 ounce paintball tank like the one below and even after filing the internal burrs off the ends of some plumbing pipe nipples and threading a new 12 ounce paintball tank with a 3/8 inch NPT tap, after several different snorkels - all new 3/8 inch X 6 inch nipples (a bunch I bought for a dime a piece at the junk store) none seem to work as well as the first CO2 tank! I began to wonder if the internals of the paintball tank would have an aberration, uneven bottom, or flange left over from manufacturing. I tapped it the same depth too. Some plumbing pipe nipples have a thick seam on the inside and I was careful to buy only the most perfect ones. So I don't know what's up with that. How much could one CO2 tank vary from the next? Once just screwing a nipple into the CO2 tank using the opposite end of the nipple to see if it made a different, well it did. Maybe they are out of round ever so slightly.

12 ounce paintball tank with ornamentation
download/file.php?id=15091&mode=view
download/file.php?id=15090&mode=view

Ordinary Budweiser bottle mimic hopeful next to a larger 20 ounce tank but picture a 12 ounce tank - they are similar enough to have a good chance of working if modified properly.
download/file.php?id=14825&mode=view

Here's another thing I tried but there's a little internal lip/ring where the conduit pipe adapter rests on the junction to the 1/2 inch threaded section that locks/threads in tight to the Bud bottle neck. So this idea needs work. The tests yesterday used a simple 1/2 to 3/8 inch plumbing pipe reducer to thread into the beer bottle neck.
download/file.php?id=14835&mode=view

This one likes to run vertically or sideways.
download/file.php?id=14741&mode=view

[Mark]

Well yet a second new 12 ounce paintball tank just tapped and threaded has the same problem. Both are the same brand as the one that runs. They start up normally but quickly entropy. This is mightily strange. I even tried boring out an NPT 3/8 inch X 6 inch nipple snorkel with a 1/2 cobalt drill bit to see if that would improve things. Looking inside the necks of the bottle below the threading on the neck there were some slight rough edges I filed as best I could get at them. I tell you I don't know who else would continue on after suffering so much defeat after defeat. But if it were easy it wouldn't be special.

[Mike Everman]

But if it were easy it wouldn't be special.

True that! Thanks for the reminder about trying non vertical orientations. I've gone through almost a 12 pack of silver bullet so far, and now finally some light at the end of the tunnel. New fuel, and putting a .53 inch hole in the bottom and running horizontally gets me a few second run.

The iphone 7 slow motion video is pretty great for this!

[Nick]

Here's what I'm wondering... if you put a baffle near the bottom of the pot would that hold the liquid fuel at the bottom and allow the pot to run more normally?

Like this https://www.dropbox.com/s/76s6rvvzq0a75 ... 1.png?dl=0

I have a resin 3d printer and some "Casting Resin" which doesn't burn until you reach about 800 degrees C - might try printing the whole thing!

Cheers

Nick

[Mike Everman]

I like it! clearly a measure for the spinny pot. I wonder if some concentric baffles on the bottom might make a normal static pot behave better. I'll do a slo mo of one of my glass post and see how turbulent the liquid in the bottom is.

Just getting a spinny pot going is a real hurdle! i hope we can hit on a solution, cause right now I'm thinking more of a static pot and a turbine, hero or vaneaxial. I'd much rather have an aluminum pot spinning for cooling purposes.

RE: 3d printing. I'm sure having fun making my test motor bark (it's just PLA, so really low melting point.) I just need to make sure it doesn't have a flame for long.

[Mark]

I mailed three little bottles to you this morning Mike that should arrive in a couple of days from snorkelville.

You may want to refer to this when your box arrives
If you can find some small milliliter measuring device it will help save some time when fueling the snorkelers. And the silver one which was a soap dispenser with a plastic pump top I bought at Bed, Bath, and Beyond will only run for a few seconds, maybe 7 seconds at best in winter conditions. In summer it's basically a dead fish but if you unscrew the snorkel and use it as a funnel to pour methanol down the flared end into the canister, it coats the snorkel and it's a good way to get it to start. If you put fuel in it assembled, it leaks down around the bell because the threads don't match. I say this because you only want to put in even less than 10 ml of fuel or it will flameout. It will give you a few seconds of good sound though if you do this and unlike the paintball snorkelers it likes to start standing straight up on a flat no jiggle surface. This one is special/sentimental to me because when I first witnessed how unexpectedly robust the effect, I became hooked on the "inbetweeners, sort of inbetween jam jars and pulsejets , albeit quarter-wavers. I wish you could hear it go from zero to sixty in ideal cool weather conditions with just 7 to10 ml of alcohol. Maybe you could get away with more fuel in winter. Any more because the combustion being so violent will slosh the fuel and flame it out. This one may sneak in a slight amount of air between the threads but I've blown into it when screwed on tight and not much air gets out. It may spit a little fuel around the bell you'll notice sometimes.

The baby paintball tank I'd recommend 40-50 ml of fuel to start with and hold it about a 30 degree angle. Later on if you use a leather glove when lighting it, you can ever so carefully raise or lower the angle to idealize or "surf" the combustion. A gloved hand technique can also be used if you get it to run long enough to get really hot so that if you immediately flick a Bic when it flames out the evaporating fuel left in the tank will produce a flame at the tip of the snorkel and then you can merely lean it over quickly to produce a fireball effect. I discovered this quite by accident, the bottle sometimes too hot to hold even with a glove and I didn't want to breathe methanol fumes so I lit the fumes and walked it from the screened-in porch out to the yard to pour it out and it shot out a spectacular flame. In the past I noticed the snorkels will sometimes have a tiny bit of aluminum melt from the heat and the threads by now are probably locked on pretty good on this one and I'd like to keep it in one piece. But you can run it as long and as many times as you like and it will be fine. I have a steel paintball tank that might be suitable if it had a better fueling method where it would be able to run long periods without melting.

The 20 ounce paintball tank is more likely to run the longest and you can put 80 ml of fuel in it or maybe 100 and even more but often if you've too much fuel it can be more fussy and flame-out on you. Again this tank likes to run at an angle and although 45 degrees will work it seems 30 degrees or less is more stable to me. You can put in more fuel and try a higher angle of course, whatever you want to or take the snorkel off and different size it. If you are doing sound tests or basic experiments, maybe you could put it in some water to make it last longer, I don't know how tight the snorkel is screwed into that one though so you might snug it up if it bubbles if running underwater or just keep the neck out of the water. Sometimes I lift the top of the freezer in my garage and put an empty tank in it for a short bit just to give it a bit of a boost in performance and to get the flame to chase down the snorkel when trying to light it if it's hot out.

Included in your snorkeler kit is that sound augmenter I challenge you to leave in the exhaust stream of either paintball tank for more than a few seconds without hearing protection. The smaller CO2 paintball tank snorkeler works the best for making sound but either is more than I can take. I'd like to know the physics behind that effect. It's not a thrust inducing augmenter but rather one that maybe stalls and cavitates the air? Just hold it about 3 - 4 inches out from the exhaust tip, you can use your bare hand to hold it without overheating your fingers. You'll find the sweet spot in no time. ha

Anyway I'm glad to have you give these a try. Again, if it were cooler weather and the humidity low, you'd see a marked improvement in sound and longevity, especially with the silver pint-size canister. It's so sudden to stall and fade in hot weather yet can start to hurt your ears in cool dry air it's that snappy. I bet it's not often you get a package with parts that to be kind look of questionable value or that would mystify any postal inspector should they open the box. You can keep them for as long as you want and then please mail them back so I can tinker with them some more when the weather is cooler. I think you'll be surprised how they excel over a typical jam jar. Happy snorkeling!

[Mark]

Hi Nick,
Can you post a link or a reference of the resin you're referring too? If you can bang out a shape that will take 800 C, you could make a lot of fun things.

[Mike Everman]

I mailed three little bottles to you this morning Mike that should arrive in a couple of days from snorkelville. snip Happy snorkeling!

Thanks for everything, Mark!! I'll be gone a lot this coming month, but will definitely play.