Ancient pulse jets?

[Mark]

http://www.nmia.com/~vrbass/pop-pop/

[Mark]

http://www.nmia.com/~vrbass/pop-pop/
http://www.motherearthnews.com/Alternat ... et__Heater_

[Anders Troberg]

That clearly leaves propulsion.

Not really.

You still havn't covered ceremonial use, which has little practical requirements, it just needs to be suitably impressive, which I have no doubt a pulse jet would be at the time. Pour some lamp oil into the exhaust of a couple of Reynsts outside the temple and you'd get a noisy display of fire that would have everybody convinced that you not only had Zeus/Jupiter/Thor on your side, you were also best buddies.

Also, using the sound as a signaling device over fairly large distances (much like signaling fires) or a mass warning "siren" for a smaller area like a city would probably work fine. The noise is not always a problem, sometimes it can be used.

I'm no expert at such things, but I can also imagine that the sound could be used in battle to disable enemy cavalry by terrifying the horses (this of course assumes that you don't have any cavalry on your side). With the right enemy, you could perhaps even scare the troops (see ceremonial use above).

[Mark]

And don't forget trees. Trees might have been a way in which pulsejets could have been discovered. Forest fires sometimes produce resonating trees, the dead hollowed out trees that catch fire are known as hooters. And I can't find any link to read more about them, however Hooters girls and owls come up often, in a simple search.
Seems like it would be a good topic for Scientific American, the whole ball of wax about how pulsejets might have and did come about, how we could have been annoying our neighbors much sooner if for only a few more clues picked up by some clever person in the 1400's let's say.
Mark

[Eric]

A pulsejet burner for smithery is also unfeasible. The exhaust temperature is far too low because of the mixing with sucked-back air. A pulsejet blower is just not worth the trouble, compared to ordinary bellows.

Actually Bruno. I used one of my 12 lb chinese engines to forge the katana I made. It gets PLENTY hot in there. I actually accidentally melted the front portion of the first piece of bar stock right off, it was something like what larry did with the dynajet and tubing, except much bigger and much more scary. Tempering it was fun, heated it with the Pjet and then pulled it out and evened out the temperature distribution with a torch before quenching it.

Its not so much unfeasible because of the temperatures, but I doubt anyone would use it for mass production of swords because of the noise and vibration involved.

Eric

[Bruno Ogorelec]

I'd say you're all quibbling. No really practical application that clearly outshines what the ancients actually did have at the time.

The pulsejet is pretty good for some industrial applications. The ancients did not have industry as we know it. It is also good for fast propulsion. The ancients had no real need for fast propulsion, having no fast vessels.

So, while the ability was there, there was no real need for the pulsejet to be developed. Meaning that it may well have been discovered back then, perhaps even repeatedly, but shrugged off as a curiosity of little apparent value.

Just as the Chinese developed the kite and built some fairly big ones, but never made the progression to the hang glider, however logical it may seem to our eyes and from our perspective.

Another example of a seemigly fantastic invention that was completely ignored is the wheel. Ancient Egypt did not use the wheel. It was known at the time, but only used on children's toys. No one saw the need. Everything worked pretty well without it and no one bothered.

[larry cottrill]

A few months ago, I thought of trying to interest somebody in a prototype tornado siren made up of a couple of FWEs. The engines would have been mounted tail down in a bird-proof cage with conical wave reflectors underneath each engine. The big one would be mounted somewhat above the small one so as not to block the sound. This would be mounted beneath the town water tower, or on top of the local grain elevator or some such. Properly set up, it would be virtually zero maintenance. Lightweight construction would be unnecessary, and the whole thing could be made of Cor-Ten steel, so it would rust but never rust away.

Naturally, there are problems. You would have to provide absolutely reliable startup and stopping, and automated switching between the engines at a predetermined interval, weatherproof electrics and propane storage, battery charging, etc. So, naturally, I didn't present it to anyone - seemed like way too much hassle. But, none of the problems is insurmountable, and it would have to be at least as good as a more complicated mechanical siren, and probably WAY louder.

What would sell it is if you could prove higher reliability coupled with absolute zero maintenance over years of use. Of course, you'd have to go to the expense of getting it "certified" by somebody for emergency service, or no one would give it a second look.

L Cottrill

[Dave367]

You guys are great! Jeez, I drop one post, go away for 3 days, and come cback to 3 pages of great responses! Thanks for the input!

Otto, I think Mark clearly solves the marine fuel problem--putt-putt boats run quite happily on coal or wood, as well as oil. I'm unsure about scaling this device, but it's surely possible to gang them together to give larger thrust.
However, I was actually thinking about land--and air vehicles. Like this one: http://www.amazon.com/gp/reader/0801874 ... eader-page

Not only does it rather handily gear down the low thrust/high speed nature of a jet (pulse or steam), it does so without a gearbox of any kind. As to flying vehicles; Japan had manned kites in the 12th and 13th centuries, and at least one chronicle of these includes "cutting their lines and flying away" when under attack. I'm ont at all sure that the waste heat of a PJ mightn't have been used to maintain altitude on a Montgolfier balloon--allowing the development of controled blimps several hundred years before they actually appeared.

We seem to have settled both the materials science issue (the "means") and also the theoretical discovery issue (the "opportunity"); there still seems to be question about "motive." Roman and Greek war fighters were always--always--in search of technological advantages in warfare. The Greeks went to the trouble of inventing ship rams, ship "shakers" ultra-fast triremes; all to make ship warfare more efficient. Hannibal took elephants over the Alps, for crying out loud, for their advantage in battle (imagine if he might have carried auto-tanks, instead?) Even in World War II, we had horses drawing artilliary and even armor over long distances--devices which were self-powered while in battle--because of lack of sufficient fuel sources to transport them there.

Leaving war alone, Peacable uses of fast, high powered transport devices include not just maritime tonnage, but the same things we eventually DID furst use them for--fast mail delivery; early-to-market transport of valuable crops (tea, opium), passenger transport.

When looking at fuel efficiency and transport machines, don't let us forget that the first steam engines--for nearly 100 years--were strictly stationary applications; specifically water pumping from mines--and later central power for factories. Imagine if the Industrial Revolution and modern manufacturing had started, not in the 16th centure, but in the third?

To the several posters who spoke to the *liklihood* of civilizations such as Rome to embrace technical solutions, I thank you. There are and were many, many reasons why these things did not in fact happen, but that was not my quandary. If I asked you whether a solid gold pulsejet were possible, I'm speaking in a technical sense, not whether such a device would be financially successful.

Dave

And I just can't get over the concept of wooden pulsejets (hooters, indeed!). Early cannons were ironbound wooden devices, and weren't meant to last very long. I wonder whether a "disposible" PJ could be built of, for insstance, parafin-soaked cardboard or wood? The earliest rockets certainly were of cardboard and paper!

[Jonny69]

Another example of a seemigly fantastic invention that was completely ignored is the wheel. Ancient Egypt did not use the wheel. It was known at the time, but only used on children's toys. No one saw the need. Everything worked pretty well without it and no one bothered.

Apart from on their chariots Bruno lol. Rameses II had chariots with wheels detailed on his engravings heheheh.

My friend had a bamboo mortar from China which was an ancient design. Basically a long 4" bamboo tube closed at one end with a 10mm hole in the side near the bottom. He used to pour a fair bit of meths into the bottom and light the hole to get the bamboo hot and it would draw air in through the hole by itself. Then something (like a frog) could be dropped into the tube, shot out with the blast and it would re-air itself in a few seconds ready for the next shot. I bet they experienced them resonate at some point. It's a bit like my baked bean can cannon but made of wood and a fair bit bigger.

Jon

[thecheat]

hmm, well, would it be possible for a reninst (sorry forgot spelling :oops: ) jar? say they made a clay (fired) pot, and dumped some flamable liquid down it (such as what the greeks did for their flamethrower) if it was a fuming liquid, and the opening in the top was small enough, I'm sure they could get some good pulsations until the pot broke. not sure if this classifies as a true PJ, and it is a bit of a chance factor, but, I'm sure it could be possible, there's not too much involved and I'm sure the ancients had the right stuff for it to work.

[Hank]

Olive oil? Could the ancient Greeks have produced enough olive oil to power a dozen warships for, say, an hour a day? Sounds like an awful lot of olive oil to me.[/quote]

Hello- I'm doing research into the technology of the US Civil War period.
The steam power of the day required eighteen to twenty two tons of coal a day expenditure for a ship the size of the C.S.S. Alabama . The ships of the period were, in the main, composite propulsion, steam and sail.

If the ancients were to utilize combustion based propulsion I'd wager they would have used sails also.

Pine tar would have been my choice were I chosen to built a fleet for the Spartans.

[marksteamnz]

Distillation would produce 90% ethnanol. You can use pottery for the still. Not very efficient but do able. Better if you can work copper. During WW2 the fertiliser works here in NZ used ceramic spiral condensors in the Sulphuric acid plants as the metal units weren't avalaible.
I've seen it sugested that (Richard Bach I think??) that a 1940's sailpane could have been built by the Pharoh's if they had the knowledge. Dry climate so the starch based glues would have been OK the rest is wood working, and very clever use of lashings for hinges etc. Probably a better statement would be any of the man powered aircraft teams could have build a 1940's sailplane using technology and matarials avaliable to the Pharoh's
Of course the kicker is the knowledge

[Dave367]

For marine use, I would imagine some form of coal power, not oil--and not likely pulsejets--or rather, if pulsejets, then more likely "putt putt" boat-style steam pulsejets than air/fuel jets. Yes, certainly a combination of sails and power; the former for most transport between points; the latter primarily in battle. Of course, after a few centuries, when the surface seeps of Mesopotamia would have been developed into true oil wells and primitive distillation of petroleum developed into more modern cracking towers (as it actually did, much less than a century after internal combustion engines proved the need for it).

As to fuel; biodiesel (from olive oil?) would have much more specific energy in it than distilled spirits; and would be considerably cheaper to produce--the meths would be used to get the jet lit, then it would run on biodiesel--or real diesel as petroleum science advanced.

Other sources of oil would have been whale oil, rock oil, corn or other vegetable oil, turpentine/pine tar; and more likely a combination of all the above. Of a certainty, without readily avilable, large sources of petroleum, pulse-jet powered vehicles would be limited to small, fast stuff, like war chariots, messenger or valuable fast freight, mail or communication packets and the like. You wouldn't see a fleet of battleships being powered by whale oil.

There seems to be a presumption that humans around the time of christ didn't have much metal. this is misplaced, I think. Copper, tin and brass/bronzes were quite advanced, and major trading in these metals were established all over europe and asia. It is possible to rivet together quite strong pressure vessels and pipes--welded boilers were unknown in OUR world until the 20th century.

In my first email I asked whether one could buiild a pulsejet in copper; no one answered. Pure copper melts about 1900° F degrees; brasses and bronzes a little higher--steel at 2500° F. Is this sufficient to contain a pulsejet?

Does anyone on the list have experience running a pulsejet on pure diesel or kerosene (jet fuel)? Is it reasonable to consider a non-fuel injected version of such a thing, and how hard is it to get it started, say with meths? How tough is the change-over to diesel? If it needs to be fuel-injected, how simple could the injector system be? (Could an "engineer" stand there and squeeze a bottle full of fuel, for instance?)

Would a blacksmith's bellows create enough air to start such a beastie? How about a simple fireplace bellows? Of course, if one built the "autochariot" I refered to earlier, it has the jets on the ends of a long boom, and they could be "spun up" to starting pressure pretty easily by hand.

Is anybody interested in actually *building* a PJ of "ancient" materials, and run it on "ancient" fuels and starting methods?

Dave

[Hank]

Other sources of oil would have been whale oil, rock oil, corn or other vegetable oil, turpentine/pine tar; and more likely a combination of all the above. Of a certainty, without readily avilable, large sources of petroleum, pulse-jet powered vehicles would be limited to small, fast stuff, like war chariots, messenger or valuable fast freight, mail or communication packets and the like. You wouldn't see a fleet of battleships being powered by whale oil.

Hello, Dave- I disagree with your last sentence.A project of this nature inevitably would have been the property of some state and little doubt with the express purpose of dumping large quantities of troops somewhere.
The advantage of transport against tide and when winds do not favor, while tried in small prototype, would have been utilized in a large scale.
Steel existed in small quantites in the ancient world. Swords were worked out of meterorites of favorable composition.

[greywuuf]

I realize that it has allready been decided that some instances of resonance were know, but can't help adding this. Is anyone here fammiliar with the musical instrument the "ocarina" ? It is sometimes refered to as " the singing pot" and as far as I know was known to the south american societies quite some time back. Just another example of a resonant system in ceramic. Of what use they would have made of it I can not say.