2004-02-14 - Pulsejet History Well and Truly Made

Moderator: Mike Everman

Nick
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Congratulations

Post by Nick » Tue Feb 17, 2004 11:12 am

Hi Guys, just logged on. Fantastic stuff Bill and Mil, as Bruno has already said what a great time to be involved in Pulsejets.
Waiting with baited breath for March!
Any chance of some videos soon?

great work!

Nick

Ray(in England)
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Congrats.

Post by Ray(in England) » Tue Feb 17, 2004 3:51 pm

Congratulations,and many thanks to Milisavljevic and Bill for this painstaking break-through,scientific work.
I admit that I don't understand the scientific details,but from the enthusiasm and approval of those that do,I know it ought to bring us much better pulse-jets, and hopefully cheaper,100% reliable propulsion.
It proves,that when a person that understands the underlying science puts his mind to a problem, success is much quicker, and repeatable.
Ray.

resosys
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Post by resosys » Tue Feb 17, 2004 9:58 pm

Milisavljevic,

Thank you for taking the time to respond to my questions about the higher resonant frequency. Your explanation was perfectly clear, which is a wonderful break from what I deal with all day here at work. I work with a bunch of genetic researchers that can't explain anything.

So, how about those Chinese designs. Does anyone have any performance numbers for specific dimensions? Are there any Chinese documents that have been translated?

Thanks again,

Chris

mk
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Post by mk » Tue Feb 17, 2004 11:19 pm

Very well done Mil and Bill!!!
Bruno already gave the right statement.

I've began thinking about "high-frequency-engines" just a few days ago, so I'm really glad that somebody already succeded in this field. So I think trying some optimizing of my already working engines could be useful...

I'm waiting for more news of your works...
mk

Bruno Ogorelec
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Post by Bruno Ogorelec » Tue Feb 17, 2004 11:26 pm

resosys wrote:So, how about those Chinese designs. Does anyone have any performance numbers for specific dimensions? Are there any Chinese documents that have been translated?
The 'Chinese' design may well be European in origin. Its 'Chinese' name probably stuck because it was mass-produced in China for the Western markets.

Milisavljevic is just about the only one (or maybe one of the two) people who have kind things to say about the 'Chinese'. Two people I know of who have built fairly accurate representations of the engine -- Dewey King (a master of pulsejet construction) and Paul Sherman (no mean engine builder himself) -- have both dismissed it as not worth the trouble. Sherman famously described the thrust in very scientific terms: "A mouse blowing through a soda straw". King was only a little kinder about it when I wrote to him.

This is the best drawing with dimensions that I have.
Attachments
Chinese_dimensions.jpg
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Bruno Ogorelec
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Post by Bruno Ogorelec » Tue Feb 17, 2004 11:28 pm

Sorry, upon checking the source, I must correct a misquote:

It was "hamster blowing through a soda straw", not "mouse".

Apologies to everyone concerned.

resosys
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Post by resosys » Tue Feb 17, 2004 11:40 pm

brunoogorelec wrote:"hamster blowing through a soda straw", not "mouse".
I've seen a lot of folks making reference to how pathetic they are, I'm just curious about their dimensions and what may be gleaned from the design. There's a little magic in there somewhere.

I'm interested in simple to produce, well behaved engines for our performance art projects as well. Right now, it looks like the locky kazoo may be the one.

milisavljevic
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Post by milisavljevic » Wed Feb 18, 2004 2:26 am

DELETED.
Last edited by milisavljevic on Wed Aug 18, 2004 8:27 pm, edited 1 time in total.

Mark
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Post by Mark » Wed Feb 18, 2004 3:36 am

I am curious who has a chinese pulsejet and what did they measure for thrust and fuel consumption? Who is the source??? It says 3.3 lbf of thrust, could someone explain that for a simpleton like me. Is that a per square inch of exhaust area or mean cross sectional area of the duct or what? I think even with 5 or six figures/factors/quotes it is still possible to leave loopholes or not pin down what's really what. Someone mentioned Forrest's data, he's still hoping to get 100 people first to pay/lay down $60.00 each before he sells the Russian translation of the book we all want, which according to Don Laird, who got him to give him a few charitable pages, weren't very interpretable/translated by Forrest in the first place. I wonder if he has taken statistics? Will he get his $6000.00?
Does anyone remember in Reynst's book or Foa's was it where they had a similar shaped pulsejet perhaps that was said/conjectured to get two cycles per hammer cycle for lack of a better word, but it was hard on the valves.
If the chinese is cycling faster than the other similar shaped designs, perhaps it is getting a double duty cycle. If it was a dream design, I'm sure the French, Maori, or others would have jumped on it, it's ten times more streamline than the folded non-aerodynamic Ecrevisse or Hiller/Lockwood and it quite resembles the Escopette in some respects sans/trade front intake for a side/rear facing port, given the thousands of shapes tried. There's no free lunch, just ask Forrest.
Mark

resosys
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Post by resosys » Wed Feb 18, 2004 4:18 am

milisavljevic wrote:PS: Chris, I encourage you to give the little Chinese a try. The diameters provided in Bruno's illustration should be interpreted as ID's and not OD's; the ID of the inlet is 0.9375 inches (not counting the flare!). The thickness called out in the original plan was 0.013 inches; however, if you follow the ID as diameter rule, you may substitute easier-to-handle (thicker) stocks.
Thanks for the breakdown and the numbers (I love the numbers as well). I'll go about trying to digest them and make some sense of it all. Specifically, it would be fun to apply some of the physics I've been studying to design an engine around the layout of the chinese design. I've got some ideas in mind.
If nothing else, it will be an interesting contrast to your numerous Lockies.
Certainly. I don't think my lockies make a lot of thrust. They blow really hard and make a hell of a wind, but I'm sure they're nowhere near the max output seen by Lockwood and Hiller or others after them.
PPS: Give Mike's 'Locky Kazoo' a try, too!
Oh yeah, for sure. Mike's engine is so wonderfully simple and cheap to build.

I'll post some drawings of my chinese engine revision ideas.

Chris
Last edited by resosys on Wed Feb 18, 2004 4:37 am, edited 1 time in total.

Mark
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Gold fever

Post by Mark » Wed Feb 18, 2004 4:29 am

PS I don't know a lot about pounds of thrust per pound of fuel per hour measurements related to everything else, the weight of the engine for example might be a pound like the Dynajet, giving it a thrust to weight ration of over 4 to 1. You could strip it down and get 8 to 1 using thinner/lighter materials. If you used compressed fuels, you will pay a weight penalty for the tank, big tanks weigh a lot. If you make the skin of the pulsejet very thin, it isn't going to hold up for very long. When you measure internal pressures, they are varying all the time in different places, perhaps others of you out there can think of other factors that could slant the overall picture, I'm tired but I know there are many variables to consider.
I've read that big pulsejets are more efficient than little ones and I've read small pulsejets are more efficient than big ones. But if you put a bunch of little ones in a bank to equal a big one they become draggy. Tharratt may have mentioned some ideas about size, I just can't remember now.
If you use propane for starters, there is some energy stored in the pressure of the tank, if I built a tiny pulsejet with a very tiny hole, I could get amazing thrust just by expanding the propane. These are just some half baked ideas of mine, but it is something that I feel has some ring of truth.
Mark

Mike Everman
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Post by Mike Everman » Wed Feb 18, 2004 4:49 am

I guess after the Kenny Kazoo, I'll do a China Kazoo, then I need to make a brace of 100mm units to power my dry lake bed cruiser! Oh I will have the Salt Lick Trophy, Chris.
Don't underestimate the thrust of your Locky's, Chris, they're brutes!

Mark, why even light the propane? Just knock the valve off the tank with a hammer. I'm sure that's going to have a phenominal thrust to weight ratio for about 3 seconds! I know what you mean, though, the entire system must be considered for these metrics to make sense. If you need a 5lb tank to carry 8 lbs of fuel, it starts to make an engine that sips from a plastic milk jug look pretty good.
Mike
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pablo
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Post by pablo » Wed Feb 18, 2004 4:50 am

Mark wrote:I am curious who has a chinese pulsejet and what did they measure for thrust and fuel consumption? Who is the source??? It says 3.3 lbf of thrust, could someone explain that for a simpleton like me.
Mark
c'on guys!
I thought you had a better memory!
first of all, I measured around 1.5 kg of thurst.

I could never measure the fuel compsumtion.
and wont be able to do it till I get my vac cleaner repaired.
Pablo

resosys
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Post by resosys » Wed Feb 18, 2004 4:59 am

Mike Everman wrote:I guess after the Kenny Kazoo, I'll do a China Kazoo, then I need to make a brace of 100mm units to power my dry lake bed cruiser! Oh I will have the Salt Lick Trophy, Chris.
Ha, you're dreaming. I already have 15 engines and 15 propane tanks!!!
Don't underestimate the thrust of your Locky's, Chris, they're brutes!
Once I get out from under all this work related stress and hell, I'll hopefully have time to build a test stand with the ability to measure thrust.

Chris

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Post by vhautaka » Wed Feb 18, 2004 6:15 am

brunoogorelec wrote: This is the best drawing with dimensions that I have.
How about the drawing on this site? :) http://www.pulse-jets.com/count/pulse.php?ID=6

It should scale well for a slightly larger version with 3" or 4" dia. cc, don't you think?


- ville

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