What pulsejet should i build?

[stoffer]

Im thinking of building my first pulsejet, i looked at the plans for the most of them but i cannot decide witch one to build, and i thought that you, who know this, maybe could recommend me a set of plans?

I have a workshop with a lot of tools and some machines, i think they are called in english(swedish in parantese): Mill (fräs), lathe(svarv), and i got a couple of welding machines, gas, mig, "normal one with a electrode", and maybe a mag too.

I have been working with such machines a couple, maybe 5 or 6 years ago, and it should'nt be too hard to get used to it again.

What i thought of is:

1. I want to make a pulsejet with valves. (not a valveless)
2. Size: As small and light so it could fit a model airplane, if i ever get it to work that is, but still big enough so there isn't problems just because its too small
3. Reliable design, easy to get to work but yet effective engine.

I know this might seem as that i want the best of all worlds, but i just want a good compromise. I see this project more of learning about pulsejets than actually getting it to work flawless.

Can anyone help me?

[mk]

Hmmmm...I'm not an expert on pulse jets, especially regarding to valved ones.

I think Mark would (as usual) suggest the Dyna-Jet. So far I know, this engine is really proven to work well and gives "good thrust".
The Atom-Jet and the Pulso 1 got good reviews, too. They are both around the Dyna-Jet size.


Mark, would you give more information, please?


If you'd like to power a model airplane (don't know the model you're thinking of, but engine-thrust-to-total-weight ratio will have to fit, of course!) you'll "simply" have to build the engine as light as possible! Maybe 0.5mm or even 0.4mm thick stainless steel should be the best.

But I'd suggest first building a mild steel (easier to bend and weld) version (the main body of course) out of 0.8...1.0mm thick sheet metal for getting building and operating experience.

Other people can surely tell you more than I'm able to.

Good luck!

[Arnold Layne]

To Stoffer:

Tjena Stoffer!
Jag håller på att bygga en efter Brauner: http://www.pulse-jets.com/phpbb2/viewtopic.php?t=935
Jag svarvar den direkt ur ett stycke metall. Jag bygger motorn enbart för att experimentera. Min blir ganska tung så den kan inte användas till modellflyg. Men du kan ju alltid ta och bygga i lättare material och konstruktion. Typ plåt. Brauner motorn är väldigt enkel!

Fö har du hittat ventilmaterial typ fjäderstål?
Mvh

[stoffer]

Thank you for your comments.

Im currently looking at either the Atom Jet or the Didgeridoo.

The thing that speaks for the Atom is that it looks easy to build.

But, it seems the Didgeridoo has a better valve design, it has more like flowerleaf shape of the holes rather than just round drillholes.

What i think i've figured out is that a larger valve area permits (or requires) a larger exhaust tube diameter, wich in that turn makes a more powerful engine of the same size because of bigger loads of gas in each pulse.

Maybe im wrong, this is just speculation.

Another thing witch i don't now if it's true is that: Shouldn't larger amounts of gas make the engine run cooler and on lower frequency? Maybe i got it wrong. If anyone has any thoughts of this, please share, im very new on this and i'm sorry if im asking stupid questions and making weird assumptions.

[stoffer]

To Stoffer:

Tjena Stoffer!
Jag håller på att bygga en efter Brauner: http://www.pulse-jets.com/phpbb2/viewtopic.php?t=935
Jag svarvar den direkt ur ett stycke metall. Jag bygger motorn enbart för att experimentera. Min blir ganska tung så den kan inte användas till modellflyg. Men du kan ju alltid ta och bygga i lättare material och konstruktion. Typ plåt. Brauner motorn är väldigt enkel!

Fö har du hittat ventilmaterial typ fjäderstål?
Mvh

Jag har tittat på brauner också, men jag förstod inte riktigt hur man skulle tillverka det främsta stycket. Att svarva det ur en del borde ju gå, men då har vi vikten där. Jag läste i din tråd att du undrade om det skulle hålla med aluminium mot värmen. En idé är ju att tillverka en platta i kolstål som har hålen borrade i sig som du fäster i den solida delen i aluminium som en värmesköld. Kanske funkar, kanske inte, jag är väldigt ny på området.

Jag såg också att Brauner hade ett bättre utnyttjande av ventilytan med blombladformade hål istället för runda hål, vilket ju talar för den motorn.

Något material för ventilblad har jag inte kollat på ännu, men fjäderstål borde väl inte vara så svårt att få tag på? Jag får titta närmare på det under veckan.

Lycka till i övrigt, jag tar gärna del av projektet om du vill dela med dig!

Kristoffer


PS. Im sorry for the Swedish in this post, if anyone want to i can translate our conversation to english, but i don't think it will be of much interest for anyone, at least my part is pure "newbie-speculations". DS

[alex]

Hej!
Jag har byggt en "chinese", men ej startat den än.

mvh
Alexander

[Bruno Ogorelec]

Another thing witch i don't now if it's true is that: Shouldn't larger amounts of gas make the engine run cooler and on lower frequency? Maybe i got it wrong. If anyone has any thoughts of this, please share, im very new on this and i'm sorry if im asking stupid questions and making weird assumptions.

Kristoffer, you will learn that the chief operating parameter in pulsejets is length. It determines the frequency. The next most important parameter is the impedance (resistance to the passage of gas) of the intake.

The influence of those parameters on performance is not simple. For instance, higher frequency usually does not mean higher performance, despite of what you may expect. In fact, lower frequency (greater length of the engine) usually gives better performance, for the additional time in the working cycle allows better aspiration.

The easiest way towards better performance is volume. If you wish to see the greatest thrust, find the model with the greatest internal diameter of the combustion chamber.

At the beginning, avoid building small pulsejets. The bigger a pulsejet is, the easier it is to make work, as a rule. Small pulsejets are for experts only.

If you don't particularly like the conventional models, my suggestion is to try building the Maupin. It is (in my opinion) the most interesting model with valves you will find on this website.

However, you will also find out that the greatest interest among the people gathering around this website is generated by the valveless pulsejets.

Be careful, though. People affected by the VPS (Valveless Pulsejet Syndrome) have been known to drop from school, ruin their businesses, divorce their wives etc. One has moved into wild Canadian tundra and devoted himself to duck shooting. Another is seeking political asylum in an Asian country.

[Hank]

Im thinking of building my first pulsejet, i looked at the plans for the most of them but i cannot decide witch one to build, and i thought that you, who know this, maybe could recommend me a set of plans?
Hello- I haven't read the rest of the posts on this thread, cramped for time today. There are plans available here on Ken's site. Click around.

I have a workshop with a lot of tools and some machines, i think they are called in english(swedish in parantese): Mill (fräs), lathe(svarv), and i got a couple of welding machines, gas, mig, "normal one with a electrode", and maybe a mag too.

(Thanks for the language lesson. I communicate with several Swedes through the net. Normal one with a electrode= "Stick Welding")

I have been working with such machines a couple, maybe 5 or 6 years ago, and it should'nt be too hard to get used to it again.

What i thought of is:

1. I want to make a pulsejet with valves. (not a valveless)
2. Size: As small and light so it could fit a model airplane, if i ever get it to work that is, but still big enough so there isn't problems just because its too small
3. Reliable design, easy to get to work but yet effective engine.

I know this might seem as that i want the best of all worlds, but i just want a good compromise. I see this project more of learning about pulsejets than actually getting it to work flawless.

Can anyone help me?
My advice is to build a couple of "Jam Jars". (I am constructing another article on same which builds on the one published in Mr. Cottrill's Jetzilla effort.) Then build a heavy (thick materials) PJ. I'd then build an enjine for flight based on the more successful designs like the P-90 or Dynajet. Good luck and glad to have you, Hank

[Mark]

[quote="mk"]Hmmmm...I'm not an expert on pulse jets, especially regarding to valved ones.

I think Mark would (as usual) suggest the Dyna-Jet. So far I know, this engine is really proven to work well and gives "good thrust".
The Atom-Jet and the Pulso 1 got good reviews, too. They are both around the Dyna-Jet size.


Mark, would you give more information, please?

I'm partial to the rap, tap, tapping of the red head woodpecker, the Dynajet, it's small and stylish, yet machine guns nicely, heck even the starting bursts and backfirings are a kick to listen to, let alone the full blown noise it makes that frightens the uninitiated. But even my smaller Tigerjet is a wonderful pulsejet in it's own right. It's hard to believe the sound it generates from a ~7/8ths inch exhaust, especially if you unscrew the head and just twirl the little body in your hand in retrospect, out of that little feather-light tapered tube comes quite a bit of noise, a deafening noise with an almost sudden orange-yellow glow, it gets your attention.
Mark

[Anthony]

Another thing witch i don't now if it's true is that: Shouldn't larger amounts of gas make the engine run cooler and on lower frequency? Maybe i got it wrong. If anyone has any thoughts of this, please share, im very new on this and i'm sorry if im asking stupid questions and making weird assumptions.

Be careful, though. People affected by the VPS (Valveless Pulsejet Syndrome) have been known to drop from school, ruin their businesses, divorce their wives etc. One has moved into wild Canadian tundra and devoted himself to duck shooting. Another is seeking political asylum in an Asian country.

Wild Canadian Tundra : Viv, and by the way if Lac-St-Jean is tundra I wonder what the north is!

Seeking asylium : Skyfrog? (Well considering Taiwan-China's relationship...)

[steve]

"seeking asylum"- I think he means Bruce

[Anthony]

"seeking asylum"- I think he means Bruce

Haha, I get it now! Yeah, makes a lot of sense!

[skyfrog]

[Seeking asylium : Skyfrog? (Well considering Taiwan-China's relationship...)

We Taiwanese are good at couting how many missiles are aiming at us. My daughter is 4 years old now, I plan to teach her how to count numbers bigger than 600. No big deals. :)

[Viv]

Another thing witch i don't now if it's true is that: Shouldn't larger amounts of gas make the engine run cooler and on lower frequency? Maybe i got it wrong. If anyone has any thoughts of this, please share, im very new on this and i'm sorry if im asking stupid questions and making weird assumptions.

Be careful, though. People affected by the VPS (Valveless Pulsejet Syndrome) have been known to drop from school, ruin their businesses, divorce their wives etc. One has moved into wild Canadian tundra and devoted himself to duck shooting. Another is seeking political asylum in an Asian country.

Wild Canadian Tundra : Viv, and by the way if Lac-St-Jean is tundra I wonder what the north is!Seeking asylium : Skyfrog? (Well considering Taiwan-China's relationship...)

Yes I wonder what the north is like too:-) but hey I got my super duper sportcheaf hunting gear so I will be as warm as toast (rotie) so it wont matter to me:-)

Viv

[Mark]

This is a good picture of a Dynajet. It's well worth it just to see the expression on other people's faces when it does a few false starts and then goes full grease. The noise is really great for a meager one pound engine.
I'd like to streamline/micronize all the auxillaries, the ignition, the fuel tank the mounting stand so as to get the whole thing down to an elegant, convenient, starts from the get-go, something that really makes an impression.
Once I just sprayed some methanol into the tailpipe and a mist or two in the venturi/intake. Then I lit it with a lighter at the tail end, and to have it rev up in your hand with instant noise for a mere few seconds is quite impressive. You can't get much more fun than that, a hand held spectacular occurence, especially when you are not really expecting anything major to happen. This is hard to achieve, but you can do it if the air or weather is in your favor.
Mark

http://cgi.aol.ebay.com/ws/eBayISAPI.dl ... otohosting