More free plans: 40 pound Chinese

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Eric
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Re: More free plans: 40 pound Chinese

Post by Eric » Sun Mar 07, 2010 5:53 am

Why do you have the mid tube so short? That's a big engine now that I see the dims, it could put out about 55 lbs thrust if you just made the mid tube 350 mm longer.
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metiz
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Re: More free plans: 40 pound Chinese

Post by metiz » Sun Mar 07, 2010 11:51 am

Hey Eric,

Why is it that you believe that lengthening the rectifier by 350mm will give me 55 pounds? Please be as specific and technical as possible in your reply.

If you truely believe that a mod like that would work, I here by invite you to prove it. The plans are available; build it to spec, confirm thrust and then add 350mm. Make some photos that shows the engine in a way so that we can see that the engine was build to spec.

If it truely puts out 55 pounds (video for proof, please) you may sell that engine after you're done with it.
*edit* also if it doesn't
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Re: More free plans: 40 pound Chinese

Post by Eric » Mon Mar 08, 2010 5:26 am

Because adding ~350 mm would make it virtually the same as what I call the advanced chinese design, which I've been building for the past 4 or 5 years.

I'd have to look at your intake setup some more, but the pipe should be capable of it.

Two proper intakes could actually be capable of a decent bit more than that, although at reduced efficiency.

I'd love to have the free time to build one to your exact specs, but unfortunately all my free time is spent building custom furniture to alleviate my bad back, and getting some solar power setups ready for spring.
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Re: More free plans: 40 pound Chinese

Post by metiz » Mon Mar 08, 2010 12:39 pm

Eric, I appreciate your imput but increasing tailpipe length is not always the way to go. If I were to build your TP-180 and add one half length of straight pipe, would I get more thrust or would I get an acoustically messed up, poorly performing engine?

Also, asuming that the mods work, given 1892 mm, the total length of the engine when modified, I could design a chinese (and even easier: a thermo) that would put out way more then 55 pounds - probably closer to 100 pounds. So what's the use?
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Re: More free plans: 40 pound Chinese

Post by Eric » Mon Mar 08, 2010 1:31 pm

Increasing the tailpipe length is not always the way to go, but it is the way to go, in the cases where it is the way to go.

And then I could again say that you could get x amount more thrust by increasing the mid tube length of the scaled up short engine, or conversely scaling down an engine with a longer mid tube, so that you have a smaller engine producing the same thrust as the original, with higher efficiency, and less drag.

Why have what you think is a smaller engine put out x lbs thrust, when a narrower engine of equal or lesser volume, with less frontal drag, and higher fuel efficiency, will produce the same thrust?

Acoustics is only part of the equation, and in designs like the thermojet, is almost totally unimportant. This general geometry is what you could call highly acoustically dependent, where the thermojet is on the other end of the spectrum at being almost entirely flow driven.
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Re: More free plans: 40 pound Chinese

Post by metiz » Mon Mar 08, 2010 2:54 pm

Eric wrote:Increasing the tailpipe length is not always the way to go, but it is the way to go, in the cases where it is the way to go.

And then I could again say that you could get x amount more thrust by increasing the mid tube length of the scaled up short engine
Longer midpipe - more thrust
Eric wrote:
or conversely scaling down an engine with a longer mid tube, so that you have a smaller engine producing the same thrust as the original, with higher efficiency, and less drag.
Shoter midpipe - same thrust?
Eric wrote:
Why have what you think is a smaller engine put out x lbs thrust, when a narrower engine of equal or lesser volume, with less frontal drag, and higher fuel efficiency, will produce the same thrust?
The engine might have less frontal drag but there's a lot more steel used so more weight. There will also be more drag over the length of the engine because air sticks to surfaces. The efficiency in-flight will be different then on the ground. flight usually means vastly improved fuel consumption, mimicking the effects of a longer pipe. All in all I think a small "acoustically dependent" engine will fare better in flight then a long engine.

(I can refer to the picture on top of the forum)
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Re: More free plans: 40 pound Chinese

Post by Eric » Mon Mar 08, 2010 4:46 pm

By "or conversely scaling down an engine with a longer mid tube, so that you have a smaller engine producing the same thrust as the original, with higher efficiency, and less drag."

I mean that if you increased the mid tube length so it was the proportions of an advanced chinese, you could then scale the entire engine down to a smaller diameter, it will use less material than the short fat engine, have less surface area, less weight, and still get the same thrust.

In flight, you would get a frequency reduction from cooler operation, while it lowers the frequency it is not the same as having a longer pipe to start with, because the engine can never build up the same initial conditions.

For example, the advanced chinese when set up properly can take in and compress significantly more fuel air mixture, even at static. Therefore you get higher thrust density, and significantly higher temps, its converting a lot of fuel into energy in a small package. In flight the engine can get such a boost that the cooling effect is almost non existent, and in fact stainless steel is not able to stand up under most conditions for repeated use. Inconel 625 is working pretty well, but holy hell is the stuff expensive and hard to form, the raw sheet cost for a laird size is about $120.
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Re: More free plans: 40 pound Chinese

Post by Jutte » Tue Mar 09, 2010 3:05 am

holy moly - inconel ....wooh only in my dreams..LOL!!!

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Re: More free plans: 40 pound Chinese

Post by Eric » Tue Mar 09, 2010 7:22 pm

Jutte wrote:holy moly - inconel ....wooh only in my dreams..LOL!!!
More like only in your nightmares... Trying to form annealed inconel into small pulsejet sizes with a 20 gauge wall thickness, is like trying to make a small pulsejet with 14 gauge stainless steel. Takes some very special techniques to do properly, or a really big hammer :P

I can see why they use the stuff for armor plate.
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Re: More free plans: 40 pound Chinese

Post by metiz » Sat Mar 13, 2010 4:45 pm

*edit* See page 1, post 1 for the correct plans
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Re: More free plans: 40 pound Chinese

Post by Kool » Sat Mar 13, 2010 6:01 pm

That looks very nice Metiz :wink:

It looks just like the pulsejet on the upper side of this forum, now I understand your question of
powering a plane(drone? :twisted: ) with a 40 pound engine.

I'm glad to have the privelege of printing formats to A1 paper at school, that saves a lot of cutting and sticking :mrgreen:
...It's better to generate heat efficiently, than recover it efficiently...

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Re: More free plans: 40 pound Chinese

Post by metiz » Sat Mar 13, 2010 6:36 pm

Cool! so you're going to build one? PICS VIDS! etc :P
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Re: More free plans: 40 pound Chinese

Post by Kool » Sat Mar 13, 2010 8:05 pm

How niet te hard van stapel lope :)

I am just planning to build about 86 different pulsejets, if I had the time :mrgreen: , but one which is in able to push a gokart/trike do I like the most. But now I'm working on a (little) Lady Anne and I will start on a engine of Eric so I'm still temporarily busy here.
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Re: More free plans: 40 pound Chinese

Post by ace_fedde » Fri Apr 09, 2010 3:36 pm

Wow! just one month abroad and loads of stuff happened on the forum! Seems you guys can do without me :(

Right now I don't have an internet connection anymore and that sucks!!
Didn't realize before that I'm an e-addict :lol:

Hope to (finally) start building soon...

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metiz
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Re: More free plans: 40 pound Chinese

Post by metiz » Fri Apr 09, 2010 8:11 pm

Hey Fedde

You've been gone quit some time, long holiday? :lol:

"Hope to (finally) start building soon..."

This one! This one! This one! This one! This one! :P
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