Jims Little 3 Lb Thermojet

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Eric
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Jims Little 3 Lb Thermojet

Post by Eric » Sat Oct 21, 2006 2:57 am

I have been pretty buisy lately working on big projects, finally got a little break. Back a while ago Jim traded me some stuff for an engine. Originally he wanted just a cheap old mild steel engine, but I really liked the stuff so I decided to make him a stainless engine.

Originally the engine was a 4 intake thermojet but the fueling was too tempermental with the internal system I wanted to use, quick easy starting wasnt very easy, so I decided to just go with two intakes with rosscojectors stuck in the front of the intake. One of the injectors flows a little more than the other as you can see in the video as a cool spot. A pinch with a vice grip should fix things.

Its super easy to start and throttle now, and should last forever.

This is how a thermojet should run, I'd say unlike those pieces of crap sold on ebay, but those dont even run at all.

Let me know what you think :)

Eric
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re: Jims Little 3 Lb Thermojet

Post by Mike Everman » Sat Oct 21, 2006 3:30 am

Sweet, man.
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re: Jims Little 3 Lb Thermojet

Post by Eric » Sat Oct 21, 2006 4:51 am

I think my neighbor that complains about the noise has moved away, so I have been able to run things at night again. It was such a drag to only be able to run things on weekdays from 9 am - 4 pm, seeing them at night time has really rekindled my pulsejet fire....

That moves my next nearest neighbor who doesnt think that pulsejets are awesome to about a mile. :)

Heres a brightness / contrast enhanced pic that shows the engine and the fuel system a bit better.

You can really see the point in the exhaust flame where the seperation boundary exists, though unfortunately theres no distinct exhaust vortex.

Eric
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milisavljevic
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re: Jims Little 3 Lb Thermojet

Post by milisavljevic » Sat Oct 21, 2006 5:41 am

Hello Eric --

Sweet little thermojet! Pulsejets are most definitely creatures of the night! Good for Halloween, perhaps?

I will extract the audio from the clip you have provided and will post an analysis to the forum later tonight.

Best regards,
M.
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for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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re: Jims Little 3 Lb Thermojet

Post by milisavljevic » Sat Oct 21, 2006 1:43 pm

Hello Eric --

I completed the audio extraction and performed a basic acoustic analysis of the small thermojet you tested.

I have already emailed you a zip file with five (5) extracted segments; each individual segment is less than
2 MB in size, so you may upload one or more of them to the forum, if you wish. I will summarise the results:

A. I extracted audio segments corresponding to the following time indices (format: min:sec) ...

[1] 00:01.0 - 00:03.5
[2] 00:07.0 - 00:12.0
[3] 00:21.0 - 00:31.0
[4] 00:45.0 - 00:50.0
[5] 00:55.0 - 01:05.0

B. I determined the fundamental resonance for each segment (average of all sampled frequencies) ...

[1] fundamental and three (3) harmonics; F1 = 207.6 Hz, average of all frequencies (08 samples)
[2] fundamental and three (3) harmonics; F1 = 223.5 Hz, average of all frequencies (12 samples); note (1)
[3] fundamental and three (5) harmonics; F1 = 233.7 Hz, average of all frequencies (12 samples)
[4] fundamental and three (4) harmonics; F1 = 234.1 Hz, average of all frequencies (10 samples); note (2)
[5] fundamental and three (3) harmonics; F1 = 214.8 Hz, average of all frequencies (08 samples); note (3)

C. I then ranked the acoustic power distribution for each segment (in descending order) ...

[1] power distribution (ranking 4/4) = F4, F3, F2, F1
[2] power distribution (ranking 4/4) = F3, F1, F2, F4
[3] power distribution (ranking 4/6) = F1, F2, F3, F4; note (4)
[4] power distribution (ranking 4/5) = F4, F1, F3, F2
[5] power distribution (ranking 4/4) = F1, F2, F3, F4

[3] power distribution (ranking 6/6) = F1, F2, F3, F4, F5, F6
[4] power distribution (ranking 5/5) = F4, F1, F3, F5, F2

Please note that the camera position changed several times during the video; similarly, the throttle was
advanced through the first 50 seconds (approx.), then reduced to a low power level in the last seconds.

note (1) : considered independently, F1 = 226.7 Hz
note (2) : considered independently, F1 = 236.0 Hz
note (3) : considered independently, F1 = 213.0 Hz, and F2/2 = 217.5 Hz (F2 = 435.0 Hz)
note (4) : F1, F2 were approximately equal by rank

Cheers,
M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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re: Jims Little 3 Lb Thermojet

Post by Jim Berquist » Sat Oct 21, 2006 5:20 pm

This is what happens when the Forum is at it's best. You put the right people together in the right place at the right time and things happen!

Eric! You done did good with me! I have a engine coming that will be the basis of a on going education on the P.J. ....

I seen it in peaces. I got to see it assembled and reassembled. I got to see it being like a peace of art ,,, created!!!

Box it like it was your first born, when you ship it!!! HAAA!!!!

I even have a Acoustic Signature of it thanks to Mr. Milisaljevic.

With Much thank You, to All .......Jim
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re: Jims Little 3 Lb Thermojet

Post by Jim Berquist » Sat Oct 21, 2006 5:46 pm

Will Correction of the right hand Rosco injector change the out put?. I don't think any frequencies would change . May rise amplitude some...Residence Frequency is a function of the tuned chamber , Right?

Jim
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re: Jims Little 3 Lb Thermojet

Post by Eric » Sat Oct 21, 2006 5:52 pm

Hehe. I'll get some real nice 6mp day time shots for you when I fix the one injector side this afternoon. I'll have it all boxed up ready for ups on monday. It will probably get there for you by thursday or friday.

With the rosscojectors it very well may be self starting. Its just damn cold here so the propane pressure is really low. Last night when I ran it, it was only about 35 degrees or so and the tank instantly iced up. Down there you should have a lot more pressure to work with.

Eric
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re: Jims Little 3 Lb Thermojet

Post by Eric » Sat Oct 21, 2006 5:55 pm

The thrust might go up a tiny bit, but the most noticeable thing will be smoother low end running. You can probably hear me talking at the start of the one run, and when I throttled it down real low right before shut off, you can hear it grumbling.

Eric
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re: Jims Little 3 Lb Thermojet

Post by Jim Berquist » Sat Oct 21, 2006 7:03 pm

Not much better here! This morning it was 35 degree....

I'm sick as a dog! I have a cold from hell! Do you think I could run it with Isopropanol and a lite oil via a bladder and needle valve? Through the Rosco injectors? I have 50 gal of Isopropnol 100 percent at work in the wast bin?

Jim
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re: Jims Little 3 Lb Thermojet

Post by Eric » Sat Oct 21, 2006 10:01 pm

Damn if its that cold there then you could heat your house with the alcohol.

100% should run if the engine is already warmed up. If you make a little propane stinger and then use the build in injectors for the alcohol you can get it running on propane and then turn on the alcohol and see what happens.

Mike was it you that tested a little J-200 and got 3 lbs thrust from it? These intakes are slightly smaller than what is used on the 2 intake engine because I was originally going with 4, but it still puts out around 2 lbs thrust. On the lowest setting it puts out less thrust and heat than a hair dryer! :)

Eric
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re: Jims Little 3 Lb Thermojet

Post by Mike Everman » Sun Oct 22, 2006 12:08 am

No, haven't run it yet. Dave's got one he's run.
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re: Jims Little 3 Lb Thermojet

Post by Eric » Sun Oct 22, 2006 3:18 am

Heres some pics from the day time run this afternoon.

A quick pinch on the right injector with a pair of wire cutters fixed the imballance so now the fuel flow to each side is nearly equal. It runs a bit lower before shut off.

Eric
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re: Jims Little 3 Lb Thermojet

Post by Mike Everman » Sun Oct 22, 2006 3:59 am

Very nice motor, Eric. Jim's going to love it.
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re: Jims Little 3 Lb Thermojet

Post by Jim Berquist » Sun Oct 22, 2006 4:29 am

Eric!

Did you replace the cone aft the CC? I don't see where the other two inputs were! Looks good and clean , thank you!!!

Jim
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