"Thunderchine" 55 lb thrust pulsejet plans

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GRIM
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by GRIM » Sat Feb 21, 2009 9:32 pm

Hi Joost Thanks for the comments ,

My “tiny mistake” was actually a BIG mistake, I did not follow the drawings ,
A Builder or Engineer who doesn’t follow the drawings would or should get fired !

Furthermore , I have spent a lot of time with a die grinder and angle grinder tweaking these cones to get them within tolerances , frequently the short cut turns out the longest route ,

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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by metiz » Sat Feb 21, 2009 10:05 pm

speaking of wich, how do you get your cones like they are - do you roll them? how do you cut, hand tools or a cnc/ similar?
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by Fricke » Sat Feb 21, 2009 11:15 pm

GRIM wrote:Storms coming,
The engine is looking nice!

1.8 mm it quite thick, but it should last long. =)

When is the maiden run scheduled??
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by milisavljevic » Sun Feb 22, 2009 7:18 am

Hermoso edificio, Joe!

Cannot wait to hear back with news of self-sustaining operation! Btw., if the beast gives you any
guff about starting up, you may want to consider covering one of the inlets until the duct hots up.

You have yet to mention what you intend to use for fuel; at full thrust, Thunderchine's appetite is
equivalent to 1200 ml/min (petrol) or 870 gm/min (propane vapour); estimated values (+/- 10%).

Black beauty: is that the special recipe or stove paint? Hope it protects this beast for a long time.

GOOD LUCK! :D

Cheers!
M.
GRIM wrote:Frequently the short cut turns out the longest route.
Hallelujah, brother! :wink:
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by GRIM » Sun Feb 22, 2009 10:52 am

Hi all
metiz wrote:speaking of wich, how do you get your cones like they are - do you roll them? how do you cut, hand tools or a cnc/ similar?
All hand tools in the back yard , I will post some pics , maybe a vid , but not here , tools n construction , soon,
Fricke wrote:When is the maiden run scheduled??
Hopefully this week ,
milisavljevic wrote:Cannot wait to hear back with news of self-sustaining operation! Btw., if the beast gives you any
guff about starting up, you may want to consider covering one of the inlets until the duct hots up.
I cant wait either , Good advice on the inlets, hadnt considered that,
milisavljevic wrote:You have yet to mention what you intend to use for fuel; at full thrust, Thunderchine's appetite is
equivalent to 1200 ml/min (petrol) or 870 gm/min (propane vapour); estimated values (+/- 10%).


Initial runs will be on propane vapor, (I hope), It is still warm here so the pressure is still good,
Thanks for the estimated fuel flow , that gives me something to aim for on the liquid (I HAVE A CUNNING PLAN ),
milisavljevic wrote:Black beauty: is that the special recipe or stove paint? Hope it protects this beast for a long time.
High temp paint for wood burning stoves , I have used it before , and it does burn off in the hottest zones , but some "make up" for the debut :wink:

Cheers, G

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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by milisavljevic » Sun Feb 22, 2009 11:36 am

Hola Joe!
GRIM wrote: Initial runs will be propane vapor [ ... ] Thanks for the estimated fuel flow,
that gives me something to aim for on the liquid (I HAVE A CUNNING PLAN)
If you need any help with your fuel flow calculations, please let me know.
With respect to fuel type (liquid), I can give you flow rates for whatever.
I can also calculate the correct orifice / nozzle sizes required for vapour.

Good luck scheduling a maiden, and thanks for building out so very fast!

Meanwhile, please have a good week start!

Cheers,
M.
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by larry cottrill » Mon Feb 23, 2009 1:34 pm

Man, Grim, that is looking just awfully nice. I'll bet this will be a mighty runner!

I have but one criticism: Your front and rear mounting struts appear to be pretty stiff in terms of forward/rearward motion. In my opinion, the rear struts should be flexible fore-and-aft (because of thermal expansion) while providing lateral stability. Probably not a serious matter for now.

Anyway, wonderful work!

L Cottrill

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UPDATE

Post by milisavljevic » Wed Feb 25, 2009 2:45 am

Hello Everybody --

Thread's not dead: activity has moved off-thread for the moment as we prepare for first fire.

Keep your fingers crossed!

M.
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avast!
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¡Viva la revolución!

Post by milisavljevic » Thu Feb 26, 2009 3:01 am

:twisted: UPDATE: Thunderchine self-sustains, frightened cows stop giving milk! :twisted:

Details to follow in later posting. Will edit 50 MB video for highlights; no thrust readings.*

Cheers!
M.

*ie., no thrust readings, this session

:D ¡Viva la revolución! ... and CONGRATULATIONS, GRIM! :D
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by GRIM » Thu Feb 26, 2009 4:29 pm

If Anyone is mystified by the “cows” comment, I shall attempt to explain ,

My test site was on a farm , and my test sesson was cut short by a farm hand running into the paddock waving his arms frantically , It would seem that the 260 head of dairy cows in the next field behind some trees, didn’t like the noise!! , once I had shut the engine down one could hear the din of the angry cows ,

I made my excuses , blamed everything on M and left , :lol:

M will post some vid and doubtless some comments when he is ready ,

G

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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by Irvine.J » Thu Feb 26, 2009 4:54 pm

Well, Other then cows, how did the engine go man!!!???
Surely you have comments to add after your initial test. We'd like to hear from you!
We are all waiting.

50 megs of video! Sounds good, sounds like you weren't shooed too fast! LOL
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by PyroJoe » Thu Feb 26, 2009 6:16 pm

Good to hear she is sustaining. Those cows didn't need their ear drums anyway. ha
congratulations,
Joe

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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by milisavljevic » Fri Feb 27, 2009 4:04 am

Irvine.J wrote:50 megs of video! Sounds good, sounds like you weren't shooed too fast!
In this instance, file size is more indicative of a lack of compression than a long running time.

M.
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Re: "Thunderchine" 55 lb thrust pulsejet plans

Post by GRIM » Fri Feb 27, 2009 2:39 pm

Here is a link to the previously mentioned video ,

http://www.mediafire.com/?yow2jjy0wha

I apologise to all concerned for the quality ,
Start up was tricky for me , and once I got the engine running I grabbed the camera and shot some vid , with every intention to re-run with the camera on a mount ,and get the start up etc , It was not to be ,

I also apologise for the delay in posting , the main cause was a difference in the predicted and measured frequencies , M will elaborate when he has time ,

As for my “experience” well “frightening” sums it up quite well , this is my first engine of this size and so I do not feel qualified to elaborate on the apparent power noise etc , all I will say is that it impressed the hell out of me ,

Further testing is pending , hopefully I will be able to get some better vid ,

G

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At the extremes of diameter

Post by milisavljevic » Fri Feb 27, 2009 3:27 pm

GRIM wrote:I also apologise for the delay in posting, the main cause was a difference in the
predicted and measured frequencies, M will elaborate when he has time.
Graham and Larry will remember this thread: "At the extremes of diameter I can imagine the answers are trivial."

Indeed they are. Thunderchine is so large, and so open, that the open-pipe mode completely dominates the acoustic
landscape. Combining this and the temperature at Joe's test site (ca. 30 C), we found his Thunderchine was running
out between 175-180 Hz, somewhat higher than expected. I asked Joe to audit his build, and was able to model his
comprehensive set of "as-built" dimensions late last night. At 30 C, Joe's "as-built" Thunderchine would be expected
to resonate between 168-173 Hz, about 7 Hz below the observed range. This difference is easily recovered if we use
the information discussed in the linked post, then treat Thunderchine as a predominately open-pipe mode resonator.

As I mentioned to Joe, the model suggests that the actual site temperature was rather closer to 31 C that afternoon.
Note to Larry: Joe's engine resonated strongly at F2, F3 in the video, corresponding to 320 and 480 Hz, respectively.

With respect to building a Thunderchine, the acoustic mode has no impact whatsoever on performance or efficiency.

Cheers,
M.

The following image was originally uploaded to the linked post, above.
coupling-segment_detail.png
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
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hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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