"Thunderchine" 55 lb thrust pulsejet plans

[GRIM]

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 ,

[metiz]

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?

[Fricke]

Storms coming,

The engine is looking nice!

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

When is the maiden run scheduled??

[milisavljevic]

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!

Cheers!
M.

Frequently the short cut turns out the longest route.

Hallelujah, brother!

[GRIM]

Hi all

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,

When is the maiden run scheduled??

Hopefully this week ,

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,

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 ),

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

Cheers, G

[milisavljevic]

Hola Joe!

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.

[larry cottrill]

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

[milisavljevic]

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.

[milisavljevic]

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

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

Cheers!
M.

*ie., no thrust readings, this session

¡Viva la revolución! ... and CONGRATULATIONS, GRIM!

[GRIM]

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 ,

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

G

[Irvine.J]

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

[PyroJoe]

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

[milisavljevic]

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.

[GRIM]

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

[milisavljevic]

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