www.pulse-jets.com

Hello Metiz,

A few meters above or below sea level makes no difference to me; temperature and pressure are fine.

metiz wrote:M., don't take this as an insult but I'm going to try to lengthen the pipe on the existing engine incrementally.

Indulge yourself, mate. It is your time and money, after all.


I never said the set of dimensions I provided is the only set that will result in a self-sustaining engine.

It is the best set that I could find that would meet the constraints imposed by your design, reaching a
full pound force of thrust (454 grams), and with its intake pipe properly aspirating the combustor can.

A shorter intake will not aspirate the combustor properly, but will permit a shorter tailpipe. It is quite
easy to solve this system of equations for your configuration; I can provide alternatives if you wish it.

If you are so inclined, hoist your signal flag and Cap'n M. will fire off a dimensional broadside for you.

Cheers,
M.

Hello Metiz,

I took a minute to punch up a less-than-optimal, but shorter configuration for you to try.
Here are the dimensions you need for this "mid-gun" engine; please follow them closely:

[1] intake ID 22 x length 79 mm; intake length includes an ID 31 mm flare
[2] combustor ID 60 x length 57 or 64 mm; match length to tailpipe length
[3] tailpipe ID 22 x length 598 or 591 mm; overall internal length: 655 mm

The shorter combustor will yield the better runner with a max. thrust of over 400 grams.

Why not switch to a linear configuration? It could be fairly short and deliver more thrust.
It is not like these pulsejets will do more than make noise, thus a u-bend is not required.

Cheers,
M.

Hi Metiz,
FWIW
Built a few like those in the past and had a hell of a time myself. One problem is in the narrowness of the CC. It is much better to keep them up in the 75mm diameter range when using propane, but I understand the availability of materials issue also.

Here is a layout that should be easier to start. It has taken some time to understand why this works well. (Rubbed my two best neurons together to the edge of fatigue). ha

Once I saw the trick played, it is kinda obvious. If possible, offset the center line of the tailpipe to the edge of the CC, and add a small piece of angle cut pipe to about the half length of the CC. It does require a little more welding/work.

No reasonable speculations on thrust from this layout, but I do hope it helps ease some frustration with starting.

Joe

Yay succes. first "increment" worked. It was pretty easy to start after I found out the right way to do it. Good throttle responce, a red hot engine and a lot of noise - good shit!

Good one Metiz!
So what were the final dimensions?

Hello Metiz,

Congratulations, dude! I replied to your PM: "Faaaaassscinating" stuff.

Cheers,
M.

Jutte wrote:Good one Metiz!
So what were the final dimensions?

Sorry mate, trade secret

Ha,
Good fix! Had to run it through a calibrated eye to see the change.
Joe

metiz wrote:

Jutte wrote:Good one Metiz!
So what were the final dimensions?

Sorry mate, trade secret

Kinda like a black hole. Absorbs light without reflecting any.

If I do get result, I'll ofcourse post the dimensions and the temp/elevation/ video of it

promises, promises......sigh.

I suppose if someone happened upon a CC of that dimension, and pipes of that ID and wanted to duplicate this engine rather than run some other perfectly runable combination, they wouldn't be far off if they made the exhaust of the third engine let's say, uh, ballpark 58 cm or so......

vturbine wrote:

If I do get result, I'll ofcourse post the dimensions and the temp/elevation/ video of it

promises, promises......sigh.

Oh But I DID post that information - just not here

vturbine wrote: I suppose if someone happened upon a CC of that dimension, and pipes of that ID and wanted to duplicate this engine rather than run some other perfectly runable combination, they wouldn't be far off if they made the exhaust of the third engine let's say, uh, ballpark 58 cm or so......

CURSES! ....eh I mean...no
I'll post something much better than this engine soon enough buddy

gracias!