Please put your "I am new and need help" question here.

[metiz]

I agree mostly with Pyro, except for the coupler. I suggest this.

[PyroJoe]

Oh.. forgot about that one, best to do it as metiz has shown, that way the seams match better.

[tcoleman]

Sweet, one last question (yea right), if the ID varies a little, only so many sizes are available,
should the total length of the intake vary to match, volume matching assumed.
Or just stay in the .88x to .7x dia. and fix the length.
Thanx. Todd

[PyroJoe]

"just stay in the .88x to .7x dia. and fix the length"

Don't sweat the volume as much. Try to find as close to the 0.88x as possible, maybe even slice a larger pipe and hammer/weld it closed to achieve the I.D. Try to maintain the minimum intake length/path.

A little work here will save considerable time and fuel later.

[tcoleman]

Thank you gentlemen, this is going to be fun!

[PyroJoe]

Happy weldings,
Let us know how you get along.

[anand7]

is there any way to calculate the thrust of a pulse-jet theoritically using formulas without any practical work?

[tcoleman]

I'm sooooooo happy! Thanx guys. It runs. Can be a bit hard to start but there is no velocity stack on the inlet and the injector could stand a little tuning BUT ears do bleed. The GRIMs 3-point injector although real cool just wouldn't run without constant air injection but the ol' Rossco injector burped, popped and took right off! Seems to run at 207Hz (will verify and look at harmonics in the future) but very little thrust, if you pick up the mounting board while running you can feel a little thrust, will measure after the weekend. Check it out on the Tube:


http://www.youtube.com/watch?v=6ziUBQ36kUw

(hoped that works) Thanx again guys!!!!

[metiz]

good job, it seems to run nicely. You can expect much better results if you flare the intake (while not decreasing the length of the intake) That is probably also the reason it won't run with the 3-point, It can't get enough air. The Rosscojector forces air in to the intake due to its shape, that's why it runs as-is. I'll bet you don't have a lot of throttle control(?) fix the flare and your problems will most likely be over.

[ganuganu]

that was really hot run ..congrats..

[PyroJoe]

Those don't make much thrust in the bare form. They pour pressure out the intake and are very off balance. Basically they are easy to start and help to get the feel of it. Constructing a tail expansion will start to balance it better.

A intake augmentor will add the "captured" mass in front of the intake and will balance the engine further, and apply the pressure to significantly more trapped mass. Almost like a "double pump".

Ha, thats a good looking engine for a chinese style. The linear versions start very easy.

Good work

[tcoleman]

Ok, now I'm real sure I want a tail pipe expansion. Which is better, a continuous cone or a cone and straight pipe(stepped)?
Also how should I calculate the dimensions? I remember seeing it somewhere but can't find it now that I want it, go figure.

[PyroJoe]

There is a basic expansion here:
viewtopic.php?f=3&t=5914

Just a few rows down in "PyroJoes Recipe for Beginners"

found under PART 2

It gives the expansion process in 2 parts, so you can observe the differences as the expansion is advanced.

[tcoleman]

Ahhhh, hiding in plain sight!

I already want to do a bigger one. Thinking about hydroforming it.
If you are not familiar with this checkout youtube they have a number of demos.
It looks like you can simply make just about anything with enough pressure.
The nice thing is ...no dies! Just imagine it and inflate it!
Thanx a bunch.

[TeiXalkidasSv]

How can you determine the frequency of the engine for a lockwood type of engine?
Both practilly and theoryticaly?
And what kind of relation has this frequency to the acoustic resonance of the tubes?