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

[SundayForever]

Yes, D is smooth DC. This has removed one of the paper 1998_3879.pdf Kentfield UAV, which is essential reading.

The reduction may or may not work, start with these lengths for sure. A few things:

You need a hot fuel, hydrogen or acetylene at this level of CO2, so be extremely careful if you try. Do not confuse Whopper-purdle-lurdle for the race as a pulse-jet, that this size will be a cry very high.

It will not work if you turn tail out of there, or at least the chances are good, down run. Just a straight tube from the queue.

[TeiXalkidasSv]

Can anyone tell me how canI measure the frequency of my engine?

[Gmc]

i am new but have been in to rockets and jet engines for a few years and wondered if some of these ideas i designed could work
-use 4 jam jar jets on a shaft to create a radial engine prototype
-you could run a valveless pulse jet through a turbo charger and use a turbine air inlet so then when the pulse jet is sucking air in to the engine it will spin the turbine up and create more suction and compression
i would be willing to make a pulse jet as a project for materials tech and think some of these could be used for a rc plane or glider

[Mike Everman]

Can anyone tell me how canI measure the frequency of my engine?

There are a number of free FFT analysis utilities out there. I use Spear. Take a video or sound file and pop it in, and it will tell you the frequency.

[tcoleman]

If you have an Android phone get the app. "Gstring" it is a guitar tuner and free. just set it on autotune and don't stand right next to the engine( too loud , overloads the input). It will tell you the freq. to 0.1 Hz. Also "SprectralView" will give you a spectrum analyzer up to 8khz. Sigh.....technology..........

[bertwarm]

Hi I would like to build a 10 to 15 lb Thermo jet can u help me size the exhaust, intake, and combustion chamber. I was a sheet metal mech. at a shipyard and have the tig welder. I just don't under stand the sizing. I can make anything with some plans. I have plans for a 5.2 lb thermo jet but i would like to make a bigger one. Thanks bert

[metiz]

try this one: viewtopic.php?f=3&t=5877 it's a chinese style, but in the same size range, 25 pounds of thrust. It has small tollerances but if you are a sheet worker AND you have a tig then it should be no problem.

[bertwarm]

Thanks just what i was looking for
bert

[leakfree]

Is there a spreadsheet available for designing a valveless pulsejet? I built off of Beck's free plans with the exception of the combustion chamber which I used a propane bottle not paying close attention to the diameter difference of 1" larger. I have run it twice successfully but it is very hard to start. I also ran across the math somewhere for design and can't seem to find it. Also I have not seen any discussion about forming cones.

[metiz]

use "pyrojoe's recipe for beginners" on top of the vpj forum. use cone designer to easily create cone layouts

[PyroJoe]

Here is another way to make cones if need be:

viewtopic.php?f=7&t=5901

Its best to make the cones a few millimeters longer, so the ends can be trimmed cleanly to fit.

[leakfree]

Thanks for the quick responses. It took a little pondering to get an understaning of the design but it is clear now. Realized several mistakes in my first build. Will modify and keep plugging along. Going to work on the igniter tonight as my finger is about worn out clicking that bic! Pyro Joe do you roll your cones? I tried to with my first and it didn't work out too well mainly because the roller was set up for 4" and my cone was 4" to 1.5".

[PyroJoe]

If the engine is a smallish one, a slip roll is typically used to achieve the rough form.

viewtopic.php?f=7&t=1776

Fine adjustment to any high or low spots can be lightly hammered on a section of pipe or wood. At the work bench there are assortment of various diameters of heavy walled pipe for finishing. A inexpensive vise holds the pipe, as modest strikes true its form.

[leakfree]

Thanks Pyro! Those look simple enough to build. Have some 1" black iron laying around.
As a side note, I pulled the sparkplug and she fired right up without air, I'm stoked by this! Still has some more mods cause the flame barely shoots out the front. Getting excited about my next build.

[leakfree]

So I saw where someone mentioned using a transformer backwards to create a spark igniter. How do you do that?