Search found 4142 matches

by larry cottrill
Fri Apr 30, 2010 8:01 pm
Forum: Valveless pulsejet forum
Topic: Big Linear FWE for a Paying Client
Replies: 60
Views: 15676

Re: Big Linear FWE for a Paying Client

Hey Larry , glad to hear your engine worked out , I need to clarify one thing , I guess it was misleading in my pm , I do indeed have several different sizes of these injectors ,but i was not suggesting that i want to make or sell them , getting into the pulsejet market is not one of my goals :lol:...
by larry cottrill
Fri Apr 30, 2010 4:47 pm
Forum: Valveless pulsejet forum
Topic: Big Linear FWE for a Paying Client
Replies: 60
Views: 15676

Successful Testing

Grim PM'd me suggesting I try one of his "three point" fuel pipes -- the ones made by pinching a tube with a big 3-jaw Jacobs chuck. By the time I got his message, I had already made one this way and it worked excellently! I pinched mine with a 1/2-inch chuck and 3/8-inch steel brake line. I finishe...
by larry cottrill
Fri Apr 30, 2010 4:34 pm
Forum: Valveless pulsejet forum
Topic: Big Linear FWE for a Paying Client
Replies: 60
Views: 15676

Re: Big Linear FWE for a Paying Client

You might want to consider drawing liquid propane and building an evaporator. . . . The cylinder won't ice-up when you're drawing liquid because there's only a tiny amount of vaporization going on there. Bruce - I hypothesized that this would be a good method a year or so ago, but never tried it. I...
by larry cottrill
Fri Apr 30, 2010 4:07 pm
Forum: Valveless pulsejet forum
Topic: pulse jet theory V o.1
Replies: 28
Views: 7848

Re: pulse jet theory V o.1

Paul - In comparing Pyro's example with mine, keep in mind that his is set up with the intake on the left end, mine with the intake on the right end. I set mine up that way because the intake is usually where I change things most often, and with UFLOW it is much easier to make changes on the right e...
by larry cottrill
Fri Apr 30, 2010 1:16 am
Forum: Valveless pulsejet forum
Topic: pulse jet theory V o.1
Replies: 28
Views: 7848

Re: pulse jet theory V o.1

I never tried Uflow but the graphs are near identical to what NUDiS produces. Does Uflow have the same core functionalities as NUDiS? NUDiS is more fully developed. They are both basically 1-dimensional analyzers, and I assume the same underlying fundamental gas equations are used. Only Graham Will...
by larry cottrill
Thu Apr 29, 2010 10:46 pm
Forum: Valveless pulsejet forum
Topic: pulse jet theory V o.1
Replies: 28
Views: 7848

Re: pulse jet theory V o.1

I'm afraid I'm not seeing three reversals (positive to negative and back) which of the of the four graphs should I be concentrating on. :( All the views are important and interesting in some way. To me, the Mass Flow graph (lower right} always looks like an exaggeration of the Mach No. graph (upper...
by larry cottrill
Thu Apr 29, 2010 1:42 am
Forum: Valveless pulsejet forum
Topic: pulse jet theory V o.1
Replies: 28
Views: 7848

Re: pulse jet theory V o.1

Oops ... my apologies. You did say "second harmonic". I think everything you've just stated above would be correct. Keep in mind that the wavelength in the pulsejet and thje wavelength of the radiated noise will be vastly different, because of the temperature difference between the jet interior and ...
by larry cottrill
Tue Apr 27, 2010 4:04 pm
Forum: Valveless pulsejet forum
Topic: pulse jet theory V o.1
Replies: 28
Views: 7848

Re: pulse jet theory V o.1

Paul - You might want to see an animation of the waveforms in a real engine. Go here: http://www.pulse-jets.com/phpbb3/viewtopic.php?f=10&t=4761 and run the second little movie file. The first part of this is two brief animations of the waveforms in my Lady Anne Boleyn engine. First there is a slow ...
by larry cottrill
Tue Apr 27, 2010 12:41 pm
Forum: Valveless pulsejet forum
Topic: pulse jet theory V o.1
Replies: 28
Views: 7848

Re: pulse jet theory V o.1

Paul - At the high gas temps and low densities at some locations within the pulsejet pipe, the speed of sound is MUCH higher than in normal air. The quarter wave will propagate much faster in the tail section (always hot) than in the front end (intake, almost always full of cool outdoor air). It is ...
by larry cottrill
Mon Apr 26, 2010 4:06 pm
Forum: Valveless pulsejet forum
Topic: Acoustic length
Replies: 13
Views: 3024

Re: Acoustic length

Thanks, Viv! Good to hear from you. I am down sizeing a PJ i made , I am almost done we will see if it will run, If not it will look cool. I will post pics tomorrow if i can Nick - Good luck! The best that can happen is that you will be VERY fortunate and have a running motor. If not, I'm sure you'l...
by larry cottrill
Mon Apr 26, 2010 12:18 am
Forum: Valveless pulsejet forum
Topic: Acoustic length
Replies: 13
Views: 3024

Re: Acoustic length

But shouldn't the scaled up version of the engine have its own natural resonating wavelength that it will run at when started up? Why will the acoustics go off? The engine should just resonate at a new frequency and be as efficient as the original. It is a kind of pulsejet truism that a conventiona...
by larry cottrill
Sun Apr 25, 2010 3:12 am
Forum: Valveless pulsejet forum
Topic: pulse jet theory V o.1
Replies: 28
Views: 7848

Re: pulse jet theory V o.1

So imagine a four foot Lockwood in operation, what is it? According to Cottrill's hypothesis, it is a low-Q quarter-wave resonator one foot long and a high-Q quarter-wave resonator three feet long operating symbiotically in perfect synchronization. The absence of a reflecting wall at the pressure a...
by larry cottrill
Sun Apr 25, 2010 2:34 am
Forum: Valveless pulsejet forum
Topic: Acoustic length
Replies: 13
Views: 3024

Re: Acoustic length

That's a neat question. I'll make a guess, since no one else has spoken to it. (This will probably be wrong ;-) If we had the super simple case of a pipe that was full of stationary air of constant temperature and density (like an organ pipe at ordinary temperature), I think we would have no reason ...
by larry cottrill
Tue Apr 20, 2010 4:56 pm
Forum: Valveless pulsejet forum
Topic: Big Linear FWE for a Paying Client
Replies: 60
Views: 15676

Re: Big Linear FWE for a Paying Client

Hey Larry Looks like things are shaping up. good work! Any chance you could videotape your 5 minute attempt? Thanks! Yes, I should get back to video this time. My latest problem is, I can't get my video capture to work well. Playback on the camera appears OK, but my capture card and/or software kee...
by larry cottrill
Tue Apr 20, 2010 3:54 am
Forum: Valveless pulsejet forum
Topic: Big Linear FWE for a Paying Client
Replies: 60
Views: 15676

Roaring and Red Heat

Got a brief run Saturday with the low speed fuel pipe. However, even with that pipe it took 60 PSI on the gauge to get the volume needed! When I tried to duplicate it today, I couldn't get anywhere with it. The low speed pipe seems very sensitive to the slightest variation in position and/or procedu...