FWE III Pulse Jet kit ROARS

[Dang911]

Well, first of all, I do have to apologize for the amount of time it took for me to finally get a video of this baby running, but at last, wait no more. This is the engine based on a partially prefabed kit. As I said in the construction topic of this engine, it was reasonably easy to build in a short amount of time, but a total dream to start. This engine starts right up every time, a perfect "first" engine to really get your feet wet.

Looking at the video, I pulled off a running frequency of around 254-258 Hz, would anyone like to confirm this? (its my first attempt at doing figuring a frequency of an engine by the sound in the video)

More comments and discussion to follow......

[larry cottrill]

Greg -

Great job! Whoever handled the camera was obviously excited about the running of this engine!

There are a couple of interesting things I noticed. You didn't have your fuel line pre-purged of air - you can actually hear the drop in pitch as it fills with propane, just before startup. Before that, you can hear the sound of your ignition coil "buzzer". Ha!

It looked to me like the flat "floor" of the intake channel (taking the place of a slice of the combustion chamber wall) was NOT running red hot. In running this engine, have you noticed this - i.e. can you verify whether this area is as hot or cooler than the larger chamber wall area? I'd be very interested in knowing whether any high temps can be observed in this area.

Good work! I'm glad you're enjoying your FWE!

L Cottrill

[larry cottrill]

Looking at the video, I pulled off a running frequency of around 254-258 Hz, would anyone like to confirm this?

I hear it right at Middle C, against my son's electronic keyboard (presumably the American standard scale, not the European). This is generally listed as 262 hz, although some sources give a "Scientific Scale" definition of 256 hz for Middle C.

Either way, your "measured value" must be very, very close.

L Cottrill

[Dang911]

Ok, so what's wrong with not purging your propane lines, you make it sound like its a big deal, hehe. Actually though there is an explanation for the swooshing sound. To start my engines I follow this sequence. First I turn on the ignition, (peppy sounding isn't it), then the propane. When I turn on the propane it ignites, but just like a grill ignition swoosh, the propane then burns as a fireball inside the chamber, I could leave this go for ever. Lastly I give a quick squirt of compressed air, and it starts right up. I live in Florida, so NORMALLY its nice and warm, and I only literally need a "less than a second" pop or air, it was 52 when I took this video, so as you can see I needed to hold the compressed air for about 2 seconds after the first false start. Still what an ease to start!!!

Its funny you mention a drop in pitch though. As you herd in the video my sparker puts out a nice scream. By placing a set of electrodes in different gasses, I could substantially change the sound (frequency) of the sparks; this obviously is from atmospheres effecting the speed of sound. Some gasses I tried were argon, nitrogen, helium, propane (no air), co2, and no2. All drastically varied the spark's sound and frequency.

VIDEO: I did this test out in a field off of the side of a highway. PITCH BLACK and the ground was un level, and the grass was tall. My friend took the video, but it was hard to walk around without stomping.

I have noticed exactly what you said about the heating of the bottom of the intake entering the chamber. I have two guesses to why this stays so cool, although at the very very end it just begins to glow slight red, after a nice run.

1. lots of cold air is being sucked in causing the whole intake to stay cool, even the bottom which also faces the heat of the combustion chamber.

2. The flow inside the combustion chamber, might be directed away from that part due to the onrush of air entering and exiting the combustion chamber.

Also, here are some pics of my fueling and igniting equipment.


What did frequency did your similar engine run at?

[larry cottrill]

To start my engines I follow this sequence. First I turn on the ignition, (peppy sounding isn't it), then the propane. When I turn on the propane it ignites, but just like a grill ignition swoosh, the propane then burns as a fireball inside the chamber, I could leave this go for ever. Lastly I give a quick squirt of compressed air, and it starts right up. I live in Florida, so NORMALLY its nice and warm, and I only literally need a "less than a second" pop or air, it was 52 when I took this video, so as you can see I needed to hold the compressed air for about 2 seconds after the first false start. Still what an ease to start!!!

I think you are basically getting Rossco's "guttoral" rumble - you're using the Rossco / Everman starting method. Sometime, try my method: You already know about what air pressure works, so purge your line, start your spark, turn on the air and immediately crank up the propane. Then, let me know your opinion on which is the most satisfying method. If you want to make a project out of it, you could even try this under various weather conditions. I'd just be interested in your opinion.

I have never (that I can remember) heard this "guttoral" rumbling combustion, though I have experienced some "howling mode" operation while pouring air and fuel into some very small engines. Maybe there was some "rumble" in my early attempts with the Elektra engines, and I've just forgotten about it. I don't have any video with such a phenomenon, I'm quite sure.

I have noticed exactly what you said about the heating of the bottom of the intake entering the chamber. I have two guesses to why this stays so cool, although at the very very end it just begins to glow slight red, after a nice run:

1. lots of cold air is being sucked in causing the whole intake to stay cool, even the bottom which also faces the heat of the combustion chamber.
Greg - I agree with this explanation - lbc

2. The flow inside the combustion chamber, might be directed away from that part due to the onrush of air entering and exiting the combustion chamber.
I do not agree with this one. The timing and flow of the air coming in and going rearward are too far off for the blast air to be influenced. There is a LARGE braking effect on the incoming air as it crashes into the front area of the chamber, and breakup into vortexing and turbulence - the forward and downward momentum is mostly dispersed before ignition, and the blast mass will easily move through there without any hindrance. - lbc

What frequency did your similar engine run at?

I never measured the frequency of the FWE IV "Smooth Lady". However, the one you built is virtually identical dimensionally, and I would expect almost identical frequency under the same conditions. Of course, I can't get the same conditions, normally - we are about 1000 ft above sea level.

L Cottrill

[Dang911]

I'm 6 feet from sea level BUHAHAHAH.

[hinote]

I'm 6 feet from sea level BUHAHAHAH.

Where do you live in FL?

[Dang911]

Weston, but its right next to Ft.Lauderdale

[hinote]

Weston, but its right next to Ft.Lauderdale

Oh yeah--hurricane country.

My bro lives in JAX; I'm going to visit him next month.

[Dang911]

Wilma gave me a direct hit. People had no power for 2 months, and no water for 3-4 days. Of the area 98% lost power, I was one of the 2% that never lost it, because of new state of the art underground wiring. I did loose water though, because the pumping stations didn't have any electricity. Gasoline was gone, and what gas was there couldn't be pumped because there was no power. Trees down everywhere, NO street lights for 1 month, and a lot of roof damage. My school suffered 8 million in damage when one building completely lost its roof, and that was a nice 2 week vacation for me.

Larry, back to your idea of a starting jig, look at what I used. For propane, I bought an off the shelf regulator for a turkey fryer (20psi) for $15. At the same time I also made a rig that works off of a small Benzomatic propane tank, with a modified torch, (65psi). I can use either one depending on what I'm doing. For spark, I made a timing transformer, using a 555 chip. It converts 12v DC to 12V AC@100Hz. Just run that into an ignition coil, and your set!!

I will try your starting method, but honestly I can't see it making difference in how this engine could start. It starts immediately, regardless of having to hold the air for just a sec to up to 2 sec. Never have I had a failed attempt or difficult start. If your way works, it will have to be just as fast, because I consider the way it starts now instantaneous.

I think it might be time for some experimentation with a liquid fuel (white gas), you think that would gross more power? Any Ideas on the setup?

[larry cottrill]

I think it might be time for some experimentation with a liquid fuel (white gas), you think that would gross more power? Any Ideas on the setup?

White gasoline will almost certainly be more powerful, if you can get it to draw properly and mix well. I would have it go in at right angles to the air flow, terminated in a VERY small hole in the end of the pipe (no. 50 drill size or possibly even smaller). The port should be as close to the center of intake cross-sectional AREA as you can get it. There MUST NOT be any air leakage into the intake at the point where the fuel pipe goes in, because it will kill the Bernoulli suction. Have your liquid level about 1/2 inch below the port location for starting. If it runs, it should draw much farther than that. Horizontal distance is meaningless as long as your tubing is 1/8 or even 3/32 inch ID.

Of course, I've never succeeded in doing it, so my advice is highly respectable ;-)

L Cottrill

[Najm]

What's the thrust?

[Dang911]

If I had to guess somewhere between 3-5lbs., not much, but it is very small.

[hinote]

For spark, I made a timing transformer, using a 555 chip. It converts 12v DC to 12V AC@100Hz. Just run that into an ignition coil, and your set!!

Dang:

Your circuit looks quite a bit simpler than others posted here, using the 555.

Can you post a simple circuit diagram for us?

BTW it's also easy to see that you took the time to do the job right. Strain relief, grommets, etc. Worth the effort, I say.

[Dang911]

No probably.....

Not hard to build at all, but yields great performance, and with the beefy mosfet I have chosen, it will run forever without burning up. The mosfet is what is switching over the power, doing all the real work, the 555 is just timing everything, if you wanted you could even make it variable frequency, with a variable resistor.

I built my ignition box to last. I made sure it would be rugged so I could build it, and never worry about the circuitry. I have had my 555 blow out on my once from a failed diode. This however happened immediately when I first built and tested it. Do yourself a favor though, put the 555 in socket!!!

Ignition coil Parts list


Capacitors
2 100nF (0.1uf)
1 220nF (0.22uf)
1 polar 47uF
1 0.22uF - points ignition coil condenser

Fuses
5 amp with mounting clips

Resistors
2 10k
2 10R
1 100R

Transistors
1 bc548
1 bc557
1 irf630 mosfet or A40N25

Diodes
in4004

IC Timers
1 ic555 with socket mount (ne555p)

Ignition Coil 20-100KV