www.pulse-jets.com

Graham et al -

I love it when the pressure looks something like that! I assume that the yellow line is gas density. Density is the curve that I think we too often overlook - it's actually critical, because it's the one curve that shows us how we're doing at moving masses!

I think that in a "perfect" valveless pulsejet, you'd have an instant in time where you have something like that kind of uniform pressure distribution, a velocity curve that is practically a flat line (0 velocity) from end to end, and the front end "valve mass" AND rear-end "piston mass" fully loaded up, ready for the next shot. Remember, this is all in a single "snapshot" moment in the cycle. The density curve will show a fairly sharp break at the transition into the chamber (i.e. a short zone of turbulent mixing across the whole width of the front of the chamber), while the tail piston density will sort of "ramp up" from the chamber end to full density in the tail (cool air pulled in from the rear).

A correctly shaped and proportioned pipe will absolutely LEAP at any fair chance to get running!

One thing the density curve clearly illustrates is the displacement of the hot blast mass. In one cycle, the hot gas that blows out of the chamber through the intake tube is COMPLETELY replaced by the re-load of cool air. At the tail end, only the farthest gas from the chamber is fully displaced and replaced. As I have stated many times before, the blast mass from a single explosion never makes it out through the tailpipe in that cycle! You can verify this by looking at the velocity curve and relate it to the tailpipe length. It is IMPOSSIBLE for a molecule at the rear of the chamber to make it to the end of the tailpipe in a single cycle time. In a long, high tailpipe volume engine like a Lockwood, it must actually take many cycles for a given unit of blast mass to finally break out into the open (at the tail end)!

L Cottrill

James D where were you fueling this engine from when you got it running successfully? Were you using a straight pipe or had you pinched it slightly?

The fuel pipe was just a straight pipe 2.4mm inside diameter and located approximately as shown in the picture below.
I'm going to try a few small mods on this version and see if I can get it nearer to 3lbs of thrust, the intake flare was never as good as it could have been and I want to play with the intake length, running it on methanol would be a nice bonus too.

Larry Cottrill wrote:...calculated data for the five cones that make up the engine shell:

Front dome -
Outer Radius: 35 mm / Inner radius: 7.0 mm / Angle: 327.0 deg

Main chamber cone -
Outer Radius: 381 mm / Inner radius: 191 mm / Angle: 30.2 deg

Middle cone -
Outer Radius: 488 mm / Inner radius: 372 mm / Angle: 15.5 deg

Choke cone -
Outer Radius: 111 mm / Inner radius: 85 mm / Angle: 68.0 deg

Tail cone -
Outer Radius: 449 mm / Inner radius: 257 mm / Angle: 22.5 deg

Do these cone layouts still hold true for the final version after all the tweaks...


I haven't had time to totally wrap my mind around this message thread, but I think the cones didn't change, right?
I will eventually compare the full size color drawing from early in this thread with the last drawing (above) and see what has changed.
Not sure I'll ever have time to build one though.

Mark -

ALL the cones changed. You need to scroll down to the one with the 29mm chamber end and shortened chamber. This is of CRITICAL importance if you want good performance. Just don't try to use the "front loading" intake that plagued us for weeks!

L Cottrill

I couldn't find a drawing of it with those dimensions, but it's not important
right now anyway... I'll probably start by building the Elektra II since I already have
the parts for that in my laboratory.

Then, if I can't resist the urge (which I really should) I'll probably build
the FWE at this URL:
http://www.beck-technologies.com/media/ ... vanced.pdf

Which I think is your "Short Lady" if I'm not mistaken.

Can the FWE be scaled proportionally and still expected to work correctly?

I have an old bicycle that could be mildly propelled by a double scale
version of the FWE.

Anyway, i'm trying not to turn this into a hobby :lol:

I think I found it:
http://www.pulse-jets.com/phpbb2/download.php?id=7866

There was another message thread on the same engine:
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=3430

But it looks like that redesign was more troublesome than the first design (?)

BTW, what is the engine on that V tailed cruise missile at the upper left of the page
(white w/ a red stripe down the side)? Chinese Pulsejet?

I think your brest referance would be the FWE evolution thread. There is also a scaling sheet.
Good luck

Thanks.
I'll have a look at the FWE evolution thread.

I'll have to bounce that against the results data on Larry Cottrill's mainpage
http://www.cottrillcyclodyne.com/
where he does show that some were (up to this point) unsuccessful.

I think I'll start with the Elektra II, and then once I get our sailboat
rehabilitated (restored, sorta) I can do the basic"advanced FWE" engine.

I have some 2 or 2.5" and 1.5" stainless tubing I bought at the Boeing surplus
which is about the right wall thickness, so if I can scale it to a 1.5" exhaust tube
diameter I will have a good start on my materials.

BTW, where do y'all get the spark plug nuts?
I can get a threaded spark plug boss at auto parts stores & JC Whitney
(it's an anti-fouling spacer) but they aren't Stainless Steel.

I also need to post a question about welding stainless, after I try searching
old message threads.

Thanks again for the info and the pics.

I have never constructed one out of stainless as of yet..just to busy working with mild steel and experimenting although I will be building one or two soon now that I have purchased a TIG welder.

Eric has a very good price on 10M plugs and nuts as a set. I usually just weld the plug directly on a nut drilled out so the plug fits inside.

If you use a heavy steel nut you can weld it to SS with 609 rod. If you split the tube and form to the 1.25 ID it will work fine. It will probably run @ 1.5 but some thrust may suffer.

The KLM (keitha lyne may) unit I designed works excelent and is an easy build, you could use a single intake as in the FWE if you want, the light show is more dramatic than the FWE especially in the dark.
Enjoy

Is THIS the right dwg & dims for the KLM?

I ran into that file by accident when looking for Cone Designer.

It interested me so I bookmarked it.

I have a MIG and Oxy-Acetylene welder.
So far, I've been able to weld SS with MIG using flux core wire
(It's what I have). I have yet to hook up the gas (Argon/CO2 mix)
and use it as a real MIG. I have some Aluminum wire that I got
the gas for, but that welding project has not made it to the top
of my projects list.

I'm wondering if SS can be Oxy-Ac welded with SS welding rod
and if it will still resist corrosion (for marine use).
I can get beautiful welds with Oxy-Acetylene because it was
all I had for many years, so I got pretty good at it (though
I am a little out of practice, I imagine).

I intend to eventually get a TIG and Stick welder someday, but
for now I just use what I have (as always).

I did with my large pulse jet.

You must use a carborizing flame. If you don't the metal will just end up as slag.

I think the welding rod is 308.

Good Luck,

Larry is great at welding SS with Oxy Acetelene.

It also took me awhile to figure out if your weld break suddenly as they cool down, then you have too much metal in the bead. I had to grid it all down and start over in a couple of locations.

Cheers,

Sorry I just noticed I said 609 it should be 309 rod for mild to SS. You can use OA for SS but the long heat time degrades the crystaline structure and leaves percipitate inclusions, it will work but the quality will suffer.

You should also use some form of backing flux or purge on the inside of the welds no matter what method is applied i.e. Argon or Solar flux, your MIG unit would be the best method of the 2 but use pure argon not ACO2 mix.

If the dwg is the last one on the thread then Yes.
Cheers

I haven't gone to the message thread yet; I just have the dwg
I found in the files section:

http://www.pulse-jets.com/phpbb2/files/klm_854.pdf

Unforunately our lawnmower went kaput yesterday, so I may
not do any work on welding this weekend (Sunday I'll be looking
at flowers :roll: )

But I might do a little on the Elektra II if the mower goes better than anticipated.