Maggie Clone Runs

[larry cottrill]

Well, while most of the forums' heavy hitters are out in the vineyard, a school teacher and his students got their Maggie Muggs ramjet clone to work, with what appears to be a big shop vacuum and liquid fuel. Unfortunately, I haven't heard back from him regarding permission to use the photos and descriptions, but if I get that, I'll post what he sent.

The Maggie clone looks pretty nicely crafted. The tail cone is not as smoothly contoured as my original, but has a nice tapered nozzle that should work fine for a low-speed jet. The most visually impressive picture is a kind of flame-thrower effect with a yellow flame a couple of feet long out the tail, but of course that's way too much fuel for the air being supplied. There's another shot with just a yellow feather or two, and that might be a pretty good run, with the blue flame just not visible in daylight.

I think their only real problem is [probably] an inadequate air supply, and I've advised that they need to find something with really good velocity, like a big leaf blower, to make it go the way it should. It looks like they never got enough combustion to get close to red heat in the nozzle.

I also got a [presumably] tongue-in-cheek email from a fellow who claimed that the Maggie design has been around longer than I have, with some pictures of one of those "jet" type garage heaters, including some internal views. As you might imagine, it is a fan-driven blower in front of a propane burner. The "flame holder" is a metal plate with a ring of circular holes - exactly the same principle as in Maggie Muggs, but a lot more of the plate and a lot less of the holes. As a "jet" goes it looks pretty bad, essentially a pressureless engine, but sure enough, the principle is there. Now, here's the interesting part: This fellow claims that the "thrust" of the thing actually makes it creep across the garage floor if left free to move! [I can't tell if it has little wheels or skids, or what.] If that's actually true, i.e. that there is really some observable thrust from such a crude device, that makes the possibility of a lightweight low-speed ramjet seem much more attainable, don't you think?

Comments / opinions? Anybody have similar experience with one of these garage "jet" heaters?

L Cottrill

[larry cottrill]

Teacher Randy Autrey sent the following, with photos shown below:

Larry,

You may use any or all of the following on jetZILLA or
wherever you would like.

My name is Randy Autrey and I work at Gould Academy,
a college preparatory boarding and day school in the
western mountains of Maine. I am a private pilot and I
also fly model airplanes. One of our students at
Gould, Ben K., saw the Maggie Muggs project on the
internet and asked if I could use it to fly one of my
model airplanes. I told him it looked like a fun
project and that we should build and test it. That is
exactly what we did.

We grabbed some freebie mugs from faculty members and
bought a sink strainer at Wal Mart. Ben used a dremel
tool to cut the mugs and we drilled a hole for the
brass tube injection system. We used JB weld to
assemble the mugs with the understanding that it was
only rated for 600 degrees F. Our first test fire was
with the small drilled brass tube which was flattened
in the center for a spray bar. We used a model
airplane fuel bottle to pressurize the gas mixture for
injection. The mug did ignite and produce a flame. It
was immediately obvious that we did not have enough
fuel. We went back to the lab to change the injection.
This time we just flattened the end of the brass
tubing and JB welded the tube to the front of the mug.

As you can see from the pictures we had plenty of
fuel. I like the pressurized bottle injection system
because you can control the flow. We started out with
light pressure during ignition and increased fuel
delivery as we increased shop vac air flow. You can
see this transition in the series of pictures of the
big flame 'blow torch' look during ignition to the
chiseled flame near the end. Just when the sound
changes and the flame becomes a chiseled point it is
time to shut down. This produces a lot of heat very
quickly when it hits efficiency.

This is a great project with very low cost and
construction effort. This was great for the students.
We are very pleased with the results. This Maggie Muggs
really draws a crowd.

We are planning on firing it again but this time we
will run it at night to see the transition from
ignition to chiseled flame. We hope to have a video
clip available soon. Stay tuned for more. We started
working on a valveless pulsejet so we will let you
know how that works out.

I would like to thank Larry for a fun design and all
of the emails he sent. Great job Larry.

EDIT: "All of the emails" did not copmprise a big bunch of technical advice. It was mostly just me encouraging him to find a bigger air supply for testing! - L Cottrill

[steve]

wow, that is pretty impressive, and they used liquid fuel too!

I've been considering trying to build a ramjet for awhile, and this has convinced me to go ahead. I will (eventually) build a miniture version of the ramjet used on the rotor blades of the infamous hiller helicopter, which a got a good up close look at when I visited the national Air/space museum two weeks ago.

[larry cottrill]

Steve -

Yes, I think they really used a simple, direct approach. Very effective, and yes, very impressive results. That really encourages me to finish up my thrust stand and get my own Maggie tested.

Those Hiller rotor-tip ramjets always seemed impressive to me, though I've never seen any good up-close info on them. There are many problems to the whole tip jet rotor idea, but that one probably was about as good a scheme as you can get. Of course, such things usually seem simpler / better than they are ...

L Cottrill

[Ray]

Those Hiller rotor-tip ramjets always seemed impressive to me, though I've never seen any good up-close info on them.

I don't have info...but I do have a couple photos of one...This one is located at the Boeing Museum of Flight in Tacoma, Washington, USA.

[steve]

I think your pics came out beter then mine

[Mark]

Here's 2 ten pound engines doing their stuff.
Mark

[Mark]

Propane ramjet. How short they are.
Mark

[Mark]

Hiller stats.
Mark

[Mark]

Another Hiller page.
Mark

[Mark]

Assorted ramjets.
Mark

[Mark]

Bristol ramjet.
Mark

[mk]

Congratulations to you for getting the Maggie Muggs clone running!

Cool.

[RG Rhodes]

Howdy Mark-

Say, on your post above, labeled "assorted ramjets", middle pic,
is that a linear ramjet? Looks neat.

RG

[Mark]

It is as it says I guess, a tip mounted ramjet, ala pancake profile. I suppose you could incorporate a ramjet into a wing structure too.
It just looks like a gulper of air in a flat profile.
Mark