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?