www.pulse-jets.com

After many hours of rolling and welding I decided to look at other, easier ways of manufacturing a Valveless Pulsejet. One thing that came to mind was building a Ceramic PJ. Obviously if this worked, the jet could be run indefinitely as there is little chance of it melting.
Possible problems are
• Weight
• Brittleness
After building it, I’m pretty sure when it’s dried, it will actually be lighter than its metal friends.
As for its brittleness, I think the clay I used should be able to cope with the stress as it’s designed for oven wear, plates etc, and am I right in saying if a PJ was to go wrong it would implode rather than explode? Well, a tube is essentially two arcs, and ceramic will work well under this form of stress/strain...I will keep this thread updated - from designing right through to building and testing. If it works, it could be a very cheap way to build prototype jets, and maybe even flight jets.

Okay - so my jet of choice is the Lady Anne - as designed by Larry. (thanks). Stupidly i only managed to find the plans for version two, then as life goes, i realised we are up to version 6! After id built it! :-(
I first re-drew the plans on to autoCAD to get some more dimensions

I then drew out the sheet layout on card, and used them to mark and cut the clay.

I rolled the tube sections around a bit of dowel, and cut the clay using a craft knife - pretty simple stuff really!

The cones where then rolled together by hand - it was very easy to form them and make then look very good. To "weld" them together, i roughed up the edges using a scraper, i then sprayed on water, and used my thumb and forefingers to fuse the clay together - i then smoothed over the outer edge using my fingers making the seam invisible. On the inside of the cone i used a plastic edge to make it smooth.

Once all the parts where created - it was time to stick them together. i started of by attaching the inlet tube. This was done the same way as making the cones. Roughing, watering, then fusing together - ensuring a smooth flowing surface between them, this is very easy to do in clay.

Once all the pieces where together, i inserted a plastic tube to ensure it remained stable through drying, at this point i cut the inlet tube to length, flared - by using dowel. I also added the end cap, and pushed an old spark plug through to make the hole.
One thing you need to remember when working with clay is how much it expands, the hole for the plug can be easily adjusted once its fired rock hard with a dremel multi tool.

So here she is, the beautiful ceramic Lady Anne - this really is a beautiful jet and im sure when she is fired into stone, she will be even more beautiful!
Its going to take her a few days to dry, then a few days to go in the kiln....soon as shes is ready for testing i will let you all know, and we can see what happens! Any questions - fire away! ;-)

Good work there. Something I've always wanted to see attempted. If you have some leftover clay, maybe you could make a little jam jar to humor me. I like jam jars very much.
Mark

If you have a piece of that material that has already been fired, what you could do is put a torch to it and see if it cracks from the thermal shock. My clear ovenware glass/Pyrex pans and chalk white casserole dishes only recommend use at 350 F.
Thinner material is less likely to crack. If your test piece of clay does crack you might want to very slowly warm your Lady up and then hit the high heat starting mode.
That's what is neat about fused quartz, it can take the high and low heat fluctuation without damage because it hardly expands.
Mark

Maybe try a little chopped carbon fiber mixed in with some left over clay. Looks great, cant wait to see it run :)

Eric

Cheers guys, ill try both recommendations. Carbon fibre is one thing i have considered, and if this clay doesnt work, there is an extensive list of ceramic composites i can try. The Lady took a couple of hours to build, but i reckon i could do it again in 1. So there is no problem in lots of testing. I also have access to an entire Engineering testing lab at my university to do some analysis. Im Excited now for the results!

Craig -

Don't know if you caught it, but several months ago I tried to get a supplier of super high temp ceramic products to get me a price on making these. However, they decided not to take it on. I'm sure the initial setup costs would have been in the tens of thousands of dollars, at least. But, on idea I had was to make the engine mounting a streamlined 'monopod' - imagine this as a T-shaped appendage at the bottom of the engine cross-section, so the very bottom is a flat base about as wide as the chamber front end. I think that would have been very cool indeed. I think the reason they didn't like the project was the requirement for the shell to be very thin all over.

I like what you're doing very much - only the intake has a rather 'bulky' look, due to the material thickness. Beautiful work, though! I can hardly wait to see what it looks like fired. (You might think up some really wild glaze pattern for the first one. Of course, I realize that would add several hours to the whole process ... ;-)

I wonder if the spark plug mount isn't going to be tough to get right. On my attempt, I was going to specify a stainless insert for that, and for the fuel pipe mounting gimmick as well. I have no idea how well that would have worked, although the rep said they have done it before!

Good luck!

L Cottrill

Well cheers Larry, I think I missed that, I’m the new guy!
As for the crazy glaze, that will be in my "1960's Psychedelic Range" he he

The clay has now dried and has been put in for firing, fingers crossed it doesn’t crack!
I’m worried about the spark plug too, I’m pretty sure for now a tight fit, and fire cement will do.
The picture below is your lady (Version 1) in AutoCAD 3d, I did it mainly as a learning exercise, if you want the original dxf, let me know.

Dang! I can't believe I haven't seen this yet. Craig, thanks, that beautiful build made me laugh out loud! That is priceless; way to go, man.

craigclavin wrote:Okay - so my jet of choice is the Lady Anne - as designed by Larry. (thanks). Stupidly i only managed to find the plans for version two, then as life goes, i realised we are up to version 6! After id built it! :-(
I first re-drew the plans on to autoCAD to get some more dimensions

I then drew out the sheet layout on card, and used them to mark and cut the clay.

Nuts! In my enthusiasm, I missed this before: Your layout actually appears to be the Revision 3 layout, and I'm sure it will be a problem ... it's one that we never did get to sustain. Rats! Of course, this doesn't mean you can't test it, just that to heat it up you'll need to keep the "starting" air running to keep it roaring. Maybe for your first shot at this, that won't be too much hassle. To make it easier, you should try to rig a "permanent" air pipe that aims right down the center of the intake throat, so you don't have one hand tied up aiming the air.

Sorry this didn't click with me earlier - of course, it wouldn't have mattered much, since you had it all put together anyway. That's one problem we have with our "online research" projects - people will take off and run with a design before we finish finding out what's wrong with it ;-) Fortunately, in your case, building a new version appears to be a fairly easy process (though the drying and firing make each iteration somewhat time-consuming, of course).

Do you think you'll actually do some glazing, or would you rather not take the time for the extra firing that will take? Just curious ... it would be really fun to see one with a wild glazing scheme. A friend of mine (an architect) I worked with decades ago did wheel-thrown pottery (sometimes intentionally distorted in the final moments) and was into experimenting with glazing patterns and materials. Pretty fascinating stuff. It occurs to me also that any porosity or "micro" roughness on the inside surface would create a much different condition at the flow boundary than what we are used to thinking about.

What would you think about casting these with a thin slip over a form that could be burned away (kind of like 'lost wax' methods)? I realize that a slip doesn't usually provide the strength of normal clay. I was thinking about some of the really high-temp stuff that Mark just came up with a couple of days ago. I suppose a slip casting has a lot higher level of shrinkage during drying, too. If it was easy, everyone would be doing it ...

L Cottrill