Nanosoft's Craft Jet

[NanoSoft]

Hello and thank you for reading. I have recently been swamped with tons of homework (AP Physics, PreCalc, AP US History, Ext. American Lit, Sports med). Really sucks because i have no time for building jets especially with cross country in there too! So this weekend after a x-country meet I decided to make the craft jet as a quick simple project so I can a least get something running. I'll work on my other projects (Annular Jet, Turbo Jet) when I have big blocks of free time.

Anyways after one hour of delicate lathing and drilling I finished the valve head. Its very small(1 inch diameter). Tomorrow I will finish the tailpipe and start it up. Here some Pics.

Nanosoft

[Bruno Ogorelec]

Love it, Nano! Good stuff. Beats cramming.

[Stephen H]

"Note: After countless hours of trying to start the craft jet I have came to the conclusion that it dosent run. If i were you i wouldnt waste my time building one, even though it seems so simple. I have heard of one that runs but required major modifications to the original plans"

that is from Eric Beck's website! have fun trying though

[Mark]

Sometimes when you are making a very small single petal pulsejet, it helps if you can get as much arm as possible. The angle or bevel cut helps, but you can also drill the hole off center. If the petal doesn't get the correct amount of flex and flutter, the little reed won't cooperate. There's a real art to finding what works, and this takes patience. And conversely, the reed may fire off some backfire shots but never fall into a resonance, if the reed is allowed to swing open too freely. I suppose that's why a retainer is used on most reed designs, finding the window of opportunity without a retainer entails quite a bit of tinkering.
For the most part, if you are using .006ths spring steel, the reed should probably be around .75 inches long, but as with most anything, this is not written in stone.
One other variation to try would be a centered hole in the valve head but drill it out on the reed side off center, giving you more arm. Another way to achieve this effect, as with the craft jet I bought on eBay, was to afix an oval ring to the reed side which raised the reed up and allowed for the overhang of a longer reed.
I remember one occasion where I installed a petal valve on the head of my tiny Logan, it ran fine as a valved valveless; I guess you could say it was a variation on a theme.
Mark

[NanoSoft]

Finally found some .5 ID diameter pipe for the exhaust. Hope to weld it up with in the week.

Nanosoft

[Mark]

I'm sure you will find it rewarding when you get it running. The little size is still too loud to run without ear protection. Reeds are a little tricky to get a feel for, but you might get lucky on your first attempt. But don't get discouraged if you have to modify your design/selection of reed and head, it's just that "one" moving part. Too stiff or too flexy, that is the question. And too, sometimes the screw can be too intrusive or too close to the arm of the flex. A tinier screw is sometimes helpful. Some designs use a straight edge "washer" along with the screw so as to obtain even stress on the flexing motion.
When I used .003ths, a most interesting quiet buzzing sometimes occured when I lit the tail end after priming the insides and throat with a mist of methanol from a spary bottle. Maybe a perfume atomizer would be suitable. For many seconds the reed must have just barely and I mean barely swung open, and then the buzzing would build and the flame would then decide to advance up the tailpipe to the combustion chamber, breaking into a full grease whine. I'd liken it to lighting a 10 second time-delayed fuse.
Anyways, that's my 2 cents.
Mark

[Mark]

PS On my ~12 inch long pulsejet I just used a mirror smooth washer I sanded to get it super flat. If you use glass to sand on it is a good flat surface. I also used a fiber washer for sink faucets I think, which got the metal washer to seal good enough against my 3/4 inch diameter pipe/combustion chamber. The screw that pinned the reed down was very tiny and the reed .003ths. My reeds cracked after very short runs but it was a screamer, you wouldn't believe the sound. After grinding out the tiny reed on the grinder, I also sanded the edges so that the reed was ultra flat against the smooth washer/valve plate.
I think it was the most magical pulsejet experience I have had. Often when I lit the tail, it was if I hadn't even gotten the flame to the tail and it took off running faster than instantaneous, which tickled me to no end.
Mark

[steve]

Mark- could you post some pictures? I want to see this thing!

[Mark]

It's been so long and since it was pipe fittings I borrowed pieces for other projects, the endless washers I drilled and saved the myriad of chewed fiber washers/gaskets, that's about all that's left of it. It was a three segment pulsejet, 3/4 inch combusion tube/nipple, stepped down to a 1/2 inch nipple, and then the 1/4 inch exhaust tube. You will need three bell reducers, one for the intake head, one for the reduction to the 1/2 inch section, and one to adapt the 1/2 to the 1/4 inch exhaust.
Really that was all there was to it.
The simple key to making any of my valved pipe jets is this. Saw off a small ring of thread off a nipple and screw that into the head bell. This is what your washer or valve plate rests on and is sandwiched in place by screwing in the nipple. You will have to use very tiny screws if you want to use a washer valve plate. You have to leave a little room for the lip of the ring/threading so it doesn't hit the tiny screw that holds your reed.
I'll see if I can assemble the shape again when I get some time. It's really not too much work to make one, but it does take patience.
Mark

[NanoSoft]

I am trying to decide what fuel to run it on. I think it will be either methanol or acetylene. I don't have a small vaporizer for methanol so I will probably start with acetylene gas. Almost finished. Pictures soon.

Nanosoft

[Mark]

I just used something very simple, (and crude), a piece of tiny copper tubing elbowed in the throat with the fuel level right up to the top ready to get aspirated in. The vibration of the engine helps disperse the fuel a little too. I didn't mount the tubing in the engine, I only pushed the elbow inside the throat and let it rest on the bottom of the venturi. The tubing was held down on the board with a U-shaped nail. I sprayed a little fuel inside the jet and then sparked it over and over or tried lighting the tail, whatever seemed to get more revs or perks till it started. The tip of the fuel line was situated to be center height in the throat.
The jet rested on the board between two nails. I put a piece of wood under the tail to make it level. All very simple, no glitz. But it worked.
Mark

[NanoSoft]

Finally finished my Craft jet. After some testing I could only get it to run with compressed air and acetylene. It Screams! It a really high pitch and the CC glows a nice even orange. I think the problem is that I am using .006 spring steel instead of .004. I don't have .004 yet so until I do it probably won't run.

Here a couple pics of the finished jet after testing.

Nanosoft

[NanoSoft]

YES!! I got it to sustain. With a little more testing a finally got it to work by its self. The only problem is that my .006 valves last for about a min if that.

I've went through a couple valves already. Now i know first hand why valveless engines are so much better. Video will come soon. (After i make more valves)

Nanosoft

[Tom]

.....Woooooh! : oD I think i may have my first engine lined up now, if i can ever build one that is. This is great, though a shame about the valve life..
Congrats.
Tom

[NanoSoft]

THIS IS AMAZING!! First Ben the first valve broke at the half way point. The Second one was pushed through the intake. The third one broke like the first.

This is where it gets amazing! Almost worth starting a new thread. On my forth test run the valve broke at the base and flew out the exhaust but the engine kept running. I have successfully unintentionally converted the Craft Jet to a valveless. SAY WHAT!! Yeah I know its really weird. But I can successfully start it in valveless mode every time I try. Now this is most likely because I am running it on Acetylene. Later tests will tell.

CHECK OUT THE VIDEO (5 sec in .mov format)

Nanosoft