Makings of first valved

[Irvine.J]

Well, I now have 4 full time projects going, one of which is my first valved engine. I wasn't sure about the thickness of your shim steel, so here I have 0.010mm, prolly not thick enough to last long, but meh. Its for a 2.5kg valveless. I'm sure its been mentioned before but whats a good valve thickness 0.035 I think someone said?

Anyway, I'm not going to waste any more aluminium casting in the yellow stone either, the water bursts from cracks and the steam is what's destroying my casts according to some metal workers, who are gonna hook me up with some good fire clay stuff a little later.

As always, i printed out the dimentions on paper then glued it to the metal to be worked so it would be spot on, does this look ok. I will try a twin V valve a little later, I believe it to be easier to make then the wedged ones.
The projects to come are 2 valveless and this valved engine, plus the putting some finishing touches on my ramjet.

[dynajetjerry]

Irvine,

If my math is correct, .010 mm is .0004 in. and that is much, much too thin for any valved p-j. Even .004 in. (ten times as thick,) will be marginal. Also, once you get the proper material for the valve, you might be well advised to trim the corners of the petals, perhaps radiusing them to the greatest extent possible without uncovering any part of the ports. OK?

dynajetjerry

[Irvine.J]

Thanks Dynajet for responding on this one, Ok so maybe a good .35mm not .035. Perhaps if you know the inches thickness recommended I can get an idea of what suggested to be "Standard". Yeah I need to trim the petals to a nice rounded shape, this is my first try and just getting a feel for the retainer and cutting really thin petals. Cheers for the help, what would you say in inches is a good metal thickness?

[Mark]

.006ths is typical for a Dynajet sized engine. The largest thickness is usually .010ths, maybe a few have ventured into the .012ths but it's unlikely.
If you have a source for old outboard engine reeds you will find most of them are the thick .010ths .
http://tinyurl.com/yja697

[dynajetjerry]

Yep, Mark and Irvine.J.

.006 in. is the most often used spring steel for reed valves but that is suitable for pjs that are similar in size to the Dyna-Jet. For smaller engines, .004 might be best but for significantly larger designs, .008 and up would be preferable.

Aeromarine developed a 30-35 lb. thrust pj that utilized 5 modified D-J valve head assemblies and they, too, used the .006 valves. Obviously, reed valve design depends more on the type and size of the valve head than on the thrust that is delivered.

Jerry

[Irvine.J]

I've been really busy lately. Only thing is at 3am I was welding on the CC and stuffed it a bit. But there are only 5/6 tack welds so its easy fixed, its just a touch off center. Anyway, I'm happy with how its going so far...I've also rolled a single cone to slot nicely over the entire inlet diffuser and convergent piece. Make it all streamlined etc.

Another quality rolled tailpipe from the P42 (Mangyjet) Labs :D

Its sized for 5.5 lb or 2.5 KG. Wootya!

[Irvine.J]

Well, nearly there. I have a cone that will extend right around the part with the inlet bolts yet to go on. I don't have a Flowjector I believe its called, so i'll make a really nice spraying copper tube un-attached for now and will silver solder one in later. Unfortunately I'm having alot of drama coming up with spring steel, so I might just have a go using the shim steel 0.010 (I think) petals I've got atm, they only need last about 30 seconds.
Is this how its sorta/ kinda/ supposed to look???

Its designed to be 5.5 lb...
Are these bad boys generally harder to start then FWE styles?
What Air PSI are we generally talking?
Also, Should be sparkplug be right behind the CC bolt ring, about .5 to 1 inch no more?

Needs a touch of grinding so those bolts sit dead straight, 1 or two are resting on a weld, 2 minutes to fix.

[Mark]

What I like to do is get a small square piece of glass or find a like flat surface and figure 8 the valve plate on some 400 or so grit sandpaper for metal, I think silicon carbide. You want a really flat surface for your petals to slap against. You can get it mirror smooth, and the same goes for the petals, you want to get all the burrs off the edges of the petals, a valved pulsejet needs a certain kind of love. But they really are fun, king of thrust to weight in pulsejet land and probably noise too. Unlike the valveless "fluidic diode" pulsejet, the air gate/door closes faster, more like instant confinement, less sponge.
I just weight the head of my Dynajet and it came out 7.5 ounces and the duct with spark plug 8.5 ounces. Now if you did away with the plug and used an insertable ignitor like the Zanin pulsejet uses and lightened the hunk of aluminum in the head, replacing it with a thin cowling and lighter valve plate, you could get your thrust to weight ratio really up there. Earl Bailey said you could go even thinner than .020ths for the wall thickness too if you could weld it. I think he mentioned .016ths and maybe Jerry or someone might recall if some of the early/prototype Dynajets were as thin? I've some old literature that says the poor boys used a propane torch at the tail end if they didn't have a buzz coil for the spark plug.
On the other hand, you can sometimes get away with a really crude flap/reed valve, it just won't last as long and may or may not present more difficulty in starting. My first pulsejet used a 2.5 inch washer for the valve plate with sanded aluminum flashing for the single reed, a retainer kept it from flexing beyond the non-return springy point, (scientific nomenclature). It ran deafeningly for over a minute before the flex wore out. Believe it or not.
Mark

[Irvine.J]

Sweet mark, I'll get out a super soft polishing thing for metal and spend a good amount of time on it removing any sharp bits. I've heard they can be a real bugger to start, instead of using a sparkplug (though I have one ready) will a sparkler up the tailpipe or some lit turpentine do the trick?

Here is an idea for my gas injector, not sure if it will work though. I like the screws more then a nail as the angle is much better and much wider head on it.

[Mark]

One thing you will come up against is overheating of the reeds. If this happens they will warp. If you take a piece of reed and hold it in the flame of a propane torch you will see how fast it can warp. A wet liquid fuel - gasoline or methanol aspirated over the reeds is better than injecting directly into the combustion chamber. If you hold/cup your hand over the intake and prime your pulsejet and then spark it, you can really feel the suction on your hand when it revs up.
If one of your valves isn't seating properly, fire can skirt/sneak around it and after taking apart your pulsejet you will find/see where the flame has discolored the reed and valve plate.
I will, if the Nikon gods are willing, post a video of my 3 inch diameter pulsejet starting from a single spark of a piezo. It's kind of neat to hear it go from nothing to full grease in a gunshot.
Mark
http://tinyurl.com/2va4je

[Irvine.J]

Hehe that cool its like a bbq lighter or something. Anyway, I was going to inject the gas into the inlet, not into the CC, is that bad? With a bit of forced air from a blowgun. I'm looking to see if I have anything capable of supplying liquid fuels like the tip of a bike air pump modified with a larger D nozzle. (I have some metal tubes equal thickness, twice as thick and a few in between which could attach via screw thread to a saftey nozzle on an aircompressor, I'm go through my "Gas box" and take a photo shortly of what i'm thinking.

[Mark]

I dug up a few brassy pieces, some you can see are valve stems from car or truck tires with the neoprene buffed off and other parts from ordinary lamp fixtures. And then there are a few oddballs. What's neat though is that the tire thread off the Dynajet flow-jector is the same as any tire valve stem. It's a 5/16 32 thread, I even bought a tap thinking one day I might find a use for it. And at the other end of the flow-jector is another common thread I found on some brass screws. So brass would be easy to drill or make a prototype from, an air and fuel metering jet of some sort, ala homemade. Someone left part of a brass dart at the library and even that has some internal threading that you could use to thread onto something.
Pictured are a few tidbits and my store-boughts to show the starting air/fuel device. Just some ideas.
Mark

[Zippiot]

I made a cool injector nozzle by melting a penny (zinc) in a brass 1/8 flare, drilling a tiny hole through it then securing the pointy end of a nail inside the hole.

Makes a nice mist and can stand very high temps, well only about 600 F but thats pretty good!

[Irvine.J]

Wait a minute wait a minute...
the straight pipe is the fuel, the angled pipe is the air Right?

The holes just below the attachment for the forced air, looks to be the fuel spray points right?
Or does the fuel pass through the centre of that bolt/thread and enter directly into the CC?

What I have here is a DG-10 spray gun I believe for paint. With the gun removed, one can blow through area where the gun was attached and feel considerable suction on the tank pipe. I think this would be good to use if using liquid fuel as the tank, venturi, etc is already made. It has a really long copper pipe with needle point which at this stage I can't get off, and don't want to bend the copper pipe. The T junction is where the gun attaches to, and directly inline the copper pipe and protective pipe. The bottom of the T goes to the tank. If I was to remove the Gun, and just keep the T, and cut back the copper pipe so the nozzle was only 1/2 and inch or so from the T, might that work? Perhaps sealing off the back of the T valve where the airgun would normally enter.

[Irvine.J]

Heres my idea, no idea if its going to work though.