Pulsejet Build

[JustinY]

Ya that's what I figured I'd do. It should'nt take too much work to get them down to size.
Just out of curiosity, when you designed the engine was there a reason for the dual intakes?

[JustinY]

Another Question, I used that program to open the folder, now I can see the individual picture files. But they seem to be in a weird file type called CON. How do you open them? Every time I choose a program to open it with, it says that file type is not supported or something.
My generation is supposedly good with computers and such, but I'd rather spend my time workin, and talk to someone in person than waste my life on computers, cell phones and video games.

[metiz]

The dual intakes are for better fuel-air mixing.

the .con files can be opened with the file attached. Rename the file to .exe .exe files are not allowed on this forum, .rar is

[JustinY]

Oh, I got it. I didnt realize that cone deal was a program. Thanks alot!
Another thing, It looks as though the dimensions are different. I figure this is some sort of compensation for the metal thickness? If so, 20 guage sheet is .9525mm. Your plans specify 1mm thick metal, but .0475mm ought to be close enough right? What do ya think?
Also, all of the layouts seem to be there, other than the cone the intakes coonect to between the CC and the tailpipe. Am I just missing it?

Thanks, Justin Yochum

[metiz]

yeah 20 gauge will do. there are 2 cones not included in the .con files: the choke cone and the intake coupler. these parts are to complex for that program. These 2 cone layouts have been provided in the file "choke elbow m25.skp" wich should be in the rar you downloaded. You will need Google sketchup to open this file. check the link that Pyrojoe gave you to the M25 thread. the same post has an explanation on how to print the files from sketchup.

you might have realised that the endcap is not included. simply trace the open end of the cc on steel, cut out slightly larger (like ~1.5mm) so that after hammering the specified convex (i think it was 7mm) it fits nicely on the cc.

[JustinY]

Well I'm back, after working on the engine I am now done with all of the metal work with the exception of the endcap. So far Im happy with the way It's turned out. Now I gotta get propane and a spark to it.
So here's my question, what should I use for the fuel injectors and what is the easiest way to light one of these. I plan on using propane and I know the plans specified tubing with a ID of 4mm. What should I use for tubing? I thought about using brake lines from cars but they arent stainless. Does that matter? As far as the ignition goes, I was going to use a Model-T coil but I have only a couple of weeks to have this running. My graduation from High School depends on this project getting completed. I heard that sparklers stuck in the end can get it lit. Is that true?
Any help would be appretiated.
Thank You, Justin.

[JustinY]

Oh, one more thing, when building a stand for this thing how should I attach it to the stand? I've heard something along the lines of that you need to attach it at certain points on the engine as the resonance has something to do with it. Do I weld tabs to it or what?
Thank You, Justin

[metiz]

Hey Justin

You can use stainless, normal steel or copper for your fuel lines. Stick to the injector positions as mentioned in the plans and you should be good.
You can use sparklers for this engine, but I recomend using a sparkplug welded to the endcap and an automotive ignition coil for the spark. This engine is hard to start, if you use sparklers you'll be there a while.

I don't know what you plan to do with the engine, just running or thrust testing it? anyway, if you want to mount the engine in a frame, make sure it can expand lengthwise and in width. For example, make a small plateau that "cradles" the combustion chamber, and a piece of sheet steel in front of the combustion chamber to prevent it from shooting backwards. At the tail, make a ring around the exhaust pipe (don't weld or bolt!) and mound this ring to your frame. The engine should be secure now but still able to move around a bit for expansion.

Any pics of your build so far?

[JustinY]

Well, im done. Went out today and tried to start it. got some good bangs and every now and again it tried to run, but it needed plenty of air from the compressor. I think the biggest problem is probably the sparkler-down-the-exhaust method. The thing that gets me is the amount of air needed to get it going. It will make some pretty good continuous noise but it just doesnt seem loud enough to be true ignition. I can get loud bangs out of it, but they dont seem to be occuring fast enough.
Any suggestions?

[tufty]

Any suggestions?

First off, and just in case you haven't done this already, make sure there's *no regulator* on your gas tank, and no flow restrictor on your ballvalve.
Secondly, make yourself a rosscojector and use it to look for the right fuelling point. Searching the forum should get you information on how to do this.

[JustinY]

When we started there wasnt hardly any fuel comin out of the intakes, problem ended up being the fitting that goes onto the tank didnt hadly let any fuel through. After digging around we found one that was nothin but a hole. Now we got tons of fuel. No regulator, made sure of that when I got the hose made.
I have been moving the injectors around to find the right spot, they are as specified in the plans and i dont think mixing is the problem. Im sure all it is, is the sparkler firework ignition method. As soon as the gas ignites it burns the sparkler clear up and I gota make sure it doesnt go out. So in reality I only get a few seconds a try to get her going.

[metiz]

Try to find an electric stove igniter. You should be able to find them in any convenience store for like 5 bucks. weld in a sparkplug on the cc endcap (in such a way that the thread doesn't penetrate the cc, just the electrode, prefably) and hook your igniter up to that (some "modifications" required) it will probably work better than the sparklers. Can you make a pic of your engine?