Pulsejet construction

[itsme]

Hi there,

I've started building a small pulsejet (24mm diameter tailpipe) to see what happens and I'm busy with the tube. I have rolled all the necessary parts out of 0.5mm steel, but now have a small (I think...) problem. I've attempted to weld some of this material with an arc welder and it tends to just burn large holes everywhere. I used a 1.6mm rod with 55amps of current (the lowest the machine goes to).

My question is: How does everyone else do this?

If I were to use silver solder to hold it all together, would I end up with a pile of pieces after the engine has run and got up to full temperature? Would it melt the silver solder?

Thanks
Warren

[ZSartell]

Using an arc welder to weld such thin metal in my opinion is impossible. You really should try using a mig welder or a tig welder. Although even with these it is dificult to weld thin metal it is not impossible and with some practice it can even look good too.

[WebPilot]

Oxy-acetylene welding is an alternative. Use the smallest tip you can find and utilize low pressures. This was a former post of mine:



Later,

-fde

[itsme]

Hello everyone,

Thanks for the replies.

I have carried on and used silver solder to hold the tube together. Sadly I don't have oxy-acetylene, so this has been my only other choice. The silver solder that I have used has a 'working temperature' of about 915 degrees celcius (I'm not exactly sure what the manufacturers mean by 'working temperature', but I'm guessing it's the melting temp???). Does anybody know the approximate temperature that a pulsejet would run at on methanol? I've got a feeling that there's a 50/50 chance that it will hold together...

My other questions are to do with ignition. I have got an automotive coil and and 12V 7.0Ah battery. I can get reasonable sparks by simply breaking the circuit by pulling the wires apart (very crude, but it works...). I was thinking about using an electric motor to operate some simple points to do this job for me. Any thoughts on this? Where should I position the spark plug in the combustion chamber?

Thanks and sorry for all the questions.
Warren

[Al Belli]

Hi,

Go to an auto junkyard and get a 4 or 6 cylinder distributer ( points type )and a heater blower motor. Drive the distributer with the motor, and You will have an excellent ignition system. The distributer is the switching device, and don't forget to use a condensor on the points.

Al Belli

[Hank]

Hello- Al, I toured the numerous auto salvage yards in my section of Florida lately and was not able to find a points distributor for a water cooled VW. (They had em until the early 80's. My need to use carbs on a Jetta.) The blower motor you mentioned may be used to drive some other switch, a points distributor seems to have followed the path of the dinosaur. Good luck, Warren. Hank

[Al Belli]

Hi Hank,

The UK probably has thousands of rusting BMC- A engine powered wrecks that have a nice point type distributor. The venerable aircooled VW also has a nice distributor for this purpose.

Al Belli

[WebPilot]

[Tom]

Is that your way of being Milisavljecic, Forrest? As soon as the forum's not convenient for you, you can delete all your posts off your server?

Did I miss something?

[WebPilot]

Here is a picture of the original.

Later,

-fde

[Mark]

I have a new remake of the Model T coil in wood, but also another one the same size in black plastic. The unit at the bottom of the screen is a 100,000 volt device I bought on eBay. The red and black tiny high voltage device is 10,000 volts and runs on anything up to 15 volts dc. I like to use a small 9 volt battery with it. The 100,000 volt device needs wall current so it isn't as portable. I threw in a piezo gas grill sparker for fun. I have three other different kinds of ignition devices too, I feel I have beaten a dead horse now. A static electricity device might be neat.
http://home.earthlink.net/~lenyr/stat-gen.htm
Mark

[Mark]

Off-topic but found on the static electricity page and link, a weird wire sound, just the thing for an intro to a pulsejet short footage MPG. Behold, another strange form of resonance.
Mark
http://home.earthlink.net/~lenyr/wiremus.htm
http://home.earthlink.net/~lenyr/wirex3.wav

[Mark]

Mike, a neat thing for a pulsejet movie would be to have a parrot learn and do some mimicry of a jam jar or snorkeler or pulsejet from afar so as not to damage his hearing. Parrots can do cell phones and chainsaws, I figure that would be funny to have one doing a jam jar, the initial hiss and then the fluttering sound. Would be a great intro for a movie, just a bird in his cage, an omnition of coming events.
Mark

[WebPilot]

Ah, a piezo, that brings back memories of an old post I did back in 2002

AAA Battery Powered Igniter, Pix and proof of concept. 2002-02-14 21:19:34

http://www.pulse-jets.com/oldforum/se.p ... m=pulsejet

Here is most of that post:





Here again, are the associated pics:


This is the grill ignitor I bought at Lowe's.

http://www.brads.net/forrestde/ForumPosts/Apparatus.png
These are the parts I found in the package.

http://www.brads.net/forrestde/ForumPos ... arking.png
This is a pic of the spark (I smell ozone again).


It can fire a spark plug.

Later,

-fde

[Mark]

I've got two of those kind too. Oddly one tics at a faster rate than the other. Sometimes though you will find you need a hotter spark or would benefit from such. Sometimes on my single pop starting method I use, that's where I spray some methanol into the tail end and then spark the spark plug, I'll be clicking the piezo time after time and then the jet will finally pop, because the spark is weak or the mixture not perfect. With the tiny battery powered units that are not piezo but starting to show up more and more on gas grills, they also can't put out much heat. A wet plug and you are in trouble.
I wouldn't go to the trouble to use my Model T buzz coil if I didn't have too and sometimes I don't. Gluhareff used a simple piezo crystal sparker because he could get away with it, but he was using propane. I think my piezo will jump a greater distance than the single tiny AAA battery powered gas grill sparker.
Mark