Straight Chinese Experimental, Will it work?

[Dang911]

Hi,

I do not have all the fancy metal working equipment to fabricate all these nice looking cones you guys produce for pulsejet's (jealous). All I have is basic tools, although I am a very good welder. I am wondering if I could pull off a Chinese style (like the smooth lady), in which the combustion chamber would be straight. Let me explain......

I would be using a Benzomatic propane tank for the combustion chamber. I would cut the stem (where the torch screws on) on the lathe, and tap it for a sparkplug.

Further more for the exhaust, I would be able to taper the 3" combustion chamber down to.....Would a 1.5" diameter mild steel tube work for the exhaust tube? Then flare it at the end. I could use a 1" mild steel tube, cut at 45's to make the intake, which would be welded onto the top of the combustion chamber.

Will all of this work, and make a decent WORKING first valveless engine? I am already in the process of building the Benzomatic valved engine in much the same fashion. (looks like a dyna-jet)

I have attached a drawing of the Valveless Benzomatic Project. If this design would work, would someone with experience, please fill in the "?". The only design constraint is the Benzomatic bottle chamber's diameter, which is 2 7/8" (7.3mm). Just repost the picture with the filled in dimensions.

Thanks

[leo]

Maybe this will do it, just wait on other more experienced people to comment.

[Eric]

Base your dimensions off the original chinese, except just use straight pipes. Also put the intake on the combustion chamber cone instead of the CC itself.

Eric

[Dang911]

Im not sure if I understand your placement of the intake, would you mind editing the drawing and showing me your take on the whole deal, including dimensions?

Also do you think it will work, and be startable?

Thanks

[leo]

Eric means like this (I think).
I say it will start, somebody else have a opinion?.

[larry cottrill]

I would slightly change two things: (1) Shorten the intake a bit to get the flare right near the L/3 point; and (2) Aim the bent part of the intake more toward the front face of the engine, instead of down into the bottom of the chamber.

But, it might start just like you have it shown, especially if you use a little Rosscojector as your fuel system. I've always thought the torch-size propane cylinders would make a nice chamber, except for being a bit longer than I would like. But, the proportions aren't that much different from the pressure can chamber of my Fo Mi Chin II, and that worked all right. The propane cylinder should be a lot better steel, too!

L Cottrill

[Dang911]

Thanks for everyone's useful input on this!!! I have made a revision trying to accommodate every ones suggestions. Please do note for people submitting future revisions that the Benzomatic bottle can be XXX in length!! The design doesn't have to use the whole bottle at its longest length, it can easily be cut to tailor for a BETTER design. With that being said is 150mm still a good length for the combustion chamber?

If everyone is happy with this design, I will go ahead in put it in CAD, and make some nice 3D renderings. THEN, I will start to build it (my propane cylinder still has another 10 min of gas left). As for fuel, someone mentioned a "Rosscojector" injector, what exactly is this? As for right now, I was going to just put a tube into the front of the intake, and supply it with Propane or Mapp gas.

[Al Belli]

Hi Dang 911,

The Bernzomatic company was formed by Otto Bernz, and he is probably turning over in his grave each time you write " benzomatic " !!!! :) :) :)

The center seam is high temperature brazed, and should be welded over for operating at pulsejet temperatures.

Al Belli

http://www.bernzomatic.com/bernzomatic/ ... utUs.jhtml

[Dang911]

Thanks that is a really helpful tip, I didn't know that!!!! As far as "Benzomatic" goes, at least I got it spelled right using his name....HEHE

So last call for any suggestions or objections to the Plan drawn above BEFORE I go ahead and draw it in CAD?

Thanks........

[steve]

but wouldn't drawing it in cad make it easier to make alterations to the design? you must not be using solidworks ;-)

[ed knesl]

[quote="Al Belli"]
The center seam is high temperature brazed, and should be welded over for operating at pulsejet temperatures.

Al Belli

I have used these cylinders for different purpose and found that brazing
at the bottom and the mid section was a problem, since the brass material
contaminated TIG welds and I abandoned the idea of using them much.
I do not believe that they will last more than couple of short runs.

If you are a good weldor just roll a rectangular sheet at least 20 ga
and you have combustion chamber. ( The top fitting is also brazed and
than you have to deal with a safety valve, too).

I do not recommend using Bernzomatic cylinders for any high temp
exposure.

Ed

[Al Belli]

Hi Ed,

I have used a 1/2" wide cap strip welded over the seam to eliminate weld contamination.

Al Belli

[Dang911]

I use Autodesk Inventor, Easier in my opinion then solidworks, plus more options!!! I don't like solidworks :(.

[Mark]

I've used the short fat propane canister to make a swell jam jar, but it has turned into solid rust, which isn't so attractive, but it still runs a fair amount of time, jam jar style with a large as possible hole bored down through where the torch would have screwed on. In this way it still retains the little nub of a neck it comes with.
It might work just as well or better if you sawed it off. It would be worth a try.
Mark

[Dang911]

After opening up the Propane can today, boy was I surprised. The brazing was very minimal, only one the center seam. That could easily be welded over with a strap (good idea). As far as the domed top where the sparkplug would go, the dome appears to be tig welded on NOT BRAZED and has added thickness. After they tiged the dome to the end of the pipe, they must of feathered it all together, because you can't tell, aside from welding pool marks. The wall of the pipe is 3/32" mild steel. Now here is the shocking part. Unless they did such a super job blending the pipe together, I think it is extruded pipe, not a sheet bent into a cylinder and welded at the seem. That is a big bonus in the long run, and will give added strength.