Jims Little 3 Lb Thermojet

[Eric]

You would have to custom make a carburator line which wouldnt be hard, you couldnt reuse that one you have. If it is for remote control I would go with a fuel pump though, as you wont have the engine go rich or lean from manuvers.


Oh your also looking at 321 grade stainless. You dont need 321, you dont even really need stainless although it is nice. Brass works and wont melt with propane, so 304 will work, and for 1/4 its $11 for 3 feet which is slightly better.

Eric

[Eric]

I have some 5" steel tubing, unfortunately i think its just barely 4' long. I think I am going to make a scrap engine using a 20 pound junk propane tank as the combustion chamber, maybe get some aluminized exhaust tubes for the intakes.....

Should be loud, and definately will be fun.

Eric

[Jim Berquist]

I have been working the aerosol can version of the ram jet. Will post some pic's asap. I want to try them with the P.J. first.

My shop Vac died yesterday! Need a new one.

Everything is made from a can!

I have a camera, I need a video with sound!!!

Jim

[mag]

So, guys, another picture of the completed engine but unforunately my neighbours did a christmas party today so i couldn´t fire it up. Damn!

So I have to wait some more days and try it out next week.



But, heres a picture of the big mama *lol* :D

[Eric]

Nice, that should finish off the old plastic stool.

If you point it straight up in the air most of the sound will go into the sky. If its not cloudy out the sound will just go up and away, but with clouds you might get some interesting things like reflections or precipitation.

Eric

[mag]

yepp, the stool is finished after this for sure! *lol*

The problem is, where I live, its not easy to do something THAT loud. And doing it outside would mostly end in a visit from the police... So im doing it inside in the car shop where I work. The only problem there is, the neighbours, I have to wait until they leave else they will complain about the noise (which I actually can understand lol). So I have to wait, but its hard knowing theres an engine which just wants to run...

[thecheat]

hey, I think the stool will be dead... sad to see it go... Lol, oh well, it was for a good cause! (however stainless works great as a heat shield!)

Eric- where ARE you getting your tubing? The prices you were listing were what I'd expect. 12 a foot is pretty expensive!

Oh, and I'm in quite a predicament... my engine only seems to give off 1.5lbs of thrust... which is kinda disappointing. My problem is that I don't know why! the test stand I rigged up, despite the minor issues, turns very freely, and smoothly.



Also, what might this be good for? (type of PJ?)

[Eric]

Did you flare the intakes yet? Maybe play around with the injector location and pinch them down flat so you get much higher velocity fuel injection.

Eric

[Al Belli]

Hi cheat,

1/8" x .020" wall tube type 304 ss is P/N 8989K12 under $10 / 6feet.

Al Belli

[thecheat]

al belli, thank you, I couldn't find the 304 stainless for the life of me, all I would get was the more expensive ones. I'll go check that out.

Eric: No, I haven't flared the intakes (how much of a difference DOES it make? I'm guessing alot...) And the rosscoinjectors are about as pinched as I can make them. I'll go flare the intakes though.

[Jim Berquist]

The Cheat:

Follow the link:

Search : 304 stainless steal tube...............Comes up as page nine..

You have to enter the temp rang....ID....OD.....And it will find it.

Follow the promps and

give it What you want and it will find it for you.

Price is dependent on amount and type $5.00 to $10.

seamless and malleable. I tryed to give you a link right to the page but it did not work!!!

http://www.mcmaster.com/


Jim

[Eric]

The flare is in the top 2 of the most important parts of the engine to get high performance, probably number one with engines that are already pretty developed.

Eric

[thecheat]

ok, thanks for that, I really didn't know the flare was that important! Now, why IS it that it's so important?


PS: thanks for all the help, I enjoy this forum quite a bit... people don't mind helping you learn.

[Jim Berquist]

My shop vac died the last week.....

I was sitting on the couch dieing with a way to fire the beast up!!

Then I remembered that we had a AIR bed and a Pump....

It worked.

You can get these at Wally World for about $12.00.....


Jim

[Dave_G]

My shop vac died the last week.....
I was sitting on the couch dieing with a way to fire the beast up!!...Jim

The original Thermojets would start without any air injection at all. You just light one of the two injectors and slowly turn up the propane. Those injectors were different -- they did not extend inside the plane of the inlet flares, and they used a small orifice rather than the Rosscojector concept. I have an original Melenric J5 and a cheap, leaky, spotwelded, "ebay clone", but they'll both start w/o air. Just a thought, but you might give it a try...just pull your injector back so it's just outside of the inlet plane. Also, this method may require flared inlets?

Oh, and I'm in quite a predicament... my engine only seems to give off 1.5lbs of thrust... which is kinda disappointing. My problem is that I don't know why! the test stand I rigged up, despite the minor issues, turns very freely, and smoothly.

According to the original Thermojet manual, and what I was told by Bryan Seegers of M-Dot aerospace, the thermojets didn't start to produce real power until fed liquid fuel. That is, you were supposed to start it on propane vapor, then after it got hot, transition to liquid. I cannot confirm how much of a difference this makes however, because I never wanted to run mine that hard -- it's more of a collector's item for me. And the spot-welded 'J3 clone' is too leaky to give any kind of decent performance so it wasn't worth bothering with. I ran it a couple of times and put it away. Anyway, you might give the liquid propane a try (after the engine is very hot) if you want to improve the thrust.