No-weld pipe fitting valveless

[hinote]

I didn't add it up. the reducers were from early jamjar experiments. I'll go to home despot and price it out one day soon.
The expander tail didn't sustain, and made ginormous, hugantic cannon bangs. I think the 1.5" pipe part at the end is too long. I'll shorten it tomorrow and try again.

Hey Mike:

Don't forget--you need to maintain the ACOUSTIC length of the tailpipe.

Take the physical length and add .3D to get the acoustic length.

If you make a larger tailpipe, you'll need to shorten the physical length-to maintain the original acoustic length.

I'm sure you (of all people) know this. I'm just pointing it out to the folks in the cheap seats.

Bill H.
Acoustic Propulsion Concepts


".......some day soon we'll be flying airplanes powered by pulsejets."

[Mike Everman]

DOH! Of course, though I still think the big section is still too long. I'll try removing the difference first. Going from 1" to 1.5" means I need to cut off only .15", but I'll give it a try, and then another, then another... ;-)
Wait'll you see the turbo bicycle at the meet!

[Mark]

Mike, do you think you are getting some benefit by using a long injection tube preheated by the snorkel over the attempted direct injection via the bell technique?
Mark

Nope, pretty sure not. The copper fuel stinger is totally cool to the touch when I shut down and remove it.

Well, ~5 inches of copper tubing in a direct flame ought to raise the temperature to some degree over the hole in the side of the bell technique. Copper conducts heat almost as good as silver, which is the best conductor of heat. If the propane wasn't absorbing heat, the copper tubing would be hot.
Mark

[Mark]

I was thinking it would be fun to make some odd little devices, and not something practical other than as kinetic art. Say you took your Schubert and added a Logan side port to it. Then you could have fire out three ports, extrapolating, you could add another port out the other side of the combustion chamber making a 4 port cross shaped pulsejet, a religious experience perhaps. Might be marketable to some fringe elements or excentric art collector. Ha
There is a twin port sphere in Reynst's book, how interesting if you could get a 4 or 6 port sphere to run, imagine a ball with pipes sticking out like some floating mine of WWII.
Getting something like that to run would really show some talent I think.
Mark

[Mark]

Mike, I guess you could contort your Pipewood to run with the ports 90 degrees from each other or twist it more and have it go another twist and have the ports pointing 180 front to back with a zigzag in the middle. Just something to do if you want to have a strange design for some photo op.
People would scratch their heads and wonder what the artist was thinking.
Mark

[pezman]

Based on the plans for a propane burner that I posted in the "Tools" section, I modified my 2" CC pipewood last night with a huge venturi on the front and drove it with a 0.06" nozzle (used a Mig wire feed for the nozzle). I managed to come up with a starting technique that starts the engine every time on the first try.

- Crack the valve on the propane just a litte bit so that the propane coming out is lower that the flame speed. You can light the propane and a stable flame will appear at the tip (use a lighter, another torch, a flint or whatever to light the flame).

- Point the tip into the nozzle.

- Slowly crank up the propane. As the flow exceeds the flame-speed, the flame will migrate down the intake tube and also start pustating a bit.

- Once the propane is going pretty well, hunt for sweet spots and tweak the propane flow upward when you find one.

Using this technique, I managed to get the jet into a weird "sub-harmonic" mode, where the pulses were less frequent but more powerful. Unfortunately, this was not a stable mode of operation and the pulses caused flameouts pretty quickly.

[Mike Everman]

Ah, Pez, sounds interesting! Picture or sketch?

[pezman]

I'll try to post a little movie, but I'm leaving on vacation Sunday A.M. and may not be able to do a movie before next week.

My only frustration with the pipewood is that it drinks fuel faster than a 1# cannister can supply it. The fixtures on the propane feed freeze up, things start leaking etc. I'll have to hook up the BBQ tank if I really want this to wail properly.

I tried to put together the 1"-er last night, but was unable to find some of the parts.

[Mike Everman]

Welllll, I did get my parts from a plumbing supply down the street. never got around to looking at home despot. I'm pretty surprised they didn't have this stuff. it's pretty standard plumbing fare.

[Rossco]

i looked in a hardware ages ago here for this sort of pipe and fittig stuff for the same purpose.
I found very little of use, and very expensive for what it is. It is much cheaper for me to cut, roll or just use scrap exhast!

Rossco

[mk]

Especially 2" to x" bell transitions and different other ones are very rare here, too. Only 2" to 1", 1.5" to 0.75", 1" to 0.5" and 1" to 0.75" can be found here and there.

[av8r]

Think I might have a go at one of these. Cool design. Its so simple. How much thrust should I expect to get from the ugly stick.

[Viv]

[quote="hinote"][quote="Mike Everman"]I didn't add it up. the reducers were from early jamjar experiments. I'll go to home despot and price it out one day soon.
The expander tail didn't sustain, and made ginormous, hugantic cannon bangs. I think the 1.5" pipe part at the end is too long. I'll shorten it tomorrow and try again.[/quote]

Hey Mike:

Don't forget--you need to maintain the ACOUSTIC length of the tailpipe.

Take the physical length and add .3D to get the acoustic length.

If you make a larger tailpipe, you'll need to shorten the physical length-to maintain the original acoustic length.

I'm sure you (of all people) know this. I'm just pointing it out to the folks in the cheap seats.

Bill H.
Acoustic Propulsion Concepts


".......some day soon we'll be flying airplanes powered by pulsejets."[/quote]

But one should of course remember that this figure is frequency dependant so for best results lower values should be used for higher frequencys and larger values for very low frequencys.

Viv from the back of the cheap seats:-)

[Mike Everman]

Wow resurrecting a thread from the archives! what's the actual proportion to frequency for the acoustic correction, Viv?

[Viv]

[quote="Mike Everman"]Wow resurrecting a thread from the archives! what's the actual proportion to frequency for the acoustic correction, Viv?[/quote]

From my books on manifold design it varies from .1 at high frequencys (6Khz) to .8 at the low frequencys (10Hz).

The actuel values are calculated using a confusing amount of conditions and varibles depending on the type of acoustic circuit under consideration.

My main point was that the correction factor used should suit the application and .3D was just an arbitory figure.

Viv