Fun designs

Mark · Post by **Mark** » Sun Nov 30, 2003 2:11 am

A thousand ideas, and so little faith. What does it take to experiment? What better way to know what you propose? The cost will hit you when your feet get wet, rude awakenings and yet the possibility of supreme fun.
Mark

Post by **Mike Everman** » Sun Nov 30, 2003 5:35 am

OK, OK, I get it! A lot more welding and a lot less talking! ;-D

Mark · Post by **Mark** » Sun Nov 30, 2003 2:57 pm

Mike Everman wrote:OK, OK, I get it! A lot more welding and a lot less talking! ;-D

I had a school of hard knocks yesterday is all. My little Logan knows how to run, I just have this little problem on how to feed it. I mean it's got no moving parts, no turbine blades or exotic twists or turns, not even a spark plug. The 10 second crude runs are fun to listen to, unlike a Dynajet perhaps, this thing can fluctuate up and down the scales somewhat, but if you starve it or if it gets too much fuel, it will choke it down and keep trying to run and it recovers, but my meager pressure head I am draining off the combustion chamber is spongy and erratic, so I tried shortening the silicon line that jumps when I start the engine and pressure goes to my little fuel tank, made with a glass jar and 2-holed rubber stopper.
I could buy a fuel pump and go tradition, but I was hoping to keep it simple, and somehow "simple" is as hard as making a ton of parts. Ah, but if it were easy, I wouldn't be doing anything challenging.
Mark

Mark · Post by **Mark** » Sun Nov 30, 2003 5:17 pm

Mark wrote:
Mike Everman wrote:OK, OK, I get it! A lot more welding and a lot less talking! ;-D

I might try using the heat from the engine to drive the fuel feed. I'm pretty good at making things explode accidentally, and what better way than to heat the gas tank. If so, I will start small and take care to control the pressure head.
I won't be happy till I get this Logan running red hot and furious. Speaking of hot, it was a "balmy" 36 degrees F in sunny Florida this morning and not too very warm in my garage yesterday either, compounding my suffering. I have to keep a fan in the window and side door open to breathe fresh air and to keep from pumping up the air compressor with methanol, propane, ether, or gasoline fumes, on various days.
Mark

Graham C. Williams · Post by **Graham C. Williams** » Mon Dec 01, 2003 12:50 am

Dear Mark.
In my 2stroke days we used a line from the tuned pipe to pressurise the tank. Better results came from making the line longer; it reduces the pressure fluctuations and gave a more steady feed. The idea was that if you cannot get the fluctuations in fuel flow to the motor in phase with the motor requirements, it’s better to go for a lesser flow but a steady one.
On the other hand Puttman et al. states that one of the situations that promote non-steady combustion is when the non-steady component of fuel supply is in phase with the motor. He goes on to develop this idea in terms of the non-steady component of heat release being in phase with the pressure fluctuations. You can see how this is related. In your case I’d see this as establishing the correct phase angles between: combustion heat release, combustion chamber pressure fluctuations and the fuel flow fluctuations.
Graham.

Graham.

Post by **Mike Everman** » Mon Dec 01, 2003 2:18 am

a very small orifice for the gas going into the fuel tank would smooth it out too.

Mark · Post by **Mark** » Mon Dec 01, 2003 3:23 am

Mike Everman wrote:a very small orifice for the gas going into the fuel tank would smooth it out too.

I'm using a 3 inch length of copper tubing at the last of the line. I micrometered the straight tubing and it is .060ths outside and probably a .020 or less pin hole size for the fuel to wisp out in a spray. I'm holding the tip of the tiny tubing just flush with the side intake port with a fly tying vise for tying flies.
At least I have mastered the art of 10 second Logan pulsejetting. I can do it almost every other attempt now. I turned out the lights and looked into the side port where a nice furnace of fire seen, although it sprays methanol out that port some distance too, over three feet in fact and I got some in my eyes! I tried to light this spray but I guess there was too much carbon dioxide or water vapor? I have taken to wearing my ear muffs now too. It's loud but almost twice as loud if I just prime it and let it rev and die off the prime only, my fueling is so crude but it's a start and still impressive for something that has only ~2 fluid ounces of air to work with, 2 shot glasses I guess you could say.
Mark

hinote · Post by **hinote** » Mon Dec 01, 2003 4:50 am

Mark wrote:
At least I have mastered the art of 10 second Logan pulsejetting. I can do it almost every other attempt now. I turned out the lights and looked into the side port where a nice furnace of fire seen, although it sprays methanol out that port some distance too, over three feet in fact and I got some in my eyes! I tried to light this spray but I guess there was too much carbon dioxide or water vapor? I have taken to wearing my ear muffs now too. It's loud but almost twice as loud if I just prime it and let it rev and die off the prime only, my fueling is so crude but it's a start and still impressive for something that has only ~2 fluid ounces of air to work with, 2 shot glasses I guess you could say.
Mark

Hey, Mark: Can you show what you've got--a photo? Or is this something you've done before.

I know all of us would like to see it.

Bill H.
Acoustic Propulsion Concepts

Mark · Post by **Mark** » Mon Dec 01, 2003 5:23 am

hinote wrote:
Mark wrote:
At least I have mastered the art of 10 second Logan pulsejetting. I can do it almost every other attempt now. I turned out the lights and looked into the side port where a nice furnace of fire seen, although it sprays methanol out that port some distance too, over three feet in fact and I got some in my eyes! I tried to light this spray but I guess there was too much carbon dioxide or water vapor? I have taken to wearing my ear muffs now too. It's loud but almost twice as loud if I just prime it and let it rev and die off the prime only, my fueling is so crude but it's a start and still impressive for something that has only ~2 fluid ounces of air to work with, 2 shot glasses I guess you could say.
Mark
Hey, Mark: Can you show what you've got--a photo? Or is this something you've done before.

I know all of us would like to see it.

Bill H.
Acoustic Propulsion Concepts

It's nothing really, but a quirky toy. I promise to photograph it running in a month or so. I swear I am going to buy a digital camera. A few minutes ago I ran it again adjusting the tubing right on the lip of the side port and it ran, but shot a steady fire out the side port about an inch and a half.
It's got to be the simplest jet I have made. I had only to drill a hole in the side of the 3/4" combustion chamber and tap it with a 1/8" pipe tap for the little length of 1/8 pipe to screw into. The tail is 1/4"plumbing pipe and it connects to the 3/4" CC with a bell, and a bell on the top now which necks down for a fat fuel line which is swung around to feed the side port. Everything screws together and is safely less than $15 to make.
I toyed around with longer combustion chambers and it really isn't affected adversely, it's not too fussy in that respect.
Mark
Mark

Post by **Mike Everman** » Mon Dec 01, 2003 5:34 am

My god, somebody send mark an old digital camera! Actually, e-mail me your address, I have an extra Logitech PC camera I'll send you in exchange for the pictures you'll take!
Oh, yeah, back in my RC days, actually before I got good at it, and crashed alot, and scraped off alot of needle valves, I started using a bent piece of brass tubing, like 1/8 od. You can bent it to complete closure, then open it up to pretty amazingly low feeds that stay consistent. Try that, it's really quick and meters well. and you can't beat the price!

Mark · Post by **Mark** » Wed Dec 03, 2003 6:04 am

Mike Everman wrote:My god, somebody send mark an old digital camera! Actually, e-mail me your address, I have an extra Logitech PC camera I'll send you in exchange for the pictures you'll take!
Oh, yeah, back in my RC days, actually before I got good at it, and crashed alot, and scraped off alot of needle valves, I started using a bent piece of brass tubing, like 1/8 od. You can bent it to complete closure, then open it up to pretty amazingly low feeds that stay consistent. Try that, it's really quick and meters well. and you can't beat the price!

I took 2 pictures of the little Logan today on the last of a roll of film. Don't think they will excite anyone, but if the still turns out when I get the roll developed, you can see how plain and simple the "design" is and a nice little beam of fire out the side port. The flame might be kind of faint with traces of color because it's alcohol, but none the less it is a peppy pulsejet rate of cycling, the Logan being 16.5 inches long.
I think you will think it funny to see how humble it is, yet it is every bit a squealing baby pulsejet. One thing about valveless pulsejets is that one big variable is controlled, that is the valves never need adjusting or tweaking. I know all I have to do is get the fuel to it, and let it cool down if I should want to start it again, (I light the tail to start it) and alcohol/air mixtures become too rich if the jet has been run.
I don't get excited about too many things, but I find this simplicity addicting. Yes, before work I had to go out in the garage and fire it up and several times after work too; and it will never wear out, because it's made with love and chubby fat plumbing pipe.
Mark