American West Coast Pulsejet Meet, April 30

[hagent]

Here is one of Bill's? Lockwoods at the PJ meet 2005.

I guess the magic number is 2 megs!

[hagent]

One more from the PJ Meet 2005.

Have a little bit of trouble starting a Chinese PJ?

I would have put money on the gentlemen in the dark blue loose shirt catching on fire at some point :)

[Mike Everman]

Thanks Hagen! I am glad you could make it out!

[Mike Everman]

Welcome to the forum, Chris!
I am in awe of the footage, man. I can't wait to see the chopped down version, and also look forward to the sound on the tape version. Your showing up when you did was a breath of fresh air.
I'll call you this week for a night run, OK?

[Mike Everman]

Larry, just so you know, this was all a complicated ruse to get your Dynajet. I consider it a huge success, sucka! Bwahahhahah!
No, really, I'm getting dug out here and should ship everyone's stuff early next week. For now, I head on a biz trip. cheerio!

[Bruno Ogorelec]

Oh, yes, the Dynajet was universally admired and fondled. It is a beautifully made engine. We all wished we had some reeds, but making them in the vineyard was a mite ambitious and no one relished going to a workshop somewhere to access technology that made more sense. So, it ended up as an inert object of desire.

As it ever does in pulsejet circles, it was often mentioned when comparisons were made. One of the most exciting moments of the meet -- in my eyes at least -- was the discovery that Mikhail's 'Laird plans' Chinese made the same thrust that Dynajet was rated at.

That one sure blew up the notion that valveless engines are inferior in terms of thrust! Both engines are roughly the same dimensions and the Chinese can probably be built lighter as it does not have that lump of the valve head up front. Very exciting!

I think many of us are thinking 'Chinese' these days. The meet sure thrust that engine to the forefront. Alas, it seems to be one of the few pulsejets not quite comfortable with the 'Rosscojector'. It just does not care for starting without forced air.

[Mark]

Do you have picture of the valveless pulsejet and it's length? The Dynajet makes about 4.5 pounds of thrust, is that what the Laird valveless produces?
Mark

[Bruno Ogorelec]

Do you have picture of the valveless pulsejet and it's length? The Dynajet makes about 4.5 pounds of thrust, is that what the Laird valveless produces?
Mark

Well, Mikhail (Nanosoft) can give you the measurements, but he says he has copied Laird's plans exactly. And yes, if I remember it right, we measured 4.5 or 4.6 pounds. I think I have a picture in my camera, but there must be dozens of others. Some may even show the instrument face with the figures showing. We were all totally amazed.

Ed Knessl's somewhat scaled up iteration of the Chinese recorded 5.6 lbs.

[Mark]

I wonder if someone could measure the volume of the Laird Chinese to compare it to the volume of a Dynajet, say cork the side port and fill it with water.
Mark

[larry cottrill]

As it ever does in pulsejet circles, it was often mentioned when comparisons were made. One of the most exciting moments of the meet -- in my eyes at least -- was the discovery that Mikhail's 'Laird plans' Chinese made the same thrust that Dynajet was rated at.

That one sure blew up the notion that valveless engines are inferior in terms of thrust! Both engines are roughly the same dimensions and the Chinese can probably be built lighter as it does not have that lump of the valve head up front. Very exciting!

I cringe whenever this comes up. "Roughly the same dimensions"? Only late at night after a few Croatian beers. The Dynajet is 21 inches long, a maximum of 2.5 inches OD and less than 1.5 inch OD at the tail flare. It sucks gasolene by itself for three minutes out of a converted Campbell's Soup can. Every one of those details is important.

When I hear someone say that the Chinese can compete with the Dynajet, I know one thing about that person: He's never had to put either of these engines in anything and tried to fly it. He's certainly never tried to squeeze the engine inside the carved fuselage of a scale model and had it survive to get launched and into the air. What good does it do to have an engine with Dynajet thrust if you have to build a scale model 60 or 70 percent larger to get it to fit? Or to distort the scale of the fuselage to get it to fit? If you mount the engine outside, as on a record speed plane, what do you do with the extra drag of the pipe? What will you do when someone racing against you claims that you get some of your thrust out of the intake, therefore violating the 1 square inch rule?

This is not to take anything away from the design, or anyone's particular build. If I had been there, I probably would have been astounded, too - especially at the scaled-up version. I'm simply pointing out, as I have before, that "to compete" means a lot more than getting the static thrust value you want. It means having an equally compact and practical flight propulsion system capable of starting easily and running economically, and capable of being flown in an airframe of reasonable size, drag and weight. Nothing short of that will do!

L Cottrill

[resosys]

This only matters to those looking to fly R/C aircraft with pulsejets... Some of us don't want that and never will. So, comparing the two engines purely on static thrust is valid for many folks.

IIRC, Ed's Chinese was only scaled in diameter and not length. Nano, Ed, is this correct? This is an engine I want to build and experiment with for thrust and engine design testing. There is some magic in there, somewhere.




Chris

[Bruno Ogorelec]

All valid points, Larry. I am not going to dispute any of them. You are right.

However, I am looking at the thing from a completely different perspective, in which its performance is important and your points are marginal. Namely, I want to fly myself.

In big sizes, the rules of the game are different. An important point in that context is that the engine is valveless.

It can certainly be converted to liquid fuel injection (Bill Hinote has done it with a Lockwood). Indeed, it can probably be expected to develop greater power that way, as gasoline is more calorific than propane (more heat from the same volume of liquid).

My excitement stems from the confirmation of the dictum (issued by Reynst and reiterated by Milisavljevic, if I'm not mistaken) that the valveless designs offer hope for greater performance (in terms of thrust and TSFC) than the valved types. For a long time, practice seemed to argue against that.

For model flying, however, Dynajet is almost impossible to beat.

[Bruno Ogorelec]

IIRC, Ed's Chinese was only scaled in diameter and not length. Nano, Ed, is this correct? This is an engine I want to build and experiment with for thrust and engine design testing. There is some magic in there, somewhere.

Chris, as Mike has pointed out, the scaling was apparently not quite faithful and the intake appears to be a bit smaller than it should (or could) be. That is probably why Ed's iteration develops less thrust per internal volume than Mikhail's 'Laird plans' machine does. Even so, 5.6 pounds from such a small thing was quite impressive.

[resosys]

Bruno,

Ahh yes. It's all coming back now. Certainly is impressive, either way. I'm looking forward to understanding a bit more about uflow so I can model the Laird specs and work out a larger engine.

Those dual intake chinese cruise missle engines are beautiful, imho.


Chris

[Bruno Ogorelec]

Bruno,

Ahh yes. It's all coming back now. Certainly is impressive, either way. I'm looking forward to understanding a bit more about uflow so I can model the Laird specs and work out a larger engine.

Those dual intake chinese cruise missle engines are beautiful, imho.

Chris,

I have a sneaking suspicion that those guys had a good thing going with a smaller single intake thing and didn't want to spoil it. So, they went double on the chamber and tailpipe sections but used two original intakes instead of risking a single bigger one of unknown properties.

I mean, what else would explain having two intakes?

The only other reason that comes to mind is making the intake length shorter, but why would they want to do that? The design could well take a much longer intake pipe with no visible harm. It must have been something else and scaling up occurs to me as the only sensible answer.

See also that the intakes are close to each other. To me, this spells the wish to preserve the original flow pattern, too.

That way of scaling up a valveless engine sounds eminently sensible to me.