Re: Big pop-pop engine
> If too much air ever does become a problem, I think the answer is to "tune"
> the pipe length so that when the action is well established, a little steam
> escapes at each pulse. That allows the excess air to escape.
I didn't try to tune the engine, but I tested several engines having different pipe lenthes and diameters. Every time an engine reached its nominal power some bubbles escaped. From that time the power (effective flow and mean thrust) was nearly constant and bubbles were escaping more or less periodically.
> This might explain why very long horizontal pipes don't seem to work - but
> then they have the complication of more mass of water.
Yes. I saw some months ago a Birman pop-pop boat which was amazing for non specialists. I took a picture of it. It has an inverted diaphragm engine. The candle heats the diaphragm. This allows to have the pipes (there are 3 pipes) on the top and, after a bend they are straight down to the stern transom. I year ago I would have said it is a special design just to change from usual one, but today I'm convinced that it is a good design.
> A separate topic that I find interesting is the single-piston (so-called
> displacer-less) "hot air" engine. Despite its many differences from
> pop-pop, it shares the feature of a mass bouncing on a cushion of gas,
> causing the gas to alternate between hot and cold.
I know several pop-pop enthousiasts who are also interested by Sterling engines and derivates. I don't know enough about hot air engines to compare with pop-pop ones.
- Hi dan,
I'm presently travelling far from my pop-pop engines. The pipe of the big engine is approx 75cm long. It is going up for the first 10cm and then it is straight and slightluy inclined down. More details in a couple of weeks when I am back to my "laboratory".
> Message du 19/03/07 00:15
> De : "danoyes1" <danoyes1@...>
> A : email@example.com
> Copie à :
> Objet : [pop-pop-steamboats] Re: Big pop-pop engine
> Hi all
> Jean I look foreward to hearing the test results you get for your
> big drum evaporator. how long is the pulse pipe on your new engine?
> it's good to hear that it had such a powerfull thrust pulse and ran
> without incident.
> --- In firstname.lastname@example.org, "Slater Harrison"
> <Sharrison@...> wrote:
> > I was just looking at Dan's and Jean-Yves' pictures. Wow! I've been
> > following pop pop engines for a couple of decades and I knew of two
> > types: the diaphragm type and the coil type. I've never seen
> > like the hammer head! Where did this design come from? How long
> has it
> > been around?
> > Slater
> > -----Original Message-----
> > From: email@example.com
> > [mailto:firstname.lastname@example.org] On Behalf Of Jean-Yves
> > Renaud
> > Sent: Thursday, March 15, 2007 1:58 PM
> > To: email@example.com
> > Subject: [pop-pop-steamboats] Re: Big pop-pop engine
> > Hi all,
> > Up to now, my biggest pop-pop engine had a pipe of ID 10mm, and
> > engine was far from optimized because at that time I didn't know
> as much
> > as I know today. Encouraged by Dan's messages and by the pictures
> of his
> > engines, I built a big one. I wanted to call it the 4 dollar engine
> > because 2 coins of 2 Canadian $ would have been perfect to close
> > evaporator. Unfortunately (that's the appropriate word) I had only
> > coin left over from my last visit in Canada. I tried the Italian
> > coin. It fitted too...but I had only one. Therefore, as I didn't
> want to
> > be responsible of a war between Canada and Italy (with all the
> > corresponding messages on the forum!!!), I decided to build 2
> > caps by myself. (see the photo album).
> > Two hours later the engine ran at the first attempt. The
> evaporator ID
> > is 28mm and the pipe ID is 12mm. The engine seems very powerful.
> > water level in my (small) test tank (approx 15cm x 30cm) was 30mm
> > the top, but the waves succeeded to flood my work bench.
> > When I have time (i.e. probably not before next month) I will test
> > engine with appropriate measuring instruments and I'll let you
> > Jean-Yves