Kazoo engine

Post by **Mike Everman** » Sat Dec 13, 2003 5:23 pm

Thanks to Tundra Man for the name!

This is a smash-tube Lockwood deriviative, now with proper proportions I can make iterations in short order in a press with clamshell rings to keep the CC in close to cylindrical shape, and what's not shown is some welding rod spokes down the centerlines of intake and exhaust to stiffen the flat areas. Thicker walled than normal will be used for this quickie. I can alter it easily, and even put screws at strategic points that close or open critical areas like the throat, exit and each end of the intake. It is important for me to know if conversions to roughly rectangular sections have any correction factors I should know about, beyond just area conversions.

This is not intended to be a winner at power/weight, since the material is necessarily thick, it's a precursor to rectangular cross-sections that I'm attempting to envision that resolve and or use the forces exerted on the flat sections. The flat sections could be made stiffer by making them semi-circular (semi-annular).

I've shown it with crossing intake and exhaust throats, attempting to make for good mixing, much as in a Kentfield (non colliding streams).

My goal is to make this over the holiday, everything is in place but a spare minute!

Bruno Ogorelec · Post by **Bruno Ogorelec** » Sun Dec 14, 2003 7:38 pm

Mike,

Of course, I love this. I love things simplified to the extreme. That's the whole point of the pulsejets -- to have mechanical complexity replaced by cunning tricks. Go for it.

As for conversion factors, you'll find out. I don't think anyone can tell you anything useful about it.

Viv · Post by **Viv** » Sun Dec 14, 2003 8:28 pm

Now I just have to admire that.

Nice

Viv

Graham C. Williams · Post by **Graham C. Williams** » Sun Dec 14, 2003 9:55 pm

Dear Mike.
Very nice.
You could try leaving it circular at the extreme exhaust end. So it's flat near the CC end and gradually opening up as you go along.
I'll try modelling this in 1D; I cannot see why it shouldn't work with fuel injection at the front cone.
Graham

Post by **Mike Everman** » Sun Dec 14, 2003 10:55 pm

Thanks Viv and Bruno, I'll post my progress here with pictures. Steel collars and material show up Monday, and I will be a-smashing soon!
Graham:
I've checked the numbers at your urging, and this is how far you must smash at the exit a tube that starts with the net CC diameter (exit=.82 CC dia, or 53% of the CC area). I can post the smash tube spreadsheet if you like, but simply put, it assumes that when smashed, the perimeter reamains the same, the flats are straight, and the radius' are perfectly semi-circular.
It's unlikely that the latter two assumptions will be true, so I may be filling the tube with lead before smashing, and melt it out after. (I had planned this for later in order to curve the intake 180 after I achieve a running configuration).

Graham C. Williams · Post by **Graham C. Williams** » Mon Dec 15, 2003 1:50 am

Dear Mike.
Do you think it would be safe to increase the friction component above that normal for a circular cross section? Perhaps do this in the crushed parts only?
I'm also thinking that the heat transfer into the walls in these parts will also be higher.
Perhaps the ratio of combustion chamber dia. to operating frequency (or overall length) will also need changing thus reducing the mean combustion time and the ratio of damping to excitation of the wave structure.

Your thoughts.
Graham.

cudabean · Post by **cudabean** » Mon Dec 15, 2003 5:09 am

It would be a complication to put lead in, not to mention the toxicity issues of dealing with that metal. What about other solutions such as packing sand in, and squeezing a little, shift the sand, squeeze some more, etc.

This might work as well when bending it into a U.

Also, as far as the squashed cross-section presenting more friction for the exhaust gasses, I can see that. I would guess that this extra friction might play some havoc with your initial measurement estimates.

Pretty simple though. Jam jar simple.

cudabean

Post by **Mike Everman** » Mon Dec 15, 2003 5:28 am

Graham,
I'm not sure if changing the surface to volume ratio from standard is actually bad. (Seriously, I really don't know!)
If I had to cast about for possible advantages, other than the obvious of construction, my thinking is thus:
1. I think it's interesting that the surface to volume ratio is in fact constant from end to end, which I find a possible reduction in variables normally difficult to iterate experimentally. When I iterate the basic dimensions, at least S/V will not be changing too.
2. Increased surface drag is going to manifest itself as damping as you say, and won't change the fundamental frequencies, so I do not expect length changes due to this. It will have an effect on amplitudes, with unpredictable result.
3. I am hoping that the non-circular intake and exhaust throat, will act like an "acoustic polarizer" if you will. Only the higher frequencies will go through the throat in the narrow direction, lower frequncies allowed through the width. I don't know if this is good or not, but certainly different! ;-)

Post by **Mike Everman** » Mon Dec 15, 2003 5:38 am

Cudabean,
yeah, I was planning on trying sand first, but I'm not sure it'll work. I don't have to use lead... maybe bismuth. It'll all come out eventually!

Bruno Ogorelec · Post by **Bruno Ogorelec** » Mon Dec 15, 2003 7:44 am

Graham C. Williams wrote:Perhaps the ratio of combustion chamber dia. to operating frequency (or overall length) will also need changing thus reducing the mean combustion time and the ratio of damping to excitation of the wave structure.

Hmmmmm....

Mike Everman wrote:the non-circular intake and exhaust throat, will act like an "acoustic polarizer" if you will

Harrumph....

Are you people aware of the way you sound? OK, let me tell you. You sound as if you know what you are talking about. Can you say those things looking in the mirror, with full conviction?

I wish I could do that. If I did, I could finally embark on that book on pulsejets I have always wanted to write.

Post by **Mike Everman** » Mon Dec 15, 2003 8:28 am

Bruno,
Please refer to my sign off saying, buddy! Conviction (sometimes foolish) is what makes you put hand to metal. If I didn't have "this time for sure!!", I wouldn't have nearly as impressive a pile of shattered dreams! ;0)

bruno wrote: I wish I could do that. If I did, I could finally embark on that book on pulsejets I have always wanted to write.

What a coincidence, smoking WEED makes me feel like I'm going to write a book, but I'll leave the PJ book to you.

Graham C. Williams · Post by **Graham C. Williams** » Mon Dec 15, 2003 11:13 am

Dear Mike.
Some numbers needed.
What will be the intended dia. of the combustion chamber? Please don't make this too small, 80 - 100mm would be good. Giving a total combustion time of 2 to 3.10^-3ms.

How the mean mixing path length is affected by the flat intake, I don't know. I can only imagine that as sharp a discontinuity as possible between the induction pipe and the combustion chamber will help.

The basic 'single intake' Kentfield-Lockwood motor seems to work well with changes to friction and heat transfer. A safe bet would be to keep to the basic dimensions of this motor.

The intake. Of all things the flat open end may cause the motor not to run. Can you at least make a large lip or open this up to circular again?

Graham

Stephen H · Post by **Stephen H** » Mon Dec 15, 2003 11:59 am

thats a lovely engine there, and all though i dont understand most of what people are saying it sounds good!
well done

Stephen

Bruno Ogorelec · Post by **Bruno Ogorelec** » Mon Dec 15, 2003 12:01 pm

From what I could glean from experiences of many people who have built Lockwoods, I would agree with Graham that making the ends circular -- and then transition them into flat lozenge section -- would be a good idea. Also, the curved lip on the intake seems to be as essential to good functioning as foreplay is to orgasm.

Post by **Mike Everman** » Mon Dec 15, 2003 6:00 pm

OK, answers in no particualar order:
1. I was going to start with a 2" dia, then make a 3", then a 1".
2. A small flare at the intake was assumed, but opening all the way out to full dia? Hmmmm. I can't imagine anything terribly wrong with that, I can certainly try it easily enough.

Graham, the engine is proportioned as the Kentfield version Lockwood. Knowing that this initial unit is 2" dia, what frequency and exit velocities should I expect? I am considering folding it like that Ecrevisse lifter, and want to make some preliminary estimates on where to make the bend...

Thanks guys, this will be fun! (and frustrating) and Fun! (and frustrating)....etc.