Atom Jet with applied EVG

[Mark]

Mark, are those petals of the same thickness? It looks like simply a scale change between the two.
Joe[/quote]

Yes, both the Tiger and Dynajet reeds are .006ths. And my Bailey pulsejet reeds are also .006ths. When I first got into pulsejets my oldest brother who gave me his Dynajet, measured the reeds and I bought this enormous roll (6 inches X 15 feet) of blue tempered spring steel from a company in Chicago in the .006ths thickness. Later I bought a caliper and Starrett micrometer and again measured all three pulsejet reeds that I own - the Tigerjet, the Dynajet, and the Bailey pulsejet. All three mic out at .006ths. I have some wide/large outboard motor reeds in a 9 flower petal design where each petal is slightly over 3/4 of an inch in diameter or very close to 2 centimeters. They are .008ths in thickness.
Here is how the 9 petal design looks compared to the Tigerjet and Bailey pulsejet reeds. Pay no attention to the really neat canister for holding nuclear materials with a fine thread, knurled , screw on lid or the colored slinky. They are a distraction. ha

[Mark]

With painstaking measuring with both calipers and mic, they both read the same thing. The breakdown is this. The rectangular reeds at top are .010ths thick. The next row down with the two kinds of jumbo round petal reeds, they both are .008ths. At first, I erroneously tried to measure them mounted and got a thicker reading as bending them to get a bite on them affected the reading. The curious 8 petal reed with spoked retainer design measures .007ths. At the bottom right, the Bailey jet reed thickness is a neat .006ths every time I measured it. The jam jar lid with flower petal design I included was just something odd I came across. So here are some reed thicknesses across the board.

The eight petal valve that is .007ths thick, the one pictured with the spokes, each petal is 1/2 inch wide. I should have twisted the brass spokes over the reeds so that you could see the gap between reeds. I noticed from the plans the Atom jet reed is 46mm wide whereas this reed is ~50mm or about 2 inches in diameter. Also a single Atom petal is 9mm wide and with my similar 8 petal reed, a single reed is ~13mm at its widest. A Bailey jet single petal is around 10 or 11 mm wide as I measure it. The Atom has a reed thickness of "0,2m/m". That is equivalent to .008ths in conversion.
http://www.mail-archive.com/lute@cs.dar ... 01753.html

[woody500]

Hi Mark, Atom jet valve is 46mm diameter. Phil.

[WebPilot]

 Joe, I have these dimensions correct ... right?

[Mark]

Hi Mark, Atom jet valve is 46mm diameter. Phil.

Thanks for that correction Phil. I think my eyes and brain were getting tired putting all those reeds on display with thicknesses and diameters and hopping back and forth from the Atom plans. I will change the 47mm to read 46mm to be correct in my previous post. It's a bummer if you build something and the parts don't line up just right. Thanks again for catching that.

[PyroJoe]

Yes Forrest dimensions are correct,
Looking good, the only thing that is a little open to interpretation is the thickness, mostly the ,2mm comes out to .0078" but most builders note .008", not sure what the actual thickness is and how much it varies from batch to batch. The thickness of course can change things considerably, as you have explained very well in previous topics.

Oh, hold on, think I missed something, be right back...
Joe

[PyroJoe]

$#^^%^%&&**&%* Freakin' horse knockers,
Anyone see something wrong with this picture? I knew I was missing something!

[PyroJoe]

Well, I'm good if I leave out the arcs/fillets at the base of the petal (although the dimensions run through BASIC reflect .0823 which inluded the arc/fillet). The thinnest 3.5mm in reality would be a little higher up, but there is no dimension of the radius, I guess it is one of those gray areas, unless someone has dimensions on that radius.
Joe

[PyroJoe]

With the increase in the retainer diameter, the value becomes larger. So is this significant, or are we splitting hairs?

[PyroJoe]

Will need to strip the fillets out and re-do the .0823 dimension. No way around that one.

[WebPilot]

Based on this previous image in my other thread,



as long as the fillets are not too large, (i.e. their point of contact is below the blue horizontal line which is below the symbol, β), they don't enter the equation. (Radius 0,25 OK but not R 0,5)



What I do have concern over is how the blue print petal is not drawn relative to the center of the retainer, quite unlike the Dyna-Jet.



I wrote my code(s) with Dyna-Jet like valves in mind. This may not be a problem with my first method, like the one you are doing, but may be with my simpler, 3 parameter code. A check is in order.

Are you or Phil going to do and post a video or sound file of the cold excitation of the mounted valve(s) against the plate? It's time. It certainly will answer some questions.

[PyroJoe]

Phil may beat me to it, but I will setup a test. May take a few days to get everything put together with the accuracy that is involved. Do you see any problems with overcutting the petals to where the fillets are under the valve retainer? Basically eliminating the fillets?

[WebPilot]

... Do you see any problems with overcutting the petals to where the fillets are under the valve retainer? Basically eliminating the fillets?

Nope. The analysis models it that way. I feel the fatigue cracks occur not so much due to a 'notch' or stress concentration where the fillets are located but rather the exceeding of the number of cycles above the endurance limit of the metal.

And to make it even easier I would do just one petal attached to an Aluminium plate with 1 hole and one surface ground smmooth. You may want to use this again for some flow tests.

[PyroJoe]

Will do.

[PyroJoe]

Here is the re-do without the fillets, using 3.5mm as the base.
Inputs into BASIC:
input1: .5540 length of rectangle 1
input2: .0689 width of rectangle 1
input3: .008 thickness of the valve
input4: .3234 distance to center of mass of side lobe
input5: .0353 area of side lobe

what is the length of CAD rectangle 1?.5540
what is the width of CAD rectangle 1?.0689
what is the thickness of petal valve?.008

'Continuous beam', partial system frequency
Young's modulus, E: 30000000 lbf/in^2
density: 0.283 lb m/in^3
thickness of beam strip: 0.008 in
width of beam strip: 0.1378 in
length of beam strip: 0.554 in
1st moment of inertia: 0.58794667e-8 in^4
mass per unit length: 0.3119792e-3 lbm/in
wl = 5353.83841 rad/sec
fl = 852.089847 Hz

What is the longitudinal distance to the CM of a side lobe?.3234
What is the area of one side lobe?.0353

Lumped mass, partial system frequency
w2 = 6149.76039 rad/sec
f2 = 978.764764 Hz

System resonant frequency
ws = 4038.01285 rad/sec
fs = 642.669706 Hz

276.397/642.669706=0.430