Blast Compression Intake proposed design

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larry cottrill
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Re: Blast Compression Intake proposed design

Post by larry cottrill » Wed Jan 26, 2005 4:49 pm

Ogge wrote:They include changes in wavelength due to temperature variations as well as differences in velocity which drive that wavelength change. The waves are no longer traveling at C (speed of light) as in electrons but at the variable speed of sound in this environment.
Even the speed of light varies - it is slightly slower than C in normal air, and MUCH slower in high density materials, such as glass. So, the wavelength changes within optical materials. In fact, it is possible to design optical surfaces entirely by looking at how the change in refractive index alters the speed over the path distance within the optical material. Optical design by such methods was mainly perfected by the late great A. E. Conrady during WWII and by his daughter after his death. It is usually known as the 'Path Difference Method' and [usually used in conjunction with other methods] can yield extremely accurate results in optical design.

The speed of light inside a diamond is LESS THAN HALF its speed in air, though the alteration varies slightly by frequency, of course ['slightly' only because the bandwidth of visible light is incredibly small]. The ratio of speeds of the same light in two media is the exact inverse of the ratio of the media refractive indices. [The refractive index of an optical material as normally given in the tables is relative to normal air - lenses used in the vacuum of space must have their indices adjusted for correct design.]

Another phenomenon of interest is 'internal reflection'. This is most easily observed in a flat-sided glass aquarium, where at certain angles of looking through the front of the tank, the side walls seem to be perfect mirrors, while at other angles they appear transparent. This is the type of reflection where a wave tries to move through an interface from high to low refractive index [in the aquarium example, the observed reflection is off the glass/air interface, not the water/glass interface]. At steep angles, there is no reflection, at shallow angles total reflection. If the angle is VERY shallow, only a slight difference in density is needed for total reflection as observed in mirages off the hot layer of air over hot pavement or desert sand. There must at least be the possibility of this occuring to sound waves at interfaces between cool, dense air and warm, less dense air. A good example might be knowing whether some types of sonar are affected by reflection off thermoclines [interfaces between two temperature layers] in the ocean, or even reflection off the wavy surface. I have no such knowledge, but I suspect that this is true.

Adam, is there such a thing as refraction of radio waves? Can you think of easily explained examples? [Just a curiosity question, not having much application to anything we're talking about.]

L Cottrill

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Re: Blast Compression Intake proposed design

Post by Nick » Wed Jan 26, 2005 7:31 pm

Guys
There is a way to settle all this back and forth theoretical discussion.
Build, test and let the results speak for themselves.
Dave

Amen!

But seriously the BCI looks very complex, you said you were going to mill it out of slabs of alloy?. how big is it? i dont want to teach you how to suck eggs but couldnt you make a prototype from tubes and sheet metal first?. it would be quicker and cheaper?!. Whatever i look forward to the results.
great stuff!
Nick

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Re: Blast Compression Intake proposed design

Post by Ogge » Wed Jan 26, 2005 10:11 pm

Larry Cottrill wrote: Adam, is there such a thing as refraction of radio waves? Can you think of easily explained examples? [Just a curiosity question, not having much application to anything we're talking about.]

L Cottrill
Yes, If I remember correctly, this is why you cant get high frequency RF to a submarine. You must use an Ultra Low Frequency or the waves do not penetrate to any great depth or reflect of the surface.

There is a huge antenna somewhere in the midwest that allows transmitting at a very slow rate. On the order of something like 1 bit over several seconds if I remember correctly.

The sub has to trail a huge attenna cable behind it to recieve instruction while at depth.
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Re: Blast Compression Intake proposed design

Post by Ogge » Wed Jan 26, 2005 10:24 pm

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Last edited by Ogge on Sat Jan 29, 2005 12:28 am, edited 1 time in total.
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Re: Blast Compression Intake proposed design

Post by steve » Wed Jan 26, 2005 10:44 pm

All I can say is: have fun building it! (insert comic sarcasm here)
If it works, it would be rather spectacular, but I just wouldn't want to have to build that thing.

It just has PDE written all over it! very impressive.
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Re: Blast Compression Intake proposed design

Post by Mike Everman » Wed Jan 26, 2005 10:50 pm

Adam,
I highly recommend getting some practical experience on a simpler design. Get used to fuel and spark delivery, etc. Helps you get a "feel" that is far from wasted time. This was the recommendation to me about a year ago, so full of Wild Ideas was I. I am so glad to have been given this advice, and my excursions are now a bit tempered, but the dream is still alive, and I've been able to keep some original bits as I went along. If I had attempted my early designs, I would have been in for a great deal of frustration and might not be where I am... Where is that? It can all be found here!
Mike
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Re: Blast Compression Intake proposed design

Post by Ogge » Wed Jan 26, 2005 11:04 pm

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Re: Blast Compression Intake proposed design

Post by larry cottrill » Wed Jan 26, 2005 11:55 pm

Ogge wrote:Larry,

BTW did you get my private message? Its been in my outbox since yesterday. I edited a reply I made to your earlier post, please go back and read the changes.
Yes, just saw it.

Hey, no problem - I've been hurt worse. You ought to see some of the discussions I got into on the old forum ;-)

L Cottrill

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Re: Blast Compression Intake proposed design

Post by Mike Everman » Wed Jan 26, 2005 11:55 pm

You should know that some of the tests that Eric and Steve have made on the suggestion of others are a very rare thing. Everyone typically has their own goals for the limited fire and noise time we get, so having your own pulse combustor to try out your reflections and refractions will be essential to my mind.
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Re: Blast Compression Intake proposed design

Post by larry cottrill » Thu Jan 27, 2005 3:07 pm

Ogge wrote:I have attempted to get at least some experiments done. For example when I asked about a reflector placed out from the FWE intake to reflect constructive feedback into the CC. Unfortunatly no one was taking me seriously. I had my BCI in mind when I requested the test.

A simple tube with plugged end could be aligned with a running FWE rear facing intake realatively easily. If no one was willing to do the test, I figured I would build one and test myself. I just wanted to throw out my ideas and designs 1st to see if anyone saw any obvious flaws in my logic before attempting anything.
Well, I took it seriously, and have proposed such a thing before. I'd like to try this - I'm just not up to building anything until it warms up a little out in the garage. To me, it looks especially good in light of Steve's success in using a 'straight in' intake snout. I proposed that moving the 'bucket' toward and away from the intake could be used as a throttling method, due to interference/reinforcement wave effects.

Of course, my assumption always was that it would take a LOT of experimenting to get this set up just right.

L Cottrill
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Front end intake with reflector bucket. Drawing Copyright 2003 Larry Cottrill
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Re: Blast Compression Intake proposed design

Post by pezman » Thu Jan 27, 2005 4:38 pm

Hmm, maybe Steve would be willing to hold a parabolic shell in front of the intake of his latest FWE to see if it can be positioned in such a way as to augment the thrust.

I managed to get a nice, steel parabolic shell from a lamp that I bought at Wal-Mart (bought it precisely because it had some parabolic and hyperbolic shapes that looked like they'd be nice starting points as PJ parts). The lamp cost about $9.

The shell is about 3" in diameter at its widest point and maybe 4 or 5" long. It should be easy to hold something like this in gloved hands and move it to various positions to see if it has an beneficial effect. I've done some experiments firing my "mini-Gaz-ex" into this shell and when the end of the tube is just the right distance into the shell the resulting concussion is surprisingly powerful.

If a "sweet spot" can be pinpointed, it should be easy enough to affix the shell at that position. If not, you're out $9, but you will have managed to warm your hands in the process (that's got to be worth something).

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Re: Blast Compression Intake proposed design

Post by Mike Everman » Thu Jan 27, 2005 4:49 pm

edmund scientific has a variety of polished aluminum parabolic reflectors for pretty reasonable price. i've been wanting to try putting one around the tail facing the rear, with the tail opening at the focus, to direct the pressure pulse to the rear. a noise abatement attempt I'll eventually get around to. it would be draggy, but I'm dreaming of VTOL thrusters.
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Re: Blast Compression Intake proposed design

Post by Ogge » Fri Jan 28, 2005 12:55 am

On another note, I guess I should stick to my own threads. It appears that Im not welcome to offer facts or opinions in one of Eric's threads.
Last edited by Ogge on Sat Jan 29, 2005 12:00 am, edited 2 times in total.
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Re: Blast Compression Intake proposed design

Post by Ogge » Fri Jan 28, 2005 1:08 am

pezman wrote:
I managed to get a nice, steel parabolic shell from a lamp that I bought at Wal-Mart (bought it precisely because it had some parabolic and hyperbolic shapes that looked like they'd be nice starting points as PJ parts).
Sounds like a worthwhile investment. My only concern would be the distance from the intake with a parabolic reflector. You will note on the BCI that the reflector is actually about the distance of the exhaust. This is to time the reflection near the exhaust reflection to attempt to time the enhancement just when the engine is going into overexpansion on the refresh cycle.

With a parabolic reflector you have to be at the sweet spot AND time it correctly with engine requirements.
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Re: Blast Compression Intake proposed design

Post by Mark » Fri Jan 28, 2005 1:13 am

Mike Everman wrote:Adam,
I highly recommend getting some practical experience on a simpler design. Get used to fuel and spark delivery, etc. Helps you get a "feel" that is far from wasted time. This was the recommendation to me about a year ago, so full of Wild Ideas was I. I am so glad to have been given this advice, and my excursions are now a bit tempered, but the dream is still alive, and I've been able to keep some original bits as I went along. If I had attempted my early designs, I would have been in for a great deal of frustration and might not be where I am... Where is that? It can all be found here!
Well phrased.
Mark
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