tinkerer

"My preferred one is liquid hydrogen at 1atm with vacuum insulation. "

Please explain how hydrogen may be kept liquid at 1 atm. pressure? 

In my own case, I had been very active during my teens and early twenties engaged in building fast cars. High school included Biology, Physics, Pl. Geom., Alg. I & II, Chem., Trig., and several shop courses. As a necessity, I became quite proficient in many skilled trades working on the cars. Thus, when I started college aiming at Engineering, I had a very good ability to perform skilled work and a foundation for the more theoretical Engineering topics. I could have secured employ as a Machinist, Pipefitter, Welder, or the like, but felt I never would be satisfied earning a living thusly. Marriage did not interfere; I took night courses in Physics and Chemistry, went on to enroll at age 31 at the University of Nevada, Las Vegas, in Engineering, full time. I received my B.S. Engineering at age 34.

It can be done. Winding up supervising a team of skilled maintenance workers in a manufacturing  plant confirmed the universal disdain the skilled have for Engineers.......until they learned I could often out-perform them!

As a Sophomore in high school, a rotary high-voltage interruptor I had built myself to copy one of Strickfadden's similar devices in a Frankenstein movie was used to build an operating high-voltage high-frequency Tesla coil. I could not enter the Science Fair as I was not in General Science, but my friend took it over and won second place!   Just reminiscing, sorry.

On 1/9/2019 at 4:23 AM, studiot said:

 

 

Hello,

You video is quite a good one - if you understand some basic facts so I will tailor my comments to the video.

But first try this experiment.

Take a book of heavy sheet of carboard or wood and see how fast you can wave it through the air.
You should have not trouble feeling the air resistance.
And the harder and faster you wave the greater that resistance.

It is this air resistance that is the key to the operation of both the turbine and the compressor.

Rotating turbines and compressors have two basic modes or types of operation.

Fluid (air) can enter or leave at right angles to the disk of  blades, along or parallel to the shaft.
This air is then directed outwards by the action of the blades against the air resistance.
As you found out in your experiment the greater the speed the greater the effect.
That is why the blades need to spin so fast.

This action turns the air flow through a right angle so it is now moving at right angles to the spinning shaft and parallel to the disk of blades.
The blades themselves are specially shaped to facilitate this.

The air then leaves or enters the casing at a hole in the outer edge into a pipe.

Note I said the air can enter or leave and then it leaves or enters.

You video shows this very well, can you identify which way the air is flowing in the turbine and the compressor parts?

Hint they are opposite directions.

This type of turbine or compressor is called a radial flow machine.

 

The other type is called an axial flow machine.
Here the air enters parallel to the shaft and does not change direction.
It remains flowing parallel to the shaft and so enters the machine at one end and exits at the other.

This type of compressor is used in jet engines.

I enjoyed the simple way you presented that! For me, it's a matter of air being a compressible fluid, and when compressed such that it experiences pressure greater than atmospheric pressure, it has the ability to move, to flow, attempting to relieve that pressure. Squeezing air to make it move is a much more forgiving process than doing so with a liquid, which is for most practical considerations, incompressible. However that fact may be, even metals can be compressed if subjected to extremely high stresses. If this copies, here is a chunk of metal being compressed under millions of pounds per square inch, the event copied by extremely high-speed X-Ray images:

On 1/10/2019 at 3:51 AM, StringJunky said:

That was a bit I picked up off an OU programme a long time ago.  

Many years ago, as a kid, we heard about the "goodness" present in Sunlight, that is, UV. UV lamps were sold specifically to be placed in the rooms of infants to "cleanse" the air. Window glass was marketed with the quality of transmitting far more UV than normal glass: it was called "Vitaglas", possibly with two "s"es. I have searched in vain for reference to Vitaglas.

1 hour ago, StringJunky said:

If it's the stuff I'm thinking of, it's highly flammable.

Celluloid is made of nitrocellulose and camphor. Nitrocellulose is the basis for almost all Smokeless Propellants, smokeless powder in vernacular. We made nitrocellulose out of thin paper and used it as magicians do with their "touch paper"; ignited, it burns completely emitting no smoke, and leaving virtually no ash. Some of the nitrated esters also burn completely, a different kind of "burning", actually a dissociation of the molecules into the component elements contained. One would be Propanetriol.

On 1/9/2019 at 8:41 AM, Strange said:

You would need to find some way of moving the conductor through the magnetic field. Silvestri shows one example. Not exactly an economical way of generating power. But if a satellite is already using a tether for some other purpose, you could get a bit of extra power from it.

Otherwise you could use some source of energy (hydroelectric, steam turbine) to rotate a wire or coil. But the Earth's magnetic field is very weak, so a generator like that would be much more efficient if you put a large magnet in it!

But, no, you can't "suck in the magnetic field".

One of my instructors long ago suggested that in understanding an electron's dropping down to a higher energy level, which results in ejection of a photon, think of light  emission as being caused by "successive suck-ins". One never forgets such an illustrious explanation.

On 12/26/2018 at 10:06 AM, Enthalpy said:

Alternators have been used at radio transmitters, long ago, between spark-gap and vacuum valves. What ol' Nikola did, I ignore it.

They had big numbers of pole pairs relatively prime at the rotor and the stator, so that for a given rotation frequency, the stator and rotor poles that just began to overlap passed quickly from one pair of elements to an other. Well done.

While this scheme is efficient at removing the current components at low frequencies, it doesn't amplify the desired radio frequency, it only keeps it. So the field at the pole edges had to be very sharp, with edges at the metal and a very thin airgap.

Imagine 100m/s rotor speed, difficult enough then: 1mm transitions in the field could produce AC current with strong components up to roughly 2*10µs or 50kHz, reaching the LW. But any pole length over 1mm was waste, producing components at lower frequencies removed by the relatively prime scheme. Poles 1mm long would have been more efficient but impossible to produce.

I had thought at modernizing the alternator. Silicon can rotate at 500m/s, with patterns and gaps few 10nm small. The alternator could be electrostatic rather than electromagnetic. The achievable frequency is the same as the read throughput of a mechanical disk drive, that is, 200MB/s=2Gb/s would achieve 1GHz energy conversion - or rather less for a significant power hence facing area. But magnetrons do that better.

Fascinating! Recently, I looked up the theory of Magnetron operation, as I had studied it in the early '60s as a Technical School student. The poles, basically axial keyholes in the I.D. of a cylindrical chunk of conductive non-ferrous material, copper commonly I think, form a tuned  resonant circuit in which the pole faces form the capacitive plates, the poles the inductor. To me, simple-minded, this concept seems to border on original design madness. Yet, it works quite well. 

@Strange    RE:   "A magnetic field is generated by a changing electric current."

This would imply that no magnetic field exists around a conductor carrying a constant direct current. 

Is that so? My Electric Theory course in Freshman High School provided an experiment in which powdered iron arranged itself allowing us to "see" magnetic lines of force about a current carrying conductor. 

On board ship, my co-worker, ex-Navy, told of D.C. welding cables lying on the steel hull doing all sorts of dances at times.

"Seawater contains very few metal ions.    "This leads me to wonder: The two commonly considered water "hardness" elements are Calcium and Magnesium. Both are thought of as metals. Both are present in virtually all water present naturally upon this planet. Both contribute to the factor arbitrarily called "water hardness".  Therefore, the statement regarding Seawater containing very few meta lions, seems misdirected, at best. 

However, what is your point, Grandma? Obviously seawater is highly ionized, but so what? 

On 1/3/2019 at 7:08 PM, J.C.MacSwell said:

Sorry to hear that. Not something anyone would fully get over...even 50 years later.

An experience greatly unexpected, to be sure, and gravely disruptive within our little family. My wife had a brother, then 16, and sister, 11, both of whom were left homeless with the only other relatives present in America being my wife and I. Certainly most curious result was the fact that during that period, I had been called up for Armed Forces Induction, the Viet Nam conflict at it's height. Having officially become responsible for two minor children, I appeared before the Local Draft Board in our town's Post Office basement. When asked to describe circumstances, upon hearing "murder-suicide", one lady gasped, recalling the event had taken place just across the street! Almost instantly, my father in law's maniacal act had quite possibly saved my life!

On 12/31/2018 at 5:48 PM, Moreno said:

A sorbent could reduce propane tank weight a lot and allow to make it of more conventional and cheaper squarish shapes. Commonly propane liquifies at 12-15 bars and require heavy tank. In a sorbent it can be stored at 1 bar pressure or even lower what still may provide sufficient supply to the engine. 

Acetylene gas is stored in steel tanks in fashion similar to your description. It is absorbed by an inner material, carbon, I believe, possibly saturated with acetone, but I forget where I heard that. Typical pressure encountered with usual surrounding temperatures is several hundred pounds per square inch. I have always heard it is stored thusly for purposes of safety, but never understood the issue. 

I expect @John Cuthber has greater knowledge of this than I, and perhaps he will share.

On 12/31/2018 at 5:48 PM, Moreno said:

A sorbent could reduce propane tank weight a lot and allow to make it of more conventional and cheaper squarish shapes. Commonly propane liquifies at 12-15 bars and require heavy tank. In a sorbent it can be stored at 1 bar pressure or even lower what still may provide sufficient supply to the engine. 

Interesting to note here that it is common practice in industry (at least here in the States) to use liquid propane fed directly in that form to the engines of fork-lift trucks. Perhaps delivery volume is inadequate in gas form, made even worse by the cooling effect on the tank of gas leaving it, which lowers the pressure. Such operation would likely be unstable. Delivering liquid ensures fairly constant pressure, so long as surrounding temperature remains relatively constant.

On 1/1/2019 at 1:24 PM, Moreno said:

What do you think could become the most common type of a motor fuel, if plug-in hybrid will become the most common type of vehicle and cars will use only 10% of fuel they use today? I think for now there may be insufficient supply of propane or ethanol to replace all the gasoline and diesel, but what if cars will use many times less fuel than now? Will global transition from gasoline and diesel to cleaner fuels make sense?

IMHO, a glut of gasoline will present itself should a fairly rapid transition, say, changeover for a following model-year occurs, making it the predominating fuel. However, gasoline prices are highly variable, and quite manipulable. I should think if considerable differences exist regarding exhaust emissions between liquid fuel and gaseous, that will affect the result. Hydrogen usage, of course, is most preferable in that respect. Personally, I've witnessed too many hydrogen explosions to yet become comfortable with it's general use. Ask the Germans!

On 12/19/2018 at 3:26 AM, John Cuthber said:

The freezing point of butane is -140C. That's 40 degrees colder than the worst bits of the antarctic. Butane didn't freeze in the pipes.

The difference in boiling points is significant.

Correct. However, the concern is that if the liquid will not BOIL, no pressure to deliver it is readily available. IOW,

On 12/19/2018 at 7:12 AM, Itoero said:

Yes, I'm sorry I wrongly quoted. I just learned how it works.

Not to feel badly; it was not until I was in my 60s that I learned the veins returning blood from lower extremities are surrounded by tiny muscle structures which contract one following another, as the heart brings blood back upwards, against gravity. They act in effect as check valves, holding the blood between them when the diastolic (resting) part of the pulse presides, preventing a coursing up and down of the contents.

Truly amazing!

Our plant in Indiana used Propane in winter when natural gas supplies were curtailed. Two 30,000 gallon tanks of it. A sudden "cold snap" resulted in a noticeable slow-down of the boilers' output, then cessation. Determined the "propane" was freezing in piping connecting the tanks to the plant building. Subsequent investigation determined that the LPG supplier routinely blended BUTANE with the PROPANE, as it was less expensive. The customer normally never knew........until his pipes froze with the much higher freezing-point butane! 30 degrees F.

7 hours ago, studiot said:

I'm very glad to see you are asking a sensible question instead of pushing nonsense from cranks.  +1

But beware there are many cranks using/hiding behind the Tesla brand.

 

No Tesla didn't have an audio amplifier or an oscilloscope.

But he did use coils.

The system was known as a 'spark gap device'.

Bsically the making and breaking of a mechanical contact causes electrical oscillations in an inductive system.
The faster the contats make and break, the higher the voltage and the frequency.

https://teslaresearch.jimdo.com/invention-of-radio/spark-gap-transmitter/

Remember also what they called high frequency would not be regarded as very high today.
Nowadays the High Frequency band (HF) is officially in the 3Mhz to 30 Mhz range which is not very high compared to a mobile phone in the 1 to 15 giga hertz range.

Final comment, when you break the contacts a phenomenon called inductive backswing occurs.
This can be a very high voltage and is the basis of creating several hundred volts in an automotive distributor.
These several hundred volts are then transformed to several kilovolts by the 'automotive coil' acting as a transformer.

 

Interestingly, a typical home-designed Tesla Coil uses 60 HZ as it's primary frequency, usually at reasonably high voltage, 10kv to 15kv using a commercially available neon lighting or ignition transformer which passes it's current through a primary coil having but few turns, and being interrupted by a spark gap in series. This alternate 60 HZ "nudging" of the primary circuit starts, and maintains, "ringing" or resonance in the secondary coil which is connected in parallel with appropriate capacitance. The degree of "step-up" may be hundreds to one, or more. Thus a million volt presence may be obtained via the secondary, whose values of Inductance and Capacitance are such that the resonant frequency may be hundreds of times the primary circuit frequency.  (whew!)

2 hours ago, Itoero said:

This system involves small valves throughout the veins and muscle contractions from your skeletal muscles when you walk and move about.

Was the question not the opposite? You describe how gravity is overcome returning the blood upwards back towards the heart. The question was how does blood travel from the heart to the feet. Try hanging upside down for some protracted length of time to see how uncomfortably the heart then struggles to overcome gravity getting blood flow to the feet.

10 hours ago, dimreepr said:

What drug did you use?

My optimism was subverted when my new wife's father shot and killed her mother, then taking his own life. She (my wife) was 20, I was 25. Optimism shattered.

On 12/17/2018 at 3:34 AM, swansont said:

CRT steering magnets and degaussing magnets are two very different applications. Permanent magnets would not be used for the latter.

So true. Steering magnets are a new term to me; however, I do recall the smaller CRTs, such as used for oscilloscopes used charged deflection plates, vertical and horizontal, mounted within the envelope. Large CRTs such as TV used electromagnetic deflection via coils surrounding the CRT neck. Those were called "sine coils", for reasons I never learned.

On 12/8/2018 at 1:17 PM, HB of CJ said:

The USA heavy truck industry, (perhaps world wide) for years had "engine brakes" that shut off the diesel fuel and slightly changed the timing of the exhaust(s) valves.  This effectively turned the truck diesel engine into a large compressor, absorbing considerable power.  While going down hill or slowing with the wheels driving the engine, this changed things greatly.  The better more efficient engine brake designs absorbed almost as much HP braking as the engine produced pulling.  If memory serves about 30% of the absorbed energy went out the exhaust pipe as noise and about 70% was absorbed by the cooling system.

The device is known colloquially as a "Jake Brake". I heard valve timing was involved, but never delved into exactly how that was accomplished. Truck diesel engines in general have quite husky valve train parts, and I do know that in some designs, "engine runaway" upon attempting shut-down was thwarted by locking the exhaust valves open.

On 12/15/2018 at 6:59 AM, swansont said:

I find the notion that deflection of moving charges was unexplained in physics instruction before 1962 to be highly dubious

Of course they were explained, but not adequately to a bunch of ruffian young men drawn from every imaginable walk of young adulthood, farmers, recent high school grads (like me), recent military dischargees. The Degaussing magnet I would have to search, today easily done. Thanks for your response.

My point here regarding electron movement within a highly evacuated space is that when I studied and attempted to assimilate it, much less understanding beyond the very basics existed (1962 or so). We had magnets glued to the necks of CRTs which were "Degaussing" devices, for example. No instructors back then explained their theoretical function. But we did greatly enjoy drawing arcs of high-voltage high-frequency origin off of the Horizontal Output Tubes! 

On 12/12/2018 at 12:31 PM, John Cuthber said:

I don't.

Or, at least, they shouldn't be.
It may be simply that, if the soil is too dry for the pH meter to work, the plant dies anyway.

What might you imagine such meters to be then? Off the shelf ten-dollar priced devices capable of measuring H+ ion content?

I have and use such devices, and have forever and a day wondered about "Soil Ph". Rather still "up in the air", though.

Evidently, to me at any rate, ions seem to exist differently on opposing sides of the "pond"......