On Friday, September 15, 2017 at 2:28:25 AM UTC-4, jrwal...@gmail.com wrote:> On Friday, 15 September 2017 02:43:34 UTC+1, dagmarg...@yahoo.com wrote: > > On Thursday, September 14, 2017 at 8:46:36 PM UTC-4, Steve Wilson wrote: > > > Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > > > > > Did anybody make iron cannons in that era? AFAIK it was Alfred Krupp in > > > > the mid-19th century who figured out how to found steel cannons that > > > > didn't explode randomly. > > > > > > > Cheers > > > > > > > Phil Hobbs > > > > > > Apparently, the USS Revenge sank in 1811. The US Navy just recovered an > > > iron cannon believed to be from the ship: > > > > > > http://www.businessinsider.com/the-navy-just-found-cannon-that-they-think- > > > was-war-of-1812-ship-2017-6?op=1 > > > > > > The 24-pounders were used in the 1700's and made of cast iron: > > > > > > https://en.wikipedia.org/wiki/24-pounder_long_gun > > > > > > Here's a view of hundreds of 1819 24-pounders stockpiled at Fortress Monroe > > > in Virginia: > > > > > > http://moultrie.battlefieldsinmotion.com/Artillery-24-pounder.html > > > > > > They were iron: > > > > > > "The bore-diameter for all these iron 24-pounders was established at > > > exactly 5.82 inches, and they were to weigh roughly 5,800 pounds apiece." > > > > > > http://moultrie.battlefieldsinmotion.com/Artillery-24-pounder.html > > > > > > "The Chinese also mounted over 3,000 bronze and iron cast cannon on the > > > Great Wall of China, to defend themselves from the Mongols." > > > > > > https://en.wikipedia.org/wiki/History_of_cannon > > > > > > Doesn't say when. Maybe the 1500's > > > > Nice info / links. > > > > Cheers, > > James Arthur > > A mixture of iron and bronze cannon was found in the remains of the > Mary Rose which sank in 1545 and which was launched in 1511. > > JohnAs I recall Hornblower commented on his brass stern and bow chasers, but other-wise had iron cannon's. George H.
Naval Cannon Search Magnetometer/Induction Coil Circuit
Started by ●September 14, 2017
Reply by ●September 15, 20172017-09-15
Reply by ●September 15, 20172017-09-15
> Speake, a British company, sells a fluxgate board for something like > $25. Stefan Mayer Instruments has something similar. It's apparently > not real hard to do. > > (I know all this from a failed NMR mag field compensation project.) > > A few fluxgates in an array could make a differential field sensor, > that could sense the gradient from a big hunk of iron. >I found this fluxgate from TI. http://www.ti.com/product/DRV425/description My concern is how to dynamically maintain a constant orientation relative to earth magnetic field reference. The speed of moving the sensor might allow filtering out vibrations in the sensor. Vibrations being an alteration of orientation. But the technology from TI has an evaluation board to try out. So I will get one. thanks
Reply by ●September 15, 20172017-09-15
"Steve Wilson" <no@spam.com> wrote in message news:XnsA7F0DB8DF3A55idtokenpost@69.16.179.23...> They probably made other things from iron: bridges, tools, machines, etc. > > With all this iron around, how did they keep it from rusting?It was gray iron, which naturally corrodes slower than say, mild steel. There may be some treatment at work, too. A well seasoned cast iron pan is good for a long time. A baked oil finish is probably ancient.> Even today, rust is a major problem. I moved back to Ontario after living > in the US for 30 years. I was astonished to find how quickly everything > rusted, often to the point of unusability. Cars, tools, you name it. > > If this is such a problem today, how did the oldtimers cope?They also didn't use salt on their roads (what a terrible waste of an expensive commodity!). Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●September 15, 20172017-09-15
"George Herold" <gherold@teachspin.com> wrote in message news:b043bb44-71dd-41b6-9f67-875141eedffa@googlegroups.com...>> it changes the inductance by acting as a poorly coupled shorted turn > > Right, I was trying to understand how that changed the inductance. > I'm using the model that 1/2LI^2 is equal to the integral of B^2 > over all space. (B^2/ 2*mu_0)A conductive object is diamagnetic at AC, tending towards B ~= 0 around the object; so it casts a shadow, so to speak, reducing the volume of the field, and therefore the inductance. It might be worth noting that the magnetic path length shrinks, too (and L = mu * Ae/le), but the area shrinks faster. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●September 15, 20172017-09-15
On Thursday, September 14, 2017 at 8:32:45 PM UTC-4, John Larkin wrote:> On Thu, 14 Sep 2017 14:02:56 -0700 (PDT), eaglesondouglas@gmail.com > wrote: > > > > >> > > >> > Here I would increase the ac frequency to make a coil Q of the required > >> > number, 1 to 10. > >> > >> Are you trying to sense the metal by having it spoil the Q, > >> or shift the frequency? In both case I might want a higher Q. > >> > > >> > >Yes, I am not a engineer kind of guy. But my inclination is to > >hope that steel or iron would alter L the coil inductance. Does > >this mean technically altering Q? > > Mostly inductance. Iron will make it go up, brass down. > > > > >From what I read this type of bridge works best at a Q of one > >to ten. Is ramping it up to 100 allowed? > > Likely not possible at audio-type frequencies. > > > > >I have an audio oscillator and wonder if I can just add an audio > >amplifier for the power source. > > You can make an AC bridge, drive it with a good sine wave, listen to > the null with amplified headphones, tweak the bridge or the frequency > for a deep null. > > I guess you could use a resonated loop in an AC bridge, too. Might be > more sensitive. > > > > >thanks doug > > What would you do next if you found a cannon? > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.comA bridge will be experimented with. Concerning using headphone. Can I just measure bridge balance with a frequency to voltage converter and measure voltage with my electrometer? I plan on sending survey data to the US Navy. And also a professional wreck hunter. And hope to get a Navy permit to recover them. I can't do recovery work.
Reply by ●September 15, 20172017-09-15
On Thursday, September 14, 2017 at 8:55:28 PM UTC-4, dagmarg...@yahoo.com wrote:> On Thursday, September 14, 2017 at 10:51:06 AM UTC-4, millssc...@gmail.com wrote: > > Hello: > > > > I am trying to make a homemade circuit to do underwater detection > > of old War 1812 US Navy ship cannons. Magnetometers can be > > bought, but they are expensive. So, I am looking at a metal detection > > type circuit. I came across the Maxwell Bridge circuit. > > > > See: > > https://en.wikipedia.org/wiki/Maxwell_bridge > > > > > > Here I would increase the ac frequency to make a coil Q of the required > > number, 1 to 10. > > > > My question is can I use the coil L3 in the bridge to scan the floor of > > a river for cannon signal? Moving the coil at a certain velocity also. > > The cannon would be about 3 foot deep in the river bottom I guess. I have > > a Keithley electrometer for the galvanometer. > > > > The final coil will be 16 foot in diameter and 2 inches long and 20 turns maybe. The plane of the coil would be run parallel to the bottom surface. > > > > Here is my blogspot on the affair. > > > > http://douglaseagleson.blogspot.com > > > > Any other suggestions are very welcome. > > thanks doug > > > > Also how would a low pass filter be added to the electrometer? > > These sites have a wealth of information about metal detectors (ferrous > and non-ferrous), treasure-hunting, magnetometers, etc. > > Recommended. > > http://www.geotech1.com/cgi-bin/pages/common/index.pl?page=main&file=main.dat > > http://www.hobby-hour.com/electronics/metal_detectors.php > > Cheers, > James ArthurThanks: On the metal detector link there is a Heathkit schmmatic. It runs a coil at 7300Hz. I had kind of hoped to avoid the use of dual balanced search coils. But maybe they are required. My system idea was was to use the effect of motion cause the change in coil inductance and bridge balance. Meaning it could not sense if not in motion, maybe. thanks doug
Reply by ●September 15, 20172017-09-15
"Tim Williams" <tmoranwms@gmail.com> wrote:> "Steve Wilson" <no@spam.com> wrote in message > news:XnsA7F0DB8DF3A55idtokenpost@69.16.179.23... >> They probably made other things from iron: bridges, tools, machines, >> etc.>> With all this iron around, how did they keep it from rusting?> It was gray iron, which naturally corrodes slower than say, mild steel.Possibly. Wikipedia says: "Compared to the more modern iron alloys, gray iron has a low tensile strength and ductility; therefore, its impact and shock resistance is almost non-existent." https://en.wikipedia.org/wiki/Gray_iron So it wouldn't be much good in guns.> There may be some treatment at work, too. A well seasoned cast iron pan > is good for a long time. A baked oil finish is probably ancient.I wonder if that could be applied to guns and bridges.>> If this is such a problem today, how did the oldtimers cope?> They also didn't use salt on their roads (what a terrible waste of an > expensive commodity!).Not to mention the ecological damage. But iron cannons on boats would suffer corrosion from the salty air. I need to do more research. If the oldtimers found some method, maybe I can use it on my cars and tools.> Tim
Reply by ●September 15, 20172017-09-15
On Fri, 15 Sep 2017 06:25:43 -0700 (PDT), eaglesondouglas@gmail.com wrote:> >> Speake, a British company, sells a fluxgate board for something like >> $25. Stefan Mayer Instruments has something similar. It's apparently >> not real hard to do. >> >> (I know all this from a failed NMR mag field compensation project.) >> >> A few fluxgates in an array could make a differential field sensor, >> that could sense the gradient from a big hunk of iron. >> > >I found this fluxgate from TI. > >http://www.ti.com/product/DRV425/description > >My concern is how to dynamically >maintain a constant orientation relative to earth magnetic >field reference.If you had two (or more) sensors some feet apart and took the difference, the outputs would mostly cancel in a uniform field. A big iron cannon would create a local distortion that would disturb the balance. Fun would be a big sheet of sensors. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●September 15, 20172017-09-15
On Fri, 15 Sep 2017 06:34:19 -0700 (PDT), eaglesondouglas@gmail.com wrote:>On Thursday, September 14, 2017 at 8:32:45 PM UTC-4, John Larkin wrote: >> On Thu, 14 Sep 2017 14:02:56 -0700 (PDT), eaglesondouglas@gmail.com >> wrote: >> >> > >> >> > >> >> > Here I would increase the ac frequency to make a coil Q of the required >> >> > number, 1 to 10. >> >> >> >> Are you trying to sense the metal by having it spoil the Q, >> >> or shift the frequency? In both case I might want a higher Q. >> >> > >> >> >> >Yes, I am not a engineer kind of guy. But my inclination is to >> >hope that steel or iron would alter L the coil inductance. Does >> >this mean technically altering Q? >> >> Mostly inductance. Iron will make it go up, brass down. >> >> > >> >From what I read this type of bridge works best at a Q of one >> >to ten. Is ramping it up to 100 allowed? >> >> Likely not possible at audio-type frequencies. >> >> > >> >I have an audio oscillator and wonder if I can just add an audio >> >amplifier for the power source. >> >> You can make an AC bridge, drive it with a good sine wave, listen to >> the null with amplified headphones, tweak the bridge or the frequency >> for a deep null. >> >> I guess you could use a resonated loop in an AC bridge, too. Might be >> more sensitive. >> >> > >> >thanks doug >> >> What would you do next if you found a cannon? >> >> >> -- >> >> John Larkin Highland Technology, Inc >> picosecond timing precision measurement >> >> jlarkin att highlandtechnology dott com >> http://www.highlandtechnology.com > >A bridge will be experimented with. >Concerning using headphone. Can I just measure bridge balance >with a frequency to voltage converter and measure voltage >with my electrometer?The frequency of the bridge null won't change; only its amplitude and phase. It sounds like you're not an electronics guy, so you could get some help here. I suspect that lots of people would be interested. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●September 15, 20172017-09-15
Steve Wilson <no@spam.com> wrote:> > With all this iron around, how did they keep it from rusting?It really was iron, either wrought or cast. Neither of those rusts particularly quickly.> Even today, rust is a major problem. I moved back to Ontario after living > in the US for 30 years. I was astonished to find how quickly everything > rusted, often to the point of unusability. Cars, tools, you name it.They are all steel, which rusts far more quickly than iron. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
