|
Fun Fact
St. Elmo's fire (also called witchfire or witch's fire)[1] is a weather phenomenon in which luminous plasma is created by a corona discharge from a rod-like object such as a mast, spire, chimney, or animal horn[2] in an atmospheric electric field.
?It has also been observed on the leading edges of aircraft, as in the case of British Airways Flight 009, and by US Air Force pilots.[3] Illustration of St. Elmo's fire on a ship at sea Electrostatic discharge flashes across the windscreen of a KC-10 cockpit. The intensity of the effect, a blue or violet glow around the object, often accompanied by a hissing or buzzing sound, is proportional to the strength of the electric field and therefore noticeable primarily during thunderstorms or volcanic eruptions. St. Elmo's fire is named after St. Erasmus of Formia (also known as St. Elmo), the patron saint of sailors. The phenomenon, which can warn of an imminent lightning strike,[4] was regarded by sailors with awe and sometimes considered to be a good omen.[5] ?????? Cause St. Elmo's fire is a reproducible and demonstrable foZhengHeShips.gifrm of plasma. The electric field around the affected object causes ionization of the air molecules, producing a faint glow easily visible in low-light conditions. Conditions that can generate St. Elmo's fire are present during thunderstorms, when high-voltage differentials are present between clouds and the ground underneath. A local electric field of about 100 kV/m is required to begin a discharge in moist air. The magnitude of the electric field depends greatly on the geometry (shape and size) of the object. Sharp points lower the necessary voltage because electric fields are more concentrated in areas of high curvature, so discharges preferentially occur and are more intense at the ends of pointed objects. The nitrogen and oxygen in the Earth's atmosphere cause St. Elmo's fire to fluoresce with blue or violet light; this is similar to the mechanism that causes neon lights to glow, albeit at a different colour due to the different gas involved.[7] In 1751, Benjamin Franklin hypothesized that a pointed iron rod would light up at the tip during a lightning storm, similar in appearance to St. Elmo's fire.[8][9] In an August 2020 paper, researchers in MIT's Department of Aeronautics and Astronautics demonstrated that St. Elmo's fire behaves differently in airborne objects versus grounded structures. They show that electrically isolated structures accumulate charge more effectively in high wind, in contrast to the corona discharge observed in grounded structures.[10][11] ?????? |
|
Re: File /9) Lubrication and cutting oils/107006-1701-Insted-A-Led-1-.pdf uploaded
#file-notice
Here a link for white lead sub
?
Dave? |
|
Bubble Sextant /Octant
Herd few photos of a Bubble Sextant sometimes know as Bubble Octant too. Used main in Aircraft some times on land?
Used atless into 1950’s. This style I do not know how long it was around .?
Note it is just a add mirror and tube level add
?
?
Below in pdf is a manual too.?
?
Dave?
|
|
Re: Hardness tesrters
Sounds great too?
It will work too.?
?
It bouns that makes work to a senceres like you said a mini metal detector and time.?
?
When purchased the first I play around with aluminum
Found about 18"? drop I could read reading of hardness of different aluminum. I had no real use as work in steel and iron. I also did have a way market the tester.?
?
Like your ? idea
Dave?
?
?
On Thu, Mar 6, 2025 at 07:34 AM, Bill in OKC too wrote:
|
|
Re: Hardness tesrters
开云体育Voltage would be pretty low, but I'll bet the current is pretty good.200mm long pipe, not cm. On 06-Mar-25 18:34, Bill in OKC too via
groups.io wrote:
|
|
Re: Hardness tesrters
Should figure out how to measure the induced voltage. Would be a cool addition to the demonstration.? Bill in OKC? William R. Meyers, MSgt, USAF(Ret.) Aphorisms to live by: Good judgement comes from experience. Experience comes from bad judgement.? SEMPER GUMBY! Physics doesn't care about your schedule. The only reason I know anything is because I've done it wrong enough times to START to know better. Expect in one hand, expectorate in the other. See which one gets full first.
On Wednesday, March 5, 2025 at 02:11:43 AM CST, Jerry Durand via groups.io <jdurand@...> wrote:
Any charts for ceramic bearings so you don't need
to worry about magnetism?? BTW, I did a demo of magnetism with non-magnetic materials.? Dropped a strong magnet through 200cm of 10mm copper tube.? Took a while to fall out the other end, something nobody in the room had seen or expected. I did include a wave of a Harry Potter magic wand, just for extra effect. On 05-Mar-25 11:07, davesmith1800
wrote:
Remember
the surface being bounced test needs to clean of oil , any
coating and Degaussing.
This
note is not on drawings
|
|
Re: Hardness tesrters
I know feeling of Harry Potter magic wand and dropping ball.
Back in 1970’s when first purchased it I would be ok for cast iron wheels and if work i would be happy.
I was very surprised how well it worked on everything
?
Dave
?
On Wed, Mar 5, 2025 at 12:11 AM, Jerry Durand wrote:
Any charts for ceramic bearings so you don't need to worry about magnetism?? |
|
Re: Hardness tesrters
开云体育Any charts for ceramic bearings so you don't need to worry about magnetism??BTW, I did a demo of magnetism with non-magnetic materials.? Dropped a strong magnet through 200cm of 10mm copper tube.? Took a while to fall out the other end, something nobody in the room had seen or expected. I did include a wave of a Harry Potter magic wand, just for extra effect. On 05-Mar-25 11:07, davesmith1800
wrote:
|
|
Broken Tap remover
If ever break a tap here a low cost machine.?
?
https://www.aliexpress.us/item/3256807236835449.html?ug_edm_item_id=3256807236835449&pdp_npi=4%40dis%21USD%21%24668.44%21%24244.66%21%21%21%21%21%4021410e8e17409930996665071d56b8%21%21edm%21%21%21&edm_click_module=alg_product_3_5731715720&creative_img_ind=4&edm_log_data=gmod-edm-item-list-three-columns.track-edm-item-list-three-columns-log-link&tracelog=rowan&rowan_id1=aeug_edm_92102_1_en_US_2025-03-03&rowan_msg_id=gunsCOWS_92102_%2443728ba50a6446c5920855ae62c76158&ck=in_edm_other&gatewayAdapt=glo2usa |
davesmith1800
Jerry Durand
Bill in OKC too