Such represents the 'routinely stocked' items available from my local 'bricks and mortar' 'True Value' home center (sans 'special order') -- I own the misunderstanding inasmuch as @Aleph(0) was merely relating my 'report' on the 'materials availability situation' lo these two years...But you are incorrect in saying stainless is only available in fine thread
Succinctly: Said alloy is 'softer' with correspondingly compromised structural properties (specifically rigidity and 'thread life') -- Note also that --quite contrary to the majority of electrical applications-- effects corollary to introduction of small parasitic resistances are negligible Re: the EHT indicator project (owing to the resistance ratios involved) -- Hence the acceptability and, indeed, desirability of steel fasteners...If soldering is involved why not use brass hardware?
Agreed! As you are no doubt aware, 'classic' hardware retail outlets often feature 'specialty hardware' (in small chests of drawers along the fastener aisle) -- While some may balk at the 'price structure' of said items - I would argue that such is more than compensated by the products' ready availability!While places like Home Depot or Lowes are much larger than an Ace Hardware, they former don't have the selection of fasteners that an Ace or maybe a True Value hardware has
We yet have them 'round here (N.E. MN and W. WI) - And 'Hardware Hank' too! Surprisingly, 'Mills Fleet Farm' (being, as they are, rather 'big boxish') likewise carries specialty hardware...Ace or maybe a True Value hardware has, though I haven't been in a True Value for years.
Ribs fashioned of PVC, Acrylic, Polycarbonate and, curiously, polyimides and PVDF (tested to 1 cm thickness) rapidly present with marked porous degradation (up to and including full thickness perforation and crumbling) owing to a process perhaps best --but in any event adequately-- described as 'pyrolysis incited electrolysis/chemolysis' secondary to corona... --- Of the substances tested only (cured) silicone adhesive, PTFE, glasses, fused silica and mica showed no detectable degradation following Ca. 100 hours (automated) exposure to 80kV DC (resistor/wax 'friendly' duty cycle observed!) --- Please don't ask which microcontroller platform I employed Re: automation of the tests -- it's just... too... Um... -- Oh! Best not to dwell upon it --- Laziness is a lamentable vice -- hypocrisy is much worse!Next question(s). Why use Teflon for the 'fault path ribs'? If PVC is good enough for the rest of the tower, why isn't it good enough for the ribs?
Although the PTFE ribs do not, themselves, degrade -- they nonetheless form a discontinuity with the highly 'corona vulnerable' PVC tube -- Hence measures must be taken is degradation of said structure to be inhibited-- Silicone adhesive represents a viable solution for two reasons:Also don't understand the use of silicone glue to hold things together.
'Fraid we'll have to 'agree to disagree' on that particular 'note'--- The way I learned 'rithmetic:As far as "rational notation" over "conventional notation"
But then these tutorials/projects are intended as 'scientific' exercises -- as opposed to 'recipes' and/or the 'fringe science' and 'hocus-pocus' having veritably lain siege to much of the (amateur) online EHT (and related topic) community...using medical and scientific terms for mechanical things,
Agreed! But then you forget (or perhaps we neglected to declare?) that (inasmuch as such would be all of unduly burdensome to the reader and contrary to the goals of this effort) none of our projects require out-sourcing of fabrication (beyond mere purchase of inexpensive, commonly available, ready made, 'raw materials')! -- Moreover, our projects are so conceived that only 'standard' tools are required! Whether for direct application to a project or for fabrication of specialized instruments required for operation/construction thereof (e.g. construction of the {perhaps $200 all told} EHT indicator -- as opposed to requiring the reader's purchase of a $60k 'Keithley' or even a $5k radiography 'voltage divider')...if you or any one were to take any of this somewhere to a machine shop that wasn't tied to a university they wouldn't have a clue to what you wanted. I know we've had this conversation before but it's just how things are.
@shortbus I apologize that, having reread our recent posts, I'm uncertain as to the 'specifics' of your reference? -- Is your comment with regard, perhaps, to our our use of 'costa' vs. rib? and/or 'fasteners' vs. 'nuts and bolts'? --- am I missing something? -- If not - methinks you underestimate hardware sales associates!?using medical and scientific terms for mechanical things,
As per your own observation, the matter is complected by too many contingencies to admit of a straight-forward mathematical solution --- While empirical observation (i.e. experimentation) with various insulating materials employed as fault path extension barriers applied to DC systems up to 800kV tends to suggest that optimal intercostal length ≈ (radius of the largest rib)/2 (where said rib is positioned nearest the 'electrically elevated' terminal) I have, as of yet, neither given said observation careful consideration nor hypothesized a theoretic basis therefor --- But to directly respond to your question:HP since I TOTALLY know people will be wondering and just for my curiosity how do you calculate optimal intercostal distance? So I get that if ribs are too close they'll basally act as only one. So arc would just bypass intercostal space jumping from edge of one rib to edge of other! Also being too far apart allows steep enough gradient to set up corona possibly initiating arc! So o/c in perfect world it's basically just normalizing from interval of convergence but in REAL world with unrestricted, non-ideal gas (by which I mean air) as _part_ of insulator it's way more complected than that! So I'm basically asking is there just like _rule of thumb_?
Maybe you can get some construction tips from this:
---Emphasis Added---"These [single phase] transformers feed into a transmission system at a voltage level of 11,00kV Direct Current"
As unlikely as it seems, HVDC links are used because in some ways they offer higher efficiencies. In the US, there is a major HVDC link along California. There are several schemes for this, which are laid out here: https://circuitglobe.com/different-types-hvdc-links.html---Emphasis Added---
What's wrong with this picture? -- Postterm April fools joke? 'Impaired' narrator? --- I dunno...
Perhaps time variant DC and a special non-saturable (insatiable?) core are implied? -- Possible? Of course! Still.. I doubt such is the case - Even as I doubt the costs of R&Ding the pictured apparatus could be held to anywhere remotely approaching the vicinity of a mere $2M (as claimed)
Very best regards
HP
Yes, Indeed! I'm familiar with DC transmission lines! --- My dubiety owed to the notion of (ostensibly magnetic) 'DC transformers' and to the concept of 'phase' Re: DC phenomena -- Of course 'DC' needn't mean 'non time variant' - Still...HVDC links are used because in some ways they offer higher efficiencies.
---Emphasis Added---The strange English that made it seem as though the cost was ~2 million dollars really intended to say that it was “double digit millions” to develop. The native language of the narrator is German, and almost certainly the writer as well if not the same person.
Or indeed a 'classic' 40kV 'high voltage' probe!I must say, it is quite an engineering feat all around, and I wouldn’t want to test if it was live with the age old method of using the tongue, à la 9V batteries.
Ah, I see. I just assumed they were referring to the input to the rectifier from the generating plant so I didn't catch it as a question. I suppose that's because it wasn't a technical presentation but a marketing one, and I have long since stopped expecting technical accuracy from marketing material, particularly aimed at "higher" decision makers—though I am pleasantly surprised when I find it.Yes, Indeed! I'm familiar with DC transmission lines! --- My dubiety owed to the notion of (ostensibly magnetic) 'DC transformers' and to the concept of 'phase' Re: DC phenomena -- Of course 'DC' needn't mean 'non time variant' - Still...
That is the reason most blue prints don't use fractions as such. Outside of wood working. Instead of 1+3/4 they would say 1.75. And I can't see anyone doing something scientific using common fractions. The 1/4- 20 is a thread description not meant as a fraction.'Fraid we'll have to 'agree to disagree' on that particular 'note'--- The way I learned 'rithmetic:
AB=A*B (as opposed to A+B) ---- Similarly: 1¾ = 1*¾ = ¾ (as opposed to 1+¾) --- Please note that I do not dispute your assertion that 'convention' dictates (Re: rational notation) that 'N p/q' = 'N + p/q' --- My stance is, rather, a reflection of my extreme distaste for said notation which being far too strong to permit my use (and, hence, tacit support) of same! ---- Then too 1+¾ is utterly without ambiguity!
Shortbus I basically agree with what you are saying! So _common fractions_ (by which I mean _rational fractions_ which is important to disclaim because being nitpicky technical about it expansions are _fractions_ too) are totally essential in math and ABSTRACT physical science and definitely anywhere fractional expression contains variables or functions! Also since it's totally more intuitive, it's common practice in math to leave fractions with integer component in _improper_ format! So 1¾ is written as just 7/4That is the reason most blue prints don't use fractions as such. Outside of wood working. Instead of 1+3/4 they would say 1.75. And I can't see anyone doing something scientific using common fractions.
Shortbus it's vry important for you to understand that we TOTALLY value your input! And so totally hope you keep it coming! So if it seems like we don't need as much advice on EHT meter project it's just that it's basically completed like 2 years ago so most of the _bugs_ are already squished! And @shortbus YOU definitely squished a HUGE _bug_ showing us how to mount meter inside box! So where we're at now with EHT meter project is basically showing them how to put it together plus providing info (like formulae for people who can't find same resistor values we're using and like that). But if you see anything that looks like possible opportunity for improvement or even just making it easier for builders including even how we're describing things (like with bolt pitch) please don't be afraid to comment! Cuz now with CDT basically _fired_ (except for @theodoravain who isn't very active on here and @Jazz2C who's basically on _involuntary leave of absence_ from tutorials) it's basically just HP and me plus all the help we can get from very kind REGISTERED AAC members! Like you and @cmartinez @The Electrician @Yaakov (and including some other AAC members too) who even though we don't know any of you personally you've been way more help than CDT team ever was!So then to my real question, you don't want any ideas on how to position the Teflon used on the fault path ribs?
HP I say HUGE THANK YOU! Now being honest I thought you prolly couldn't stay away after like 4 years _investment_ of your time here but it's definitely a huge relief seeing you say u plan to return!Although my 'recovery' from exasperation corollary to certain 'online annoyances' (Spec: non-registering developers and especially @Jazz2C's recent 'faux pas' elsewhere on these fora) is nearly complete -- I apologize that my participation here will be rather limited prior to mid/late May (i.e. following 'Dayton') --- In the meantime @Aleph(0) and (one can but hope) @theodoravain will be available to respond to questions/comments -- thanks for understanding!
So here's for people who don't understand how corona (which feels just warm) can heat something enough to make it start breaking down into other compounds:Ribs fashioned of PVC, Acrylic, Polycarbonate and, curiously, polyimides and PVDF (tested to 1 cm thickness) rapidly present with marked porous degradation (up to and including full thickness perforation and crumbling) owing to a process perhaps best --but in any event adequately-- described as 'pyrolysis incited electrolysis/chemolysis' secondary to corona...
Shortbus I'm sorry it seems like that to you because that's not case at all! So only major disagreements HP and I have are about where and when to use quantitative vs. qualitative approach cuz qualitative explanations can seem like _dumb-down_ but being strictly quantitative early in series or in _basic_ discussion can scare people off who just need a little time to get like _acclimated_ to the math! So anyhow you can see how _touchy_ subject is by just looking on how HP and I have like _changed sides_ on that more than once since start of tutorials!Aleph, I get mixed messages from you and HP on my input. One seems to welcome it and the other doesn't seem to want it.
So being 100% clear: Short answer from both of us is: _We don't need advice on design of towers because we totally worked that out like two years ago and present design has stood _test of time!_you don't want any ideas on how to position the Teflon used on the fault path ribs?
LOL! I'm bound to remark that reflection upon said 'process' places me in mind of FB Long's 'Hounds of Tindalos' - and who will deny that failure of same is with the lamentable fate of Halpin Chalmers but upon the towers?!So next thing we tried was _dressing-out_ discontinuity at rib/tube junction with epoxy which helped but since it's not geometrically possible to totally _shift_ discontinuity to rib...
FWIW Our original plan (once having quite decided to implement the tower bodies via PVC tubing) was to cut PVC rings/spacers having inside diameters marginally larger than the outside diameter of the tower tubing such that the ribs might be rigidly 'clamped' between same -- such would have produced a 'rock solid' assembly but at the cost of further discontinuities -- Happily, electronic grade silicone bonds quite well to PVC -- Hence our development of the following technique (each rib):But my Idea is a way to make the positioning and anchoring of the 'ribs' stronger and more easily done by using the same materials
Inasmuch as the 'Mini-Fed' wells are 'outside' the poles - corona (although present) in not an issue -- Hence, instead of silicone, they (the CPVC Wells) are secured to the PVC end-caps via 'high temp' acrylic adhesive --- Although I've not attempted it, I suspect the PVC and/or CPVC would break prior to separation of the bond! -- For all its 'agro' acrylic is surprisingly 'tough stuff'The same would be where the "fed" connector joins the tower.
I am familiar with the product to which you refer -- Indeed is is yet available as GC 10-4702 - A useful compound indeed! --- Unfortunately it is inapplicable to the presently discussed application for reasons similar to those noted by @Aleph(0) (Re: silicone) quoted immediately below:On another similar note, did you try painting the PVC parts with the old fashion 'corona dope' that was used back when CRT TV repair was still done? I think it is or was still available.
Stated otherwise --- 'layering' of 'atmospherically-immersed' solid insulation is --to the extent possible-- best avoided above Ca. 45kV --- Nor is it that the "rules change' -- merely that what is negligible at 35kV is often highly pronounced at 60kV -- said 'criticality' being prominent among the reasons 'high voltage' equipment is generally 'potted' in conductive containers...coating whole PVC tube with silicone won't work at all cuz of creating interface discontinuities and so high voltage antinodes causing _walking_ gradient patterns all along tower! So for people saying _that doesn't make since for DC circuit_ I say please remember corona is type of _disruptive discharge_ and so time varying in nature which gives it properties of AC even if it doesn't change polarity! That's also why _DC_ arc like lightning (which is also example of disruptive discharge) can cause AC phenomena (like standing waves) too!
What you tried is very similar to what my idea is. But instead of trying to find a tube that will work for the spacers, I was going to suggest using PVC "unions" some times called "couplings". They are made to fit over the original pipe , they have a slight internal rib to center two pipes when using in their normal job, but that is easy to take out with an Exacto knife or a Dremel tool.FWIW Our original plan (once having quite decided to implement the tower bodies via PVC tubing) was to cut PVC rings/spacers having inside diameters marginally larger than the outside diameter of the tower tubing such that the ribs might be rigidly 'clamped' between same -- such would have produced a 'rock solid' assembly but at the cost of further discontinuities -- Happily, electronic grade silicone bonds quite well to PVC -- Hence our development of the following technique
My suggestion for the Mini Fed connection is to use one of the 'unions' mentioned above on the end of the tower. Then using a PVC reducer fitting inside the open end of that 'union'. This will make the fed connection much less prone to getting broken off or giving another radial joint to worry about. The reducers are available to go from the 1" diameter of the tower down to as small as 1/2"(0.5") PVC pipe size.Inasmuch as the 'Mini-Fed' wells are 'outside' the poles - corona (although present) in not an issue -- Hence, instead of silicone, they (the CPVC Wells) are secured to the PVC end-caps via 'high temp' acrylic adhesive --- Although I've not attempted it, I suspect the PVC and/or CPVC would break prior to separation of the bond! -- For all its 'agro' acrylic is surprisingly 'tough stuff
yeap ... CPVC's dimensions are made to same standards as old copper tubing, while PVC's are of the "schedule" typeIt may have been mentioned before but if not, you are aware that your CPVC mini fed connector tube doesn't fit into PVC fittings. The two different pipe materials aren't compatible so they made the sizes so they couldn't be interchanged in common use.
FWIW My (failed) approach entailed cutting several snug-fitting PVC 'washers' from 3/16" flat stock, thence placing one such 'washer' above the upper rib, another below the lower rib (having first 'stacked' several of same between said ribs) -- with predictably lamentable resultsWhat you tried is very similar to what my idea is. But instead of trying to find a tube that will work for the spacers, I was going to suggest using PVC "unions" some times called "couplings". They are made to fit over the original pipe , they have a slight internal rib to center two pipes when using in their normal job, but that is easy to take out with an Exacto knife or a Dremel tool.
you are aware that your CPVC mini fed connector tube doesn't fit into PVC fittings. The two different pipe materials aren't compatible so they made the sizes so they couldn't be interchanged in common use.
yeap ... CPVC's dimensions are made to same standards as old copper tubing, while PVC's are of the "schedule" type
A union has the same exact inside diameter as the end cap, within manufacturing tolerances, since they both have to fit the same pipe. The union is also two end caps long and can be cut to any length needed, or one could be used instead of two for a longer separation of the ribs. to my mind easier than sawing the end off of a cap. There is usually a small radius in the bottom of a cap also.That said -- Instead of a union, it seems 'snugger' fitting sleeves might be fashioned of PVC end-caps via removal of their end-closures --- Thoughts?
While I've never had much luck getting teflon tape to stay in place other that on a thread, and even that only after the first wrap, there are such things as teflon "O" rings. They would last much longer than the tape, and a groove could be made in the outside of the mini fed connector by putting it in a drill chuck and holding a file against it while it was spinning.As an aside - Re: the CPVC plug and well -- Inasmuch as a plasma-tight seal is required (and unavailable via most polymers) we snugly _reach the sides_ of the well via formation of 'alignment ribs' upon the 'mini-fed' plugs (via turns of PTFE 'thread tape') as illustrated below... -- In addition to establishment of a far superior 'seal', said arrangement is readily maintained via addition and/or replacement of PTFE 'tape' as required
The problem with solid teflon o-rings, is that it's a material with very poor elastic properties. So here's another alternative: teflon-coated buna-n (an excellent elastomer) o-rings.While I've never had much luck getting teflon tape to stay in place other that on a thread, and even that only after the first wrap, there are such things as teflon "O" rings. They would last much longer than the tape, and a groove could be mad in the outside of the mini fed connector by putting it in a drill chuck and holding a file against it while it was spinning.
Are you saying that the plasma will travel up through the gap in an unglued pipe to fitting joint? That is hard to believe. There is only about 0.001" difference between the two diameters of that joint, ~0.0005 per side. And over a 1" length, with a direct connection to the internal circuit of the meter.
Embarrassingly, it seems 'off-line life' has -once again- made 'liars' of us -- That said, I can imagine no scenario preventing either of us returning to regular participation next week (i.e. that of Mon May 13, 2019).Please be advised that I will be absent from these fora prior Tuesday/early Wednesday (Off-line 'life' again) -- @Aleph(0) expects to resume participation here no later than early Monday...
The 'Trick', as it were, is in winding the first several turns with a degree of tautness sufficient to achieve firm constrictive tenure to the CPVC all the while avoiding undue distortion of the 'tape'...While I've never had much luck getting teflon tape to stay in place other that on a thread, and even that only after the first wrap
there are such things as teflon "O" rings. They would last much longer than the tape
While O-rings and their ilk would indeed prove more durable -- PTFE film (i.e. 'pipe thread tape') is a better choice - given that:The problem with solid teflon o-rings, is that it's a material with very poor elastic properties. So here's another alternative: teflon-coated buna-n (an excellent elastomer) o-rings.
Re: the conditions under discussion -- Ion exchange becomes detectable (sans instrumentation) at channel major-axes > 500pm (picometers) and unacceptable at major axes > 650pm (Note that 0.001" ≈ 25.4 million picometers or ≈ 39 thousand times the maximum acceptable pore-channel major axis [650pm]). ---- To understand this - you need merely entertain the perspective that 'plasma' is as much a process as a 'substance'Are you saying that the plasma will travel up through the gap in an unglued pipe to fitting joint? That is hard to believe. There is only about 0.001" difference between the two diameters of that joint