@shortbus and anyone who cares -- Below is the (too) long awaited LOPT disassembly discussion.

Please accept my sincere apologies for the cursory, frequently shamefully informal 'tone' of the following (my time has not been my own as of late - excuses, excuses...)

All questions, comments and requests for clarification welcome! --- Please be advised, however, that while I may be unavailable for a few days, @Aleph(0) will be 'on hand' (granting the continued 'march' of her 'necroambulant' VPN)

So... With no further ado...


LOPT Disassembly Discussion (27 Nov 2017)

Notes:
1) The terms 'core' and 'form' are used interchangeably (and may be regarded as synonymous) for the purposes of this discussion.

2) For the reader's convenience, illustrations are both 'contextually linked' and attached as full-size images at the bottom of this post. For best results please return from linked images via your browser's 'back arrow' (⇐) 'button'...

3) The illustrations represent LOPTs and constituent components typical of the desired style but not necessarily from the same device.

LOPT Construction:
-As a 'point of reference' an unmodified LOPT of the desired 'form factor' is presented in illustration #1

-Illustration #2 shows the device following removal of the external (radial) auxiliary windings and clamping/mounting hardware (save for the frame ligature) -- Please regard this (sans the ligature) as the 'initial state' of the device prior to disassembly...

-Please see illustrations Nos. Three, Four, Five and Eight for definitions/depiction of terms and references.


The principal difficulty: Liability to core breakage during LOPT disassembly.
Ferrite consists of a rather brittle sintered ceramic possessed of only moderate strength - Indeed the tensile strength of the 'grade' employed in the devices under discussion only marginally exceeds that of (graphic) 'chalk sticks' of similar cross section.

While the lower core joint is directly accessible following destructive removal of the (inutile) external auxiliary windings (whereupon the lower gap adhesive may readily be 'defeated' via direct heating or application of keytone solvents) direct access to the upper joint is not possible owing to its envelopment by the EHT winding assembly.

The Desired Solution: Discovery of a 'pedagogically acceptable', 'novice friendly' method of upper core joint separation sans undue liability to damage to or degradation of the core or EHT winding proper.


A Summary of unsatisfactory methods (i.e. what we've tried):

Present (miserably failed) technique:

Step 1) Clear the lower joint gap of adhesive via steeping of the exposed lower core leg in a keytone solvent followed by mechanical removal of the degraded adhesive and gap spacer.

Potential difficulties with step #1:
A> Degradation of EHT assembly insulation and/or cladding secondary to keytone vapour/condensate exposure...

Step 2) Following removal of the wooden shims intervening the core sleeve and upper core leg, alternately play hot air upon each core rail distal to the EHT winding assembly such that temperatures sufficient to adequately soften the adhesive are attained at the upper core leg and joint (via thermal conduction in the ferrite) -- followed by 'working' the core pieces free of the adhesive via development of alternating torques coaxial to the upper form leg through manual application of simultaneous, appropriately directed 'differential' forces to each core rail.

Potential difficulties with step #2:
A> Although damage to the coaxial auxiliary windings (please see illustration #8) is of no consequence - the EHT winding is easily damaged via misdirected and/or otherwise 'stray' hot air...

B> Overheating of the core may result in a permanent shift of the ferrite's magnetic properties.

C> Uneven heating of the core may result in explosive stress fracturing..

D> It has been our observation that, for many (I daresay most) individuals, successful application of adequate --all the while non-excessive-- torque represents an experience-garnered skill... -- Please note that this is far and away the leading 'mode' of LOPT damage incurred in the course of optimization...


Other methods 'explored' and found to be unsatisfactory or otherwise deemed unacceptable:

1) Rapid, even heating of the core via 'induction' techniques.

--Rationale for rejection--
-While this method has proven to effectively and consistently 'release' the core pieces (within two minutes) sans significant heating of the EHT winding or overheating of the core -- it is, sadly, inadmissible (Re: inclusion in our Tutorial) for the 'disjuncture' of tuition necessarily attending early discussion of power oscillator circuits...

2) Removal of the coaxial Aux windings 'in situ' so as to abrogate core to sleeve adhesion and provide direct access to the upper core joint.

--Rationale for rejection--
-High liability to inadvertent damage to central EHT winding turns.
-Liability to severance/breakage of the EHT return.
-Value of access to the upper core joint (thus obtained) questionable owing to continued proximity of the (readily damaged) EHT winding.

-Method deemed more 'failure prone' than present (unsatisfactory) technique.


3) Ultrasonic delamination of the adhesive-ferrite interfaces.

--Rationale for rejection--
-Variable results.
-Unduly burdensome requirement of 'special' tools/equipment.

4) Protracted (hours to days) application of traction (via spring tension) to core pieces in a modestly heated environment (Ca. 100°C)

--Rationale for rejection--
-Burdensome requirement of arduous, tedious and 'critical' construction of 'traction apparatus'.
-Liability to core breakage secondary to (necessarily) 'uneven' yielding of adhesive.
-Liability to insulation/cladding degradation secondary to protracted exposure to elevated temperatures.

5) Destructive salvage of two similar LOPTs for production of each optimized unit (i.e. salvage of the winding via destruction of the core of one unit and vise versa).

--Rationale for rejection--
-Maintenance of minimum allowable winding periphery to core clearance requires very similar source LOPT geometries.

-Wasteful!


Potentially useful information
1) Inasmuch as the coaxial auxiliary windings will be discarded, damage to same is of no consequence.

Appreciation of the coaxial auxiliary windings' position within the EHT winding assembly may be gained via study of the following linked images:

Illustration #8 (Unmodified EHT winding Assembly) - Note that all features central to and including the auxiliary shell will be discarded in the course of modification...

Illustration #9 (EHT winding assembly following removal of all auxiliary winding components except the auxiliary shell) - EHT return lead indicated by pen.

Illustration #10 (EHT winding assembly following removal of all auxiliary winding components) - EHT return lead indicated by pen.

2) The 'stock' reluctance gap spacers will not be reused and are, hence, 'expendable'.

3) Acceptable techniques will apply equally to cores defining cylindrical and polygonal cross-sections...

/////////////////////////////////////////////////////////////


Illustration #1: Typical AC LOPT

Illustration #2: LOPT assembly following removal of external aux windings and frame

Illustration #3: 'Exploded' view of magnetic LOPT assembly components (sans external Aux windings)

Illustration #4 Form/Core detail

Illustration #5: Form piece detail

Illustration #6: Detail of lower core joint prior to removal of adhesive

Illustration #7: Sleeve to core adhesive/shims

Illustration #8: EHT winding assembly prior to removal of coaxial winding

Illustration #9: EHT winding following removal of coaxial Aux windings but prior to removal of aux shell

Illustration #10: EHT winding following removal of coaxial aux windings and aux shell

Dimensional drawing of lopt assembly following removal of external aux windings and frame (Drawing courtesy of AAC member ' @shortbus ')

 

Please accept my sincere apologies for the cursory, frequently shamefully informal 'tone' of the following (my time has not been my own as of late - excuses, excuses...)

To my and many others who have expressed their opinions, the "informal" tone would be a welcome not "shameful" way to go in this. Why, oh why, should someone need to have a dictionary and thesaurus at arms reach to do this? You seem to forget your not talking to a 'peer' audience but a general audience. I know we have argued about this before but it is just my opinion, along with many others.

B> Overheating of the core may result in a permanent shift of the ferrite's magnetic properties.

Ferrite consists of a rather brittle sintered ceramic

Those two statements contradict each other! The amount of heat needed to stinter the core when it is made would burn the whole winding and encapsulation material to nothing. Any heat needed to take this assembly apart will not change the magnetic properties,as it comes nowhere near the currie point of the core. The heat resistance of the wire insulation is the limit of heat that can/should be of prime importance in this, not the core.

Step 1) Clear the lower joint gap of adhesive via steeping of the exposed lower core leg in a keytone solvent followed by mechanical removal of the degraded adhesive and gap spacer.

While I don't have a back round that let's me give meaningful incite to the chemicals that degrade Epoxy and not magnet wire insulation, maybe you or Aleph can choose one from this list. One that isn't quite as volatile as acetone or MEK. Having worked with both of those vapor transfer is/would be a probable for the windings that you want to save. https://www.engineeringtoolbox.com/chemical-resistance-epoxy-d_786.html

I would have to think that the Epoxy used in this application was a "one part" Epoxy. I say this because of the fact these are automation built items. The use of two part Epoxy would have been a problem to the automation before the adoption "mixing tube" dispensers. But if built after that point in time maybe it is two part, don't know when the LOPT was built. https://www.threebond.co.jp/en/technical/seminar/epoxy.html

Still waiting for the go ahead to post my latest ideas on the disassembly.

 

Hey @shortbus! -- Thanks for your reply!

To my and many others who have expressed their opinions, the "informal" tone would be a welcome not "shameful" way to go in this. Why, oh why, should someone need to have a dictionary and thesaurus at arms reach to do this?

And I maintain that formality is nothing to do with vocabulary, socioeconomic class, culture or peer groups in general - but, rather, courtesy to the audience! -- As I see it, condescension/'talking down' (i.e. assumption of the reader's/listener's ignorance) is always wrong! -- Whereas recourse to 'colloquialism' or otherwise casual delivery is dubiously applied to instruction targeting a culturally diverse audience... FWIW (Re: the 'Alpha Testing' program) we've received majority-positive feedback as regards tone, delivery and (most importantly) readability/intelligibility... --- I wish I could say the same for ease of (uneventful) LOPT disassembly! -- But then that's the purpose of this discussion!

Those two statements contradict each other! The amount of heat needed to stinter the core when it is made would burn the whole winding and encapsulation material to nothing.

I apologize that I failed to describe the manufacturing process (and, hence, special 'thermal liability') of ferrites...

Any heat needed to take this assembly apart will not change the magnetic properties,as it comes nowhere near the currie point of the core.

--Emphasis added--

As you will see, Tc is not the issue...

Following formation (by sintering via brief application of high temperatures and compression in an inert atmosphere) ferrite forms are 'heat treated' in a 'reducing' atmosphere pending attainment of the desired 'crystal chemistry' (which being determined by duration of treatment or, in the case of high quality production, loading/coupling of the induction heater)... While properly 'seasoned' 'inductor grade' ferrite exhibits a relatively low degree of coercivity, 'over-seasoning' (including post-production overheating) tends to 'harden' (i.e. permanently increase the coercivity of) same with, of course, attendant undesirable shifts in volume resistivity, hystresis and corollary properties thereof. -- Stated otherwise; 'hardened' ferrite exhibits many of the undesirable electrical and magnetic properties experienced with metallic cores...

Although the lower temperature threshold for the described changes (≈ 280°C) is well below the material's Tc (≈ 670°C) such is, of course, higher than than would intentionally be applied to a 'populated' core... That said, as sad experience has shown, a heat gun tends to be a 'weapon of mass destruction' in the hands of a novice

The heat resistance of the wire insulation is the limit of heat that can/should be of prime importance in this, not the core.

FWIW cladding (with the exception of silicone) and bunting materials tend to exhibit greater thermal sensitivity than does 'enamel' insulation...

Thus it seems we are agreed (albeit for different reasons) that temperatures sufficient to 'denature' the core are already too high for the purposes at hand?

Re: Silicone cladding (please note that 'cladding' refers to the 'covering' of the EHT winding tyre):
While silicone is both solvent and (reasonably) heat resistant there is, nonetheless, a 'problem'...
The 'EHT winding' is comprised of a 'spiral' consisting of several hundred turns ('tiers') of bunting carrying perhaps a dozen 'passes' of the conductor (a typical arrangement being 420 turns of bunting carrying 12 'passes' of the conductor abreast for a ≈ 5000 turn coil).

Thus it may be seen that prominently among the cladding's functions is inter-tier insulation at the cortices... Exposure of the EHT winding tyre (and, hence, the cladding) to temps much greater than 120°C --while causing no visible damage or obvious separation from underlying structures-- often results in damage leading to coil failure (manifest as inter-tier flash-over along the winding/cladding boundary) during operation at even modest output EMFs -- FWIW I imagine said failure owes to 'bubbles' and/or delamination of the silicone-to-winding interface secondary to heat-induced 'out-gassing' of the silicone - but such is little more than a 'wild guess'...

While I don't have a back round that let's me give meaningful incite to the chemicals that degrade Epoxy and not magnet wire insulation, maybe you or Aleph can choose one from this list. One that isn't quite as volatile as acetone or MEK. Having worked with both of those vapor transfer is/would be a probable for the windings that you want to save. https://www.engineeringtoolbox.com/chemical-resistance-epoxy-d_786.html

I would have to think that the Epoxy used in this application was a "one part" Epoxy. I say this because of the fact these are automation built items. The use of two part Epoxy would have been a problem to the automation before the adoption "mixing tube" dispensers. But if built after that point in time maybe it is two part, don't know when the LOPT was built. https://www.threebond.co.jp/en/technical/seminar/epoxy.html

Although ketones don't 'attack' silicone 'rubber' cladding -- nylon, polyethylene, polyurethane, polypropylene, polyester, acrylic, etc are quite another matter! -- All of which is to say: if you know of an agent as 'aggressive' to 'epoxies' as keytones but exhibiting short-term compatibility with most other 'common' 'thermoplastics' -- I've a wide open mind!

Still waiting for the go ahead to post my latest ideas on the disassembly.

As far as I'm concerned you had it with this morning's posting of the discussion (i.e. Post #1363) Inasmuch as I've seconded @Aleph(0) to management of this discussion (pending my return to a less demanding 'off-line schedule' {in a few days}) you may wish to check with her (I expect she'll 'look in' early Tue AM)...

Many sincere thanks!
HP

 

While properly 'seasoned' 'inductor grade' ferrite exhibits a relatively low degree of coercivity, 'over-seasoning' (including post-production overheating) tends to 'harden' (i.e. permanently increase the coercivity of) same with, of course, attendant undesirable shifts in volume resistivity, hystresis and corollary properties thereof. -- Stated otherwise; 'hardened' ferrite exhibits many of the undesirable electrical and magnetic properties experienced with metallic cores...

HP ur exactly right except it's more complicated than that in air cuz of redox reactions at surface with not just O2 but N2 also!

Although the lower temperature threshold for the described changes (≈ 280°C) is well below the material's Tc (≈ 670°C)

HP I say u could prolly get away with like 300C for vry short time but you'd have hot spots and anyhow it would cook through aux 2 eht winding too fast! But I say it's good margin for hotspots for target temp of like 250C

if you know of an agent as 'aggressive' to 'epoxies' as keytones but exhibiting short-term compatibility with most other 'common' 'thermoplastics' -- I've a wide open mind!

HP I say ur totally dreaming! Anything that effective on epoxy will totally dissolve other thermoplastic polymers! Anyhow like I said b4 vapor isn't problem cuz quasi-aprotic and just aprotic solvents depend on capillary action at molecular level which requires liquid phase! So when it looks like vapor galled and softened surface it's really action of microscopic droplets! So all u need 2 do is just soak lower gap in acetone under hood or outdoors with fan blowing warm air over eht tire 2 prevent condensation!

So anyhow like u said REAL problem is how 2 deal with upper joint!

Still waiting for the go ahead to post my latest ideas on the disassembly.

As far as I'm concerned you had it with this morning's posting of the discussion (i.e. Post #1363) Inasmuch as I've seconded @Aleph(0) to management of this discussion (pending my return to a less demanding 'off-line schedule' {in a few days}) you may wish to check with her

Shortbus I say go ahead whenever ur ready! But plz totally read post 1363 and ask abt anything that's not clear first! So that way we won't need 2 revisit totally trodden ground! Shortbus now I'm saying if u think we ruled something out in _explored methods_ section that u think has merit that's ok too as long as u have new approach 2 rejected method! So only _explored_ method that's totally off table is _induction heating_ cuz it works perfectly but that's not point! We can't use it cuz it would mean putting electronic driver concepts in handiwork chapter

 

HP when u removed old post from public view u forgot to give me access rights so plz fix that asap! Tnx!

 

Although ketones don't 'attack' silicone 'rubber' cladding -- nylon, polyethylene, polyurethane, polypropylene, polyester, acrylic, etc are quite another matter! -- All of which is to say: if you know of an agent as 'aggressive' to 'epoxies' as keytones but exhibiting short-term compatibility with most other 'common' 'thermoplastics' -- I've a wide open mind!

Did you read through the list of chemicals in the link? Look at the ones called out as 'not recommended' those are the ones that may/should be of interest. Due to my total lack of knowledge an experience of chemicals I can't make a determination of what would work or not, that's for the two of you.

I have worked with both acetone and MEK. I know that MEK will dissolve synthetic varnish, because it was used for that at one place I worked. To remove varnish on vacuum metalizing fixtures after the process was done before the fixtures were reused.

 

As for heating to weaken the Epoxy. Why not use either a 'toaster oven' or an 'electric skillet', they can be bought from second hand stores or places like the Salvation Army stores for next to nothing. So you don't need to worry about "contaminating" one that will be used for food preparation.

The reason I suggest them is that they have a thermostat, this will prevent over heating. If 250C is the limit for a short time just keeping the temp at lower than that say around 350F which any of the ovens or skillets are capable of. A lower heat for a longer time will give the Epoxy time to break down without the worry of going over the 'critical' temp.

I have a toaster oven for this purpose in my machine/fabricating shop. To both preheat metal(aluminum) before Tig welding and to temper steel when heat treating it. Also use it to heat up parts before pressing bearings in to things.

 

Now for the core disassembly part.


The first picture shows how to measure for the hole positions in the parts to be made.

The second shows the individual parts to be made. While I show one way of making the screws, out of allthread rod, wing nuts, hex nuts, and lock washers, that is not the only way of doing it. An eye bolt that is long enough and with threads the full length of it's shank would also work. I show the "U" type clip nut because most people won't be able to tap the holes for the screws. It has to be the "U" type clip nut shown, there is another type that is just sheet metal without the thread tower that won't give enough strength or threads for this purpose. All of the things shown in this picture are available at McMaster-Carr, most Ace hardware stores will also carry them, or the ones in my area do.

The third and fourth pictures show the assembly of the whole. In use the angle iron pieces would be clamped to the core as shown. Then the screws would be snugged up against the bottom angle irons and a slight pressure put on the assembly with them. This will then start to pull the two part of the core apart. The angle iron keeps the core from twisting and supports it through the process. After the assembly of this "puller" it's into the oven to bring the whole up to heat. After letting it heat for a while it would be removed from the oven and both puller screws tightened a little more, it may take a few times of the heat and tighten cycle to get the job done. The big thing is making sure both screws are turned to keep the pressure equal on both sides.

This 'puller' is similar to how a gear puller works, it's just a glorified gear puller made to fit the job at hand.

 

If it was me doing this the first thing would be to remove as much of the auxiliary tower above the secondary winding. Not on the wire connection side but on the side with no wire connections. This would get rid of a lot of the wooden 'shims' and probably some of the Epoxy bond that your trying to defeat. This could be done with a fine tooth hacksaw blade to cut through to the core. Not using a hacksaw but just the blade hand held. Cutting close to the "tyre"(tire?) say a 1/8" away from it.

And removing the wood shims could be done using a thin old screw diver, heating the blade with a propane torch and using it to "burn" or char the wood. This would also help to break down the Epoxy. There should be little to no chance of the whole thing catching on fire doing this, the surrounding material will act as a heat sink.

 

Anything that effective on epoxy will totally dissolve other thermoplastic polymers!

Not necessarily, check this thread.

 

Shortbux Tnx!

As for heating to weaken the Epoxy. Why not use either a 'toaster oven' or an 'electric skillet',

Shortbus cuz either of those would heat winding too which has 2b be avoided! Cuz temps way below damaging insulation on wire can still delaminate potting from winding spiral! So heat reflux from core isn't enough 2 damage HV winding as long as it doesn't have time 2 migrate through auxiliary windings but HV winding shouldn't be heated to more than like 60C (150F) and even then not 4 too long!

The reason I suggest them is that they have a thermostat, this will prevent over heating. If 250C is the limit for a short time just keeping the temp at lower than that say around 350F

Shortbus that temp is ok for core but even 70C (so like 160F) is pushing it for winding!

So just 2 explain: Coil can safely run hotter than that in operation cuz then inside is hotter than outside so potting doesn't separate from wdg spiral! So max operating temp is like 100C but just 60C if heated from outside to be totally safe!

If it was me doing this the first thing would be to remove as much of the auxiliary tower above the secondary winding.

Shortbus I think u mean just _auxiliary winding_? Cuz tower is just HV output connection on outside of tire? So plz look on pics again and let us know if u need more info or more pics

This would get rid of a lot of the wooden 'shims' and probably some of the Epoxy bond that your trying to defeat. This could be done with a fine tooth hacksaw blade to cut through to the core. Not using a hacksaw but just the blade hand held. Cutting close to the "tyre"(tire?) say a 1/8" away from it.

Shortbus like HP explained in presentation we already tried that! There are just too many problems cuz even with HV tire loose and free 2 move end 2 end it's still captive on upper leg so too close 2 gap to be out of harm's way! Removing auxiliary winding actually makes HV winding more vulnerable to hot core cuz of no intervening aux windings for like heat sink and shield! Now for cold cutting I say if someone doesn't have skill to twist core apart w/o breaking it no way do they have skill like surgeon or jeweler to cut glue from gap at such super close quarters!

So anyhow HP explained that we tried that (in quote from presentation below) so Shortbus plz carefully read WHOLE presentation cuz I don't like 2 see you waste your time and efforts with _been there done that_ ideas

2) Removal of the coaxial Aux windings 'in situ' so as to abrogate core to sleeve adhesion and provide direct access to the upper core joint.

--Rationale for rejection--
-High liability to inadvertent damage to central EHT winding turns.
-Liability to severance/breakage of the EHT return.
-Value of access to the upper core joint (thus obtained) questionable owing to continued proximity of the (readily damaged) EHT winding.
-Method deemed more 'failure prone' than present (unsatisfactory) technique.

After the assembly of this "puller" it's into the oven to bring the whole up to heat. After letting it heat for a while it would be removed from the oven and both puller screws tightened a little more, it may take a few times of the heat and tighten cycle to get the job done. The big thing is making sure both screws are turned to keep the pressure equal on both sides.

Shortbus there's something u don't understand and I think it's our fault Any temp hot enough to safely and quickly release glue is too hot for HV tire! So for example HP tried putting whole flyback under tension by attached spring loaded puller in 100C oven and at that temp it took like six hours for ferrites to creep apart cuz glue is like amorphous solid at that temp! But even 100C is totally destructive 2 potting-winding bond cuz of outside being hotter than inside at first! So I totally like your puller but we need to find way of using it after heating JUST core to like 200C cuz yield tension of 200C epoxy is way less than tensile strength of 200C ferrite!

So anyhow here's quote from presentation where HP explains abt heating FB in oven with spring puller attached

4) Protracted (hours to days) application of traction (via spring tension) to core pieces in a modestly heated environment (Ca. 100°C)

--Rationale for rejection--
-Burdensome requirement of arduous, tedious and 'critical' construction of 'traction apparatus'.
-Liability to core breakage secondary to (necessarily) 'uneven' yielding of adhesive.
-Liability to insulation/cladding degradation secondary to protracted exposure to elevated temperatures.

Shortbus it looks like your puller solves first two objections but third one (heat damage of winding) is still a problem so like I said we just need 2 think of a way of heating just the core then using your puller right away!

I have worked with both acetone and MEK. I know that MEK will dissolve synthetic varnish, because it was used for that at one place I worked.

Shortbus I say ur preaching 2 choir! So I don't doubt acetone and mek can damage insulation and potting! I'm just skeptical that anything harmless 2 insulation will effect epoxy!

Not necessarily, check this thread.

Cmartinez tnx but since I don't have time to properly read 6 page thread right now what I got from skimming is ur suggesting nitrogen hydrides (like NH3 and N2H4)? So I'm saying it might be possible to disintegrate epoxy that way but brittling effect on everything from PE to silicone rtv rubber cuz of replacement reaction is disqualifying factor Cmartinez If I missed something by skimming over important posts plz just tell me or link to posts

 

So just 2 say I prolly won't have chance to be here again b4 weekend and HP won't be back on here until next week so plz don't anybody get wrong impression from _crickets_ cuz we're just busy not conceited

 

Thank you for at leas having a look at my proposal.

Shortbus I think u mean just _auxiliary winding_? Cuz tower is just HV output connection on outside of tire? So plz look on pics again and let us know if u need more info or more pics

I do know what the high tension tower is. What I was calling the auxiliary winding tower, because I didn't know what else to call it, was the tube that surrounds the auxiliary winding, the one going out from each side of the 'tyre'.

Shortbus like HP explained in presentation we already tried that! There are just too many problems cuz even with HV tire loose and free 2 move end 2 end it's still captive on upper leg so too close 2 gap to be out of harm's way! Removing auxiliary winding actually makes HV winding more vulnerable to hot core cuz of no intervening aux windings for like heat sink and shield! Now for cold cutting I say if someone doesn't have skill to twist core apart w/o breaking it no way do they have skill like surgeon or jeweler to cut glue from gap at such super close quarters

Isn't an air gap a better insulator than either plastic or wire?

You mean to say they wouldn't be able to tell the difference between soft (plastic, wood, winding's), and when the blade hit ceramic/ferrite? I can almost guarantee the saw blade would. Even carbide machine tools won't cut ceramic.

So anyhow HP explained that we tried that (in quote from presentation below) so Shortbus plz carefully read WHOLE presentation cuz I don't like 2 see you waste your time and efforts with _been there done that_ ideas

I have read it. But there are so many things on my mind that some times I don't remember details. Especially when many times they are given in a "foreign" tongue to me. I don't speak, academia very well. (don't get your panties in a twist, not trying to get you to dumb it down)

So for example HP tried putting whole flyback under tension by attached spring loaded puller in 100C oven and at that temp it took like six hours for ferrites to creep apart cuz glue is like amorphous solid at that temp!

I can almost guarantee the puller will be more effective than any spring. It also has the added value of strengthening the core during the process of separating it.

 

ur suggesting nitrogen hydrides (like NH3 and N2H4)?

Nope, I'm suggesting you try NMP ...

 

Did some searching last night on how to defeat cured Epoxy. Seems there are somethings sold that are made to do it.

https://www.3m.com/3M/en_US/company...-Adhesive-Remover?N=5002385+3293193731&rt=rud

https://www.esslinger.com/attack-epoxy-resin-and-adhesive-dissolver-solvent-remover-cleaner/

https://www.dynaloy.com/products/dynasolve-185

https://www.dynaloy.com/products/decap

Maybe exposing the area between the core and winding's. Removing the wood shims or at least as much of the shims possible, to create a void , then injecting one of the epoxy removal products with a syringe. Doing it like this would limit the chemical exposure/damage to the rest of the wanted winding encapsulation.

 

Probably a dumb question, or one that's already been addressed. What is the real reason for doing all of the removal of the core? Is it to change the gap distance?

I know me and HP had a pretty heated back and forth on this and don't want to reignite it. But after that discourse I did some online research on what she said. She basically said it was to prevent, 'inter winding capacitance'. Since I didn't understand I looked into it. Unless I am still misunderstanding, inter winding capacitance refers to capacitance between layers in the same winding, not other winding's on the same core. Maybe HP meant, "intra winding capacitance", but that gets no hits in Google.

That said, if the reason for taking the core apart isn't to change the gap, I have another idea. Earlier I suggested sawing or cutting the tube covering the auxiliary winding's. Why not do this close to the 'tyre', and then teasing/picking the offensive, unwanted winding's out from under the 'tyre'? This would leave the 'tyre' unmolested by chemicals or heat. The winding's would the be replaced by the same items(pvc pipe or what ever) like in the original build. The pvc pipe would just need to be split length wise into two parts and inserted into the space, like engine "bearing shells".

 

Hey @shortbus thanks!

I apologize that I haven't time for thorough review your suggestions/posts at this juncture - howbeit I can tell you that some of your suggestions look quite interesting/promising!

But to clarify one of my previous comments...

What is the real reason for doing all of the removal of the core?

Principally: Improvement of winding-to-core insulation via replacement of the unneeded, otherwise troublesome, 'coaxial features' (i.e. Aux shell, windings and sleeve) with insulating material (Spec. 'Acrylic', CPVC, PP, polyolefin, PUR/'Lycra' and electronics-grade RTV) -- Ease of reluctance gap adjustment and preclusion of 'parasitic issues' (arising from the Aux windings) represent 'fringe benefits', as it were...

She basically said it was to prevent, 'inter winding capacitance'

Said comments were with reference to distributed capacitance exhibited by the auxiliary windings and the undesirable effects thereof (e.g. parasitic loading, resonances, coupling, etc...).

Please recall that the re-purposed application electrically 'floats' the EHT winding and operates at significantly higher EMFs and frequencies than anticipated by the original design -- hence the requirement of improved (80kV+) winding-to-core insulation and 'purging of parasites', as it were...

Shortbus -- I implore you! Please thoroughly study the Tutorial {Vol(A) and Vol(B)} -- While I realize it makes for rather 'dry' reading You will discover that it contains the answers to most of your questions

Very best regards and again, many thanks!
HP

PS -- As per my conversation with her this afternoon, you may expect a comprehensive response to your suggestions/comments/questions from @Aleph(0) Sunday or Monday -- FWIW I should have significantly more time by the end of next week...

 

HP when u removed old post from public view u forgot to give me access rights so plz fix that asap! Tnx!

Done!

 

I just started looking at this post and have not read them all so if what I am adding has already been covered I am sorry, but here it goes, my thoughts on using chemicals is that they could absorb into the insolation also which could cause problems, heating has been stated as working but damages the insolation so don't head the insolation, apply the heat to the core directly and do not heat the surrounding air. You would need to be careful not to heat it up too quickly as the thermal shock will cause it to crack. I hope this is helpful.

 

I just started looking at this post and have not read them all so if what I am adding has already been covered I am sorry, but here it goes, my thoughts on using chemicals is that they could absorb into the insolation also which could cause problems, heating has been stated as working but damages the insolation so don't head the insolation, apply the heat to the core directly and do not heat the surrounding air. You would need to be careful not to heat it up too quickly as the thermal shock will cause it to crack. I hope this is helpful.

From the sound of it, you are going to fit right in to this thread.