REVEALED: Metal Membrane Strainer is for Theremin's Great Seal Bug! 

Yes, that is definitely me! Videos about my experiences and the tech of the project will be on my channel soon

I can also churn out synecdoche and metonymy when I'm pushed....

I was tempted to go in with the inch and a quarter drill, but I think that would be pushing it a bit too far

CA glue is a real marvel. Deserves a lot more credit in my opinion. It can work magic if you use it correctly.

@@crabmansteve6844 I first used it in 1970 at high school. It was furiously expensive but the chemistry and metalworking teachers though it was going to be important and that we should know about it. I would like to find some with microspheres, or a way to add microspheres to get a totally consistent glue-line thickness. As with all these things, it's not a new idea. Wax has been used as a workholding glue for metal probably since the era of the Antikythera Mechanism and I've used beeswax from my own beehives in the past to this very purpose. CA needs about 200 C to melt and has the major benefit that it releases cleanly from the hotter side, so a flame on the thin workpiece ensures that there is no glue residue. I use some specific de-bonding fluid to remove any traces, although I think acetone works.

@@MachiningandMicrowaves you should use hot glue. It's not diy without hot glue.

@@MachiningandMicrowaves Acetone is slow against wax, xylenes and carbon tet are better solvents. When I first read decades ago about using cast low melting point metals as a work holding fixture I was very intrigued. I think Woods metal is one of the common ones and all you need is a cavity with a lip, hold your work in while you pour the metal into the cavity. Some alloys can expand at the moment of solidification resulting in no loose fit. Type metal is one such but it will be deprecated these days due to the large lead content, the antimony was responsible for the expansion effect IMMS me.

All good so long as you weren't drinking tea at the time I guess.

Now if only we could persuade her to say "unbranded poker dice game" when parting

...and seat your part with a "knocky knock knock"

That sounds like a cool project, hope to see it on a video sometime!

I saw a video about that and in that case the weight of the foil holder ring was the sole provider of the required tension. The sandwiching ring was then simply put on the top and the screws put through the foil. (Sorry, if my explanation is not that clear, damn language barrier)

You also have to think about selectively sputtering the gold on the mylar foil, so that it is not in electrical contact with the baseplate and holding ring.

@@zsigmondkara Very clear. It must be much simpler with metallised mylar which is pre-stretched BO-PET film and doesn't work-harden, although I guess there must be some exciting issues around the metallisation breaking apart if you over-strain it. I did try copper leaf (like gold leaf and only 0.2 micrometres thick) but even air currents would rip it. I measured the thickness by laying ten leaves on a gauge block then laying another gauge block on top and comparing the overall thickness with the thickness of just the blocks, using my Mahr Millimess and a conparator stand on one of my granite surface tables.

Hmm, gold sputtering... now that's an interesting thought. I have a large Bell jar here in my lab, and some microwave oven magnetrons, but also some solid state 2.5 GHz amplifier boards that can make as much power as a magnetron. Wonder if I could use those to create a plasma sputterer? I know @thethoughtemporium and @AppliedScience have already done similar things, but how cool would it be to have my own PVD/sputtering setup! I've added that to my ever-growing project list.

I am bit over-prone to hyperbole! I checked up and found at least four recent projects of mine had surface-mount HSTTL chips, like 390 decade counters and 7486s

@@MachiningandMicrowaves Everyone does it too in some way. Also, I can't wait to see what you're making these things for.

@@RvnKnight @Machining and Microwaves is secretly a fisherman. 🤫 *He's going to strain the world's tiniest fish out of **_micro-waves._* 😉

@@YodaWhat I do have a large number of Three-Spined Sticklebacks in my pond. They are pretty small.

Just think of all the excellent things that a lathe can produce. If civilisation ends, and you have a lathe, it wouldn't take long to rebuild it.

Is the family name Turner? If so, how could you not?

@@shakarakash Invoking nominative determinism is a time-honoured approach to marital negotiations.

I've only done it on 2.2 mm enamelled transformer wire, using a long bar as a lever, to make replacement elements for a Tonna yagi antenna. You can definitely feel the stuff work-hardening as you pull, but the lever deadens the feedback on just how far you can go. I like the hammer idea.

Slug barriers? I'm intrigued. Got pictures, or a complete description?

Lots of interesting ideas so far, but this is a commercially sensitive job so I'm not able to shed any light on what product these are used with. Interesting ideas include X-rays, burst disks, vacuum sputtering, "some sort of mirror for microwaves", something infra-red, MASERs, vacuum cannons, longwave lasers, plasma generator, pressure gauge and inflammable liquid depth measurement. Fascinating.

That sounds like a Russian bugging device in a carved Eagle.

@@KallePihlajasaari lol winner winner

@@jamesbizs Jep, Neil apologised for removing my more comprehensive comment in his other membrane video and confirmed my guess. I did warn him about this comment as well but it looks like he left it in place.

I've had to retire that effect because of complaints!!

I have a new Newall as well. It's probably using a cpu but it still uses spherosyns.

Heh heh, no comment!

I said same thing..😉

Here I was thinking burst discs for a light-gas-gun. For that I think they use aluminium, so maybe a comparison between the x-ray permeability of copper and aluminium could tell you what’s more likely.

Lots of other metals that can be used in burst disks I guess? I've got this working with brass foil and very thin stainless steel shim now.... Not for any particular reason, obviously. I've got a vacuum pump and a compressor and a cylinder or two of Argon, although that's not light. I do need a launcher to send lines over trees for antenna supports. Hmmmm.

Didn't we already prove that electrons exist?

I've always fancied the idea of building a synchrotron, but a linac would be cool. In related news, I have 120 UHF amplifier pallets capable of 250 watts each. I wonder what they could be for?

@@MachiningandMicrowaves Happy to guide you through the vacuum stuff for building the synchrotron if you'd like! :)

@@Spirit532 where do you think the crossover happens between a Linac and a synchrotron on the hobby scale? Today, the largest synchrotron is way bigger than the smallest linac. If you had to choose, what would you build?

@@Tadesan Synchrotron. *Way* easier to build than a linac.

​@@Tadesan - It depends on how many MeV, GeV, or TeV you need, and what kind of beam particles. Old CRTs were a simple form of LinAc, as are common X-ray sources. I've heard of simple accelerators being driven by 20,000,000 volts (20 megavolts) from Van de Graff generators, which will get electrons up to a very respectable relativistic velocity of 299699.4063 km/s (kilometers per second) = 6.704084786×10^8 mph (miles per hour) = 2.996994063×10^8 m/s (meters per second) = 99.96896129% of c, *only 93 km/s slower than c,* and a _relativistic gamma_ of 40.13902397 *(over 40 times more total energy than rest mass-energy).*

A few decent wrenches make all the difference. I still have my Dad's old Moore and Wright, which is like the baby Staret 91, but it's been in use since 1954 and it's getting a little tired. I also have two baby 91s

Coming soon!

I have a 91B as well.

Where is his Starrett die stock ? The one he used today looked like it came out of a Christmas cracker 😉

My nice die stock was in use with another die and I didn't want to remove it and upset the dimensions. Normally I use a tailstock dieholder. I think that one cost me AT LEAST £7.99. It is truly terrible. I should have blurred out that section to avoid offending everyone's sensibilities!

@@stevewilliams2498 Oddly there isn't, no die holding, only taps. If someone has any ideas why I would like to hear.

It is odd, unless they own Greenfield? Dormer stocks are OK, and maybe Cle-Line? Mine is something ancient, made in Sheffield by blokes with hammers.

Nanny Ogg?

@@MachiningandMicrowaves Half way between her and Ponder Stibbons. Ironically, I look like Lord Vetinari.

@@garbleduser Somewhere I have a photo of Terry Pratchett signing the back of my friend's leather jacket while she bent over in front of him. He just grinned and signed his name... Such a dude.

Chuck spider is made in the US and shipped direct from Edge Technology LLC in Eagle, ID on amazon.com, I just checked using a friend's address in MA and indeed they charge $21.99. I think there is a trick to save money here. If you buy direct from Edge, you can order a spare spider centre set for about $25 and sets of just three parallels of one height for £15, probably plus $$$ postage. www.edgetechnologyproducts.com/replacement-parts/ Perhaps only works for US addresses. Could be worth a look if you can use that trick. Anchorlube is supposed to be very good. I wish I could buy Tapmagic for Aluminum here, but MSC direct don't carry the ally version and nobody else seems to import Tapmagic. I get on OK with a mix of ester-based cutting oil and WD-40, so it's not much of an issue. As for Project Swordfish, yesterday I was in visiting where I met with the good folks from and carried out some detailed tests on the using and now I have a lot of data and have to make a huge pile of modifications before next week when I get to visit at and meet to explain some technical details and processes and things. I'm not helping here, am I ????

I'm trying gluing the membrane to a ring that's larger than the jig so it hangs down around the main body and pre-tensions the membrane so I don't have to hold it.. Not shown in the vid is that there's a step of 0.05 mm on one face and 0.10 on the other, so there's 0.05 clearance where the bolts are and the main pressure is applied on a ring just inside the bolts. The the underside of the ring inner edge has a shallow polished curve that's rather like a parabola so it ensures there's no sharp bend anywhere. It's over the last 5mm or so. Details will be in part 2. Good thought about a tiny amount of grease, although I'm nervous about cleaning it afterwards. I can't use the ultrasonic bath as it makes the membrane go floppy. A very gentle rinse with brake cleaner and acetone is probably the way forward. I'm getting a success rate around 5%, and I only need maybe eight good ones, but that's an awful lot of attempts. The trick with the glue and ring certainly seems to be helping as you rightly say. It's been a whole lot of fun messing around with ways to do this, but I'll be glad when I move on to the next project!

​@@MachiningandMicrowaves Ah, way ahead of me, good stuff! The curiosity is killing me for the reveal but I'm a patient lil guy :)​

@@MachiningandMicrowaves The foil is sounding so thin that I am thinking merely having it glued to a external washer and using the step clamping force without any screw holes would make for a more even holding force and easier removal. Also looking forward to the reveal on the purpose. Lovely machining as always. Perhaps just rubbing the polished tool with a block of PTFE would deposit enough dry lubricant. A grease lubricant might stick more than help.

@@KallePihlajasaari I'm using a drop of very light oil on my fingertip and wiping the curved face with a just a faint smear. That seems to be fine. I've made a new slightly larger piston out of some piece of leaded mild steel and it has taken a very good polish as well. The issue with this foil is that you have to stretch it quite a lot to get it to work-harden. It would be much simpler with stainless steel or even brass foil

My instinct is to use a pressure differential across the membrane to do the stretching bit.

I'm never sure which Loctite would work and release cleanly with heat, but also I expect it would cost twice as much as this high-viscosity CA! I use that black rubbery Loctite 480 and the various thread/stud lock compounds and don't mind paying a premium for the performance. This stuff sets fairly rapidly and holds well. It also lasts a long time once opened, I've been using this pot for four months with no sign of degradation

@@MachiningandMicrowaves Thanks for the reply 😊 I'm going on what I have seen other RU-vid machinists use - normally one of the green studlock/retaining compounds. But, whatever works.....

It sings a bit with long stickout, but the value is excellent when compared with carbide.

It's interesting to see Adam Booth @abom79 getting a lot of rather rude comments after he showed a piece of machining that went wrong. Everyone's suddenly a forensics expert and is convinced he's doing something stupid. The total certainty that some of them have about the root cause of the issue feels like quasi-religious zealotry. I'm happy to see him doing some machining again and interested to see the followup video about diagnosing and fixing the issue.

@@MachiningandMicrowaves which video is that? I love aboms videos, havent caught up much on his content since he moved shop though.

@@robbiestevens1158 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-gEAURyEZcqM.html

Hydraulic would be good, this has a 0.5mm pitch screw, so around 50 tpi, but depending on the material, the difference between "just right" and "scrapped part". There's a gentle curve on the underside of the clamping ring, so the foil doesn't get any particular damage from that part. There's also a 50 micrometre step in one face and a 100 um in the other to help lock the foil in place near the bolts. I started using 3 micrometre leaf, but it's just impossible. It works really well with thicker material up to about 70 micrometres. I need to try stainless steel foil as well. Some more detail in the next episode about the rest of the construction. but the full details of what I'll be using this for has to wait. Commercial confidentiality and suchlike.

Thin foils being drawn are more an art than science.

I used to think it was SO fast. Then in 1977 I made a prototype parity injection device that added bits to a 240 Mbps data stream using ECL chips with microstripline interconnects. That seemed fast at the time. It turned electricity into heat very efficiently.

I like that idea!

Having it pressed against a mould gives me some other ideas, like making vacuum bellows and micropositioners controlled remotely by air or hydraulic pressure....

@@MachiningandMicrowaves I would only do the molding with hydraulic as you don't want the explosive decompression when you inevitably blow up the first few membranes as you tune your proceas, but low pressure pneumatic would certainly be usable for actuators and the like..

@@Flying0Dismount Oooh,I could do a lot of Shorts with loud bangs and slow-mo! Or perhaps not....

Shot peening is certainly a good surface treatment, but a 10 micrometre foil might not survive the abrasion and might be contaminated by the impactors. The key here is to align the crystal domain boundaries using a radial strain, rather than simple work-hardening, I should have made that clearer

I'll put all of the drawings up in Github or some other repository at some point, but I want to make a few presentation-quality gold and silver plated Bugs in display cases for sale first. Ideal gift for the Oligarch Who Has Everything

I would be keen to get one

@@jonathangreenstein919 I think they'll be ready for Christmas at the rate I usually work

I bought several copper leaf packs but they were impossibly fragile, worse than gold leaf and impossible to solder or stretch. Worked well when applied like gold leaf and burnished, but also anything less than 10 micrometres is too thin to work well as an RF conductor at 1GHz. Nothing is ever easy! I wonder what to do with all this copper, rose gold and brass leaf!

@@MachiningandMicrowaves OK. Sorry that you ran into troubles.

@@guytech7310 Oh but I had enormous fun trying, and that's the important bit! That copper leaf is weird stuff, I couldn't get it to move using a fine paintbrush like gold leaf. I bought more from two different suppliers but they were similar

I still have absolutely no idea what I'm doing, but somehow it doesn't seem to matter. So long as nobody confuses me with a proper engineer/scientist/machinist, all is good. I'm just an old computer hacker who messes about with radio and machining and chemistry and maths and physics. I must get a proper camera though, then at least I can have a second angle shot to fill in when I mess up the focus!

RTL chips had almost gone by the time I started messing with electronics, but all of the magazine adverts had great long lists of 74xx devices along with thermionic devices and discretes. Henrys, Bi-Pak and others had small ranges. If you don't mind copyright violations, the worldradiohistory.com site has a scan of the first Practical Wireless magazine I bought with the money from my newspaper delivery round, aged 11. URL ends with /UK/Practical/Wireless/70s/PW-1971-04.pdf or use the search tool for Practical Wireless April 1971. I took my remaining pocket money to John Birkett's shop in Lincoln and bought the parts for that month's Take 20 column, a rain alarm. Two 2N2926Gs, a few other parts and a speaker from an old radio, built on and a bit of Paxolin tagboard and fitted into a pipe tobacco tin. It wasn't Gold Block, more likely Golden Virginia. John Birkett died recently, well into his 90s. The shop is still there.

@@MachiningandMicrowaves Blimey, I built a sound triggered switch with 2N2926. I remember they had a green, red or i think orange possibly yellow to denote the gain. It was from an issue of Practical Electronics that had a photo of a hammer breaking an illuminated light bulb, the sound switch was used to trigger the camera's shutter. Buy pre pak bloody hell that's from a while back. I'll raise you Arrow Electronics !

@@Alan-wu3ry I remember setting up some bottles with bare wires taped to the surface, or just above, setting up two cameras with open shutters in a darkened room while a friend was laying prone on the floor aiming a .22 Webley with a scope. He loaded and aimed, then I flipped the light switch, waited half a second for the incandescent light to fade, opened the camera shutters with a cable release and gave him the command to hit the trigger. When the pellet touched the wires, it fired off a flashgun. I made a stop-frame animation of the pellet from an inch away until it hit the bottle and then a few more frames as the bottle shattered. Couldn't go very long because although we had a trigger delay using a monostable, each shatter pattern was different, even though his aim was spot on. We had some rather difficult conversations with the housemates about why there was glass EVERYWHERE. Ah, the 1970s.

@@MachiningandMicrowaves Top stuff Neil, easy on the HSE 😀

I've tried using a titanium plate and electroforming copper foil on to it then peeling it off, and I have an upcoming project using an aluminium mandrel and using a zincate process then gold plate then electroformed copper and dissolving the aluminium in hot sodium hydroxide, but haven't tried the obvious next step of plating a layer of nickel then silver (or silver then nickel). Last week, I bought a Titanium bar 63 mm diameter by 140 long for a very low price with the idea of making continuous copper foil, but your comment has inspired me to try the B&K method. Any idea when they started using that technique and if there are patents from before 1938 that Termen or others in the Ioffe organisation may have seen?

@@MachiningandMicrowaves Hi, I will check and reply to you question later in the day about the B&K methode. I have a book with the description

Oh, I just noticed you already replied to almost the exact same comment. My bad!

I only posted that reply a minute ago.... Was it LS TTL or HC TTL or the really old plain vanilla 74xx chips you were using?

@@MachiningandMicrowaves I was probably around 10 years old when I started messing around with logic stuff. I remember buying 74HCxx logic chips from the local electronics shop, and desoldering LS stuff from boards I bought at flea markets etc. I don't think that I understood the difference between them at the time. I mixed-and-matched :)

I built a phase-locked 100 MHz ovened crystal osc last year using a 7486 (modern equivalent in an SOT23-5 case). Somewhere i still have a few MECL III chips from a project in 1977.

The clue is in the title I guess, Looks like you spotted the new video about the actual use for my replica Great Seal Bug

At the time I made that video, I was under a non-disclosure agreement because the TV series had not been announced, so I had to be extremely vague about the purpose of the membrane stretcher!

I have a box of 74xx series 5 volt TTL logic chips somewhere in my electronics lab...

@@MachiningandMicrowaves 5 volt TTL is obsolete? when did that happen? (I feel so old sometimes!)

The pile of component sheets in my other lab is growing. I now have the electronics assembly lab, woodworking and grinding shop, machine shop, radio room and an outbuilding for welding, brazing, metalcasting and electroplating. I'm hoping to get a new laser engraver delivered next week so I can put my logo and part numbers/serial numbers on feedhorns. I have 87 component kit boxes part filled, but Real Life keeps intruding. Once they are shipped, I'll probably do an assembly video showing how I make them, but I need to get them shipped!!

@@MachiningandMicrowaves hi Neil. Really setting up a good workshop for metalwork too. I wish I had the space and most important the knowhow. I do intend to, maybe this winter, play a bit with a small lathe I have for few years now which someone practically gifted it to me. It the Ultimate rather old but I am told that it is a good lathe to start with.. Ok on the kits and all. Yes I do agree life has it's way to f..k up things and plans end up going down the drain. Recently, to give you an example, I installed a PV system in a small country house my brother has and forgetting I am no longer 18 I did all at one go. I ended up with 5 weeks of bed rest with a injured knee and back. And all my plans for my microwave maintenence program went up the drain. But much better now. Keep these videos coming. I really enjoy the video and comentry. Take care and stay safe

Burst disks are certainly used for gas guns with evacuated barrels, although they are usually formed into a dome

Not sure exactly what this is, the vendor just said 316, might be 1.4401, bit of molybdenum (2%), more nickel than 304, non-magnetic austenitic. Supposedly it welds nicely.

Some rather specialist Transducers! All will be revealed later this year.

i knew it

I have a pot of that as well, also good stuff.

Well spotted. I saw that when I edited the footage and wondered what on earth was going on. It's perfect with a different tap, I must try it with the M6 again (It's a YG-1, not a Volkel) and see if it is still offset. I didn't detect any wobble in the feel, it seemed rigid enough, so could just have been a chip. Reaching round the camera means I can't always see what's going on.

That would have been quite a good answer to the puzzle, but it was for the microphone membrane in the Great Seal Bug in this video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-GyryQltyDwA.html

I blame the camera. The inserts are 1/4 inch across

Most of mine are less than 3/32" or 2 mm, so that one is GIGANTIC in comparison!

I'm using UHMWPE for antenna dish elevation bearings with stainless steel shafts. Works really well, but it is funny stuff to machine. I have sometimes wondered if it's feasible to use half-wave rods in a nonconductive fluid to get point measurements of temperature, but I suspect the temperature effects on the relative permittivity of the fluid would far exceed any changes in length of the metal rods. One thing I'm working on at the moment is a microwave cavity using a resonance mode that doesn't have large wall currents so I can maintain an extremely high Q-factor just with a silver-plated machines copper block and change the resonant frequency by varying the temperature of the block. Adding in a an amplifier and delay line will turn it into a temperature-tuned oscillator. Then I can use a phase-locked loop (well technically a frequency-locked loop) using my Rubidium atomic clock and a fractional-N synthesizer to lock the free-running oscillator frequency. If I use two linked cavities machined into the same block and have a heat drain as well as a heat source, possible a Peltier plate, I think I should be able to get a stable loop lock without the usual synth phase noise and spurs because of the inherent low-pass filtering effect of the flywheel inertia of the temperature of the block. There was some some work done on this using a pair of laser diodes or dye lasers, one fixed temp, one variable, that you then mix together in an ultra-fast photodiode. It then generates the mixing product of the two lasers at sub-Terahertz frequencies, so two optical laser beams turn into a radio signal. Lots of fun to be had there I think.

The thing that give me panic attacks is when folks shove a finger inside a hole with some emery while it's doing 1000 rpm. Shudder... Most of the parts I need to polish internally are too small even for my little fingers. 304 is definitely easier to machine. This stuff is stringy like titanium unless you bury the tool nose and give it some proper umpty. At least it doesn't catch fire like one of my titanium jobs did last year. Impressively bright.

@@MachiningandMicrowaves I have a couple of "stunt-fingers" for those inside polishing jobs, just a wooden dowel with a bit of foam stuck to it (for softening edges) and a bull-dog clip for clipping the emery on, it beats having to explain your stupidity in A&E. i've not had the pleasure of machining titanium, although I've used titanium filings in some pyrotechnics before. It makes for wonderful sparks. pyro enthusiasts often use stuff they call magnalium, which is exactly what it sounds like - a fine mixture of magnesium and titanium powders, it's brilliant for long lazy sparks for rocket-tails.

I use some Delrin and PEEK cones as laps for the insides of feedhorns.

@@MachiningandMicrowaves I made a fixture that was basically just a spigot with a slot cut in it on the end of a piece of some plastic, acrylic maybe, that you could wrap some emery around and through the slot for putting a good surface on the inside of a part that got glued to a carbon fiber tube.

One of the more horrific injuries I saw on the internet was a fellow who stuck his index finger into a threaded hole of just the right size while the part was spinning. It didn’t “just” skin it. 8-(

I bought a job lot of brass bars a few years ago from the estate of an old model engineer I think, but I use a lot of brass for other things, so I end up with lots of short ends that I use for mandrels. They all seem to get re-used regularly once I've made them

Yep, I tried it with a cutting oil mist from my Noga-cool and it was pretty good even at those depths of cut. I can't use the camera with the Noga or soluble oil as it doesn't have removable filters or a sensible long lens. It was pretty good with just periodic squirts of ester-based cutting oil from a pump can. It was more a test to see if my little 3HP Colchester could dig in deep enough to get nice chip formation without going into overload, and how the new inserts would behave. I think the inserts didn't notice anything was happening and would probably do much heavier chiploads, but the motor would wheeze and the I'd have to use the rigid toolpost with no compound to get things stiff enough. It's rare that I need to move lots of 316 but I have a lot of large-headed pins to make that need to be more weatherproof than 303/304. I'll probably run soluble oil for that job despite the mess.

I think they use metallised mylar fixed to a weighted ring to make capacitor/condenser microphones. That would give a consistent preload. Mylar is pre-stretched BO-PET so it only needs to be tensioned, but for my application I need metal and it needs to be work-hardened and then tensioned. That 10 micrometre copper alloy film needs around 0.2 kN (abotu 20 kg/44 lbs) of tension to make it stretch if my calculations are correct about the modulus etc. The whole thing has been a fascinating excursion into the way metals behave in the elastic and inelastic/work hardening domains. I bet there's some videos about manufacturing condenser mics. I know they have some extremely fancy hole patterns in the fixed element to damp resonances. I've never found a "How it's made" about how they stretch the mylar and fix it, but there are hundreds about how they work. I guess the coating (which looks to be gold in the photos I've seen) on the mylar is vacuum-sputtered. I know they have to go to wild lengths to avoid resonance peaking as the wavelength of sound at 20 kHz is only about 15mm, so the large diaphragm microphone are much more than a wavelength across. As the air only moves a few tens of nanometers at 1kHz/40dB SPL, the damping is dealing with some mightily small hydrodynamic behaviours. Fascinating subject. I might have a play with metallising some mylar now I've got the vacuum pump and bell jar, but that will be for mmwave antenna reflector experiments!

Kind of not the point though, I wanted to try to reproduce the original. I actually bought some horribly expensive nickel foil and tried to plate it, but that was just a good way to burn £300 by the time I finished! The other issue is skin depth. I have a vacuum chamber and I can do vacuum deposiiton, but getting a thick enough layer of metal to keep the cavity Q high enough is REALLY hard. Needs at least 8 um, preferably 12 um. Then you have to find another way to tension the film and maintain contact and it starts to become a whole different reproduction. I'm going to look at EASYCHAIR Mk 2 at some point, using a hearing aid microphone and a diode as rectifier and modulator

6 fs is definitely well into the "splendid" region of performance. What connectors do you use?

@@MachiningandMicrowaves uBGA 6x8mm . Test board by me was high speed dielectric and coax traces with grounds above and below and along the sides of each trace. Edge fly into the SMC or 3mm ? connector. All inputs one side of IC and outputs the other side. Differential internal. The $1M HP rack and stack (2 were made) calibrated itself and each segment of the board before it drove the device and sampled the output. High Tech SiGe.

There's an enormous number of suppliers, mostly from China, who sell these foils. I haven't a clue what it's used for other than internal screening of some sorts of electronic devices.Burst disks are usually formed into a spherical surface, but need to me made form something with predictable fracture mechanics, It would work as a separator on vessels with chemicals incompatible with aluminium or stainless. Possibly as a target for subatomic particle counting or something like a screen-printing mask cut by a laser or electron/plasma beam, although titanium or stainless or nickel might be better for that. Very challenging question!

@@MachiningandMicrowaves OK burst disk makes sense but you are an microwave guy (and I am not:)). would there be any microwave or rf function for such a thing? I am fascinated by RF stops and filters created by PCB traces and this feels something like that.

@@OldePhart One application I thought of is to make a pressure-controlled reflective mirror to change the focal length of an antenna system at mmwave. I'm working on the coaxial low pass filter again now, I need to finish off the deep technical dive into how those filters work and get the next video in that series finished. The final part of the membrane stretcher series is just running through the producing program now, so should be live in 90 minutes or so. Another thing I need to make is a set of 90 degree hybrid combiner/splitters using a suspended copper stripline with four ports are 90 degree intervals, so if one device fails, the other won't see a major mismatch, and if the antenna or load port is disconnected, both amplifiers will dump their power into the dummy load port without seeing a dangerous mismatch.

​@@MachiningandMicrowaves Pressure controlled mirror . . . Just because you can doesn't mean you should... :)But I'll be watching. Love the vids.

@@MachiningandMicrowaves OK now, its the end of 2022 . . what was this for ?

I just snapped three more this morning. Trying a different sort of foil now, I think there are some flaws in that last one

It was all MECL III when I was playing with microstrip login boards all the way back in 1976. Happy days.

It has to be flat for this application, but I wonder what shape it would take with compressed air or hydraulic fluid? Would it be spherical, hyperbolic, parabolic? Wonder if you could make a focusing mirror that was adjustable?

@@MachiningandMicrowaves it could be pressed with gas or liquid against flat surface

@@MachiningandMicrowaves Spherical for small displacements. If the membrane is uniform the radius of curvature is set by the modulus of elasticity and the pressure. Edge effects from the clamping ring as the displacement increases.

@@murdo_mck makes sense that it's spherical at small displacements. I could try it and use a laser to map the surface to see when it goes measurably nonlinear

Heh heh, that's most days in my lab and machine shop and office.

The very same....

Definitely, that was my first attempt, A two stage press that grabs the foil then a second stage that strains it would work well. I suspect they electro deposited the nickel plus silver foil, then either peeled it off the substrate or used a dissolvable substrate

I think that old Colchester lathe has seen much more terrible things during its long and productive life!

@@MachiningandMicrowaves yes but the bad habits you are teaching it.

I missed a trick there, didn't I? I reckon it might sound like a Chihuahua licking a person's face. On my lap there is a Chihuahua. Wonder if I can get a recording? On second thoughts, perhaps not.

I use WD40 on aluminium, I have two gallons of the stuff in my chemical store. Haven't tried it on this 316, I'll give it a go. I'll check the datasheets for the inserts. Some of them insist on dry cutting, but that's usually at more extreme material removal rates. The Millicut J40 I normally use on steels did help a bit, but I didn't try it in the Noga Cool as I have to wear a respirator and run the extractor fans flat out. Perhaps I need a Fogbuster....

Sadly it's work-hardening and elastic strain that I need, not expansion. As I found to my cost when I caught the membrane with the flame from a gas torch. Bad times...

@@MachiningandMicrowaves thats too much heat, a hair dryer is enough

@@o74769 Yeah, the hole in the foil was a dead giveaway! I did try using a controlled temp oven, but the ring expanded as well as the foil, so that was a bit of a fail. I like the idea of heating just the foil to make it expand while keeping the ring cold, but then it needs to be soldered and that expands the ring. If the ring was in two parts, then a preheat and/or stretch then pressing the parts together would make a nice tight drum. However, just screwing the ring on to the polished and rounded edge of the threaded body works well. If I could use contact welding to fix it in place, that might be feasible too, or perhaps just compress the ring so it springs back to apply tension.

I need to work on my aim when glueing as well. Luckily, nobody other than me and half of the internet will ever see it!

I think AIMEE is trying to forge her own path. Less than convincingly... I'm pretty sure she still dreams of being a cool kid like Quinn though.

Heh heh, I've got a bit better at camerawork and lighting now, but I'm still a rank amateur compared with Proper RU-vidrs

Doesn't make it flat unfortunately, plus it will run away as it exceeds the elastic limit. Hydraulics would avoid that, but you still get a parabolic or hyperbolic form instead of a strained flat sheet with the grain boundaries arranged radially

If I get permission from the client, I'll do a series of videos about the instruments later in the year. It's a fascinating story

It looks like a simple transformer and rectifier then a large TO3 device for the 5V power rail. I can't see the marking, could be a 2N3055 type of thing or an LM7805K perhaps. It seems there are other voltages in there for the analogue elements. The 5V rail appears to run the 7-segment display as well. I only opened it up to see if I could fit a microcontroller with a USB or ethernet connection to send position data to a controller. I asked Newall if they had a circuit diagram, but they have no records of the detail of the product, and anyone who knew is long retired or no longer alive. One of the digits is a bit flaky, so a 5 looks like an 8, although a 0 is a 0. Nice to know these old lumps of electronics are still working fine like their cast-iron counterparts.

If you open her back up again, I'd be interested in board part numbers and gen suffix. It could be a fun project build old to be new again.

I need to fix the stuck segments at some point, so the case will be opened and I'll film what I find

My Chihuahuas go wild when they meet a hedgehog, so I cannot imagine the mayhem if they find me playing with tortoises. Mmmm, my neighbour keeps terrapins... Must nip round next-door for a cuppa.

The kiss has been retired and I think squelch is now past its sell-by date as well. Pop is staying. They will doubtless be replaced by even more horror-inducing examples, but that's Progress for you!

@@MachiningandMicrowaves Hurray, thank you! It took a few episodes before I couldn't handle the squelch anymore, so Progress and Novelty may be all the same to my poor tum 😊

First time I saw TTL for sale in Practical Wireless was September 1970 from Bi-Pak. I didn't buy any until '71 when I was 13. I think I bought some 7490s to make a divide by 100 circuit. They were furiously expensive at 22/6 each, just before decimalisation. I had to take my pocket-money to the Post Office in the village to buy a postal order. See page 79 of worldradiohistory.com/UK/Practical-Wireless/70s/PW-1970-10.pdf

Yep, it's annoying, but a commercial reality

Thats Chris Maj or Abom79 territory!

@@MachiningandMicrowaves whoops, 70 thou

@@pacman10182 That's only 1.8mm ish, what's wrong with that?

@@heybabycometobutthead my lathe cant do that in metal

@@pacman10182 That sucks, hope you get something a bit bigger someday

I'm getting much better and I'm doing some training as well. Controlling the heat in small diameter parts is where things go wrong. I can't see the weld pool clearly enough, so I had some special glasses made to match my eyes and let me focus quite close to the material. I'm trying a lighter torch as well to see if that helps. I'm working at it and determined to get to the point where I don't mind showing the raw welds on camera. I'm mostly doing seam welds of 1/16th inch aluminium sheet tubes rolled on my bi slip roll. I have to grind the welds flat so I don't have to show the evidence. I'm usually a fast learner so being so bad at TIG was a sobering reminder that I'm not half as clever as I think! I have huge respect for folks who can do really skilled work, I'm never going to be good at any of the zillion things I do, but I'm happy when I am at least vaguely competent

@@MachiningandMicrowaves look into a green lense for your hood gives better visibility and still does the job.

@@quadpop4643 Thanks,I'll have a look at them

@@MachiningandMicrowaves also the lenses with the reflective coating are good as well. Look up a vid on walking the cup it will serve for many situations and makes a beautiful weld.

I have "retired" that sound effect now, it made too many people uncomfortable!

@@MachiningandMicrowaves They're amusing, but caught me off guard. I enjoyed the Soviet bug series 🖖

@@604cpr Just working on the next instalment, but the Day Job is getting in the way of important things like playing with tech and machining and making RU-vid vids

Absolutely agree, see my reply to Mark's Hobby Machine Shop

At least Sulphur and Sulfur have the decency to sound the same!

@@MachiningandMicrowaves hahaha!!! indeed!!!

@@MachiningandMicrowaves You know, I did not realize that there are two spellings, and I did not realize that the British spelling and pronunciation is preferred by English speakers everywhere except North America.

@@drstrangelove09 The history of the naming is interesting, it started as "Alumium" When Humphrey Davey named it originally. www.merriam-webster.com/words-at-play/aluminum-vs-aluminium

A complete lack of technical ability with cameras perhaps? Oh, wait, not, I'm NOT hiding that...

I'll ask on the UK microwave and tech forums. Can you email me with the details of what you need and some contact info and I'll pass on the request

Heh heh!

Vacuum-assisted spud-gun. Way to go!!! Like Smarter Every Day's baseball cannon. Supersonic Maris Pipers anyone?