WW2 electronics AA delayed shells - Page 1
Forum section: electronics / general

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 06, 2019, 07:42:41 am
content: In things like anti-aircraft guns, with exploding projectiles, How did they make delayed fuses and proximity fuses, sensor based fuses, fit inside the projectile, way back in WW2 and before/after using electronics ?What kinds of circuits were they, surely they weren't making ultra mini vacuum types, or ultra mini high voltage batteries to fit in stuff like this, what kind of HV capactors maybe were used, or I wonder...etc ?https://en.wikipedia.org/wiki/Proximity_fuzeI can imagine maybe using the voltages from the weapons, being set for a certain range, then loading a RLC tank circuit, that decays as the projectile travels for few seconds, then somehow triggering at some lower voltage from the tank circuit. What were they really doing and how and with what ?

author: dmills
author_rank: Super Contributor
timestamp: April 06, 2019, 08:54:56 am
content: By the end the AA shells were actual radar proximity fuzes.Built with miniature valves and a rather clever battery that was activated when the acceleration of the firing broke a glass tube of acid.There are diagrams (Including circuit diagrams) out there.Incidentally, ground combat using these (very expensive) rounds in error was how they discovered the terrifying effectiveness of air burst rounds on infantry.Google is your friend (But it helps if you spell fuze correctly).

author: vk6zgo
author_rank: Super Contributor
timestamp: April 06, 2019, 09:03:15 am
content: Quote from: lordvader88 on April 06, 2019, 07:42:41 amThe link you provided answers most of your question-------but, yes, there were very small vacuum tubes & gas thyratrons made at the time.In fact, the link mentions this (ignore the reference to "all solid state" a couple of paragraphs in).Miniaturised "high voltage" batteries (actually around 22.5 volts) were commonly used in tube type hearing aids immediately before & just after WW2, so the capability was available.The proximity fuse batteries were probably less of a design problem than hearing aid ones, as flight times of the shell were very short, so neither the HT or "filament" battery needed a long life.Shelf life is of course important in both applications.If it was being designed today, it would almost certainly contain a microcontroller somewhere, but people have become so accustomed to being able to use "brute force" methods easily, that they cannot readily comprehend the "work-arounds" that allowed designers in earlier times to produce effective devices.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 06, 2019, 09:09:26 am
content: Quote from: dmills on April 06, 2019, 08:54:56 amMuch of the world call them "fuses".Google usually isn't very sensitive to US-v-"just about everybody else" spelling distinctions, & will normally bring up the same sites using both spellings.

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 06, 2019, 10:57:35 am
content: well why do so many tubes need several hundred volts, why were these super low voltage tubes not used in radio's, tv, etc ?

author: soldar
author_rank: Super Contributor
timestamp: April 06, 2019, 11:20:57 am
content: Quote from: dmills on April 06, 2019, 08:54:56 amCan we have some cites corroborating that? Because I find it extremely difficult to believe.I know AA guns were aimed using radar but those radars were the size of trucks so I would be very surprised to learn the shells had radar proximity fuses.I would think they were timed fuses which were simply mechanic or chemical.

author: dmills
author_rank: Super Contributor
timestamp: April 06, 2019, 12:22:17 pm
content: Here is a decent articlehttps://warfarehistorynetwork.com/daily/wwii/artillery-proximity-fuses/But a quick search on "ww2 proximity fuze" will turn up quite a lot of stuff including drawings and cutaways, these things were made for AA, Artillery, gravity bombs.Arguably it was more RF proximity sensing then radar, but still.Regards, Dan.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 06, 2019, 12:24:09 pm
content: Quote from: lordvader88 on April 06, 2019, 10:57:35 amThey weren't really up to the job, & there was really no advantage in their use.Analog TVs in particular, need to produce fairly serious power in the horizontal & vertical scanning circuits.The easiest way to get such power is to use higher voltages & full sized tubes.Conventional Superhet radio receivers used compound tubes in their mixer stages, which could both do the mixing and provide the local oscillator function.Very hard to do with sub-subminiature tubes, as was the audio output requirement of, commonly, several watts.The gain of even full sized tubes with low anode voltages was low, & it was not till the 1960s that tubes designed to operate with anode voltages of around 12v with enough gain to be used in the RF & IF stages of car radios were developed.(this allowed the car 12volt battery to run everything.)Those radios had solid state audio output stages, as power was too hard to obtain with tubes at such low voltages, whereas power transistors were designed for such service.

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: April 06, 2019, 12:27:58 pm
content: Quote from: lordvader88 on April 06, 2019, 10:57:35 amIn brief: more voltage, more power, less distortions:(In the twenties, the Soviet industryproduced ST-6 vacuum tube. Due to the use of an “accelerating” (with a positive voltage) cathode grid, and a small gain factor, the tube could work at an anode voltage of only 20 volts. But in general it was worse then R-5 at 100V of anode voltage).Quote from: soldar on April 06, 2019, 11:20:57 amJust google "Mark 53 proximity fuze":https://www.radiomuseum.org/r/crosley_proximity_fuse_mk53_fuze.htmlQuote from: soldar on April 06, 2019, 11:20:57 amThese devices have different work distances. Tens of kilometers for air warning/fire control radar and tens of meters for proximity fuze.

author: Gyro
author_rank: Super Contributor
timestamp: April 06, 2019, 12:30:06 pm
content: Quote from: lordvader88 on April 06, 2019, 10:57:35 amLow voltage directly heated tubes were used in many many battery portable radios. They used 1.5V filament and 90V (end voltage ~50V) batteries. They were capable of driving an efficient paper speaker at acceptable volume. Specialised tubes like Electrometer tubes have amaximumanode voltage of around 6V.The problem with low voltage tubes - low power capability (although valve rectifiers and series voltage regulator triodes work at low anode-cathode voltage drop, not battery applications though). As for TV's, what would be the point, you need EHT to make a visible image on the screen, high drive on deflection coils etc.

author: chris_leyson
author_rank: Super Contributor
timestamp: April 06, 2019, 12:33:06 pm
content: All of the US manufactured proximity fuzes used VHF doppler at around 150MHz or so, although I can't find a reference to confirm that. I powered up a Mk 45 fuze about 20 years ago at it seemed to oscillate at 120MHz. About 15 million Mk 45 fuzes were manufactured for the US army and about 1.6 million for the the British army, also about 80,000 Mk 45 (3"/50) were used by the US navy but suffered from premature detonation due to high waves when fired at a low angle, they were withdrawn from navy service and replaced with a five tube design with the additional tube used for AGC, possibly the Mk 53 or Mk 58.The Mk 45 used three miniature triodes and a thyratron. A single triode VHF oscillator was mounted just under the antenna and a pair of triodes were used as the detector which triggered a miniature heated thyratron that was used to discharge a 1uF 100V paper cap into the squib.The battery was made up of stacked annular discs, one side zinc and the other carbon, with plastic spacers and an amuple of chromic acid. The shock of gunfire would shatter the ampule and the spin of the shell would distribute electrolyte throughout the battery plates. It took about 1/10th of a second after set-back before the radio transmitter functioned.Due to the high forces at set-back the valve structure would buckle slightly causing the tungsten filament to bend so a ruggedised tube was developed with a small "mouse trap" spring to keep the filament under tension.Reference "The Deadly Fuze, The Secret Weapon of World War II" Ralph B. Baldwin ISBN 0 354 01243 6US3113235 Rugged Vacuum Tube H.H Porter EtalUS3166015 Radio Fequency Proximity Fuze M.A. Tuve EtalA poor picture of a pair of Mk 45 triodes posted below. Top tube is the oscillator triode and you can just see the grid support in the centre. Bottom tube is one of the detector triodes, the 'T' shaped structure to the right, mounted between the supports, has the "mouse trap" spring wound onto it.Somewhere I have a schematic from a reverse engineered Mk 45 and will post it when I find it.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 06, 2019, 12:39:07 pm
content: Quote from: soldar on April 06, 2019, 11:20:57 amIt wasn't really quite radar, but the free running oscillator in the fuse was affected by the proximity of other objects.Apparently therewasa reflected wave which was Doppler shifted.This mixed with the local oscillator in the oscillator tube*, having more & more effect as the other object became closer, until it tripped the fuse.This is the best translation I can make from the quite meagre information I found on the 'Net.*It was not unusual to use tubes for several different functions, before the advent of compound tubes which separated the functions, offering better stability.PS:- It seems the "production" version was more complex, as describes bychris_leysonabove.

author: chris_leyson
author_rank: Super Contributor
timestamp: April 06, 2019, 12:53:28 pm
content: Radar was never used in WWII proximity fuzes. The Doppler signal from a reflecting target was detected by measuring the variation in oscillator anode current as the shell approached the target. I think typically they were designed to detonate at 50 feet or so from the target but there were lots of variations depending on the application. If used to shell fox holes as in the Battle of the Bulge I think the optimum burst height was 70 feet, the German army didn't know what had hit them. They were also very effective against the V1 with help from the M9 gun director and SCR-584 radar. A real Mk 45 shown below (inert).

author: dmills
author_rank: Super Contributor
timestamp: April 06, 2019, 01:15:45 pm
content: Sure sounds like CW Doppler radar to me, especially as they shaped the radiation pattern and amplifier responses to make the range/velocity sensitivity match the shrapnel pattern.Radio ranging certainly, and if a modern microwave doppler door opener can be described as a 'radar' sensor, and I have seen them described that way, then that surely qualifies?Regards, Dan.

author: soldar
author_rank: Super Contributor
timestamp: April 06, 2019, 01:39:01 pm
content: Thanks for the very interesting information. Those WWII fuzes were more advanced than I thought.

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 06, 2019, 02:11:24 pm
content: Quote from: soldar on April 06, 2019, 11:20:57 amIt's ture, and it like to see a schematicWhen they 1st made radar, they where trying to detect reflections, at a few miles, that where about 100-1000 times stronger Watts/area than a typical radio of the time used, around micro-Watts/meter^2 iircSo in some projectile, that's getting within 10-50 meters or whatever, the radar EM is way way stronger. But what all is the circuitryand what parts/etc ??When 'they' 1st started making spark gaps that would pick up EM waves, did they in-effect miniaturizes that, so that it sets off some primer cap ?

author: chris_leyson
author_rank: Super Contributor
timestamp: April 06, 2019, 02:17:57 pm
content: From Merle A. Tuves patent US3166015"With the oscillator 35 energized, as the projectile approaches a target, such as an airplane, the radio waves emanating from the projectile are reflected by the target, and the reflected waves change the radiation resistance of the antenna 33. As a result, the loading of the oscillator 55 circuit is changed, whereupon the plate current of the tube 40 also changes. This current change in the plate circuit develops a voltage across resistor 50 which is impressed upon the amplifier 36 through the resistance 52 and a wire 78 connected through a plug-and-socket connection 79 to one side of a condenser 83 in the amplifier unit. The other side of the condenser 83 is connected to the control grid of tube 84, the resistance 82 providing proper grid bias. The condenser 80 serves to by-pass high frequencies to the ground and cooperates with resistor 52 to form a low pass filter.The amplifier, as shown, is provided with a second stage of amplification, including a tube 85, and the output of the amplifier is used to trigger a thyratron 86."Maybe it could be argued it's very primitive CW radar but I would say it's more akin to a proximity detector. As the patent was filed January 1943 it's probably an early example of a proximity fuze. Must go and find that schematic.

author: Mr. Scram
author_rank: Super Contributor
timestamp: April 06, 2019, 02:21:35 pm
content: It always boggles my mind that a place as violent as an artillery shell can carry electronics without destroying it before final detonation. The fact they managed to do this that long ago without the benefits of ICs is the cherry on top.

author: dmills
author_rank: Super Contributor
timestamp: April 06, 2019, 02:34:02 pm
content: The electronics is not hard, making the electronics work in a shell acceleration environment in a way that is sufficiently squaddie proof and safe to abuse, that is tough (Also, at least reasonably sea water resistant). Actually a big part of the real magic was the power source for the thing which had to come up to power quickly (~0.1 seconds) and have a shelf life of years.There were issues with firing at low angles over rough seas where the the waves could be detected and cause detonation, they fixed this with a diode detector producing a bias to the trigger circuit.The design is an awesome mix of physics, chemistry, electronics and mechanical engineering.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 06, 2019, 03:30:51 pm
content: Quote from: vk6zgo on April 06, 2019, 09:09:26 amQuote from: Wikpediahttps://en.wikipedia.org/wiki/Fuze

author: iMo
author_rank: Super Contributor
timestamp: April 06, 2019, 03:45:27 pm
content: The projectile rotated 3000 rev/minute, and the antenna had a special radiation pattern.While in proximity to the target it created a beat, the beat was amplified and triggered the fuse. So no Doppler, afaik.The fuses were easy to trigger far from target by sending modulated signal and sweeping around the frequency (around 200MHz). That was proven during US experiments in late '44 as the large amount of fuses were captured by Germans after D-day and US military was looking for potential countermeasures.

author: Cyberdragon
author_rank: Super Contributor
timestamp: April 06, 2019, 03:48:45 pm
content: Quote from: Gyro on April 06, 2019, 12:30:06 pmSubminiature tubes were used a lot in the military were applicable from walkie-talkies to radar control systems. They weren't often used in the consumer market, but there were things like pocket radios and hearing aids that used submini tubes.https://www.radiolaguy.com/Showcase/PortableRadios/subminiature.htmhttps://www.google.com/url?sa=t&source=web&rct=j&url=https://www.cia.gov/library/readingroom/docs/CIA-RDP80-00809A000600330387-6.pdf&ved=2ahUKEwjugLOc5rvhAhWDct8KHelKDV8QFjANegQIBhAB&usg=AOvVaw2OXeQISlvzVe04eLA-4yg3They were also used in some calculators and computers.https://www.radiomuseum.org/forum/subminiature_tubes_in_computers.htmlNote: these tubes operate like a normal vacuum tube, unlike the low voltage car tubes which were space charge tubes.

author: chris_leyson
author_rank: Super Contributor
timestamp: April 06, 2019, 06:47:51 pm
content: I think Merle A. Tuves patent is probably for the Mk 30 or maybe Mk 32 fuze for 4.5 inch AA guns. The Mk32 required separate oscillator and amplifier sections which made it quite long and it also required a 2 inch dry battery.Early fuze designs used 67.5V dry batteries which were also used in some WWII walkie-talkies, however, it was found that the shelf life was as short as 3 to 4 months in the south pacific, but in general was 6 to 12 months. National Carbon Company, a division of Union Carbide, set about developing a reserve "wet" battery. The reserve batteries were made up of stacked zinc/carbon annular rings around a small glass ampule containing chromic acid. The ampules were supported by a "crown" breaker or a "Bellville washer" in the 1.5 inch batteries and a "two point" breaker in the 2 inch batteries. As the centrifugal forces in a spinning the shell were so high it was possible to have a dead section in the battery if the electrolyte was not uniformally distributed. To fix this 1/64th inch holes were drilled into the battery plates so that the amount of electrolyte reaching each plate was equalized. It was considered preferable to allow a high resistance short through these holes than to risk complete fuze failure through improper electrolyte distribution. The same production lines that made Christmas tree lights were used to make ampules - hence no Christmas tree lights for the duration of the war. Eastman Kodak did a lot of work on the battery design alongside National Carbon and spent a million man hours on production methods and tooling before producing a single battery. On V-J day, Nation Carbon, Eastman-Kodak and Hoover were producing 101,000 batteries per day.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 06, 2019, 11:47:51 pm
content: At least where I have worked in the US a fuze is a device to set off ordnance while a fuse is used to limit excessive current. Don't know about world wide usage but nationalized spell check wouldn't help that since the program has no idea what you are talking about.The story of the VT fuze has always fascinated me. VT stood for variable timing and was a bit of disinformation to conceal the fact that it was a proximity fuze. Prior to this fuze AA shells had a timer which was set mechanically before firing. Time delay chosen to go off when it reached the altitude the targets were expected to be at. Obviously there are all sorts of problems with that, starting with knowing that altitude, convincing the targets to stay there, getting the poor guy loading the gun to twist his screwdriver the right way over and over again and following through to various times to altitude due to ammunition differences, air density variations and the like. But as a partial answer to lordvaders original question these fuzes where purely mechanical. A spring driven clockwork movement. These movements were quite reliable and still used in safeing and arming applications well into the 1980s and 1990s. But the whole infrastructure for that, from design through manufacture is gone now. Too expensive without that infrastructure.There were 13 manufactures for the tube used in the VT fuze. They tested huge batches and found that only one relatively consistently survived the firing (when waxed into a hole cut in a wooden block). I think I remember that Sylvania was the winner on that.There was an optical version also developed, but it never worked out all that well.The thing that really fascinates me about this fuze was how fast this got into production. Tuves and team apparently got the concept in 1941 and 4000 units were built and tested at White Sands in early 1942. Less than a year later they were at full production making 80,000 per week. Pretty impressive ramp up for a totally new technology and working under the constraints of total secrecy. Some folks say this was the second most secret project in the US, after the Manhatten project. Shows what can be done when you really, really want to.

author: jmelson
author_rank: Super Contributor
timestamp: April 07, 2019, 03:09:58 am
content: Quote from: vk6zgo on April 06, 2019, 12:24:09 pmI have an R-392 receiver that runs entirely off 28 V DC, with no voltage converter. All tubes are pretty standard-looking 7-pin miniature. It works pretty well. It was designed to run off a military truck electrical system.Some later gear moved to 57xx series tubes that were even smaller, and ran on pretty low plate voltage.Some of the 1960's crypto gear had hundreds of these tubes in one unit.Jon

author: james_s
author_rank: Super Contributor
timestamp: April 07, 2019, 04:19:55 am
content: Quote from: lordvader88 on April 06, 2019, 10:57:35 amThey were, well not those specific tubes but low voltage tubes were used in farm radios that ran off 32V. Tubes are less efficient at low voltages though, they are inherently high impedance devices so the current they can carry is limited. For a given tube if you use a higher voltage it can handle more power all else being equal. When you've got a wall socket available there's no reason to try to make a radio with a low plate voltage when you can have a much higher voltage available and get much better performance for the same cost in parts.

author: jesuscf
author_rank: Frequent Contributor
timestamp: April 07, 2019, 05:08:41 am
content: Very interesting. If the enemy knew about this kind of fuze, wouldn't a radio receiver had detected an incoming projectile? Once detected, wouldn't it have been easily activated with a radio transmitter? It reminds me of what happened with the German magnetic mines. Thunderf00t has a nice video about it:

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: April 08, 2019, 01:08:40 pm
content: Quote from: jesuscf on April 07, 2019, 05:08:41 am"The method and system of this invention is a fuze jamming device which is effectually a repeating facility in which the continuous wave (CW) signal transmitted by the fuze is received, and retransmitted back to the fuze."

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 08, 2019, 01:57:44 pm
content: What I find incredibly fascinating about WW2 is the amount of technical and engineering achievements by all major belligerents.And those were done in record time, and within the constraints of simultaneously waging a total war.Back to the original topic.There were several very low voltage tubes developed. My fave is the CK534AX. With anoperatingplate and filament voltages of 15 and0.625volts respectively, these were well within transistor power supply levels.

author: Gyro
author_rank: Super Contributor
timestamp: April 08, 2019, 09:50:58 pm
content: It'sbecausethe parties were waging total war, not despite.Winning a (conventional) war depends on outpacing the enemy in all things. That means that factories get re-assigned from their previous production to weapons etc. R&D goes the same way. Normal working hours, marketing overhead etc. go out of the window and everyone focusses on coming up with something new and getting it into use as urgently as possible.Nothing unites a country in a common goal like all-out war (sadly).

author: Mr. Scram
author_rank: Super Contributor
timestamp: April 08, 2019, 11:40:44 pm
content: Quote from: schmitt trigger on April 08, 2019, 01:57:44 pmLook at all the junk the world manages to produce on a daily basis and imagine all those efforts redirected into a war effort, with the added incentive of people working to protect their lives and everything they hold dear.

author: chris_leyson
author_rank: Super Contributor
timestamp: May 06, 2019, 06:52:40 pm
content: After a little bit of research I'm sure I have a Mk45 Mod 11 fuze. According to OP-1480https://maritime.org/doc/vtfuze/index.htmthe approximate length of the Mk45 Mod 12 is 7.7", my fuze measures 8" when what is left of the rear section is screwed on. I think when they were deactivated they just chopped the back end of the rear section off with a band saw. The Mod 11 was longer and taken out of service.I have the schematic drawn out but need to check the cathode connections for "top" and "bottom" filament connection.Also have to check the capacitor orientations for outside foil. There are six capacitors in the amplifier section not counting the firing capacitor. Three of them are marked RCA TYPE M 0.004 MFD and the other three are marked 0.01 SELKAR S P12705.It turns out that the "SELKAR" tubular capacitor was manufactured by Sprague from 1944 onwards for the US Navy,Sprague Electric Co. v. Commr. of Internal Revenue. What looks like a paper capacitor actually turns out to be metallized film, cellulose acetate.The firing capacitor is maked M927654 1 MFD 100 V.D.C. FAST A8076. Best guess for B+ operating voltage is 67.5V because 67.5V dry batteries were available in the 40's and dry batteries were used in earlier fuzes. Ralph B. Baldwin's book mentions 67.5V dry batteries.