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bbear
Airman 1st Class
I very much doubt it. at least for WW2. even for a 5" it was a squeeze. the valves you see. Sorry tubes.
.Here's a few links
8 minute introduction places and faces hhttps://www.youtube.com/watch?v=6-D592VR4RU see fuze size related to human hand at 3:27
http://www.bombfuzecollectorsnet.com/userimages/radio proximity vt fuzes.pdf authorised version of events facts and figures
Proximity Fuze History Southwest Museum of Engineering,Communications and Computation# history context
https://www.jhuapl.edu/techdigest/views/pdfs/V02_N1_1962/V2_N1_1962_VTfuze.pdf history with a telling picture on p22*
https://www.drdo.gov.in/drdo/pub/monographs/Introduction/Proximity_Fuzes.pdf post war discussion from ally. see Section 1.7 A Striking Combat Success
.Here's a few links
8 minute introduction places and faces hhttps://www.youtube.com/watch?v=6-D592VR4RU see fuze size related to human hand at 3:27
http://www.bombfuzecollectorsnet.com/userimages/radio proximity vt fuzes.pdf authorised version of events facts and figures
Proximity Fuze History Southwest Museum of Engineering,Communications and Computation# history context
https://www.jhuapl.edu/techdigest/views/pdfs/V02_N1_1962/V2_N1_1962_VTfuze.pdf history with a telling picture on p22*
https://www.drdo.gov.in/drdo/pub/monographs/Introduction/Proximity_Fuzes.pdf post war discussion from ally. see Section 1.7 A Striking Combat Success
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Shortround6
Major General
It took until the 70s (??? open to correction) to get proximity fuses into the 40mm Bofors gun shells. Shells tend to follow the cube law. Shells of similar shape will have 8 times the volume as a shell 1/2 their size.
Glider
Captain
Even if they had worked I doubt that they would have been more effective than the fuses already fitted to the shells (by mid war). They were fused to explode a fraction of a second after hitting something so they exploded inside the aircraft, which is far more effective than exploding outside the aircraft
Barrett
Senior Airman
Thanks for the links, will forward to some ordie friends.
One of my antiquer pals in California, 1970s, had been a student at Cal Tech when the war started. Really bright, and had a rare student deferment. He was put onto a Beyond Top Secret project, highly compartmentalized, and told by men in trench coats that it was Death Or Worse to talk to anybody. Naturally Bob compared notes with another guy and between them they G2'd that the VT fuze was underway.
One of my antiquer pals in California, 1970s, had been a student at Cal Tech when the war started. Really bright, and had a rare student deferment. He was put onto a Beyond Top Secret project, highly compartmentalized, and told by men in trench coats that it was Death Or Worse to talk to anybody. Naturally Bob compared notes with another guy and between them they G2'd that the VT fuze was underway.
bbear
Airman 1st Class
[QUOTE="", The smallest sheill i know with VT is 40mm for L70 Bofors.[/QUOTE]
I think those L70 versions were beyond WW2 technically , brought in around 1951? possibly an altgrrred tech mini-tube? Or early transistors? THis os why so many US Navy vessels changed Bofors 40mm quad mounts with 3" guns, or so I'm reading. VT was available in 3" in period Mk45 in May 1944..
I think those L70 versions were beyond WW2 technically , brought in around 1951? possibly an altgrrred tech mini-tube? Or early transistors? THis os why so many US Navy vessels changed Bofors 40mm quad mounts with 3" guns, or so I'm reading. VT was available in 3" in period Mk45 in May 1944..
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bbear
Airman 1st Class
Could you please clarify what you mean by the doppler feature? Do you mean the suppression of function when fired at low angles over water? Or the limit of detection bandwidth? Or suppressing the microphone effectOr are you talking about Countermeasures now?
Doppler shift is for 3x 10exp. 8 m/sec. emission from a subsonic source and subsonic reflector maybe 300m/sec - negligible shift?
or
who/what are you responding to?
thanks
Edit does this text from wikipedia express or address your question?
The Allied fuze used constructive and destructive interference to detect its target.[23] The design had four tubes.[24]One tube was an oscillator connected to an antenna; it functioned as both a transmitter and an autodyne detector (receiver). When the target was far away, little of the oscillator's transmitted energy would be reflected back to the fuze. When a target was nearby, it would reflect a significant portion of the oscillator's signal back. The amplitude of the reflected signal corresponded to the closeness of the target.[notes 1] This reflected signal would affect the oscillator's plate current, thereby enabling detection. However, the phase relationship between the oscillator's transmitted signal and the signal reflected from the target varied depending on the round trip distance between the fuze and the target. When the reflected signal was in phase, the oscillator amplitude would increase and the oscillator's plate current would also increase. But when the reflected signal was out of phase then the combined radio signal amplitude would decrease, which would decrease the plate current. So the changing phase relationship between the oscillator signal and the reflected signal complicated the measurement of the amplitude of that small reflected signal.
This problem was resolved by taking advantage of the change in frequency of the reflected signal. The distance between the fuze and the target was not constant but rather constantly changing due to the high speed of the fuze and any motion of the target. When the distance between the fuze and the target changed rapidly, then the phase relationship also changed rapidly. The signals were in-phase one instant and out-of-phase a few hundred microseconds later. The result was a heterodyne beat frequency which corresponded to the velocity difference. Viewed another way, the received signal frequency was Doppler-shifted from the oscillator frequency by the relative motion of the fuze and target. Consequently, a low frequency signal, corresponding to the frequency difference between the oscillator and the received signal, developed at the oscillator's plate terminal. Two of the four tubes in the VT fuze were used to detect, filter, and amplify this low frequency signal. Note here that the amplitude of this low frequency 'beat' signal corresponds to the amplitude of the signal reflected from the target. If the amplified beat frequency signal's amplitude was large enough, indicating a nearby object, then it triggered the 4th tube - a gas-filled thyratron. Upon being triggered, the thyratron conducted a large current that set off the electrical detonator.
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Shortround6
Major General
I think those L70 versions were beyond WW2 technically , brought in around 1951? possibly an altgrrred tech mini-tube? Or early transistors? THis os why so many US Navy vessels changed Bofors 40mm quad mounts with 3" guns, or so I'm reading. VT was available in 3" in period Mk45 in May 1944..[/QUOTE]
The guns may date form 1951 or so but the proximity fused ammo for them was a much later development.
bbear
Airman 1st Class
The guns may date form 1951 or so but the proximity fused ammo for them was a much later development.[/QUOTE]
Looking through online sources briefly it seems the history is this:
The 40mm Bofors was de-emphasised in US procurement at 1945 because the 3" installation using VT ammunition better fit the projected need for AAA. However servicing the installed 40mm base, other forces and other needs kept he platform relevant, with an upgrade to 40L70 in the the '50's, until 1980/81. At that time the development of the PFHE ammunition type with proximity fuze function. That ammunition with added automatic target tracking, gun laying etc put the Bofors 40L70 back near the cutting edge of AAA and the proximity fuze fully transistorised to the 40mm size was born again bad-ass as PFHE against ship killers of a new generation. THe 40L70 platform and has stayed somewhere close to that status. Emerging threats resulted in the 3P ammunition generation which as yet still needs additional caliber as it is available only in 57mm format.
1. https://www.drdo.gov.in/drdo/pub/monographs/Introduction/Proximity_Fuzes.pdf section 1.10 post war developments, none of the fuze types mentioned are 40mm
2. PFHE specs https://www.marinha.mil.br/emgepron...br.emgepron/files/fichatecnica/lt_40mml70.pdf
3. https://www.janes.com/images/assets/571/36571/Surviving_the_swarm_new.pdf
The emergence of 'smart' medium-calibre ammunition is also noteworthy. Programmable fuzes - such as the 3P fuze developed by BAE Systems Bofors for its 57 mm gun line - enable ammunition to be programmed at the point of launch so as to optimise effect against specific target sets. The development of guided rounds - exemplified by Oto Melara's emerging Vulcano 76 sub-calibre projectile - offers the prospect of extended range and precision accuracy (enabled by the combination of GPS/inertial mid-course correction coupled to IR terminal guidance).
4. USA Bofors 40 mm L/60 Model 1936 - NavWeaps also contains this text
1a Bofors introduced their 40 mm PFHE proximity round during the 1980s. This was similar to those developed for their larger guns. Bofors claims a maximum effective bursting radius of 18 feet (5.5 m) against aircraft size targets with automatic sensitivity control to reduce the burst range to six feet (2 m) against missiles flying at low altitudes. As of 2001, Bofors was producing HE-T, AP-T and APHC-T (armor piercing high capacity - tracer) rounds for these weapons. The APHC-T round is unusual in that it carries an armor-piercing slug within an aluminum body. Bofors claims that this round penetrates some 30% deeper than the earlier AP-T round and that the aluminum body has an incendiary effect on the target.
5. confirming source 3/11 Regiment, Royal Malta Artillery.
The weapon was superseded in the British Army by the 40 mm L/70 automatic anti-aircraft gun in 1957 when 16 AD Regiment Royal Artillery was equipped with L40/70, with its three batteries having a total of 18 guns. The L/70 had entered service with the Swedish Army in 1951 and was manufactured under licence in various countries including UK. There were two basic models Type A and Type B. Type B had a three phase 220 volt 50 Hz APU mounted on the rear of the carriage and Type A was fed from an external power source. A high rate of 300 rounds per minute was achieved through ramming the rounds during run out. It had five types of ammunition for anti-aircraft and anti-armour roles. The Pre-Fragmented HE round (PFHE) had a proximity fuze with an effective range of 6.5 metres against aircraft and the improved Mk2 could effectively double this figure. " I'm saying this confirmss in one source the easy confusion, The 1957 gun being described close to 1980's ammuntiion spec. implying they were contemporaneously manufactured in 1957
6. Design philosophy of the 40L70 with similar juxtaposition of gun date and ammunition type inviting misapprehension
The Bofors Gun – Part II: the L/70 Weapons - Chris Chant's Blog
7. continuation of the above article 6. showing the 3P round impact on capability
The Bofors Gun – Part III: Modern developments - Chris Chant's Blog
"In itself this Trinity 3P is a formidable round, but its capabilities are boosted by the use of a new Philips Elektronikindustrier programmable fuse, which is set while the round is in the feed system so that the bursting parameters for each round can be programmed during each burst of fire. It is this combination of barrel accuracy and programmable fuse that allows the use of a pre-programmed detonation pattern for the projectiles in any 10-round burst, allowing the operator to blanket a target with detonating projectiles and so maximise kill probability. "
can we tell any other enquirers that any mystery there was is solved that the case is closed? That there were no VT on Bofors 40mm in WW2 period. Period. That is the above sources all confirm your memory and understanding is accurate.
all the best
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One of the documents (I think you) listed mentioned the doppler effect. Usually doppler effects involve closure rates as the frequencies change as you move towards/away from something.
From what I read, the system seemed to transmit a series of pulses which were cancelled out or amplified by the reflecting currents being out of phase or in phase, which produced "beats" as the frequency was cancelled out and reappeared. And the system effectively measured the change in the frequency of these beats due to the closure rates.
bbear
Airman 1st Class
Hi, I think what you read was this.
How a Radio Proximity Fuze Operates Among various possible types of radio proximity fuzes, an active-type fuzed operating on the doppler effect was selected as being the most promising method. In a doppler-type fuze, the actuating signal is produced by the wave reflected from a target moving with respect to the fuze. The frequency of the reflected wave differs from that of the transmitted wave, because of the relative velocity of the fuze and the target. The interference it creates with the transmitter results in a low-frequency beat caused by the combination of the transmitted and the reflected frequencies. The low-frequency signal can be used to trigger an electronic switch. Selective amplification of the low-frequency signal is generally necessary. Operation of the fuze occurs when the output signal from the amplifier reaches the required amplitude to fire the thyratron. For a given orientation of the fuze and target, the amplitude of the target signal produced in the oscillator-detector circuit is a function of the distance between the target and the fuze. Hence, by proper settings for the gain of the amplifier and the holding bias on the thyratron, the distance of operation may be controlled. Distance, however, is not the only factor which requires consideration. Orientation or aspect is very important,
yes. If so I'm notv surprised you were prerplexed.
The VT fuze is a Continuous wave not a pulsed wave device,. And as explanations go I prefer the wikipedia or military wikipedia explanations.
I'd like to have a go at explaining it myself, this would be risky as
1. I'm an aging nit and no one understands more than 1/2 of what i say these days.
2. I never finished my electronics training
3 I was trained by the generation who were trained by the original circuit designer
4 I was never trained on valves (tubes)
5 never worked on any military application
6 the list goes on
so just to give you a taste and so I don't spend a lot of time writing stuff you are not interested in:
200 MHz emission, speed of light 300 x million metres/ sec wavelength 2/3 m or about 66cm, 300 m/sec projectile Target assumed to be stationary
There are two ways to explain most electronics of this kind, frequency and time (phase).
The frequency description is boring - doppler, yawn, For me the real story is in the phase
Each 33cm that the shell advances the phase of the reflected signal changes by 2Pi or 360 degrees, one half wavelength less to get there, one half wavelength faster less getting back
But until you get close the amplitude of that phase shifted return is zip.
As you approach the target a greater % of the emitted energy is reflected back,. the antenna picks up a small % of this but the effect is to increase the plate current of the oscillator tube causing an increase in the emitted signal energy (+ve feedback)
As the distance shortens further the phase shift of 360 degrees is a greater and greater fraction of the remaining distance (take 33cm at a mile versus 33cm at 6 metres ) (the beat frequency rises - doppler )
As the shell comes to its closest approach there is an inflection in the beat frequency (rising to falling doppler)
But also a change in the sign of the phase (each 33cm advance takes you 2Pi or 360degrees away from the target) positive phase shift to negative phase shift. Thus at one instant it is zero, the closest the shell will come, the largest collector plate current.appears right then, If at that point with the Positive feed back the circuit triggering the thyratron either reaches a saturation point, or it doesn't.
oh dear, I'm afraid I rather ran on
I'm often perplexed, but that often drives me to learn stuff. Then I stop being perplexed. Until something else catches my curiosity anyway
.So it emits a steady frequency tone?
Actually older people know more stuff, our education system (particularly in the United States) is a disaster. There's rules on this forum about politics, so I'll try and avoid getting up on the soap-box...
You probably forgot more than I've learned...
That, I actually understand...
Not necessarily. The doppler effect has effects that can be felt in real time (an airplane coming in for a landing, a train, etc), as well as other matters like the movement of other galaxies and things of that nature.
A wavelength is 360, so every half wavelength it travels, you'll get a cancellation of the signal as it's out of phase?
Meaning it's slightly overshot the target and is no longer heading towards, but heading away?
Don't worry, teaching and learning takes time.[/quote]
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bbear
Airman 1st Class
just discovered a new to me original' source
https://nvlpubs.nist.gov/nistpubs/sp958-lide/059-062.pdf
https://nvlpubs.nist.gov/nistpubs/sp958-lide/059-062.pdf
bbear
Airman 1st Class
[/QUOTE]I'm often perplexed, but that often drives me to learn stuff. Then I stop being perplexed. Until something else catches my curiosity anyway
So it emits a steady frequency tone?
Actually older people know more stuff, our education system (particularly in the United States) is a disaster. There's rules on this forum about politics, so I'll try and avoid getting up on the soap-box...
You probably forgot more than I've learned...
That, I actually understand...
Not necessarily. The doppler effect has effects that can be felt in real time (an airplane coming in for a landing, a train, etc), as well as other matters like the movement of other galaxies and things of that nature.
A wavelength is 360, so every half wavelength it travels, you'll get a cancellation of the signal as it's out of phase?
Meaning it's slightly overshot the target and is no longer heading towards, but heading away?
Don't worry, teaching and learning takes time.
yes and yes and yes.
The thing to appreciate about Butement design is that the electronics is scanning the space in front of the shell and around it every 100 microseconds or so, or every 33cm of advance down range. If the threshold is not reached in one sweep because the target is 34cm farther away than detectable then it absolutely will be within the next 33cm of flight. That I think gives you a Standard Error of about 15cm. Think about that. It is many many times better than a Norden or Sperry bombsight even at 15,000ft in ideal conditions. Approximately 1,000 times batter in the x, down range, dimension than AAA shellfire was otherwise in the y/z plane. Hell, 'smart' munitions today aren't that accurate.
So, because of that clever design every round that is on target explodes at the ideal distance +/- maybe 50 cm or 18 inches.The ideal distance for frag damage was about 70 ft or 21 metres (compared to 6 metres for shock wave damage).
21 metres +/-50cm. That's remarkable. And deadly.
Thank goodness the Germans didn't develop theirs. Only America had the production and engineering capacities to make that design work in artillery.
bbear
Airman 1st Class
[/QUOTE]I'm often perplexed, but that often drives me to learn stuff. Then I stop being perplexed. Until something else catches my curiosity anyway
So it emits a steady frequency tone?
Actually older people know more stuff, our education system (particularly in the United States) is a disaster. There's rules on this forum about politics, so I'll try and avoid getting up on the soap-box...
You probably forgot more than I've learned...
That, I actually understand...
Not necessarily. The doppler effect has effects that can be felt in real time (an airplane coming in for a landing, a train, etc), as well as other matters like the movement of other galaxies and things of that nature.
A wavelength is 360, so every half wavelength it travels, you'll get a cancellation of the signal as it's out of phase?
Meaning it's slightly overshot the target and is no longer heading towards, but heading away?
Don't worry, teaching and learning takes time.
best source yet - see chapter 9
VT Fuzes For Projectiles and Spin-Stabilized Rockets - OP 1480
