Japan shares it's cavity magnetron with German in 1940?

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T. A. Gardner
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Re: Japan shares it's cavity magnetron with German in 1940?

Post by T. A. Gardner » 21 Aug 2020 18:11

TheMarcksPlan wrote:
21 Aug 2020 01:09
stg44 wrote: Still German centimetric gunnery radar got it down below the 1942 best IIRC, which is a huge improvement over OTL rates.
What are the best sources on the development of German gunnery directors?
The electro-mechanical ones, or the radar sets?

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by TheMarcksPlan » 21 Aug 2020 20:43

T. A. Gardner wrote:
21 Aug 2020 18:11
TheMarcksPlan wrote:
21 Aug 2020 01:09
stg44 wrote: Still German centimetric gunnery radar got it down below the 1942 best IIRC, which is a huge improvement over OTL rates.
What are the best sources on the development of German gunnery directors?
The electro-mechanical ones, or the radar sets?
Both. Surely some/most of creating/transmitting a firing solution is independent of the detection apparatus.

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by T. A. Gardner » 22 Aug 2020 00:12

TheMarcksPlan wrote:
21 Aug 2020 20:43

Both. Surely some/most of creating/transmitting a firing solution is independent of the detection apparatus.
For the Germans, and for most fire control sets, radar was separate from the fire control computer and radar data was entered manually. The SCR 584 set, is one of the few exceptions to that.

Image

In all cases, WW 2 AA guns got aiming data from the fire control computer as well as fuze setting data. On every mount except the M2 90mm gun, this data was displayed electro-mechanically at the gun and the gun was then laid manually by the crew. On the M2, there was power on the mount and the gun could be laid remotely with the crew just supervising and loading the gun. The M2 was the only AA gun that had powered fuze setting and ramming on it too (much like some naval guns had).

The object in every case was to try and shorten the time between making an observation of the target and getting the gun laid and fired. The shorter this time lag was the more accurate the fire would be.

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by TheMarcksPlan » 22 Aug 2020 09:47

T. A. Gardner wrote:
22 Aug 2020 00:12
TheMarcksPlan wrote:
21 Aug 2020 20:43

Both. Surely some/most of creating/transmitting a firing solution is independent of the detection apparatus.
For the Germans, and for most fire control sets, radar was separate from the fire control computer and radar data was entered manually. The SCR 584 set, is one of the few exceptions to that.

Image

In all cases, WW 2 AA guns got aiming data from the fire control computer as well as fuze setting data. On every mount except the M2 90mm gun, this data was displayed electro-mechanically at the gun and the gun was then laid manually by the crew. On the M2, there was power on the mount and the gun could be laid remotely with the crew just supervising and loading the gun. The M2 was the only AA gun that had powered fuze setting and ramming on it too (much like some naval guns had).

The object in every case was to try and shorten the time between making an observation of the target and getting the gun laid and fired. The shorter this time lag was the more accurate the fire would be.
Thanks but can you list any sources? I have good library access...

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by stg 44 » 22 Aug 2020 13:21

I did find this:
http://www.cdvandtext2.org/ADI-K-Histor ... -Diehl.pdf
The "Egerland", which was devised for the flak and
comprised the "Kulmbach" panoramic device and the "Marbach"
firing installation, was a particularly successful development.
As regards target altitude and direction, its accuracy was
considerably greater than that of any other flak device and was,
in most cases, greater than one sixteenth of a degree. Moreover,
this installation had a panoramic range of 50 km, was able to
locate targets in rapid succession and could not be blanketed by
"Window".
And this link:
viewtopic.php?t=41495&start=240


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Re: Japan shares it's cavity magnetron with German in 1940?

Post by Carl Schwamberger » 23 Aug 2020 21:29

http://www.cdvandtext2.org/ADI-K-Histor ... -Diehl.pdf

The "Egerland", which was devised for the flak and
comprised the "Kulmbach" panoramic device and the "Marbach"
firing installation, was a particularly successful development.
As regards target altitude and direction, its accuracy was
considerably greater than that of any other flak device and was,
in most cases, greater than one sixteenth of a degree
. Moreover,
this installation had a panoramic range of 50 km, was able to
locate targets in rapid succession and could not be blanketed by
"Window".
Recalling my artillery gunnery training experience that 1/16 of a degree translates to slightly over one meter error at 1000 meters. A bit over eleven meters error at 10,000 meters range.

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by TheMarcksPlan » 25 Aug 2020 14:28

Carl Schwamberger wrote:
23 Aug 2020 21:29
http://www.cdvandtext2.org/ADI-K-Histor ... -Diehl.pdf

The "Egerland", which was devised for the flak and
comprised the "Kulmbach" panoramic device and the "Marbach"
firing installation, was a particularly successful development.
As regards target altitude and direction, its accuracy was
considerably greater than that of any other flak device and was,
in most cases, greater than one sixteenth of a degree
. Moreover,
this installation had a panoramic range of 50 km, was able to
locate targets in rapid succession and could not be blanketed by
"Window".
Recalling my artillery gunnery training experience that 1/16 of a degree translates to slightly over one meter error at 1000 meters. A bit over eleven meters error at 10,000 meters range.
Thanks for the sources. (Mr. Gardner as well).

Wonder what the gauge for error was. If that's 95% confidence interval then ~2/3 of aims would be within half that range (5.5m error), meaning a 128mm shell is usually aimed with sufficient accuracy to kill (fuse timing, shell dispersion, and target maneuver being additional confounding factors). 88mm shell would usually be aimed to kill about ~1/4 of the time (given ~3m lethal radius).

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by T. A. Gardner » 25 Aug 2020 15:16

With radar the error is determined against known targets as they appear on the display. It could also be calculated using the wavelength of the set versus the size of target being detected. It is sort of like bore sighting a gun only done electronically. In the era of vacuum tubes, these values would drift some as the set was used so the more skilled the operator the closer they could get the set to make accurate detections.

A lot of this has to do with the wavelength of the radar. In the cases of Egerland and Kulmbach, these went from about 54 cm where Würtzburg was operating to 10 to 3 cm or an increase in accuracy of 5 to 15 times. The only reason these sets were unaffected by Window was the US and Britain didn't drop chaff that would be effective against radars on that wavelength. Had they known the Germans were using such sets regularly, they would have shifted the size of the chaff dropped to include half dipole lengths of 1.5 to 5 cm which would have been effective.

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by stg 44 » 26 Aug 2020 02:18

TheMarcksPlan wrote:
25 Aug 2020 14:28
Carl Schwamberger wrote:
23 Aug 2020 21:29
http://www.cdvandtext2.org/ADI-K-Histor ... -Diehl.pdf

The "Egerland", which was devised for the flak and
comprised the "Kulmbach" panoramic device and the "Marbach"
firing installation, was a particularly successful development.
As regards target altitude and direction, its accuracy was
considerably greater than that of any other flak device and was,
in most cases, greater than one sixteenth of a degree
. Moreover,
this installation had a panoramic range of 50 km, was able to
locate targets in rapid succession and could not be blanketed by
"Window".
Recalling my artillery gunnery training experience that 1/16 of a degree translates to slightly over one meter error at 1000 meters. A bit over eleven meters error at 10,000 meters range.
Thanks for the sources. (Mr. Gardner as well).
He was quoting my post.
TheMarcksPlan wrote:
25 Aug 2020 14:28
Wonder what the gauge for error was. If that's 95% confidence interval then ~2/3 of aims would be within half that range (5.5m error), meaning a 128mm shell is usually aimed with sufficient accuracy to kill (fuse timing, shell dispersion, and target maneuver being additional confounding factors). 88mm shell would usually be aimed to kill about ~1/4 of the time (given ~3m lethal radius).
Assuming a 4 gun battery, which was usually not the case by that point in the war IIRC, they had more 88s than that per battery, that should saturate a wide enough area to 'cover the spread'.
T. A. Gardner wrote:
25 Aug 2020 15:16
With radar the error is determined against known targets as they appear on the display. It could also be calculated using the wavelength of the set versus the size of target being detected. It is sort of like bore sighting a gun only done electronically. In the era of vacuum tubes, these values would drift some as the set was used so the more skilled the operator the closer they could get the set to make accurate detections.

A lot of this has to do with the wavelength of the radar. In the cases of Egerland and Kulmbach, these went from about 54 cm where Würtzburg was operating to 10 to 3 cm or an increase in accuracy of 5 to 15 times. The only reason these sets were unaffected by Window was the US and Britain didn't drop chaff that would be effective against radars on that wavelength. Had they known the Germans were using such sets regularly, they would have shifted the size of the chaff dropped to include half dipole lengths of 1.5 to 5 cm which would have been effective.
I wonder how much it would impact how much chaff could be carried if they had to cover the entire spectrum between the Würzburg and Marbach systems (the combined system of Egerland and Kulmbach).

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by T. A. Gardner » 26 Aug 2020 03:47

Chaff is very light. The shorter the wavelength the lighter is is per piece. For metric wavelengths like CH or Freya you use "rope" chaff.

Image

The centimetric sets at 10 cm and less looks more like this

Image

There were also active countermeasures to jam radar and by 1944 most bombers were carrying sets. This was often enough to overwhelm defending radar sets with noise jamming.

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by Carl Schwamberger » 26 Aug 2020 04:26

TheMarcksPlan wrote:
25 Aug 2020 14:28
...
Wonder what the gauge for error was. If that's 95% confidence interval then ~2/3 of aims would be within half that range (5.5m error), meaning a 128mm shell is usually aimed with sufficient accuracy to kill (fuse timing, shell dispersion, and target maneuver being additional confounding factors). 88mm shell would usually be aimed to kill about ~1/4 of the time (given ~3m lethal radius).
Whats missing from the basic calculation of firing point to target/sim point is the metrological correction. Crosswinds at different altitudes, variable wind velocities, difference in air density (barometric pressure), humidity or moisture density. In the field artillery calculating all that by hand (54 steps) or digitally from a Metrological observations was problematic. When we could get radar generated data the corrections had a lot more utility. But, until then the 'shoot and adjust' method was a necessary supplement as the Metro data degraded after time of observation. In extreme cases corrections of 3,000 meters at 15,000 meters range were necessary due to metrological variants. More commonly deviations from the standard conditions the firing tables were based on would result in 10 to 50 mill deviation from point of aim to point of impact. At 10,000 meters range a 10 mil error = 100 meters off target. Corrections of 100+ mil were not uncommon from the meteorological conditions.

One of the more critical Met corrections was temperature of the air, or more specifically the propellant charge. It was the one item we could track at the firing position, with a thermometer stuck in the propellant bags, and correct for in a timely manner. With the slow RoF of our howitzers & the considerable heat sink of the barrel/breach overheating was not a large problem. When the breeches did become superheated the concern was with premature ignition of the propellants & not its effect of muzzle velocity/range error. I don't know if significant MV changes occurred with sustained fire of WWII AA cannon, or if there was a accurate method of correction.

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by T. A. Gardner » 26 Aug 2020 05:28

The biggest error input into the system was that the fire control system was slow in calculation and second that the time between fuze setting and firing. A faster and continuous calculation fire control system helped but there was still a lag between data input and calculation output of as much as 30 seconds. Electro-mechanical systems were just slow. It doesn't help if the enemy is not flying a steady course and altitude.

Then there's fuze setting. On almost all WW 2 heavy AA guns this was done by the loaders well ahead of loading. There could be several shells with fuzes set waiting for loading. The US on the M2 90mm tried to alleviate this by using a power rammer and automatic fuze setter that set the fuze just before ramming it home for firing.


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Re: Japan shares it's cavity magnetron with German in 1940?

Post by TheMarcksPlan » 26 Aug 2020 15:07

Carl Schwamberger wrote:
26 Aug 2020 04:26


Whats missing from the basic calculation...

I don't know if significant MV changes occurred with sustained fire of WWII AA cannon, or if there was a accurate method of correction.
Good points.

I'd guess there were fairly significant changes in MV due primarily to barrel wear. Barrel life was ~900 rounds so 20min of firing at 15/min would take up 1/3 of expected life.

BTW - does anyone have figures on the cost of barrel/liner replacement for Flak? Westermann's Flak gives no figure IIRC, so it must be a little obscure.

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Re: Japan shares it's cavity magnetron with German in 1940?

Post by Carl Schwamberger » 27 Aug 2020 21:49

Barrel wear can be corrected for calculating the aim. Running a gauge through the barrel after cleaning gives you a number to apply to a correction table. By the 1980s we had a radar set strapped to the barrel that gave us real time MV/correction :)

I recall LeMay was at odds with the doctrinal allowance for time of the final bomb run. When he took command of 8th AF bombers he felt the 60 seconds or less allowed the bombardiers for the final straight and level aiming run was unnecessarily short. The bombardiers could not cope with the demands of the Norden sight in that short of time. As a former artillery officer LeMay thought the FLAK was simply not as accurate as allowed and had his staff collect data on US and capture German AA cannon. He argued that showed the Probable Error from point of aim much larger than estimated & increasing the 'straight run' time for the bombardier to two minutes or more justified.

Anyone have any literature on this from the US AAF, 8th AF or other sources?

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