German Remote Controlled Turrets

Discussion in 'Aviation' started by SpicyJuan11, Jun 10, 2015.

  1. SpicyJuan11

    SpicyJuan11 Member

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    Hello, could somebody please give me a quick run-down of German remote-controlled turrets and how they worked? I heard that they were different from the B-29 (as it had a fire-control computer of sorts) but closer to the A-26 Invader which used periscopic sites (like in German aircraft).
     
  2. davebender

    davebender Well-Known Member

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    Available on this site. It provides a description of Me-210 remote control barbettes.
     
  3. SpicyJuan11

    SpicyJuan11 Member

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    What site Dave? You didn't seem to link one. But I was thinking mainly of the remote turrets like the FDL system on the Ju 288, not barbettes.
     
  4. Koopernic

    Koopernic Active Member

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    #4 Koopernic, Jun 10, 2015
    Last edited: Jun 10, 2015
    This is an interesting topic: the Whole "Bomber B" program such as the Junkers Ju 288, Focke-Wulf Fw 191 and Dornier Do 317 are intimately connected with the use of remote controlled turrets. Technical problems with them as early as 1941/42 was perhaps as stressful to the decision makers as suitable engines. A remote controlled tail gun in the Ju 88S in 1942 might have given the Germans an excellent bomber.

    Most if not all the German systems were hydraulic.

    1 Me 210/410; the rear observer/gunner had 3 reflector sighs, one to the left, a central one and a right had one. There were attached to a pentagram mechanism and so moved in unison, the observer chose the one that suited best.
    Moving the 'sight' opened a 3/5 valve (the spool ie the valve blade itself) this operated the hydraulic jacks or motor that deflected the guns. A second mechanical mechanism connected to the gun mounts then moved the body of the valves (relative to the spool which was only connected to the sight) so that when the guns were in position the flow was closed of, this was 'negative feedback' by mechanical means.

    Note the sighting bulges on this Me 210C long which has MG81 rifle calibre guns, MG131 13.2mm guns were eventually fitted on the 410.
    26-2.jpg

    At leas one Russian web site claims that Soviet tests revealed that some kind of computing mechanism compensated for wind speed in deflecting the bullets though gyro sights don't seem to have been installed.

    Experience had shown that gunners in the Me 110 were unable to aim their guns accurately due to g forces nor were they able to replace magazines due to those forces. Hand driven guns only worked in bombers not a relatively agile aircraft as the Me 110.

    The Arado 240/440 broadly used similar hydraulic technology except that they used an dorsal/ventral turret that was aimed via a U-boat style periscope that switched between upper and lower view. This worked quite well as the vision through the periscope was better than through a reflector sight through armour glass and furthermore the sight head was in an optimal position to avoid interference with aircraft structures.

    The Ju 288 and 388 tail gun worked through hydraulic technology, the 'negative feedback' for the tail turret was fed back via gear boxes and long shafts from tail to the gunners position where the valve was. However one difference was that the head of the sighting periscope was moved via a separate feedback mechanism (gear driven shafts) from the guns themselves rather than the gunner directly to ensure the guns and periscopic sight were always aligned. The spool valves were machined to be open in both directions by 30 microns so that the hydraulic lines were pressurised and 'expanded' prior to any movement so that there would be no lag. That's precision.

    The He 177 seems to have been all hydraulic and I believe the chin turret of some He 177 was hydraulic as well. (He 177 crew size was the same as a B-26 or He 111).

    A electrohydraulic system was also developed which used a purely electrical system of transmitting aiming commands to the turret but I don't believe it was used on the He 177 (may have been on latter versions).

    bvp144-2.gif

    What is going on here electrically is that the devices attached to the sight are "synchros" which create a AC voltage proportional to the deflection of the sight, this is subtracted electrically from a similar synchros in the guns themselves. The difference is converted from an AC voltage via a phase sensitive rectifier to DC voltage which is used to open an electrohydraulic valve (think of it as a DC motor operating a valve). The reason that a phase sensitive rectifier is used is that 180 or -180 degree phase of the AC voltage (nothing in between) is used to represent positive or negative deflections in DC.

    The amplifier boxes, labelled as being 7kg, could in theory contain computing mechanisms to add in deflections to compensate for projectile fall off, air speed, air density, target lead and parallax much as the GE system in the B-29 did. However the most convenient place to some of these would be within a gun sight itself.

    The amplifier systems to control deflections were essentially naval gun turret practice transferred to aircraft. This German system of technology became very fast and was also used to control V2 exhaust gas fins that stabilised the V2 during launch.

    The US was highly successful in developing all electric turrets due to the perfection of the 'amplidyne' in the USA. The Germans might have achieved all electrical system via their own technology of the magnetic amplifier but they tended to reserve this for stabilisation of optics probably due to use of copper and nickel.
     
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  5. SpicyJuan11

    SpicyJuan11 Member

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    Thank you Koopernic for the taking the time to detail it all out so well.
     
  6. SpicyJuan11

    SpicyJuan11 Member

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    Could you please provide a link/source on the difficulties they had during the Bomber-B program with the remote turrets? I have the book Ju 288/388/488 and it continually states the issues with the Bomber B was the engines, and not the turrets.
     
  7. Augsburg Eagle

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  8. SpicyJuan11

    SpicyJuan11 Member

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    #8 SpicyJuan11, Jun 11, 2015
    Last edited: Jun 11, 2015
  9. SpicyJuan11

    SpicyJuan11 Member

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    Quick question: How did the German's overcome the parallax issues with the turrets, if at all?
     
  10. Capt. Vick

    Capt. Vick Well-Known Member

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  11. Koopernic

    Koopernic Active Member

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    #11 Koopernic, Jun 19, 2015
    Last edited: Jun 19, 2015
    In the General Electric system used in the B29 the sight was aimed from within the sighting blister. The optics was sighted through the Perspex of the blister.

    Most of the planned German systems still had a sighting blister but they used a periscope for aiming and that periscopes sighting head was near the turret thereby eliminating the parallax issue. The periscope that was to be used on the Me 264 was called the PVE 6 and supplied by Arado.

    One saw service in small numbers on the Ar 240/440.

    Aiming through a periscope is actually better for night vision and accuracy than aiming through a Perspex blister.

    The electrical GE system on the B-29 had a electromechanical computer full of servo motors, differential gears and various camshafts that could add in all sorts of corrections to compensate for such things as air speed, air density, target motion, projectile fall and of course parallax. The B-36 didn't have parallax as the gunner was seated close to the gun.

    The Germans did develop and electrohydraulic gun turret but I think now that even the Me 264 system was controlled hydraulically via mechanical linkages. hard to tell.
     
  12. SpicyJuan11

    SpicyJuan11 Member

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    Thanks again Koopernic, but sorry for wasting your time, as you first post already answered my question:oops:
     
  13. Frantish

    Frantish Member

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    Good stuff! Thanks for thread on it!
     
  14. SpicyJuan11

    SpicyJuan11 Member

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    Koopernic, what's your source for the Arado 240's defensive armament working well? I have a few snippets here from "Die Deutschen Flugzeugbewaffnungen bis 1945" by Manfred Griehl,and he states on page 77 that it was not accurate enough.
     
  15. Koopernic

    Koopernic Active Member

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    The "German Fighter 1914 to 1980" by Rudiger Kosin.

    Both the Me 410 and Ar 440/240 hydraulic turrets worked well, however both experienced delays in solving the accuracy problem. In the end they worked and worked well.
     
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  16. SpicyJuan11

    SpicyJuan11 Member

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    Huh ok, thanks for the info Koopernic, Griehl does seem to be sparse at times. I have a few more questions, but I've been traveling lately and I have very poor connection so I can't access the book all too often.
     
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