Rheinmetall Fuze Condensers

[Bellifortis]

For quite some time I try to understand the the workings of the old Rheinmetall fuze condensers. It bugs me, that I'm not able to understand a nearly 100 years old anachronistic technology. I know near to nothing about electronics. I searched the internet, Wikipedia a.s.o., but I found no answer anywhere. Attached are photos of the El.AZ. (25)D condenser roll and a picture of the 25C model wiring diagram, which is supposed to be the same as the D model. There are 6 condensers in the diagram. I suppose that one condensers is rolled up on top of the other. How are they seperated ? In the fotos you see the 0,1-0,05mm thick and 6mm wide tincoated contact strips attached to the surface of the condenser roll. I count 7 strips. The attached connecting wires all come out at the top. At the bottom the strips are folded down and disappear between the folds of the rolled up foil. I'm told that condensers don't have plus and minus poles and that the capacity only depends on the surface earea of the metal foil. I don't know if there ever has been any other use of such condensers rolled one on top of the other besides this use in electric fuzes. Is there anybody here on the net who can explain, in a laymens language the construction and working of these old fuze condensers.
Thanking you in advance for any input,
Bellifortis.

 

[Fusse2004]

Hallo Bellifortis! Kaufe dir mal das Buch von Peter Vo - Die Deutschen Bombenznder - darin werden alle deine Fragen beantwortet. Gru Harry

 

[pzgr40]

Hi Bellifortes, you are right. It is not one condenser, but six condensors rolled around one another. They are devided from one another by tar coated paper between the rolls The capcity is descides by the number of revolutions per roll. The condenser exists of tin foil sheet , tar coated on one side to enshure electric insulation between the revolutions.
I made a few posting about German bom fuzes:

http://www.bocn.co.uk/vbforum/threads/4054-El-A-Z17(Electrische-Anschlag-Znder-17-)-Germany

http://www.bocn.co.uk/vbforum/threads/4055-El-A-Z-38-Electric-impact-fuze-Germany-WW2

http://www.bocn.co.uk/vbforum/threads/4051-El-A-Z-57-German-WW2-Electric-impact-fuze

http://www.bocn.co.uk/vbforum/threads/4056-El-Zt-Z-9-Electrical-aerial-burst-fuze-No-9


Maybe they are of any help.

Regards, DJH

 

[Bellifortis]

Hi DJH,
thank you for your answer. By the way I'm a big admirer of your beautiful handwork since nearly 2 decades. Some time ago already I had some enlargements printed of the nice fotos in the 4 links above. You have answered my question about the electrical isolation partition between the rolls. I assume that the electrical charge is communicated and tapped via the bent around at the bottom, thin tincoated copper strips to which the connecting wires are fastened and exit at the top. I assume that this 0.1-0.05 thin metalstrips are just inserted inbetween 2 revolutions during winding of a coil of one condenser. Does it matter if they contact a condenser roll at the beginning, the middle or the end ? The room available to a set of condensers is always the same. I have added up the sums of capacities of all condensers in the different models. The lowest is the (17) and the (49)B3 with 1,0 microfarad and the highest the (15) with 2,4 microfarad. In the cut models I have seen, the size of the complete roll always seems to be the same. One other thing I want to ask you : Do you have a detailed picture of the double ball transverse vibratory switch found in (15) and early (25) and the single ball vibratory used in the (50) and the inertia bolt switch from the (28)B. I have never seen one and only know these from the literature.
With kind regards,
Bellifortis.

 

[Harvey]

Hi Bellifortis,

The easiest way to imagine what a condenser does in these circuits is to think of it as a very fast charging rechargeable battery. When a voltage is applied to the two foils separated by a non conducting 'dielectric' then the electrical energy is stored between the foils as an electrical field. The exact dynamics of this depends on the materials used, and which foil is positive and which is negative is determined by the applied voltage. The actual connection point of the wires is irrelevant.

The Rhinemetall fuses use plungers with insulating rings to allow the aircraft electrical system to store an initial voltage in the primary condenser (charging the battery) and when the fuse cap is pulled off, the plungers connect the condenser to the rest of the circuitry (discharging the battery). From what I have seen of the circuit diagrams, the firing condensers are charged from the primary condensers through a resistance. This provides a delay (a larger resistance providing more delay) until the firing condensers to reach the voltage required for the glow wires to initiate the firing train, so they are well clear of the aircraft before becoming armed.

The practice of wrapping the condensers around each other should have no influence upon the charge in the individual condensers given the relatively short times they are charged for before being destroyed. This design is more likely an efficient use of space than anything else.

 

[Bellifortis]

Hi Bellifortis,

The easiest way to imagine what a condenser does in these circuits is to think of it as a very fast charging rechargeable battery. When a voltage is applied to the two foils separated by a non conducting 'dielectric' then the electrical energy is stored between the foils as an electrical field. The exact dynamics of this depends on the materials used, and which foil is positive and which is negative is determined by the applied voltage. The actual connection point of the wires is irrelevant.

The Rhinemetall fuses use plungers with insulating rings to allow the aircraft electrical system to store an initial voltage in the primary condenser (charging the battery) and when the fuse cap is pulled off, the plungers connect the condenser to the rest of the circuitry (discharging the battery). From what I have seen of the circuit diagrams, the firing condensers are charged from the primary condensers through a resistance. This provides a delay (a larger resistance providing more delay) until the firing condensers to reach the voltage required for the glow wires to initiate the firing train, so they are well clear of the aircraft before becoming armed.

The practice of wrapping the condensers around each other should have no influence upon the charge in the individual condensers given the relatively short times they are charged for before being destroyed. This design is more likely an efficient use of space than anything else.

Hi Harvey,
thank you for your answer. I do understand the workings of the fuze. What I have problems with is the basic understanding of the workings of this old style rolled papercondenser sets. I searched the net for the basics : 1745 Leiden flask, 1775 Voltaic pile and 1897 Charles Pollack's patent on which all later condensers are based, but nowhere could I find a description of these 1930s rolled papercondensers. Referring to my original post, there are 6 condensers rolled one on top of the other. There are 7 of the 6mm wide tincoated copper connecting taps to which the connecting wires are soldered. I assume that the 7th tab is a common ground connection, as in the diagramm you see that all condensers are connected to ground. The fuze is charged with DC voltage, so there has to be a plus and minus side. The minus apparently is the casing of the fuze to which the 7th tab must be connected. How is that 7th tab safely connected to all 6 condensers without ever touching the +. In his biography Herbert Ruehlemann, the inventor, mentioned this problem occuring 1 time with 1 lot of another manufacturer. A plane blew up in the air in Russia when the pilot flipped the switch to drop his bombs. Sorry, I know that most people here are not interested in old paper condensers, so excuse my rantings. To show you something interesting I have attached a photo of one of the different models of the charging gear for the fuze that was attached directly to the weopons station of the plane.
Greetings,
Bellifortis.

 

[Harvey]

Hi Bellifortis,

It seems to me that it is down to careful manufacturing. As there is a common ground potential shared by all six condensers, these will be mechanically connected together to allow electricity to flow between them and keep them all at the ground potential. This is probably via the metal strips that disappear into the coils. If these are not electrically isolated from the other foils, then a short circuit will bypass the condensers which could lead to the primary charging voltage being applied to the glow wires and the catastrophic results you described.

I'm no expert in the way these coils were manufactured, but I would suggest that the strips which re-enter the coil probably have an insulating coating on the inside to prevent a short circuit between the different foils.

Regards,

 

[Bellifortis]

I reread the chapter about the accident that happened in the spring of 1942 in the designers book. When asked by General Marquardt of the airforce if such a thing could happen with Rheinmetall electric fuzes, H.Ruehlemann thought it technically impossible, as there is a 40 megaohm resistance placed between the charging and firing condensers. Within 2 weeks of the accident the lot of fuzes were shipped back from the depot in Russia to Smmerda and investigated. They had been produced by "Sachsenwerke" which used condensers made by the largest condenser producer at the time "Hydrawerke". Both of this factories were subsidiaries of AEG. The condensers used by Rheinmetall were produced by Siemens (the developer of these condensers) or made in Smmerda directly. In the original design the + and - wires were placed on opposite sides of the condensers. Hydrawerke changed this for more easy production and placed the wires just a few windings apart. This created a small inductive coupling between charging and firing condenser, which sometimes (not allways) was sufficient to ignite the very sensitive squib.
Regards,
Bellifortis.