User:MinorProphet/Draft subpages/WW2 ZF gearboxes

ZF SSG 77 gearbox and final transmission with Panzer III in the background

Top view of the SSG 77, cover removed

Oi! GET ON THOSE SFNs!

NB! From 1 October 1938, all engines had to be able to use 74 octane (OZ 74). (Pz. Tr. 22-1-8)

See also: User:MinorProphet/Draft subpages/WW2 Maybach gearboxes

This is an incomplete list of gearboxes (German: Schaltgetriebe) made by ZF Friedrichshafen (ZF) before and during World War 2 and fitted to various military vehicles used during the war, including tanks, tank hunters, self-propelled artillery and assault guns, half-tracks, armoured cars (Sd.Kfz. 247 Ausf.A), artillery tractors (eg SWS, ?Maultier?) and other soft-skinned transport vehicles (e.g. Krupp Protze).

ZF designed and made gearboxes for most German AFVs and prime movers used before and during World War II, in conjunction with its sister company Maybach, who made the engines and some gearboxes: both were subsidiaries of Luftschiffbau Zeppelin, all based in Friedrichshafen.

The 'G' and 'ZG', models (without synchromesh) were fitted to half-tracks; and the rest ('FG', 'SFG', 'SSG', and 'AK' models, all with synchro on most gears) were fitted to tanks and various self-propelled guns, tank hunters etc. based on tank chassis.

All the gearboxes described in this article and in the tables below are of the manual, constant-mesh, 'Aphon' type (from Greek, meaning "noiseless") using helical-ground gears (except for reverse) even if not expressly indicated. They were produced in both synchromesh and non-synchro models.

While manufacturing large quantities of gearboxes for production-series tanks and half-tracks, ZF also made a number of experimental or test designs which never reached the mass production stage. Both these types are listed in the tables below.

History

Founding of ZF

Zahnradfabrik Friedrichshafen GmbH (ZF) was formed in September 1915 as an offshoot of two existing companies, Luftschiffbau Zeppelin GmbH of Friedrichshafen and Max Maag Zahnradfabrik of Zürich (later Maag-Zahnräder AG), to make gearboxes for Zeppelin airships.

The head of the testing department at Zeppelin was Alfred von Soden-Fraunhofen (21 November 1875–14 June 1944), an engineer and designer who had previously worked at Daimler AG and MAN. He had become acquainted with Graf von Zeppelin while holidaying in the area, and was offered the newly-created position in 1910. He was involved with testing the LZ 6 and LZ 7 in 1910 after the LZ 5 crashed and burned. (See List of Zeppelins.) Soden and Claude Dornier, also employed by Zeppelin, wrote a report together on airship drag in 1911. In search of high-quality gear mechanisms, von Soden contacted Max Maag, a Swiss engineer who in 1913 had started his own factory in Zürich to make precision ground helical gears.

Count Zeppelin prompted Alfred Colsman, managing director of Luftschiffbau Zeppelin GmbH (LZ), to propose a new independent company based in Friedrichshafen, which was founded in 1915 as Zahnradfabrik Friedrichshafen GmbH, a limited liability company with von Soden as managing director. By 1918 the company had 600 employees, which had fallen to 570 in 1920.

Inter-war period

The harsh terms of the Versailles Peace Treaty forbade all military activity and manufacturing, and ZF turned to making gearboxes for passenger vehicles. The general post-war depression threatened bankruptcy, and the firm was re-financed and incorporated as Zahnradfabrik Friedrichshafen AG (stock corporation) in May 1921, with LZ (Luftschiffbau Zeppelin) as the major stockholder. Theodor Winz was the first managing director with Soden as technical director, heading the department for almost 30 years until his death from previously diagnosed leukaemia in 1944. Soden was deeply religious, and never joined the NSDAP.

After the rise to power of the NSDAP regime in 1933, the manufacture of military vehicles began again in earnest, and many other German manufacturers manufactured their own engines and gearboxes: but by 1936 the gearboxes for the majority of all tanks and half-tracks were designed and made by ZF, with the engines made by Maybach, another offshoot of Zeppelin also based in Friedrichshafen. ZF and other firms were licensed to make Maybach-designed semi-automatic gearboxes, eg the SRG 32 8 145 for the Panzer III Ausf. E–G.

However, the motor industry in Germany during the 1930s was not well developed. There was very little mass-production using assembly-line methods common in the US. Motor cars (Personenkraftwagen, Pkw) were only owned by approximately one per cent (1%) of the population, including businesses, government and richer private individuals. The motor industry was small-scale and scattered over thousands of individual businesses. Approx 90% of all goods travelled by rail, and another 8.5% was carried by trucks (Lastkraftwagen, Lkw). The most common mode of personal transport was the motorcycle.

Soden gearbox

The Soden transmission (Soden-Getriebe), a pre-selector, semi-automatic gearbox, was invented in 1921 by Alfred von Soden of ZF. It was fitted in passenger cars, light trucks, and also in the Leichttraktor, the forerunner of the Panzer III tank.

It was shown to the public on 23 September 1921, at the first Berlin Motor Show since the war. This gearbox represented a feat of engineering that was far ahead of its time. A series of pre-series (Vorserienstand) gearboxes had already been launched in Vienna in October 1920, aimed at taxis, light trucks and buses. The range included types S2.5, S3, S3.5, and S4 for passenger cars (Pkw, Personenkraftwagen) and type S5L for trucks (Lkw, Last\kraftwagen) A version for railway locomotives, Typ TS18.5, had 5 forward and 5 reverse gears.

ZF only made one model of this type of pre-selector, semi-automatic gearbox for a military vehicle, the 6 EV 75. It was Maybach (its sister company) who pursued the design and development of this type of relatively complex and (at the time) uncommon gearbox, and produced the great majority of types. ZF also made a single model of prototype electromagnetic gearbox, the K 12 E, which was not put into full production.

In 1925 ZF introduced the Einheitsgetriebe or 'Standard Transmission' series which consolidated and rationalised ZF's gearbox production down to a few structurally similar designs, with varying maximum torque capacities.

History: Leichttraktor

The forerunner to the Panzer III, the Leichttraktor of c1930 made by Krupp, used a Soden transmission with 4 forward gears and 1 reverse. Changing gears was effected in two separate stages. First, the driver (anticipating the terrain ahead) moves a small pre-selector lever in a fore-and-aft quadrant into the desired slot. Nothing obvious happens. Secondly, when the new gear is needed, the driver depresses the clutch pedal for a full second. Inside the gearbox, a pre-selected piston at the top of the gearbox moves a selector fork within the gearcase to physically change gears on the shaft; the piston is held in its locating hole by spring pressure. The driver then releases the clutch pedal, and travel continues smoothly and uninterruptedly in the new gear.

When changing gear while climbing a gradient, it was important to keep hold of the steering wheel while turning; before reversing; or in a moment of danger.

Apart from the Soden transmission used in the Leichttraktor, it doesn't seem that ZF actually made any quantity series production gearbox of this type for military use, except the ill-fated EV series with electromagnetic clutches, fitted to around 100 Swedish Stridsvagn m/42 tanks. In general, ZF made conventional, manual gearboxes, and Maybach made the more complex semi-automatic ones.

'Aphon' gearbox

In 1928 ZF introduced the 'Aphon' transmission (Greek for "without noise" or "noiseless"), a constant-mesh gearbox with helical-ground gears for passenger vehicles. It eliminated the inherent whine of straight-cut gears. See also § Overview of gearbox types below.

The Aphon was designed by Albert Maier (1899–1983). Maier graduated from Konstanz Engineering school and joined ZF in 1922, later becoming an engineer in the Design Office/Department. Soden and Maier designed the AK 7-200 gearbox for the Panther. See also Maier also designed ZF's only car, the post-war two-seater Champion with 200cc supercharged 2-stroke lawnmower engine with 3+1 speed gearbox. One of the managers of ZF after the war. Collector of medieval arms and armour.

These first Aphon car transmissions also featured synchromesh (except 1 & R). Transmissions with full synchro on all gears for passenger vehicles such as the AK 4 S series (marketed as Panaphon) appeared in 1934. The AK 4 S 15 was fitted in the BMW 327 from 1936/7 to 1941. The (world's) first full synchro gearbox for commercial vehicles appeared in 1957, e.g. the ZF S 6-55 etc. - ha! see Getriebe-Fibel.

NB! Find Spielberger's use of Schubgetriebe (abbreviated to 'Schub-') which he appears to use in referring to non-synchro transmissions. Somewhat misleading, since the German term appears refers specifically to an old-fashioned sliding-mesh gearbox.

Nomenclature

ZF's gearbox model identification system generally consists of one to three letters (e.g. G, FG, SSG), followed by a number indicating the gearbox's approximate maximum torque capacity in kilopondmeters (abbreviated in contemporary documents as mkg or mkp.)

For example, 'SFG 75' stands for Synchronisiert Funf-gang Getriebe (synchronised five-speed gearbox), with an approx. maximum torque capacity of 75 mkg. See also § Torque section.

The numbering of the 'AK' series explicitly includes the number of forward gears and maximum torque, e.g. AK 7-200.

Although all the ZF half-track transmissions included a range reduction gearbox (sometimes called 'hi-lo', or 'crawler' box) either separate or integrated within the casing (resulting in 8 forward and 2 reverse speeds), this is ignored in the model number.

Half-tracks

Both types of the production half-track gearboxes are manually operated and without synchro, having four forward speeds and one reverse, coupled with a hi-lo range box (or 'crawler box') (not included in the designation) to give a total of 8 forward speeds and 2 reverse, abbreviated in this article as (4+1 x 2).

• G = Getriebe, Four forward + one reverse gears, non-synchro. 'Semi-unit' construction with factory-fitted clutch. Two casings are bolted/flanged together: clutch and hi-lo box casing at the front; and main change-speed box in the rear casing (i fink). Fitted to half-tracks with Maybach HL 'TU' type engines (e.g. HL57 TU in the Sd.Kfz. 7 KM m9) - NB The exception is the clutchless G65 in the Sd.Kfz. 9.
• *ZG = Z-Getriebe (Zug-Getriebe??) Four forward + one reverse speeds, non-synchro, no factory-fitted clutch. 'Unit' construction with both speed change and hi-lo mechanisms within the same casing. Fitted to half-tracks with Maybach HL 'TUK' engines (e.g. HL62 TUK in Sd.Kfz. 7, KM m11) An exception is the ZG 35 fitted in Krupp's export tanks L.K.A and L.K.B. (using a Krupp V-8 engine) which had synchro on at least the first two gears, and a single plate clutch.

Tanks

All the series production gearboxes for German tanks made by ZF (including other full-tracked vehicles based on tank chassis, such as self-propelled artillery, tank hunters, assault guns etc.) have five, six or seven forward gears, with synchromesh (except reverse).

• FG = Funfgang Getriebe, five forward gears + one reverse, (synchro on gears 2, 3 and 4 only REALLY?)
• SFG = Synchronisiert[er] Fünfgang Getriebe, Synchronised Five-gear Gearbox (synchro on all gears except 1 & R)
• SSG = Synchronisiert[er] Sechsgang Getriebe, synchronised six-gear transmission
• AK = All-Klauengetriebe (German: Klaue = (tech.) "dog clutch" "claw", an internal mechanism for shifting gears.) See also #General overview of gearbox construction. The AK series (whether series production or not) have the number of gears and max. torque stated explicitly in the model number. The AK 7-200 had seven forward gears, the non-production AK 5-80 had five forward gears, and the AK 6- series had six.
  • ZF had earlier produced a series of 4-speed manual gearboxes with synchromesh on all gears in 1934, the AK 4 S. The AK 4 S 15 was fitted in the BMW 327 from 1936/7 to 1941.

Other tank gearboxes:

• EV (6+1) - Electromagnetic gearbox with synchromesh, fitted to Swedish Stridsvagn m/42 tanks. Seen as very unreliable (due to poor quality steel in manufactured internal clutch plates, perhaps not the basic design...)
• SMG = ?? This was a series of experimental, non-production gearboxes. For example, the SMG 90 had eight forward gears and possibly semi-automatic operation.

With the exception of the last two gearboxes above, it appears that all of the transmissions which ZF produced for installation in German tanks, halftracks and other military vehicles were manual: all the pre-selector, semi-automatic gearboxes fitted to some German tanks and the Sd.Kfz. 10 etc. as mentioned above, were designed by Maybach (their SRG, VG, & OG series), with some made under license by ZF and others.

Good website about the Panzer IV: Panzer IV Universe with lots of refs.

Lists of ZF gearboxes

Zahnradfabrik Friedrichshafen (ZF) designed and produced the gearboxes for the vast majority of German tanks and half-tracks, shown in the tables below.

Almost all the tank gearboxes included a clutch as standard, as well as some of the half-track ones (e.g. for many Sd.Kfz. 6 variants.) The ZF SSG 76 and 77 with clutch were fitted to the Panzer III Ausf. D–G and Ausf. H-N. Between these two series, the semi-automatic Maybach SRG 32 8 145 was used in the Panzer III Ausf. E–G. Maybach's own modified clutch was fitted at the factory, and thus the Maybach HL108 TR and HL120 TRM engines could be ordered from the manufacturer with or without a clutch, depending on the gearbox.

Half-track gearboxes with no clutch included the ZG 55 fitted to late models of the Sd.Kfz. 7, and the G 65 VL230 in the Sd.Kfz. 9; they were paired with a Maybach TUK type engine, where the 'K' always indicates a factory-fitted clutch.

Exceptions

Tanks etc. which did not use a ZF gearbox included the Panzer II Ausf. D & E, which used a pre-selector, semi-automatic, Maybach SRG 14 4 79 (7+1); the Panzer III Ausf. E-G which used the troublesome Maybach SRG 32 8 145 (10+1); and production models of the Tiger I, Tiger II and derivatives, which used the Maybach Olvar OG 40 12 16 (8+4).

Half-tracks which did not use ZF gearboxes included the Sd.Kfz. 10 and Sd.Kfz. 250, fitted with the pre-selector, semi-automatic Maybach VG 102 128H (7+3); and all Sd.Kfz. 11s and Sd.Kfz. 251s, which used Hanomag's own manual 4+1 x 2 gearbox design. Ref, dude?

Table 1 - Series production ZF gearboxes

List of ZF WWII series production gearboxes

Model number	Type	Max. Torque	Gears	Application	Engine
G 25	G	25	4+1	Pre-war Mercedes, Opel, Wanderer	various
G 35	G	35	4+1 x2	Pre-war Mercedes-Benz G3A 6x6 military truck	Daimler-Benz M09
FG 35	FG	35	5+1	Panzer I Ausf. A; Krupp Protze Sd.Kfz. 247 Ausf. A, a lightly armoured Protze	Krupp M 305
FG 31	FG	31	5+1	Panzer I Ausf. B and variants e.g. kleiner Panzerbefehlswagen, Fahrschulpanzer I B (LaS Maybach); Panzerjäger I	NL38 TR
FG 34	FG	34	5+1	Panzer I Ausf. C (VK 6.01) REALLY?? J&D claim a Maybach VG 15 3 19. A "strengthened" VG 15 3 19 was good for 46 mkp in production models of the Panzer II.	HL45 P
ZG 35	ZG	35	5+2	L.K.A. 1 (Leichter Kampfwagen Ausland) and L.K.B. (Leichter Kampfwagen Bulgarien) (tanks for export only)	Krupp M-311
ZG 45	ZG	45	4+1 x2 (x2)	Sd.Kfz. 6 (Büssing-NAG) type BNL 5 (1935)	NL35 NL38 TU
G 45v	G	45v	4+1	Sd.Kfz. 6 type BNL 7	NL38 TUK HL54 TUKRM
SSG 45	SSG	45	6+1	Panzer II Ausf. a, b, c, A, B, C Marder II on Panzer II Ausf. F chassis (Sd.Kfz. 131) 15 cm sIG 33 auf Fahrgestell Panzerkampfwagen II (Sf) (12 made)	HL57 HL62 TR/TRM
SSG 46	SSG	46	6+1	Panzer II Ausf. F Also fitted in the only two 10.5 cm K gepanzerte Selbstfahrlafette	HL62 TR
SSG 48	SSG	48	6+1	Panzer II n.A. Ausf. L "Luchs", Sd.Kfz. 123; Panzer II Ausf. H and M (not produced)	HL66 P
G 55	G	55	4+1 x2	Sd.Kfz. 7 (Krauss-Maffei) KM m8, m9 & m10 Leichttraktor Krupp (c.1930), Nachschubfahrzeug (N)	HL52 TU (m8) HL57 TU (m9) HL62 TU (m10) Daimler-Benz M 36
ZG 55	ZG	55	4+1 x2	Sd.Kfz. 7 KM m11 M.A.N type FT truck, 1933–35	HL62 TUK (m11) MAN D 2085 K
ZG 60 (?)	?	?	4+1 x2	Sd.Kfz. 8 (Daimler-Benz)	HL85 TUKRM
G 65 VL230	G	65	4+1 x2	Sd.Kfz. 9 (FAMO)	HL108 TUKRM
6 EV 75	EV	75	6+1	Swedish Stridsvagn m/42 (made 1943–1944)	2x Scania-Vabis L/603/1
SFG 75	SFG	75	5+1	Panzer III Ausf. A, B, C Panzer IV Ausf. A	HL108 TR
SSG 76	SSG	76	6+1	Panzer III Ausf. D Panzer IV Ausf. B to J StuG IV Sturmpanzer (Sd.Kfz. 166)	HL108 TR HL120 TR
SSG 77	SSG	77	6+1	Panzer III Ausf. H to N StuG III 7.5 cm Kanone Ausf. B to G (Sd.Kfz. 142) Sturm-Infanteriegeschütz 33B; Sturmgeschütz IV	HL120 TRM
AK 7-200	AK 7-	200	7+1	Panther (Panzer V) Jagdpanther	HL210 HL230

Table 2 - Experimental or test ZF gearboxes

None of the gearboxes listed here, and very few of the vehicles they were tested in, actually reached series production during the war.

List of ZF WWII test/experimental gearboxes, never reached quantity series production

Type	Torque	Gears	Application	Engine
SSG	47	4+1	Panzer I Ausf. F (VK 18.01) and Ausf. J	HL45 P
SSG	51	?	Kätzchen	HL50 P
SSG	280	6+1	Neubaufahrzeug (early designs 1926–1928 for Panzer IV )	BMW Va
SMG	50	?	Panzer II Ausf. G All 5 SMG 50s installed in VK 9.01 (Panzer II Ausf. G 0-series) failed in a major test in April 1941. ZF conducted driving trials with a SMG 50 fitted in a VK 9.01 chassis from January 1942 to July 1943.	HL66 P
SMG	90	8+?	8.8 cm Flak auf Sonderfahrgestell Pz. Sfl. IVc, Grille 10 Tested in Flakpanzer based on Panther chassis with HL90 Tested in VK 30.01 (early Tiger), along with SSG 77 and Maybach SRG 32 8 128	HL90 P or HL100. HL 116 None reached series production.
SMG	91	?	Proposed for the MAN VK 20.02 Heuschrecke, as an alternative to the Maybach OG 32 6 16, although neither saw series production.	HL90 torque c.90 mkg
AK 5-	25	5+1	Proposed in late 1943 for Kleinpanzerjäger “Rutscher”	BMW CM3 Type 335
AK 5-	55	5+1	Proposed for Aufklärer 38(d), development of Panzerjäger 38(t)
AK 5-	80	5+1	Proposed for JagdPanzer D	Tatra 'Typ 103'
AK 5-	200	5+1	At least one tested with Panther II	Deutz T8 M118
AK 5-	250	5+?	Tested in post-war French AMX 50 project, because the French Army got to Friedrichshafen first.	HL295
AK 6-	200	6+1	Two built, for Panther II	HL234
AK 7-	80	7+1	Proposed for Krupp's Versuchsflakwagen-leichte	HL90
AK 7-	130	7+1	Proposed for a Flakpanzer based on Panther chassis	HL157
E	130	7+?	Electromagnetic gearbox, trialled with Panther II in June 1944	?
K 12 E	185	12+6	Gearbox with electromagnetic clutches. Proposed for Panther II, one fitted in standard Panther chassis. Paired with ZF LE-185 electromagnetic steering unit.	HL230

Background

General overview of gearbox construction

Main articles: Manual transmission and Semi-automatic gearbox

The general terminology of gearboxes may differ considerably by country. Gearboxes are often called transmissions, although the latter term is often colloquially used by mechanics and others to refer to the complete drivetrain by which power is transmitted from the engine to the driving whelks wheels. In modern terms, this may include the gearbox (which may be separate or of unit construction with the engine}, propeller shaft (or Cardan shaft, or simply 'prop shaft') and final differential gear. There are many implementations of this overall concept.

This article interchangeably uses both 'gearbox' and 'transmission' to refer only to a speed-shift mechanism. In this context, the gearbox or transmission is almost always a separate unit, either flanged directly to the engine (as in the half-tracks mentioned here) or powered by a prop shaft from the engine which is usually located at the rear of the vehicle.

The term 'transmission' may also include a separate 2-speed manual transfer gearbox, although no Wikipedia article appears to accurately define this specific simple mechanism. It is sometimes called a reduction gearbox (Untersetzergetriebe) although not necessarily of planetary construction, 'transfer case' 'hi-lo box', or 'crawler box', also often found in agricultural tractors. For the purposes of this article this type of reduction gearbox was fitted to most of the WW2 German half-tracks (except the Sd.Kfz. 10), providing a second set of low ratio speeds when very low speed and high torque was needed, such as hauling disabled vehicles out of a ditch, mud, etc. In the ZF transmissions under discussion here, the reduction box may be of separate construction and flanged to the rear of the change-speed gearbox, or of unit construction within the gearcase. This article does not discuss the differentials, steering gear or braking systems installed in tanks etc. made by other manufacturers.

Sliding-mesh 3-speed gearbox with reverse (blue)

Constant-mesh 4-speed manual transmission

• A) Manual transmission
  • 1) Sliding-mesh type (German: Schubgetriebe or Schubvorgelege). This is one of the oldest gear change mechanisms, dating back to at least 1906. The gears are physically moved up and down the (input) shaft (German: Welle) to engage with the corresponding gear on the (output) shaft. Almost always without synchro, and often called a 'crash box'. Skilful double de-clutching is needed to effect gear changes without 'crunching' the gears as they mesh at different speeds. Very often the gears are straight-cut, which produces a pronounced whine.
    None of the ZF transmissions listed here are of this type, although various gearboxes are briefly described by historians (eg Spielberger) as "Schub-", perhaps possibly to distinguish from synchro boxes.
  • 2) Constant-mesh (German: Klauengetriebe) type. As the name suggests, all the gears are constantly in mesh. Instead of shifting an entire gear wheel on a shaft, a selector fork moves a dog clutch (in purple in the diagram) on a shaft between a pair of gear wheels. All the ZF transmissions listed here are of this type, with or without synchro, and all with helical-cut (or helical-ground) gears.
    • ZF's trade name for this type of transmission was § 'Aphon' (Greek for "without noise" or "noiseless"), a helical-ground constant-mesh transmission introduced in 1928 for passenger vehicles. It eliminated the inherent whine of straight-cut gears.
  • 3) Synchromesh gearbox or 'synchro' (German: Synchrongetriebe) type. A development of the constant-mesh gearbox which eliminates the need for double de-clutching by the incorporation of 'synchro rings' between the dog clutches. The rings absorb the speed difference between the two shafts, essentially acting like basic automatic inline clutches. Almost all ZF gearboxes fitted to tanks etc. were of this constant-mesh synchro type.
    • eg Aphon SSG 45 synchro in the Panzer II, SFG 75 & eg SSG 76, Panzer III & IV etc.
    • 'AK' (Allklauen) series (German: Klauen, 'dog clutch'), were all synchro - eg AK 7-200 (7+1) for all Panthers. Also experimental AK 6-200 (6+1) & 5-200 (5+1) for later high-revving experimental Maybach HL154 etc. engines - neither the prototype engines nor gearboxes ever reached series production during WW2.
• B) Semi-automatic gearboxes.
  • Preselector gearbox type. Apart from the unsuccessful 6 EV 75 (see below), ZF doesn't appear to have made any series production of this type during the war, although it seems likely that they worked with Maybach on the designs of various models (eg SRG, Variorex and Olvars.) See List of WW2 Maybach gearboxes.
    • ZF Electro series - used internal electro-magnetic clutches, eg ZF 6 EV 75 (6+1) fitted to c.100 production Swedish Stridsvagn m/42 tanks in 1943–1944 (very unreliable - see table); and ZF K 12 E 185 proposed for late model Panthers but never reached series production.

Summary

• The 'G' and 'ZG' gearbox series installed in some half-tracks are all non-synchro.
  • All the ZF gearboxes fitted to a number of half-tracks had manual, non-synchro transmission with 4 forward + 1 reverse gears, coupled with a hi-lo range transfer box giving a total of 8 forward and 2 reverse speeds. This is expressed as (4+1 x 2). Some early models of the Sd.Kfz. 6 had a further hi-lo reduction box giving 12 forward and 3 reverse speeds. NB Spielberger in the English version of Halftracks has some very differing views, but I suspect he (and/or his translator) is completely in error. See talk. Some sources say that the Sd.Kfz. 9 may have had a synchro gearbox, but this is almost certainly incorrect.
  • Not all gearboxes fitted to half-tracks were made by ZF: eg the Maybach pre-selector Variorex in the Sd.Kfz. 10/250; and Hanomag installed their own gearbox in the Sd.Kfz. 11 and 251. (ref Spielberger, Halbketten in German, although the English edition makes some outlandish statements) J&D, Pz. Tracts, p. 22-2-7 state that a late trial version (not made in quantity), the H7, used a Maybach pre-selector box. Not further discussed. In some cases the range box is completely or semi-separate, as in the early 'G' series; and if of unit construction, the 'ZG' series (and, illogically, the G 60 in the Sd.Kfz. 9).

• The 'FG', 'SFG', 'SSG' and 'AK' series, installed in many other tanks and SP gun carriages etc., are all synchro (except 1 +R).
• Despite Spielberger's list in Halftracks of the German Army, ZF don't appear to have made any pre-selector gearboxes at all except the electromagnetic 'E' or 'EV' series, and they weren't a success (although due to manufacturing faults rather than design.)
  • See the interesting and fruitful discussion Talk:Sd.Kfz. 8, the reason for this article.

Torque

Gearboxes (colloquially, simply 'boxes') are generally designed to transmit a specific maximum torque.

The unit of torque used in Germany at the time was the Kilopondmetre, abbreviated as mkg in contemporary literature (sometimes mkp): modern abbreviations are kp·m or m·kp. 1 mkg = 9.80665 N·m = 7.233 lb·ft

• Torque (lb.ft) = 5,252 x power (hp) / speed (rpm)
• Torque (N.m) = 9.5488 x power (kW) / speed (rpm)
• Torque (mkg) = 716.19724 x power (PS) / speed (rpm) (thanks to GNU Units and the Science Ref desk)

Max. torque of an engine is often reached at lower revs (approx 2/3 max revs) than maximum power, eg 2,000 rpm vs 3,000. Refs needed... Diesel engines (inherently lower-revving through their basic design) produce max. torque at lower revs than a petrol engine, although diesels were not fitted to most German armoured vehicles.

ZF's naming scheme almost always indicates the rated torque of the gearbox - eg the SSG 45 was designed for Maybach HL62 TR's max torque output of 45 mkp/mkg. In some cases the gearbox was uprated to handle a greater torque, but kept the same model number.Ref pls! Similarly, the AK 7-200 was apparently designed for the HL210/230's max torque of c.200 mkg.

• I think I need a list of engines and/or gearboxes whose max. torque (Md. = Maximaldrehmoment) are definitely known. (Done: see Talk.) Spielberger's Panther tank and variants includes Appendix 18 with lots of original diagrams, graphs etc., including HL108 and HL230. NB! My thoughts below about tractability and flat torque curves may be completely wrong. They say (i fink) that a noticeable torque rise through the rev range with more gears, is equivalent(?) to a flat torque curve with fewer gears. Or something. Check, fool!

In tank and prime mover engines, the maximum power of an engine may be rather less important than its maximum torque.

Insert stuff about the relationship between the two. Not particularly easy to explain. Sports analogy: a bit like having a load of rugby players to haul you through the mud rather a bunch of sprinters to achieve maximum speed. See Büffel-Charakteristik, 'Buffalo characteristics' (Spielberger, Panther tank and variants, p. 236)

"A flat torque curve makes an engine much more driveable because acceleration is the same at any point on the curve. Transmission can be less complicated, not more. Engines with peaky torque curves require a lot of gears as acceleration is maximum only in a narrow rpm range.It is just difficult to get with max hp output." Put another way, a flat torque curve is desirable in a tank engine. More info needed.

"Torque can be increased by increasing the mean effective pressure of the engine, or by lowering the torque losses." power vs torque Includes lots of graphs for various fuel-injected spark car engines.

Clutch

See also: List of WWII Maybach engines § Clutch

Clutches, like gearboxes, are designed to transmit a specific torque from the engine to the drivetrain. The firm of Fichtel und Sachs (see also de:Fichtel und Sachs) supplied the majority of factory-fitted clutches either for ZF gearboxes or for Maybach engines/gearboxes where specified.

Most of the ZF gearboxes fitted to tanks (and SPGs, tank hunters etc.) discussed here were delivered to the various manufacturers' assembly plants with a clutch attached. These were connected by a prop shaft to Maybach engines without a 'K' in the model number (e.g. HL62 TR used in some Panzer IIs). There is at least one exception: a clutch was bolted to the HL120 TRM motor in the Panzer III Ausf. H and onwards, not to the SSG 77 gearbox. Maybach engines with a 'K' in the model number, almost all used in half-tracks (e.g. HL108 TUKRM in later Sd.Kfz. 9s) indicate that the clutch was fitted as standard by Maybach.

Planetary construction

Although a number of sources (mostly websites) claim that some ZF gearboxes used planetary gears, this never appears to be the case, although some differentials and final drives (not made by ZF) did. The term 'transmission' has been used in various ways, not all of them helpful.

END OF MAIN ARTICLE TEXT

Appendix A: Soden transmission

Lede

The Soden transmission (Soden-Getriebe) is a pre-selector, semi-automatic gearbox invented in 1921 by Alfred von Soden of ZF. It was fitted in passenger cars, light trucks, and also in the Leichttraktor, the forerunner of the Panzer III tank.

Although this gearbox was designed and made by ZF, its basic principles were generally developed and used in the SRG, Variorex (VG), and Olvar series of Maybach semi-automatic gearboxes used in WWII tanks and half-tracks.

Maybach and ZF (both subsidiaries of Zeppelin and all based in Friedrichshafen) had a close working commercial relationship, and between them had an effective monopoly of the design and manufacture of engines and gearboxes used in most German AFVs from c1935–1945. Sounds like bollox

History

It was shown to the public on 23 September 1921, at the first Berlin Motor Show since the war. This gearbox represented a feat of engineering that was far ahead of its time. A series of pre-series (Vorserienstand) gearboxes had already been launched in Vienna in October 1920, aimed at taxis, light trucks and buses.

The range included types S2.5, S3, S3.5, and S4 for passenger cars (Pkw, Personenkraftwagen) and type S5L for trucks (Lkw, Last\kraftwagen) A version for railway locomotives, Typ TS18.5, had 5 forward and 5 reverse gears.

The gears are straight cut and integrally form part of a shaft which incorporates a dog clutch mechanism at one end. The selector forks... ZF photo of a cutaway gearbox:

Leichttraktor

NB! OLD! Copy from History section!

The Leichttraktor of c1930 made by Krupp used a Soden transmission with 4 forward gears and 1 reverse. Changing gears was effected in two stages. First, the driver moves a small pre-selector lever into the desired slot. Secondly, the driver then presses down on the clutch pedal for a full second, during which time one of the pre-selected pistons in the top of the gearbox moves a selector fork to actually change gear. The driver then releases the clutch pedal, and the new gear is engaged.

When changing gear it was important to keep hold of the steering wheel while climbing a gradient, while turning, before going backwards or in a moment of danger. Description of gearbox on p. 15 [pdf 25]. The pre-selector lever is no. 5 in the photo, right on top of the gearbox. Close-up pic of lever on p. [40].

Apart from the Soden transmission used in the Leichttraktor, it doesn't seem that ZF actually made any quantity series production gearbox of this type for military use, except the ill-fated EV series with electromagnetic clutches, fitted to around 100 Swedish Stridsvagn m/42 tanks. In general, ZF made conventional, manual gearboxes, and Maybach made the more complex semi-automatic ones.

Outline of operation

NB! Needs plenty of refs! eg Leichttraktor, von Soden paper (HathiYech)/ZF pamphlet (** above)

Only a complete translation from the German Leichttrakor manual will clarify - possibly... Heavily parenthesised technical German... Argh

• NB! The ASCII diagrams below are very bad approximations of the pix and technical drawings by von Soden himself here: "Das neue Motorwagen-Getriebe der Zahnradfabrik G.m.b.H., Friedrichshafen a. B." [esp. pp 7-11], ZF pamphlet by Graf von Soden, reprinted from "Grundsätze über den Bau von Wechselgetrieben für Motorwagen und Beschreibung eines neuen Getriebes", by Dipl.-Ing. Graf von Soden, Der Motorwagen, XXIII. Jahrgang (1920), nos. XX and XXI. NB Fixed two-page layout. Sadly not downloadable or otherwise online.
• Other online volumes at archive.org of Der Motorwagen: IV. Jg, 1901 VI. Jg, 1903 VII. Jg, 1904 IX. Jg, 1906 X. Jg, 1907 XXV. Jg, 1922

NBB! There is no vacuum involved at all: it is a completely mechanical operation. The pins are held in place by spring pressure, either in a hole or against the circumference of the locking rotor/selector shaft: and retracted by a mechanical lever against the spring pressure. Simples.

Operation

Operation of Soden transmission (in German). Click for English translation

The constant-mesh gearbox has three shafts, one mainshaft and two layshafts below and to either side of it. See page 9 of the ZF pamphlet (von Soden, 1920)

First see ZF photos of gear selector lever (3-2-1-0-[N]-R) and cutaway gearbox, so you know what you're looking at: NB Werner Beisel wrote a book about it (Beisel, Werner. Das Sodengetriebe. 2018, ISBN 978-3-00-058503-6.)

Now see Leichttraktor manual 1930, Figure A6a [pdf 22]. In the photo on page A6 [pdf 24] of the manual, the pre-selector lever is no. 5, right on top of the gearbox. Close-up pic of lever on p. [40]. Description of gearbox on p. 15 [pdf 25]. First part of this description refers to p. A6 [22] (eg "Trennwand 2" (bulkhead). See also picture A13 [pdf 40] showing the gear lever. Page A6a [pdf 22] has a manufacturer's explanation BY ZF of how the gearshift mechanism of the Soden gearbox works.

1. (See Fig. 1.) The gear selector lever is directly connected (perhaps by a mechanical linkage) to a locking rotor shaft inside the gear change mechanism, located on top of the gearbox. The rotor shaft sits at right angles to the main gearshafts. The shaft has five lateral holes drilled along and around its length. Moving the gear lever pre-selects (but does not engage) the next position which the shaft will rotate into, so that just one hole will be horizontally aligned with the relevant pin.

     ↓-↓-↓-↓-↓--------- locating holes for pins under spring pressure
    _______  __
 __| O     └┘  |_ zz
|__    O        _|__|  ← gear selector rotor shaft (R)
   |_____O__┌┐_|  zz   ← teeth on gear wheel to rotate shaft, linked to gear shift lever

      Fig. 1. Side view of rotor shaft

     ● ● ● ● ●   ← locating pins with selector fork attached below
     | / | \ |   ← selector forks (Schaltgabel) (all five shown)
     | | ∩ | |   ← end of central selector fork, fitting over dog clutch on mainshaft
     \ | O | /   ← mainshaft (centre) + selector forks (four shown)
       ∩   ∩     ← rounded end of selector forks on layshafts (two not shown)
       o   o     ← layshafts (Nebenwellen)

Fig. 2. End view of selector pins and gearbox shafts. NB: The rounded of the selector forks sit directly over the dog clutches on the shafts (basic graphics)

2. (See above, Fig. 2.) In line with the rotor shaft and at 90 degrees to it, and thus parallel to the main gearshafts, there are five sliding pins (one per gear ratio, 4 forward and 1 reverse), which locate by spring pressure in a corresponding hole in the rotor. For any given gear, only one hole has a pin located in it; the rest press against the outside of the shaft. Put the other way round, each pin has one exactly hole it can locate into, and thus selects the desired combination of locked pinions. In the earliest versions, all the pins face the same way: in later version the pins on the outer two pistons face one way, and the inner three face the other way.

When the clutch pedal is depressed, a mechanical linkage retracts all the pins away from the shaft against spring pressure; the selector shaft rotates into the next pre-selected position, and when the clutch is released, spring pressure pushes the next relevant pin into its hole. There is a separate pin for reverse.

Small version of above diagram hidden here:§

3. (See Fig. 3.) Directly attached beneath each of the five locator pins is a selector fork, which moves a dog clutch a small distance on any of the gearshafts to engage and lock the desired gear ratio.

NB! Q1: How many pins need to be located to engage any given gear ratio? A1: One. Five pins (4+R), five holes, five combinations of dog clutches (e.g. In/Out/Out/Out/Out, or Out/Out/In/Out/Out).
Q2: How many pins need to be shifted in order to select a new gear? A2: Two: one out, one in. Simples.

          (R) =  Riegelwalze, locking rotor in 'Prinzipskizze' diagram above
|_____|== O shift pin (l.) and rotor shaft (r.) (end view). => Spring pressure to  engage.
   | | ← Selector fork attached to sliding dog clutch <= Disengaged by mechanical linkage
    \ \      ~~~~    ← gear teeth    
     \ \     |  |    ← gear pinion
______| |___=|__|___
      | |=  =|  |    ← shaft carrying pinions with dog teeth (=)
______|_|=__=|__|___     
      |_|   =|  |
             |  |
             ~~~~

  Fig. 3. Simplified section of shifter pin, selector fork and dog clutch

Translation next, I suppose. Also...

Soden patents

Various patents of von Soden: {{cite patent}}

• US1532564A - Coupling 1921 https://patents.google.com/patent/US1532564A/en
• US1502701A - Change-speed gear - 1922 - locking mechanism for [semi-auto?] gearboxes https://patents.google.com/patent/US1502701
• US2001292A - Clutch device for motor vehicles - 1933 - one-way clutch patent, like a sprag or cam clutch. https://patents.google.com/patent/US2001292

Refs

Sources

• Page on von Soden:[3]
• Pamphlet by von Soden (1920) about a new type of gearbox, and the Soden transmission:[4] MAKE A CITE!
• Pic of Soden S 3.5 gearbox (1920), showing rotor shaft and holes for shifting pins:[5]
• von Soden, Alfred (20 July 1920). "Grundsätze über den Bau von Wechselgetrieben für Motorwagen und Beschreibung eines neuen Getriebes" [Basic principles of construction of change-speed gearboxes, and description of a new gearbox]. Der Motorwagen (in German). XXIII. Jahrgang (Heften XX, XXI, XXIV): 355–360, 377–380, 454.
• Good close-up pic of the rotor shaft and locking pins of a pre-selector Soden gearbox.

Lots of info at https://www.sodengetriebe.de/.

- https://www.sodengetriebe.de/getriebe/ - good cutaway diagram of gear selector and g/box - https://www.sodengetriebe.de/fahrzeuge/ - list of Soden gearboxes for cars (PKW, Personenkraftwagen) and trains - https://www.sodengetriebe.de/getriebevarianten/ - more gearboxes, and pics of boxes named on the above page

Ext. links

• School of Tank Technology - Glossary of German Tank Terms - German/English Technical Glossary - 1943|

End of Appendix A

Appendix B: Info from Appendices to Spielberger's Panther tank and variants

Moved section from ZF gearboxen draft, 'More Panther tech data'

Spielberger, Panther tank and variants, p. 221, says the Maybach Olvar was physically shorter than the ZF AK 7-200.

In Appendix 2, p. 235 (NB not by Spielberger), Maybach & licensees made a total of 7000 Panther engines and 2000 Tiger ones (HL230 P45). The AK 7-200 weighed 750 kg., engine dimensions length 1310 mm x width 1000 mm x height 1190 mm. (p. 236)

Better: HL230 P45 power = 700 PS @3,000, torque = 185 mkg @2,100 rpm. (p. 235) Excellent. The clutch, a Fichtel & Sachs LAG 3/70 H could transmit 200 mkg at max rpm (ie 3,000). Even better.

The gearboxes were assembled at Waldwerke Passau; Steyr-Daimler-Puch in Graz-Thorndorf (Austria??) and Lanz in Mannheim also made components (and/or assembled them. (p. 236)

The magnetos (with impulse starter installed) were JGN 6/R 18 (p. 237) The 24 V electric starter used 2 x 12 V batteries in series.

Even more re Panthers: Appendix 8, Panther Btn. combat report (When?), said that some 30 tanks in constant combat for 6 days travelled an average of 700 km, with only 11 engine changes. Only 6 tanks were completely put out of commission by enemy fire. Destroyed 89 tanks/assault guns, and 150 guns, AT and AA guns.(pp. 244-5)

Last meeting of Panzer Commission, 31 Jan 1945:

Panzerjager 38D (German version): Torque could be improved from 48 mkg (with what engine?) to 78 mkg with the Tatra diesel engine, although it was almost impossible to fit into the design. "The gearbox" had double the torque of "the Wilson gearbox" with only 15% weight increase. (Spielb/ Panther, p. 258)

• NB A Wilson mechanism definitely relates to the clutch-steering gear and final drive, not the change-speed box. Obviously(?) all the components in the drivetrain need the same torque capacity.

The MM (Maybach Motoren) HL230 in the King Tiger only produced 540 PS at the governed 2,600 rpm. General Thomale (stub, needs expanding - see de:Wolfgang Thomale) expressly said that the new HL234 injection engine should NOT be rolled out until it has reached 100% maturity. (Ahem). (p. 258) Holzhaeuer wanted the 8-cylinder Tatra diesel for the 38(t), the 8-ton half-track (Sd.Kfz. 7) and the SWS, which would include the ZF AK 5-80 gearbox. Maybach proposed an HL64 with fuel injection instead of the Tatra, giving roughly 270 PS rather the 210 of the Tatra. (p. 259)

Finally: use of the AK 5-80 in the Panzer II (still???) and IV, and the AK 7-200 in the Tiger II needed to be planed for. Two Tiger IIs with AK 7-200s had been tested in Kummersdorf and there was no question about their reliability. [Even so, they still used the Olvar in the production vehicles.] (p. 260), 31 January 1945.

Flakpanzer based on Panther chassis: (Spielberger, Panther tank and variants p. 214)

"Krupp proposed the use of the following tank components:

— Track and running gear of the Panther (Leopard armored reconnaissance vehicle running gear was not adequate, since the larger road wheels brought about an increase in the muzzle height by approximately 100 mm)

— Maybach HL 157 engine with 550 hp (Aufklärungspanzer Leopard) - seems to be a correct figure...

— ZF AK 7-130 gearbox (Aufklärungspanzer Leopard) - another one for the ZF experimental table.Y

— Steering mechanism from either the Leopard armored reconnaissance vehicle or, considering the great length, possibly an in-house design." (Spielberger, Panther tank and variants p. 214)

And on p. 220, the test vehicles used an HL90, 360 hp @ 3,600 + ZF SMG 90, and proposed series would have used HL157, 550 hp @3,500 rpm. This is confirmed by Pz. Tracts 20-2, Paper Panzers Vol 2 p. 20-66 and 20-94) - 'Leopard': 550 PS @3,500 or 3,600 rpm - perhaps fuel-injected.

• Appendix 15, p. 254, 'Organisation of a Panther tank maintenance unit'.
  • A report quoted in The Combat History of German Heavy Anti-tank Unit 653 (Münch, 2005, pp. 275-6), stresses that piecemeal use of tanks/tank hunters should be avoided, since the maintenance unit cannot be in two places at the same time. Various Ferdinands from the battalion were deployed in two distant locations; broken-down vehicles which could have been fixed were completely abandoned for lack of repair facilities.
  • Also, really good details of specific tech problems with engines/transmissions on Münch, p. 277. Also see Repairing the Panzers, vol. 1 (Friedli). There were basically - i fink - four levels of maintenance: man with a spanner (battery level); men with a workshop and/or mobile 3 or 10-ton? crane on a 4-wheel truck or Sd.Kfz. 9/1 (company level); men with a bloody big crane capable of lifting a turret off (battalion level); return to factory (army level). Although physical tanks themselves are the most obvious components of an armoured unit, the behind-the-scenes support sections to keep them running are considerably more numerous.
• Appendix 17, 'Final meeting of the Panzerkommission' section 5, p. 258, Panzerjäger 38 D
• Appendix 18, p. 262, 'Gasoline or diesel engines for the tank'.
  • Kniepkamp (either in Estes?) or BIOS report? explains how the official requirements for tanks stated a specific combat radius. Petrol engines met these specs. It's a trade-off. If the reqs. had been for a greater distance, diesels would have been used, since the increased overall weight of engine, fuel etc. is compensated for. Plus, in c. 1936/7 the fuel industry had indicated that gasoline was going to be cheaper to produce than 'artificial' diesel. This had changed by 1943, but it was too late by then. Ferdinand Porsche (who had Hitler's ear) was very much into diesel, and various other manufacturers; the Tatra air-cooled diesel was slated for the Jagdpanzer 38D by late 1944, but it was far too late by then. Also, German armaments production during World War II shows how vast amounts of money and labour were expended on useless projects (Graf Zeppelin aircraft carrier, Atlantic Wall, monster tanks, V-2 rockets etc.) when sheer numbers of much cheaper weapons might have made an actual difference.
• Appendix 19, p. 268, 'Newer tank models'.

Panther breakdowns by Niklas Zetterling:

https://dupuyinstitute.org/2018/08/10/panther-breakdowns-in-january-1944/

https://dupuyinstitute.org/2018/11/09/panther-breakdowns-in-february-march-1944/

End of Appendix B

References

Notes

Citations

Sources

• Anonymous (c. 1930). "Leichttraktor manual" (PDF) (in German). Retrieved 25 July 2021.

• Chamberlain, Peter; Doyle, Hilary (1993). Encyclopedia of German Tanks of World War Two: A Complete Illustrated Directory of German Battle Tanks, Armoured Cars, Self-Propelled Guns and Semi-Tracked Vehicles, 1933–1945 (revised ed.). London: Arms and Armour. ISBN 1854092146.

• Doyle, Hilary Louis; Friedli, Lukas (2016). Vollketten M.S.P. Kätzchen and Final Developments of the Schützenpanzerwagen (Sd.Kfz.251). Panzer Tracts 15-4. Boyds, MD: Panzer Tracts.

• Fleischer, Wolfgang (1997). Fahrschulpanzer der Wehrmacht 1935-1945. Wölfersheim-Berstadt: Podzun-Pallas Verlag. ISBN 3790905992.

• Friedli, Lukas (2010). Repairing the Panzers: German Tank Maintenance in World War 2, Vol. 1. Heathfield, Sussex; Monroe, NY: Panzerwrecks (No ISBN).

• Jaugitz, Markus (1998). Panzerbergung im 2. Weltkrieg. Waffen-Arsenal Special S-22 (in German). Wölfersheim-Berstadt, Germany: Podzun-Pallas-Verlag. ISBN 3-7909-0638-7.

• 4–0 Jentz, Thomas L.; Doyle, H. L. (1997a). Panzerkampfwagen IV - Grosstraktor to Panzerbefehlswagen IV. Panzer Tracts 4. Boyds, MD: Panzer Tracts. ISBN 9780964879348.

• TT–2 Jentz, Thomas L.; Doyle, H. L. (1997b). Germany's Tiger Tanks: VK 45.02 to Tiger II - Design, Production and Modifications. Atglen, PA: Schiffer Publishing. ISBN 9780764302244.

• 8–0 Jentz, Thomas L.; Doyle, H. L. (2000a). Sturmgeschuetz - s.Pak to Sturmmoerser. Panzer Tracts 8. Darlington, MD: Darlington Productions. ISBN 9781892848048.

• TT–1 Jentz, Thomas L.; Doyle, H. L. (2000b). Germany's Tiger Tanks: D.W. to Tiger I - Design, Production & Modifications. Atglen, PA: Schiffer Publishing. ISBN 9780764310386.

• 20-1 Jentz, Tom; Doyle, Hilary (2001). Paper Panzers: Panzerkampfwagen, Sturmgeschuetz, and Jagdpanzer. Panzer Tracts 20-1. Boyds, MD: Panzer Tracts. ISBN 0-9708407-3-X.

• 1-1 Jentz, Thomas L.; Doyle, H. L. (2002a). Panzerkampfwagen I Kleintraktor to Ausf B. Panzer Tracts 1-1. Boyds, MD: Panzer Tracts. ISBN 9780970840769.

• 1-2 Jentz, Thomas L.; Doyle, H. L. (2002b). Panzerkampfwagen I Kl.Pz.Bef.Wg. to VK.18.01. Panzer Tracts 1-2. Boyds, MD: Panzer Tracts. ISBN 9780970840783.

• 5–1 Jentz, Thomas L.; Doyle, H. L. (2003). Panzerkampfwagen Panther Ausführung D with Versuchs-Serie Panther, Fgst.Nr.V2. Panzer Tracts 5–1. Boyds, MD: Panzer Tracts. ISBN 0-9708407-8-0.

• 15-2 Jentz, Thomas L.; Doyle, H. L. (2005). mittlerer Schuetzenpanzerwagen (Sd.Kfz.251) - History of Variants, Production, Organization, Issue, Tactics and Employment in Action from 1939 to 1942. Panzer Tracts 15-2. Boyds, MD: Panzer Tracts. ISBN 0977164314.

• 3–1 Jentz, Thomas L.; Doyle, H. L. (2006a). Panzerkampfwagen III Ausf. A, B, C & D. Panzer Tracts 3–1. Boyds, MD: Panzer Tracts. ISBN 9780977164349.

• 15-3 Jentz, Thomas L.; Doyle, H. L. (2006b). mittlerer Schuetzenpanzerwagen (Sd.Kfz.251) Ausf.C & D - History of Production, Variants, Organization and Employment in Action from 1943 to 1945. Panzer Tracts 15-3. Boyds, MD: Panzer Tracts. ISBN 9780981538242.

• 3-2 Jentz, Thomas L.; Doyle, H. L. (2007a). Panzerkampfwagen III Ausf. E, F, G & H. Panzer Tracts 3-2. Boyds, MD: Panzer Tracts. ISBN 9780977164394.

• 2-2 Jentz, Thomas L.; Doyle, H. L. (2007b). Panzerkampfwagen II Ausführung G, H, J, L, and M development and production from 1938 to 1943. Panzer Tracts No. 2-2. Boyds, MD: Panzer Tracts. ISBN 0977164381.

• 2-1 Jentz, Thomas L.; Doyle, H. L. (2008a). Panzerkampfwagen II Ausführung a/1, a/2, a/3, b, c, A, B, and C development and production from 1934 to 1940. Panzer Tracts No. 2-1. Boyds, MD: Panzer Tracts. ISBN 9780981538228.

• 15-1 Jentz, Thomas L.; Doyle, H. L. (2008b). leichter Schuetzenpanzerwagen (Sd.Kfz.250) Ausf.A & B - History of Production, Variants, Organization and Employment in Action from 1941 to 1945. Panzer Tracts 15-1. Boyds, MD: Panzer Tracts. ISBN 0981538207.

• 3-3 Jentz, Thomas L.; Doyle, H. L. (2009). Panzerkampfwagen III Ausf J, L M & N. Panzer Tracts 3-3. Boyds, MD: Panzer Tracts. ISBN 9780981538242.

• 2-3 Jentz, Thomas L.; Doyle, H. L. (2010c). Panzerkampfwagen II Ausführung D, E, and F development and production from 1937 to 1942. Panzer Tracts No. 2-3. Boyds, MD: Panzer Tracts. ASIN B0045W90UK.

• 23 Jentz, Thomas L.; Doyle, H. L. (2011). Panzer Production from 1933 to 1945. Panzer Tracts No. 23. Boyds, MD: Panzer Tracts. ASIN B004WXA45C.
  • NB This volume gives Jentz and Doyle's final production estimates for most of the German fighting vehicles covered in their earlier Panzer Tracts series and other publications. The authors state they had not completely understood the complexity of the original documentation. It is essential to use this book in conjunction with any other Panzer Tracts volume to ascertain the correct production figures.

• Köster, Roman (10 August 2008). "Zeppelin: The airship and the need for diversification after WW I (1918–1929)" (PDF). European Business History Association (EBHA). Retrieved 25 July 2021.

• Naunheimer, Harald; Bertsche, Bernd; Ryborz, Joachim; Novak, Wolfgang (2010). Automotive Transmissions: Fundamentals, Selection, Design and Application. Translated by Aaron Kuchle (2nd, illus. ed.). Springer Science & Business Media. ISBN 9783642162145.

• Sawicki, Robert; Ledwoch, Janus (2007). Mittlere ZgKw 5t: Sd Kfz 6 (in Czech and English). Warsaw: Wydavnictwo "Militaria". ISBN 9788372192875.

• von Soden, Alfred; Dornier, Claude (1911). "Mitteilungen des Luftschiffbau Zeppelin in Friedrichshafen: Die Bestimmung des Schiffwiderstandes durch Farhtversuch" [Determination of airship resistance through flight tests]. Zeitschrift fur Flugtechnik und Motorluftschiffahrt (in German). 2. (US access only)</ref>

• Spielberger, Walter J. (1974). Die Panzerkampfwagen I und II und ihre Abarten (in German). Illustrated by Hilary L. Doyle and Uwe Feist. Motorbuch Verlag Stuttgart. ISBN 3879433356.
• Spielberger, Walter (1978). Die Rad- und Vollketten Zugmaschinen des deutschen Heeres 1871-1945 (in German). Illustrated by Hilary L. Doyle. Motorbuch Verlag Stuttgart. ISBN 3879435286.
• Spielberger, Walter J. (1993a). Die Halbkettenfahrzeuge des Deutschen Heeres 1909-1945 (in German). Illustrated by Hilary L. Doyle and Uwe Feist (4th ed.). Motorbuch Verlag Stuttgart. ISBN 3879434034.
• Spielberger, Walter J. (1993b) [1977]. Panzer IV & its variants. Illustrated by Hilary L. Doyle and Uwe Feist. Translated by Edward Force. Atglen, PA: Schiffer Military/Aviation History. ISBN 0887405150.
• Spielberger, Walter (1993c). Panther & its Variants. Illustrated by Hilary L. Doyle and Uwe Feist. Atglen, PA: Schiffer Military/Aviation History. ISBN 0887403972.
• Spielberger, Walter J. (1994). Sturmgeschutze: Entwicklung und Fertigung der sPak (in German). Illustrated by Hilary L. Doyle and Uwe Feist (2nd ed.). Motorbuch Verlag Stuttgart. ISBN 3613013568.
• Spielberger, Walter (1998). Der Panzerkampfwagen Tiger und seine Abarten (in German). Illustrated by Hilary L. Doyle (6th ed.). Motorbuch Verlag Stuttgart. ISBN 3879434565.
• Spielberger, Walter J. (2007). Panzer III and its Variants. Atglen, PA: Schiffer Publishing. ISBN 978-0887404481.
• Steude, Heinz (June 1965). "Graf von Soden-Fraunhofen". Tradition: Zeitschrift für Firmengeschichte und Unternehmerbiographie (in German). 10. Jahrg. (3). Verlag C.H.Beck: 97–111. JSTOR 40696961.

External links

• Panther Tank's Steering and Gearbox conical Synchromesh on Youtube
• Panther Tank Transmission details on Youtube
• Zahnradfabrik 12 E 170 by Kedoki (in Russian)
• Report on Interrogation of Dipl.-Ing. Ernest Kniepkamp (tank engines) Transcription of BIOS report