User talk:MinorProphet/Draft subpages/WW2 Maybach gearboxes

Things to investigate
Lots of this was copied from the main article when I finally worked out how it sort-of worked. A lot of it depends on the stated maximum torque of the engines they were *originally* fitted to, some of which I have determined thanks to List of WWII Maybach engines. MinorProphet (talk) 22:35, 20 July 2022 (UTC)

Model numbering, Part 1
I have no idea how the numbering of the SRG/VG/OG types works. I now know exactly how the numbering of the SRG/VG/OG types works: but not exactly why. NB! Almost all my queries in the following three sections have now been answered... MinorProphet (talk) 01:38, 30 March 2022 (UTC)

...Some have 5 figures, often in a 2-3 sequence; some model numbers have 6 figures, either in pairs, triplets or a 2-1-3 configuration. Unlike the ZF gearbox naming scheme, which generously includes its max. torque in the model number (e.g. ZG 45), there seems to be no hint at all about any pre-selector gearbox's capability. They could be simply design or project numbers with no regard to logic/reality whatsoever.
 * [later edit]: I was almost right. The numbers relate to the specific engine for which they were originally designed. The model number remained unchanged when fitted to later, considerably more powerful engines: which tends to indicate that the gearbox had undergone some development during its pre-production phase. MinorProphet (talk) 11:03, 17 July 2022 (UTC)

Also the Maybach engine numbering scheme is very obvious, including the capacity eg HL42. Why all the nonsense?
 * Well, Spielberger & Doyle, Panzerkampfwagen Tiger und seine Abarten, 6th edition, 1998 (in German), p. 18, has this to say:
 * "Versuchsweise kam bereits ein Maybach OLVAR Getriebe vom Typ 40 12 16 zum Einbau. Dieses wurde ursprünglich für einen Motor mit 400 PS Leistung entwickelt (40 = 400 PS/12 = Md 120 mkp/16 = i = 16). Es hatte acht Vorwärtsgänge und einen Rückwärtsgang. Für das 7. und 8. Fahrzeug war ein neues Lenkgetriebe vom Typ SMG 90 vorgesehen." My translation:
 * "A previously existing Maybach OLVAR transmission of type 40 12 16 was installed by way of experiment. This was initially developed for a motor/engine of 400 PS output. (40 = 400 PS; 12 = Md 120 mkp; 16 = i = 16). For the 7th and 8th vehicle[s] a new steering gear of type SMG 90 was envisaged." Well, this appears to make very little sense.

1. No-one describes a gearbox in terms of power, which is a function of torque. And anyway, the rated power of an engine is almost always its max. power, NOT the power where max. torque is developed, which is around 2/3 of max power, at around 2/3 of max revs. Just sounds like nonsense...
 * By May 1941, when the VK 45.01 spec was finalised, Maybach's most powerful functioning engine was the HL120 which made no more than 300 PS.
 * As far as I know, Maybach designed two research/experimental engines of around 400 PS: the HL157 P (410 PS) slated for the VK 16.02 Leopard from around 1941; and the HL100 (400 PS), possibly fuel-injected, proposed for the Heuschrecke 10 and Hetzer, but that was by c.1943. Jentz & Doyle (2000) Germany's Tiger Tanks: D.W. to Tiger I, p. 10, mention an HL150 of 400 PS @3,400 (see Talk:List of WWII Maybach engines.)
 * Even further, the concept of a 30-ton tank had been raised as far back as 1936 (see Talk:List of WWII Maybach engines, and Dr. Maybach himself said a 600 PS engine was needed, but at the time it would have to have been a gigantic V-16, half a metre longer than the HL108. So why, therefore, would the Olvar 40 12 16 have been even developed for a 400 PS engine? Well, that's perhaps all they had at the time. So because its original spec was for something much less powerful, the Olvar's model number didn't reflect the power etc. of the actual engine it was finally used with.

2. What does 'Md' stand for? Drehmoment = 'torque', perhaps Md. = Maximaldrehmoment, Max. torque. Sounds good.
 * But, might an engine develop 120 mkp of torque when it's making 400 PS? ? See User:MinorProphet/Draft subpages/WW2 ZF gearboxes. It's an almost nonsensical idea to express the rating of a gearbox in these terms.
 * Well... the HL108 (c.250 PS) produced 75 mkg @2000 rpm. If the HL120 made even 300 PS @2,800, (Spielberger says 280 PS on p. 12 - and 300 PS @3000 rpm for the HL116 on p. 14) that might be eg 200 PS @1800, that's 716.2 x power / speed = 716.2 x 200 /1800 = approx. 80 mkp. BUT: The HL230 (up to 700 PS @3,000, and perhaps 600 PS @2,100) developed around 200 mkp, and the Panther used the ZF AK 7-200 gearbox for this reason. The Tiger used the Olvar, which must have had the same sort of torque rating, namely 200 mkp. It almost defies probability that the Olvar was originally designed to transmit 120 mkp for a 400 PS engine, when it ended up connected to a 700 PS engine developing 200 mkp.
 * Assuming that these figures are meaningful, 400 PS @ 3,000 might make 300 PS @1,800 : 716.2 x 300 / 1800 = 120 mkp. Or even taking the figures literally, 716.2 * 400 PS / 3000 rpm = 94 mkp. But no-one would ever describe a gearbox in that way, especially since the revs aren't specified.

3. And what does 'i' in "16 = i = 16" mean? In German abbreviations, 'i' almost always means in or im - but this seems not to be the case here. It might be some sort of standard letter used in eg physics formulas - lower case abbrevs. would be adjectives, or at least not nouns.
 * Well, Dubbel + eds. (1994), Handbook of Mechanical Engineering, section 8.1.2, p. F 117, says that i=transmission reduction ratio. Spielberger, Panther tank & variants, Appendix 2, p. 236, says the AK-200 had an entire reduction ratio of 1:13.4, so if i does = reduction ratio, then i = 16 for the Olvar in the Tiger may be good... But the Tiger book isn't so forthcoming, although it contains a complete reprint of the Tiger-Fibel at the end. Dubbel also says on the same page that the total reduction ratio is the sum of the individual ratios of each gear: i = i1 + i2, etc. So more boxes with gears will likely have a higher number. But where is an explicit working-out of this idea? Spielberger's Stugs (sPak) p. 37 has a nonsensical list to arrive at 1:14.5; Spielberger Panther and variants p. 236 says 1:13.4, but adding up the listed ratios (even if you subtract reverse - (wot??) ends up with 1:11.87.

4. The term 'Lenkgetriebe' (in the quote from Spielberger above) definitely refers to 'steering gear'. So why do people say that an SMG 90 was a gearbox, as well an SMG 50 installed in four Panzer II Ausf. G to compare with four Maybach OG 20 417 (and an SMG 91 proposed for the Heuschrecke? See User:MinorProphet/Draft_subpages/WW2_ZF_gearboxes. Are these real?


 * "On 4 November 1942 Krupp presented its drawings for a Flakpanzer (Gerät 42), making use of the following Panther components: running gear, track tensioning device, drive sprocket, final drive, steering mechanism, hand and foot levers, ZF AK 7-200 gearbox and Maybach HL 230 engine. Krupp relayed that the ZF SMG 90 gearbox and L 320 C steering mechanism, which were planned for use in the prototype model, had already been tested in another Krupp vehicle and that the gearbox exhibited serious problems, causing only limited driving performance to be reached. Krupp therefore proposed an alternate installation using the proven ZF SSG 76 gearbox (Panzer III and IV) together with its own design of a single-radius steering mechanism." (Spielberger, Panther tank and variants p. 214)

Short biographical sketch of Kniepkamp on p. 230.

5. This numbering scheme only makes sense for a couple of OGs and VGs. The OG 55 11 77 (see Table 2 below) fitted in the Leopard used the HL157 P, which did actually produce 550 PS @3500.(Spielberger, Tiger und seine Abarten, p. 209) But did it make 110 mkp? Most of the others have 5 figures in the name. The HL230 developed 185 mkp.

Model numbering, Part 2
Well, well. Spielberger (1994), Sturmgeschütze: Entwicklung und Fertigung der sPak p. 37 states that the 10+1 SRG 328 145 had a total gearbox reduction of 1:14.5 (i=14.5) Well, having read this again more carefully...! Spielberger re-states the numbering scheme. Here's a translation.


 * "On 21 June 1938 Maybach licensed or outsourced the production of the SRG 328 145 to the Altmärkische Kettenwerke GmbH (Alkett). In 1939 the previously-named "Schaltreglergetiebe" (SRG) received the name (Wortzeichen) VARIOREX. All assembly firms had to name the licensed gearboxes/transmissions as "Variorex-Getriebe, Lizenz Maybach". Instead of the previous designation SRG, every transmission type had to be furnished with the designation VG, and furthermore a three-part numerical description:


 * 1) The hundreds and tens figure/part (die Hunderte- und Zehnerzahl) of the power (PS)
 * 2) The hundreds and tens figure/part of the torque (mkg)
 * 3) The total reduction ratio (Gesamtsprung) of the transmission." (Spielberger 1994, p. 37)

The reason for this re-designation appears to be that the SRG 32 8 145 used in Panzer III Ausf. E, F, & G was a wholesale disaster, and Maybach wished to swiftly bury all memory of it. The replacement ZF SSG 77 was installed from mid-1939 in Panzer III Ausf. H onwards, because of the unconscionable delays to get the SRG to work. It took nearly 5 years from its proposed installation in Panzer IIIs in May? 1937? When, fool? until the problems were sorted out in c1942. Refs above and/or below.

NB! Ahaha! Numbering scheme of the SRG 32 8 145: The HL120 in the Panzer III from Ausf. H did indeed stick out 300 PS, approx. 80 mkp, and 145 = i = 14.5 is the gearbox's reduction ratio (see Spielberger 1994, Stugs, p. 37) ...! So it all makes sense in the end.

So my rant above about stating the rated power of the gearboxes was plain wrong. Most of the first numbering section can be deleted, especially my uninformed comments.

On Spielberger 1994, p. 36, two sets of original drawings show very clearly the arrangement in the Stug III Ausf. A and B. In the Ausf. A - not many made - the clutch is attached to the gearbox (the SRG 328 145, like the Panzer III Ausf. E-G); and in the Ausf. B the SSG 77 (like all the Panzer III Ausf. H to N) with the HL120 TRM, with clutch as stated in Panzer Tracts 03-2, pp. 3-2-70 & -71.

On p. 40 he specifically states that the 6-speed SSG 77 gearbox in the Stug III Ausf. B was capable of transmitting up to 77 mkg. NB! This can go in the Torque section of ZF Gearboxes draft. This also indicates that the SRG 32 8 145 had a maximum torque of around 77 mkg - in fact the '8' denotes around 80 mkg.

Model numbering, Part 3
Soooo... Spielberger, Panther & variants, Appendix 2, p. 236 gives all the gear ratios of the AK 7-200, and the "entire reduction ratio" of 1:13.4. I may have misunderstood Dubbel - yes - he puts the functions in brackets next to each other, which does mean multiply in maths. And all the web pages say that you multiply the ratios together: but I think they are are somehow wrong.

AK 7-200 Gear Ratio Jump 1   9.21  2.02  2    4.56  1.59 3    2.87  1.56 4    1.83  1.45 5    1.27  1.41 6    0.90  1.31 7    0.69

Multiplying the ratios gives about 117, and adding them gets around 20, so these must both be wrong. So I multiplied all the jumps: the product of which is approx. 13.419 ! Which means you have to divide the ratio of any gear by the next lower ratio: eg 0.90 / 0.69 = 1.304 (not exactly 1.31...) and 4.56 / 2.87 = 1.59.

On a calculator: start with the 1st gear, divide it by 2nd gear. Press M+. Divide 2nd by 3rd. Multiply by MR. Clear memory (MC). Add shown number to now empty memory (M+) again. Divide 3rd by 4th, multiply by MR, MC. M+. etc. This works. So you don't have to write down the jumps, but it would help if you go wrong.

Now I need another set of gear ratios, and its total reduction ratio.

Another post from Kedoki (in Russian), June 24th, 2017, (The three SRG posts above begin on September 15th, 2016) shows that you only have to divide the highest gear ratio by the lowest to get the same figure: or even the max. speed in top by the max speed in bottom gear, since they are directly related by the reduction ratio of the differential steering gear. It's true.

He also shows how the OG 55 11 17 on the VK 16.02 relates to the HL157 (550 hp at 3600 rpm) for which was originally designed, and that the OG 40 12 16 was developed on the VK 36.01 (h) with an HL175 of 450 PS.

Just like I did, he gets his calculator out and reverse engineers the gear ratio table for the OG 55 11 17 by reference to the Tiger and Panther. 8 + 2 gears, 1st is 1:11.22, 8th is 1:0.66, and the TRR is 17 (i = 11.22 / 0.66)

SRG 328 145 (Spielberger, Stugs [sPak] p. 37) Gear Ratio Jump 1   8      1.36 2    5.88   1.34 3    4.39   1.33 4    3.3    1.36 5    2.43   1.34 6    1.81   1.36 7    1.33   1.33 8    1.00   1.34 9    0.75   1.36 10   0.55  = 14.56 or 8 / 0.55 = 1:14.55

The G45v (note 15 see next section) has these ratios:

Gear Ratio Jump 1st 5.58  1.84 2nd 3.04  1.77 3rd 1.72  1.72 4th 1.00

Total reduction ratio = 1:5.58, or roughly 5.6. But why is this the same as 1st? Dunno. Ah, Because 4th is 1:1, and 5.58 / 1 = 1:5.58. QED.

The jump (q value) or steps between gears are approximately from 1.34 - 1.75. For a smooth acceleration curve all the steps need to be approximately equal expect perhaps 1st.

Table of gearboxes, ordered by total reduction ratio (TRR) VK 16.02  OG 55 11 17   8 gears, 11.2 / 0.66 - TRR = 1:17 - yes Tiger,    OG 40 12 16   8 gears, 11.0 / 0.68 - TRR = 1:16    - ok Panzer III SRG 328 145  10 gears, 8.00 / 0.55 - TRR = 1:14.55 - ok Panther    AK 7-200      7 gears, 9.21 / 0.69 - TRR = 1:13.4 Sd.Kfz. 10 VG 102 128   7 gears, 70.0 / 5.50 - TRR = 1:12.7 (km/h)  - ok  Panzer III SSG 77        6 gears  40.0 /  5.5 - TRR = 1:7.27 (km/h) Panzer IV SSG 76        6 gears, 42.0 /  5.8 - TRR = 1:7.24 (km/h) Panzer IV SFG 75        5 gears, 32.4 /  5.1 - TRR = 1:6.35 (km/h) Sd.Kfz. 6 G45v          4 gears, 5.58 / 1.00 - TRR = 1:5.58

I'm not sure that I need to do any more tables since the total reduction ratio 'only' shows the difference between bottom and top gears and the tractability, if you like, of the gearbox.

Note for Auflkaerer 38D - PzTr 20-2, p. 20-74

Model numbering, Part 4...
Main sources: Spielberger [& Doyle] (1998), Panzerkampfwagen Tiger und seine Abarten, 6th edition (in German), p. 18; and Spielberger (1994), Sturmgeschütze: Entwicklung und Fertigung der sPak, p. 37.

1st numbers = 100s and 10s components of engine power in PS. eg 14 = 140 PS as in SRG 14 4 79 2nd number(s) = 100s and 10s of torque in mkg. eg 8 = 80 mkg, as in SRG 32 8 145 3rd numbers = total gearbox reduction ratio, leaving out any decimal point (decimal comma in German) (i = 128 = 12.8), as in VG 10 2 128.

However, these numbers relate to the engine for which the gearbox was originally designed. Spielberger Tiger & Abarten p. 18 says that the Olvar OG 40 12 16 was initially developed for an engine of 400 PS output, approx. 120 mkp, and a reduction ratio of 1:16. This transmission was eventually fitted in the all the Tigers, along with the HL230 which developed 700 PS @3,000 rpm and 185 mkg @2,100 rpm.(Spielberger, Panther and variants, p. 235) An accurate reflection of this engine's capabilities would result in a theoretical OG 70 18 16 [assuming the total reduction ratio remains the same]. MinorProphet (talk) 11:10, 17 July 2022 (UTC)

Similarly, late experimental models of the Panzer II n.A (neue Art) Ausf. H & M (VK 9.03), had a "strengthened" VG 15 319 (Table 2 below). This was fitted with an HL66 P developing 180 PS @3,200, and 46 mkp @2,000 (J&D, PzTr 2-2, p. 2-2-12). Its theoretical numbering would be a VG 18 4 319 (assuming the reduction ratio wasn't changed - hah!)

The numbering of some later transmissions might more closely reflect the capabilities of the relevant engine: eg the OG 55 11 77, used in the VK 16.02 'Leopard', with a (fuel-injected?) HL157 P which developed 550 PS @3,500 (torque unknown, could be 110 mkg, since the HL230 made 185 mkg). A reduction ratio of 1:7.7 seems a little low, but with the trend for gearboxes with fewer gears, it could be possible.

To test the theory (NB falls down immediately):

VG 102 128H (7+3). Fitted in Sd.Kfz. 10 and 250, which used an HL42 TUKRM. This developed c.100 PS @2,800, thus 100 = 10. Torque unknown atm, but the NL38 TUK developed 25 mkg @1,700 rpm, taken from the Sd.Kfz 6 BNL 8 parts list. So a similar torque figure in the 20s might apply to the HL42, thus up to 29 mkg (rounding down) gives 29=2. Theoretically i=128, but no confirmation... Argh.

Tiger
Olvar OG 40 12 16 A (again): Spielberger Tiger & Abarten, p. 201, gives 1:10.75 (Vorgelegeübersetzung, transmission gear ratio) but this is probably the final drive reduction, not the gearbox. On p. 204 (Tiger II B), 1:12.56 for the OG 40 12 16 B, but again probably the final drive reduction.

Photos of other test engines for the Tiger on p. 183, Simmering-Graz-Pauker Sia 16, plus Simmering's brake testing machine, good for 15,000 PS...

On p. 187, graph of revs/speed in each gear for a Tiger fitted with an AK 7-200. Although the speeds are given at max revs, 3,000 rpm, theoretically giving 50 km/h in top (7th), the HL230 was limited to 2,600 (or 2,500? check!), and the graph shows that at 2,600 rpm it wouldn't do much more than 40 km/h.

J&D, Germany's Tiger Tanks 1, p. 76 [40], says HL230 P45s were governed at the factory to 2,500 rpm. Around 250 P45s were rebuilt with better bearings in Oct-Nov 1943 with 'M' on the serial plate, and improved bearings fitted from January 1944. Lower compression ratio pistons and copper rings pressed into grooves to solve the leaking head gasket problem from August 1943.

On p. 96, cutaway photo and schematic of geartrain of the ZF 12 E 170 (Versuchs) - I was right about the 'V' - electro, with bloody great big shift clutches tested in two Tiger chassis in September 1942.

PDF reader: Go to pdf page = Ctrl + Shift + N

Compare photo on p. 118 [107] of 'an' Olvar (type B?) in a Tiger B, with small clutch bulge at the top, squared-off main clutch at the bottom, plus 2 round bolted cover plates, then prop shaft flange. Plus big diagonal link from gear selector lever area.

On pp. 50-51, [45] lots of pix & schematic of 'an' Olvar. At the rear, a big box-like construction, almost the height of the whole 'box, with the flange for the prop shaft protruding at the back. Big clutch bulge at the bottom. Possibly just a cover. Three shafts, mainshaft on top, another directly below, and a third to one side between them O O     O

And on page 47, the total reduction ratio (Gesamtuntersetzung) is given as 1:16. Which is what you might expect. And same figure 1:16 on p. 195 for the Tiger B, Gesamtsprung. And what is simple "Untersetzung des Getriebes" at 1:11? Gives all the speeds in all the gears, but not the ratios.

On p. 43, good pic of the HL210 and its one-piece casting, with huge hole for the web crankshaft.

J&D, Germany's Tiger Tanks 1, DW to Tiger I (2000) p. 35 gives all the gear ratios in the Tiger E

Gear 1:x    Jump (eg 11.0 / 7.38 = 1.49) 1   11.0    1.49 2     7.38   1.46 3     5.05   1.485 4     3.4    1.53 5     2.22   1.485 6     1.495  1.458 7     1.025  1.50  8     0.68          (1.455:1 = 1:0.68) Product of jumps: 1:16.052 EXCELLENT!

Lots more interesting stuff, moved from User talk:MinorProphet/Draft subpages/WW2 ZF gearboxes.

Olvars in the Tigers
Full repro by page of the Tiger-Fibel

Spielberger, Panzerkampfwagen Tiger und seine Abarten has the whole Tiger-Fibel at the very end of the book.

Tiger I Information Center Transmission & Steering has an excellent full-colour labelled diagram of an Olvar (which version? - probably the A.) Pity about the white text on a black background. Nul points.

Tigers in Combat, 2 vols. by Wolfgang Schneider, details almost every loss of every single Tiger. Only about 1000 Tiger Is were ever made. From after the battle of Kursk (in June 1943) to May 1945 they fought almost entirely in a defensive role, for which they were not designed. About 45% were completely destroyed by enemy fire. Another 45% or so were destroyed by their own crews for various reasons: mainly a) unrecoverable after getting bogged down; or breaking bridges because of their own weight; or driving into minefields; b) ran out of fuel; c) at least 11 from the same batch caught fire; d) abandoned in retreat, failed because of mechanical problems (often suspension or final drives).

''Modern study of Fgst. nr 250031'' - stunning colour cutaway drawings of Olvar gearbox in the Tiger I,  shot of 8-position gear lever on pp. 98, 136. Wot about reverse? I'm fairly sure that the threaded top of the direction lever - Forwards, Neutral, Reverse, is just shown at the bottom of the pic, with the screw-on knob missing. This is clearly shown in the cutaway pic in the Haynes Tiger Manual, pp. 42-3.

Sledgehammers: Strengths & Failures of Tiger Tanks - interesting, but almost nothing about low-down technical details.


 * ISBN 9781300875376 Panther engine manuals, p. 76. Exchange Chart for German Engine Components, p. 169 incl. Bosch & Solex parts.

Friedli, Repairing the Panzers Vol.1 p. 20 - good stuff about almost complete lack of production line capability in 1930s - wot about Ford and Opel?


 * Daily Journal of V. Battalion of Pz. AOK 4, part of Heeresgruppe South in Soviet Union: (p. 160)
 * Long useful discussion about whether there really was a shortage of spare parts. There were many positive reports about availability. Following up complaints discovered laziness at the depots, inefficiency, and unauthorised personnel bypassing the approved distribution system. Also attempts by individual units to build up their own stock led to over-ordering. Repairing the Panzers Vol.1, p. 152-4 Not only parts but other equipment and machine tools eg "Batteries, fire extinguishers, trolley-jacks, camo paint, canvas covers, screw thread grinders, fuel hand pumps (for fuel barrels) with hoses, blowtorches, complete tool sets." Repairing the Panzers Vol.1, p. 155. 10 July 1943. Drive with Guderian over the battlefield. Troops often cannibalized damaged Panthers, esp. for road wheels for immediate repairs. Time was of the essence during an attack.

Repairing the Panzers Vol.1, pp. 158-9.
 * 7 July 1943 (Battle of Kursk): 76 Panthers had failed, 50 through technical failure. The following day, ten aircraft loaded with spare engines would arrive from Magdeburg*, plus 4 G-wagons with spare parts by Blitzpfeil-Transport (priority rail transport) (cf Operation Blitzpfeil-Transport of 1945)


 * "29 May 1941. Tank spare part depots, 400 tons are carried by AGps. for each Armd.Gp. In addition a depot for parts in short supply — near Magdeburg* (parts will be flown to the front)."
 * 13 July 1943. Report that seven aircraft with seven Panther engines, 400 seals and other spare parts are to leave Friedrichshafen Airport for Kharkov on 14 July. (p. 162)
 * 17 July - suggested that damaged engines be returned to Friedrischshafen by the aircraft which bring the new ones. (p. 168)
 * 18 July - two aircraft have arrived from Magdeburg with parts for Tigers for SS-Div. Totenkopf.
 * Schw.Pz.Abt.503 (Tigers) reported from 5 July - 21 September 1943: Effective average 10 Tigers operational per day incl breakdowns of fixed vehicles. Approx. 276,000 tonnes of spare parts used. Damage/failures to the following occurred: 38 engines: 33 transmissions: 18 radiator fan drives: 22 final drives: 20 suspensions: 8 brakes: 3 radiators (pp. 190–191)


 * Organisation of Panzer Regiment 1944 - good line drawings of vehicles in org. chart - WWII Panzer Division Organization | source: Panzers Normandy Then and Now by Eric Lefèvre

Maybach SRG 32 8 145
Fitted to Panzer III Ausf. E-G. Update List of Maybach engines... ✅ Done?


 * NB! Lack of (K) or (M) in engine type doesn't necessarily mean they didn't have one - the HL120 TR had built-in magnetos mounted on the camshaft (Steuerwelle) and no clutch - but the HL120 TRM did have a clutch and one of those big magnetos mounted beside the flywheel (Schnappermagetzunder). J&D, Pz. Tracts pp. 3-2-70 to 71

Kniepkamp requested a 10-speed box for the latest Panzer IIIs, and Insp. 6 requested a semi-automatic one for inexperienced drivers & to reduce fatigue. Pz Tracts 03-2, p. 3-2-3

The HL120 had separate cast iron crankcase, V-barrels and heads. The SRG 32 8 145 had 10+1 gears. (p. 3-2-8)

NB! Although Maybach re-designated the SRG to Variorex in 1939, the terms are not entirely interchangeable. Although they both used pre-selector mechanisms, the terms refer to completely different gearboxes. The SRG used pneumatic and hydraulic circuits, the VG 102 128H was pneumatic (vacuum) only. But the SRG was the only? gearbox that used the dual vacuum/hydraulic pre-selector mechanism. The VG 102 128 in the Sd.Kfz. 10 and 250 apparently had no accelerator/braking clutches and only used vacuum for the gear change.

Nevertheless, on Pz. Tracts p. 3-2-11, J&D quote that "in July 1937 Maybach reported that ZF had a contract to complete 96 of their SRG 328145 for Motor HL120" from March to July 1938. ZF reported that "actual production of the Variorex-Getriebe 328 145 was 23 in 1938, 223 in 1939, 1015 in 1940, and 44 in 1941." Even further confusion. Mind you, these were Maybach products, and ZF 'just' made them under licence and possibly didn't care... Maybe it's a general term to describe semi-auto boxes.

The first Ausf. E was meant to be delivered in May 1938, and all 96 by September 1938. But the gearbox was obviously proving a pig. The very first Panzer III Ausf. E was only accepted the Army Inspectorate in December 1938. (Pz.Tr. 3-2-11). In March 1939 MAN (who were going to do the main assembly) reported that "three transmissions without accelerators (Hochtreiber) are available for installation. ZF stated that no transmissions will be completed in April. The accelerators wouldn't be delivered until 20 April, and 8 to 10 days are needed for transmission conversion."

Thus the whole accelerator clutch mechanism for the SRG/Variorex was invented at this time, and incorporated into the SRG 32 8 145. Numbering scheme: The HL120 did indeed stick out 300 PS, approx. 80 mkp, and reduction ratio was i = 14.5 = 145...! (see Spielberger 1994, Stugs, p. 37) So it all makes sense in the end.

Even so, the first Pz III with the semi-automatic box didn't even reach the assembly area in Poland - the inside of the transmissions were destroyed. (3-2-14) Problems included seized shifting pistons (overheating), siezed forks, and torn 'accelerator mebranes'. (3-2-36) Incorrect factory assembly, poor tolerances were often at fault.
 * I know what an 'accelerator membrane' is, now: part of the vacuum-controlled Gasgeber mounted on or near the engine, and which opens the throttle automatically by a rubber membrane valve, and thus revs the engine when the clutch pedal is depressed. Think vacuum carbs on a motorbike, same principle. The vacuum (i fink) is created by an Autovac with compressed air running through it. How else could they have done it? The Gasgeber revs the engine so that the 'accelerator clutch' (and the 'braking clutch') can synchronise the different speeds of the two gearbox shafts (although they're not actually shafts per se) to shift dog clutches which select the next gear to be engaged when the clutch pedal is released. As it were. MinorProphet (talk) 22:12, 17 March 2022 (UTC)

The HL120 TR did have 2 Steuerwellen Magnetzundern, (Pz. Tracts 3-2-8) the HL120 TRM had the Schnappermagetzunder. (Panzer Tracts 3-02, Panzer III - Ausf. E, F, G. H, p. 3-2-15 and 16)

Panzer Tracts 03-2 p. 3-2-44 - problems with the Maybach Variorex (ex SRG) had been solved by 1941, and in fact gave very reliable service in N. Africa & Russia. Hmmm... It had first appeared by around May 1938, and took three years to fettle. A bit like the length of time to develop a 600 PS V-12, since the HL102 first arrived in around 1937-ish??

Insp. 6 had pushed for the 6+1 SSG 77 to replace the Variorex as far back as autumn 1939. Production of the SSG 77 intended for April 1940 for the Panzer III H. Electro g/box testing in September 1939. (Panzer Tracts 03-2 p. 3-2-68) Also, in Pz.Tr. 3-5-2 (Panzer III Umbau - chassis conversions): A single Z.W.38 (ZugfuhrerWagen) chassis with an ZF electro gearbox, and another single Z.W.38 with the Maybach 10-speed SRG/Variorex 32 8 145 (probably). Also, V.K. 20.01 D, a single chassis with a ZF transmission using compressed air (rather than a vacuum) being tested at St.Johann in January 1942, and had been driven over 6000 km by January 1945, attached to a Daimler-Benz MB809 diesel of 315 PS. (Pz.Tr. 3-5-2) NB! Move to ZF gearboxes draft

Well well, according to J&D, the clutch is attached to the HL120 motor in the Pz. III Ausf. H and onwards, not to the SSG 77 gearbox. (Panzer Tracts 03-2 p. 3-2-70 to 71.) NB! It all depends on which specific Maybach engine is fitted, or what they called it...
 * And indeed, pic of HL120 with clutch at Repairing the Panzers Vol.1, p. 253 [pdf 254], although - typically - the Ausf. Nr. is not guessed at. It's very interesting how different, varied, and specific the particular interests of various authors are. The individual details of the production or experimental Maybach engines and ZF gearboxes are scattered over very many different publications, almost none of which are particularly interested in these recherché items.
 * "The automotive drive train remained unchanged from the first Ausf J to the last Ausf N." (Panzer Tracts 3-03, Panzer III - Ausf. J, L, M & N, p. 3-3-1), namely, Maybach HL120 TRM, La 120 HD clutch (attached to the engine!) and ZF SSG 77 transmission. (Panzer Tracts 3-03, Panzer III - Ausf. J, L, M & N, pp. 3-3-3 to 4).

Variorex VG 10 2 128H
Fitted in Sd.Kfz. 10 and Sd.Kfz. 250 only.

Excellent pic of this pre-selector g/box being replaced on a Sd.Kfz 10 with(out) 2cm flak. Repairing the Panzers Vol.1, p. 225 MinorProphet (talk) 17:49, 8 December 2021 (UTC)

The box was fairly reliable - 3rd Panzer Reconnaissance Battalion reported in April 1943 that only 11 transmissions needed replacing after 5 to 6,000 km: difficulty in shifting gears, two jumping out of gear. Mostly due to inexperienced drivers and frequent changes of driver.(J&D, Pz Tracts sdkfz 250, p. 15-1-78) Engine in the Sd.Kfz. 250 was the HL42 TRKM with 300-watt generator driven by a fanbelt.(J&D, Pz Tracts sdkfz 250, p. 15-1-3) This was very reliable - same 3rd Recce Btn. says engines didn't needed changing, even after around 10,000 km. (J&D, Pz Tracts Sd.Kfz. 250, p. 15-1-78)

Pic on p. 15-1-39 shows the gear change lever and quadrant, Sd.Kfz. 250/6. Possibly the direction lever, pic p. 15-1-30.

The box was changed from Unterdruckschaltung (vacuum-assisted shifting) to Renkschaltung (manual shifting) from the D7p production models of the Sd.Kfz. 250 around July-October 1943. Instructions for this conversion were officially announced by Wa.Pruf 6 in December 1944.(J&D, Pz Tracts sdkfz 250, p. 15-1-17) Hmm, was this a permanent change?

The same idea of manual override was present on the Olvar in the Tigers: the three square-headed lugs (i.e. the tops of the dog clutch shifters) needed to be manually turned fore or aft (eg 2 to 4 o'clock) to engage different ratios, if the hydraulic pre-selector mechanism failed. Hence those long plates on the Olvar with numbers 1, 2, 3, 4 in diamonds. ✅ Yep, got it.

For info:
 * Different patterns of road wheels on half-tracks. Plus 10 small holes on outer circumference on half-track prototype somewhere? J&D?

MinorProphet (talk) 11:06, 10 December 2021 (UTC)

How did the Germans succeed in France?
Copied from main page. MinorProphet (talk) 16:56, 23 July 2022 (UTC)

So, how did the Germans win in France, especially since production of their main battle-tank, the Panzer III, was a year behind schedule? There were only relatively small numbers of IIIs and IVs available, up to around 300 each, and the plentiful Pz. Is and IIs had only MGs and 20mm cannon.

French politics, industry and the military were all horribly broken before the war anyway. Defensive thinking led to the Maginot Line. Only 2 or 3 mobile armoured divisions created in 1938? Morale very low. Dive-bombing was terrifying.

Anthony Thorne, To Lose a Battle, Penguin, 4th ed? p. 221, says there were 349 Pz IIIs, and 278 Pz IVs. There were a total of 800 Char Bs and Somuas. But 80% of French tanks had no radio.(Thorne, p. 222)

One answer, from Jentz, Panzertruppen Vol. 1, pp. 117, 123:
 * "The decisive cause for the German success in battle against French tanks was the fact that the French always fought against the regiment only with a small number of tanks. Therefore it was possible to destroy them with the concentrated fire of our relatively few armour-piercing weapons. It could lead to a very difficult situation if the French employed a large number of Somua tanks against us." (Commander of Pz Rgt 35 (4th Panzer Division), experience report, May 1940: Jentz, Panzertruppen Vol. 1, pp. 117, 123) NB! What were they actually equipped with?

A Panzer officer commented about the "lack of manoeuvrability and the fact that they fight single and in loose formation, not all together under one command." (Thorpe, To Lose A Battle, Penguin, section "Holland: a Matter of Hours", p. 358.)

Apart from the standard towed 3.7cm PaK anti-tank gun, the Panzer IIIs up to early Gs used the 3.7 cm KwK 36 (ie basically the same Pak 36); and early Panzer IVs had the 7.5 cm KwK 37; both fired armour-piercing ammo, but only the Panzer IV's gun with AP ammo was really capable of taking out a Char B1 Bis, and that at 100m. The Somua S35s and Char B1 Bis were heavily armoured (40mm and 60 mm frontal armour respectively), and often resisted considerable attack. Often the German gunners had to shoot their tracks off to stop them. Even the Panzer IV up to September 1940 only had 30 mm frontal armour. There were literally no other standard anti-tank guns (the 50mm PaK didn't appear until late 1940). Both the divisional 10.5 cm leFH 18 - among its 28 types of ammo(!) - and 15 cm sFH 18 cannon fired AP shot (Granate 39 i fink) (the infantry 15 cm sIG 33 howitzer didn't): but how often does attacking standard towed artillery get to shoot at enemy tanks?
 * Well, if you can get an 88mm FlaK gun into action relatively swiftly (no need to dismount it even, with direct fire), that might be the only option, since the Char B1 bis was essentially invulnerable to standard anti-tank gun or tank fire. See end of next section.

For Operation Sealion in August 1940, there were 90 Panzer IIIs with 3.7 cm KwK guns (Ausf. E-F, some early G's),(J&D Pz Tr 3-2-46) a mere five with 5 cm KwK (most Ausf. G and all H's), and 28 Panzer IVs ready for service.(Spielberger 1992, Panzer IV & variants, p. 39) Mind you, the BEF had left everything in France, there wasn't going to have been much opposition.

From User:MinorProphet/Draft subpages/German aluminium casting alloys made during WW2:


 * Tooze...says that Germany had *no* anti-tank guns capable of defeating a Char B1 bis. German combat reports say they did. What was actually the case? Well, the only anti-tank gun used by the Germans apart from the 3.7 cm PaK 36 was the Panzerjäger I which mounted the Czech 4,7cm KPÚV vz. 38 (German designation "4.7 cm PaK (t)" on a Panzer I Ausf. B chassis (SdKfz 101). 202 of these were produced in 1940 and 1941 [says Wiki article - wot says Panzer Tracts 23? Nowt, coz they weren't yer actual tanks: see Panzerjagers, Pz Tracts 7-1, p. 7-46.] Hmm, there were 40 made in March 1940, 60 made in April 1940 and 30 in May 1940.(Pz Tr 7-1, p. 7-46) NB with 5-sided gun shields = 130 or 132 total, in 5 Abteilungen of 3 companies of 9 = 27 guns each.


 * For Operation Barbarossa, a further 70 were contracted to Krupp-Essen in October 1940, 60 delivered to Klockner-Humbolt-Deutz and 10 to Alkett. 30 accepted by Waffenamt in December 1940 and 30 in February 1941.(Pz Tr 7-1, Panzerjaeger, p. 7-56.) NB with 7-sided gun shields ((Pz Tr 7-1, p. 7-56) So the figures in the Wiki article seem wrong. Posted a query on Talk:Panzerjäger I. Hmm, should have gone to Specsavers. I just can't read, is all. There were indeed 202 produced per J&D.


 * Combat report on p. 7-58 says "during the campaign in France they were very effective against heavily armored French tanks." But there were only a maximum of 130 in the whole of the Belgium/Holland/French campaigns, and how many French tanks did they account for?


 * Not to be confused with the 15 cm sIG 33 (Sf) auf Panzerkampfwagen I Ausf B which was the standard early SP heavy infantry gun: but the SiG 33 didn't fire anti-tank shells. See 15 cm sIG 33


 * Careful! The book of pix of the 1st Panzer Division (Riebenstahl, The 1st Panzer Division 1935-1945: A pictorial history. Schiffer) has plenty of these in France - but check if they are the Panzerjäger I or the sIG 33 SP artillery.
 * No, they are 15 cm heavy infantry guns, and there are no pics of Panzerjager Is. So maybe they were assigned at the Corps level and fought "with" or "in support of" the Panzer divisions. #521 assigned to Gruppe von Kleist on 10 May 1940: were in the Battle of Belgium in the Ardennes, so fought against the French at eg Battle of Sedan (1940): the three others (#616, #643, and #670) were sent into action as they became combat ready. (Pz Tr 7-1, p. 7-52) The "clutch steering unit" often broke. No reports of engine/gearbox failures. Slower than everything else, no more than 30 kph, 15-30 mins rest after the first 20 km, then every 30 km for cooling down, lubrication & repairs. (Pz Tr. 7-1, p. 7-53) Marching with either motorised infantry or tanks was a mistake, it overstressed everything. Best to march alone. Took take up to 8 days for left-behind vehicles to make their way to the Abteilung with help of special signs. But the guns were good and the crews liked them. Good against 45-50 mm armour at 500-600 metres, even tracks hit at 1000 metres ricocheted through the belly.(Pz Tr. 7-1, p. 7-54)
 * Also NB! Had a Maybach NL38 TR (100 PS @3,000 rpm), and a ZF FG31...(Pz Tr 7-1, p. 7-61)


 * For Barbarossa, (Pz. Tr. 7-1, p 7-56)

521 to XXIV Army Corps, 2nd Pz Gr., Army Group Mitte - (Tessin Vol. 11 pp. 61-2 [pdf 33]], destroyed Stalingrad Jan. '43) 529 to VII Corps, 4th AOK, Mitte (Tessin Vol 11 p. 83 [44], formed 24.1.41 from Pz.Jg.Abt. 169) 616 to 4th Pz Gr., Nord - (Tessin vol 11, pp. 312-3 [159]) 643 to XXXIX Corps, 3rd Pz. Gr., Mitte (Tessin vol 12 p. 25 [15]) 670 to 1st Pz. Gr., Sud (Tessin vol 12 p. 79 [42] - 12.5.1940 equipped with Sfl., +7.62 cm Sfl in 1942, died Stalingrad Jan '43)


 * Or maybe I'm finking of the the long propaganda film https://archive.org/details/1941-Sieg-im-Westen Sieg im Westen? The 5 cm PaK 38 certainly wasn't used until Operation Barbarossa in June 1941. Thus Tooze is correct if he means *native* German anti-tank weapons, but the self-propelled Panzerjäger I used the Czech 4.7cm AT gun. So he's wrong in this case.


 * Tooze in this book gives Erich von Manstein the credit for success, using Napoleon's strategy of concentrating his forces at a single point with greater force than the defenders.(Tooze, pp. 403-4) Later (see previous section) he puts it down to 'the triumph of the will'.

Summary
Thus only the Panzerjäger I (self-propelled 47mm anti-tank gun), or the Pz IV at very close range, had any chance of stopping the Char B1 Bis. Or the 8.8 cm FlaK, or the 10.5 cm divisional howitzer, perhaps more likely.

Un-needed diversion
...as to the distribution of French tanks, and exactly which French Somua-equipped units the German 1st & 2nd Pz Divs (which had the most PZ IIIs i fink) came up against.

Well, between 1931 and 1935, French industry had only been producing about three tanks per month. Production was artisanal and manufacture of parts was sub-contracted. Even on 1 January 1937, the three battalions equipped with Char D1s had the most modern tanks in the French army, and these were largely worn out.

Renault, for example, had negotiated fixed-price contracts, and costs of raw materials had skyrocketed. A number of other bureaucratic impediments slowed the delivery of tanks to the French army; this affected the timely formation and training of new tank units. Large numbers tanks had not been delivered until a few months before the German attack, significantly undermining the whole French tank force in 1940.

The Somua S35s were issued to the Cavalry units, the 2e & 3e DLM (French: 2ème division légère mécanique, 2ème DLM).Le Somua S35 (in French), p. 42 [5]. Compared with the 3rd & 4th Panzer Divisions, there were 176 Somuas against 82 Panzer IIIs and 50 Panzer IVs. The concept of a highly mobile mechanised division was alien to French army thinking in the 1930s, which was wedded to the idea of relatively static defensive actions eg Maginot Line thinking. There were around 400 Char B1/bis supporting the infantry. The majority of the most capable tanks, the Somua S 35s were allocated to the cavalry regiments in the 1st & 2nd DLM [and/or the 3rd].(Sumner, Ian; Vauvillier, Francois; Chapell, Mike (1998) The French Army 1939-1945 (1). Osprey. |series=Men-at-arms 315, pp. 13-14)

"Adroitly supported by Stukas, powerful concentrations of tanks from both the 3rd and 4th Panzer Divisions hammered at Prioux’s two Light Mechanized Divisions." (Thorpe, To Lose A Battle, Penguin, section "Holland: a Matter of Hours", p. 358.) MinorProphet (talk) 16:56, 23 July 2022 (UTC)

Zaloga has a table showing the French tank strengths. The cavalry DLM (Divisions Légeres Motorisées: 1st formed 1953-6, 2nd formed 1937, 3rd by 1940) had the Hotchkiss 35/39 and the Somua S-35, plus Renault AMR-35 light tanks and Panhard 178 armoured cars. The Divisions Cuirassées (DCr) were only formed in January 1940 and had the Hotchkiss 35/39 and the Char B1 bis. Often held up by lack of refuelling tractors.

The major tank vs tank battles during the French campaign were: 2nd & 3rd DLM at Hannut and Gembloux, May 11-15; 1st DCr at Flavion, May 15; and 3rd DCr at Stonne, May 15-6. (Zaloga, map,

The Somuas and Char B1s were very robust, and were fairly impervious to the 37mm Paks and guns of the Pz III and the (short-barrelled?) 75mm of the Pz IV - often only knocked out by 88mm or 105mm fire. :"The direct combat losses were due primarily to the Germans’ improvised use of heavy artillery, with the vast majority due to 105mm field guns and 88mm Flak guns which were the only weapons that could reliably penetrate the Char B1 bis’ heavy armor."

Eg The 1. FlakKorps on 10th July 1940 reported it had destroyed 372 planes in the air, 252 on the ground, 47 tanks [of any size], 30 bunkers and 1 warship. Towed by Sd.Kfz. 7s and able to fire without dismounting from the towing axles, the 88mm Flak 36 was one of the only guns capable of defeating a Char B1 bis. The Panzer IV certainly couldn't.

Eg The 37e BCC (Batalion des Chars de Combat - Tank Battalion) of the 1e DCr (Division Cuirasée - Armored Division) lost 21 Char B1 bis tanks on 15 May near Flavion, mostly in engagements with the 5th Panzer Division's 105mm field artillery. "The panzer crews were shocked to see their 37mm and 75mm rounds bounce off the Char B1 bis..."

Jentz also says that the Char B1 bis was impervious to single strikes of armour-piercing shells from the 3.7 cm PaK, 3.7 cm KwK (Pz III) or 7.5 cm KwK (Pz IV) - but the 60 mm armour could be defeated by multiple 3.7 cm hits at close range, or by AP 10.5 cm leFH 18 (standard divisional artillery), or by 8.8 cm Flak. The 102. Flakregiment attached to Guderian's XIX Army Corps claimed only 9 kills by 8.8 cm Flak L/56, and Jentz says they were not a major factor in defeating French armour during Guderian's advance towards the Channel.











Panzer III strengths - why?
According to Panzer Tracts 3-2-12, only 50 Panzer III Ausf. E had been accepted by the Army inspectors by August 1939, with another 40 made in September. Only about 70 Ausf. A-D were made: Ausf. A, 10; B, 15; C, 15; D, 30, total c70.(Spielberger Panzer III and variants, pp. 140–143)

In Armoured Bears, 3rd Panzer Div in WW2, Vol. 1 p. [70], at the start of the Polish campaign the 6th Panzer Regiment (3rd Pz Brigade, along with the 5th Pz Regt) had 55 Panzer	I, 55 Panzer II, a mere 3 Panzer III, 6 Panzer IV, 132 trucks, 60 staff cars, and 114 motorcycles. Around 120 tanks total.

By the end of April 1940, the 3rd Pz division had received its first Panzer III’s (thirteen) and Panzer IV’s (twenty), which were distributed to the two regiments.(Armoured Bears, 3rd Panzer Div in WW2, Vol. 1 p. [96])

4th Panzer Division in September 1939 had roughly 341 tanks, including 183 Panzer I, 130 Panzer II, apparently no Panzer IIIs, 12 Panzer IV and 16 PzBef

Even by May 1940 there were only around 350 Panzer IIIs in all divisions. (Zaloga, Pz IV vs Char B1 bis p. 49)

Why worry? Basically, the vast majority of tanks used in the Polish invasion were Panzer I and IIs, with only a very few III and IVs. The Polish forces were woefully outnumbered, and only the 150 or so 7TPs (ex Vickers 6-ton) had a 37mm gun. Sadly, Tanks of the Polish Armoured Forces is virtually un-referenced. The frontal armour on the early Panzer IIIs was easily penetrated by even 20mm French AT guns.