User talk:MinorProphet/Draft subpages/WW2 ZF gearboxes

Contents moved to User talk:MinorProphet/Draft subpages/WW2 Maybach gearboxes. MinorProphet (talk) 10:26, 10 December 2021 (UTC)

I haven't been dating most of these entries, but I have added some s. MinorProphet (talk) 21:43, 22 March 2022 (UTC)

Argh
There is apparently no single book dealing with the ZF gearboxes by themselves. The details are scattered over the histories of the tanks and half-tracks they were installed in. Milsom 1975 lists all the tank ones, and Spielberger is often useful, but Jentz & Doyle with their Panzer Tracts series and other publications seem to be the most reliable, although there are some irritating errors which could have been ironed out by a good proofreader.

Through my library I now have access to a large number of sources. Many of them disagree in one way or another. I am tempted to go with Jentz and Doyle's Panzer Tracts, although some of them have some annoying inconsistencies, which you could term errors or mistakes (e.g. SFG 75 vs. SSG 75 in Panzer IIIs. See Table 1 in the article.) I think I have resolved several of these.

Maybe it's best to go through the whole damn lot again, vehicle by vehicle, Ausf. by Ausf., maker's version by version, source by source, writing them all down ref by ref, and see what comes out. MinorProphet (talk) 21:43, 22 March 2022 (UTC)

Sd.Kfz. 8
This is the original reason for this entire article.

Despite extensive research and discussion as detailed at Talk:Sd.Kfz. 8, the specific model number of any the four types of gearbox fitted to the 12-ton half-track remains highly elusive. The German and English versions of Spielberger's Halbketten..., Halftracks of the German Wehrmacht list (in more or less detail) all of the gearboxes fitted to all models of the half-tracks. But they differ considerably, the English version stating that many models of different Sd.Kfzs had ZF pre-selector transmissions. This is the only source that makes these claims, and I am particularly skeptical of them. Unfortunately Jentz & Doyle don't cover the 12-ton Sd.Kfz. 8 in their Panzer Tracts series, probably the most detailed and thorough sources of all. Although it was the first of all the series to be designed, there were far fewer of them made than any other German half-track. The mystery continues... The preponderance of sources saying they were all manual, non-synchro, 4+1 x 2 transmissions leads me to discount Spielberger as reliable in this case. Furthermore, as this article shows, ZF simply didn't make a pre-selector gearbox for any German production series military vehicle.

Here's the list from Spielberger's English edition of Halftracks of the German Wehrmacht that SV66 kindly posted at Talk:Sd.Kfz. 8: This might serve as a starting point, if only to rebut Spielberger's more outlandish statements (in green). MinorProphet (talk) 22:48, 14 December 2021 (UTC)


 * Sd.Kfz. 10
 * D6: Demag-Adler 6/1 + NL38 TRK 83 PS @2400, engine nos 50001 - 50068 ✅ Confirmed by (Pz Tracts, p. 22-1-5, 8)
 * D7: HK 601(??) Maybach Variorex 7/3 or 8/3 ✅ Confirmed by (Pz Tracts, p. 22-1-8). Used NL38 TRKM, [new head + shorter pistons for lower compression ratio for OZ 74 octane rating fuel], engine nos. 50069 onwards, available from 1 October 1938.


 * Sd.Kfz. 11
 * HL kl 5: Hansa-Lloyd-Goliath 4/1 x2 ✅ - All sources confirm
 * HL kl 6: Hanomag U 50 4/1 x2 ✅ - All sources confirm


 * Sd.Kfz. 6
 * BNL 5: ZF pre-selector 4/1 x 2.  -  Well, according to US Handbook (ref in main table), and the German edition of Spielberger Halftracks, it was a ZF G45 (4+1 x2). But J&D, Pz.Tr. 22-3, p. 22-3-5, say it was a ZG45 (8 forward, 2 reverse (4+1 x2) within the gearbox), plus another hi-lo gearbox (x2) in a second, separate housing (probably with the diff and final drive) giving a total of 16 forward and 4 reverse gears (4+1 x 2 x 2), although many ratios were probably not used. The engine in this version was an NL35 TU. Thus the clutch would have been supplied by ZF (no 'K' in the engine model number). You can see in the two gear levers for speed shift and hi-lo the pic on p. 22-3-7.
 * Plus, on the title page of the official parts list (Ersatzteilliste) for the BNL 7, it shows the the spelling of the BN factory type, "BNL 7" and "DBL 7" in all caps, not BN 1 7 etc. as Jentz & Doyle would have it. Seifert (Waffen Arsenal S 35) agrees.
 * BNL 7: ditto (ZF pre-selector 4/1 x 2)  Actually a G 45v 4+1 (x2 in separate diff housing) (Pz.Tr. 22-3-12 & -13) See Ersatzteilliste (Spare Parts List) for BNL 7, Figure 14 (around p. 60): and also Sawicki and Ledwoch, Militaria 287, Mittlere ZgKw 5t: Sd Kfz 6, p. 51, where the labelled photo shows very clearly the hand brake, gear shift lever, the fore-and-aft "gear box reductor lever" and winch lever (Nos. 4, 5, 6, & 7 in the photo.)
 * BN L 8: ditto  Un-named 4-1 x2 in J&D
 * BN 9: ditto  Un-named 4-1 x2
 * BN 11 V (Versuch?): had a Maybach HL49 + a 10-speed semi-automatic BN V gearbox (apparently also made by Bussing-NAG), [ MinorProphet (talk) 15:53, 27 March 2022 (UTC) ] but only one vehicle was completed. (Pz.Tr. 22-3-30)


 * Sd.Kfz. 7
 * KM m 8: ZF Aphon ZG 55 4/1 x2. Argh everyone says it was a ZG55, but it must have been a G55 with the HL52 TU with no clutch. (PzTr p. 22-4-28) Unless ZF changed the designation of the ZG between the ZG 45 and the ZG 55, one with and without a clutch. Aargh, see section below on Sd.Kfz. 7 boxes.
 * KM m 9: ZF Aphon G 55 4/1 x2 ✅ Confirmed by (PzTr p. 22-4-30)
 * KM m 10: ditto ✅ Confirmed by (PzTr p. 22-4-36)
 * KM m 11 ZF pre-selector 4/1 x2  J&D state a ZG 55 (PzTr 22-4-36)
 * Breda 61 ZF pre-selector 5/1 x2  J&D, (Pz.Tr. 22-4-84) give a ZF G55 4+1, even stating their source, D607/13, 1944 edition.


 * Sd.Kfz. 8 ( Added by MinorProphet (talk) 15:09, 20 April 2021 (UTC) )
 * DB s 7: DB pre-selector 4/1 x2 Daimler-Benz may well have fitted a pre-selector gearbox: they certainly stuck one in the max. de luxe WO7 series. "In 1930/1931 Mercedes announced a sports car with a 7.7 litre supercharged straight-eight, with a special Mercedes-Benz-Maybach multiple-range gearbox giving six speeds. [...] The change is effected by the employment of the partial vacuum in the inlet manifold, controlled from the steering wheel." Possibly the Mercedes-Benz 770 or  Großer Mercedes. Motor Sport, October 1930. This was a 3-speed gearbox with long fore-and-aft lever on the floor, with a three-speed overdrive selector mounted on the steering column. See List of WWII Maybach engines for more refs.
 * The Maybach Zeppelin DS8 also had the same DSO8 engine as the 12-tonner. "A 1938 Maybach Maybach Zeppelin was fitted with a Variorex eight-speed gearbox (both the first 8-speed and first 8-speed manual gearbox) with a vacuum shift." - sold for 1.3 million Euros in 2012.  Maybe a lowly half-track might have got one as well...
 * As an aside, the SSG 77 gearbox fitted in the Panzer III (made by Mercedes) has the Mercedes and the ZF logos on both sides, so there seems to have been some sort of collaboration going on between them...
 * Just to clarify things: Wilhelm Maybach designed Daimler engines (Daimler Motoren Gesellschaft, DMG), and designed the DMG-Phoenix, the first 4-cylinder car engine, in 1894. Emil Jellinek sold Panhards in France, who owned the French license and name for Daimlers. His daughter was named Mercedes. Maybach designed the highly successful Daimler-Mercedes car and its engine (the Mercedes 35 PS) for Jellinek in 1900. Daimler registered the Mercedes trade mark in 1902, and put the name on the radiators of its passenger cars. Maybach, technical director of DMG, resigned in 1907 to form what became Maybach-Motorenbau GmbH with his son Karl in 1912. Daimler (DMG) merged with Carl Benz & Co. in 1926 to form Daimler-Benz AG. Wilhelm Maybach died in 1929. Thus Mercedes is a wholly-owned branch of Daimler-Benz. Now you know. Sort of. MinorProphet (talk) 15:53, 27 March 2022 (UTC)
 * DB s 8: ditto Why not?
 * DB 9: ZF Allklauen 4/1 x2  If true, this would be a constant-mesh, synchro box like the AK 7-200, see above. However, ZF did make a 4-speed synchro gearbox in 1934, the „Allsynchron“-Getriebe AK 4 S in 1934, with what looks very much like a pre-selector mechanism of the Soden type on top. ( With cutaway photo. But looks a bit small compared to the following... )
 * Actually, Allklauen is simply ZF's name for their constant-mesh gearboxes, made in both synchro and non-synchro versions. All the ZF half-track gearboxes were non-synchro, and the tank ones were synchro. So a 4/1 x2 is fine. ✅ MinorProphet (talk) 03:20, 21 June 2022 (UTC)
 * DB 10: ZF Spl. pre-selector 4/1 x2.  The original manual for the Sd.Kfz. 8 Typ DB 10 shows most obviously a standard ZF 4+1 x 2 gearbox, whatever the rest of the world might say. Figures (Bilden) 4 &  5 show:
 * Schalthebel für Schaltgetriebe (change lever for speed-shift gearbox)
 * Schalthebel für Untersetz?getriebe (Unterseßer?getriebe) (overdrive or hi-lo box)
 * Schalthebel für Seilwindeantrieb (winch drive} (PTO is No. 9 on opposite page)
 * Another view of the driver's position in Bild 8. There's no clutch, since it was attached to a HL85 TUKRM ('K' = clutch) in the 12-tonner.


 * SD.Kfz. 9
 * FM gr 1: ZF Aphon 4/1 x2 ✅
 * F2: ZF G 65 VL 230 4/1 x2 ✅ OK, everyone knows this one.
 * F3: ditto ✅

Thus by my reckoning Spielberger gets 8 ticks, 7 crosses, 4 question marks and one double-cross (hah!) He claims that at least some models of the Sd.Kfz. 6, 7, and 8 all had a "ZF pre-selector", although ZF doesn't appear to have made any such gearbox for half-tracks, or for tanks for domestic consumption for that matter.
 * Summary

A lengthy and mostly enjoyable gathering of info about both ZF and Maybach gearboxes has led me to suppose most strongly that (apart from the 1939-ish EV 12 electromagnetic gearbox fitted to the Stridsvagn m/42 which failed because of manufacturing defects, and perhaps the AK 4 S), ZF didn't make any wartime pre-selector gearboxes for tanks and AFVs at all. I'm afraid that almost all of Spielberger's claims in the English edition of Halftracks of the German Army that the Sd.Kfz. 6, 7 & 8 used such a gearbox appear to be incorrect. MinorProphet (talk) 21:43, 22 March 2022 (UTC)

German technical publications for the Sd.Kfz. 8:
 * Still hunting for info re 12-tonner gearbox:
 * D 608/7 Schwerer Zugkraftwagen 12t (Sd.Kfz. 8) Typ DB 9 Gerätbeschreibung und Bedienungsanweisung zum Fahrgestell und Aufbau 27.11.1939
 * D 608/8 Schwerer Zugkraftwagen 12t (Sd.Kfz. 8) Typ DB s8 & DB 9 Ersatzteilliste zum Fahrgestell und Aufbau 09.10.1939
 * D 608/11 Schwerer Zugkraftwagen 12t (Sd.Kfz. 8) Typ DB 10 Gerätbeschreibung und Bedienungsanweisung zum Fahrgestell und Aufbau 12.01.1940
 * D 608/12 Schwerer Zugkraftwagen 12t (Sd.Kfz. 8) Typ DB 10 Ersatzteilliste zum Fahrgestell und Aufbau 22.01.1942
 * D 608/211a Schwerer Zugkraftwagen 12t (Sd.Kfz. 8) Typ DB 10 Sonderausrüstung für Winterbetrieb 1.07.194

Also, LoneSentry.com has gone, with the digitised US Catalogue of German equipment, although the whole of it is on Wayback.

MinorProphet (talk) 21:43, 22 March 2022 (UTC)

Kb 40 D
According to J&D, Pz Tracts 7-3, p. 7-227, a report by Krupp stated that the 8.8 cm Pak 43 Kp auf Waffenträger (Ardelt-Krupp Waffenträger) was fitted with an HL42, steering gear from a 3-ton Sd.Kfz. 11, and a "4-speed Kb 40 D" gearbox by Zahnradfabrik. This is not a typical ZF gearbox model number. See also p. 7-226, where the transmission from an RSO was to be used. J&D give bare details of the 7.5 cm Pak 40/4 auf RSO, saying it was a 4+1 box with a Steyr V-8 3.5 litre developing 70 PS @ 2500. (Pz Tracts 7-3, p. 7-180)

Apparently ZF did make a Kb 40 D, fitted in a little post-war railway diesel-powered car of 52 PS. Klv 61 - Kleinstturmtriebwagen

Details of the SWS are on Panzer Tracts 22-3 (Sd.Kfz. 6 etc.) p. 22-3-48, which says a Kb 40 D transmission was fitted, with no manufacturer. Reinhard Frank in Mittlerer Zugkraftwagen, p. 19 says the SWS had a ZF Kb 40 D. Milsom in German Half-Tracks of WW2, p. 75 says it was a "sliding-mesh, non-synchromesh type", and on p. 94 says it was a ZF with 4 forward and 2 reverse. But ZF hadn't made a sliding-mesh gearbox since 1928 when they introduced the Aphon series, I reckon this is bollocks. Milsom also claims ZF sliding-mesh boxes for the Klöckner-Humboldt-Deutz 2-ton Maultier (Sd. Kfz.3c) and the 4½-ton Mecerdes-Benz Maultier with MB 112 PS engine (Sd.Kfz.3/5) on p. 60. Evidently suffers from Spielberger-itis.

The HL42 (coupled with this Kb 40 D as above) sticks out around 100 PS - anything from an NL35 to the HL54 (only manages 115 PS) is coupled with a G45, so it's quite possible that the Kb 40 D was rated for 40 mkp.

Well, ZF now classify it as a 'truck gearbox', see Historical Manual Transmissions for Trucks and Passenger Cars, p. 1. ZF Friedrichshafen AG. 1 October 2021. Retrieved 20 December 2021. MinorProphet (talk) 23:07, 20 December 2021 (UTC)

Gearboxes fitted to the Sd.Kfz 7
All of Spielberger, Jentz & Doyle, and Milsom 1975 state in their texts that the gearbox fitted in the first Sd.Kfz 7, the KM m8, was a ZG 55. However, Hilary Doyle's detailed and accurate drawings of the Krauss-Maffei m8 (Pz Tracts 22-4, p. 22-4-39) and the KM m10 (Pz.Tr. 22-4, pp. 22-4-43) unquestionably show not a ZG 55, but almost certainly a 'semi-unit' G45 or G55 (clutch, hi-lo gearbox, and 4+1 speed-shift box all bolted together), attached directly to the clutchless HL52 TU engine. The above two transmissions are certainly the same design of semi-unit gearbox, only differing slightly in shape. The stats on p. 22-4-28 also confirm an HL52 TU, which by definition has no clutch. See List of WWII Maybach engines

On the other hand, Doyle's drawing of the m11 chassis (Pz.Tr. 22-4, pp. 22-4-45) shows a completely different arrangement, with the HL62 TUK engine complete with standard factory-fitted clutch, notably connected by a propeller shaft to the separate, rectangular, clutchless ZG55 gearbox of completely unit construction where the manually operated change-speed gearbox and the dual-range hi-lo box are contained in a single casing. Compare p. 22-4-43 (KM m 10), where the front driving sprockets are much further back, vertically in line with the driver's cab side. The final drive is a separate unit behind the gearbox. On p. -45 (KM m 11), the front drive sprockets are much further forward, since the final drives/diffs are directly attached to the gearbox. Plus another set of road wheels. In this case I'm taking Doyle as the RS.

Anyway, none of the HL 52, 57, or 62 TU engines as fitted to the earlier Sd.Kfz 7s could possibly have ever driven the ZG55, since none has a factory clutch.

Thus: contra Spielberger, Jentz's text, and Milsom, and as per Doyle's drawings, I suggest strongly (WP:OR?) that the KM m8, m9 and m10 (all with TU engines) used the semi-unit G45? or G55, followed by a separate final drive to the wheels: but all sources definitely agree that the KM m11 powered by the HL62 TUK was fitted with the clutchless ZG55 with final drives directly attached. A proposed KN m12 was slated to have the Maybach HL80 engine, but neither made it into series production.

Stuff about the mysterious ZF SSG 75 vs. the Maybach SRG 32 8 145
"Previous deliveries [of the Panzer III] utilized the proven SFG 75, SSG 75 or SSG 76." (Panzer Tracts p. 3-2-12.) NB! This is from a director of Daimler-Benz named Werlin in June 1939, replying to an official questionnaire on the status of the Panzer III at Factory 40. [Which? Hmm.] According to official reports, the Maybach SRG 32 8 145 wasn't working at all, holding up tank production in June 1939. (Panzer Tracts p. 3-2-11 and -12.) Maybach added an 'accelerator clutch' to the upper part of the main clutch housing of the SRG 32 8 145. (Panzer Tracts pp. 3-2-11 to -12) (Pix at Repairing the Panzers Vol.1, pp. 65-66) It was decided to re-install the proven ZF SSG 76 from Fall 1939 onwards (NB This didn't happen. Production of the Ausf. E's only really started getting going around this date, and the Waffenamt was forced to deliver about 1,400 tanks up to 7./Z.W [ie the start of the Ausf.H's].) (Pz Tracts 3-2, p. 3-2-14)

But this previously-used ZF SSG 76 gearbox needed to mate with the final drive used in the Ausf. E–G with the Maybach SRG 32 8 145, and the SSG 76 was partially re-designed to become the SSG 77. This took some time, because "a different transmission couldn't be acquired fast enough." (Pz Tracts 3-2, p. 3-2-14)

[SSG 75 - ha! this mysterious SSG 75 gearbox appears in various places, and here is a statement from a Director of Daimler-Benz that it DID exist. It could be a mistake on his part, or maybe it did exist but was only installed on a few vehicles. But when or where was it actually installed on any Panzer III Ausf. A–D ??? Pz. Tracts 3-1, states SRG 75 on p. 3-1-32, and SSG 75 on 3-1-39. This seems more like a misprint or error. SFG = Synchronisiert[er] Funf-Gang Getriebe. SSG = Synchronisiert[er] Sechs-Gang Getriebe. Did a six-speed SSG 75 actually exist??? See note at ZF Gearboxes, Table 1.]

Stuff about the SFG 75, SSG 76 and SSG 77
Taken from refnote in See Main Table 1 User:MinorProphet/Draft subpages/WW2 ZF gearboxes

In the Pz. III Ausf. A (SFG 75) and B through D (SSG 76), the gearbox was driven by the Maybach HL108, which developed 75 PS @ 2000 rpm.(Panzer Tracts 03-01 Panzerkampfwagen III. Ausf. A, B, C & D, p 3-32);(Panzer Tracts 03-04 Panzerbefehlswagen p. 3-4-4, 3-4-6, and 3-4-12 for the Pz.Bef.wg. Ausf. D1.) The engine fitted to the Ausf. E and onwards was the HL120 TR/TRM, which obviously produced more torque, although I haven't yet discovered the actual figure... Well, the central '8' in the Maybach SRG 32 8 145 indicates 80–89 mkg, so there's one clue. So, the SSG 76 and 77 must have been capable of a similar capability. Good. Getting there.

The semi-auto Maybach SRG 32 8 145 fitted to the Ausf. E-G may well have had a different steering mechanism to the Ausf. D. Reason: "The SSG 76 in the Ausf. D [also fitted to most Panzer IVs] had to be altered to connect with the steering mechanism used in the Ausf. E-G [which used the Maybach SRG 32 8 145]. This variant was called the SSG 77".

NB!! Check steering mechanisms and Fichtel & Sachs clutch types fitted to Ausf. D, E-G, and H onwards, and all Panzer IVs! - see table-thing below.

As demonstrated (i fink) in the main article—or these notes or elsewhere eg Maybach gearbox article—the designation of a ZF gearbox doesn't necessarily reflect its true torque capacity. The SSG 77 probably had the same torque capacity as the SSG 76 as used with the HL108 TR, since the SSG 76 was also fitted in all Panzer IVs from the Ausf. B onwards, which all used the Maybach HL120, as did the Panzer IIIs from Ausf. E onwards. Both the SSG 76 and 77 seem to have had a greater torque capacity than the SFG 75.

As the notes show, the SSG 76 was introduced on the Panzer III and IV at almost exactly the same time.

Tank                  Engine (PS)       Clutch          Gearbox          Steering Pz III Ausf. A-C      HL108 (230-270)                    SFG 75 Pz IV Ausf. A            "                                 " Pz III Ausf. D        HL108                             SSG 76 Pz III Ausf. E        HL120 TR (265)                    SRG 32 8 145 Stug III Ausf. A          "                                  " Pz IV Ausf. B, early C    "                             SSG 76  Pz III Ausf. F-G       HL120 TRM (272)                   SRG 32 8 145 Pz IV Ausf. later C-J      "                             SSG 76 PZ III Ausf. H-N      HL120 TRM (272)  F&S LA 120/HDA   SSG 77           DB/Wilson clutch-type

Pretty smart, the Fichtel & Sachs dry 3-plate LA 120 HDA clutch had the same number as the Maybach engine.(Spielberger Panzer III & variants, pp. 147–152)

What I hadn't realised: By June 1937 already there were plans to standardise the Panzer chassis: the Panzer IV was going to use the new Panzer III 4.Serie/Z.W (Ausf. E) chassis with torsion bar suspension and the Maybach pre-selector 10-speed gearbox. Krupp was told to cease development on the Panzer IV chassis. However, problems with the gearbox especially meant that already by May 1937 it was known that the Pz III Ausf. E wouldn't be ready until April 1938. This caused an 8-month gap in Pz IV production. (Pz Tr 4-0 p. 4-24 - the old one) In fact, it would barely be ready by September 1939 - there were only 51 Pz IIIs total in the Polish Campaign, and over 50% of them would be destroyed. This meant that all development on the Panzer IV chassis stopped, and it carried on throughout most of the war with the 8-bogie leaf suspension, the HL120 engine and the SSG 76 gearbox.(Pz Tr 4-0 p. 4-24) All the subsequent Ausf. models from the Ausf. C onwards just added more armour and a bigger gun. Then you get the Panzer III/IV with the flak wagons etc. in 1944 or so.

Attempt to determine max. torque of various engines/gearboxen
Moved from main article. MinorProphet (talk) 14:16, 8 July 2023 (UTC)

It seems likely that most of the ZF model numbers indicate the gearbox's maximum torque. A couple of books state the max. torque of some gearboxes &/or engines: some very approximate calculations follow to see if this might generally be the case.

Table-thing to consolidate known power & torque of engines & gearboxes with sources

Engine     PS @ rpm    mkg @ rpm   G/box   Torque  TRR* Application        Refs Krupp M305  60  2500                FG 35  35          Panzer I Ausf. A NL38 TUK S 100  3000   25   1700     G 45  45          Sd.Kfz. 6 BNL 8 HL52       120         54? SSG 45 45          La.S.100, pre-Pz II                                                           Sd.Kfz. 7 KM m8     2a ? HL57 TR    130  2600   ?? SSG 45 45          Pz II                 HL62 TR     140  2600   45          SSG 45  45          Pz II, SdKfz 7 HL108 TR   300  2800   79          SFG 75  75          Pz III A              HL108 TR    250  3000   75   2000   SFG 75  75          Pz III A              HL108 TR    250  2800   75   2000   SSG 76  76          Pz III D1 (PzBefWg) HL120 TR   320  2800   82          SSG 77  77          Pz III F-N HL120 TRM  272  2800               SSG 77  77          Stug. III B          HL230       700  3000  185   2100  AK 7-200 200         Panther, Tigers * TRR = Total reduction ratio - not listed here atm

NBB! The maximum torque of any gearbox implied by ZF's model numbering scheme may not be entirely accurate. It appears that ZF uprated the capacity of at least one or two gearboxes without changing the model number. Thus refs to an upgraded SSG 55 or wotevs FIND REF, FOOL! for certain tanks. The table above also shows that the G 45 and SSG 45 were fitted to a wide variety of engines from the NL38 TUK to the HL62 TR, which produced varying amounts of torque below and above 45 mkg. Yech.


 * Details of the above table:

In the following calculations I am trying to work out the maximum torque, given the stated max. power and revs. As a very general rule, max torque is developed at lower revs, perhaps 2/3 or less of max. revs. So taking 2/3 of max. revs, it is possible to make a rough calculation to find out the approximate max. torque developed by an engine.


 * The NL38 TUK Special in the Sd.Kfz. 6 BNL 8 developed 100 PS @3000 rpm, and 25 mkg of torque @1700 rpm. NB! This is considerably less the max torque of 45 mkg of the G 45 it was paired with.
 * To test my assumption that max torque is developed at 2/3 max revs:
 * Torque (mkg) = 716.19724 x power (PS) / speed (rpm). Forgetting that we know the actual torque figure for the moment, assume that max torque could be developed at 2000 rpm (approx. 2/3 of max power revs): so power at 2000 rpm might be approx. 65 PS. Torque would therefore be: 716.19724 x 65 / 2000 = 23.3 mkg - in fact, pretty close to the stated 25 mkg.
 * But knowing that max torque of 25 mkg is developed @1700 rpm: torque * speed / 716.19724 = power. So when the NL38 TUK is developing max torque, its power output is: 25 * 1700 / 716.19724 = 59.3 PS. That's a fair bit of low-down grunt. Again, not too far off my guess of 65 PS.
 * BUT!! The Panzer I Ausf A used the Krupp M305, 60 PS @2500 rpm, and the FG 35. With the best will in the world, I can't coax more than 20 mkg out of that, and why use a gearbox capable of 35 mkg? Likewise, the Panzer I Ausf. B used the same NL38 TU as just discussed, and the FG 31, which has a considerably lower max. torque figure than the FG 35, and certainly more than the G 45.
 * Thus why were gearboxes capable of 45 mkg (possibly more) used with engines from the NL38 (25 mkg) to the HL62 (45 mkg)? Quite a range. Thinking about this, it may be cheaper to fit an over-spec'ed gearbox rather than to design a new one specific to the engine. MinorProphet (talk) 16:04, 19 July 2024 (UTC)
 * According to Jentz & Doyle, the Maybach HL52 had a torque of 54 mkg - proposed for the La.S.100, light tank prototype for the Panzer II. (J&D, Pz. Tracts 2-1, p. 2-1-2). This means that the corresponding ZF gearbox should have a similar number, eg ZG 55 (which did exist, but was non-synchro). However, the next page (2-1-3) says that it used an SSG 45, which would have been well under-specced. BUT my table of Maybach engines has a note 'adjusted estimate' for the 115 PS for the HL52. When I first made the table, I tended to lower what seemed like a high figure - but what power was originally given? Production models of the Panzer II used the HL62 and SSG 46 (except Ausf. D & E) - only 1 mkg greater. Is this a slight fudge? There is not a chronological linear relationship between engine higher capacity and power, since later developments produced engines with similar capacities but much greater power and thus torque. Hmm.
 * Further hmm: Spielberger says that the SSG 45 was designed for the Maybach HL62 TR's max torque output of 45 mkp mkp/mkg. This figure is considerably less than of Jentz & Doyle's claim of 54 mkg of the lower capacity HL52 quoted above. There must be a mistake or error somewhere. I compiled the List of WWII Maybach engines without the benefit of either Jentz & Doyle or Spielberger - maybe time to have another look and add in known torque figures, even make a table from the above calculations...


 * ZF SSG 45, max torque 45 mkp in early Pz II + Maybach HL57 TR which gave 130 PS @2,600 rpm. With max. torque developed at lower revs, say 115 PS @ 1,900 rpm:
 * 716.2 x 115 / 1,900 = 43.35 mkg - fairly close. (J&D, Pz. Tracts 2-1, p. 2-1-8) states explicitly that the SSG 45 had a max torque of 45 mkg.


 * Sd.Kfz. 8 had an HL85 TUKRM, developing 185 PS @2,600 rpm. Suppose at a guess 135 PS @1,900 rpm.
 * 716.2 x 135 / 1,900 = 50.88 mkg; but since the Sd.KFz. 7 had a G 55, and the Sd.Kfz 9 had a G 65 (true) the Sd.Kfz 8 should have had something like a G 60. But such a thing doesn't seem to have existed.


 * Panzer III Ausf. A had a ZF SFG 75, designed to cope with the HL108's max torque output of 75 mkg @2000 rpm, which gave 250 PS @3,000. NB! Bollox alert!! More like 230 @ 2600 If max torque is developed at the stated 2,000 rpm, this might equate to 200 PS:
 * 716.2 x 200 PS / 2,000 = 71.6 mkg, also close, plus some manufacturer's margin for extra torque.
 * To work out the power developed, given the torque and speed:
 * torque (mkg) = 716.19724 x power (PS) / speed (rpm)
 * power = torque * speed / 716.19724
 * power = 75 * 2,000 / 716.19724 = 209.44 PS - pretty close to my estimated 200 PS.
 * But knowing that max torque of 75 mkg is developed @2000 rpm: torque * speed / 716.19724 = power
 * 75 * 2000 / 716.19724 = 209 PS

Forgetting that we know the actual torque figure for the moment, assume that max torque could be developed at 2000 rpm (approx. 2/3 of max power revs): = 2/3 of 2,600 = 1,730
 * HL108 TR 230 @ 2600 in Panzer IV Ausf A J&D say the HL108 developed 75 mkg @ 2,000 rpm. Which is not too bad compared to the manufacturer's figure of 79 mkg.(Koch, Motoren und Getriebe Deutsche Panzer 1935–1945 p. 24) See  below.

716.19724 x 160 PS / 2000 rpm = Please hold, found some actual figures... MinorProphet (talk) 21:32, 10 February 2024 (UTC)


 * HL120 TR in the Panzer III Ausf. D and Panzer IV Ausf. B developed 265 PS @ 2,600
 * Try them both backwards:
 * Since torque (mkg) = 716.19724 x power (PS) / speed (rpm),
 * Thus power = torque * speed / 716.19724
 * power


 * HL 230 developed 700 PS @3,000 rpm, but was governed to 2,500, making c650 PS, so perhaps might make 600 PS @2,100. (Dubious website figure for torque: 1,850 Nm = 1,365 lb.ft @2,100 rpm ) Actually, this is exactly the 185 mkp stated in Spielberger's Panther tank and variants, Appendix 2, p. 235.
 * 716.2 x 600 / 2,100 = 204.6 mkg - The gearbox on all Panther models was the ZF AK 7-200, which also matches up well.


 * HL295 (non-production, experimental engine) - Spielberger, Panther & variants, p. 175 gives actual graphs of power & torque: 850 PS @ 2500; almost flat torque curve, say 260 mkg @1750 rpm, which equates to 650 PS @1750 rpm (NB values taken from the graph)
 * 716.2 x 650 / 1,750 = 266 mkg - fairly close. But which gearbox? The relevant transmission would have been something like an AK 7-260 - haha! Plans of a French tank hunter, powered by the HL295, with a ZF AK 5-250! See also Plans for AMX 45 All suggested by this forum.

Actual figures for the HL108 and HL120
Hahaha! 10 February 2024 - finally! Koch, Waffen Arsenal 182 p. 24, for Panzer III Ausf. A-D

Torque figures for both HL108 and HL120 - 79 and 82 mkg!

Leistung. . . . . . . . . . . . 300 (320) PS bei 2800 U/min. Maximale Drehmoment. . . . . . .79 (82) mkg Bohrung und Hub. . . . . . . . .100 Ø x 115 (105 Ø x 115) Zylinderinhalt. . . . . . . . . 1080 (1190) Verdichtungsverhältnis. . . . . .1 : 7 Gewicht. . . . . . . . . . . . .920 kg Gehäuse. . . . . . . . . . . . .Grauguß mit auswechselbaren nassen Laufbüchsen Zylinderköpfe. . . . . . . . . .Grauguß abnehmbar Drehzahlbegrenzung. . . . . . . die Verwendung eines Drehzahlmessers mit besonders großen Zifferblatt wird empfohlen (wird von uns geliefert)

NB! last line (wird von uns geliefert) translates as "will be supplied by us," i.e. Maybach. This looks suspiciously like the manufacturer's own data sheet...! MinorProphet (talk) 21:32, 10 February 2024 (UTC) Apparently from their own manual (front page on p. 18 of Koch), quite possibly from c1936.

These high power and torque ratings are achieved by using 7:1 (Verdichtungsverhältnis) high-compression pistons and quite probably fuel with a decent octane rating, better than the later mandated OZ 74. Indeed, Spielberger Panzer III and variants, p. 140 says the HL108 TR in the Pz III Ausf. A had a compression ratio of 6.5:1 and developed a mere 230 - 250 PS: and the HL120 TRM in the Ausf. F (p. 145) developed 265~300 PS on a CR of only 6.2-6.5:1. This seems to be a very clear explanation of how power outputs were reduced after the change to OZ 74 (regular, in US terms).

Plus internal SSG 76 pics from semi-restored PzKpfw IV Ausf J found in Poland

Not quite ready for upload...
Hi, hope you are well. You were there at the start of Talk:Sd.Kfz. 8 (nearly two and a half years ago), which was the unlikely genesis of this draft article: I still haven't found out the gearbox model number of the 12-tonner. Apart from the very basic refs (currently generally in parentheses, most needing conversion to sfns - trivial if time-consuming, the bibliography section is already prepared), I'd like to think I'm fairly happy with this draft. NB Most of the talk page above this section details my slow attempts to work out the details of the article: much of the earlier stuff now seems vague and uninformed, although it was all enjoyable.

If you you could spare the time to go through my draft, I would very much welcome your critical comments, either general or very specific. I'm fairly sure you are very familiar with the RS literature. Although my understanding of German isn't too bad, you may be able to correct a few subtle points. I'm hoping that the tables at least are basically correct. I am hoping to publish the corresponding WW2 Maybach gearboxes draft article at the same time, which needs a bit more work... Neither of them are likely to be quite as popular as the List of WWII Maybach engines article (which I also started just for fun), but you never know... MinorProphet (talk) 18:38, 8 July 2023 (UTC)