Introduction Maybach used a series of letter codes and numbers to identify specific engine models, namely: • NL / HL – performance • TU / TR – lubrication • K – clutch • R / RR – V-belt drive for compressor and/or radiator fans • M – "
schnapper"-type magneto ignition Although these codes usually indicate what ancillary equipment was fitted at the factory (e.g. the HL42 TUKRRM and the HL57 TR), there are some exceptions, discussed below. The individual engine number and its capacity, the model type, and year of manufacture are hand-stamped on each crankcase. On 6-cylinder models with
schnapper magneto ignition, this information is found on the magneto housing: e.g. MOTOR Nr 730192 4198 ccM. HL42 TUKRM 1943 And on the HL210, stamped at the top end of the crankcase above the flywheel cover: Mot. Nr. 46302 HL210P45
Performance • NL =
Normalleistung (normal performance motor) • HL =
Hochleistung (high performance motor) This is followed (without space) by the approximate engine capacity (e.g. HL42 = approx. 4.2 litres.) Compared to the NL motors, the HL (high performance) series had a higher
compression ratio, which increased the power output. This advantage was somewhat lost when a mandatory requirement to run on lower-quality OZ 74 (74
octane) gasoline after October 1938 necessitated the compression ratio of the HL series to be lowered, achieved by fitting shorter pistons and a new
cylinder head. This may partially explain the similar power outputs of engines with different capacities, shown in the table further below.
Lubrication • TR =
Trockensumpfschmierung (
dry sump lubrication), generally fitted to tanks - because of low ground clearance - and to the
Sd.Kfz. 10 and
250 half-tracks. There is no
sump below the crankcase: the engine oil is contained in a reservoir on one side. On later V-12s there is a tunnel through the oil reservoir, through which the hand crank for the
inertia starter passes, operated from the outside rear of the vehicle. The
Sd.Kfz. 10 had a unique arrangement with a conventional clutch attached to the engine driving a
pre-selector Maybach 'Variorex' VG 102 128H gearbox. (
See also diagram on right.) • Other tank gearboxes included the synchromesh ZF Aphon SSG 5x and 7x series gearboxes (the SSG 75 fitted in early
Panzer IV had five forward gears and one reverse: the 76 and 77 had six forward and one reverse). The main clutch () (LA 120 HD) was bolted to the gearbox on the SSG 75, and incorporated into the main housing in the 77. The SSG 77 gearbox replaced the mechanically vulnerable Variorex in the Stug. III Ausf. C. Bigger tank engines (e.g. the
HL230 fitted to
Tiger Is
and IIs) used a hydraulically controlled Maybach-Olvar gearbox such as the Olvar OG 40 12 16 (8 forward gears, 4 reverse), or the ZF AK 7-200 with synchro used in the
Panther. • Some half-track gearboxes also included a
power take-off shaft (PTO) driving an external
winch ().
Compressor • R =
Riemenantrieb für Luftpresser (
V-belt drive for
air compressor), driven at the radiator end by a pulley with an extra groove. Most of the half-track engines had a compressor fitted, to power various types of equipment (discussed below). On some engines (e.g. the NL38 TUK) the compressor was an integral part of the engine, driven by internal gears and mounted on top of the cam cover at the flywheel end. The compressor is not specifically indicated in the model number. In similar fashion, on the HL 57 TU and 62 TUK the compressor was located in a gear-driven housing next to the clutch on the inlet side. On other models, the compressor was an external belt-driven ancillary denoted by an (R) in the model number (e.g. HL38 TUKR), it was mounted on one or other side of the engine, driven by an extra V-belt at the radiator end. Thus the lack of an (R) in the model number doesn't necessarily mean that a compressor wasn't fitted. The compressor was used to power various types of equipment, including: :*Sd.Kfz. 10 and 250 – Variorex VG 10 2 128H pre-selector gearbox :*Sd.Kfz. 11 and 251 – air brakes on towed equipment (e.g.
Pak 40 anti-tank gun) :*Sd.Kfz. 6–9 – pneumatic foot/parking brake + towed equipment (e.g.
15 cm sIG 33 towed by the Sd.Kfz 7) :*Panzer III Ausf. E–G, and Stug III Ausf. A (only 20 made)§ – Maybach Variorex SRG 32 8 145 pre-selector gearbox ::On certain Panzer IIIs, and Stug III, and on the
Sd.Kfz. 10 with its derivative the
Sd.Kfz. 250, the compressor provided the (reverse) pressure for a pneumatically operated pre-selector gearbox. The air inlet of the compressor is connected to the system, not the outlet: the compressor works "in reverse" to create a vacuum. To shift gears, the pre-selector lever is set in the desired position or slot, and when the next gear is needed, the clutch pedal is depressed for about one second. This opens a valve inside the Variorex gearbox, which operates specific vacuum-actuated pistons attached to selector forks: these move
dog clutches, which select the desired gearing.Although they worked on the same vacuum principle as the bigger tank pre-selector gearboxes (e.g. Variorex SRG 32 8 145, installed in
Panzer III Ausf. E-G), these gearbox types had no integral clutch, and were much smaller than those fitted to tanks. The drive passed through a standard clutch attached to the engine via a cardan shaft into the gearbox: depressing and releasing the clutch pedal simultaneously disengaged the main clutch and actuated the vacuum pistons to engage the pre-selected gear ratio. • KRR = Clutch, compressor, and extra belt drives for radiator fans: fitted to a number of
Sd.Kfz. 251 variants, which had a different radiator from the unarmored
Sd.Kfz. 11 on which it was based.
Ignition All Maybach engines used a
Bosch 12-volt
magneto for the ignition. There were two main types: • Driven off the camshaft () (or the camshaft pinion), located at the top of the engine at the flywheel end. This type of magneto can often be identified at the top of the engine at the flywheel end by a circular, slightly domed cover, and a tubular duct (sometimes corrugated) which fed the ignition leads out of sight behind an engine cover plate. This type of installation () was part of the standard specification and not included in the model letters (e.g.HL98 TUK). This applies to some 6-cylinder models and some V-12s. On the HL210 the magnetos are separately located above the ends of the camshafts, and on the HL230 they are centrally installed between the cylinder heads. • M = (impulse magneto ignition). Some 6-cylinder models had this type of magneto in its own housing on the right-hand side, and driven off the starter ring on the flywheel. In V-12s, the magneto is located in the V of the cylinder block, driven off the camshaft pinion. Most models were also fitted with a belt-driven
Bosch generator for charging the two 12-volt batteries for the 24-volt electric starter motor; and for 12-volt lighting, etc. On 4- and 6-cylinder engines the generator was usually connected by a short drive shaft to the separate belt-driven coolant pump, located close to the cylindrical
oil cooler.
Installation • P =
Panzerkampfwageneinbau (tank installation?) • Z =
Zerstörereinbau (tank destroyer installation?) • S =
Schleppereinbau (military tractor installation?) These letters were only used on some models, e.g. HL42 TRKMS, HL45 Z, HL157 P. The HL230 P30 and P45 appear to fall into this category, being named according to their original project specification: the HL230 P30 was designed to be fitted in the
Panther, whose prototype was the 30-ton class VK30.02; and the HL230 P45 went in the Tiger, whose final 45-ton class prototype was numbered VK45.01.
Examples • NL38 TRKM = Normal performance 3.8 litre, dry sump, clutch,
schnapper magneto (Panzer I Ausf. B) • HL42 TUKRRM = High performance 4.2 litres, wet sump, clutch, belt-driven compressor, twin radiator fans,
schnapper magneto (Sd.Kfz. 251) • HL62 TR = High performance 6.2 litre, dry sump, no clutch (K), no external compressor (R), camshaft-driven magneto (no M) (some Panzer II) • HL108 TUKRM = High performance 10.8 litre, wet sump, clutch, belt-driven compressor,
schnapper magneto (Sd.Kfz. 9) • HL120 TRM = High performance 12.0 litre, dry sump, no clutch (K),
schnapper magneto (Panzer III) ==Gallery==