Panther with a radial engine

[Pasoleati]

According to Spielberger, the Panther was tested with a BMW 132 radial engine. Tests were promising, but the book has no details. Anyone with further information?

 

[Apophenia]

Not sure if this is a useful lead but, according to A Life Awheel: The ‘auto’ biography of W de Forte by Richard Skelton, one of the engineers behind the BMW 132D-powered Panther was Alex von Falkenhausen.

 

[Harry64]

Because of the inaccessibility of the lower cylinders, the experiments were discontinued. The stated continuous output of the motor of approx. 520 HP in addition to the 600 HP of the Maybach still appeared to be of little benefit.
Source: Panther - Meilenstein der Geschichte - F. Koehler

 

[riggerrob]

BMW 132 was almost "square" with a length of 1.411 meters (55.55 inches) and a diameter of 1.38 meters (54.33 inches). Mind you that includes the length of the propeller speed reduction unit, which would need to be changed for installation in an AFV. That large diameter would limit hull height. Does anyone have dimensions for a stock Panther engine compartment?

A hypothetical alternate installation would lay the engine nose-down (vertical crankshaft). Hopefully the new psru would reduce hull height enough to avoid a major redesign.

In comparison, engine diameter (45 inches/1.143 meters on Wright/Continental R-975 Whirlwind) as half the reason that the American M3 Lee/Grant and M4 Sherman series had such deep hulls. The other reason was a drive shaft that was suspended half the engine diameter above the hull floor.

 

[Pasoleati]

Riggerrob, the deep/high hulls of the M3/M4 was not caused by the "diameter" of the radial engine. It caused by the idiotic decision to use a powershaft mounted directly on the engine's nose case. The M18 had the same engine, but it used a gearing so that the power transfer shaft could run horizontally along the floor of the vehicle. A look at respective cutaway drawings easily reveal that. Had the M4 used the M18 setup, the tank would have been substantially lower and lighter (smaller hull=less weight).

The reasoning that the "inaccessibility of lower cylinders" was in practice of any significance is dubious; it defitinely wasn't in the M3/M4/M18. What is more, a BMW 132 rated at 520 or so hp in a tank installation means an engine running much below its capability, thus giving reliable and durable operation (in aircraft the same engine was used with powers exceeding 1000 hp and basically always operated at above 520 hp).

What is more, the Maybach suffered from serious issues like coolant leaks plus had to be considerably derated to keep its life reasonable. In Finnish Air Force maintenance experiences in WW2, air-cooled radials required far less daily maintenance than their liquid-cooled companions.

Honestly speaking, although fine engines in theory, Maybach's WW2 tank engines were in practice quite poor with highish specific fuel consumption, poor torque characteristics and lack of ruggedness (Finnish tank drivers driving the Stug III were warned that its engine does not tolerate rough handling like the previous tank engines (T-26/Vickers) they had operated). A bad feature for a wartime engine.

 

[Foo Fighter]

Difficult to say when and where the Maybach engines were unreliable due to the practice of using forced labour in construction. Where the engines badly designed or were the 'other' factors contributing more in this? I'm pretty sure they designers knew their onion. Perhaps our resident engine guru's can run a basic theorem together to rationalise all the different impacting elements, fuel standards and spares availability for example.

 

[riggerrob]

Difficult to say when and where the Maybach engines were unreliable due to the practice of using forced labour in construction. Where the engines badly designed or were the 'other' factors contributing more in this? I'm pretty sure they designers knew their onion. Perhaps our resident engine guru's can run a basic theorem together to rationalise all the different impacting elements, fuel standards and spares availability for example.

Also consider that the German war industry was hampered by shortages of key alloying metals like nickel.

 

[Herman]

The BMW radial was not too high and it fitted inside the (small) engine compartment of the Panther. The drive shaft had to pass under the turret basket, so, the engine was fitted with a drop down gearbox that lowered the driveshaft to the same height as the shaft from the standard Maybach HL 230 engine. Allied tanks fitted with radial engines all had engine access hatches in the rear buklhead of the engine room. Through these, the lower cylinders were accessible. The Panther's does not feature an access hatch. The engine literally had to be removed from the tank to change the spark plugs. To allow the radial to be used operationally, the tank would have had to be substantially modified to allow improved access to the engine.

As far as power is concerned, we should remember that the max. rpm of the HL 230 engine was limited to 2500 rpm and the compression ratio lowered from 6.8:1 to 6.4:1, soon after it was introduced, as a result of poor reliability and durability if the engines were allowed to be used at their design max. rpm of 3000. At 2500 rpm, the Maybach HL 230 only developed around 575 metric horsepower, i.e. only about 50 more than the big BMW radial. Furthermore, high torque is more important to a tank than high horsepower, and the 27 litre BMW engine had oodles of torque. The radial normally developed about 800 hp at 2350 rpm in aircraft use, running on aviation gasoline. For use in the Panther, the supercharger was removed and the compression reduced to allow the engine to run on 74 octane German army petrol. In the end, further development of the project was stopped because German industry could not produce enough of the radials to satisfy the demands of the air force, never mind producing hundreds or thousands of extra engines for tanks!

 

[tomo pauk]

@Herman - is there some article or a book where that engine installation is discussed?

 

[Herman]

@Herman - is there some article or a book where that engine installation is discussed?

Spielberger W.J.: Panther & Its Variants. Schiffer Publishing, 1993. ISBN: 978-0-88740-397-2. p.p. 141-143.

 

[Herman]

@Herman - is there some article or a book where that engine installation is discussed?

I know this sounds arrogant, but I actually wrote a book on German Fighting Vehicle Engines of the Second World War. I did submit it to the Osprey publishing company but they thought, correctly in my view, that the subject is too specialised to be economically viable in a conventionally printed book. Below is the section that deals with the subject at hand, i.e. the use of a radial engine in the Panther.

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As mentioned previously, MAN did, experimentally, install radial engines in two Panther tanks in late 1943. The engine used was the BMW 132 Dc, a 9-cylinder radial of 27.7 litres (1690 c.i.). The BMW 132 engine was descended from the Pratt & Whitney Hornet, for which BMW acquired a production licence in 1928. Like the American R975, the engine was fitted with a cooling fan for tank use. In addition, a drop-down gearbox was fitted. The standard drive shaft between the engine and gearbox in the Panther was too low to attach directly to the crankshaft of the radial engine. The drop down box corrected this.

For tank fitment, the engine was carburetted and normally aspirated while most of the aircraft versions were fitted with direct fuel injection and supercharging. The tank version developed 520 hp at 2000 rpm. The aircraft versions of the this engine developed 720 hp to over 1000 hp. The low power in the tank installation is due to the lack supercharging and fuel injection, and adaptation of the engine to run on 74 octane army petrol.

Tests with this setup were apparently satisfactory and MAN suggested building 20 more Panthers with this engine for extended trials. One must keep in mind that at this time, the big Maybach engines were proving to be very unreliable and MAN was keen to find a potentially more reliable alternative for the Panther. In the end, this did not proceed however as it became clear that the lower cylinders, including valves and spark plugs, were not accessible for servicing in the narrow confines of the Panther’s engine compartment. To access these important and maintenance sensitive components, the engine had to be removed from the tank! The other problem was that Germany could barely produce enough of these engines for their aircraft. The BMW 132s was mainly used to power the Junkers Ju 52 transport aircraft(4).

It is interesting to speculate what might have been in this regard. Germany actually produced two suitable air-cooled radial engines in the power range to suit the Panther: the BMW 132 of 27,7 litres (1690 cu. inch) and the BMW Bramo 323, also a nine cylinder radial, that displaced 26,8 litres (1637 cu. inch). In aircraft use, with superchargers, these engines produced up to about 1200 hp. With some development work, one could probably expect them to achieve around 550-600 in the tank role, certainly if the supercharger was retained, as in the case of R-975 engine(5).

Because of the design of a radial engine, with lots of important bits at the bottom, they are only really suitable for tanks with the engine at the back and the transmission at the front, so that the engine can be approached from the rear for maintenance. This lay-out is found in the Sherman and Honey tanks, for instance, but also in WW2 German tanks, like the Panther and the Tigers. To fit a radial, the rear of the Panther’s hull would have had to be redesigned to allow for engine hatches but this should not have created any great problems. The BMW 132 radial, which had been produced in Germany from 1933, would likely have been more reliable than the problem-ridden Maybach HL 230, especially during the initial deployment of the tank. One should keep in mind though that the R-975 was the least reliable of all the engines used in the Sherman, during WW2; even less reliable than the Chrysler multibank engine, and much less reliable than the Ford GAA V8 unit.

Aside from technical considerations, there are several issues which would have had to be solved in this hypothetical situation. Production capacity would have had to be found to produce the required number of engines. Maybach alone produced more than 8000 HL 210/230 engines during the war while a number of other manufacturers also produced significant numbers of these engines. Auto-Union, for instance, was producing about 800 engines per month by mid-1944(5).

In the intrigue-ridden Nazi Germany of the forties, loyalties and favouritism played important roles and Prof. Maybach, a personal friend of Hitler, would have been piqued, to say the least, if a BMW aircraft engine had been selected for the new tank instead of a Maybach unit. Finally, the big radial produced about 15-20% more torque than the HL 230 engine. The drive train (gearbox, differentials, steering gear and final drives) would likely have had to be adapted to the bigger engine. If not, especially the fragile final drives of the Panther would likely have been even more unreliable with this engine than with the Maybach V-12.

References:
R-975 2: The Sherman Tank Site.
Hoffschmidt E.J. and Tantum W.H. Tank Data 2. Aberdeen Proving Ground Series. WE inc. Old Greenwich Conn. 1969. pp. 48-60.
Spielberger W.J. Panther & Its Variants. Schiffer Publishing, 1993. ISBN: 978-0-88740-397-2. pp 141-143
Jane’s Fighting Aircraft of World War II. Jane’s Information Group. ISBN 1-851-70493-0. pp 288-289.

 

[Foo Fighter]

I have oftern wondered whether the radial engine and electric motors would have been a good fit for the Panther.
Chuck out a lot of the drivetrain complexities and perhaps a workable if imperfect solution may be found.

 

[Herman]

I have oftern wondered whether the radial engine and electric motors would have been a good fit for the Panther.
Chuck out a lot of the drivetrain complexities and perhaps a workable if imperfect solution may be found.

Electric drive has theoretical advantages for the propulsion of large, heavy vehicles and more countries have experimented with its use in tanks. Porsche did a lot of work on this concept during WW2, with the development of the Porsche version of the Tiger I, and the later Elephant self-propelled anti-tank gun. The US also did quite a bit of research and development of electric drive for tanks. During the development of what was to become the T26 and finally the M26 Pershing tank, the T23 tank was built. This was powered by a Ford GAN engine which drove a generator which in turn powered an electric traction motor at each final drive. Such an electric drive provides immense torque at low speed, and the speed of the respective motors can be varied infinitely, so that an infinite gear range and steering radii are possible, without the use of complex, mechanical steering gear. Total production of the T23 tank was 250 vehicles. No tank manufacturer has however gone for a production vehicle with petrol/diesel electric drive.

 

[tomo pauk]

I know this sounds arrogant, but I actually wrote a book on German Fighting Vehicle Engines of the Second World War. I did submit it to the Osprey publishing company but they thought, correctly in my view, that the subject is too specialised to be economically viable in a conventionally printed book. Below is the section that deals with the subject at hand, i.e. the use of a radial engine in the Panther.

That you for the overview.
Perhaps small printing houses might be of help? For example, currently the best, 1000 pg big book about the Bf 109 is being printed in small quantities (link).

 

[Elan Vital]

Interwar-1940 France studied the question of electric transmissions extensively as this was often the most practical system for very heavy vehicles at a time when mechanical systems were not scaled up/strengthened enough. It does add a lot of weight and (sometimes) bulk however, even when it works perfectly. They were working on using it only for vehicles above 45 tonnes while upscaling mechanical systems to that weight.

In the case of the Panther, the final drives were the truly weak part with the transmission itself being reasonable. But in this case it was more practical to improve the mechanical systems rather than get down the rabbit hole of electric systems.

 

[Foo Fighter]

The Panther would have been too small for the drivetrain of thePanzerjäger Tiger (P) 8.8 cm PaK 43/2 L/71 ‘Ferdinand/Elefant’ (Sd.Kfz.184) and the GT-101a only appeared in a few test vehicles.

That is not a tank either, unless you are a bleep bleep cee reporter anyway but they had their success and fans in the Ost front due to their heat generation.

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