Linke-Hofmann R.Ⅱbomber.
The R.II was a tremendous airplane called "a heavy bomber with four engines that simply expanded the shape of a high-performance single-seat fighter."
Both the wheels and the propeller simply expanded the shape of the small aircraft.
The only one propeller with a huge two-blade was driven by four engines.

R.II was an approximately three-times scale-up of a conventional single-engined biplane, powered by a quartet of Mercedes D.IVa inline-six engines turning a single 6.90 meter (22 ft 7.5 in) diameter tractor propeller, the largest single propeller ever used to propel any aircraft in aviation history.
The quartet of Mercedes powerplants were arranged in pairs in the central fuselage(same as R.Ⅰ) and drove the propeller through clutches, shafts and gearboxes.
The Linke-Hofmann R.II, probably the largest single propeller driven aircraft that will ever be built, had a wing span of 41.16 m (135 ft 0 in), length of 23.3 m (76 ft 5 in) and height of 7.1 m (23 ft 4 in).

Two examples of the R.II had been completed by the time of the Armistice. They bore the German military registration numbers R.55/17 and R.56/17.
Flight testing of R 55/17 was carried out after the Armistice in 1919. demonstrating acceptable performance and handling, being able to fly happily with only two engines driving the enormous propeller. Normal endurance was estimated to be 7 hours, but with adjustment of load and a cruising speed of 74 mph (119 km/h) it was estimated that the R.II could stay aloft for 30 hours.

There were plans to make it a 12-passenger airliner after the war, but the restrictions of the Versailles Treaty ended further development.

Radiator shape is unique.
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Hi!
Russian site says that

"The authors were puzzled by the boxy shape hanging from the racks under the fuselage, as shown in modern plans. Was it an early version of a retractable "garbage box" tower or an auxiliary fuel tank? A patent search proved that it was the first semi-retractable tower that allowed the gunner to be in it while the aircraft was in the air. There is no indication that the tower was installed on the prototype, most likely it was an improvement planned for later series."

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Hi! DFW R.Ⅰ.
DFW R-I
At the end of 1915, engineers from the Leipzig firm Deutsche Flugzugwerk (DFW) developed a heavy four-engine bomber under the factory designation T26. Since the spent scheme of such machines did not exist yet, each firm, which risked to undertake such a complex project, went its own way, acting by trial and error.

DFW designers decided to place all four engines of their aircraft inside the voluminous fuselage between the wings. Each engine worked on one propeller, being connected to it through conical gears and long shafts.

According to the designer's plan, such a scheme allowed to reduce frontal resistance and gave the opportunity to serve in flight very capricious and unreliable then motors. But the power losses in transmission mechanisms were very large, and a large mass of these devices over-weighted the machine.

However, on September 5, 1916, the T26 made a successful four-hour flight, proving that even a not-so-successful design could be viable if carefully crafted.


In the future, the aircraft demonstrated the ability to fly normally on three engines. It was put into service in October, but no new orders were made. The first flying giant of DFW remained in a single copy. The military assigned the car the R-I index (R - from the word Riesenflugzeuge, literally - "huge aircraft").

DFW R-I is a solid-wood three-toe biplane. The fuselage is lined with plywood, wings and plumage - canvas. Crew - 5 people: navigator-bombardier, aka nose shooter, two pilots, a mechanic-motorist and a tail shooter. Two pulling screws were located at the front edge of the upper wing, and two pushers - at the back edge of the bottom.

In the early spring of 1917, DFW R-I arrived on the Russian-German front, but soon, without making a single flight, was sent to the company to refine the transmission. At the beginning of the summer, it reappeared on the eastern front and on June 13 raided Riga from the Alt-Auz airfield, dropping 680 kg of bombs. During the second combat flight, two engines failed one by one. During the forced landing, DFW hit the wheels in the trench and fell to pieces.
Crew : at least 5, Length : 17.6 m, Wingspan : 30.5 m, Height : 6 m
Wing area : 186 m2,
Empty weight : 6,800 kg, Gross weight : 9,400 kg
Powerplant : 4 ×Mercedes D.Ⅳ8-cyl. water-cooled in-line piston engines, 164 kW (220 hp) each
Propellers : 4 x 2-bladed
Maximum speed : 120 km/h, Rate of climb : 1.7 m/s)
Wing loading: 51.7 kg/m2 (10.6 lb/sq ft)
Guns : Provision for dorsal, ventral and nose machine-gun positions
Bombs: up to 2,600kg of bombs

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Hi! DFW R.Ⅱ.

The DFW R.II is a German bomber during World War I. It was built by the German aircraft plant (Deutsch Flugzeug-Werke) and first flew in August 1918. Four engines were housed in the fuselage, driving two tractor-type propellers attached to the upper wing with a drive shaft and two pusher propellers attached to the lower wing. Six aircraft were ordered and two were completed by the end of the war, but they were never used for combat.
Developed in 1916, it was developed with a payload of 3400 kg, exceeding 2600kg of DFW R.I payload in the same engine and propeller configuration, which was produced only one aircraft. The engine was enhanced to 260hp from the R.I's 220hp Mercedes D.IV, four units, and the D.IVa with improved reliability was used. It was first flown in August 1918, but suffered from a problem with the vibration of the drive shaft. As a countermeasure, the drive shaft is surrounded by a steel pipe, and the support portion was strengthened. Six aircraft were ordered, and two aircraft were completed by the end of the war, but the operation on the front line was judged to be insufficient performance, and it was operated for training. After the war, plans were made to convert to 24-seat airliners, but the plan was canceled before the prototype was completed.
Crew 5,Length 20.93 m, Width 35.06 m, Wing area 266 m2
Height 6.40 m, Engine 4 x Mercedes D.IVa
Maximum speed 132 km/h
Cruising time 6 hours, Weight 8,600 kg, Total weight 12,000 kg


Bottom photo shows supercharged R.16/17. Brown-Boveri supercharger was driven by one 120hp Mercedes D.Ⅱ engine.
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Hi!
DFW R.Ⅱ and R.Ⅲ. Almost same scale.

The DFW R.III was a German bomber designed during World War I which had not built when the end of the war because of the cancellation.
The R.III was powered by eight engines. As with the previous R.Ⅰ/R.Ⅱ designs, these were to be housed inside the fuselage, driving propellers by long driveshafts.
In the R.III design, these propellers were to be mounted on a nacelle in the interplane gap. Each end of this nacelle would carry two co-axial propellers, each driven by a separate engine.
Had it been built, the R.III would have been the largest aircraft in the world at the time.
Length : 25.00 m, Wingspan : 53.50 m, Height : 8.78 m
Powerplant : 8 × Mercedes D.Ⅳa, 260 hp each
8 × machine guns, 2,500 kg of bombs

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Of course I have. It's a excellent book!! I got this second hand book in Kanda Tokyo.(Thied Edition,1988,PUTNAM, ISBN 0 85177 812 7)
But very expensive now. For example, $178.:oops: I hope same books for British, French, Italian and Russian giant aircraft.
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Hi! AEG R.Ⅰ.This plane is like a flying sperm whale.:D
A.E.G. R.I
Two "Giant" machines were ordered from A.E.G. during 1916, R I 21/16 and R. I 22/16. The four engines were placed together inside the fuselage, the airscrews being driven through gear boxes and transmission shafts. Initially, four-bladed airscrews were fitted, but later a two-blade type was substituted. First flights of the R I 21/16 took place during 1916 and were considered to be satisfactory. Later, during flight trials on 3rd September, a propeller disintegrated due to the laminating glue not having been allowed sufficient time to harden thoroughly. As a consequence the transmission shaft tore loose and smashed a centre-section strut, which caused the machine to crash with a loss of seven lives. R I 22/16 was still incomplete at the end of the war and was eventually scrapped. Engines, four 260 h.p. Mercedes D IVa driving two airscrews through transmission geared down to 750 r.p.m. Span, 36.0 m. (118 ft. 1 1/2 in.). Length, 19.5 m. (63 ft. 11 1/2 in.). Weights: Empty, 9,000 kg. (19,845 lb.). Loaded, 12,500 kg. (28,003 lb.).
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Thanks for excellent information.
No doubt it's better to have a hard copy of this amazing book.
 
Hi! Schutte-Lanz R.Ⅰ.
In the middle of 1917 the "Amerikaprogramm" came into being, and its execution became the responsibility of Idflieg. The programme's sole purpose was to strengthen the German air arm to meet the expected impact of American participation in the war. Although emphasis lay in the establishment of new fighter squadrons, the complement of the two R-plane squadrons was also to be increased. The net effect on Schutte-Lanz was that it, among other aircraft companies, received a contract to construct two all-duraluminium R-planes, designated the Schul R.I, numbered R.65 and R.66.

Experience with previous central-engined R-planes had shown that large fuselages were not stiff enough to avoid resonance vibrations, bending and twisting.
The same could be aid of wing-strut or outrigger mounted propeller supports: they had proved to be too flexible to assure fully reliable operation of the drive system.
To avoid these problems,Schutte-Lanz designed twin-boom biplane with a centre nacelle.
Relatively short and small centre nacelle only containing the pilots' cabin, navigator and wireless operator's positions, engines(six 300 h.p. Basse und Selve BuS.IVa engines) and bombs. Initially two superchargers driven off the centre gear-boxes were to have been supplied, but these were eliminated in the final version.
Short and small centre nacelle had high eigenvalue frequency to avoid resonance vibration. also afforded good manoeuvrability.
Centre nacelle did not receive tail stabilizer/rudder/elevator force, then increase bending and twisting strength.
Two outer booms to support the tractor propellers, the tail and the fuel tanks, which were separated from the engine to minimize fire hazard. In an emergency the fuel tanks could be jettisoned, and a gravity tank located in the top wing contained enough reserve fuel to enable the R.I to find a suitable landing spot.
The twin booms supported the biplane tail, which, being held at the end of its span, could be made structurally lighter.
In contrast to the all-steel wing spars employed by Dornier and Junkers, the Schutte-Lanz R.I was the only R-plane to have duraluminium wing spars planned for it.
According to Dipl.-Ing. Hillmann, the R.I was 80 per cent complete when the war ended. It was dismantled to prevent it from falling into Allied hands.

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Excellent description is here.
 
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Hi!
The Adlershof Projects
”Ten project drawings of R-planes were discovered among a pile of Zeppelin material that had found its way to the Air Museum at Wright Field. Even by today's standards, the size of some of the projected aircraft is immense, these drawings, more than anything else, reflect the thinking of German aeronautical engineers at the time. Unfortunately no information has been found to throw further light on these extremely interesting drawings. Six of the aircraft depicted follow the same twin fuselage configuration, differing in size and horsepower, and these show a strong resemblance to projected designs published by Junkers in the early 1920s. But the only concrete fact, apart from their existence, is that they originated from Adlershof.”

1. Adlershof R-plane project larger image.
 4/500 h.p. Benz engine. Span : 48.4m, Length : 26m, I can't see radiators. 10×300kg bomb under the wing?
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2. Adlershof R-plane project, dated 7 July 1918. 10/500 h.p. engine. Span : 67m, Length : 37m.
The nose propeller is driven by two engines. The diameter of the nose propeller is about 1.5 times the diameter of the other eight propellers. The propellers at both ends of the engine pod in the side view are omitted. In the front view, I can see radiators.
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these drawings, more than anything else, reflect the thinking of German aeronautical engineers at the time.
Which is that the most important is to slaughter the other side's civilians.
Visibly, they are the fathers of those who waged WWII onto Europe so mercilessly....
 
"Der Ingenieur ist der Steigbügelhalter des Kapitalismus"
(The engineer is the one, who brings the capitalism to power)

That was a slogan, which was still painted on a wall of the university, I was
attending during the early `80s and it was there since the late`60s/ early `70s.
It wasn't really left there, instead of being removed at once, because of it's
political statement, but to remind us to the responsibility of those, working in
a purely technical field. At least, we were told so, perhaps the real reason was
just, that money for renovation was scarce ...But the first explanation sounded
better, too, I think. ;)

So, in a way, you're right, I think. But, first, I cannot fully agree to labelling those
engineers as the cause for fascist Germany starting WWII and doing even worse,
as I wouldn't blame Boeing engineers for planning nuclear wars, because
they were the first to build the appropriate means of transportation for "the bomb".
And secondly, we are discussing aircraft as part of technology here, often a deadly
technology, but the ways and reasons for it to be used in anger, very rarely depend
on those, who designed it, I think, because those are politics and so, out of the scope of
this forum and so the place to discuss them isn't here, please !
 
Hi!
3. Adlershof R-plane project. 4/500 h.p. Benz. Span : 59m, Length : 30.8m, 6 machine guns. Many bombs installed vertically in the wing outside of the engine?
  It seems that there is no blind spot in the defense weapon of this plane.
  I can see some parts at the wing root. What is this? Radiator? Fuel tank? I can't see pilot seat.

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I cannot fully agree to labelling those engineers as the cause for fascist Germany starting WWII and doing even worse
Not to re-start that discussion, just to clear a misinterpretation: I never meant those engineers were a "cause", but an early indicator of a trend.
(the trend for the goal of war switch from defeating the other side's army to eliminating its population).
 
Ah, ok ! Then perhaps we can put it into more technical terms, and say, that those aircraft clearly
marked the change from a tactical to a strategical use of a bomber force ? That use, aircraft designers
in several countries built big aircraft with long range and large bomb loads for ?
If and why those aircraft are targeted then by high ranking militaries and politicians against military installations,
like fortifications or military harbours, or against pure population centers is interesting and important, but
not in the context here.
 
Sorry I can't attend such a difficult discussion.:)
 
Hi!
4. Adlershof R-plane project. 6/500 h.p. Benz. Span 72m, Length 38m.
Main wing is monoplane and horizontal tail stabilizer is biplane.
I can imagine pilot position. No bomb in this drawing. Propeller size which located wing leading edge is different from which located wing trailing edge.
Each front propeller was driven by two engines. In this drawing, I can see three turrets.
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What were the competeing views on tricycle undercarriage vs tail wheel undercarriage at this time?
 
These weren't true tricycle undercarriages, the nosewheel was there, purely to prevent nose-overs on landing. Remember, landing an aircraft of this type and size wasn't easy at the best of times, and most of these were, or were planned to be, operating at night, which adds a whole new level of complication and uncertaincy. Compare with the big nose skid on a Vickers Vimy . . .

cheers,
Robin.
 
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The last r-class aircraft was the four-engine R-XVI. This machine, built by aviation company, outwardly almost did not differ from the R-VI. The novelty was in the power plant. In addition to the two conventional engines of the "Benz" Bz.IV of 220 hp, its gondolas had two of the newest experimental engines , the "Benz" Bz.VI 530 hp. But in one of the test flights the aircraft crashed, and the second copy was finished only in 1919 and for some time used as a passenger aircraft.
After the war, German heavy bombers were used for some time for postal and passenger transport. It is known that at least one of the "Tseppelins" in 1919 flew to the city of Kamenets-Podolsk to communicate with the leadership of the Ukrainian People's Republic. All were then destroyed at the request of the victorious countries.

I can see larger propeller at the wing trailing edge.
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"Der Ingenieur ist der Steigbügelhalter des Kapitalismus"
(The engineer is the one, who brings the capitalism to power)

That was a slogan ... to remind us to the responsibility of those, working in
a purely technical field. ... But, first, I cannot fully agree to labelling those
engineers as the cause for fascist Germany starting WWII and doing even worse,
as I wouldn't blame Boeing engineers for planning nuclear wars[/I]

I agree up to a point, both with the sentiment and the remark on scope of discussion. But, only to a point. Historically, the capabilities that engineering provides as often as not drive the ways in which it is used and, thereafter, developed. Sven Lindqvist makes this point in his idiosyncratic but thought-provoking "A History of Bombing."
 
I believe Jens-san will give us more valuable information because he can read Germany.;)
 
Well, let's see, where to start with ...
I know those drawing from "The German Giants" by G.W. Haddow and Peter M.Grosz, Putnam publishing, 1962, where it is
mentioned, that they were "discovered among a pile of Zeppelin material that had found its way to the Air Museum at Wright Field",
but that "the only concrete fact. apart from their existence, is that they originated from Adlershof".

So, first, "Adlershof" is used in some publications as a kind of company's name like "Gotha" or "AEG", but in fact, it isn't. Until 1920, when it was
suburbanised, Adlershof was a village nearby Berlin, adjacent to Johannisthal, where the first airfield in Germany was founded in 1909.
That airfield attracted several constructors and companies to settle there, e.g. August Euler, Edmund Rumpler, Anthony Fokker, Albatros or the
Wright Brothers. That cluster of aviation companies laid the foundation for a centralised research facility, The "Deutsche Versuchsanstalt für Luftfahrt“
(DVL). The outbreak of WWI not only lead to a quantum leap in the production of aircraft at this location, but (after a break) to the expansion of
the facilities of the DVL, too, which from 1915 onwards was amalgameted with the "Flugzeugmeisterei des Heeres" (Aircraft Establishment of the Army).
directing not only selection of new types and production, but also all kinds of aeronautical research, that was done there for all companies.

As mentioned in the Putnam volume, six of those drawings show details, well known from later Junkers designs, like very thick self-supporting wings,
monoplanes with closed cabins and even the kind and shape of the ailerons. But several of those characteristics can be found in the E.4/20, too, which
actually was designed by Karl Rohrbach.
Unfortunately, the inscriptions on those drawings don't give away the designer, only the basic data like dimensions, weight, crew and motor capacity.
And at least the data for span of the last designs are impressive, even today, though I'm sceptical, if a cantilever wing of 114, or even 140m would
have been really technically feasible at the end of WWI.
As mentioned in this thread before, and by the authors of "The German Giants", too, there was a tendency towards "bigger is better" during that
time, maybe partially triggered by the fact, that many more R-Flugzeuge were lost due to accidents, than being lost to enemy defences, besides
the increases in range and bombload.
My personal opinion is, that this may have led to a feeling of "invulnerability" of such big aircraft, and so paved the way for bigger and bigger
designs. But this over-confidence may not have lasted too long, if the use of those aircraft would have lasted longer. In "The Air Defence Of Britain,
1914 -1918" by Christopher Cole and E.F. Cheesman, Putnam publishing, too, it is mentioned, that investigations on the futile attacks on German
R-Flugzeuge by fighters, came to the result, that in most cases the pilots, still unfamliar with the sheer size of their targets, had opened fire far too
early, from distances more than twice the effective range. So it would have been just a matter of time, before the real efficiency of the bomber
defences would have to be proven.
Maybe those fascinating drawing were less meant as actual projects, but more as an illustration, where an increase in the design points bomb load
and/or range would lead to ? Such representation were common in the design of warships, e.g. the German H-class battlehips, where the H-44 was never
meant as a real project. Aircraft of that size probably wouldn't have been accommodated on a standard airfield back then, but needed more
and bigger infrastructure, maybe often leading to them being stationed further away from the target area, so eating up part ot their range, maybe
leading to further increase in weight and size.

But we still can hope, that one day, another pile of papers will surface, answering at least some questions !
And as mentioned in "Zeppelins Flieger", published by the Zeppelin Museum Friedrichshafen, there are still documents owned by Zeppelins family,
but still not made public, so maybe one day .... ;)
 
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Friedrichshafen Aircraft of WWI,

a G.V bomber.
 

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From, German Aircraft of Minor Manufacturers in WWI Vol.2,

a Schutte-Lanz Projects.
 

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