Effects of a mass produced Do26?

[wiking85]

Now what the Do 26 could do that Bv 138 couln't? 138 was chosen to be the main flying boat type, not a good idea to change the main type if there wasn't something concrete to gain.

Juha

Fly that far. The BV138 had much shorter legs.
Blohm Voss BV 138
It had less range on max fuel than the Do26 had on normal fuel loads with full military kit. There's nothing to say there can't be both produced simultaneously, as the BV138 had good uses at short to medium ranges.

 

[wiking85]

View attachment 230269

It sounds like the primary argument is for diesel engines due to increased fuel efficiency. So why not put tandem diesel engines on Do-217 airframe ILO DB603 V12 or BMW801 radial engine? Tandem engine pod should fit on Do-217 wing without too much difficulty. That gives you fuel sipping diesel engines on a relatively advanced bomber airframe.

Can't use radials for tandam layout; the rear ones couldn't enough airflow enough to cool down. Plus the BMW 801 is a very long engine, so would require totally new wings.

The Do217 was also not ready until late 1940-early 1941 historically after starting design in 1937 or 1938. It was meant as a specialty naval strike aircraft not a long range recon craft in the way the Do26 or FW200 were. So even with underpowered diesels, we are looking at a much later start date than the Do26, which was ready to go into production in 1939; by 1941 its too late, so the Do26 is better than anything else out there hypothetical or not.

 

[Shortround6]

Sticking a pair of 1400lb engines plus 300-400lb propellers several feet BEHIND the Cg may not be the best thing for the flying qualities of the Do-17, especially after you yank the over 2000lb BMW 801 form in front and replace them with 1400 engines.

Airplanes are not Lego toys. Some combinations work a whole lot better than others and just because something "looks like it would FIT" doesn't mean the plane would actually be safe to fly with such a combination.

Of course changing the Do 217 over to nose wheel landing gear shouldn't be a big problem either to get clearance for the rear propellers unless you stay a tail dragger and use really tiny 5-6 blade props on the rear engines

 

[Juha]

Fly that far. The BV138 had much shorter legs.
Blohm Voss BV 138
It had less range on max fuel than the Do26 had on normal fuel loads with full military kit. There's nothing to say there can't be both produced simultaneously, as the BV138 had good uses at short to medium ranges.

Just look the reat defences, Do 26 was almost defendless against attacks from rear sector whichwas the direction of most fighter attacks, that meant little before mid 41 but after that situation was different. One can remove all those draggy turrets etc for longer range but when an enemy fighter appears situation chances.

Juha

 

[davebender]

Apparently I didn't make myself clear.

Do-26 had a pair of tandem Jumo 205 diesel engines on each wing.
Do-217 had a single DB603 V12 on each wing.
~600kg. Jumo205 dry weight.
.....4 x Jumo 205 engines weigh about 2,400kg.
~920kg. DB603 dry weight.
.....2 x DB603 engines weigh about 1,840kg.

Pluck tandem engine pods from Do-26 wing and put them on Do-217 wing ILO DB603 engines. The resulting Do-217x bomber would have two 880hp Jumo 205D diesel engines on each wing. Total engine power would be similiar but aircraft will weigh about 600kg more.

Or else build four engine variant of Do-217 powered by Jumo205D engines. In this case engine layout would be conventional rather then tandem.

 

[krieghund]

The info on the Ju205/Ju207 engines was previously posted here http://www.ww2aircraft.net/forum/engines/diesel-engines-34736-3.html#post980511

 

[davebender]

Yes and no.

I asked a question as to if/when the 650kg Jumo207 engine could be expected to produce 1,000 reliable hp. Any guesses?

 

[krieghund]

Are you speaking of Take-off power or maximum continuous cruise power?

 

[Shortround6]

Yes and no.

I asked a question as to if/when the 650kg Jumo207 engine could be expected to produce 1,000 reliable hp. Any guesses?

The prototype JU-86P with 207 engines was flying in 1940. The power rating may have been mentioned in Paul Wilkinson's book "Aircraft Diesels" published in 1940.

 

[davebender]

I assume 1,000hp would be take off power for Jumo 207 engine. However I'm only guessing.

 

[tomo pauk]

?
No need for guessing, the data about the engine can be easily found by following the link from the post #26 here. And it is 1000 HP, for take off and max continuous.

 

[davebender]

Junkers Engines - Jumo 206

Jumo 207A. Operational 1940.
16.6L. 805kg.
647kw take off power (880 metric hp). 500kw cruise power (680 metric hp).

Jumo 207B. Operational 1942.
16.6L. 865kg.
735kw take off power (1,000 metric hp). 551kw cruise power (749 metric hp).

Power to weight ratio well below gasoline engines. However improved fuel economy (i.e. less fuel carried) might compensate for the relatively heavy engine.

 

[tomo pauk]

Some good reading about aircraft diesels, albeit from 1940:

Diesels

 

[davebender]

Why is Jumo 205 engine so heavy? Cannot be the engine block. Twin crankshafts and vibration dampers must be massive.

 

[Shortround6]

It's diesel

It had a 17:1 compression ratio before you figure in the boost from the supercharger. While the average or mean pressure in the cylinders was lower than most petrol engine the PEAK pressure was much higher. The engine has to be able to handle the Peak pressure without breaking or bending.

 

[fnqvmuch]

wonder if the legendary double-knocker Commer didn't owe something to Junkers, albeit one crank
( - via rockers, three cylinders, and gas not oil - albeit two-stroke )

 

[wiking85]

So it sounds like you all are on board due to the diesel argument. It makes more sense than the Condor for that and the reliability issues, plus could be based out of Brittany instead of Bordeaux because they wouldn't have to worry about airfield space, which would cut a lot of distance off heading into the North Atlantic.

 

[davebender]

Seaplanes have weight and aerodynamic drag disadvantages. IMO long range military seaplanes are worthwhile only for supporting fast moving naval task forces. Otherwise you are further ahead with land based aircraft.

Versions of Ju-52 and Ju-86 airliners were powered by Jumo 205 / Jumo 207 diesel engines from mid 1930s onward. Ju-86 probably has best long range potential due to superior aerodynamics. Or else power the aborted Ju-252 with three Jumo 207 engines.

Ju-86. Already in mass production.
840 civil and military Ju-86 aircraft produced by 1939.
2 x 600hp Jumo 205C engines.
Wing fuel tank next to engine contains 170 gallons of diesel.
Passenger cabin contains 10 seats.
174mph cruise @ 8,000 feet. 193mph max.
61mph landing speed.
…..Rather low. Hence short runway will work.
Lufthansa Ju-86 flew 3,600 miles non-stop between Germany and west coast of Africa (Bathurst) while carrying 1,000lbs of mail.

Install more powerful Jumo 207 engines and put a large fuel tank in the passenger cabin. That should give you plenty of range / endurance for recon over Atlantic Ocean.

 

[wiking85]

The Do26 had retractable floats to increase its aerodynamics. Plus there was the innovative push-pull layout that the Ju86 lacked, giving the historical Ju86 airframe less than half the power of the Do26. Plus, IIRC, Dornier had the patent on the push-pull layout and development.
https://en.wikipedia.org/wiki/Junkers_Ju_86

Specifications (Ju 86R)

Data from Jane's Fighting Aircraft of World War II[18] and Warbirds Resource Group[19]
General characteristics

Crew: 2 (pilot and radio operator)
Length: 16.46 m (54 ft)
Wingspan: 32 m (105 ft)
Height: 4.7 m (15 ft 5 in)
Wing area: 82 m² (883 ft²)
Empty weight: 6,700 kg (14,800 lb)
Max. takeoff weight: 11,530 kg (25,420 lb)
Powerplant: 2 × Junkers Jumo 207B-3/V diesel engines, 746 kW (1,000 hp) each
Performance

Maximum speed: 420 km/h (260 mph) above 9,150 m (30,000 ft)
Range: 1,580 km (980 mi)
Service ceiling: 13,000 m (42,650 ft)
Rate of climb: 4.67 m/s (900 ft/min)
Armament

Guns: defensive armament of three MG 15 machine guns
Bombs: 1,000 kg (2,200 lb) of bombs

Plus the historical Jumo 207 equipped version only could travel less than 1000 miles.

 

[Shortround6]

The Do26 had retractable floats to increase its aerodynamics. Plus there was the innovative push-pull layout that the Ju86 lacked, giving the historical Ju86 airframe less than half the power of the Do26. Plus, IIRC, Dornier had the patent on the push-pull layout and development.

what patent?

Did they buy it from Handley Page?

And Handley Page might not have been the first.