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2 reasons:Why not use the full 6 cylinder banks of the original engines for an H-24?
For Junkers almost anything was better than getting involved with the 222 (46.5 liters in early versions) engine in hindsight.
Jumo H-16 comes out at 46.5 liters
But the H-16 Jumo is not going to promise the small diameter and high rpm of the 222.
I can see Junkers going for the H-16 as an quick easy alternative to the Ju 222 and/or trying to get the 211 to run faster than 3000rpm.
For DB we are looking at a 45.22 liter engine compared to the 44.5 liter DB 603. Not sure if the extra cost/complexity is worth it.
DB just sat on the 603 for a while but one has got to ask, was it more difficult to make an H-16 ( vibration and layout problems) than it was to get the 603 to run at 601 speeds at the same point in time?
the radials are just a tiny bit shorter due the odd number of cylinders. Not muchLooking at the stroke of big radials, the 55.3 in wide & tall Centaurus was with the 178 mm stroke, so perhaps the Jumo and DB engines with 165 and 160 mm stroke are not to generate such a tall engine. With pistons moving vertically, they will also be less wide than the powerful radials, and thus easier to streamline than these. We'd probably be getting ~1000 kg engines from both DB and Jumo intially.
Curiously enough, the Jumo 213 was a less tall engine than the 211, despite sharing the stroke and the same basic layout.
Cheating a little bit - making the new versions having shorter stroke should give them an 'access' to the 3000 rpm operation and will result in less tall engines, while keeping both the piston speed and weight in check. The Jumo H16 is certainly an alternative to the 222.
Problem with replacing the DB 606 with the H-16 is that it has 2/3rds the displacement/power at any give level of development. They maybe able to make up some of that or maybe the H-16 is a bit light per HP than the DB 606 layout.
- He 177 indeed looks nothing like it looked before, but it is made either as a normal 4-engined bomber, or with two push and two pull engines
Prop is 10.5ft (3.2 meters)
H-16 can use a lot smaller radiator.
Left over radials are R-1830s.
2 reasons:
H16 engines were very rare.
24 cyl engines were not suitable to be retrofitted on existing aircraft due to size and weight of these engines; Ju 288C notwithstanding.
DB having a H16 engine in the works might kill both the DB 606 early on (so the He 119 uses two separate engines, and the He 177 looks like something else) and by default the 610, as well as the DB 603. So the company has just 1.5 lines of engines to debug, rather than 2.5 lines; number of engine lines is a pure whim on my part.
I wouldn't expect the H24 to be retrofitted into aircraft.
It would be in aircraft that historically were designed around the Jumo 222, DB 606, etc. So He 177, Ju 288 (designed around Jumo 222, ended up with DB 606 and then DB 610 engines).
The H-24s gives the power that the double vee 24 engines had, the H16 doesn't.
A H24/601 should give the He 177 the same power with less fire risk!
A H16 using DB 601 cylinders will have the same frontal area as a H24. The H24 can use the cylinder blocks and crankshafts as is used on the V12, the H16 needs new cylinder banks and crankshaft.
Also, rareness isn't a reason to develop an engine.
Daimler Benz were also developing the DB 609 V16 based on DB 603 cylinders and the DB 613, a coupled DB 603 along the lines of the DB 606/610. They even had a proposed coupled DB 609.
Also, they had the DB 604 X-24 under development early in the war. That was capable of around 2500hp.
With its shorter stroke, it might have made for a more compact H24 than DB 601 or DB 605 if they decided to change the layout (would probably need a new crankshaft design, though).
Well, they had to fit it on the existing airframe. Even with 5 blades it was not big enough to handle the power of the 24 cylinder engine.Tiny prop there - it will hardly suffice on a single Jumo 213, despite having 5 blades?
The 'no free lunch' rule applies as ever - if you want more power, prepare to pay in size+weight, unless you want to risk it with a bespoke design, that might and might not mature fast enough.Just tying to give a context of the size. It is roughly the size (diameter) of an R-2800/R-3350/Centaurus but a little skinner.
The 211 H-16 is 46.7 liters (2847cu in) so it is not a surprise. Frontal area of the R-2800 is 15.2 sq ft, frontal area of the Arsenal H 24 is 14.1 sq ft.
What's the advantage of a H-16 engine of 46.7L (Jumo 211 based) against the Jumo 213 of 35L and DB 603 of 44.5L?
Using the Jumo 211s as the rule of thumb, it is indeed 1600 HP, but for 1940. For 1942, 1800-1900 HP (cue Jumo 211F/J of 1340/1420 PS), and for 1943/44 1900-2000 PS (cue 211N/P). All of this is before the RPM is upped to 3250 rpm, as in case with the Jumo 213, and all with 87 oct fuel, without the swirl throttle and without MW 50. Even 3000 rpm will be good.The Jumo 211-H16 is going to give around 1,600hp. It will be shorter than the V-12s, but taller and wider. Weight?
A Jumo 211-H24 gets you into the 2,000hp engine class. Which is what the larger German aircraft needed.
For fighters, the V12s still seem the better option.
Well, it's certainly possible one is stumbling upon a great concept that history for various reasons has overlooked, but more likely people have looked at it in the past and found it wanting.Also, rareness isn't a reason to develop an engine.
In general, I'm not particularly impressed by the H16 layout for an aero engine. You pay a significant cost in complexity, weight, and frontal area and gain only 4 cylinders and a slightly shorter block than the well-trodden path of V-12s. If you're going to go through all the trouble of developing such an engine, at least make it a H24 to provide a significant leap over the V-12s.
In retrospect, IMHO Germany should have focused on improving their V-12s. Like solving the valve and bearing issues, improved (multi-stage) superchargers, making them in general sturdy enough to fully utilize the capability of C3 fuel, etc. Forget all the X, H, W (coupled V's), V-16 etc. Spend the "ooh shiny" budget on turbines. If two 603s or 213's (or 801's if we include radials in this scenario) aren't enough on a big plane, put four of them in a tractor config ahead of the wing like the rest of the world.
Ability of a 24 cyl engine, that is long and at ~1300 kg, to be trouble-free retrofitted on an established aircraft design is close to zero. So I'd stay clear from it, and where the loads of power are required, as in the case of really big bombers, use 4 engines.
Weight and size of a 16 cyl engine allows it to be retrofitted on an existing airframe much easier. Hence this thread.
In case of Germany, the retrofit might've made sense on a Fw 190, Ju 88/188/288/388, Do 217, even on the He 111 and Ju 87.
A H16 spin-off is still very useful even under the historical conditions of German having very restricted access to the (for them) rare metals that made them a lot of problems, as well as with S/Cs at the historical level.
The improvements in valves, bearings, S/Cs and ability to withstand greater boost levels can also be siphoned to the H16 engines, meaning heaps of power when everything is said and done, while still doing well with the fuel that Germans had the most - the 87 octane.
Date | V-12 | H16 |
1937 | Jumo 211A, 1,000 hp | prototype |
1940 | Jumo 211D, 1,200 hp | H16A 1,335 hp |
1941 | Jumo 211F, 1,350 hp | H16D 1,600 hp |
1943 | Jumo 211F, 1,500 hp | H16F 1,800 hp |
1944 | Jumo 213A, 1,750 hp | H16P 2,000 hp |