Radial engines more favored in Germany, 1935-45?

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Ok, we got room for guns, now, where do we put the ammo
 
As you state cooling the heads was an issue. The legendary Porsche 959 used water cooled heads to solve that problem while retaining the traditional air cooled barrels.
 
Reluctant Poster said:
As you state cooling the heads was an issue. The legendary Porsche 959 used water cooled heads to solve that problem while retaining the traditional air cooled barrels.
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The new BMW R 1300 GS motorcycle does the same: https://www.bmwmotorcycles.com/en/models/adventure/r1300gs/technicaldata.html

(I have to admit I'm slightly confused why this would be a particularly satisfactory point on the design space. If you already have paid the extra complexity and weight of a water cooling system, why not use that to cool the barrels as well?)
 
WARSPITER said:
The eventual Ford GAA had 100 more horsepower than the the wright radial in the Sherman and was more reliable.
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It also had a longer life and didn't have the engine fires the R-975 was prone to. The R-975 was also prone to hydraulic lock resulting in bent/broken conrods. Nicholas Moran (aka the Chieftain) has excerpts from the US Army equipment reports on his website. I am having difficulty finding the second part which has specific info on the R-975 but here is the first part
Please wait...
I found part 2

The Chieftain's Hatch: ETO Equipment Reviews, Pt 2

The remainder of the assessments of the various vehicles that the European Theater thought worthy of commenting upon.
worldoftanks.com
 
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What problem did the BMW 810 solve other than being an available alternate to the Daimler Benz DB601? Are you assuming that radial engines are automatically superior to liquid cooled V12s?

The Germans failed to develop two-stage supercharges and high octane fuel. This limited the BMW801s just as much as the DB601s and DB605s.
 
You are certainly free to either take part in the thread with less of an attitude, or to ignore the thread.
 
Each type of engine has advantages and disadvantages. How well the designers manage or cope with problems while utilizing the advantages tends to make the specific engines successful or failures.
Sometimes engines have directly conflicting attributes.
Like large radials often have more cylinders which means that the cylinders are smaller, easier to cool, have greater volumetric efficiency and probably a few other things, like short stroke means lower piston speed.
However when you put 7 or 9 cylinders on one crankpin piston speed may not be the limiting factor on rpm.
Using air instead of liquid cooling also changes the cooling problems. Liquid cooled radials never made it to production after WW I?

An awful lot depended on what the companies could actually manufacture. That means actual manufacture in quantity at acceptable production levels with acceptable scrap rates.
Doesn't matter if the test engine makes it to 150 hours if you have to throw out 75% of block castings before getting to completed engines. Can you supply the needed bearings in each application in the engine?
The Hirth engine company of Germany, maker of an extensive line of air-cooled engines in the 1930s basically went out of business at the beginning of WW II for several reasons, before being folded into Heinkel as part of the jet engine program. The Hirth engines were exquisitely engineered and constructed. However they used roller bearings on the crankshaft mains and on the connecting rods which meant multipart crankshafts, they also used roller bearings on the piston pin bearings. Exquisite but EXPENSIVE, to get little better performance than the Argus or more conventional engines.
Britain would have been in a world of hurt if RR had designed the Merlin to use roller bearings. A roller bearing Merlin might have worked very well, Britain could not supply the roller bearings needed once production got passed a certain point (Hercules needed imported bearings). This does not mean that either the Merlin or the Hercules was bad, just that you need all of the supporting infrastructure to make the best use of the designs.

Different alloys allowed for different things.
 

For the German companies in particular, they haven't designed a 'military grade' radial for some 20 years - between end of ww1 and BMW 139 and Bramo 14-cyl radial that gotten nowhere? Both BMW 132 and Bramo 323 were warmed-up versions of engines from 1920s.
If the firm decision to prop-up the radial engines' design and production was made in 1936, let alone in 1935, that leaves precious 2-3 extra years for the companies to design, test and debug respective designs, so the 1200-1400 HP engines can be had already by 1939, instead of the vintage 900-1000 HP 9 cylinders as it was the case.
Perhaps merge Bramo and Argus, as well as BMW with Hirth, all by 1936?

Eg. - Bramo to make an engine similar to the Kasei (42L, pretty light at 700kg, growing to 750 kg later), introduced in 1939. 1400/1200 HP (1st/2nd gear), main user He 111? Improved versions, with bigger & better S/C, more RPM, a bit heavier grow to 1600/1400 HP by 1941, and a bit more on C3 fuel. Yes, power values no different than BMW 801, but with savings of ~300 kg just for a bare engine weight, per engine. I haven't account for gains due to Germans installing the fuel injection. Further versions might've included the 2-stage version, or a version with a big S/C, perhaps a 3-speed drive version etc.
As a follow up, have Bramo design an 18 cyl spin off, similar to the Ha 42.
 
tomo pauk said:
For the German companies in particular, they haven't designed a 'military grade' radial for some 20 years - between end of ww1 and BMW 139 and Bramo 14-cyl radial that gotten nowhere?
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Perhaps from this perspective focusing on inlines was a better choice; less conspicuous and can maybe be explained away "oh this is for a racing boat"? Then again, given the thinking in Europe at the time that fast aircraft needed inlines, developing big radials maybe could be explained as being for upcoming civilian aircraft (which, per se, wouldn't even need to be a lie)?

Perhaps merge Bramo and Argus, as well as BMW with Hirth, all by 1936?
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Do these have the R&D muscle to develop high power radials? Also, starting in 1936 is still quite late if we want a radial replacement for the Jumo 211?

Alternatively, what if Junkers "sees the light" in the 1920'ies and decides that radials are the future? That would give plenty of time to develop a few smaller radials to learn the ropes, and then develop one or two high power ones in time for WWII?
 

Focusing on the inlines takes all the fun out


Perhaps they do have the muscle, perhaps they don't have. The historical recipe meant that, for the 1st two war years, the engines series-produced by Bramo and BMW were well behind the curve, and that BMW 801 was late with upgrades that would've kept it on the forefront past mid-1943. Specifically for BMW, the incursion with 116 and 117 meant that precious time of a couple of years was wasted.
Note that I've listed both Jumo and DB keeping with liquid cooled engines for the purposes of this thread
 
tomo pauk said:
Note that I've listed both Jumo and DB keeping with liquid cooled engines for the purposes of this thread
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I'm aware; I just worry your scenario isn't ambitious enough on the organizational side of things to be able to produce the kinds of engines you want to see.

Ok, if we per your wishes fix DB and Junkers to concentrate on inlines, how about: BMW sees the radial light directly after WWI, and the BMW IV and all following aero engines are radials. These BMW radials quickly become the engine of choice for the nascent German aircraft industry and enable a substantial increase of both R&D and manufacturing capacity. Argus, Bramo and Hirth see the oncoming BMW freight train and merge in response (for lack of a better name, lets call this new hypothetical merged company "ABH"). By the time WWII starts, almost all German aircraft, civil and military except for the Bf 109, 110 and Ju 87, are powered by BMW or ABH radials. FW 190 is close to entering service, and both BMW and ABH have 18 cyl radials in advanced development. Junkers, seeing the lackluster success of the 211, forgoes the 222 and makes a "213 lite" which is essentially a 211 with pressure cooling, sturdier components for higher rpm, a 4V head, and then concentrates on jet development.
 
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Most (all?) engine companies were businesses. They made engines they could sell to make money.
Unfortunately what the engine companies thought would sell sometimes didn't sell. This varied with both time and country for different reasons.
There were a number of large engines that were built in 1920s but they were often too large. The airframe makers didn't want them of various reasons. And military customers didn't often agree with commercial customers.
For instance in The US the Liberty engine all but killed the domestic engine market from 1918 though 1925 or late 20s. It was helped by the Wright built Hispano and the Curtiss OX-5 V-8. These respectively owned the 400hp, 180-200hp, and 90-100hp markets and as cheap (really cheap) surplus engines kept most new comers out. Didn't help the engine makers much as most/all of the engines were from government surplus stocks.
Curtiss and Packard tried with their V-12s but even government sales were slow. Wright and P-W tried with their radials but again sales were slow due to glut of surplus engines.
However even the 1920s aviators soon got tired of the 1916-19 era engines that needed extensive maintenance (like pull heads and scrape carbon every 20-30 hours).
Wright capitalized on the separate cylinder feature of air cooled engines and made 5, 7, and 9 cylinder engines all using the same cylinders. Some European companies did the same.
Attempts to use 3 very large cylinders for low power never quite worked out. There was a limit to the vibration that pilots and paying customers would put up with

By about 1930 P &W was making 3 different 9 cylinder radial engines and Wright was making the Whirlwind series (5,7.9 cylinders) and the Cyclone which was pretty much a 1759 cu in engine in the 20s. P&W had the Wasp (R-1340) and two Hornets, the R-1690 Hornet A and the R-1860 Hornet B. The last was not a success despite being used in 12 different planes. Many of them were either one offs/prototypes or very low number production. It was also P & W's last attempt to make large displacement cylinders and P &W, at least on production engines always preferred to use a higher number of smaller cylinders of less than state of the art size. The R-1860 being replaced by the 14 cylinder R-1830. Wright enlarged the R-1750 to R-1820 and the race for world domination was on
The R-1860 had two problems, one was cooling that size cylinder, made worse by the state of the art in the industry of the time with being able to manufacture the needed sized finning, but would always be a problem and the 2nd was the getting the flame fronts from the dual ignition to meet in the cylinder and dealing with the 6.75 in (171.45mm) stroke. Other people used longer cylinders but as with many things, there are trade offs.
 
z42 said:
Junkers, seeing the lackluster success of the 211, forgoes the 222 and makes a "213 lite" which is essentially a 211 with pressure cooling, sturdier components for higher rpm, a 4V head, and then concentrates on jet development.
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The '213 lite' looks interesting.
Power-wise, and for early 1943 (?), half-way between the 211N and 213A (~1400 HP at 5.5 km, 1600 at SL), all on 87 oct, outfitted with swirl throttle.
For early 1944, 2-stage version, altitude power better than the 213A or DB 605AS, if worse than the 213E)? Puts it also a bit above 2-stage Merlins of the day.
 
Further to this point radial engines required higher PIN (aka Octane) than radials to avoid knocking. The US was switching to 115/145 fuel at the end of the war to increase performance of the big radials. The Merlin didn't need it. Similarly the Luftwaffe had to use the more expensive and more difficult to produce C3 in the BMW radials whereas the Daimler Benz and Jumo inlines could use B4.
 

Yes, but I think the interesting question is whether this was due to some inherent feature of radial engines, or was it just that at that point in time, the particular radial engined planes were more in need of a performance boost to keep up with the competition?

And in the case of Germany, it seems their valve/bearing/etc. problems meant that their inlines were not capable of taking advantage of the extra power higher octane fuel would provide. Again, was this something fundamentally inherent to radial vs inline engines, or was it just a fluke of history that their inlines were already so close to their design limits on B4 that a lot more work was needed for them to be able to take advantage of higher octane gas?
 
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