Radial engines more favored in Germany, 1935-45?

Shortround6 said:

sorry to keep picking at this, we can figure out the power of the "better" 132 with a 2 speed supercharger pretty well by using the power figures from the existing 132 engines. Doesn't require redoing the engine. If you want more than that then we have to get really tricky.

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See here, quotes from 3 posts, I've bolded some words now:

tomo pauk said:

Indeed, both 2-speed drive and a better S/C was needed.

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tomo pauk said:

Me, I'd still make the BMW 132 with 2-speed S/C, together with a better S/C.

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tomo pauk said:

a 2-speed drive for an improved S/C would've mean a better 132?

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Three times a better (or improved) S/C is noted.
A better S/C improves the power down low, and it much improves the power at higher altitudes.

Shortround6 said:

This is the ideal world.
I have no idea why BMW didn't get a contract for one engine or the other. Like if the BMW engines were really not as good as the Jumo or DB engines or if there was some sort of politics/favoritism going on. Or if like England the air ministry decided that they only needed a certain number of engine makers of one type of engine and other companies (Fairey and Alvis need not apply).
BMW wound up making over 9,000 of the old VI type V-12s during the 1930s and licensing them to the Soviets and Japan. Having BMW voluntary give up on liquid cooled engines in the early 30s to contrate on radials????

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BMW was told by RLM in 1938 (after BMW bought Bramo) to can the V12s and to focus on making radials.

Numbers from the 1946 edition of Jane's.

132 model number...........................................F&J.........................................................K&M...........................................................N
supercharger gear............................................11.4..........................................................7.0..........................................................10.14

Take-off power....................................800/2350rpm/1.4ata.............................960/2550rpm/1.3ata..........................865/2450rpm/1.35ata
altitude power....................................890/2350rpm/1.4ata/11,500ft...........970/2550rpm/1.3ata/1480ft...........960/2450rpm/1.35ata/9,850
Climb power sea level......................720/2250rpm/1.3ata............................810/2250rpm/1.2ata...........................765/2350rpm/1.25ata
Climb power at altitude..................810/2250rpm/1.3ata/12,400ft..........830/2250rpm/1.2ata/2,780ft............865/2350rpm/1.25ata/11,000ft
Cruise power sea level....................650/2250rpm/1.2ata.............................715/2200rpm/1.1ata............................670/2250rpm/1.15ata
Cruise power at altitude............... 740/2250rpm/1.2ata/14,000ft...........750/2200rpm/1.1ata/4,900ft............765/2250rpm/1.15ata/12,800ft

If these numbers are accurate, you may well have better numbers than I do, we can expect a two speed supercharger to use both the 7.0 gear ratio numbers and the 11.4 gear ratio numbers although some consideration could used as to using the 10.14 numbers. We are trading around 1400-1600ft of altitude for a large hole in the power curve in the 5-8000ft range (?).
Again, if these numbers are accurate, there seems to be a heat/pressure problem in the supercharger. It appears that they used higher engine rpm to get the needed boost at low altitude but ran out of boost very quickly. With the higher altitude engine they are using low rpm to control the boost.

If the engine can really run at 2450-2550rpm they are limiting it to keep the airflow down and they are supposed to have a double air-intake throttles controlled by a fixed automatic datum boost pressure control. Now the 11.4 gears will take 2.65 times the amount of power to drive as the 7.0 gear and heat the intake air a lot more.

At anyrate, that is about what to expect from a 2 speed supercharger using the existing supercharger. How much improvement you can get with a better inlet?
The 132 seems to be set up backwards.

The screened inlets on either side of the #1 cylinder seem to be the throttled inlets. Maybe I am looking at things wrong but in appears that the inlet's then go down to impeller housing between the crankcase and the impeller and the open side of the impeller faces the engine. The pipes to the cylinders are further back than the inlet?

Seems to be room for improvement but may require turning the supercharger around?

Shortround6 said:

At anyrate, that is about what to expect from a 2 speed supercharger using the existing supercharger. How much improvement you can get with a better inlet?
The 132 seems to be set up backwards.
The screened inlets on either side of the #1 cylinder seem to be the throttled inlets. Maybe I am looking at things wrong but in appears that the inlet's then go down to impeller housing between the crankcase and the impeller and the open side of the impeller faces the engine. The pipes to the cylinders are further back than the inlet?

Seems to be room for improvement but may require turning the supercharger around?

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You can take a look on the post #75 for a clue or two.
Better inlet was one of things that separated the Merlin XX and 45 from the III or XII, or the Hercules 100 series from the earlier models.

tomo pauk said:

You can take a look on the post #75 for a clue or two.
Better inlet was one of things that separated the Merlin XX and 45 from the III or XII, or the Hercules 100 series from the earlier models.

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Thank you for the diagrams.
It appears that the early engines used a "normal" supercharger and the inlet from the carb looks like a rather gentle turn and well centered.
No idea why they flipped the impeller around and went to the side inlet arrangement

We do know that P&W sold four 875hp Hornets to FW to use in the prototype FW 200 and a few more for Ju 86s that were built for South Africa, Sweden and a few to south America.
These were certified for 87 octane fuel and were rated at 750hp max continuous at 7000ft.

Now this was still in the era of GE designed superchargers at P&W so the P&W superchargers were certainly something to write home about ( mostly complaints
But these 1936 (?) engines should have been up to date in other ways compared to the original 1928 license information.
It Appears that the late model Hornets used 6.5 compression and the BMWs used 6.93 (?). Older 132s with carbs used the 6.5 compression.
The US Hornets gained about 240lbs from the late 20s to the mid 30s with both versions using reduction gears. The 132s gained about another 70-80lbs but how much of that was due to the fuel injection or other changes I don't know.

There is little doubt that the Germans could have improved things further. But the Bramo 323 was already in production, and 27 liter 9 cylinder radials had a few problems unless you were willing to spend a lot of money. The R-1820 is sort of the exception and that needed a lot of money to get to where it was in 1941-42. Also needed 100 octane fuel.
The 27 liter radials were running about 80-84 % as fast as a Merlin, they couldn't use as much manifold pressure as the Merlin. They have got cooling problems You need to solve one or all three to get any significant increases in power.

Shortround6 said:

No idea why they flipped the impeller around and went to the side inlet arrangement

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They were probably looking to keep the engine short, while hoping that one 90 deg turn will reap greater benefits from the ram effect than two 90 deg turns required from the old set-up?

Shortround6 said:

It Appears that the late model Hornets used 6.5 compression and the BMWs used 6.93 (?). Older 132s with carbs used the 6.5 compression.
The US Hornets gained about 240lbs from the late 20s to the mid 30s with both versions using reduction gears. The 132s gained about another 70-80lbs but how much of that was due to the fuel injection or other changes I don't know.

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Late 132s were running at 2400 rpm vs. the early running at 2050, so there was certainly strengthening of the internals where it was judged as needed. S/C drive was more beefy.
Keeping the CR low should allow a bit greater boost for a bit more power, while hurting the mileage a bit.

Shortround6 said:

The 27 liter radials were running about 80-84 % as fast as a Merlin, they couldn't use as much manifold pressure as the Merlin. They have got cooling problems You need to solve one or all three to get any significant increases in power.

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Probably nobody expects that 9 cyl radials will mimic Merlin's level of power. For the Germans, an equivalent of the later Bristol Pegasus engines would've been very worthwhile to be had in greater numbers - Bramo 323 was about there, but the 132 was produced in much greater quantities.

Shortround6 said:

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.

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An extra cost of the Hercules was the need to import ball and roller bearings from Sweden requiring fast boats and aeroplanes to get them across the North Sea throughout the war despite Germany owning the seas and air until they got near Scotland. An equivalent would be Germany importing something vital from Ireland by sea and air into France. It may partly explain some of the extra cost of a Hercules against a Merlin. These ball and roller bearings were an important source of very high quality bearings made from Swedish steel. Those same factories in Sweden also made up an even higher proportion of German industry ball and roller bearings.
Operations Rubble, Performance, Bridford and Moonshine at sea involving Norwegian merchantmen and ex Turkish Navy fast gunboats.

z42 said:

I wouldn't be so sure about that conclusion. How can you pinpoint the reason to be the inherent features of a radial engine, vs., say, the P-51 being a very advanced low drag aero design for it's time and thus had sufficient performance without 115/145 gas?

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Your statement is purely conjecture. Normally I respond to purely conjectural statements with coulda, woulda, shoulda, but didn't. If was a simple as you postulate, they would have done it. Normally the burden of proof is on you but in this case there is available evidence that radial engines couldn't do what you claim. Grade 115/145 fuel was specifically developed to compensate for the deficiencies in radial engine cooling.

"Development of Aviation Fuels" by S. D. Heron details the history of aviation fuels. Sam Heron was intimate with the subject as he worked for Ethyl corp. Also important, he was very familiar with radial engines as he and Professor Gibson had developed the template for radial engine cylinders and heads in WWI
Air-Cooled Cylinders 1.
He also invented the sodium cooled valve. But I digress. In his booklet Heron specifically discuses fuel development during WWII.

The allies had standardized on 100/130 grade but the British were able to develop 100/150 grade with greatly improved power output in Merlin and Sabres. This could be produced without an impact on overall production.

Heron notes;
"For an air force whose major offensive power relied on mild water cooled engines, even for bombardment, as did the RAF, grade 100/150 would appear to be a contribution to offensive power. The RAF, however, had some bombers equipped with very severe air-cooled engines and in this case the advantage of Grade 100/150 was slight."

For the US he notes:
"Grade 100/150 would have been of questionable value in Army bombers and in particularly so in the case of B-29 aircraft operating against Japan.....In the case of Army fighter aircraft, Grade 100/150 would appear to have significant advantages. The liquid cooled P-38 and P-51 fighters could have gained considerable improvement in performance and this was recognized by Wright Field."

"At the time Grade 100/150 was on test both the Navy and Army wished to obtain a fuel which was better in both lean and rich properties than Grade 100/130, and such a fuel became available in the form of Grade 115/145 at the end of the war in Europe. Grade 100/130 could be reblended to Grade 100/150 without loss of total production. In air-cooled engines Grade 100/150, in general, was the equal of Grade 115/145 in regard to maximum available power but was inferior in potential cruising range. In mild liquid-cooled engines Grade 100/150, in general, was the equal of Grade 115/145 in respect to maximum power and cruising range."

"Shortly after Pearl Harbor the Army, the Navy and the British evinced increasing interest in obtaining a fuel superior to Grade 100/150. The first emphasis was on a fuel superior in both rich and lean quality. Study of the production of such a fuel indicated that if substituted for an equal amount of Grade 100/130, relative enormous amounts of steel additional to those required for Grade 100/130 would be required. Neither the Navy nor the Army felt that additional steel allotment could not be tolerated in view of its effects upon the output pf such equipment as destroyer escorts and tanks."

"As a result of joint Army-Navy-PAW studies it was agreed that as soon as demand for Grade 100/130 showed signs of slackening, production of a new grade with improved lean quality should start."

"Grade 115/145 went into production at about the time of V-E Day and for every gallon produced the production of Grade 100/130 dropped by about two gallons."

Garde 115/145 was specifically developed to compensate for the inadequacies of radial engines.

Reluctant Poster said:

Garde 115/145 was specifically developed to compensate for the inadequacies of radial engines.

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It could be argued that 100 oct fuel was specifically used on Merlins and V-1710s o compensate for their small displacement, whoe a good-sized radial was making plenty of power even on 87-91 oct fuel.

My point - every engine was a compromise. A small V12 will be in the pains to provide a propulsive power of a good 14 cyl radial, while next to impossible to provide the propulsive power of a good 18 cyl radial. Four small V12 will not be able to power a B-29, try as they might. Once we need to introduce two V12s to emulate a single 18 cyl radial, the V12s surface as the ones with inadequacies.

tomo pauk said:

It could be argued that 100 oct fuel was specifically used on Merlins and V-1710s o compensate for their small displacement, whoe a good-sized radial was making plenty of power even on 87-91 oct fuel.

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Actually "100" octane fuel was being developed by the US and the British to increase the power of all engines.
This was in 1938-39 and research had been going on for quite some time. Howard Hughes used 100 octane fuel to set the land speed record in 1935. But in 1935 100 octane fuel was little more than a laboratory sample.
By 1939-40 you had the British ordering their version of 100 octane, the US ordering their version, the French talking about it but which/what version they were thinking off???
Germans were working on 96 octane, Japanese were working on ??? and the Soviets were working on??? 95???
Italians were working on getting enough 87 octane.

Nobody had rich ratings. The British knew something was happening with aromatic compounds but they didn't know exactly what. The Americans thought that aromatics were bad juju and wanted aromatics as far from their fuel as they could get it.

Most people knew that lead could raise the octane ratings. But too much lead to fouled spark plugs and other problems.

Even Fedden was one of the strongest proponents of 100 octane in the late 30s and he was not one who would aid his rival engine makers if he didn't think the new fuel would benefit his company. He may have been thinking that higher octane fuel would benefit sleeve valves even more as the sleeve valve theology of the time was that sleeve valves would allow for higher compression on the same grade of fuel.

How much this changed in late 1940-1941-42 I don't know. They leaned how to measure the rich response of the fuel and they did lot of testing in different engines and they really learned (instead of suspecting ?) the problems that air cooled engines had. Although air cooled engines had been far from problem free in WW I and the use of excess fuel as an internal coolant was known in early WW I.

100/130 fuel certainly allowed for the continued production of the Merlin and V-1710s instead of forcing the adoption of newer/larger engines in large numbers.

Shortround6 said:

100/130 fuel certainly allowed for the continued production of the Merlin and V-1710s instead of forcing the adoption of newer/larger engines in large numbers.

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Thank you.

tomo pauk said:

It could be argued that 100 oct fuel was specifically used on Merlins and V-1710s o compensate for their small displacement, whoe a good-sized radial was making plenty of power even on 87-91 oct fuel.

My point - every engine was a compromise. A small V12 will be in the pains to provide a propulsive power of a good 14 cyl radial, while next to impossible to provide the propulsive power of a good 18 cyl radial. Four small V12 will not be able to power a B-29, try as they might. Once we need to introduce two V12s to emulate a single 18 cyl radial, the V12s surface as the ones with inadequacies.

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Absolutely not true. The big radials you admire so much used 100/130.

Reluctant Poster said:

Absolutely not true. The big radials you admire so much used 100/130.

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My admiration is not required. Needing and using 130 grade fuel is whole another ballpark than using the 150 grade fuel.
For radials working on 87-91 oct fuel, we can take a look on what Japanese did. From 1000 to 2000 HP, mostly very reliable and of light weight.

tomo pauk said:

My admiration is not required. Needing and using 130 grade fuel is whole another ballpark than using the 150 grade fuel.
For radials working on 87-91 oct fuel, we can take a look on what Japanese did. From 1000 to 2000 HP, mostly very reliable and of light weight.

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87 octane 2000 Hp show me which engine?

Reluctant Poster said:

87 octane 2000 Hp show me which engine?

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Is 1900 HP enough, as done by Ha-42, used on Ki-67 bombers?

Picture from an old book

This shows the change in the finning of the Perseus cylinder from the late 20s or 1930 to 1939/40 when the book was published.
The early Hercules used pretty much Perseus cylinders. And the Hercules needed dramatic changes in the amount of finning to reach even mid WW performance.
I know these are not poppet valve cylinders but the same principle applies. To get more power out of an air cooled engine you need to increase the cooling ability.
And you need the ability to machine the cooling fins into the steel forgings or you need a way to fasten cooling fins onto the steel barrels and machine the close space, very deep fins into the cylinder heads.
And you need to do the machining in a economic manner.
Number of groves on left had cylinder is 17. On the right you have around 45 and they are deeper. You don't have the two rows of slots at the top but you get the idea.

How many more man hours and machine time for 9 cylinders?

P&W resorted by the end of the war to using an aluminum "muff" of fins that could be 'slid' onto a smooth steel barrel to improve cooling.
Actually involved both good machining, heating aluminum muff and cooling the cylinder barrel and using a hydraulic press. Also depends on using the right alloys of aluminum and steel to have a very close if not identical co-efficient of expansion.

Wright was using sheet metal fins and a special process.

getting more than 100hp per cylinder was doable, it was not easy.

Shortround6 said:

This shows the change in the finning of the Perseus cylinder from the late 20s or 1930 to 1939/40 when the book was published.

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I've posted the similar picture depicting the finning of the early BMW 132 and on the later, indeed the later has much more of thinner finning for a greater area for the cooling air to do it's work.

Shortround6 said:

getting more than 100hp per cylinder was doable, it was not easy.

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British did it with Pegasus by some time 1938 (maybe 1937?), Bramo was 100+ with the 323P, Soviets did it with M-62, just before the ww2?
Japanese overcame 100 HP/cyl with the Kasei and Ha 109 by 1941. French needed the G&R 14R, by what time Germans were in control. Italians - it never happened.

British did it with Pegasus by some time 1938 (maybe 1937?),

Very true.

Bramo was 100+ with the 323P

also true.

Soviets did it with M-62, just before the ww2?

also true but that was sort of licensed R-1820 and used big cylinders. Not sure about the fuel. The US R-1820s needed good fuel to get much past the 1000hp mark (111hp cylinder).
The US used a lot of 90-91 and 95 octane fuel in the few years right before 1941 before they switched to the US 100 octane. And the R-1820s needed massive changes in addition to the better fuel to reach the 1100 and 1200 hp levels ( 122hp and 133hp per cylinder)

Japanese overcame 100 HP/cyl with the Kasei and Ha 109 by 1941.

A little iffier. The Kasei does get about 109hp per cylinder in 1941. The Ha 109 is not operational in 1941. The Ha 41 is making about 1260hp which is not bad for a 37.5 liter engine.
The Ha 109 also picked up about 150rpm over the Ha 41 in addition to the two speed supercharger.

French needed the G&R 14R, by what time Germans were in control.

And they never did anything with it (production wise) and the 14R pretty much failed in the post-war market. With the strangeness of French politics the French did build and use several dozen French built Jumo 213s. I would also note that the French advertising claims for the 14R tended to fall off after 1946 (result of actually testing?) although it still made take-off power. Post war was 100-130 fuel
Some of the 1940 French power levels for experimental engines seem to be wishful thinking or estimates based on fuel they didn't have.

Shortround6 said:

Soviets did it with M-62, just before the ww2?

also true but that was sort of licensed R-1820 and used big cylinders.

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Nobody said anything about how big the cylinders should be used to beat the 100 HP/cyl mark.

Shortround6 said:

Not sure about the fuel. The US R-1820s needed good fuel to get much past the 1000hp mark (111hp cylinder).

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Seems like 91-92 oct fuel for the M-62.

Shortround6 said:

The Ha 109 is not operational in 1941.

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It probably was not.

Shortround6 said:

And they never did anything with it (production wise) and the 14R pretty much failed in the post-war market. With the strangeness of French politics the French did build and use several dozen French built Jumo 213s. I would also note that the French advertising claims for the 14R tended to fall off after 1946 (result of actually testing?) although it still made take-off power. Post war was 100-130 fuel
Some of the 1940 French power levels for experimental engines seem to be wishful thinking or estimates based on fuel they didn't have.

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True.

tomo pauk said:

Seems like 91-92 oct fuel for the M-62.

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90-92 according to the I-153 manual. 1000hp takeoff. But with certain constrains 88-89 fuel (4B-70) was allowed as well.

Shortround6 said:

And the R-1820s needed massive changes in addition to the better fuel to reach the 1100 and 1200 hp levels

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The M-63 reached 1100hp in January 1939 at the latest, 93-95 fuel.