Why didn't the P&W 1830 get WEP?

[pinsog]

Why didn't the P&W 1830 get WEP? Didn't it start and end the war at around 1,200 hp with not much improvement? If so, why?

 

[tomo pauk]

Just IMO: the R-1830 draw the short straw in the P&W research repartment, with only minor upgrades that brought take off power to 1350 HP in some late war versions. Those 1350 HP being take off power. The main design effort looks to be given to the R-2800, R-4360 and R-2000.
War emergency power usualy meant installing water-injection on the engine in the US radials, and probably since FM-2 got the much upgraded R-1820 (shaved 400 lbs over the 2-stage R-1830), there was no fighter in the US arsenal that was to be powered with R-1830, hence no bother with water-injected R-1830.

The turbo R-2000 was supposed to get water injection for the installation on the Vought Flapjack in order to make 1600 HP in WER.

 

[pinsog]

Could the 1830 have made more HP at the beginning of the war 1941- December 1942 when it was really needed and really mattered? Were they being conservative with its HP rating or was 1,200 hp about all it could handle the first year of the war?
I'm just curious, I imagine the Navy and Marine pilots would have welcomed and could certainly have used a 1,350 hp rating for the first year of the war.

 

[tomo pauk]

The R-1830 started out with 800 HP. All further refinements, changes and strengthenings, along with 100 oct fuel, made the engines in 1941/42 doing 1200 HP - a 50% increase. Not too shabby, so I'd say that Allied pilots got from the R-1830 what was realistic in 1941-42. It was just so that F4F was to darned big and bulky for kind of power the R-1830 was offering, weight further upped with installation of folding wing and a pair of non-too-light .50s with F4F-4..

 

[pinsog]

I agree that the F4F-4 was way too heavy for 1,200 hp. I was just curious if they could have gotten more out of the 1830 in 1941-1942 than they did. 1350 hp in an F4F-3 would have been a much different airplane. I read that the Allison rating was too conservative early and mid-war and I wondered if they had done the same with the 1830.

 

[tomo pauk]

The two-stage R-1830 was not allowed for 2700 rpm when auxiliary supercharger was in the high gear, unlike when the aux SC was in 1st gear or it was off. So I guess that engine cooling was limiting factor already in these settings. Pushing the engine making bigger boost/power would involve even greater termal loads, not conductive to the life of engine.

BTW - by 1941/42, with a bit of foresight, the USN and USMC could've had a fighter with engine power in 1700-2000 HP range. Plus, the USMC P-40 wouldn't be that bad at all.

 

[Shortround6]

The thing with radials is that they were operating closer to the edge to begin with. The fuel guys considered air cooled engines as severe duty engines. Most liquid cooled engines were moderate duty, even at 12-15lbs boost.
The air cooled engines didn't have the gallons of coolant to act as a heat sink to keep the cylinder temperatures from going critical in less than 5 minutes.
Both the 1350hp R-1830 and the 1300-1350hp R-1820 had different finning than the 1200 HP versions. The R-1830 changed from a steel cylinder barrel with machined fins to an aluminum barrel/fins with a steel liner for one thing. The R-1830 also changed bearings and a few other things. The R-1820 changed quite a few things including a different crankshaft between the 1300 and 1350 HP versions let alone what they changed from the 1200 HP versions.
Both engines had problems delivering power at altitude even with two speed supercharger. For instance the 1350 HP for take off R-1830 gained just over 50hp at just at a bit over 13,000ft. New engine was good for 1100hp at 13500ft at 2800 rpm and the older engine (2 speed, not 2 stage) was good for 1050hp at 13100 ft at 2700rpm. The new engine gained around 60lbs in weight.
Now it might have either gained in overhaul life or at least not lost overhaul life.
But it seems like there was little growth left in the 1200hp version without major changes. Increasing boost or just adding a water injection system may not have done anything for altitude performance without a new supercharger.
BTW the R-2000 didn't exibit anywhere near the increase in power at altitude over the R-1830 than the difference in take off power seems to suggest. P & W may very well have used the same supercharger as the R-1830 or only slight different.
The R-2000 that made 1450hp for take off was good for 1100hp at 16000 ft and gained about 100lbs over the 1200hp R-1830. It actually weighed just about what the two stage engine did.

 

[pinsog]

When did the 1830 get 1350 hp? What airplane used the 1350 hp version of the 1830?

 

[wuzak]

I'm guessing that the 1350hp was the WEP rating.

As I understand it, no US engines had a war emergency rating until around 1941 or 1942.

 

[Shortround6]

The 1350hp version (-94) was used in PB4Y-2 Privateers, the power rating was for both take-off and military power up to 2000 ft. The Navy Privateers did not use turbos. A few late model B-24s used a single speed 1350hp version with turbo.
BTW the 1200 HP engines could hold 1200hp to 4900ft while running 100 rpm slower.

 

[pinsog]

Thank you for the detailed explanation

 

[rinkol]

The 1350hp version (-94) was used in PB4Y-2 Privateers, the power rating was for both take-off and military power up to 2000 ft. The Navy Privateers did not use turbos. A few late model B-24s used a single speed 1350hp version with turbo.
BTW the 1200 HP engines could hold 1200hp to 4900ft while running 100 rpm slower.

I recall seeing reports that the reliability suffered for the higher rated versions. I'm sure P&W were preoccupied with the R-2800 and R-4360. After the war they did market a new R-2180 which was based on the R-4360, but this engine gained little acceptance. Attempting to introduce such a design during the war would have been inadvisable given the adverse impact on production. Wright continued on with the R-1820 after the war, eventually reaching 1525 hp.

From a business perspective, there might have been a realization that a two row 14 cylinder engine in the 1800 cubic inch size range was always going to be at a disadvantage in cost and weight in comparison with a single row 9 cylinder engine having a similar rating. The smaller diameter was insufficient compensation, being relatively unimportant in the major applications.

 

[Shortround6]

The high powered R-1820s were used in rather specialized aircraft. Aside from helicopters were power to weight is very important the late R-1820s were used in the Grumman Albatross flying boat, and the Grumman Tracker, Tracer, Trader trio and a few others (some T-28s).
Few if any, commercial aircraft used the high powered R-1820s unless they were used/surplus aircraft.
The vast number of Surplus C-47s killed any commercial market for small airliners post WW II. There was a market for 40-50 passenger planes using two 1800-2300hp engines or up. R-2800s, Hercules or Centaurus engines. But new 20-36 seat planes using 1200-1600 HP engines were doomed to commercial failure.
By the time the C-47s were wearing out or requiring major maintenance the age of the turboprop had arrived.

 

[Shortround6]

Getting back to the original question the two American radials had several things against them as far as any real increase in power goes.
1. Already mentioned is the cooling problem. Needs new fins to really get around. Water injection would help.
2. Strength of the engine it self. The 1300hp and up R-1820s went to 20 bolts per cylinder instead of 16 to hold them to the crankcase among other changes. Increasing boost and blowing the occasional cylinder through the cowl was probably not a good plan.
3. The size of the existing superchargers. The two US engines were 1200 HP engines because they used small superchargers and accepted poor altitude performance. Many French, Italian, Russian and Japanese engines of the time (1937-41) had critical altitudes of 3-4000 meters and take-off power suffered accordingly. They catalogued engines with lower critical altitudes and better take-off power but they were rarely used.

The two US engines just didn't have a lot of extra flow left in the existing superchargers to give a lot of extra boost. Please note that the Allison was getting as much or more power from it's single speed supercharger at altitude. It was running at the equivalent of the radials on high gear.

 

[tomo pauk]

...
3. The size of the existing superchargers. The two US engines were 1200 HP engines because they used small superchargers and accepted poor altitude performance. Many French, Italian, Russian and Japanese engines of the time (1937-41) had critical altitudes of 3-4000 meters and take-off power suffered accordingly. They catalogued engines with lower critical altitudes and better take-off power but they were rarely used.

The two US engines just didn't have a lot of extra flow left in the existing superchargers to give a lot of extra boost. Please note that the Allison was getting as much or more power from it's single speed supercharger at altitude. It was running at the equivalent of the radials on high gear.

Several (most?) R-1830 variants used on military aircraft were with 11in superchargers, so I'd say supercharger size was not the culprit. The R-1820 was with either 10 or 11 in impeller. Compared with V-1710 where impeller was of 9.5 in, and most of early Merlins with 10.25 in.
The 2-stage R-1830 was with engine-stage impeller of 9.5 in and auxiliary stage impeller of 11 in.

 

[Shortround6]

Diameter is not the only dimension. Thickness or 'height' of the impeller, cross section/s of the housing, number of blades/fins on the impeller. All can affect the mass airflow of the entire unit in addition to the RPM of the impeller.
Whatever was going on the higher take-off power versions of both engines displayed only small increases in power at altitude.
For instance the post war R-1820 that was rated at 1525hp/2800rpm for take-off using 10.5lbs of boost and ADI in low gear was rated at 1250hp/2700rpm at 9lbs boost dry in high gear at 10,800ft.
The old 1200hp engine was good for 1000hp/2500rpm at 14,200ft boost unknown?
Adjusting very roughly for the difference in RPM and altitude the 1525hp engine would be making 1075-1100hp at 14200ft and 2500rpm.
Adjusting just for altitude would give about 1170-1180hp? The 27% increase in power at sea level (in low gear and using ADI) fades to around 18% more power at 14,200ft?

The 1425hp engine did it without ADI and at 2700rpm (100rpm lower) but running another 0.3lb of boost (0.5in) although rounding may have been used.

However the late model Cyclone 9s were not fighter engines, they were used for getting large airframes off the ground. Either vertically

or horizontally.

Performance at 15-25,000ft NOT being a priority for such aircraft.

 

[GregP]

One reason we didn't have War Emergency Ratings until 1941 - 1942 is we weren't IN a war until 7 Dec 1941, which it pretty damned close to 1942. The R-1830 was more or less a bomber engine, though our Seversky AT-12 (a thinly disguised 2PA), runs quite nicely on one. It is smooth and relatively vibration free when compared with an R-1820. That is probably more important for a bomber since you are going to be in it longer (slow cruise to a far away target destination) and have many crewmen more or less along for the ride unless you get attacked.

The main reason we had no fighter powered by the R-1830 is the same reason we didn't have any powered by the R-1820 after the FM-2 stopped production ... our fighter designs needed 1,500 - 2,000 HP due to the weight of things deemed essential, if we were going to get the desired performance. We COULD have designed fighters around the R-1830, but then we would have had the same choices as Jiro Horikoshi when he designed the Mitsubishi A6M Zero ... what do we have to leave off in order to get the desired perfomance level?

Instead they chose to go with more power and put in all the bells and whistles.

That takes away nothing from the very well-designed R-1830. It is reliable, smooth, relatively rugged, and holds a tune a long time when compared with some other engines. All in all, quite trouble-free if well maintained and run by the book.

 

[tomo pauk]

Diameter is not the only dimension. Thickness or 'height' of the impeller, cross section/s of the housing, number of blades/fins on the impeller. All can affect the mass airflow of the entire unit in addition to the RPM of the impeller.
...

I agree what you've said here, but I'll again state that impeller with diameter of 11 in is not a small one.

One reason we didn't have War Emergency Ratings until 1941 - 1942 is we weren't IN a war until 7 Dec 1941, which it pretty damned close to 1942. The R-1830 was more or less a bomber engine, though our Seversky AT-12 (a thinly disguised 2PA), runs quite nicely on one.
...

The R-1830 was very much a fighter engine, too, it was installed on the P-36, P-43. F4F, Boomerang, J-22.

 

[Shortround6]

I agree what you've said here, but I'll again state that impeller with diameter of 11 in is not a small one.

It is not a small supercharger in diameter but the P & W supercharger would only support 1200hp (net) in low gear (7.15) to about 4900ft
and 1050hp in high gear (8.47) to about 13,100ft granted the impeller was turning slower than in the Allison. However the impeller tip speed was 1218fps in high gear. The smaller Allison supercharger could support 1150hp to 12,000ft using a tip speed of 1093fps (8.80 gear) and 1125hp to 15,500ft using 1193fps tip speed (9.60 gear). Apparently the "smaller" Allison supercharger could supply more air over 2,000ft higher in altitude?

The R-1830 was very much a fighter engine, too, it was installed on the P-36, P-43. F4F, Boomerang, J-22.

Yes and no. The R-1830 needed either good fuel (P-36 used 100 octane) , a two stage supercharger (P-43 and F4F a bit later in timing) or both (the P-43 and F4F wouldn't have worked with 87 octane) or a very small airplane (J-22)in order to be a competitive fighter engine. and the J-22 wasn't that much faster than a 109E and had less ceiling , granted it was using less than 100 octane fuel.

 

[tomo pauk]

The V-1710 also needed 100 oct fuel to really perform; using the 91 oct in the continental USA meant boost/power restrictions.

It is not a small supercharger in diameter but the P & W supercharger would only support 1200hp (net) in low gear (7.15) to about 4900ft
and 1050hp in high gear (8.47) to about 13,100ft granted the impeller was turning slower than in the Allison. However the impeller tip speed was 1218fps in high gear. The smaller Allison supercharger could support 1150hp to 12,000ft using a tip speed of 1093fps (8.80 gear) and 1125hp to 15,500ft using 1193fps tip speed (9.60 gear). Apparently the "smaller" Allison supercharger could supply more air over 2,000ft higher in altitude?
...

Here we deal with another property or two of a supercharger system: quality/efficiency of the impeller, and 'cleanliness' of the air passages, both before carb and aft the impeller. Perhaps Allison did a better job here than P&W, since Allison swiched rathear early to the impeller with curved/'grabbing' vanes for example?