Pratt vs Wright

[swampyankee]

Hi Kitplane01,

I find it odd, too, that the Wright and the Pratt are basically interchangeable, but they are. Not really, because they fit different engine mounts and connections, but practically, yes.

Case in point:
1) The Pratt R-1830-S1C-G: 1,200 HP @ 2,700 rpm, diameter 48", dry weight: 1,250 lbs. Generally the series is 800 to 1,350 HP. Most 1,000 - 1,350 HP.
2) Wright R-1820-G2: 1,000 HP @ 2,200 rpm, diameter: 54.25", dry weight: 1,184 lbs. Generally the series is 700 to 1,525 HP. Most 1,000 - 1,350 HP.

The engines were being sold to the same customers for the similar or even the same aircraft. Both CW and P&WA were selling to airlines before WW2; if you want different engines on a DC-3, they need to give the same payload and performance, so the engines need similar weight, power, and size.

 

[GregP]

Hi Biff,

Regardless of dash number, these engines were and are both generally in the 1,000 to 1,350 HP class except for very early models that were under 1,000 HP and some high-performance models that made it up to 1,500 HP or so. By and large, they were as stated above. I'll not indulge in nitpicking about specs, there are too many dash numbers to worry about. If you build one up today, it's like building up an Allison or a Merlin … you somewhat use mix-and-match parts to get a running engine. The dash number on the dataplate may or may not exactly match the internals. Many overhaulers use the best parts they have to finish an engine … IF parts are needed, and they might or might not be the same dash number part as what came out of the engine being overhauled.

Notice the DC-3 appears in both lists of uses for the engines.

1) P&W R-1830:
A general list of aircraft use includes:
Bristol Beaufort (Australian-built production), Bloch MB.176, Boeing XB-15, Budd RB Conestoga, Burnelli CBY-3, CAC Boomerang, CAC Woomera, Consolidated B-24 Liberator, Consolidated PBY Catalina, Consolidated PB2Y Coronado, Consolidated PB4Y Privateer, Curtiss P-36 Hawk, Douglas C-47 Skytrain, Douglas DC-3, Douglas DB-7 (early variants only), Douglas TBD Devastator, FFVS J 22, Grumman F4F Wildcat, I.Ae. 24 Calquin, Laird-Turner Meteor LTR-14, Lioré et Olivier LeO 453, Lisunov Li-3 - A Yugoslav version of the Soviet Lisunov Li-2, Martin Maryland, Martin M-130, Restored Mitsubishi A6M Zero warbird aircraft, Republic P-43 Lancer, Saab 17, Saab 18, Short Sunderland V, Seversky P-35, Vickers Wellington IV, VL Myrsky, Vultee P-66 Vanguard.

2) Wright R-1820:
A general list of aircraft use includes:
Bloch MB.221, Boeing B-17 Flying Fortress, Boeing 307, Brewster F2A, Curtiss AT-32-A Condor, Curtiss SBC-4 Helldiver, Curtiss P-36 Mohawk, Curtiss SC Seahawk, Curtiss-Wright CW-21, Douglas A-33, Douglas B-18, Douglas DC-2, Douglas DC-3 (DST, G-102 and G-202), Douglas Super DC-3, R4D-8 / C-117, Douglas DC-5, Douglas DF Wright SGR-1820G-2, Douglas SBD Dauntless, FMA AeMB.2 Bombi, General Motors FM-2 Wildcat, Grumman TF-1 / C-1 Trader, Grumman E-1 Tracer, Grumman FF, Grumman F3F, Grumman XF5F, Grumman XP-50, Grumman HU-16 Albatross, Grumman J2F Duck, Grumman S-2 Tracker, Lockheed 14, Lockheed Lodestar, Lockheed Hudson, Martin B-10, North American NA-44, North American O-47, North American P-64, North American T-28B/C/D Trojan, Northrop YC-125 Raider, Piasecki H-21, Polikarpov I-16, Ryan FR Fireball, Sikorsky S-58/HUS/HSS/H-34, Vultee V-1.

 

[Reluctant Poster]

I wonder what happened in the back rooms of the Pentagon and Congress. We should recognize the potential influence of who knew who. If Defence firms, like P&W in the later postwar period can skate a little close to the rules, I'm sure they did the same back in the 1940s and 50s.

Curtiss Wright was BREAKING the rules during the war. That's why they were investigated by the Truman Committee. If they were held to a stricter standard post war it was their own fault.

 

[swampyankee]

Curtiss Wright was BREAKING the rules during the war. That's why they were investigated by the Truman Committee. If they were held to a stricter standard post war it was their own fault.

More than breaking the rules, they had some serious quality and serviceability problems.
See http://www.enginehistory.org/Piston/Wright/R-2600/R-2600CaseHx.shtml
http://www.enginehistory.org/Piston/Wright/R-2600/R-2600Lockland.shtml
http://www.enginehistory.org/phpbb/viewtopic.php?t=954&sid=e7da1e4156145c6a0ef5b0be99565f8d

 

[kitplane01]

So far no one has argued that either engine had a technical superiority to the other. Yes??

 

[Shortround6]

So far no one has argued that either engine had a technical superiority to the other. Yes??

With their long production times and multiple models the lead (technical superiority) may have swapped back and forth a few times. Hidden in the dash numbers are some rather different engines. The first R-1820 shipped in July of 1930 and the R-1830 had design work start Dec 1929, first run in April of 1931 and first flight in June 1931. First non company flights may have been in the XB-14.
While you can certainly swap parts around between dash numbers of the same series engines it gets a lot harder when you have different series engines. Wright went through 5(?) different crankcases on the R-1820 series, maybe more?
cast aluminium on the E series
Forged aluminium on the F and G
Steel on the G-100
different steel crankcase on the G-200
Not sure on the H but it used 20 cap screws to hold each cylinder down rather than the 16 on earlier engines.
Some of the early R-1820s ran on 73 octane fuel, the last ran on 115/145. Last R-1820s were built in 1963.

 

[swampyankee]

So far no one has argued that either engine had a technical superiority to the other. Yes??

For the R-1820 vs R-1830? No. Post-WW2, the R-1820 seemed to get more development effort (the most powerful version of the R-1820 was rated at about 1,425 HP; the most powerful R-1820 at 1,350 HP. If the R-1830 was equally developed as the R-1820, with the same power per unit piston area, about 1,780 HP would be achieved).

Pratt&Whitney Aircraft vs Curtiss-Wright is a wider topic than R-1820 vs R-1830. P&WA had a narrower range of engines, though: it's smallest was the R-985, while C-W had three engines significantly smaller than Pratt's smallest engine; these were the R-540, the R-760, and the R-790.

 

[Shortround6]

A fair number of the post WW II R-1820s were used in helicopters where it's higher power to weight ratio was an advantage and everything was shaking around so much the vibration from the big 9 cylinder engine might have been lost.

You would really have to comb the records to find out which introduced valve gear lubricated by engine oil first (or converted to all internal oil lines) Wright used the first two speed supercharger between the two of them, P&W introduced two stage supercharger in this race. Which introduced things like stellite faced valves or different bearing materials or other improvements first also takes a lot of digging, both increased the amount of cylinder finning for cooling over the years, the R-1820 starting from a bit further behind (but was in service first) but ending with more, in part because P&W stopped development of the R-1830 to concentrate on other engines.
Totally by coincidence, many of the Wright powered S-58/H-34 helicopters were repowered with P&W (of Canada) turbines.

 

[tomo pauk]

SR6,
Are these the two different engines found in the F4F / FM-2?
Cheers,
Biff

FWIW, attached is the respective power chart for the engines used on F4F-3/-4 and FM-2, military power, from the book 'America's hundred thousand'. Note that term 'neutral' here is only applicable for the 1st stage of supercharging (a.k.a. auxiliary blower, or auxiliary compresor) on the 2-stage R-1830 engines - in other words, the 1st stage is disengaged.
The 2nd stage (a.k.a. engine-stage, or integral blower, or integral compressor) was always on in it's only one possible 'speed' (gear). Here, the terms 'low speed' and 'high speed' are applicable for the 1st stage of S/C for the 2-stage R-1830 here (= S/C stage is engaged), as well as for the one and only supercharger stage of the R-1820.

The water injection that was used on many FM-2s upped the boost from 44-46.5 in Hg (military power max boost) to 52 in Hg, for perhaps extra 100 HP under the rated altitudes.
The power curve of the 2-stage of the P&W radials is very similar in shape to the Jumo 213 series of engines, that sported 3-speed supercharger gearing.

 

[swampyankee]

A fair number of the post WW II R-1820s were used in helicopters where it's higher power to weight ratio was an advantage and everything was shaking around so much the vibration from the big 9 cylinder engine might have been lost.

You would really have to comb the records to find out which introduced valve gear lubricated by engine oil first (or converted to all internal oil lines) Wright used the first two speed supercharger between the two of them, P&W introduced two stage supercharger in this race. Which introduced things like stellite faced valves or different bearing materials or other improvements first also takes a lot of digging, both increased the amount of cylinder finning for cooling over the years, the R-1820 starting from a bit further behind (but was in service first) but ending with more, in part because P&W stopped development of the R-1830 to concentrate on other engines.
Totally by coincidence, many of the Wright powered S-58/H-34 helicopters were re-powered with P&W (of Canada) turbines.

Something that may strain credulity, and is certainly high in the realm of ironies, is that Pratt & Whitney Canada built R-1820s under license.

 

[BiffF15]

FWIW, attached is the respective power chart for the engines used on F4F-3/-4 and FM-2, military power, from the book 'America's hundred thousand'. Note that term 'neutral' here is only applicable for the 1st stage of supercharging (a.k.a. auxiliary blower, or auxiliary compresor) on the 2-stage R-1830 engines - in other words, the 1st stage is disengaged.
The 2nd stage (a.k.a. engine-stage, or integral blower, or integral compressor) was always on in it's only one possible 'speed' (gear). Here, the terms 'low speed' and 'high speed' are applicable for the 1st stage of S/C for the 2-stage R-1830 here (= S/C stage is engaged), as well as for the one and only supercharger stage of the R-1820.

The water injection that was used on many FM-2s upped the boost from 44-46.5 in Hg (military power max boost) to 52 in Hg, for perhaps extra 100 HP under the rated altitudes.
The power curve of the 2-stage of the P&W radials is very similar in shape to the Jumo 213 series of engines, that sported 3-speed supercharger gearing.

Tomo,

Thanks for the chart it clears things up regards power at altitude, but begs another question. That is I was under the impression that the FM-2 was the more powerful hotter version of the Wildcat (taller rudder for increased torque). If so reading the chart I would assume the F4F is the more powerful version...

What am I missing?

Cheers,
Biff

 

[XBe02Drvr]

Some of the early R-1820s ran on 73 octane fuel, the last ran on 115/145. Last R-1820s were built in 1963.

When I left the Navy in 1974 there were still plenty of 1820s around in S2s, C1s, T28s, C117s, and even the occasional E1. No 1830s to be seen anywhere.

 

[P-39 Expert]

Tomo,

Thanks for the chart it clears things up regards power at altitude, but begs another question. That is I was under the impression that the FM-2 was the more powerful hotter version of the Wildcat (taller rudder for increased torque). If so reading the chart I would assume the F4F is the more powerful version...

What am I missing?

Cheers,
Biff

The FM2 used the lighter and more powerful (at takeoff) Wright 1820 because they were to be used on the smaller escort/Jeep carriers and the extra takeoff HP really helped. On the Jeep carriers in the Atlantic they really didn't need the small extra HP at higher altitudes since they were on convoy patrol. Hope this helps.

 

[rinkol]

The reports I've read have said that Curtiss-Wright was far more loath to spend any money on R&D and product development than was P&WA; it got far enough behind the curve so there was no catching up.

Some of the accounts at the AEHS describe a seriously dysfunctional environment within the company. It is interesting to recall that P&W was started by Wright employees who were unhappy and left. There may have also been an "Innovator's Dilemma" situation where there seemed to be little urgency in developing new products since the R-3350 looked like it would have a long life in commercial aviation. Eventually Wright licensed British engines, but ended up being too late to compete with P&W and GE.

 

[pinsog]

Tomo,

Thanks for the chart it clears things up regards power at altitude, but begs another question. That is I was under the impression that the FM-2 was the more powerful hotter version of the Wildcat (taller rudder for increased torque). If so reading the chart I would assume the F4F is the more powerful version...

What am I missing?

Cheers,
Biff

Go to FM-2 Performance Trials
And go to
F4F Performance Trials

and you can compare the difference below 10,000 feet, especially climb rate

 

[tomo pauk]

Tomo,

Thanks for the chart it clears things up regards power at altitude, but begs another question. That is I was under the impression that the FM-2 was the more powerful hotter version of the Wildcat (taller rudder for increased torque). If so reading the chart I would assume the F4F is the more powerful version...

What am I missing?

Cheers,
Biff

The FM-2 was somewhat lighter (mostly due to having 4 HMGs instead of 6), and have had the extra up to 150 or so HP under 9000 ft already on military power. Between 10000 and 15000 ft, the water-injection kit added up to perhaps 120 HP, thus more than cancelling any power surplus the 2-stage R-1830 had. The engine installation of the FM-2 was also better since it featured individual exhaust stacks for all cylinders for the better exhaust thrust - worth perhaps another 50+ HP?
So the altitude band above ~18000 ft remained the 'only' area where the R-1830-56 was superior, at least on paper and before we account for the lower exhaust thrust of the -56, however the air combat in Pacific rarely went there. There was no water injection for the R-1830-56 either (or any R-1830 in service that I'm aware of).

Neither F4F nor FM-2 were hot aircraft when compared with other fighters in respective eras. F4F/FM-2 design was unable to take advantage of the R-1830 smaller diameter vs. R-1820 since the fuselage was fattest well behind the firewall, wing was big, aircraft was big & heavy, and R-1830-56 was no better than current European engines with 1-stage supercharger, or the mainstream Japanese engines of 1942 that all featured just 1-stage S/C.

 

[xylstra]

Does anyone know the reason that CW did not do the same as P&W?

Because if the rigid, dogmatic attitude of P&W's executive engineer, Wilton

Does anyone know the reason that CW did not do the same as P&W?

Because if the rigid, dogmatic attitude of P&W's executive engineer, Wilton G. Lundquist. (Also, see his post C-W career, re Thiokol 'DynaStar'

 

[MiTasol]

I have noticed that Curtiss Wright bought working reliable jet engine designs then spent a lot of time and money tweaking and productionising the engines so they were heavier, took more man hours to build and were less reliable. If CW thought they needed so much work why buy the design.

And the same applies to Rolls Royce in the 60s when the started to licence build the Continental O-200. They proudly boasted some 200 improvements - and then the ADs started, most of which required the replacement of RR parts with TCM parts.

 

[kitplane01]

FWIW, attached is the respective power chart for the engines used on F4F-3/-4 and FM-2, military power, from the book 'America's hundred thousand'. Note that term 'neutral' here is only applicable for the 1st stage of supercharging (a.k.a. auxiliary blower, or auxiliary compresor) on the 2-stage R-1830 engines - in other words, the 1st stage is disengaged.
The 2nd stage (a.k.a. engine-stage, or integral blower, or integral compressor) was always on in it's only one possible 'speed' (gear). Here, the terms 'low speed' and 'high speed' are applicable for the 1st stage of S/C for the 2-stage R-1830 here (= S/C stage is engaged), as well as for the one and only supercharger stage of the R-1820.

The water injection that was used on many FM-2s upped the boost from 44-46.5 in Hg (military power max boost) to 52 in Hg, for perhaps extra 100 HP under the rated altitudes.
The power curve of the 2-stage of the P&W radials is very similar in shape to the Jumo 213 series of engines, that sported 3-speed supercharger gearing.

Can you please explain this chart to me?

Why does the R-1830 have less horsepower at 8,000 feet that 10,000 feet? In both cases the blower is on low, and at 8,000 feet the atmosphere is denser.

 

[Shortround6]

Because they have to part close the throttle to keep from over boosting the engine and blowing it up.

If they could engage low gear in the aux supercharger at sea level and open the throttle all the way the engine would have made around 1550-1600hp for very, very brief period of time.