Integration of PW 1830 & Wright 1820 engines

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gottschs

Airman
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16
Nov 3, 2018
Good evening all and new member,

I was wondering in any of you have insights about the issues with pre-WW2 and WW2 aircraft to upgrade engines within a series line or between PW 1830 and Wright 1820 engines. I have done some research on aircraft like the Northrop/Douglas A-17A and P-36 variant and I noticed they tested out different variants within an engine family or even switched between the PW/Wright lines (R-1535, R-1820, R-1830). I was thinking the fluid/electrical/control connections would be a complication and would be time consuming at a depot. Beyond the US PW and Wright lines, I would think the smaller 9/14 cylinder engines of Jupiter, Gnome Rhone 14N, Alfa Romeo 136, and ASh-73 could/would be almost interchangeable (obviously not the German 801 line which would have given great hp but was ~2x the weight and 20+ inches longer).

For example, the Finns were able to change all their Wright 1820 P-36's over too PW 1830...did they end up making a new smaller cowling or did they stick with the 6" larger diameter Wright cowling and live with the small speed reduction?

Thanks for any help.
 
gottschs said:
For example, the Finns were able to change all their Wright 1820 P-36's over too PW 1830...did they end up making a new smaller cowling or did they stick with the 6" larger diameter Wright cowling and live with the small speed reduction?
Click to expand...

Curtiss made Hawk75 with both engines.
Finns got:
subtypes A-1, A-2 and A-3 with R-1830-SC3-G and -S1C3-G
subtypes A-4 and A-6 with R-1820-G205-A.

Due to lack of the R-1820's and overheating problems some of the 75A's were converted to R-1830. I guess it was not difficult, as Curtiss had done it already.
 


A good question.

Fitting new fuel lines would not be hard, at least compared to making new engine mounts. It took a number of hours just to swap an identical spare engine into an aircraft. Very few engine were set up as power eggs.

for the American engines the propellers were interchangeable as the US used a standardized spline on the prop shaft. the Prop might need some adjustment as to the limits of pitch or tension on springs/oil pressure but they will physical fit. Trying to change from a US engine to a European engine could often mean a new propeller (or propshaft). And even between some European engines.

Not sure of your list of other engines. Jupiter, Gnome Rhone 14N, Alfa Romeo 136, and ASh-73.
The Jupiter was thoroughly obsolete by the mid 30s and had been replaced by Bristol by the Pegasus (same bore and stroke) and while many countries built copies (licensed) it was hundreds of horsepower less than more modern 9s.
The Gnome Rhone 14N was a physically large engine (or medium?) although light in weight (for a 38.7 liter 14 cylinder) .
The Alfa 126 and kin were licensed Jupiter/Pegasus 9 cylinder engines. the 135 was sort of two Bristol Mercury's but back to back to form an 18 cylinder engine (over 2000lbs) and the 136 was never made.

The ASh-73 was an 18 cylinder engine comparable to the R-3350 used in the B-29. There were ASh-62s & 63s known as M-62s and M-63s at the time that were Russian developments of the R-1820 cyclone that were converted to metrics.
 
Douglas, Grumman, and Curtiss offered aircraft with either engine. The R-1830 was a bit heavier and longer, but the R-1820 was a bit larger in diameter. They probably had different mounting points, so the mounting structure would need some redesign. I suspect that the two engines, being similar in power and weight, were considered as alternatives from early in the design process, so the manufacturers designed alternative engine mounts and made provision for shifting weights -- batteries are excellent for this -- to compensate.
 
Thanks all for the help. Good things to think about, especially the issue of different mounting brackets and the shaft/spline difference.
 

You are addressing a few issues, so:

1. Before WW2, aircraft manufacturers used many different engines on the same airframe mostly due to weight, availability, reliability and cost. Many times it went down to customer's preference. Also, some engines performed better under "military, fighter plane" conditions than others. I believe that this is one reason why the R1830 was not as popular for fighters as the R1820 was.

2. The R1830 and R1820, though having similar displacement and horsepower, are entirely different in size, weight, accessories and mounting arrangement. When it comes to mounting different engines to the same airframe, the main issues involved are maintaining the overall airplane weight and balance, thrust line and attachment points between the engine mount and airframe (where the engine loads are transferred to the airframe). Then there are the issues of cowling, exhaust, air intakes and adapting to the overall airplane shape. Just two examples: The C-47 was built with P&W R1830 twin row radials as well as with Wright R1820 single row radials. You cannot remove a P&W off a C-47 and just bolt on a R1820 - everything from the firewall forward is different. The Japanese, during WW2, built the KI100 and the KI61 Tony - same airplane, different engines (one an inverted V12, the other a radial). Both needed addressing all the issues I described before.

3. Even more difficult is when addressing European, British and American engines. The Europeans, French and German, etc., all used metric dimensions and hardware as well as their own material standards. The Brits used Whitworth hardware and their own standard for materials and hardware. When the Merlin was given to Packard to build, the Merlin underwent a process of Americanization - everything British was changed to American. That's why Merlin parts cannot be used on a V1650 and vice versa.

4. The Finns went through a program in which all the issues I described in 1 above were addressed. Not a simple process.

Hope it helps clarify the issue.

Jake
 
Thanks Jake and all the contributors. Hope everyone had a safe Remembrance and Veteran's Day. I was looking at the Osprey aircraft book on "P-36 hawk aces of WW2" and certainly noticed a different cowling between the PW and Wright engines especially from the Hawk 75A-4 (Cyclone engine).
 

If I may:
1. The R-1830 was every bit as popular on fighters as the R-1820.
2. I don't think that anyone suggested just yanking an engine and stick in another one. However, the same basic A/C types were manufactured with different engines, many times it was a succesful swap. Not just when different radials or V12s were used, but also a change from radial into V12 engine, or vice versa.
3. IIRC the V-1650 was pretty much the same engine as the respective Merlin, major difference being prop spline and supercharger drive.
 

That is the biggest Merlin myth that remains to this day.

Packard had to source or make British standard fasteners, including the small BA screws that held the cam covers in place.

The main difference between the V-1650-1 and the Merlin 28 (also produced by Packard) was the SAE spline prop shaft instead of the SBAC spline prop shaft. The main difference between Pacard built 28s and the British built equivalent was the carburettor.

It must be noted that Packard were contracted to build Merlins for the British - the production of V-1650-1s was a result of a stipulation in the original contract required by the US government. Namely that 1/3 of production be for US aircraft.

The V-1650-3 had greater differences to the British equivalent because it used a different supercharger drive system. This was an epicyclic type system, compared to the spur gear Farmn type used by Rolls-Royce (and on the-1).

Packard Merlins used the 2 piece block from the start of production, but they did not design it. Rolls-Royce changed to the 2 piece block later, due to war time production demands. This coincided with the changeover to 2 stage engine production. Packard did design their own system for connecting the water passages in the head to the block, but reverted to teh Rolls-Royce design once that had been perfected.

Parts could be exchanged between British and American built Merlins, though not all. The example often cited is that the British tore down used or spare engines to supply the USAAF with spare parts for the P-40F.
 
The F6F was originally designed to have the Wright R-2600 and the first two prototypes had the R-2600
XF6F-1 had the R-2600-10, XF6F-2 had the R-2600-16.
After the switch to Pratt & Whitney:
XF6F-3 had the R-2800-10, XF6F-4 had the R-2800-27, XF6F-5/6 had the R-2800-18W.
When it went to production, the F6F-3 had the P&W R-2800-10, by the F6F-5 version, it had the P&W R-2800-10W.

The F4F used both the Wright R-1820 and the P&W R-1830, too.
 
Rolls-Royce required Packard had to used British dimensions on the whole engine so it could be interchangeable with existing RAF aircraft and parts made in the UK.. Packard had to make the tools for making British hardware as none existed in the US. It took Packard 8 months to deliver the first 3 engines for RR inspection and approval. The Packard Merlin's turned out to be a better engine than the British made RR. Refer to the RR Heritage Foundation for more information.
 
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