Merlins > Packard vs RR

[Reluctant Poster]

Both. Generally early CCF Hurricanes used RR imports and later ones used Packards.

Canadian built Hurricanes with Merlin engines - Luftwaffe and Allied Air Forces Discussion Forum

The majority of CCF Hurricanes were built with the Packard Merlin Mark 28 or later 29. The only difference between those marks was the propeller shaft. The 28 used the std British shaft while the 29 used the std American shaft. CCF Hurricanes with Hamilton Standard props can be recognized by the lack of a spinner due to the bulk of the Ham Stan. The HS prop was also much heavier than the equivalent Rotol.

 

[GregP]

Hi Wayne,

The British did not USE a U.S.-supplied injection carburetor nor the SAE shaft splines nor SAE fasteners and other hardware, so there isn't really any British equivalent for a V-1650-3 or -5. The internals may have matched similarly to the Rolls design (as I would expect since we made "Merlins"), but the engines are NOT interchangeable unless you also interchange props, tool sets, and engine mounts. It's not that TOUGH to change one over, but it also isn't a "swap one for one" deal, either. Heck, we have an interesting time even trying to GET Whitworth bolts here in the U.S.A. , much less Whitworth wrenches and sockets. You can find them, but not at the local hardware store.

Some parts of a Merlin WERE interchangeable, and the head castings were the same for British and U.S. Merlins, at least center-to-center of the head bolts. Probably slightly different diameter holes, but I'm not sure since I have only worked on Packard-Merlins and never measured the head bolt holes for ANY Merlin, or Allison either, for that matter. Never needed to do so. But, you wouldn't try to install a British "machine to fit" part on a Packard Merlin unless you were out of interchangeable parts. Then it makes sense to "fit" a part if that's the only practical way to return the engine to service. Later British mass production parts may BE interchangeable with each other, but are they interchangeable with Packard parts? My contacts say "No," but I'm also not working much with warbird engines like I used to.

I'm playing more with my Ford Coyote V8 than airplane engines at present, and am having more fun doing it, too.

 

[Milosh]

Didn't Lancasters have a mix of engines on the same a/c? No R/R engine available, a Packard would be fitted.

 

[pbehn]

Hi Wayne,

The British did not USE a U.S.-supplied injection carburetor nor the SAE shaft splines nor SAE fasteners and other hardware, so there isn't really any British equivalent for a V-1650-3 or -5. The internals may have matched similarly to the Rolls design (as I would expect since we made "Merlins"), but the engines are NOT interchangeable unless you also interchange props, tool sets, and engine mounts. It's not that TOUGH to change one over, but it also isn't a "swap one for one" deal, either. Heck, we have an interesting time even trying to GET Whitworth bolts here in the U.S.A. , much less Whitworth wrenches and sockets. You can find them, but not at the local hardware store.

Some parts of a Merlin WERE interchangeable, and the head castings were the same for British and U.S. Merlins, at least center-to-center of the head bolts. Probably slightly different diameter holes, but I'm not sure since I have only worked on Packard-Merlins and never measured the head bolt holes for ANY Merlin, or Allison either, for that matter. Never needed to do so. But, you wouldn't try to install a British "machine to fit" part on a Packard Merlin unless you were out of interchangeable parts. Then it makes sense to "fit" a part if that's the only practical way to return the engine to service. Later British mass production parts may BE interchangeable with each other, but are they interchangeable with Packard parts? My contacts say "No," but I'm also not working much with warbird engines like I used to.

I'm playing more with my Ford Coyote V8 than airplane engines at present, and am having more fun doing it, too.

I think this is a situation that would only happen in post war warbird set ups though wouldn't it? When engines were taken out in WW2 they were sent for re build, not rebuilt there in the hanger with parts laying about.

 

[pbehn]

Didn't Lancasters have a mix of engines on the same a/c? No R/R engine available, a Packard would be fitted.

I found this, my bold, but did they use the same or both types at the same field at the same time?

Demand for the Rolls Royce Merlin engine constantly threatened to outstrip supply. One solution was the manufacture of Merlin engines by the Packard motor company in America. These Packard Merlins were used in a variety of aircraft, but perhaps the biggest consumer was the Lancaster III, of which 3,039 were built (requiring over 12,000 engines). The use of the Packard Merlin 28, capable of delivering 1,420 hp at take-off was the only difference between the Mk I and the Mk III.

Avro Lancaster III of No.619 Squadron
As would be expected, the performance of the Packard Merlin powered Lancaster was very close to that of Rolls Royce powered aircraft. Many RAF Squadrons used both types. The only exception was that the Packard Merlin was slightly more likely to overheat during take off and landing, making it less suitable for use in training units.


The Lancaster Mk III was constructed on the same Avro construction lines as the Mk I, with the choice of engines dependent on availability. The Mk III entered production towards the end of 1942, and entered service during 1943. Production continued throughout the war. A number of Mk IIIs were amongst the aircraft modified to carry the famous "bouncing bomb" used on the Dambusters raid.

 

[wuzak]

Hi Greg,

The British did not USE a U.S.-supplied injection carburetor nor the SAE shaft splines nor SAE fasteners and other hardware, so there isn't really any British equivalent for a V-1650-3 or -5.

No, the British built Merlins did not use the US injection carburettor. No, they did not use the SAE output shaft.

Packard Merlins did not use SAE fasteners. Except, maybe, the supercharger drive system. They even used all the little BA screws to join the supercharger housings together and hold down the rocker covers.

The V-1650-7 was supplied to the British as Merlin 266s. They differed from the Merlin 66 in the supercharger drive (epicyclic, designed by Wright) and the injection carburettor.

The Merlin 266 only differed from the V-1650-7 in the output shaft.

The Packard V-1650-3 was, absolutely, the equivalent of the Merlin 63. Because that is what it was based on.

The Packard V-1650-7 was the equivalent of the Merlin 65/66. Because that is what it was based on.

The Packard V-1650-9 was a Merlin 100 series. I can't recall which model it was equivalent to, maybe the 113/114. Maybe the 130/131.

The difference between the V-1650-1 and British Merlin XX variants was the injection carburettor and prop shaft. They were supplied with SBAC prop shafts, but otherwise identical, to the British as the Merlin 28.

The internals may have matched similarly to the Rolls design (as I would expect since we made "Merlins"), but the engines are NOT interchangeable unless you also interchange props, tool sets, and engine mounts. It's not that TOUGH to change one over, but it also isn't a "swap one for one" deal, either.

As mentioned by others above, if a Rolls-Royce Merlin needed maintenance it could be, and was, swapped for a Packard Merlin in aircraft such as the Lancaster.

Don't know why you think the engine mount would change. The output shaft could be easily changed.

Some parts of a Merlin WERE interchangeable, and the head castings were the same for British and U.S. Merlins, at least center-to-center of the head bolts. Probably slightly different diameter holes, but I'm not sure since I have only worked on Packard-Merlins and never measured the head bolt holes for ANY Merlin, or Allison either, for that matter.

MOST of the parts were interchangeable.

The heads were the same. They were built to Rolls-Royce designs and specs.

But, you wouldn't try to install a British "machine to fit" part on a Packard Merlin unless you were out of interchangeable parts. Then it makes sense to "fit" a part if that's the only practical way to return the engine to service. Later British mass production parts may BE interchangeable with each other, but are they interchangeable with Packard parts? My contacts say "No," but I'm also not working much with warbird engines like I used to.

"Machine to fit"? I suppose that is an improvement from "file to fit" which is often the term used in this MYTH.

The only engines that were individually fitted were the prototype versions used by Rolls-Royce to test new parts and power ratings. These were built in the tens.

The "later British mass production" Merlins appeared before any production Packard Merlins.

Why do you, logically, think that a part built in Britain to a set of specs and tolerances not fit in place of a part built in the US to the exact same specs and tolerances?

 

[GregP]

Well Wayne,

I have a LOT more time on Allisons than on Merlins. So, my Merlin knowledge is not what my Allison knowledge is. Say, 100 times as much Allison time as Merlin time. But the guys who own these things that are friends do not feel they are interchangeable. Me, I'll go along with the guys who own one rather than the guys who don't, and they don't think the parts are all that interchangeable. Seems to me as if the guys who are DOING it think that, I can't disagree with them since I don't own one and have no incentive to prove them wrong just to do it.

In another world, where I win a lottery, I'd know these things since I'd be flying a Merlin-powered private aircraft and would have great incentive to figure it out.

The only times I have seen cylinders changed on a Merlin, it seemed like as much, if not more, of a job as it is on an Allison. The only reason it MAY seem like more of a job is because I am less familiar with Merlin work than Allison work. I have actually participated in changing out cyinder liners on an Allison. Since the steps aren't the same for the Merlin, maybe I SAW it as more complex when, in fact, it wasn't if you are familiar with it.

I KNOW the V-1650-3 was based on the Merlin 63, but have never heard anyone but you say they were interchangeable. I KNOW the V-1650-7 was based on the Merlin 66 but, again, have never heard anyone else say they were interchangeable. Most of the P-51s I am familar with are not really a V-1650-3 or -7 these days. They are sort of hybrids, and run the best parts they can find. Some guys are running transport heads on a V-1650-3/7. Some run a different cabruretor. If the aircraft is registered as Limited, they can't. But, if it is in the Experimental or Experimental Exhibition category, they can pretty much run whatever they want to run.

I do not believe the Packard Engines starting with the V-1650-9 were based on any British engine dash number. They were Packard developments. Certainly the -21, -23, and -25 were not Rolls-Royce dash number based. They also were not manufactured in any numbers, being experimental. I think they made 40 of the -23 and 40 of the -25 engines, but I don't know how many -21's were built.

 

[Greyman]

Sorry if this was covered but what is the power of a Lancaster X Packard Merlin at +14 boost compared to a Merlin 24 running +18 boost?

Would this be where the '82%' figure comes from?

A&AEE compared a Lancaster X (KB.721) to a normal Lancaster III (JA.918) and concluded that there was 'very little difference' in climb and 'no significant difference in performance' with regard to level speeds.

 

[wuzak]

I KNOW the V-1650-3 was based on the Merlin 63, but have never heard anyone but you say they were interchangeable. I KNOW the V-1650-7 was based on the Merlin 66 but, again, have never heard anyone else say they were interchangeable. Most of the P-51s I am familar with are not really a V-1650-3 or -7 these days. They are sort of hybrids, and run the best parts they can find. Some guys are running transport heads on a V-1650-3/7. Some run a different cabruretor. If the aircraft is registered as Limited, they can't. But, if it is in the Experimental or Experimental Exhibition category, they can pretty much run whatever they want to run.

Apart from the output shaft, a V-1650-7 is interchangeable with a Merlin 66. And the -3 with the Merlin 63. To fit it to a British aircraft you would either change the output shaft or change the prop.

I do not believe the Packard Engines starting with the V-1650-9 were based on any British engine dash number. They were Packard developments. Certainly the -21, -23, and -25 were not Rolls-Royce dash number based. They also were not manufactured in any numbers, being experimental. I think they made 40 of the -23 and 40 of the -25 engines, but I don't know how many -21's were built.

The V-1650-9 was a Merlin 100 series. It was rated either RM.14SM or RM.16SM, I can't recall which. Either way, there were several Rolls-Royce Merlin marks with the same ratings.

Apart from the output shaft, supercharger drive and carburettor, the -9 differed from British marks in having ADI.

I don't know about the -21, -23 and -25, except that the -23 and -25 were used on the P-82 (the -23 being LH rotation version of -25) according to wiki.

I believe the -11 was an experimental version with a variable speed supercharger drive.

 

[wuzak]

According to Lumsden, the -21 was a left-hand version of the -9, the -23 was a right hand version of the -21 and the -25 was similar to the -21.

The -9 had the same rating as the Merlin 110, Merlin 113 and Merlin 114, RM.16SM.

Note that Rolls-Royce mark numbers varied for small changes, such as reduction gear ratio. So -9, -2, -23 and -25 may have been similar except for some detail changes.

Lumsden also says the -11 was similar to the -9 but with a modified fuel system.

 

[pbehn]

If there was a substantial difference between the power output of Rolls Royce and Packard engines at the same setting then there would be an immediate investigation because it denies the laws of physics. Pending a solution of that Rolls Royce engines would be put in those aeroplanes that needed it most that would be P-51s and Lancasters carrying Tall Boys and Grand Slams which were instructed to return with the bomb if not used. In fact the opposite was the case. The difference in performance of RR Merlin engined aircraft like the Spitfire Mk IX and a P-51B/C D are because of aerodynamics not power output.

 

[fastmongrel]

Didn't Lancasters have a mix of engines on the same a/c? No R/R engine available, a Packard would be fitted.

I dont think this happened in Britain or at least very rarely but it certainly happened in other theatres. My late Father was a Cpl instrument fitter on a Coastal Command Sqdn in the eastern Med around 1947/48 that flew Lancasters in the Anti Sub and Air Sea Rescue roles. He mentioned that RR and Packard engines were mixed it wasnt a regular thing but when all that was available was a Packard the swap could be done in roughly the same time as fitting an RR.

Relatively few changes were needed to the aircraft, different pitot head, different ignition switches and a change to the throttle wires which I believe were related to the Bendix pressure carb.

 

[wuzak]

If there was a substantial difference between the power output of Rolls Royce and Packard engines at the same setting then there would be an immediate investigation because it denies the laws of physics. Pending a solution of that Rolls Royce engines would be put in those aeroplanes that needed it most that would be P-51s and Lancasters carrying Tall Boys and Grand Slams which were instructed to return with the bomb if not used. In fact the opposite was the case. The difference in performance of RR Merlin engined aircraft like the Spitfire Mk IX and a P-51B/C D are because of aerodynamics not power output.

And the Spitfire XVI did not have a performance advantage or deficit compared to the Spitfire IX, despite being the same aircraft but fitted with a Packard Merlin.

 

[wuzak]

Relatively few changes were needed to the aircraft, different pitot head, different ignition switches and a change to the throttle wires which I believe were related to the Bendix pressure carb.

Yes, there were changes required to suit the injection carb. One of the main differences, other than the engines themselves, between the Lancaster I and III.

 

[pbehn]

And the Spitfire XVI did not have a performance advantage or deficit compared to the Spitfire IX, despite being the same aircraft but fitted with a Packard Merlin.

If there was a substantial difference because of manufacture in any way there would be an immediate investigation to bring the lower powered engine up to the performance of the other no matter which it was. The differences quoted are along the lines of the difference between Merlin and Griffon or single and two stage supercharger at some altitudes. There wouldn't need to be some explanation where the power difference was coming from or going to.

 

[MiTasol]

Relatively few changes were needed to the aircraft, different pitot head, different ignition switches and a change to the throttle wires which I believe were related to the Bendix pressure carb.

Lancaster 10 KB926 had Packards when I worked on it in Calgary and it had the standard British ignition switches. From memory the parts list showed that applied to all Lanc 10s.

The pitot is not in any way related to the engine installation - it is purely for airspeed calculation - so there is no reason to play with that.

After 50 years I cannot remember if KB976 had a separate idle cutoff control but certainly many British aircraft (Spitfire and Hurricane for example) did. I am fairly confident KB976 used the standard American set up of idle cutoff built into the mixture lever. That would have required changes when changing between RR and Packard engines.

 

[chris mcmillin]

One thing about the Merlin in the US durring the war. It took an average of 320hrs to overhaul and 198 average to overhaul an Allison. I don't know for sure but this might illistrate the complexity/precision required for the Merlin engines. That would make the Merlin more dependant of careful assembly and would result in a wider variation in power output possible between engines.

wmaxt

Because the cam, followers, fingers of the Merlin head were so complicated. More time in assembly and set-up than the simpler Allison head.
Supercharger on the -3,-7,-9 Packard V-1650 is essentially two blowers, equals more time yet.

 

[fastmongrel]

The pitot is not in any way related to the engine installation - it is purely for airspeed calculation - so there is no reason to play with that.

I am only going by what my dad told me 30 or 40 years ago so that's 2 lots of fallible memory the information is filtered through.

I should do some research and not rely on memory. It's why I am always a bit wary of the "I spoke to a veteran and he said" anecdotes.

 

[MiTasol]

I am only going by what my dad told me 30 or 40 years ago so that's 2 lots of fallible memory the information is filtered through.

I should do some research and not rely on memory. It's why I am always a bit wary of the "I spoke to a veteran and he said" anecdotes.

In his recent autobiography the Australian historian Geoffrey Blainey said something like memory is not a reliable source. I totally agree, and am equally guilty of the results.

 

[Reluctant Poster]

Although many sources claim that the V-1650-3 was the equivalent of the Merlin 63 that in fact is not true. There was a significant difference in the supercharger design resulting in better performance for the V-1650-3. When the V-1650-3 was being scheduled for production Rolls Royce asked Packard to adopt the much-improved supercharger they had developed for the Merlin 66. Here is the memo from Hives to Lapin on this subject.
"It seems these modifications might be standardized from the start in American and full details are therefore attached for your information. Briefly the modifications consist of the adoption of thin vane diffusers in place of the existing wedge vane type, modified circular arc rotating guide vanes on both stages, and an increase in the first stage rotor diameter from 11.5 ins. to 12 ins……….You will note an increase of 2,500 ft in full throttle height for F.S. gear."
The reason people compare the V-1650-3 to the Merlin 63 is that it Packard used the higher supercharger gear ratios of the 63's supercharger drive. Rolls Royce however recommended the lower gear ratio for the same reason they lowered the gear ratio for the Merlin 66, to improve performance at low altitudes. The FW 190 was close to the Merlin 63 Spitfire IX in performance at low altitudes but was way behind over 20,000 feet, therefore Rolls adopted gear ratios that improved low altitude performance while retaining the excellent high level performance. It is a common misconception that the Spitfire LF IX was a dedicated low-level fighter, like the LF V. In fact, the high-altitude performance of an LF IX was superior to the vast majority of WWII piston engine fighters. As an example, the Russian used the LF IX as their standard high-altitude interceptor well past the end of WWII. Eventually Packard followed Rolls Royce's advice and used the lower gearing on the V-1650-7. Rolls Royce later developed a high-altitude version of the Merlin 66 known as the Merlin 70 which was installed in the Spitfire HF IX.
When comparing the performance of the V-1650-3 the appropriate model should be the Merlin 70 not the 63.