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Building the Rolls Royce Merlin engine, doc

Great chapter on "this side of pond effort" at the Packard plant in Packard A History of The Motorcar and The Company by B. R. Kimes.

New dedicated plant, tooled up, genned out over 50,000 Merlins - all in 30 months
 
The " Ford Motor Co " built a huge " Shadow Factory " at Trafford Park near Manchester to churn out Merlin engines for the Lancaster bombers that were being built in the nearby " Avro " factory in Chadderton about 7 or 8 miles from where I live.
I read somewhere that they were thought to be the best Merlins, better than the " Rolls-Royce " and " Packard " engines.

Regards Tyrone.
 
In "Not Much Of An Engineer" (a wonderful book and highly-recommended), Stanley Hooker tells of asking the Ford engineers to review the Merlin drawings with a view to beginning manufacture.

The Ford engineers, after a week or two, replied that they were having difficulties with the tolerances and asked for a meeting.

Hooker and the other RR engineers thought that this was because they couldn't meet the high standards of RR but, at the meeting, the Ford engineers explained that they worked to much tighter tolerances in their car engines than RR did in their aero engines.

The result was a considerable amount of plan re-drafting to meet the higher standards of Ford.

Sir Stanley was a gentle, modest genius who didn't mind telling a story against himself.

The book is quite expensive now but should be available through the library system; read it if you possibly can.
 
A "bookend" to the documentary posted by the OP is "Men Bet Their Lives On It". This is a youtube about how Packard took on the building of the Merlin engines. It goes into considerable detail as to how Packard built a whole new plant for the job, and how they handled the design work. As noted, apparently Rolls Royce did not use a system of tolerances as tight as Packard worked to, and used some different system of making their drawings. Packard engineering had to re-draw the entire set of working drawings and then drawings for the tooling in order for them to setup and build Merlin engines.

I believe it is in the Packard youtube that mention is made of the two Rolls-Royce engineers who came to Packard to work on the setup for Merlin production there. One of the two engineers quite literally worked himself to death.

The contention about the differences in how Packard built Merlin engines vs Rolls-Royce stems from working to a consistent system of tolerances. From what I have read and seen in the documentaries, Rolls-Royce tended to machine engine parts to within a reasonable range of accuracy. The parts were then individually measured and matched up to assemble engines. In some instances, the "fitters" lived up to their name in what it took to build an engine with parts made by Rolls-Royce's existing methods. Packard and Ford were used to mass production methods, and had consistent systems of tolerancing for their design drawings and to which parts were made.
It is also worth noting here that Henry Ford had early-on recognized the Johannsen Blocks (aka "Jo Blocks"), and had developed the production and use of Jo Blocks as a routine thing in Ford plants.

I also recall some discussion as to establishing "which inch" to work off of when establishing standards for measurements in building the Merlin engines. The inch standards vary very slightly from the US and Britain, something on the order of tenths of ten-thousandths of an inch, but it is significant enough to matter with the fine tolerances needed to build the Merlin engines.

Aside from all else, Henry Ford was an isolationist and wanted the US to remain neutral as far as involvement in WWII. Ford, himself, was an ardent supporter of Adolf Hitler and had been honored by the Nazi government. When the US government asked Ford to convert some of his plants to doing defense work, prior to our entry into WWII, and to manufacture war material for our allies, he refused. Supposedly, the US government told Henry Ford that if he did not conform to war production or defense plant corporation requirements, the US government would simply take over his plants. Ford backed down. Once the US entered WWII, Ford Motor began building all sorts of war material including the "Willow Run" bombers and Jeeps (GPW's I think, since Willys could not keep up with the orders).

I do not know how much of a hold or control Henry Ford had on the "Shadow Factory" at Trafford Park, since it was in England. With England involved in WWII long before the US entry, did the Trafford Park works start Merlin production before the US entry into WWII ?

Just this evening, I was talking with our son via phone. I've been asked to be an adviser/mentor to an engineering school's "Battlebots" team. All new to me. I told my son that visions of the Soviet T-34 tanks were dancing in my head when I had found out what "Battlebots" is all about. We discussed how the Soviets developed and produced the T-34 tanks, including relocating whole steel mills and heavy industrial plants to the Urals. My son ( a visionary and idealistic 31 year old law student) talked about the "nimble" soviet economy, good planning, etc. I reminded him first that Stalin simply ordered any available people and resources to get on dismantling, relocating, and setting up heavy industry away from danger, and to get busy and develop some good tanks. My son asked how the T-34 came to be, and I was telling him about how the Soviets cloned the 1930's 'Cat diesel tractors and likely had engineers from that factory group put on tank production. I also reminded him that Stalin ordered countless people to dismantle, move, re-build and operate heavy industrial facilities with horrific loss of life due to accidents, untrained workers, minimal equipment, overwork, starvation, cold, disease, and summary executions. Then, I threw the "zinger", telling my son that: Without the US to provide the machine tools to our allies, they could not have built much of their war material. I told my son how the US tooled up, took people who were either too old, unfit for military service, or women and trained them and got them going full-out on war production. We tooled , equipped, and armed our allies without forcibly relocating anyone or working anyone under conditions anything like what Stalin inflicted on the Soviet workforce. I also said that the US machine tool industry was the bedrock of the allied war effort. In watching the youtube of the Rolls Royce Merlin plant, there is a "Wickes Brothers- Saginaw, Michigan, USA" production milling machine shown in operation, as well as a Gleason gear inspection machine. I am sure if a person walked through that Rolls-Royce plant, they'd have found plenty of US made machine tools such as Cincinnati milling machines and Fellows and Gleason gear making machine tools in use.

The important thing is that we were in it together, and the USA stepped up to the plate, first by helping tool up our allies, then by furnishing war material including naval vessels and aircraft, and ultimately, be sending in our armed forces.

I know a Jeep is nowhere near the kind of machine that a Merlin engine is. However, my own exposure to WWII production happened when I got shanghaied into rebuilding the engine in a 1944 Willys MB Jeep. My wife and I had been married only a few months and were living in an apartment. Some fellows I knew let me store my motorcycle for winter in their building. One afternoon, as winter closed in, they called my wife and said their old Jeep, with which they plowed snow, would not start. They asked my wife to call me at work and ask if I would swing by their place to see what ailed their Jeep. The Jeep was beyond tired, and we pulled the cylinder head. It was obvious that the engine needed to have the cylinders bored and oversized pistons fitted. We rigged a chainfall and pulled the engine that night. The fellows did not want to pay an automotive rebuilder to reassemble the engine, so took it down to the bare block the next day. They took the block and crankshaft to the automotive rebuilder's machine shop. A week later, I got a call to put that Jeep engine back together. My bride helped me one cold Saturday morning. I decided to remove the ring gear from the flywheel and flip it around to get crisp and fresh corners on the gear teeth. I heated the ring gear, popped it off the flywheel and got it back on. As I looked at the flywheel and crankshaft, I saw the "Ford Oval" with the Ford script on both parts. The engine was clearly a Willys engine. The Jeep engine had been rebuilt once at Mechanicburg, PA Army Depot, so my guess is the Army's mechanics put it together with whatever used parts met specifications. I have always held that story in my mind, as to how Willys and Ford parts interchanged without problem on what was a Willys design. It would be a test to take a R-R/Trafford Park Merlin engine and a Packard built Merlin apart and see how parts interchanged and assembled.
 
As I looked at the flywheel and crankshaft, I saw the "Ford Oval" with the Ford script on both parts. The engine was clearly a Willys engine. The Jeep engine had been rebuilt once at Mechanicburg, PA Army Depot, so my guess is the Army's mechanics put it together with whatever used parts met specifications. I have always held that story in my mind, as to how Willys and Ford parts interchanged without problem on what was a Willys design. It would be a test to take a R-R/Trafford Park Merlin engine and a Packard built Merlin apart and see how parts interchanged and assembled.

Joe -

Now I was not around for WW2 as we are almost the same age. But I do know Army Depot Rebuild on assemblies like engines entails total tear down to the lowest component level - at least from 1970 when I was schooled on it. I'm guessing that all the engines were built to the same specs. So when reassembly time came it would be quite easy to have a mix of parts in any given engine - your story makes perfect sense to me. Your story brings back memories.

Then there was the other extreme. By the time Nam started heating up the old M-37 3/4 ton truck was getting long at the tooth (early 50s design/build) - Dodge built those, had the old reliable flat head 6. The geniuses decided to go 'commercial off the shelf' with a modified Jeep Gladiator that was the M-715 series, but what all of called the '5/4' as it was supposedly a 1 1/4 ton capacity vehicle. This was to be an 'interim' vehicle so the geniuses decided to save money and never bought any spare engines or major components like heads for the fleet. They used the standard Jeep engine - which was a 6 cylinder overhead cam with some serious design issues. The biggest of which was - if I remember correctly - an aluminum cam deck that was too soft, resulting in bearing failure. I reported into a maintenance company in November 1972 as a platoon leader down at Fort Hood, TX. We had something like 60 of these sitting on the lot with failed cam decks - and more being jobbed into us weekly. And no way to get parts - on order, but none available. The unit I was in provided Direct Support (figure dealership level service) to something like 59 units - we swapped out major components - engines, transmissions, injector pumps, clutch jobs, etc. By this time it was obvious the Army had a mess on their hands because of previous decisions - which I am sure were tied to trying to save money because of our 'guns and butter' way of running things in Nam. Solution was to have every unit like ours in the Army pull the bad engines, crate them up, ship to Red River Army Depot in Texarkana, TX for them to rebuild. Trouble was you ended up with all the miscellaneous parts that did not go with the engine - so we ended up filling up a couple of 30 foot trailers with all those parts. Usually you got a replacement engine in a 'can' - sealed shipping container - so the parts were on/off. I left active duty 24 June 1974 and the mess had only gotten worse and no engines returned. They even looked into buying more engines at some point - but new emission rules would not allow new build of the old design. A complete cluster.

The replacement for the M-715 became the M-880 series, which were Dodge pickup trucks and part of the 'saving' of Chrysler Corporation later in the 70s. And those are a whole other story and headache.

I much rather would have worked on the old Jeep engine you messed with! A good design that worked - like the small block Chevy I know very well.

Dale
 
There's a really interesting (to some) book on aircraft engines with the oddly specific title _Allied Aircraft Piston Engines of World War II_. It goes into detail about the development and production of the various aircraft engines and engine technology used during the war. I remember mention that the Ford Merlins could have parts swapped by mechanics in the field, while the Rolls Royce made Merlins had to have parts hand fittted to the engine they were being put on.
 
Aside from all else, Henry Ford was an isolationist and wanted the US to remain neutral as far as involvement in WWII. Ford, himself, was an ardent supporter of Adolf Hitler and had been honored by the Nazi government. When the US government asked Ford to convert some of his plants to doing defense work, prior to our entry into WWII, and to manufacture war material for our allies, he refused. Supposedly, the US government told Henry Ford that if he did not conform to war production or defense plant corporation requirements, the US government would simply take over his plants. Ford backed down. Once the US entered WWII, Ford Motor began building all sorts of war material including the "Willow Run" bombers and Jeeps (GPW's I think, since Willys could not keep up with the orders).

It wasn't the government per se that told HF that. It was Bill Knudsen, former head of Ford manufacturing. Read the great book "Freedoms Forge". Most amazing story about the second industrial revolution created by WW2.

Paul
 
Joe and Tom have described the fundamental difference between UK and US manufacturing philosophies.

Whilst the first true mass-production was the block-making machinery designed by Brunel and installed at Plymouth (UK) in 1803, much of British industry retained the selective-fitting concept.

In the US the long-established Springfield Armory made the first step toward mass production when Blanchard's tracer lathes were used in 1819 to produce rifle stocks.

The advantages of producing even wooden parts that were identical and did not require skilled labour soon led to more detailed investigations of more-complex parts such as rifle barrel, breech and trigger mechanisms and this led, to the delight of the military, to rifles with parts that were completely interchangeable, without special tools and in the field.

We regard this as normal today but it was a new concept almost 200 years ago.

Meanwhile, in the UK, arms makers wanted to retain their ancient system of piece-work, which was very useful in keeping wages down, putting the onus on the worker to produce the required number of parts and, by means of different payment systems for different crafts, effectively hiding the earnings of one worker from another.

They scornfully dismissed the US mass-production philosophy as inferior and coined the phrase "British craftsmanship" to cover up their own inferiority.

The shortcomings of the British philosophy were really exposed by WW2 and I recommend Blood, Tears and Folly (Len Deighton) for a detailed description of the problems faced by British military with inadequate weapons while US soldiers enjoyed weapons that were effective and easily-repaired.

Understanding these different nation approaches to manufacturing engineering explains the RR/Ford differences regarding the Merlin; RR was using "British craftsmanship" which involved bins of different engine parts and the selection of various combinations to achieve the specified tolerance.

Ford engineers just made the parts properly in the first place.
 
It is a great mystery then, how Rolls-Royce in Britain managed to manufacture over 82,000 Merlins (with constant development and the curse of introducing improved models while increasing production), 8,000-odd Griffons, not to mention develop the jet engine, a two-stroke V-12, tanks and tank engines, armaments, repair bomb damage to factories...all done by chaps in brown coats, at workbenches with hand files and bins of roughly-made parts.

Ford in Manchester produced 30,428 and Packard turned out 55,523 using their wonderful drawings and improved methods and not too many model changes to worry about.

I have heard that Packard laid their parts on felt-covered surfaces, while the Brits whacked them down onto steel benches, this accounted for a measurable increase in Packard-Merlin horsepower....

It's all a load of bollocks of course, and these stories of Packard & Ford superiority are repeated fondly every time the subject comes up.

Please stop, none of them are true.
 
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They scornfully dismissed the US mass-production philosophy as inferior and coined the phrase "British craftsmanship" to cover up their own inferiority.

That reminds me of the bumper sticker seen on a Triumph:
"The parts falling off this car are of the finest British manufacture".

Steve
 
Nothing "British craftsman" about selective assembly whatsoever- simply a method that worked very well.
The method was commonplace at the time in precision industries; the best example being the German optical industries; ie. Zeiss Ikon, Leica etc. No "fitting" as such, simply hand assembling classed parts made to close tolerances into working mechanisms.

Much like ball and roller bearings are made today:D
 
I have been a keen student of Merlins and have substantial files of information on them.

Nowhere in my Merlin files is any claim or statement that Merlins from one plant were better than those from any other and I have never thought or said so.

I have given references for my indirect quotes by Sir Stanley Hooker and Len Deighton; neither carry any inference that one Merlin was better than another of the same Mark.

The situation was that British and US engineering philosophies at the time worked fine separately but did not easily co-exist when required to do so by the exigencies of war production, hence Hooker's wry story of the Ford drawings.

RR continued to build Merlins in the "Rolls-Royce way" and Ford built Merlins in the "Ford way"; both engines performed to strict specification.

Deighton (a highly-respected military historian) is scathing in his comments on how the inefficiency of the British system let-down the fighting troops; Rolls-Royce were (and remain) undoubtedly one of the world's great engineering firms but it's necessary to examine the origins of "British craftsmanship" to understand how and why their philosophy and that of US firms did not dovetail neatly.

Blood, Tears & Folly is cheaply available and is, again, highly recommended.

All the factories that produced Merlins built very good ones, in accordance with the high engineering skills possessed by each factory/company;

We have to accept the earlier view of Geoffrey Chaucer that "... diverse pathes leden diverse folk the righte way to Rome."
 
Wonderful thread.
Perhaps it has always been so but I find it remarkable how this accomplishment illustrates the organizational structures which must exist behind the pointy end in order to prevail when nations go to war.
 
Wonderful thread.
Perhaps it has always been so but I find it remarkable how this accomplishment illustrates the organizational structures which must exist behind the pointy end in order to prevail when nations go to war.

Recently there's been a series on TV over here called " War Factories " that had gone in to this subject. It's been very interesting although somewhat slanted in my opinion. All the commentators are from the right wing of the argument.

Regards Tyrone.
 
I’d learned to avoid looking at Merlin threads, for the sake of my blood pressure. However, I saw some respected members’ names popping up, so I’ll chip in.

Most of us on this forum know something about machining, or about rebuilding engines. With that knowledge, a little reflection will surely raise questions about some of the statements that are commonly made whenever this topic crops up.

Take the question of tolerances. It may be that when R-R were producing small numbers of engines with skilled craftsmen, they could be more relaxed about specifying tolerances. However, as Peter S points out, R-R produced 82,000 Merlins, plus other engines. They also had components manufactured for them by outside firms, such as De Havilland, Alvis, Sunbeam. They also overhauled huge numbers, and produced guns as well. They did this in several large factories, some of which started with large contingents of inexperienced labour. They all had to produce precision parts which gave the correct interference fits, small running clearances, correct gear meshing, etc, and these parts had to pass inspection, by direct measurement or go/no go gauges, whether this be in-house or by the resident Aircraft Inspection Board inspectors.

Next observation: It is sometimes said that Ford and/or Packard were accustomed to working with tighter tolerances. I have very little information on the tolerances used by Rolls-Royce or the others. I do have before me a 1940 R-R drawing of a Merlin component, and two of the diameters used for location have tolerances of +0, -0.00025” (actually written as -1/4). Less critical dimensions (axial lengths} have appropriate tolerances such as [+0.002”, -0], [+/- 0.005] etc. There’s a fillet radius of 0.040” -0.010”. Now, assuming these are typical, I'd be interested to know why another manufacturer would consider it necessary or advantageous to tighten up on any of these tolerances?

Then we have the vision of mechanics in the field ‘hand fitting’ replacement components on R-R Merlins. I’d be intrigued to know what parts of a highly-rated Merlin could be safely made the right size by filing, or whatever. Presumably not the crankshaft, con rods, camshaft, valves, pistons, bearings, or any of the 70-odd gears. On the other hand I can envisage stock parts being selected for fitting during overhaul. I've done the same myself, thinking it unwise to fit new standard size bearings to a reground crankshaft!

Rolls-Royce overhauled thousands of Merlins, keeping the designers busy with approved schemes for replacing or salvaging expensive components, and having the shops produce the replacement parts. For example, something simple like replacement case-hardened drive pins for magneto drives were held in three oversizes, in increments of 0.010”; diameter +0, -0.00025. (Example specification given in ‘The Merlin in Perspective – the combat years’ by Alec Harvey-Bailey, Rolls-Royce Heritage Trust, 2003).
 
Good stuff there, Asquith. It’s nice to hear some actual callouts from original documents. I think there is naturally going to be rivalry in competing “teams” and anecdotes will tend to be repeated and exaggerated by the interested parties, It becomes part of the story, that’s human nature.

Let’s not forget the big picture, the amazing accomplishment of the Women and men who cranked out the huge numbers of these engines.

On another note, I’d be really interested in exactly how the power of the engines was doubled (or more). Was it due to advances in metallurgy, production engineering, testing and inspection? I’d imagine plenty of opportunity to “run until failure” as well. Likely all of the above and more, what book covers that aspect best?
 
Cyanidekid - Good questions.

100-octane fuel from the USA provided the essential foundation for the performance increase. This New York Times article provides some interesting background:-

Who Helped Win Battle of Britain - The New York Times

This makes a nice succinct newspaper story, but inevitably only hints at the bigger picture. Alec Harvey-Bailey points out that switching from 87 to 100 octane and increasing the supercharged boost raised the power output from 1000 to 1300 HP at 8000-9000 ft, but the advantage was lost at higher altitudes. The majority of fighting was done at 18,000 ft and higher, where the higher octane fuel gave no benefit. Considerable work was needed to produce blended fuels and to improve supercharger design and power transmission to the superchargers, etc, etc.

An article by Francis Rodwell (Rod) Banks hints at the efforts on the fuel side:-

http://www.wwiiaircraftperformance.org/100-octane/banks-fuel.pdf

Banks was an IC engine fuel/combustion expert, who developed fuels for various world record attempts before the war. He was appointed an Air Commodore for the duration

Stanley Hooker (mentioned earlier by Plannerpower) led the way in transforming the supercharger design at Rolls-Royce.

Then the story gets complicated. Years ago I read a fascinating book which recounted the progressive development of the Merlin to keep one step ahead of the Luftwaffe, but I’ve failed to track it down.

As the design was progressively altered to increase power, testing to destruction was used to find the weaknesses, as cyanidekid says. Obviously this had its limitations compared with in-flight behaviour. Moreover, application of the engine in different types of aircraft gave different problems, requiring quick solutions.

The best information, warts and all, comes from the Rolls-Royce Heritage books, written mostly by engineers who were directly involved. However, I don't think any of them give a full picture of how the power output was progressively increased. From memory, The Power to Fly by L J K Setright does give a good account of the developments.

'The Merlin in Perspective – the combat years' by Alec Harvey-Bailey, Rolls-Royce Heritage Trust, 2003) provides fascinating information about design, production, failures, etc, but only has 90 pages of text, the rest of the 210 pages being photos and tables

'Rolls-Royce Piston Aero Engines – a designer remembers' by A A Rubbra, RRHT, 1990, covers the development of various R-R piston aero engines, packed with drawings and photos.

'Rolls-Royce and the Mustang' by David Birch, RRHT 1987/1997 gives a fascinating insight into the challenges of matching engine and airframe.

If I get chance I'll post some more information.
 








 
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