# Bad Steel in the Rolls-Royce Merlin?



## SKR_01 (Sep 12, 2017)

Hi people!
I had a dispute with a friend: he claims that Merlin had poor-quality steel. I know that RR used the mark steel KE.965 for valves, but I do not know how this circumstance is with this industry.
If there are people here who are familiar with Merlin or how good is British steel in the 30s and 40s?
Sorry for my English.


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## bobbysocks (Sep 12, 2017)

seemed to be a pretty reliable engine for supposedly having been made of poor steel... I have never read of pilots not trusting the engine or massive accounts to blowing the engine because they ran it too hard.


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## fubar57 (Sep 12, 2017)

Western engine reliability


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## pbehn (Sep 12, 2017)

SKR_01 said:


> Hi people!
> I had a dispute with a friend: he claims that Merlin had poor-quality steel. I know that RR used the mark steel KE.965 for valves, but I do not know how this circumstance is with this industry.
> If there are people here who are familiar with Merlin or how good is British steel in the 30s and 40s?
> Sorry for my English.


As a retired metallurgist (of sorts) the term "bad steel" is not applicable. There are dozens of different metals in an engine and not all are steels. There are discussions you can read here about the Allison being more reliable than the Merlin but that is by degrees, the Merlin was extensively tested and used on British (UK) and US aircraft from the start to the end of the war.

In a theoretical case, if a big end seizes due to poor lubrication then the con rod may snap, that is not a sign of bad steel but poor design or servicing.

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## SKR_01 (Sep 13, 2017)

Tell me, what methods of steel production were in the 30's and 40's in Britain?


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## pbehn (Sep 13, 2017)

SKR_01 said:


> Tell me, what methods of steel production were in the 30's and 40's in Britain?


The subject is tied up in language that confuses most. Steel is an alloy of Iron and Carbon. However when you produce Iron using coke for heat it has a high carbon content. Refining steel from this "Iron" from a blast furnace involves reducing the amount of carbon not increasing it. Most Steel in UK at the time was refined using the Bessemer process or open hearth process, the Basic Oxygen steel process was developed in the post war period,


Blast furnace - Wikipedia
Bessemer process - Wikipedia
Open hearth furnace - Wikipedia
Basic oxygen steelmaking - Wikipedia


However the process is a small part of the story, the real problems are in testing. I started work in 1977 and was trained in chemical analysis by wet methods. It took two people a whole day to test forty samples for all elements, now it takes a few seconds per sample. In heat treatment I met old guys who could tell the temperature of molten and solid steel with their eyes. In heat treatment temperature is vitally important but how could you measure it to nine hundred and ten plus minus five celcius in 1940? Similarly, ultrasonics didn't exist and radiography was primitive, how do you test for internal defects? The problems were not really in production but in quality control and quality assurance. 

At the time the biggest metallurgical problems were in jet engines, The UK at the time was the equal of the USA in this field. Germany had different problems because they couldn't get expensive and rare alloy elements but came up with passable solutions despite this.


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## pbehn (Sep 13, 2017)

bobbysocks said:


> seemed to be a pretty reliable engine for supposedly having been made of poor steel... I have never read of pilots not trusting the engine or massive accounts to blowing the engine because they ran it too hard.


If you did this would more likely be a problem of oil feed, oil type or bearing quality. Various "dodges" like tuftriding and ball peening increased the service life of engine parts but this is not really a question of "bad steel". Some manufacturers have had problems in the past with things like valves and rings for example, this is usually poor heat treatment not the steel itself.

In my youth Honda had a problem with their 900cc engines breaking con rods when used for racing. The solution was to use a smaller not bigger "big end" housing. The smaller connecting rod being lighter put less load on the crank and bearings. Any layman would blame the steel used in the engine when in fact the problem was the engine design itself.

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## pbehn (Sep 13, 2017)

SKR_01 said:


> Hi people!
> I had a dispute with a friend: he claims that Merlin had poor-quality steel. I know that RR used the mark steel KE.965 for valves, but I do not know how this circumstance is with this industry.



KE 965 was developed by Kayser Ellison and co in 1937

C= 0.4 Cr =13 Ni =13 Si -1.5
UTS = 156,000PSI, elongation 27% reduction in area 49% Brinell hardness 265. Heat treated
Non distorting for valves and supercharger buckets.

"Developed to replace EN52 as an exhaust grade steel, this steel possesses excellent creep strength and impact values at high temperature, and has good scaling and corrosion resistance, except in the presence of sulphur, and its resistance to oxidation extends to temperatures above 900 Deg. C. "

"Creep" is the elongation of materials at high temperatures under low load over a long period of time..

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## yulzari (Sep 14, 2017)

pbehn said:


> In my youth Honda had a problem with their 900cc engines breaking con rods when used for racing. The solution was to use a smaller not bigger "big end" housing. The smaller connecting rod being lighter put less load on the crank and bearings. Any layman would blame the steel used in the engine when in fact the problem was the engine design itself.


Very good Pbehn. We found the same thing with Chevrolet V8s in Formula 5000 engines. The smaller diameter cranks pins had a slower speed over the bearing surface and the oil could cope better. The steel was of little significance.

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## pbehn (Sep 14, 2017)

yulzari said:


> Very good Pbehn. We found the same thing with Chevrolet V8s in Formula 5000 engines. The smaller diameter cranks pins had a slower speed over the bearing surface and the oil could cope better. The steel was of little significance.


I used to read quite a lot on stuff like tuning the Ducatis for Hike Hailwoods comeback. Many of the solutions were like the one you describe, counter to what appears logical to the lay man. That is because I am a lay man and not an engineer. The Rolls Royce Merlin was one of the oldest designs of front line WW2 in line water cooled engines, it also had one of the smallest swept volumes. Despite this the last versions were over 2000 BHP. If it had any serious reliability issues it would not have been the engine in the P51, you cannot send hundreds of single engine fighters on six hour missions over enemy territory with dodgy engines.

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## fastmongrel (Sep 16, 2017)

Possibly things have got confused between the RR Merlin aero engine and the Meteor tank engine which was mostly developed by Rover. The Meteor had around about 75% parts common with the Merlin and used some parts that had not managed to pass tests for air use. A broken valve spring over Germany can mean a bail out, a broken valve spring in a tank means burning oil till you can get out of the combat zone and then a few hours fitting a new engine. Meteors also used parts from RR and Packard Merlin engines that had exceeded the hours allowed for air use or had gone out of tolerance.

RR used the "rev it till something breaks and then work out why it broke and how it can be strengthened" testing method. The residents of Derby must have spent many hours with their fingers in their ears as the latest V12 was run to destruction in the test bays.

Many RR developed Ferrous and Non Ferrous alloys were used for many years as industry standards in the UK so I doubt that RR who could have had any materials they wanted from the UK and US would have used inferior steels.

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## pbehn (Sep 16, 2017)

fastmongrel said:


> Possibly things have got confused between the RR Merlin aero engine and the Meteor tank engine which was mostly developed by Rover. .


The original post was from a guy in Russia, the Merlin may have a different reputation there, but that may be due to operating conditions or different fuels and lubricants.

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## swampyankee (Sep 16, 2017)

pbehn said:


> Various "dodges" like tuftriding and ball peening increased the service life of engine parts but this is not really a question of "bad steel".



Shot peening and ball [hammer] peening are very useful processes for improving fatigue resistance, as they induce compressive residual stresses near the surface; I'd not call them dodges, even in scare quotes 

I suspect that a thorough and accurate multi-national comparison of steel (and other alloy) quality from the WW2 era and before is impossible, for several reasons, first of which is that "quality" in this context doesn't mean "better," but consistent, so one would need at least dozens of test reports for each alloy, each vendor, and each type of process hot rolled, cold rolled, cast, stamped, different heat treatments, .... and that the ways these data are reported differ between countries, _e.g._, Germany and the US used different methods of reporting elongation.


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## pbehn (Sep 16, 2017)

swampyankee said:


> Shot peening and ball [hammer] peening are very useful processes for improving fatigue resistance, as they induce compressive residual stresses near the surface; I'd not call them dodges, even in scare quotes
> 
> I suspect that a thorough and accurate multi-national comparison of steel (and other alloy) quality from the WW2 era and before is impossible, for several reasons, first of which is that "quality" in this context doesn't mean "better," but consistent, so one would need at least dozens of test reports for each alloy, each vendor, and each type of process hot rolled, cold rolled, cast, stamped, different heat treatments, .... and that the ways these data are reported differ between countries, _e.g._, Germany and the US used different methods of reporting elongation.


I agree Swampyankee,it is always difficult to choose the language. What I meant by a "dodge" was a method to increase the serviceability of a component without changing the other basic production process. In the Merlin the pistons are Aluminium alloy, the big end beaings are lead bronze, the little ends are phosphor bronze, the con rods are nickel steel forgings, the crankshaft is a Ni Cr Mo steel hardened with nitrogen while the crank cases are Aluminium. The critical parts are either not steel at all or completely out with what people regard as "steel". I have worked with stainless "steels" where Iron is quoted as "balance" and Carbon is less than 0.03% even though steel is supposed to be an Iron Carbon alloy. They are actually Cr Ni Mo Fe alloys but "steel" is a convenient collective word.


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## swampyankee (Sep 16, 2017)

pbehn said:


> I agree Swampyankee,it is always difficult to choose the language. What I meant by a "dodge" was a method to increase the serviceability of a component without changing the other basic production process. In the Merlin the pistons are Aluminium alloy, the big end beaings are lead bronze, the little ends are phosphor bronze, the con rods are nickel steel forgings, the crankshaft is a Ni Cr Mo steel hardened with nitrogen while the crank cases are Aluminium. The critical parts are either not steel at all or completely out with what people regard as "steel". I have worked with stainless "steels" where Iron is quoted as "balance" and Carbon is less than 0.03% even though steel is supposed to be an Iron Carbon alloy. They are actually Cr Ni Mo Fe alloys but "steel" is a convenient collective word.



When I worked in aerospace, there was one part where they changed the process, from air melt to vacuum melt, with absolutely no other process changes. The part went from severely life-limited (recommended replacement interval less than 500 flight hours) to unlimited: same part, same heat treat, same testing specs, same loads.


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## pbehn (Sep 16, 2017)

swampyankee said:


> When I worked in aerospace, there was one part where they changed the process, from air melt to vacuum melt, with absolutely no other process changes. The part went from severely life-limited (recommended replacement interval less than 500 flight hours) to unlimited: same part, same heat treat, same testing specs, same loads.


You do not have to go to aerospace applications or even to vacuum melting, good de gassing procedures on normal carbon steels lift Charpy (CV 10) impact values from 250/300 to 500+.Joules But the level of this discussion illustrates my point, what is a good or a bad steel depends entirely on what you want. The part you were quoting is not "bad" when produced by air melt method, it is just not as good as what replaced it, that is engineering and metallurgy..


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## swampyankee (Sep 16, 2017)

pbehn said:


> You do not have to go to aerospace applications or even to vacuum melting, good de gassing procedures on normal carbon steels lift Charpy (CV 10) impact values from 250/300 to 500+.Joules But the level of this discussion illustrates my point, what is a good or a bad steel depends entirely on what you want. The part you were quoting is not "bad" when produced by air melt method, it is just not as good as what replaced it, that is engineering and metallurgy..



My only metals-related experience is when I did structural test (mostly fatigue testing) before I moved to aerodynamics; I prefer my anecdotes to be personal.


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## pbehn (Sep 16, 2017)

swampyankee said:


> My only metals-related experience is when I did structural test (mostly fatigue testing) before I moved to aerodynamics; I prefer my anecdotes to be personal.


Me too, and I appreciate it. The discussion hinges around "bad" steel. Having worked on steels for 35 years the term is not applicable. You have a steel that is acceptable to the specification or "fit for purpose" or it isn't. Basically you cannot say a crankshaft is good steel and so melt it down and make con rods and valves out of it.


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## bobbysocks (Sep 17, 2017)

pbehn said:


> If you did this would more likely be a problem of oil feed, oil type or bearing quality. Various "dodges" like tuftriding and ball peening increased the service life of engine parts but this is not really a question of "bad steel". Some manufacturers have had problems in the past with things like valves and rings for example, this is usually poor heat treatment not the steel itself.
> 
> In my youth Honda had a problem with their 900cc engines breaking con rods when used for racing. The solution was to use a smaller not bigger "big end" housing. The smaller connecting rod being lighter put less load on the crank and bearings. Any layman would blame the steel used in the engine when in fact the problem was the engine design itself.



I agree. the problems would be more related to the lubrication in regards to the crank, cams, rings, and the parts of the engine that are related to them. the other aspect would be insufficient cooling....one part of the engine retaining too much heat and causing warpage or fracture. but both of those are engineering issues and not the steel, iron, metal itself. 

bad metal would result in fracturing with sufficient cooling....excessive cylinder, valve guide, etc wear with sufficient lube....

the only problems I can recall were valve and valve seat issues, and sparkplug leading/fouling. others may and probably do have more info than i.


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## swampyankee (Sep 17, 2017)

pbehn said:


> Me too, and I appreciate it. The discussion hinges around "bad" steel. Having worked on steels for 35 years the term is not applicable. You have a steel that is acceptable to the specification or "fit for purpose" or it isn't. Basically you cannot say a crankshaft is good steel and so melt it down and make con rods and valves out of it.



My point is that changes in processing can make a material (not just steel) suitable or not. I don't know what Rolls Royce's quality control methods were for materials and I don't know what kind of quality control checks they had during processing, nor the degree that these checks were enforced in subcontractors. I can only presume they were adequate for the design and within normal practice for aircraft manufacture at the time.


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## pbehn (Sep 18, 2017)

swampyankee said:


> My point is that changes in processing can make a material (not just steel) suitable or not. .



Very true SY, this is a process that has been going on since metals were first melted. In my last years at work people discussed the effects of dissolved nitrogen in steel, in my early years there was no way of testing for it in a steel plant. 

An engine goes through various phases of development. Sometimes huge power outputs are quoted for an engine on a test bed. However these are engines run for a short time and assembled under perfect conditions using specially selected and machined parts. To get this engine to a mass produced engine that will hold together in service for hundreds of hours is what takes the time and explains why the maximum produced on a bench is much more than that produced in service. Engineers design around what they have, they may request manufacturers to improve some aspect of what they supply but that is research for the future. In practice, from my experience the manufacturers write the specification which is approved by major clients. This is how a company called Kayser Ellison produce a material standard for high performance exhaust valve steel used only by companies like Rolls Royce.


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## MycroftHolmes (Oct 1, 2017)

R A Gould's work suggested the opposite: that the steel used in RR Merlins was of better quality than that in Packard-made engines. He noted that when crashed aircraft powered by RR engines were excavated the engines were in much better shape than similarly-recovered Packards, due to impurities in the steel used in the American-built engines. I imagine though that aircraft in WWII had such short lives that this made little practical difference.


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## Shortround6 (Oct 1, 2017)

A strange way to judge steel. What was important at the time was strength and resistance to fatigue. Which might very well call for a different alloy than resistance to corrosion. Steel parts that corroded in service were probably not getting enough oil.

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## pbehn (Oct 1, 2017)

Shortround6 said:


> A strange way to judge steel. What was important at the time was strength and resistance to fatigue. Which might very well call for a different alloy than resistance to corrosion. Steel parts that corroded in service were probably not getting enough oil.


It is no reason at all to make a judgement. Pure normalised iron corrodes quite slowly. In a welded pipe the weld will corrode more quickly than the pipe despite being much cleaner as regards impurities. The weld is a coarse grained structure. However the place that corrodes most is the toe of the weld because the weld and parent metal are different and set up a small galvanic cell.

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## swampyankee (Oct 1, 2017)

When I took my metals class in college, the textbook mentioned that if one took a rubber band, wrapped it around a stainless steel tube, dropped it into tap water, and waited a couple of weeks, the rubber band would cut through the steel.


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## pbehn (Oct 1, 2017)

swampyankee said:


> When I took my metals class in college, the textbook mentioned that if one took a rubber band, wrapped it around a stainless steel tube, dropped it into tap water, and waited a couple of weeks, the rubber band would cut through the steel.


I dont know if that is true or not swampyankee, what is true is that there are a huge number of different types of steel especially stainless steels many of which will rust. All sorts of things can happen, I have seen a hole burrowed into a 2 inch thick carbon steel flange in three months purely by turbulence in the oil and galvanic action.


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## swampyankee (Oct 1, 2017)

pbehn said:


> I dont know if that is true or not swampyankee, what is true is that there are a huge number of different types of steel especially stainless steels many of which will rust. All sorts of things can happen, I have seen a hole burrowed into a 2 inch thick carbon steel flange in three months purely by turbulence in the oil and galvanic action.



Even if the book mentioned the variety of CRES, I got rid of the book years ago and couldn't tell you the alloy to save my life.The book did say to try it.


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## pbehn (Oct 1, 2017)

swampyankee said:


> Even if the book mentioned the variety of CRES, I got rid of the book years ago and couldn't tell you the alloy to save my life.The book did say to try it.


I wasn't doubting it SY I just havnt heard that specific example. Having worked in a stainless steel pipe factory for years, the most dangerous things to most stainless steels are plain carbon steel and salt water. The most expensive pipes I ever inspected were SS625 on the inside, X65 carbon steel as the "pipe" (for engineering strength) and a Monel coating. The splash zone on an oil rig is one of the most corrosive environments found anywhere and stainless steel just isn't good enough. Monel is an alloy of Nickel and Copper but that isn't a cure all for corrosion, a guy once built a boat with a Monel hull and it fell apart in six weeks, galvanic action ate the rest of the boat.


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## SKR_01 (Oct 3, 2017)

pbehn said:


> The original post was from a guy in Russia, the Merlin may have a different reputation there, but that may be due to operating conditions or different fuels and lubricants.


in general, I read about the use of Merlin in the Hurricane in the USSR and most of the claiming boiled down to a carburetor that was not suitable for frosts at -25 ° C


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## pbehn (Oct 3, 2017)

SKR_01 said:


> in general, I read about the use of Merlin in the Hurricane in the USSR and most of the claiming boiled down to a carburetor that was not suitable for frosts at -25 ° C


That is colder than any temperature I have experienced in UK.


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## SKR_01 (Oct 3, 2017)

pbehn said:


> That is colder than any temperature I have experienced in UK.


In the winter of 1942 near Stalingrad it was even colder) The water left in the carburettors froze and made the carburetors crack. By the way, I also learned that in the USSR the hurricane was reworked for flights on ordinary water, rather than ethylene glycol


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## pbehn (Oct 3, 2017)

SKR_01 said:


> In the winter of 1942 near Stalingrad it was even colder) The water left in the carburettors froze and made the carburetors crack. By the way, I also learned that in the USSR the hurricane was reworked for flights on ordinary water, rather than ethylene glycol


I worked in Russia (Vyksa) for a while, it is much colder than UK. However water entrapment isn't issue of bad steel. I believe the RAF used a water/glycol mix later in the war on safety grounds.


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## SKR_01 (Oct 4, 2017)

pbehn said:


> I worked in Russia (Vyksa) for a while, it is much colder than UK. However water entrapment isn't issue of bad steel. I believe the RAF used a water/glycol mix later in the war on safety grounds.


I know how cold in Russia. In my opinion, winter in Russia is the most pleasant and interesting time of the year. 
Water in the carburetor is a common phenomenon and all have suffered as a disease as engines, including the USSR.


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## pbehn (Oct 4, 2017)

SKR_01 said:


> I know how cold in Russia. In my opinion, winter in Russia is the most pleasant and interesting time of the year.
> Water in the carburetor is a common phenomenon and all have suffered as a disease as engines, including the USSR.


There is no reason that a solution couldn't be found apart from the huge distance between the front in USSR and Rolls Royce in UK. I cant remember Winston and Uncle Joe discussing carburettors much.

A Russian winter is much more pleasant than one in UK, snow at -20C is snow, at 0C it is cold water and the wind blows it everywhere.


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## Bollock brain (Oct 4, 2017)

pbehn said:


> Very true SY, this is a process that has been going on since metals were first melted. In my last years at work people discussed the effects of dissolved nitrogen in steel, in my early years there was no way of testing for it in a steel plant.
> 
> An engine goes through various phases of development. Sometimes huge power outputs are quoted for an engine on a test bed. However these are engines run for a short time and assembled under perfect conditions using specially selected and machined parts. To get this engine to a mass produced engine that will hold together in service for hundreds of hours is what takes the time and explains why the maximum produced on a bench is much more than that produced in service. Engineers design around what they have, they may request manufacturers to improve some aspect of what they supply but that is research for the future. In practice, from my experience the manufacturers write the specification which is approved by major clients. This is how a company called Kayser Ellison produce a material standard for high performance exhaust valve steel used only by companies like Rolls Royce.



Great stuff. So nerdy but fantastic , I am learning lots of things and have a whole new aspect of WW11 to annoy my wife with, which is wonderful theraphy.

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## pbehn (Oct 4, 2017)

Bollock brain said:


> Great stuff. So nerdy but fantastic , I am learning lots of things and have a whole new aspect of WW11 to annoy my wife with, which is wonderful theraphy.


Not really nerdy, it is engineering and the same applies in the modern world. The "floor plan" of a Volkswagon car costs much more to design and develop than a Rolls Royce car. However when completed it is the base of a range for all VW Audi Skoda and Seat vehicles whose production runs to millions. I don't know how much an exhaust valve weighs, but I doubt that all the Merlin exhaust valves ever made weigh more than a few tons, this is why military equipment costs a fortune.


I worked most to API 5L specification for pipes, which is American and written in English however the revisions for clad pipe API 5LD have some Germanic phraseology because it has lifted some technical statements from a German company. Even the American Petroleum institute cannot specify something that a manufacturer cannot make.


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## bobbysocks (Oct 4, 2017)

SKR_01 said:


> In the winter of 1942 near Stalingrad it was even colder) The water left in the carburettors froze and made the carburetors crack. By the way, I also learned that in the USSR the hurricane was reworked for flights on ordinary water, rather than ethylene glycol



i would like to see some reports or documentation about that. if a carb ices up in flight it doesn't crack and they can ice up to nearly closed. i don't understand why it would that if the ac was sitting....unless there was water in the fuel...which came from contaminated fuel and not the humidity of the air. not saying it didn't happen but this is the first i have heard of it.


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## SKR_01 (Oct 5, 2017)

bobbysocks said:


> i would like to see some reports or documentation about that. if a carb ices up in flight it doesn't crack and they can ice up to nearly closed. i don't understand why it would that if the ac was sitting....unless there was water in the fuel...which came from contaminated fuel and not the humidity of the air. not saying it didn't happen but this is the first i have heard of it.


VLVMA СПРАВОЧНИК ПО АВИАЦИОННЫМ МОТОРАМ 1943.djvu


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## rodg (Oct 9, 2017)

Re shot peening. I think that the idea was to eliminate scratches due to machining, in stressed areas. Even grinding and buffing leaves scratches which could seed fractures. As an aside, I used to work for Thornycroft lorry building division. We made the Antar, much used as a tank transporter and the largest lorry built in Britain. That , and two of the smaller lorries used by the military used the Meteor engine. And very nice it sounded too. During the War, they too, made the Merlin rocker/camshaft brackets. When I started there, there were still boxes of the brackets littering the machine shops

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## pbehn (Oct 9, 2017)

rodg said:


> Re shot peening. I think that the idea was to eliminate scratches due to machining, in stressed areas. Even grinding and buffing leaves scratches which could seed fractures.



The mechanics of shot (ball) peening are complicated, from wiki.

"Peening a surface spreads it plastically, causing changes in the mechanical properties of the surface. Its main application is to avoid the propagation of microcracks from a surface. Such cracks do not propagate in a material that is under a compressive stress; shot peening can create such a stress in the surface.[3]

Shot peening is often called for in aircraft repairs to relieve tensile stresses built up in the grinding process and replace them with beneficial compressive stresses. Depending on the part geometry, part material, shot material, shot quality, shot intensity, and shot coverage, shot peening can increase fatigue life up to 1000%.[2]

Plastic deformation induces a residual compressive stress in a peened surface, along with tensile stress in the interior. Surface compressive stresses confer resistance to metal fatigue and to some forms of stress corrosion.[1] The tensile stresses deep in the part are not as problematic as tensile stresses on the surface because cracks are less likely to start in the in the interior."


It goes on and gets more complicated but that gives the basic idea.

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## bobbysocks (Oct 9, 2017)

SKR_01 said:


> VLVMA СПРАВОЧНИК ПО АВИАЦИОННЫМ МОТОРАМ 1943.djvu



cool! thanks....I will look at it when I get off of work.


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## grumpos (Oct 9, 2017)

The late Alex Henshaw wrote a good article about Merlin failures some years ago. Apparently skew gears could fail, causing the engine to cut out in flight. He experienced this several times. There was also a problem with the US built Merlins where metal parts were were weakened during the manufacturing process. Exactly how, I cannot remember, but it involved contamination. Once the problem was identified, it was fixed. The article was in two or three parts in Aeroplane Monthly quite a few years ago. I'm sure that one of the Rolls Royce Heritage Trust booklets will have further information about this topic.


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## pbehn (Oct 9, 2017)

grumpos said:


> There was also a problem with the US built Merlins where metal parts were were weakened during the manufacturing process. Exactly how, I cannot remember, but it involved contamination. Once the problem was identified, it was fixed. .


There were many problems with the Packard Merlins and I am sure hundreds more that never got outside the factory. Setting up a plant to produce someone elses engine is a huge and very difficult undertaking. To find out Rolls Royce problems you would have to go back through all the problems in development of the Merlin and its predecessors. Both versions were excellent engines and both were operated by USA and UK in service. The differences amount to no more than quirks. 

One thing that really pushes my buttons is the popular notion that Rolls Royce hand produced their engines while Packard were proper mass producers. The original orders for Spitfires Hurricanes and Battles were for hundreds not thousands of aircraft. If the Vulture Sabre and Typhoon had developed as hoped and Adolf delayed the war by a year then the Merlin would be viewed as an interesting pre war design of which a few thousand were produced. Apart from the Spitfire and Hurricane none of the big users of Merlins were supposed to have them, Lancaster Halifax and Mustang were designed for other engines while the Mosquito wasn't designed until after the outbreak of war. The US government and Packard would not get involved in building huge facilities to produce a few thousand engines over 4 years.

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## Shortround6 (Oct 9, 2017)

pbehn said:


> One thing that really pushes my buttons is the popular notion that Rolls Royce hand produced their engines while Packard were proper mass producers. The original orders for Spitfires Hurricanes and Battles were for hundreds not thousands of aircraft. If the Vulture Sabre and Typhoon had developed as hoped and Adolf delayed the war by a year then the Merlin would be viewed as an interesting pre war design of which a few thousand were produced. Apart from the Spitfire and Hurricane none of the big users of Merlins were supposed to have them, Lancaster Halifax and Mustang were designed for other engines while the Mosquito wasn't designed until after the outbreak of war. The US government and Packard would not get involved in building huge facilities to produce a few thousand engines over 4 years.



The Merlin would have been an important engine no matter what. The Sabre was too big for many airframes and too expensive. 
The US certainly built plenty of R-1820s, R-1830s, R-2600s and V-1710s in addition to the R-2800s and R-3350s.

The Mercury, Pegasus, and Taurus were too small. Which pretty much leaves the Merlin and Hercules. 

The real thing that saved the Merlin was better gasoline. Had the British been limited to fuel that would only support 12-15lbs of boost the Merlin would have seen much less use near the end of the war. 

For some reason people want to believe that "their" nation built better engines or somebody else built lousy ones and will repeat any rumor that supports their position. 

However as far as Rolls Royce hand producing their engines, it was much more a question of had selecting rather than had fitting.
Engine assemblers didn't "file" parts to fit. They simply sorted through a bin of parts (even if the parts were separated or cushioned and not banging into each other) and sorted out the number of parts they needed that would fit _without hacking at them with hand tools! _
AS in measuring piston diameter and cylinder bores and matching up suitable parts (while keeping the weights within limits). 

Stanley Hooker in his memoir says that Ford of England built parts to tighter tolerances than RR did. Ford didn't have the trained labor force to do the hand selecting and every piece had to be totally interchangeable with every other piece of that part number. This was when Trafford Park was being set up. I have never read anything about RR tightening up their own allowable tolerances on parts but it might not be surprising to find out they did.

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## pbehn (Oct 9, 2017)

Shortround6 said:


> 1. The Merlin would have been an important engine no matter what. The Sabre was too big for many airframes and too expensive.
> The US certainly built plenty of R-1820s, R-1830s, R-2600s and V-1710s in addition to the R-2800s and R-3350s..
> 2 The real thing that saved the Merlin was better gasoline. Had the British been limited to fuel that would only support 12-15lbs of boost the Merlin would have seen much less use near the end of the war.
> 
> ...





Great post SR, I hate posts being cut to pieces so I have numbered yours and reply below.

*1 It is a sort of what if but the Spitfire and Hurricane both gained weight anyway, another possibility was the Griffon which actually happened with the Spitfire and Lancaster replacements.

2 I think that is a chicken and egg situation common in engineering and technology, improved superchargers demanded improved fuels which prompted experiments on further improved superchargers and fuels. The result in 1945 could not have been dreamed about in 1937.

3 It drives me nutz and this forum is the least worst I see.

4 and 5, That is the difference between true mass production and a small scale specialist. What is never discussed is that to produce all pieces quickly to one size you need one machine on one setting, like a capstan lathe. For large production runs you need a lot of machines and you can tolerate many more rejects. This is even true today with CNC machines but the differences are much smaller.*

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## Shortround6 (Oct 9, 2017)

I agree with your points however to elaborate on the fuel issue 


pbehn said:


> *2 I think that is a chicken and egg situation common in engineering and technology, improved superchargers demanded improved fuels which prompted experiments on further improved superchargers and fuels. The result in 1945 could not have been dreamed about in 1937.*



The production of high performance number fuel required both good feed stocks and large quantities of special compounds. You can't just add more lead to mediocre feed stock. 
The US and British changed the allowable blends of 100/130 several times in order to stretch production of the 100/130 using lower quality feed stocks. Sometimes extra refinery procedures could help out.

However 100/150 or 115/145 in large amounts required tens of thousands of tons of steel for extra refinery equipment and had to be balanced against ship production or other needs ( you can't use melted down I beams or railroad rail for refinery equipment) and obviously has to be planned for well before it it used in service. 

They were fooling around with triptane in WW II but it was very expensive and to use it as a major component in aviation fuel, instead of an additive, would have required even more tens of thousands of tons of steel to make a major production plant. 

Being able to make a fuel in batches of a few hundred gallons doesn't mean you can make it in batches of hundreds of thousands of gallons. 

I have no idea why (or at least that I can prove) but the Merlin, Griffon and Allison all were able to run at boost pressures much higher than most other engines, only the R-2800 came close.

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## tomo pauk (Oct 10, 2017)

Shortround6 said:


> ...
> I have no idea why (or at least that I can prove) but the Merlin, Griffon and Allison all were able to run at boost pressures much higher than most other engines, only the R-2800 came close.



Part of the answer re. some engines better withstanding greater boost than some others is the engine's compression ratio.
Eg. Mikulin engines were with ever smaller CR for each new model in the ww2 - started at 7:1 with AM35A, 6.8:1 for AM-38, 6:1 for AM-38F, ending at 5.5:1 for the AM-42. The last one was using 2 ata of boost on the Soviet 96 oct fuel, no water injection, no intercooler.


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## Shortround6 (Oct 10, 2017)

True but I was also thinking of the Sabre with maxed out, even post war, at about 65in ( Sabre VII) and the Hercules and Centaurus engines which seemed to max out the mid to upper 50s even 7-10 years after the war ended. None of the Wright engines ever seemed to go past 60 in either. (1525hp R-1820 excepted?)


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## pbehn (Oct 10, 2017)

Shortround6 said:


> True but I was also thinking of the Sabre with maxed out, even post war, at about 65in ( Sabre VII) and the Hercules and Centaurus engines which seemed to max out the mid to upper 50s even 7-10 years after the war ended. None of the Wright engines ever seemed to go past 60 in either. (1525hp R-1820 excepted?)


Just a question, can you directly compare compression ratios/boost levels of sleeve valve and poppet valve engines with the scavenging and combustion chamber shape being so different.


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## tomo pauk (Oct 10, 2017)

Shortround6 said:


> True but I was also thinking of the Sabre with maxed out, even post war, at about 65in ( Sabre VII)
> ...



Compression ratio 7:1. So IMO it would've been very unlikely that it was able to withstand boost pressures of what Merlin & Griffon were doing, with CR of 6:1 for both. 
We can recall than one of considered options for the Allison V-1710 'G' series was reduction of the CR from 6.65:1 down to 6:1 in order to increase the boost.


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## pbehn (Oct 10, 2017)

Shortround6 said:


> I agree with your points however to elaborate on the fuel issue
> The production of high performance number fuel required both good feed stocks and large quantities of special compounds. You can't just add more lead to mediocre feed stock.
> The US and British changed the allowable blends of 100/130 several times in order to stretch production of the 100/130 using lower quality feed stocks. Sometimes extra refinery procedures could help out.
> 
> ...


A great illustration of what total war means. I doubt if many would see any connection between professors of chemistry and their technicians beavering away in labs ith their knights of the sky in fighters and bombers. Some may even have considered them draft dodgers and shirkers.

One thing Packard did bring to the Merlin was the use of Indium coated bearings. Wikipediaa says "In 1924, indium was found to have a valued property of stabilizing non-ferrous metals, and that became the first significant use for the element.[59] The first large-scale application for indium was coating bearings in high-performance aircraft engines during World War II, to protect against damage and corrosion; this is no longer a major use of the element.[" Imagine the thousands of man hours needed to find how to coat the bearing and which thickness coating to use before going through long term reliability tests on Merlins before use, all for a minor improvement on one small part of an engine.

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## fastmongrel (Oct 10, 2017)

rodg said:


> That , and two of the smaller lorries used by the military used the Meteor engine



The Antar used the Meteorite which was a V8 version of the Meteor. They still had a few Antar MkIs when I was in the mob and they made a lovely sound but drank petrol like an Irishman in a brewery. iirc 3 miles to the gallon at 20mph was about the best fuel consumption possible.


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## Shortround6 (Oct 10, 2017)

pbehn said:


> Just a question, can you directly compare compression ratios/boost levels of sleeve valve and poppet valve engines with the scavenging and combustion chamber shape being so different.




Maybe not but if power is in proportion to the amount of fuel/air burned (some engines used extra fuel as an internal coolant) then power has a pretty close relationship with the amount air flowing through the engine. 

rpm times the size of the cylinders times the weight of air (and fuel) per cylinder filling per unit of time. higher pressure means a higher weight of air/fuel per cylinder filling (intake/power stroke)


Yes higher compression gets more power from the same amount of fuel burned but the difference in power is much smaller than increasing the amount of fuel and air burned. 
Maybe the sleeve valve does allow for better cylinder filling but filling the cylinder when you have 24-40lbs of pressure in the intake manifold/intake ports is a lot different than when the descending piston is trying to suck air from a manifold with less than 15lbs pressure (normal pressure at sea level) like a non-supercharged engine. 

The real difference for high power using large amounts of boost may have been cooling problems with the sleeve valve system. 
In a normal cylinder the heat path is through the cylinder walls (one piece) and either into the coolant for a wet sleeve liquid cooled engine or into the fins on an air cooled engine. With the sleeve valve the heat has to go through the sleeve, through the oil film between the sleeve and jacket (either water cooled or aircooled. 

It may be this extra "layer" and the need to keep from over heating the oil the that limited the boost in the sleeve valve engines.

Just a theory.


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## pbehn (Oct 11, 2017)

Shortround6 said:


> Maybe not but if power is in proportion to the amount of fuel/air burned (some engines used extra fuel as an internal coolant) then power has a pretty close relationship with the amount air flowing through the engine.
> 
> rpm times the size of the cylinders times the weight of air (and fuel) per cylinder filling per unit of time. higher pressure means a higher weight of air/fuel per cylinder filling (intake/power stroke)
> 
> ...


Great post S/R, I had in mind my experience with two/four stroke engines. They have compression ratios port opening and closing times but they do not exactly compare. Also for reasons you state about the lubrication of the sleeves etc the oil took a lot more cooling than poppet engines.


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## pbehn (Oct 12, 2017)

Rolls Royce were helped by some things purely by accident. The Merlin was an engine type they had a lot of experience within both civil/military and racing use. They had a few years in peacetime to sort things out and then when the war started it was ordered for four engined bombers. If an engine fails in a single engine fighter you will be lucky to get anything to examine. However if an engine fails or is damaged on a four engine bomber it has three others to get home. An unladen Lancaster could fly on two engines but they were on maximum power. I read of one Lanc (I think in "The Lancaster" by I McInstry) whose third engine loss, happened as it came into land. While it is great that the crew got home safely a failure in service at maximum power for an extended period is pure gold to a research department a test bed only goes so far in simulation.

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## YF12A (Oct 12, 2017)

pbehn

I could not agree more. My neighbor made it back "more times than he wanted to remember" with R-1820's wounded or dead. He told me he came back "a few times" on just 2 good engines, hopefully, like you said, these were examined and useful information was obtained from them.

What absolutely kills me are the pictures from the Pacific B-29 bases, they had so many dead R-3350's, they were just put in big piles. But everyone already knew about the problems with that engine from the start.

I'm in the Car business and found out forever ago that X amount of miles on Y amount of vehicles { car, motorcycle, aircraft, heck, just about anything ) in a short time frame just can not give you real world usage feedback until it is put into the hands of its' user.


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## pbehn (Oct 12, 2017)

YF12A said:


> pbehn
> 
> I could not agree more. My neighbor made it back "more times than he wanted to remember" with R-1820's wounded or dead. He told me he came back "a few times" on just 2 good engines, hopefully, like you said, these were examined and useful information was obtained from them.
> 
> ...



I only know what I have read on this forum but what I have read is very authoritative. When an engine was run at maximum boost it was done so for a limited time and any time over that was recorded by the pilot or flight engineer to advise the ground crew who controlled engine servicing.. I know there was a war on but in the case I quoted I don't believe there is any chance a Lancaster with three non functional engines would just have those replaced. The failed engine and that last running engine are research gold. After 1940 removing rebuilding and re installing Merlins became quite an industry in UK.

The B 29 was pushing the boundaries in every direction and there was a war on. In a war you pee with the pot you have until you get a better one.


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## swampyankee (Oct 13, 2017)

pbehn said:


> That is colder than any temperature I have experienced in UK.



You haven't missed much. Indeed, I suggest that it's your good luck you haven't. I've spent far too many seconds (about 300 of them) outside in -32C, and I'd rather not do anything like that again. I would like to remain attached to my toes.


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## pbehn (Oct 13, 2017)

swampyankee said:


> You haven't missed much. Indeed, I suggest that it's your good luck you haven't. I've spent far too many seconds (about 300 of them) outside in -32C, and I'd rather not do anything like that again. I would like to remain attached to my toes.


Oh I was careful with my words swampy, I said in UK. However on the coldest night recorded in Northern England (-21C 1978) I spent the night with my girlfriend in Redcar and then rode a 350cc Yamaha to Hartlepool about 25 miles on iced roads. By the time I arrived at work I had lost all feeling in my fingers and toes. I didn't get off the bike I just let it fall over. By comparison -35C in Germany was a positive pleasure because the air is so dry and still however a UK car at the time only had anti freeze good enough for -25 and my cars water pump housing froze and cracked.

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## swampyankee (Oct 14, 2017)

pbehn said:


> Oh I was careful with my words swampy, I said in UK. However on the coldest night recorded in Northern England (-21C 1978) I spent the night with my girlfriend in Redcar and then rode a 350cc Yamaha to Hartlepool about 25 miles on iced roads. By the time I arrived at work I had lost all feeling in my fingers and toes. I didn't get off the bike I just let it fall over. By comparison -35C in Germany was a positive pleasure because the air is so dry and still however a UK car at the time only had anti freeze good enough for -25 and my cars water pump housing froze and cracked.



I lived in Chicago at the time. It had been about 15C two days earlier (the weather in the Midwestern US can closely approximate Purgatory), and several people had the coolant in their cars freeze.

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## Koopernic (Oct 15, 2017)

Note that the original 100 octane that the RAF used to replace 87 octane really was only 100 octane ie more like 100/100 and purchased or “free” lend lease supplied from American refineries. It did not have as significant rich mixture response. The latter 100/130 came from the addition of synthetic alkylate produced from acid alkylation. Hence the RAF can thank Major Jimmie Doolittle for winning the BoB because it was he who apart from BeeGee racing, and heading the Tokyo air raid from the Aircraft carrier Hornet was responsible for aviation fuels development at shell in the 1930s and make sure there was refinery capacity to produce 100 octane. The process of catalytic cracking with regenerative catalysts was used. The rich mixture techniques developed and tested in Schneider floatplane trophy racing must have come into use well after BoB.

Without the 100 octane fuel Merlin power was around 1030 rather than 1280.

The Germans struggled as their investment was directed at coal to oil technology. They used a different way of producing octane from syngas to upgrade their fuel but latter also added alkylation.

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## GregP (Oct 15, 2017)

It cannot be like you said Shortround. If all Rolls Royce did was sort through bins of parts, they would have had a huge mountain of scrap parts that didn't exist. And they didn't have that when Merlin production ended. Not all their parts fit other required parts, and they DID had fit and had file. They just tried to start with a part closer to what was needed to reduce the hand-fitting process. That's why they call it hand fitting. If the production process produced parts as loose as you contend, then they HAD no process.

Can't buy it, but there is NOTHING wrong with a hand-fitted Merlin ... until you needs spares and don't have the skills available to re-fit new parts. Then you sell it to someone who has the expertise and go get a Packard, so you can get parts that work without all the hand fitting. You STILL have to hand-lap the main, rod, and cam bearings, but not hand-fit EVERYTHING. If you can't do that, you can't fly a big V-12 airplane from WWII that experiences wear unless and until you find someone who CAN do it.

I can tell you from personal experience that main bearings for Allisons and Merlins do NOT fit today when brand new (because ALL are remanufactured ... no NEW mains for a LOT of years), or the manufacturing process is just plain old wrong. They remanufacture the bearings oversize so they require hand-lapping, plastigage, and go-no go gauges for fitting crankshafts fitted with plain bearings of any kind. To get away from that, you need to go to ball-bearing mains. Neither the Merlin nor the Allison have ball bearing mains.

On page 135 of the Rolls Royce Merlin Service Manual for Series II engines (1938), the clearance for the main bearings is .004 - .00475. for new bearings (hand lapped) and .006 when it reaches the service limit. If you try to run it with larger clearances, you lose too much oil pressure and it falls out of flight limits. Other version have similar clearances.

Same for an Allison, but the actual clearance may be slightly different. Haven't checked in a couple of years ... I seem to recall .003 - .005.

The actual spec calls for installing a crankshaft gauge tool and tightening the main studs to full torque. You MUST be able to rotate the tool by hand (yes, there IS a torque spec). Trial and error for some years sets the actual clearances that you must scrape to, and they are covered in a separate maintenance instruction so that if the manual falls into enemy hands, they can't assemble it successfully without a complete set of manuals. No single manual had ALL the specs. The guys who do Allisons HAVE all the specs today a,d share them among themselves.

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## pbehn (Oct 15, 2017)

GregP said:


> It cannot be like you said Shortround. If all Rolls Royce did was sort through bins of parts, they would have had a huge mountain of scrap parts that didn't exist. And they didn't have that when Merlin production ended. Not all their parts fit other required parts, and they DID had fit and had file. They just tried to start with a part closer to what was needed to reduce the hand-fitting process. That's why they call it hand fitting. If the production process produced parts as loose as you contend, then they HAD no process.
> .



I don't believe they had bins full of parts as in finished parts but blanks or part machined pieces awaiting the final cut. In the early days RR needed to make Merlins for themselves to get an engine that worked and could be tested. Then they needed engines for prototype Spitfires Hurricanes Defiants and Battles. The early orders for these aircraft were in hundreds not thousands and you do not set up or use mass production techniques for small production runs.


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## Shortround6 (Oct 15, 2017)

Koopernic said:


> Note that the original 100 octane that the RAF used to replace 87 octane really was only 100 octane ie more like 100/100 and purchased or “free” lend lease supplied from American refineries. It did not have as significant rich mixture response. The latter 100/130 came from the addition of synthetic alkylate produced from acid alkylation. Hence the RAF can thank Major Jimmie Doolittle for winning the BoB because it was he who apart from BeeGee racing, and heading the Tokyo air raid from the Aircraft carrier Hornet was responsible for aviation fuels development at shell in the 1930s and make sure there was refinery capacity to produce 100 octane. The process of catalytic cracking with regenerative catalysts was used. The rich mixture techniques developed and tested in Schneider floatplane trophy racing must have come into use well after BoB.
> 
> Without the 100 octane fuel Merlin power was around 1030 rather than 1280.
> 
> The Germans struggled as their investment was directed at coal to oil technology. They used a different way of producing octane from syngas to upgrade their fuel but latter also added alkylation.



You are in error about the British 100 octane fuel. It did have a rich mixture response. We have been over this many times. The British were _NOT _saved by American 100 octane fuel.
American 100 octane fuel could NOT have _more than _2% aromatic compounds.
British 100 octane fuel could NOT have *less than *20% aromatic compounds.

This was included in the list of specifications for the fuels by the respective governments/buying agents. The British may have *bought* fuel from "American" refineries but it was to their specification and not American specification. The British also had refinery/s in the _Americas, _such as the one/s in Trinidad that reached a capacity of 285,000 bbl/day in 1940. There were also refineries in England capable of making 100 octane fuel from imported feed stocks.

British 100 octane fuel during the Battle of Britain did vary from batch to batch but was usually between 115 to 120 for rich response when tested later after the invention/development of the Performance Number Scale. 

American 100 octane was just about 100PN for rich mixture response although it to could vary a few points up _or down_ from 100. A few batches were 100 octane lean and in high 90s running rich. 

The Schneider floatplane trophy racers in the last of the 1920s and in the 30s didn't even run on gasoline but some rather exotic fuel blends cooked up by Francis Rodwell Banks. Try googling him before you give ALL the credit for 100 octane fuel to Major Jimmie Doolittle.

BTW the British knew about rich mixture response even with their 87 octane fuel, they just didn't know how to specify it in numbers directly. They did know that fuels with a fair amount of aromatic compounds did have better rich mixture response than fuels with little or no content of aromatics.

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## Shortround6 (Oct 15, 2017)

GregP said:


> It cannot be like you said Shortround. If all Rolls Royce did was sort through bins of parts, they would have had a huge mountain of scrap parts that didn't exist. And they didn't have that when Merlin production ended. Not all their parts fit other required parts, and they DID had fit and had file. They just tried to start with a part closer to what was needed to reduce the hand-fitting process. That's why they call it hand fitting. If the production process produced parts as loose as you contend, then they HAD no process.



Bearings may in a different catagory than pistons. 

There are maximum and minimum dimensions, as you well know, and if a part is over or under it won't even get to the assembly area. 

According to one book I have the Merlin pistons were supposed be between 5.370 and 5.368 in measured at the top at right angles to the gudgeon pin when new and 5.380 to 5.378 at the bottom of the skirt also at a right angle to the gudgeon pin. A 0.010 taper? allowance for greater expansion in the piston head when hot? Clearance between Piston and cylinder wall was 0.030 to 0.034in at the top and 0.020 to 0.024 at the bottom when new. Permissible worn was 0.045 at the top and 0.035 at the bottom. 

A fitter/assembler might very well measure a cylinder bore and select a piston that gave a good fit, it might be the first he picks up up. It might not be a good fit for that cylinder but might very well fit the 2nd or 4th cylinder better. 

Things like pistons and piston-rod assemblies also had weight tolerances. I don't know what the minimum and maximum weights were but all the pistons in a _single _engine had to be within a 1/2 ounce range (including rings) which means it was quite possible to assemble an engine using all light pistons, another using all medium pistons and a 3rd using all heavy pistons and yet meet the specification. 

Clearance of the crankshaft bearings was 0.004 to 0.00475 new and 0.006 maximum worn. Crankshafts were allowed to be reground twice. 

I would note that many cars of the time used poured babbit bearings that needed to be scraped and lapped to fit. 

Unless someone can actually find descriptions of workers measuring up a cylinder bore and then measuring a piston out of a rack of pistons, taking said piston over to a lathe. putting said piston into a chuck or fixture and then taking a "cut" of a few thousands of an inch and going back the engine to fit the piston to the piston rod and then repeating this process over and over I think we can dispense with "filing and fitting".
There may have been a bit of filing, grinding or drilling to remove a bit of weight to bring an over weight piston into spec but I would imagine that this would be done before the pistons got the assembly area. Having metal chips or metal filings floating around your final assembly area isn't a very smart thing to be doing.


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## GregP (Oct 15, 2017)

Right, you don't usually file or hone pistons. That's why they have rings!

Perhaps I simply misunderstood and your intention is correct. It's happened before, Shortround, and I VERY rarely catch you wrong. Probably fewer times than your wife does ... 

Just to be clear, there is NOTHING wrong with hand-built craftmanship. It runs great, last as long or longer than mass-production engines, and has only the shortcoming that fitting replacement parts may be troublesome compared with the mass-produced engine. To many, that is not a problem.

Also, the British engines said "Rolls Royce" on them, and that has been worth something. quality-wise, for a LONG time. No argument there ...


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## fastmongrel (Oct 15, 2017)

Koopernic said:


> purchased or “*free” lend lease* supplied from American refineries.



Have a look at when the Lend Lease was signed and when it came into effect.

As for 100 Octane most used by the RAF in 1940 came from refineries in the Caribbean, Venezuela and the Persian Gulf. Any that came from US refineries was paid for Cash and Carry no credit allowed. Theoretically if the Germans had the cash they could have bought fuel from the US.

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## Shortround6 (Oct 15, 2017)

I would note that there was a short lived American specification for 100/125 fuel.

The Americans and British agreed to a "common" 100/130 fuel specification shortly after that. 
However they went through at least 3 different specifications for 100/130 fuel that differed in the amount of allowable lead per gallon and perhaps other things. There may have been either later specifications or combined changes for allowable amounts of certain aromatic compounds along with the last change in allowable lead. I don't know, most accounts are not clear. However each change allowed for increase production of 100/130 from the available base stocks (more gallons of aviation fuel from the same number of tons of crude). 
I do know that post war there was one specification for military 100/130 fuel and another for civilian or commercial 100/130 fuel. The Commercial/Civilian fuel was allowed less lead per gallon. More expensive (needed more costly base stock) but saved on spark plugs and plug changes. 

The History of aviation fuel is not well documented and has to be drawn from various places. 

Roy Fedden of Bristol was another Englishman who pushed for 100 octane fuel during the late 30s. His company had nothing to do with fuel except wanting the greater performance such fuel would bring.
Rolls-Royce had announced power levels for the Merlin at the 1938 Paris AIr show/exhibition using "100" octane fuel but I don't know if the 100 octane they were testing in 1938 was the same as the British government was buying and stockpiling in the fall of 1939.

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## pbehn (Oct 15, 2017)

Shortround6 said:


> I would note that there was a short lived American specification for 100/125 fuel.
> 
> The Americans and British agreed to a "common" 100/130 fuel specification shortly after that.
> However they went through at least 3 different specifications for 100/130 fuel that differed in the amount of allowable lead per gallon and perhaps other things. There may have been either later specifications or combined changes for allowable amounts of certain aromatic compounds along with the last change in allowable lead. I don't know, most accounts are not clear. However each change allowed for increase production of 100/130 from the available base stocks (more gallons of aviation fuel from the same number of tons of crude).
> ...



Great post SR and you have made many on the same subject. Why not just put all that you know in a post/thread over a period of time so that such discussions can be answered with a link to it. Each post is informative but just forms a patchwork spread all over forum discussions which are impossible to find. This thread is about bad steel in Merlins, it wouldn't show up readily in a search about fuel.


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## wuzak (Oct 15, 2017)

Koopernic said:


> Note that the original 100 octane that the RAF used to replace 87 octane really was only 100 octane ie more like 100/100 and purchased or “free” lend lease supplied from American refineries. It did not have as significant rich mixture response. The latter 100/130 came from the addition of synthetic alkylate produced from acid alkylation. Hence the RAF can thank Major Jimmie Doolittle for winning the BoB because it was he who apart from *BeeGee racing*, and heading the Tokyo air raid from the Aircraft carrier Hornet was responsible for aviation fuels development at shell in the 1930s and make sure there was refinery capacity to produce 100 octane. The process of catalytic cracking with regenerative catalysts was used. The rich mixture techniques developed and tested in Schneider floatplane trophy racing must have come into use well after BoB.




BeeGee Racing

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## buffnut453 (Oct 15, 2017)

I could have gone my ENTIRE LIFE without seeing that photo. Thanks a bunch. Now it's burned into my memory. My eyes!!! MY EYES!!!!!

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## ChrisMcD (Oct 19, 2017)

GregP said:


> It cannot be like you said Shortround. If all Rolls Royce did was sort through bins of parts, they would have had a huge mountain of scrap parts that didn't exist.



Not sure what the quantity was, but a lot of Merlin parts that failed quality control were used in the Meteor tank engine - as were '"crashed" merlins that were not considered airworthy
Rolls-Royce Meteor - Wikipedia

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## ChrisMcD (Oct 19, 2017)

On the subject of 100 octane for the BoB, this link is interesting 

100-Octane

AFAIK the two opinions are mostly correct and together give a fairly complete picture.

I have a feeling that once a lot of American engines were in Britain in 1941, there was a move to co-ordinate Octane numbers. Probably after the problems with P-38's.


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## tomo pauk (Oct 19, 2017)

ChrisMcD said:


> On the subject of 100 octane for the BoB, this link is interesting
> 
> 100-Octane
> 
> ...



Thanks for the link. 
'Problems' with P-38 were related to many things, fuel not being high on the list, if even it was on the list.
By the time P-38J was in problems (winter of 1943/44), the Allies have long accepted the 100/130 fuel as standard.


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## swampyankee (Oct 22, 2017)

Selective fit is anathema to the assembly line, but as recently as thirty or so years ago, it was normal practice for production of civilian firearms. Firearms need close fits and the extra labor costs of selective fit were lower than the costs of machinery that could hold tight enough tolerances.

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## Shortround6 (Oct 22, 2017)

As I have mentioned before my father was a production engineer for Colt firearms from the early 60s to the early 80s. 
The parent company, Colt Industries, used profits from the M-16 during the Vietnam war to by up other companies, like Holly Carburetor and Fairbanks Morse pumps rather than invest in new tooling. 
While they may not have been using machine tools dating back to Sam Colt himself some of the machine tools were pretty old and not in the best shape. Like drill presses that tended to "wander" and hand fitting was still the order of the day on revolvers. Some parts were "stoned" into tolerance on the assembly benches as they were already heat treated and filing wasn't going to work. My father did get a blueprint changed for a cylinder stop (the part the fits into the notches at the rear of the cylinder) like this one. 




After he found that the assemblers were having to stone .005-007in of the top of the lug to left on average to get them to fit. Management agreed to change the dimensions so they only had to stone off .002-004in 
CNC machines were just coming into service an I can remember a few times my father went to trade shows and came back with demonstration samples from machines.
One reason Colt had such high prices at the time was that they had a truly horrendous scrap rate and high manufacturing costs but the "Colt" name they could charge the higher prices and get away with it. Very few bad parts made it into finished guns but an awful lot of semi-finished parts went out the door in scrap barrels. But no new machines was the order of the day from management.

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## ChrisMcD (Oct 22, 2017)

tomo pauk said:


> Thanks for the link.
> 'Problems' with P-38 were related to many things, fuel not being high on the list, if even it was on the list.
> By the time P-38J was in problems (winter of 1943/44), the Allies have long accepted the 100/130 fuel as standard.



Not my area of expertise, and no way am I sticking my finger into that mincer! But this thread seems to have considered it important.
The P-38J and L in the European theater.


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## Aozora (Oct 26, 2017)

One of the best sources of information on the developmental and production problems of the Merlin is _The Merlin in Perspective:The Combat Years_, by Alec Harvey-Bailey (Rolls-Royce Heritage Trust, Historical Series No 2) Amazon product
_View: https://www.amazon.com/Merlin-Perspective-Combat-Years-Historical/dp/1872922066_

Harvey-Bailey became head of quality control for Merlin production: some excerpts from his book are attached. Most of the steels and alloys used in the Merlin were developed by Rolls-Royce specifically for high powered aero-engines, so the claim that there was "poor quality" steel used is completely wrong: as Harvey-Bailey explained, the biggest problems encountered in the Merlin came about through some poorly designed components that were redesigned as soon as any weaknesses were discovered.
Also attached is an interesting article by A.C Lovesey, one of the main engineers in charge of Merlin development: Cyril Lovesey - Wikipedia This article is posted on WW II Aircraft performance http://www.wwiiaircraftperformance.org/merlin-lovesey.pdf

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## fastmongrel (Oct 27, 2017)

Aozora said:


> One of the best sources of information on the developmental and production problems of the Merlin is _The Merlin in Perspective:The Combat Years_, by Alec Harvey-Bailey (Rolls-Royce Heritage Trust, Historical Series No 2)
> _View: https://www.amazon.com/Merlin-Perspective-Combat-Years-Historical/dp/1872922066_



Curse you. Thats another book I will have to buy and add to the groaning bookcase.

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## Shortround6 (Oct 27, 2017)

It does spell out most if not all of the differences between the different Merlins although a bit short on actual time lines. 

Some experimental versions are in the tables.


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