bobbysocks
Chief Master Sergeant
cool! thanks....I will look at it when I get off of work.
Bad Steel in the Rolls-Royce Merlin?
- Thread starter SKR_01
- Start date
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cool! thanks....I will look at it when I get off of work.
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.
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.
Shortround6
Major General
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.
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.
Shortround6
Major General
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.
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.
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.
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.
Shortround6
Major General
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.
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.
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
1st Sergeant
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.
Shortround6
Major General
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.
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.
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.
YF12A
Airman
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.
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.
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.
swampyankee
Chief Master Sergeant
- 3,954
- Jun 25, 2013
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.
swampyankee
Chief Master Sergeant
- 3,954
- Jun 25, 2013
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.
