Merlins > Packard vs RR

[FLYBOYJ]

Originally Posted by Hop

It's not hard to keep the good stuff for airframes when it comprises 75% of the aluminium, and use the low grade stuff for seats and handles and mess tins etc.

Yes and no...
When you have aluminum ingot that is on the "low end" of the tolerance, it still meets specs but may have a higher level of impurities. Those impurities may come back and haunt you later on as when the "part" is subjected to environmental conditions, things like intergranular corrosion will develop more easily than if the material was at the upper end of the spec to begin with. As stated, I was involved with this in the early 80s. Several manufacturers refused to used Reynolds in their aircraft because of this...

[glennasher]

I don't know anything about technical stuff, but I did overhear a Mustang pilot at an airshow, talking about the Merlin in his Mustang, and he swore the RR he now had, ran smoother than the previous Packard. That is, of course, just hearsay, but he firmly believed it. I don't know any reason to disbelieve him. He does (did) a lot of aerobatics in his bird, and had a pretty good feel for his plane.

[k9kiwi]

A collection of notes from varying sources.

Wiki

The initial Packard modification on the Merlins were done on this engine by changing the main bearings from a copper lead alloy to a silver lead combination and featured indium plating. Indium plating had been developed by the General Motors (Pontiac Division) to prevent corrosion which was possible with lubricating oils that were used at that time. The bearing coating also improved break-in and load carrying ability of the surface. British engineering staff assigned to Packard were astonished at the suggestion but after tear down inspections on rigidly tested engines they were convinced the new design offered a decided improvement.

The real improvement Packard incorporated into the Merlin was adopting the Wright supercharger drive quill. This modification was designated the V-1650-3 and became known as the "high altitude" Merlin destined for the P-51. The ((two speed, two stage supercharger)) section of the V-1650-3 featured two separate impellers on the same shaft which were normally driven through a gear train at a speed of 6.391:1. A hydraulic gear change arrangement of oil operated clutches could be engaged by an electric solenoid to increase this ratio to 8.095:1 in high speed blower position. The high speed gear ratio of the impellers was not as great as the ratio used in the Allison but speed of the impeller alone was not the factor that increased the engine performance at altitude. The double staging of the compressed fuel/air mixture provided the boost pressure through a diffuser to the intake manifolds which increased the critical altitude of the power plant.

When the first of the Packard-built Merlins arrived in Britain, the engineers at Rolls-Royce stripped it down and were amazed to find that the production-line built Packard engine, far from being as bad as they expected it to be for component tolerances, was actually better. Up until then, R-R Merlins were hand built, every face being finished off by hand, and this time-consuming process placed great strain on the production capability of the skilled workforce involved in the manufacture of these engines. The Packard engine changed many minds, although there were still some at R-R who remained unconvinced of the quality of the American engine, produced as it was by a largely unskilled and semi-skilled female workforce. In the end, the engine's performance removed any doubts about its quality and workmanship.

Next, by reading the flamin manual (Air Publication 2062 A & C) for the Lancaster it shows clearly that the RR Merlin XX, 22 or 24 engines were fitted with SU carbs while the Packard Merlin 28 or 38 had Bendix Stromberg pressure injected carbs.

Also the 28 and 32 engines achieved a significant saving in fuel compsumption.

Boost at +7 lbs./sq.in, RPM 2,650 Medium boost at 5,000 feet altitude usage per hour

Packard 240 gallons
Rolls Royce 260 gallons

It should also be noted that at no point in the AP for the Lancaster is any warning given about a reduction in performance between the two engine types.

That only one type of engine would be used on a particular airframe is of course obvious, as later marks, even batches ordered used immersion pumps and different fuel / oil systems altogether to the early models.

[mkloby]

Originally Posted by FLYBOYJ

Yes and no...
When you have aluminum ingot that is on the "low end" of the tolerance, it still meets specs but may have a higher level of impurities. Those impurities may come back and haunt you later on as when the "part" is subjected to environmental conditions, things like intergranular corrosion will develop more easily than if the material was at the upper end of the spec to begin with. As stated, I was involved with this in the early 80s. Several manufacturers refused to used Reynolds in their aircraft because of this...

Especially the havoc that a salt water environment can have on aircraft...

[trackend]

Originally Posted by k9kiwi

Next, by reading the flamin manual (Air Publication 2062 A & C) for the Lancaster it shows clearly that the RR Merlin XX, 22 or 24 engines were fitted with SU carbs while the Packard Merlin 28 or 38 had Bendix Stromberg pressure injected carbs.

That don't surprise me the SU's have always been really beautifully made carbs but noted to be more juicy than strombergs

[kool kitty89]

In the case of the RR Merlin 20 series the boost limitations were continually increased from +10.34 psi, to +12 psi (first in low gear, then later high), to +14 psi (in low), and eventually +16 psi (in high gear) for WEP.

This resulted in power going from 1,300 hp to 1,390 hp, 1,480 hp, and finally ~1,510 hp.

From: Hurricane Mk II Performance
http://www.wwiiaircraftperformance.o...s-10june40.jpg
http://www.wwiiaircraftperformance.o...xx-15nov40.jpg
http://www.wwiiaircraftperformance.o...xx-18nov42.jpg
http://www.wwiiaircraftperformance.o...xx-21nov42.jpg
http://www.wwiiaircraftperformance.o...x-curve-c1.jpg



The V-1650-I (based on the Merlin 20 series) was rated for 51.1" Hg MAP (+10.34 psi) for take-off and emergency power and I haven't seen doccuments for increased boost limits for the engine.

[mhuxt]

FWIW, Merlin 25s used +18 in the Mosquito FB.VI. Not sure what the Packard Merlins had in the 225, though I imagine if I keep reading, I'll find out eventually.

Then there's the whole 150 octane thing....

[kool kitty89]

Yes, but increases up to the +16 psi were all on the same fuel (100/130 octane iirc) the restricting factor had been structural concerns (not detonation issues), and as testing on the engine progressed higher and higher power settings were allowed.

I just don'r know if this was done on the V-1650-1. (the answer would also introduce some more data to the Allison Vs Merlin P-40 comparison thread)

[mhuxt]

Yes, +18 was on the "normal" fuel.

[kool kitty89]

Ok both the Merlin 24 and 25 were rated for max +18 psi resulting in ~1640 hp at ~2,250 ft. With ~1510 hp in high gear at ~9,300 ft.


As shown in the link for graph I posted earlier:
http://www.wwiiaircraftperformance.o...x-curve-c1.jpg

And shown for high high gear as well here:
http://www.wwiiaircraftperformance.o...x-curve-c2.jpg

[P-Popsie]

Originally Posted by evangilder

They didn't really re-engineer the Merlins. The drawings that were provided were not the usual customary drawings that American engineers are used to, so they had to tear it down and do the drawings that they expected to build the motors.

if by chance you had an online copy of these american conversion blueprints or a location for them i would be most grateful to you for them.

[P-Popsie]

Well i've read a bit more of this rather heated thread i could of sworn the original idea was best engine to which my two cents worth goes to the merlin Packard or RR for two reasons one no other engine to my knowledge was used so universially Fighter, Night Fighter, Light Bomber, Heavy Bomber, All classes of A/C in the U.K arsenal were powered by the merlin. Moreover this is the only A/C engine i know of to be used in armoured vehicles if versitility = best then there's my vote

[kool kitty89]

See my post #96 which brings up an important point -pertinant to the original question- not mentioned previously. (despite the long thread )

[Skip M]

Originally Posted by P-Popsie

Moreover this is the only A/C engine i know of to be used in armoured vehicles if versitility = best then there's my vote

What about all of those funny round things in M3 light, M3 medium, and M4 and M4A1 medium tanks?

[Skip M]

In reading this thread that the contributers to this forum have their own thoughts and do not repeat the same old lines. That is why I joined this forum.

Not all that much has been brought up on the very different labor forces that each country had to work with. I do not believe that England could have built a Packard Merlin and I know the US could not build a RR Merlin in the numbers needed. England had the highest percentage of machinists in their population in the world. This goes back to the beginning of the industrial age. This type of skilled worker can do a large number of jobs and hand fitting is the norm and the mark of a craftsman. You do not need to give tolerances for this type of worker. As long as you can move them to the industries that you need at the time and you have enough you will get a RR Merlin engine. Germany and Japan allowed many of their craftsmen to be drafted and their quality suffered. The US had a higher percentage of unskilled and agricultural workers then England in spite of our industrial output. Moreover most of our industries were fairly young and when they started they had train a fresh work force. No other country had the success at that time of creating industries with this type of work force. Instead of taking years to make a craftsman you take days or weeks to teach one small job to a person. The skills of the craftsman is broken down into many jobs. This works very well with mass production. This allows you to go into farm country and in a year build a factory and be producing tanks. aircraft, engines, radar, and build thousands of ships. Craftsmen do not like this type of work as it is below them. I do not remember the book but in the 1960's I was reading that the RR Merlin was a little more powerful and smoother. The Packard easer to fix and keep flying. You did not have to hand fit the replacement parts. Both countries built the correct engines for their work forces.