Thread: Merlins

how do you tell the difrence between a RR built Merlin and a Packard built Merlin
























the packard has the oil on the inside

Originally Posted by clean32

how do you tell the difrence between a RR built Merlin and a Packard built Merlin
























the packard has the oil on the inside

Aside from that, some Packard built Merlins had fewer studs holding the primary supercharger halves together on twin stage Merlins. I don't know if there is a register of serial numbers anywhere. That would probably be the only way to determine the builder other than those that had the lesser number of studs. Old WWII RAF fitters told me they preferred the Packard built engines for the simple reason that a high quality US tool kit was supplied with every Packard built engine.
They were built by Rolls Royce at Derby and Glasgow, Ford at Manchester in a purpose built plant, Packard & Continental in the USA, and James Kirby in Australia, or by CAC in the James Kirby plant depending how you look at it. Pugh the RR historian says James Kirby. Kirby's own biography also claims credit for manufacture of Merlins in Oz. In 1963 I obtained Merlin special tools from a storeman at James Kirby, paid for in bottles of Resch's. Nev. Morris at Dalby has a running restored Merlin in his shed, twin stage, probably Mk 63, recovered from a WWII crash site on the Darling Downs.

There were quite a few little differences that the yanks introduced to aid the manufacturing lines. The spur drive for the blowers are a bit simpler, less studs as pointed out, coil packs, rings\pistons, Valve size as is the head porting. UNF @ UNC instead of whit worth etc, hence the tool kit. A bit like DC3 and there stupid star lock screws.

as a rule the RRs had a bit more oumph but the yanks had the life.

As a side note, the poms first asked Mr Ford to build there motors, he declined because he thought that England would fall to the Nazis and that he wouldn’t get paid. Besides he was making more from building trucks for the Nazis.
As for the P51 being American, that’s a joke, the US army having been fleeced of most of there aircraft to be sold to the poms had a bit of a bitch up. So when the pomes wanted to purchase more P40s the army said Nope we want them all. so enters north American with there German Jewish engineers who were up until 18 months before were working for Henkel, ( check out Henkel’s companion to the ME109 elliptical wings and all and that 3 years before the spit). The only motor available was the Allison. From that we got the XP51 GROUND ATTACK. it’s fat laminar flow wings ideal to stand up to the low level buffeting required of close in ground support ( taxi rank, a Kiwi idea) ( aussies were back in the pacific around this time).
Any way the abrasive desert environment wasn’t very nice to the fabric of the hurricanes, no more P40s were showing up but XP51 were, problem no parts supplies for the Allison’s, no problem stuff a Merlin in and that was the unofficial birth of the P51. In reality the P51 only claim to fame is it wide undercarriage and its fuel capacity. they are a bit to stable to be a good fighter.

Originally Posted by vnx205

There is a Merlin engine in the Binalong Motor Museum, along with a lot of other interesting machinery.

My recollection is that even on the outside, it looks incredibly complex, a real plumber's nightmare.

How does the power output John mentioned in the OP compare with similar engines 80 years later?

I just finished watching a TV series called "A plane is born", which was made in / around 2000 and from memory the Rotax engine they used was around 1.3L and developed about 100hp. That's a 4 cyl horizontally opposed 4 stroke pushrod engine with carbs.

It is a shame they stuck with carbs...

Bogged from wikipedia:

Carburettor developments

The Merlin's lack of direct fuel injection meant that both Spitfires and Hurricanes were, unlike the contemporary Bf-109E, unable to nose down into a deep dive. Luftwaffe fighters could therefore 'bunt' into a high-power dive to escape attack, leaving the pursuing aircraft spluttering behind as its fuel was forced by negative 'g' out of the carburettor. RAF fighter pilots soon learned to 'half-roll' their aircraft before diving to pursue their opponents. The use of carburettors was calculated to give a higher specific power output, due to the lower temperature, and hence greater density, of the fuel/air mixture, compared to injected systems. "Miss Shilling's orifice" (invented in March 1941 by Beatrice Shilling, an engineer at the Royal Aircraft Establishment, Farnborough), a holed diaphragm fitted across the float chambers, went some way towards curing the fuel starvation in a dive. Further improvements were introduced throughout the Merlins: 1943 saw the introduction of a Bendix-Stromberg pressure carburettor which injected fuel at 5 psi through a nozzle direct into the supercharger and was fitted to the Merlins 66, 70, 76, 77 and 85. The final development was an SU injection carburettor which injected fuel into the supercharger using a fuel pump driven as a function of crankshaft speed and engine pressures, which was fitted to the 100 series Merlins.[8][14] Production of the Griffon-engined Spitfire Mk. XII had begun the year before.

If Dobbo wasn't banned I'm sure he would have fun with "miss shilling's orifice"

Originally Posted by clean32

There were quite a few little differences that the yanks introduced to aid the manufacturing lines. The spur drive for the blowers are a bit simpler, less studs as pointed out, coil packs, rings\pistons, Valve size as is the head porting. UNF @ UNC instead of whit worth etc, hence the tool kit. A bit like DC3 and there stupid star lock screws.

as a rule the RRs had a bit more oumph but the yanks had the life.

As a side note, the poms first asked Mr Ford to build there motors, he declined because he thought that England would fall to the Nazis and that he wouldn’t get paid. Besides he was making more from building trucks for the Nazis.
As for the P51 being American, that’s a joke, the US army having been fleeced of most of there aircraft to be sold to the poms had a bit of a bitch up. So when the pomes wanted to purchase more P40s the army said Nope we want them all. so enters north American with there German Jewish engineers who were up until 18 months before were working for Henkel, ( check out Henkel’s companion to the ME109 elliptical wings and all and that 3 years before the spit). The only motor available was the Allison. From that we got the XP51 GROUND ATTACK. it’s fat laminar flow wings ideal to stand up to the low level buffeting required of close in ground support ( taxi rank, a Kiwi idea) ( aussies were back in the pacific around this time).
Any way the abrasive desert environment wasn’t very nice to the fabric of the hurricanes, no more P40s were showing up but XP51 were, problem no parts supplies for the Allison’s, no problem stuff a Merlin in and that was the unofficial birth of the P51. In reality the P51 only claim to fame is it wide undercarriage and its fuel capacity. they are a bit to stable to be a good fighter.

I can assure you that all Merlins used British threads. Personal experience. It was going to be too much trouble to re-draw thousands of engineering drawings to convert, as well as causing untold confusion and maintenance problems as soon there would have been a mix and match situation in the field requiring duplication of spare parts. I still have taps and dies made in the USA in WWII in British systems supplied to the allies for production and maintenance of aero engines. They used seldom encountered items like 5/32, 7/32, 9/32 BSF left and right hand. Left hand BA, and other monstrosities.

Ford told Rolls-Royce that they could not mass produce the engine using RR's tolerances. "Ha", said RR, "you rough motor car types can't work to our high standards". "No", replied Henry's men, "your tolerances are too wide for mass production. We require identical parts that can be assembled by unskilled labour, not selective assembly by skilled fitters matching parts by micrometers." So the tolerances had to be re-jigged and Ford's Manchester plant built by the British government at a cost of millions went into production.

RR had industrial problems in the Glasgow plant. They wanted women and boys to operate automatic machines like turret lathes etc. owing to a shortage of labour, the men having been conscripted into the forces. The Scottish industrial custom was that machines could only be operated by "time served" men, tradesmen, even if the machines were designed to be operated by process workers. The remaining men were reluctant to surrender hard won conditions. Eventually an agreement was reached that women and boys could operate machines for the duration of hostilities or until such times as tradesmen were available again.

Bendix-Stromberg referred to their fueling apparatus as the "anti-gravity carburettor". It was far and away the pick of fuel devices fitted to the Merlins of whatever mark.

It never ceases to amaze me (even at my age), that things I had just taken for granted turn out to be much more complicated that I realised.

From isuzurover's info:
Luftwaffe fighters could therefore 'bunt' into a high-power dive to escape attack, leaving the pursuing aircraft spluttering behind as its fuel was forced by negative 'g' out of the carburettor. RAF fighter pilots soon learned to 'half-roll' their aircraft before diving to pursue their opponents.

I imagine that most people like me had this idea that fighter pilots just jumped in their planes, opened the throttle and went up and shot down a few enemy aircraft.

It would never have occurred to me that they might have to do some sort of acrobatic manoeuvre at the start of an engagement just to make sure the engine didn't die on them in the middle of a dogfight.

How on earth did they ever concentrate on shooting down the enemy when they had so many other things to think about?

Very true.

Add to that, many of these pilots only had minimal experience (measured in tens of hours) and most were in their early 20's.

A lot to learn in a very short time.

It says a lot for "motivation".