Packard/merlin engines

[Ballistics in Scotland]

Very interesting engine, in this day and time it is remarkable that one basic engine design was successfully adapted to so many different applications..
And yes, Henry Ford was an odd duck as some folks would say. That's one of the reasons for his success.

I've seen the Meteor-engine tanks in the Tank Museum at Bovington Camp, and it makes for a fearfully crowded engine bay. Gasoline fuel is quite a liability too, with people taking shots at you, but those tanks were far from alone in that, at the time. It was also the engine around which Cultivator No. 6, a gigantic trench-digging machine, was originally designed, although Air Force demands produced a change to diesels.

It is easy to scoff at new inventions, and in this case easier than most. Cultivator No.6 would only have worked for a short time, and if surprise was maintained, before the enemy learned to plant the right sort of mines. But nobody knew, before the spring of 1940, that there were other ways of breaking through the stalemate of trench warfare.

Yes, Ford was peculiar, although he got more peculiar as he reached a position of not having to impress anybody. Who is to say how any of us would respond to such temptation? A psychiatrist on someone else's payroll might say he was quite seriously cracked. To be fair, he probably brought benefits to everybody - customers, workers, the country, underdeveloped rural areas. It is unfair to compare him with the great dictators, as some do. Even most of the Bolsheviki intended everybody to come round to seeing the benefits of their system, after being killed a little first. Only Hitler planned for a fair proportion of the population not to benefit under any circumstances.

[Don Purcell]

The marriage of the Merlin and the P-51 was a match like no other. One aspect that is overlooked is the design of the belly scoop of the P-51. Engineers at North American spent a lot of time adjusting the position of the intake for the best flow thru the radiator and the design of the exit ductwork. When they were finished it was determined that the heated and expanding air coming out the rear of the radiator and the design of the ductwork caused a sort of propulsion effect that when the Mustang was using full power that the jet effect was worth almost an extra 200 horsepower.

[smokeywolf]

I believe it was rumored that the later configurations of the P-51 reached the sound barrier in power dives. Not sure if that's possible, as it is said that the tip of the propeller is likely to hit the sound barrier before the rest of the aircraft.

[Harter66]

There was a super modified P51 called the Red Baron. It was Race number 5 . It was fitted with counter rotation propellers. It may still hold a closed course speed record a little over 512 mph .

You are.correct about the prop tips going super sonic first ,the effect being that that portion of the propeller blade effectively cavitates and stops making thrust.

While there was some venturi and heat exchange thrust created by the scoop design the exhaust side was only a narrow slit in cruise at altitude . Keeping in mind that it doesn't take a lot of air over a radiator when you have a temperature difference of 130-200 degrees between the engine coolant and air temperature. The racers removed the scoops in favor of hauling a cold reservoir because the added weight was less drag load than the slip stream drag of the scoop. If they were gaining 200 HP worth of thrust they would have figured out how to remove the drag while keeping the exhaust thrust.

12 years at Reno in the pits I learned a little here and there.

[fast ronnie]

There was a super modified P51 called the Red Baron. It was Race number 5 . It was fitted with counter rotation propellers. It may still hold a closed course speed record a little over 512 mph .

You are.correct about the prop tips going super sonic first ,the effect being that that portion of the propeller blade effectively cavitates and stops making thrust.

While there was some venturi and heat exchange thrust created by the scoop design the exhaust side was only a narrow slit in cruise at altitude . Keeping in mind that it doesn't take a lot of air over a radiator when you have a temperature difference of 130-200 degrees between the engine coolant and air temperature. The racers removed the scoops in favor of hauling a cold reservoir because the added weight was less drag load than the slip stream drag of the scoop. If they were gaining 200 HP worth of thrust they would have figured out how to remove the drag while keeping the exhaust thrust.

12 years at Reno in the pits I learned a little here and there.

Curious as to which planes you worked on. I do some stuff on Dreadnaught and the others from that shop. Also did a little work on Ridgerunner before it was retired from racing. They are working on an f4u right now. Going to be a long process on that one, but they are making good progress.

[Artful]

http://en.wikipedia.org/wiki/RB51_Red_Baron

[Harter66]

94 was my last season. I crewed Lickity Split ,Sheba, Miss Iris and Undecided.
I was there when Rare Bear buried 3 course records ,I still get goose bumps. 456 was amazing but 496 just ....... I can't describe the sensation. I always was a Bear fan except for the short life of the Super Corsair . Don't crop the wings if they plan on the big Pratt . That was the down fall of the Super Corsair, they couldn't hold full power in the turns ,it wanted to roll right.

[Artful]

[Loudenboomer]

Thanks for tribute to Bob Odegaard. All around good guy.

[Ballistics in Scotland]

The Rolls and Allison engines sound like a new hotrod ad actually.

Quad valves,double over head cams , dual ignition, nitrogen filled ignition cables or direct ignition spark , anti detonation injection, self regulating induction, some even had exhaust driven super chargers over gear driven centrifugal blowers. Pretty cool for 1939s finest.
Another time bit the p51 throttle was rigged with a bit of brass safety wire that prevented the pilot in normal operations from exceeding 75 inches of manifold pressure (2.8 atmospheres or 41 psi + engine consumption ) if the wire was broken the engine was replaced because the blower limit was 125 inches of mercury, just over 61 psi plus 3400 revs x 1760 Cid. kinda makes ya wonder how they kept the main bolts hooked to the aluminum blocks.

For aviation race application they are pulling over 100 inches in the lineup to start the fastest race and around 175 on the course,burning 150 octane leaded fuel and as much as 40 gallons of water as anti detonation injection and auxiliary cooling .

One feature of the P51 that made it a great fighter is that in full armour and fully armed it was a very unstable platform . Patrol pilots that didn't empty the guns often came home with the nose down trim all the forward and holding some nose down to maintain level flight. They were constantly on the trim controls I can imagine that with an aft tank in the airframe that they were very flight intensive .

Even those service P51s had a phenomenal level of boost, which surely depended on the use of 150 octane fuel. Battle of Britain Spitfires had 12psi authorized only as a five-minute emergency measure, and its use had to be reported afterwards by the pilot, for checking and possible overhaul of the engines. Later it rose only to (I quote from memory) about double that, under the same conditions, and I believe only some number in the thirties was tested. A supercharging system which was actually dangerous to puncture might do in air races, but not in combat.

Most of the great increase in power from the Merlin during its life was due to increased supercharging, rather than the parts that have to stand up to excessive use of supercharging. Strategic bomber escort duty doesn't happen from standby, any minute of any day, and the USAAF, late in the war, probably had far better facilities to service or change engines than the RAF during the Battle. Even in the late 70s (which was the last time I knew about it) the American system was to exchange engines or other units which the Royal Air Force would have repaired locally.

Mitchell learned to be a good aluminium man on biplane flying-boats. There is a photograph of the Supermarine Stranraer drawn up on the beach in Stranraer, with my grandparents' front door in the background, and it doesn't look modern enough for the mid-30s. But that was long after someone said "Suppose we race them?", and he had produced a single-purpose family of Schneider Trophy seaplanes. He came from just the reverse of those air-race P51s, getting more speed than all but the late Spitfires from seaplanes with lesser engines, and about as much frontal area in each float as the fuselage. The snag with those aerial concept cars "So why not build a Spitfire quickly?") was the very limited life and maintenance requirements of those engines. With fuel in the floats and the racing done at low altitude, supercharging was less critical and the wings could be made very thin. The Schneider seaplanes also cut drag by having the coolant pass between double skins on the wings and floats, an expedient which would have made one bullet hole disastrous for a fighter.

I doubt if any aeroplane can be made more manoeuvrable by the mere fact of being heavier, unless you use the weight to provide something useful. That rear tank in the P51 would surely have reduced maneouvrability, but the prime role of an air to air fighter had mutated from interception to bomber escort, in which they would deplete whichever tank was most advantageous, before contact with the enemy was likely. Horses for courses.

I also doubt if radiator heat could produce anything like the jet effect claimed for it. There may be some confusion here, as I believe late highly supercharged piston engines received quite a bit of jet effect from the exhaust. It was a step in the direction of the turboprop.

I remember the press reports in the 1960s when two British businessmen (not a team, but one starting where the other perhaps wisely left off) used a Meteor to power a custom car. As the Merlin was a British icon by then, the press naturally called the engine a Merlin. It wasn't called "The Beast" for nothing, and he was made to remove the Rolls-Royce logo and Spirit of Ecstasy mascot when they sued. It seems a trifle mean-spirited, when nobody was likely to suspect them of complicity in anything so terrifying. They did not have Bonneville in mind, but places with corners.

Another interesting snippet of information was that in a confrontation with Indonesia in the 1960s the Indonesians had single-seat piston engine fighters, P51s I believe. So the British did some combat testing with Spitfires and the English Electric Lightning, which was state of the art then, and at least fast a couple of decades later. They found that the Spitfire was best approached from below. Even with such a great advantage, more conventional fighter attacks weren't safe.

[Harter66]

The super chargers were more common in the high altitude bomber than the fighter being exhaust driven and taking a long time to spool up or down they were well suited to the stable nearly static power required at high altitude. The thumb rule is 3% per 1000 for power loss basically at 25,000 ft a piston carbureted engine won't run due to air starvation . Aviation cheats using ram air at 200 mph you gain ,assuming intake to consumption area rates are right an atmosphere so at 30,000 ft the 1000 HP 3350 Cid makes 500 HP so we add a 10-1 blower ratio and it comes up to 750 and the cylinders and carb think they are at 12,000 ft . With the exhaust driven super chargers added now the engine has its sea level 1000 HP back.

Flight stability is hard to explain if you have never had a hand on the yoke.
A very stable platform is like a big road car it soaks up the bumps and even at high speed is smooth and responds well to trim and fixed power settings it also is less load shift ,IE fuel consumption,and while it is capable of quick changes in direction it prefers "40 acres". An unstable platform requires constant attention to trim throttle adjustments, especially if it is in any sort of formation kind of like driving a full blown rally/SCCA car that carves every turn and you feel every Crack and pebble in the road . The P51 was like the latter as little as a 5 gallon change in fuel would have a pilot on escort adjusting the trim that Rolls sucks up around 30gal/hr in a 200 mph cruise with the bombers feeding from a tank 5ft behind the lift center, the stick was probably getting nose heavy every 7-10 minutes . The pilot rolls some nose up an gets a comfortable stick loading in his palm and 5 min later it's out of the neutral loading and pushing against his fingers,retrim. All the while the indicated air speed has fallen off to 192 and climbed back to 205. If he was the outside man under the bombers there's a good chance that he feels like he's running down a farm road on a dry day in and out of the air wakes of the bombers and his own flight plus throttle changes and more trim changes to stay in formation . Get into combat mono amono, that all changes he made a tank switch to the full aux tanks at lift center the trim is forgotten at a neutral point and the throttle is up around 90% the platform can be in a 45* bank and or dive or climb at 400 mph and still be pushed into or out of yaw for shooting windage and then flipped into a reversed position in just a hair under a second. They also had the ability to slam on the breaks in a cross controlled maneuver forcing the other guy to break his line and then accelerate back to fire again ,maybe. Because of the heavy high power design they could also out dive an enemy to escape. Late in the war there is a story of a P51 pilot being out matched and rolling into the break away escape dive only to look out his side and see the Me109 pilot smiling back and diving away into a breaking climb and disengagement. By then the Me 109 was sporting over 1900 HP in an 5000 lb combat ready airframe while the P51D was running just 2100 in combat read airframe close to 8000 lbs (Corsairs were where I knew them front to back pardon errors numbers are approximate and of good ratio).

On the race course the Merlin is pulling closer to 3500 HP some even more.

There is an F8F Bearcat "Rare Bear" that runs the 4350 Pratt and Whitney with a 2 stage blower . The yrs that they had great sponsors they built an engine that produced a baseline of 3400 HP and a step to a call at ed 4200 when the high altitude blower stage was engaged. This design allowed the war birds to launch from a carrier at maximum throttle and climb to 10,000 ft with only about a 10% power loss and carry sea level proformace to 25,000 ft and get there in 18 min. Rare Bear also had a nitrous plate that boosted it to some estimated 4600hp . There was a delay built into the switching that turned on cooling spray bars in the cowling the a 7psi open flow fuel line with 2 1/4 inch lines into the intake below the carb before the NOS hit it . It could run for 7 seconds per shot as long as the shots were more than 45 seconds apart. Before the NOS system he set a course win record at 456 and change with a cleaned up much modified P51 called Strega at 43? in 2nd. The next year Strega finished 2nd at 24? and RB set a 458 in qualifing 463 in heat 1 , 47? In the 2nd heat race and 496 for the big money.

The Snider cup racers as sea planes were actually faster than their land based sisters the floats actually carried there own weight and we're rigged to carry in high load (thus lower drag) the wings could then be flattened to carry their load at a higher loading and lower drag as well.

I believe that the "golden age" of racing and design development was probably from about 1925 to 1938 what was learned in those yr has been applied over and over in design aerodynamics and engines ,electronics have only allowed the outer or upper limits to ride the razors edge. I imagine dozens of blown engines could have been saved by digital management . Who turns to see what came around the corner when it's a 14' 400 HP Mustang? Just try to look away from a 500 horse 68 Daytona Road Runner , I dare ya.

[Artful]

The Beast

[Harter66]

http://youtu.be/SIj2GVfua84

[Harter66]

http://youtu.be/6SRhOQ7_Yfc

Rare Bear.

[castalott]

I believe it was rumored that the later configurations of the P-51 reached the sound barrier in power dives. Not sure if that's possible, as it is said that the tip of the propeller is likely to hit the sound barrier before the rest of the aircraft.

the p38 was so clean it could hit the sound barrier in a dive...The latest models had dive brakes for just such an emergency as the controls locked up in a fast dive. That's what I've read anyway....

[Harter66]

It actually became a victim of control reversal . The non technical description is that at transition speeds the normal down thrust tail plane lift would become up thrust so to get out of the dive ,remember that in the dive the controls are neutral the pilot had to actually push forward (down )to raise the nose . Weird things happen to air planes at transsonic speeds. Even the Jets of today have a tiny window of non responsive controls when they go to or from super sonic speeds. Something to do with shock waves.

[Loudenboomer]

Merlin = Music! Gotta love that sound! Especially the ones with the wick turned way up. Sense the hey day of piston aircraft getting a good fuel has been a problem unless on a serious race budget. Pump 130 octane just is not available like it was in years gone by. My first job in the Air Force was an engine mech. on a C-131. Twin Prat R 2800's. We flew that until the mid 80's. The only fuel available to us was 100 octane LL. With out Alcohol water injection we would detonate the engines and could not run enough manifold pressure to get the old girl off the ground. Injecting about 55 gal of fluid on take off and initial climb out and we were golden.

[Harter66]

Boomer ,
I don't suppose you still know the fuel grade color poem ? Red,blue,green ,purple for 80,100,130 ,150..... run boys.....

[Bad Water Bill]

That "blue goose" worked great for everyones Zippo lighters.

[Loudenboomer]

66 I forgot all about the fuel song code until you mentioned it. I'll never forget counting the prop blades go by then sparking up 2800 cubic inches at a time. If that don't make a farm kid that's nuts about flying grin nothing will.