Enzo Posted May 24, 2017 Share Posted May 24, 2017 (edited) A Merlin is a Merlin, It doesnt matter if its a boat or not, Its not a question of the "Procedure" or "Configuration". Its a Question of will the Merlin ignite with only the booster coil. which i read as no because its hooked to the Distributor. no mags on no volts to the distributor. Drag boat guys were stupidly notorious for blowing Merlin's up left right and center so id say they have a pretty intimate relationship with the motor. I have also sent the Question to a real P-51 pilot Scott Yolk of Quick Silver. Edited May 24, 2017 by Enzo Link to comment Share on other sites More sharing options...
ED Team Yo-Yo Posted May 24, 2017 ED Team Share Posted May 24, 2017 (edited) "Ignition: Ignition is by two high-tension rotating magnet magnetos mounted on each side of the wheelcase. The "A" bank magneto serves the intake spark plugs and the "B" side magneto serves the exhaust spark plugs. The magneto has an integral coil and breaker points operating off a four pole cam, each magneto is driven by a serrated coupling shaft turning at 1.5x engine speed. A distributor turning at 1/3 the magneto speed provides one complete cycle of 12 sparks every 2 revolutions of the engine. Provisions exist for an engine control mechanism to move the breaker base through 25 degrees of advance. In addition, the distributor features a two contacts on its rotor -- the leading finger is energized by the magneto and the trailing finger by an external terminal which can be connected to a booster coil to facilitate starting. The booster coils are essentially high tension coils with vibrating points which provide continuous spark -- when applied to the retarded finger they provide a high energy retarded spark which can greatly facilitate starting, especially with cold, slow turning (thick oil) engines which don't provide much speed for the magnetos. Merlins in aircraft only boosted the "A" bank, but I've seen boats with no boost, with booster coils on both banks, and both combinations in between." "Starting: Electric starter motor composed of 24V series wound electric starting motor engaging reduction gear at bottom of wheelcase (motor mounted vertically). The geartrain provides a reduction more than 104:1, and includes a safety clutch and a modified Bendix-type mechanism to protect the drivetrain and related components from excessive torque and to allow the starter to disengage while the engine is running. Booster coils are employed to retard spark and increase ignition during low-speed cranking. Primer system for direct injection of fuel through atomizing nozzles into intake manifolds provided." In Short, the Booster coil retards the spark and increases ignition for starting. The booster coil is on "A" Bank or the intake side, and Both A and B are powered by the mags, if the mags are OFF there is no spark, thus as an A&MP put it so greatly, No Sparky Sparky, No Bang Bang. http://thunderboats.ning.com/page/rolls-royce-merlin-v1650-engine Source. Negative. If you tried to look at the schematics diagram you would see that THERE ARE NO SWITCHES in the HV side of the magnetos. High voltage from the booster coil goes to the right magneto HV circuit directly through the spark gap then to the distributor. So, the booster coil is independant on magneto switch. Edited May 24, 2017 by Yo-Yo Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles. Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me Link to comment Share on other sites More sharing options...
Pzkfw Posted May 25, 2017 Share Posted May 25, 2017 It is to pre-prime the oil galleys so the oil pressure on startup is not zero for a few seconds. Keep in mind oil pressure is usually measured at crank journals so even if that takes a few seconds to read pressure, the cams etc are not getting pressure for a few seconds even after that. It is debatable if it is strictly necessary as long as the engine has been run some time recently and ambient temperatures are not extreme, as oil forms a film on the parts they are protected for the few seconds without oil pressure. It is still good practice and is "seat of the pants" engine-building and engine-maintaining knowledge. AKA Venturi "You can tell a bomber pilot by the spread across his rear, and by the ring around his eye, you can tell a bombadier; You can tell a navigator by his maps and charts and such, and you can tell a fighter pilot - but you can't tell him much!" -523 TFS Fighter Pilots Song Book Link to comment Share on other sites More sharing options...
Pzkfw Posted May 25, 2017 Share Posted May 25, 2017 BTW ed tester, cylinders run dry except for splashing of oil from crank. AKA Venturi "You can tell a bomber pilot by the spread across his rear, and by the ring around his eye, you can tell a bombadier; You can tell a navigator by his maps and charts and such, and you can tell a fighter pilot - but you can't tell him much!" -523 TFS Fighter Pilots Song Book Link to comment Share on other sites More sharing options...
sobek Posted May 26, 2017 Share Posted May 26, 2017 (edited) No Sparky Sparky, No Bang Bang. As Yo-Yo has outlined, have a look at the circuit diagram. It is less open to your interpretation than a textual description. Although i admit that if you're trained to read current circuit diagram symbols, the arcane style of that diagram can be a bit of a brain teaser. Edited May 26, 2017 by sobek Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives! Link to comment Share on other sites More sharing options...
Frederf Posted May 27, 2017 Share Posted May 27, 2017 It sounds like starter engages ignition bypass circuit and during starter operation there is ignition. Keeping the magneto switch off initially means that there is no ignition in absence of starter operating (let go of starter, ignition dies = safety). That makes perfect sense (not the same as true) to me that why would you have starter motor operating without ignition. Not spectacularly related but I'm curious if the bug (assumed) has been addressed where if you prime before the propeller has moved 0.00000001° it won't start but if you move the propeller 0.00000001° and then prime while stationary then it will start. I cannot think of any reason why one should work and the other not. Either they should both work or both not but producing different results seems crazy. Link to comment Share on other sites More sharing options...
sobek Posted May 27, 2017 Share Posted May 27, 2017 Never heard of that bug. Sounds like a faulty init state of the engine model that gets corrected once the prop moves. It has definately been fixed. Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives! Link to comment Share on other sites More sharing options...
Art-J Posted May 27, 2017 Share Posted May 27, 2017 I confirm, they fixed that one allright a couple of patches ago. i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10. Link to comment Share on other sites More sharing options...
NeilWillis Posted May 27, 2017 Share Posted May 27, 2017 A Merlin is a Merlin, It doesnt matter if its a boat or not, Its not a question of the "Procedure" or "Configuration". Its a Question of will the Merlin ignite with only the booster coil. which i read as no because its hooked to the Distributor. no mags on no volts to the distributor. Drag boat guys were stupidly notorious for blowing Merlin's up left right and center so id say they have a pretty intimate relationship with the motor. I have also sent the Question to a real P-51 pilot Scott Yolk of Quick Silver. What utter bunkum! In an aero install, the ancillaries can and will be entirely different to a boat install. To make assumptions like this are exactly the way to utter confusion and misinterpretation. The fact that the drag boat boys are great at blowing up Merlins says it all! And as others have added, you are utterly incorrect regarding the mags and booster coil configuration too. Perhaps turning it over without the fuel cocks on will give you a better chance of not prematurely running the engine - plus you'll avoid cylinder wall washing with raw fuel too, which is never a good thing. Link to comment Share on other sites More sharing options...
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