So this may be a hair brained idea, but bear with me here. I was watching a show on the History channel about the restoration of a P-38 and at the end of the show they fired up the engines. My question is about the starter those old war birds use, or more specifically the sound they make. Your hear something start to wind up, without the engine turning over. Then the pilot flips a switch and that high pitched noise slows way down. The prop makes a couple lazy rotations, the engine fires once, then twice, then roars to life. Its such a cool sound, I had to rewind and watch it a couple time, but what causes it? Can someone explain the starting process? And how do I make my car sound like that at start-up without dropping the cash for an Allison(sp?) or Rolls-Royce Merlin?
they had delayed wind and shotgun starters. you can get the delayed type starter for flatheads too. or something similar .
I'm not 100% sure, but I think that they use a big inertia starter. An electric motor with a flywheel. I think your hearing that motor spin the flywheel up to speed before it engages the engine. That's a lot of mass to get spinning, lots of compression to overcome. Something a reasonably sized electric motor cant do by itself, like a car engine.
Scott got it right. Inertia starters were originally hand powered. If you watch early WWII movies, you will see mechanics insert a crank in the side of the fuselage behing the engine and usually two of them crank onit for all their worth. When they get it up to speed, they engage the clutch and get about two or three revolutions out of the engine before they have to start over. Sure wanted to keep them tuned up.
Thanks guys, Thats kind of what I was thinking, but would be hard to get to work on a automotive engine, lots of extra weight and packaging issues I've never heard of a delayed wind starter, anybody have more info on them?
There weren't any starters that could directly spin those high compression multi cylinder engines fast enough to start them. So they used a big heavy flywheel, turned it with an electric motor until it got up to "starting speed" and engaged a clutch that mated the inertia flywheel to the crankshaft and hoped it started.
So it is just a big flywheels inertia that does it. Thanks guys. Just thinking out loud here, I may have an idea how to pull this off, but its gonna require a lot of custom fab work. What about a starter gear in constant mesh with the engines flywheel, supported on each side with a bearing. Then use a clutch out of an auto trans or motorcycle. Have one side of the clutch hooked to the starter gear, and the other hooked to an electric motor from a standard automotive starter. Mount the motor housing to the trans bellhousing and support the clutch with bearings. Have some kind of hydraulic system to engage the clutch. To start, you put power to the motor and get it spinning, then activate the clutch, maybe with a master cylinder from a motorcycle connected to a small pedal. The clutch would engage, the electric motor would slow down, and the engine would turn over. I know it is a little too complicated and unnecessary for a hot rod, and I got a feeling I'm gonna get flamed for putting it out there, but I think the sound alone would be worth it.
If you ever get to watch the movie "Flight of the Phoenix", you'll see quite an extended scene where Jimmy Stewert finally gets a DC-3 radial engine started with a shotgun starter...
Gun powder starers where used by the British a lot probably because of lack of materials to build lelectric starters. This is a general description of the starter motor used on 1710 Allison V-12 aircraft engines Starting: Direct cranking electric starter motor composed of 28V series would electric motor with integral 3-stage planetary reduction gear (approximately 100:1 reduction gearing) engaging a dog geared (1:1) to the crankshaft. Booster coil employed to retard and increase ignition during low-speed cranking. Primer system consisting of one injector nozzle in each of the four legs of the rams-horn intake manifold, fuel being controlled by solenoid valve from the pressure fuel supply. Doesn't appear to be an interia starter?
Goes on a bit, but look at four minutes on and you´ll see how they did it. http://www.youtube.com/watch?v=4Y5LBUVS1T8
You're correct, not all piston powered aircraft did this. I'm just referring to the ones that make the sound he described.
This is a Coffman starter, used on many radials and most early jets. Used the charge from the cartridge to spin the rotating mass of the motor, pop on electric and you're away. These things are uber cool! Doc.
The sound mostly comes from the high speed of the flywheel, and without that component, your starter motor isn't going to make the same sound. But as noted in the citroen vid, you don't need much of a flywheel. In no way shape or form is my post intended to encourage your idea
This is a picture taken in 1928. The plane is a Fokker Tri Motor "The Southern Cross". Just before taking off from Oakland Calif. to cross the Pacific Ocean to Australia. The First Trans-Pacific Flight. The man Cranking the Wright-Whirlwind engine is James Warner, The Radioman on the flight, and my Father. The Pilot was Kingsford-Smith.
It was a radial engine............but it wasn't a DC3 (aka C-47), it was a B-25 "Mitchell" Bomber if I recall correctly......one of my favorite flicks......... Ray
!! WOW !! That is some family history. Did your Dad make any other significant flights on that bird? That was the only flight in the Southern Cross that my Father flew on. But Kingsford-Smith made a lot of significant flights in it. He was called at one time, "The world's greatest Aviator". The plane is in a Museum in Australia. You can find many references to him and the plane online. Google "James Warner Aviator" Or "Kingsford-Smith"
You are correct, of course........after reading your post I remembered the "boom" sections, trailing aft of the wings, geeesh........it's Hell getting old, first the memory goes........I don't recall what's next......
If you are thinking of a crashed B-25 in the desert, you might be thinking of the movie "Sole Survivor". http://www.imdb.com/title/tt0065007/
The C119 series had Coffman starters. The original flick wasn't bad but had some serious reality failings in the attachment of the port outer mainplane the the starboard boom root. Without serious machine work it wouldn't happen. Having said that in the original they did build one that flew, unfortunately it spun in killing the pilot. Thats who the movie is dedicated to. Doc.
There's some info on various starting systems on this page. http://www.enginehistory.org/accessories.htm And the rest of the site could keep you busy for a while. too.
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