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junkers2006
10-08-2006, 11:06 AM
hi! can someone explain this!
in game or real life when i push the engine button, the engine propeleer start slowly rotating, after few seconds the propeleer quickly spins up and the smokes comes out of engine! why is it so?
why does the plane engine cannot be started like car engine?

Snodrvr
10-08-2006, 11:37 AM
An airplanes engine is a lot heavier than a car engine, It would take a much bigger battery to get an aircraft engine rolling enough to start. That's why in WW1 you saw the ground crew spinning the props by hand to start the engines. In WW2, I believe they switched to using an electric "Jumpcart" to start the motors by providing electricity to some of the engines, and others which were started using a loop that was placed over the propeller and then rapidly drawn back using a device of some sort, doing the same job the WW1 ground crew was doing, but doing it with much more force and quite a bit safer.

I guess it boils down, to being better for the planes to not have carry all that extra weight, when they had options availible.

Nowadays, the modern jets can be started much like a car engine, allowing for a quicker scramble time should an emergency arise.

You'll have to ask someone else for the exact specifics, Im not an expert and some of the facts about starting processes in WW2 may be slightly inaccurate.

WB_Outlaw
10-08-2006, 11:47 AM
Most engines with electric start slowly spun a heavy flywheel. The flywheel was seperated from the crankshaft with a clutch. When the flywheel was spinning fast enough, the clutch was engaged and it started the motor. This allows the use of a small electric motor instead of a giant one.

Hand starts that use a crank, like the 109, were the same thing except that the flywheel was spun by hand with the crank.

Some engines used a shotgun like cartridge (just propellant) to start the engine. It only fired into one cylinder and the prop was turned by hand until the piston was at top dead center. When the cartridge fired it pushed the cylinder down and hopefully started the engine.

--Outlaw.

junkers2006
10-08-2006, 12:31 PM
thanks! now i get it!

killer2359
11-01-2006, 02:08 AM
The whole answer simply boils down to this: to spin over any engine you have to apply enough force to rotate it - opposing this force is the cylinder compressions and the rotational mass of the engine - this is in large part made up of the FLYWHEEL. In a car engine - even a big one - you might be looking at a flywheel of 11 or 12 inches weighing maybe 10 to 20 kg ........... a ww2 plane engine has a flywheel of something like 7 feet or more weighing over 100kg!! - it's physically impossible to kick over such a large mass as quickly as a car engine.<div class="ev_tpc_signature">

sudden and silent

major_setback
11-01-2006, 06:08 AM
As I understand it: the combustion chambers of the engine fire in sequence, and these, by pushing the pistons, rotate the engine. This works fine once the engine is rotating (the pistons firing in turn keeep it going). However the cranshaft has really to be rotating to start with. The flywheel/cartridge described in the above posts are used to get the initial rotation of the crankshaft going enough for the engine to coninue in it's cycle.


Also the crankshaft rotation itself compresses the petrol vapour in the cylinders before ingnition.
The engine is designed to keep going once it's started, it needs help with that start though.



I hope I'm right in the above, I'm not mechanically minded so please correct me if I'm wrong. This is just how I percieve it working.<div class="ev_tpc_signature">

http://i4.photobucket.com/albums/y129/major-setback/B17sig11LowResPlane2.jpg (http://i4.photobucket.com/albums/y129/major-setback/Editthisnov06a003k1800xLaterimprove.jpg)

Chuck_Older
11-01-2006, 10:08 AM
close enough http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif They fire in a sequence, called firing order, but it doesn't go 1-2-3-4-5-6-7-8-9, it is staggered and depends on a few things, like the number of cylinders, the arrangement of the engine, and the number of strokes per cycle

killer2359
11-01-2006, 11:43 PM
Yes, that is indeed the basic theory of piston engines - the point is that a car engine is able to turn over very relatively quickly to get running (start) - but the aeroplane engines as depicted in Pacific Fighters have huge propellers hanging off them which are somewhat more difficult / slower to get turning initially and up to a speed where they can start to run. I've been answering the original poster's question - ie. why do the plane engines begin turning over so much more slowly than a car engine - this I have answered (I am an Aircraft Mechanic by trade you see).<div class="ev_tpc_signature">

sudden and silent

Waldo.Pepper
11-02-2006, 03:19 AM
So there are no hamsters involved at all then.<div class="ev_tpc_signature">

http://img.photobucket.com/albums/v516/WaldoPepper/sig/p61rev.jpg

x6BL_Brando
11-02-2006, 04:32 AM
So there are no hamsters involved at all then.

Not even jet-powered ones http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Here's the spec for the Rolls-Royce Merlin V1650
Firing Order 1A-6B-4A-3B-2A-5B-6A-1B-3A-4B-5A-2B, (where A & B are the two banks of the V-12 engine)

The rest of the specs are here (http://www.unlimitedexcitement.com/Pride%20of%20Pay%20n%20Pak/Rolls-Royce%20Merlin%20V-1650%20Engine.htm#Top) . You will note that the engine came with a 24 volt starter motor, with a reduction of 104:1 - but count the number of ancillary systems that are being turned by that starter in the first instance. Not to mention the propeller!

Several variants used the Coffman (cartridge) starter - mainly for Navy use. I don't know why - perhaps starters & starter-trollies were unusable in the presence of seawater?

B.

killer2359
11-03-2006, 11:18 PM
Yep - in all the whole process hinges round fairly hefty reduction gearing to get things turning - be it by electric or physical mechanical means - so the initial result at the prop is slow rotation to begin with.

Hamsters are problematic in that there's never been a successful system devised to ensure they run the correct way - and for naval ops they're totally unsuitable as they get seasick very easily.<div class="ev_tpc_signature">

sudden and silent

WOLFMondo
11-04-2006, 04:43 AM
Originally posted by x6BL_Brando:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">So there are no hamsters involved at all then.

Not even jet-powered ones http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Here's the spec for the Rolls-Royce Merlin V1650
Firing Order 1A-6B-4A-3B-2A-5B-6A-1B-3A-4B-5A-2B, (where A & B are the two banks of the V-12 engine)

The rest of the specs are here (http://www.unlimitedexcitement.com/Pride%20of%20Pay%20n%20Pak/Rolls-Royce%20Merlin%20V-1650%20Engine.htm#Top) . You will note that the engine came with a 24 volt starter motor, with a reduction of 104:1 - but count the number of ancillary systems that are being turned by that starter in the first instance. Not to mention the propeller!

Several variants used the Coffman (cartridge) starter - mainly for Navy use. I don't know why - perhaps starters & starter-trollies were unusable in the presence of seawater?

B. </div></BLOCKQUOTE>

Trollies were probably a pain in the *** on a rolling deck!<div class="ev_tpc_signature">

Cheers!!