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Machine Elf
09-08-2009, 12:09 PM
A car comes equipped with an electric starter. Simple deal: battery powers an electric motor that spins the engine up to some speed where combustion can take over and bring things up to a steady idle RPM.

18-wheelers, I believe, typically have two options:

1) electric starter as described above, or
2) air-start. The have compressed air on board for operating the air brakes, so they can use this to spin the engine. Unclear whether some special valvetrain management is needed, or whether (on an in-line 6-cylinder) there's always going to be at least one cylinder with its intake valves open, and so you can just pressurize the intake manifold and start spinning.

So how about diesel locomotives, with displacements on the order of 120 liters (your car is more like 2-5 liters)? It would take a humungous electric starter and battery to spin this engine over. Barring that, do they have compressed air on board for any purpose? Moreover, do they have enough compressed air on board to start the engine?

Finally, take it all the way to the limit: large-scale, marine diesel engines (http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C), with displacements up to 25,000 liters. My understanding is that these engines are almost never shut down unless something is seriously wrong with them. because they're capable of extremely low-speed operation (I'm talking about single-digit RPM's), it's even possible to completely overhaul one cylinder at a time without shutting down the engine. But at some point, somehow, they must have started the engine, and they must have the capability to do it again if they ever shut it down. Anyone know how?

Nunavut Boy
09-08-2009, 12:36 PM
I don't know the answer, but here (http://people.bath.ac.uk/ccsshb/12cyl/) are some pictures of the most powerful diesel engine in the world. It's HUUUUUUUUGE!

t-bonham@scc.net
09-08-2009, 12:39 PM
So how about diesel locomotives, with displacements on the order of 120 liters (your car is more like 2-5 liters)? It would take a humungous electric starter and battery to spin this engine over. Barring that, do they have compressed air on board for any purpose? Moreover, do they have enough compressed air on board to start the engine?They certainly have compressed air on board -- that's what powers the whole braking system for trains! And given the amount needed for that, I suspect it would be enough to start the engine.

Also, those are diesel-electric locomotives. The diesels just power electric generators, which charge batteries that power electric motors that drive the wheels. So they have a real big supply of electricity stored in batteries onboard. Certainly enough to power an electric starter for the diesel engines if they did it that way.

Tully Mars
09-08-2009, 12:51 PM
I serviced an older Caterpiller dozer years ago that had a two cylinder gasoline engine that was pull-rope-started. When you had the two-cylinder running, you used a hand-actuated clutch to turn the big diesel engine.

GusNSpot
09-08-2009, 01:08 PM
Big engines are almost always 'air' start now days....

johnpost
09-08-2009, 01:09 PM
Also, those are diesel-electric locomotives. The diesels just power electric generators, which charge batteries that power electric motors that drive the wheels. So they have a real big supply of electricity stored in batteries onboard. Certainly enough to power an electric starter for the diesel engines if they did it that way.

why would there need to be batteries which add weight and loose energy? the generators power the motors directly (with control and rectification in between).

t-bonham@scc.net
09-08-2009, 01:24 PM
why would there need to be batteries which add weight and loose energy? the generators power the motors directly (with control and rectification in between).The batteries store the electric power.

The diesel engines are set to run at a constant, most-efficient speed. But the energy needed by the train varies, depending on whether they are accelerating, going up a hill, down a hill, coming to a stop, etc.

Machine Elf
09-08-2009, 01:54 PM
The batteries store the electric power.

The diesel engines are set to run at a constant, most-efficient speed. But the energy needed by the train varies, depending on whether they are accelerating, going up a hill, down a hill, coming to a stop, etc.

Even if the engine is held at constant RPM, the fuel injection can be varied to meet load demand. Not only is there no need of batteries for this purpose, but it would be impossible to carry enough battery capacity in the locomotive to meaningfully affect the performance of the train as a whole. I suppose a battery may be present for starting purposes, but as has been noted (I don't know why I didn't realize this :smack:), a locomotive will have a ready supply of compressed air on board for brake operation, and so an air-start is a trivial add-on.

Big engines are almost always 'air' start now days....

It's still not certain to me that this is the case for the super-big marine diesels. Locomotives and OTR trucks have compressed air systems for braking purposes, but what about the big container ships? And if they do have compressed air available, wouldn't it take a freakin' humungous tank of it to get an engine spun up?

VunderBob
09-08-2009, 02:07 PM
Back in the days of DC generators and electrical systems, a diesel locomotive was started by running battery current throught the generator itself, making it a DC motor.

Modern, Tier 3 compliant diesels are air start. A dead locomotive with the air bled off requires another locomotive or an external air compressor to charge the reserviors.

The batteries store the electric power.

The diesel engines are set to run at a constant, most-efficient speed. But the energy needed by the train varies, depending on whether they are accelerating, going up a hill, down a hill, coming to a stop, etc.

Unless you're talking about the Green Goat style switchers based on hybrid technology, this is baloney. There ain't enough battery made to do this in the standard long haul locomitive you see pulling a train. Batteries in those serve much the same purpse as those in IC cars and trucks, power when the engine is not running, not propulsion.

Xema
09-08-2009, 02:07 PM
The batteries store the electric power.
The diesel engines are set to run at a constant, most-efficient speed.
Various Googling suggests that storage batteries are not common in trains. As JFF notes, they would certainly have to be big, heavy and expensive in order to store train-scale amounts of useful energy.

Whack-a-Mole
09-08-2009, 02:10 PM
The batteries store the electric power.

The diesel engines are set to run at a constant, most-efficient speed. But the energy needed by the train varies, depending on whether they are accelerating, going up a hill, down a hill, coming to a stop, etc.

I recall asking this here a long time ago (and forget the answer) but seems to me when a train is accelerating with a big load you can hear the rumble of the diesel engines get low and strained. You can feel/hear the engine struggling. If the engine could just run at a constant speed this would not be the case. You'd just hear one constant hum from the engine regardless of what the train was doing. Somehow the effort of the electric motors goes back to the diesel engine making it struggle (which I think was my question ages ago...how did this effort translate through the electric motors to make the diesel strain?).

ETA: Here is the thread where I asked about this: http://boards.straightdope.com/sdmb/showthread.php?threadid=63293

Xema
09-08-2009, 02:14 PM
... but what about the big container ships?
One scheme I've read about involves a relatively small motor that slowly (say, over the course of 20 seconds or so) cranks one cylinder up to full compression. When this cylinder is fired it kicks the whole engine to life.

Not sure how common this is.

VunderBob
09-08-2009, 02:16 PM
I recall asking this here a long time ago (and forget the answer) but seems to me when a train is accelerating with a big load you can hear the rumble of the diesel engines get low and strained. You can feel/hear the engine struggling. If the engine could just run at a constant speed this would not be the case. You'd just hear one constant hum from the engine regardless of what the train was doing. Somehow the effort of the electric motors goes back to the diesel engine making it struggle (which I think was my question ages ago...how did this effort translate through the electric motors to make the diesel strain?).

The principle invloved (I forget the name, and I'm an electrical enginer; shoot me) is that electrical power isn't free. if you need a kilowatt to run a load, you need to generate a kilowatt plus the transmission losses to deliver it. Therefore, should the traction motors on the locomtive bog down under load, the increased load will be transmitted back to the alternator, and in turn slow down the prime mover, which you hear.

Sunspace
09-08-2009, 02:33 PM
So are those giant marine diesel engines built in place, and they build the rest of the ship around them?

Fastidiots
09-08-2009, 02:45 PM
So are those giant marine diesel engines built in place, and they build the rest of the ship around them?IIRC, built in your Gigantic Engines and Such Factory (GESP), disassembled, shipped to the wharf (with engine assembly crew), reassembled, then lowered into the beast. Life!

SpectBrain
09-08-2009, 06:45 PM
with compressed air. Information from this very interesting site: http://www.brighthub.com/engineering/marine/articles/41105.aspx

Snnipe 70E
09-08-2009, 08:43 PM
They certainly have compressed air on board -- that's what powers the whole braking system for trains! And given the amount needed for that, I suspect it would be enough to start the engine.

Also, those are diesel-electric locomotives. The diesels just power electric generators, which charge batteries that power electric motors that drive the wheels. So they have a real big supply of electricity stored in batteries onboard. Certainly enough to power an electric starter for the diesel engines if they did it that way.


Diesel electric trains do not have batteries for the prime mover.

Snnipe 70E
09-08-2009, 08:46 PM
The batteries store the electric power.

The diesel engines are set to run at a constant, most-efficient speed. But the energy needed by the train varies, depending on whether they are accelerating, going up a hill, down a hill, coming to a stop, etc.

You ever hear a train start the engines will rev up at it starts to move. The output of a generator running at a constant speed will vary according to the load, no batteries are needed.

Snnipe 70E
09-08-2009, 08:49 PM
One scheme I've read about involves a relatively small motor that slowly (say, over the course of 20 seconds or so) cranks one cylinder up to full compression. When this cylinder is fired it kicks the whole engine to life.

Not sure how common this is.


This method was used on some old fishing boats usually 2 or three cylinders.

Snnipe 70E
09-08-2009, 09:09 PM
Finally, take it all the way to the limit: large-scale, marine diesel engines (http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C), with displacements up to 25,000 liters. My understanding is that these engines are almost never shut down unless something is seriously wrong with them. because they're capable of extremely low-speed operation (I'm talking about single-digit RPM's), it's even possible to completely overhaul one cylinder at a time without shutting down the engine. But at some point, somehow, they must have started the engine, and they must have the capability to do it again if they ever shut it down. Anyone know how?


Excluding diesel electric ships or ships with variable pitch props, a marine diesel engine is directly coupled to the prop shaft. To change speed of a ship the engine's rpms are incrreased or slowed down. A slow bell might be 20 RPM with a full ahead bell being around 120 RPM.

The engines are started with high pressure air. Each cylinder will have a valve just for starting air. If the prop is not turning then the engine is not turning. If the ship is on any ahead bell and a reversing bell is given, the engine is stopped the valve guides lifted, the cam shaft is shifted to the reverse position, the valve guides are dropped and starting air is introduced into the clinders. When the engine is up mim rpms the air valves are closed and the injectors begin operating.

If a cylinder needs to be worked on the engine is stopped first, woth a pistion and valves moving you can not work on a cylinder.

Air is provided through air compressors and air tanks. Some of the older ships had an air compressor built into the main engine with auxalliary compressors.

When manuvering into port some times a ship can get a show boat Mate or Captian who likes to use a lot of bells forward and astern. If too much air is being used the engineering watch officer will call the bridge and tell them that they have only so many more ahead to astern bells that they can do in the next 20 minutes. If the bridge exceeds the number and uses all the air the enginroom will ring up STOP, and call the bridge and tell them that they will not be answering bells for the next time period. When the air pressure is back up they will ring up stand by engines.


Normally the engine is assembled as the ship is being built.

Snnipe 70E
09-08-2009, 09:11 PM
As a side bar, before computers the way pistion rings were inspected is someone would climb into the intake chamber and the engine was rotated with jacking gear until the pistion rings were at the intake ports. This on a two cycle engine.

Kevbo
09-08-2009, 10:03 PM
Another method is inertial starting: A hand crank, or an electric motor spins a flywheel up to very high speed, then a clutch is engaged, which couples the flywheel through gearing to turn the motor. The hand-crank version was fairly common on large radial aircraft engines. I have had the pleasure of cranking a Stearman up with this. It would not have been a pleasure if the pilot wasn't well practiced in priming and throttle manipulation, requiring more than one spin-up of the flywheel.

Magiver
09-08-2009, 10:07 PM
Gasoline engines can be started by injecting and igniting gas in the cylinder that is read to fire. I don't know if any cars are using the technology but it's been talked about for years.

If a diesel engine uses a common rail fuel system with pressures of 26,000 psi I see no reason why it can't be done on a large diesel. they would have to have an ignition source added just for starting.

Princhester
09-08-2009, 11:35 PM
My understanding is that these engines are almost never shut down unless something is seriously wrong with them.

What Snnipe 70E said. This is dead wrong: not only are they regularly shut down, they are shut down several times in the course of a single berthing manouevre as the master/pilot call for ahead/astern movements. More starts than planned usually happens when something is going wrong.

When something is already going wrong and then the engine room calls "only three more starts, Captain" up to the bridge the tension goes up a notch.

Happy Fun Ball
09-09-2009, 12:20 AM
I serviced an older Caterpiller dozer years ago that had a two cylinder gasoline engine that was pull-rope-started. When you had the two-cylinder running, you used a hand-actuated clutch to turn the big diesel engine.I have seen this setup also. The gasoline engine was called a pony engine and it would be used to start the diesel. The diesel was from a WWII tank IIRC and was installed in the boat I was on shortly after the war. The boat was a Chesapeake Bay buy boat, and was sail powered before the engine was installed.

The principle invloved (I forget the name, and I'm an electrical enginer; shoot me) is that electrical power isn't free. if you need a kilowatt to run a load, you need to generate a kilowatt plus the transmission losses to deliver it. Therefore, should the traction motors on the locomtive bog down under load, the increased load will be transmitted back to the alternator, and in turn slow down the prime mover, which you hear.Conservation of Energy? Bang!

VunderBob
09-09-2009, 05:01 AM
Conservation of Energy? Bang!
It's named for somebody.

Deereman
09-09-2009, 05:14 AM
Small gasoline engines were used to crank over hard starting large diesel engines, back when the electric starters weren't up to snuff.

They're usually called pony starts, donkey engines, or cranking engines and were used on John Deere diesel tractors from 1949-1960. Tiny opposed two cylinder engines or tiny V4s, depending on the tractor.

And on Caterpillars too, as was mentioned

Here is a video of a pony start Deere, being started:
http://s108.photobucket.com/albums/n8/weirddeere/?action=view&current=70DStart.flv

kferr
09-09-2009, 07:22 AM
I used to work at a natural gas compressor station where the engines were HUGE! We had 7 engines, six were straight 7's and one was a V-8. The size of the pistons was between the size of a beer keg and 55 gallon drum. The fuel was the same natural gas that they were compressing and they were all started on air.

Tully Mars
09-09-2009, 08:00 AM
I used to work at a natural gas compressor station where the engines were HUGE!

Like this (http://farm4.static.flickr.com/3542/3399904561_021ea80bf5_b.jpg)? This one is air-started. The air starter makes a high pitched whine that sounds almost like a siren when it starts. The woods in East Texas are littered with these things now and you can hear the starters go "whiiiirrrrrr" from miles away when they start one up.

BlakeTyner
09-09-2009, 12:49 PM
Here's a youtube video of a locomotive starting, taken from inside the engine compartment. Scroll to about the 4 minute mark for the actual startup. It's an older locomotive, but the concept remains basically the same (modern locomotives often have an engine start button in the cab that automates the fuel priming, etc.)

It's done off of battery power.

As mentioned above, except in very specific circumstances, the batteries do not provide any propulsion.

Starting a Locomotive (http://www.youtube.com/watch?v=bNR8dYzeCkc)

gotpasswords
09-09-2009, 12:58 PM
How much of a market remains for those gigantic engines?

I don't know about container freight ships, but cruise ships have been diesel-electric for some time now, and the newer ones have an array of small engines so they can only run as much engine as they need to support the current (hah, bad pun...) demands of both the "hotel" load (basically, all of the human comforts above the water line) and propulsion.

The ship I was on earlier this year had something like two 8-cylinder engines and three 16-cylinder engines which let them trim their fuel usage anywhere along the range of full power on down to just enough to keep the lights and climate control running while docked.

Whack-a-Mole
09-09-2009, 02:09 PM
How much of a market remains for those gigantic engines?


Apparently a lot.

The huge engine linked above is a pretty new design. I presume they would not have gone to the expense had there not been a market.

It is stated in one of the above links that people who run container ships prefer a single engine, single propeller design. I presume the whole thing driving this are cost of operation concerns and I am guessing one engine/propeller is cheaper to operate than two or more.

They also note that the huge engine above is actually very fuel efficient. Another cost savings.

I would suppose a cruise ship might have other concerns. A single engine is a single point of failure. More than one engine is probably a good idea for those.

Pushkin
09-09-2009, 02:47 PM
I serviced an older Caterpiller dozer years ago that had a two cylinder gasoline engine that was pull-rope-started. When you had the two-cylinder running, you used a hand-actuated clutch to turn the big diesel engine.

On that note I was somewhat disappointed to find out that engines from Zaporozhets weren't used as starter motors (http://www.readrussia.com/blog/made-in-russia/00067/) for Soviet tanks.

Myglaren
09-09-2009, 06:22 PM
My dad was a marine engineer and mentioned on more than one occasion how the diesels were started with a (blank) shotgun cartridge.


Come to think of it, I believe I saw this being done on Das Boot.

Snnipe 70E
09-09-2009, 09:14 PM
My dad was a marine engineer and mentioned on more than one occasion how the diesels were started with a (blank) shotgun cartridge.


Come to think of it, I believe I saw this being done on Das Boot.

That woudl be a small marine engine probably under 2000 HP

Snnipe 70E
09-09-2009, 09:24 PM
How much of a market remains for those gigantic engines?

I don't know about container freight ships, but cruise ships have been diesel-electric for some time now, and the newer ones have an array of small engines so they can only run as much engine as they need to support the current (hah, bad pun...) demands of both the "hotel" load (basically, all of the human comforts above the water line) and propulsion.

The ship I was on earlier this year had something like two 8-cylinder engines and three 16-cylinder engines which let them trim their fuel usage anywhere along the range of full power on down to just enough to keep the lights and climate control running while docked.

Freighters and tankers are going to be single shaft with direct drive most of the time. And cost is the factor.

On modern cruise ships twin screw. And electric drive with isopod motors. That is a motor hung under the ship some what like an outboard drive on a boat. Manuaverability is the reason.

The engines and engine room on some of those ships are strange. The main engines turn generators that feed a main power supply buss. The main engines feed the buss and the main motors and hotel load are both connected to the main buss.

Some ships are diesel electric only, some are diesel electric with waste heat boiller and a steam turbine, and some ships are gas turbine with a waste heat boiler and steam turbine.

The motors on the new cruise ships are variable speed motors, that is why two motors can run off a main buss with the hotel load. And the motors on these ships are in the range of 43,000 shp or more.

Machine Elf
09-09-2009, 11:07 PM
On modern cruise ships twin screw. And electric drive with isopod motors. That is a motor hung under the ship some what like an outboard drive on a boat. Manuaverability is the reason.

An isopod (http://en.wikipedia.org/wiki/Isopod) is a small, annoying insect with armor plating.

Perhaps you meant Azipod, (http://en.wikipedia.org/wiki/Azipod) which I've heard of before.

Why are Azipods the weapon of choice for cruise ships, but not for freighters/tankers?

GusNSpot
09-10-2009, 12:43 AM
Why are Azipods the weapon of choice for cruise ships, but not for freighters/tankers?

$$$$$

Princhester
09-10-2009, 12:48 AM
Why are Azipods the weapon of choice for cruise ships, but not for freighters/tankers?

I'm not completely certain. However, the commercial ship market tends to be dominated by the need for reliability and efficiency, which tends to lead to designs that emphasise simplicity. Azipods have more moving parts, and are necessarily diesel electric which (as said above) is less efficent than just a simple big engine direct driving a simple big prop.

Where Azipods come into their own is when manoueverability ranks high in priorities.

Cruise vessels already run diesel electric , and they often go to relatively obscure ports which may not have much tug assistance. They also go into/out of ports more often.

Commercial vessels tend to go to established ports with tug assistance, and have longer carrying voyages between ports.

Snnipe 70E
09-10-2009, 12:52 AM
An isopod (http://en.wikipedia.org/wiki/Isopod) is a small, annoying insect with armor plating.

Perhaps you meant Azipod, (http://en.wikipedia.org/wiki/Azipod) which I've heard of before.

Why are Azipods the weapon of choice for cruise ships, but not for freighters/tankers?


A cruise ship needs mobilty. with AZIPODS and bow thrusters a cruise ship can do turn end for end. a freighter or tanker does not need to make those kinds of turns.

Princhester
09-10-2009, 07:13 AM
A cruise ship needs mobilty. with AZIPODS and bow thrusters a cruise ship can do turn end for end. a freighter or tanker does not need to make those kinds of turns.

Yes they do. Swinging such vessels is commonplace. In the vast majority of ports of which I have experience, you can't go out the same way you came in. Because it is easier to swing a vessel in ballast (rather than loaded) ships come into the loadport, swing head down and berth, then load and depart, and do the opposite at the disport.

Cicero
09-10-2009, 07:41 AM
So how do they start a nuclear powered aircraft carrier?

Princhester
09-10-2009, 07:51 AM
Very very carefully

Cicero
09-10-2009, 08:01 AM
I was fission for an answer.

Rocketeer
09-10-2009, 11:18 AM
...moan...

Pushkin
09-10-2009, 11:56 AM
So how do they start a nuclear powered aircraft carrier?

I'm curious, is there a big starter button in engineering/the bridge on any ship? Something that would make a land lubber like me think "Ah, so simple".

Whack-a-Mole
09-10-2009, 01:07 PM
So how do they start a nuclear powered aircraft carrier?

I'm curious, is there a big starter button in engineering/the bridge on any ship? Something that would make a land lubber like me think "Ah, so simple".

Well, there is the initial start of the reactor but once running I think it is always running to some extent till it needs to be refueled.

I certainly do not know the ins-and-outs of reactor startup but I imagine it involves putting the fuel in and moving the control rods which slow the reaction enough to allow fission to start. Pretty sure fission will start naturally in the reactor with the fuel in proximity to each other like that. No doubt a lot of things need to be happening parallel with this (coolant pumps running and so on). Doubtless there is more than a button push but perhaps it is that simple with a computer running things (and humans closely monitoring to make sure all goes as planned).

After that the nuclear reactor is really just a fancy way to boil water to make steam to turn turbines. Want the ship to go I guess you increase the reaction in the reactor and start boiling more and more water. Build up pressure, get the turbines spinning and away you go.

Princhester
09-10-2009, 11:53 PM
I'm curious, is there a big starter button in engineering/the bridge on any ship? Something that would make a land lubber like me think "Ah, so simple".

There is a lot of variety but generally speaking no. The big diesels used on commercial vessels are started by the engineers from the engine room, and there are a series of steps to go through involving turning on various pumps, closing this, opening that, before you can start it.

Snnipe 70E
09-11-2009, 12:10 AM
The captian tells the Chief Engineer when he wants to leave port. If the Chief agrees he will inform the engineering watch officer when to be ready to answer bells. The closest thingf to a start button is the EOT (engine order telegraph). The bridge will ring up stand-by engines as they single up lines.

Oslo Ostragoth
09-13-2009, 12:59 AM
Small gasoline engines were used to crank over hard starting large diesel engines, back when the electric starters weren't up to snuff.

They're usually called pony starts, donkey engines, or cranking engines and were used on John Deere diesel tractors from 1949-1960. Tiny opposed two cylinder engines or tiny V4s, depending on the tractor.

And on Caterpillars too, as was mentioned

Here is a video of a pony start Deere, being started:
http://s108.photobucket.com/albums/n8/weirddeere/?action=view&current=70DStart.flv

A Johnny Popper? (Two cylinders opposed?)

Oslo Ostragoth
09-13-2009, 01:11 AM
Excellent links in this thread.

Why, yes, in fact I am a Big Machinery geek.