Mike, we burned No 2 crude oil, but I think that it was then changed to electric power for propulsion. I'm not an expert in this matter since I was a Airdale and did not fraternize with ships company. But I have seen the hoses dripping when we refueled at sea and it was a black, gookey looking stuff and it smelled bad.
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More Aircraft Carrier - Scenery Questions . .
- Thread starter expat
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Dumb question time (again): before the nuke era, were the Forrestal, Midway and Essex class carriers diesal-electric powered - which seems to be Helldiver's recollection on the Leyte? This seems close to the set up with modern diesal locomotives, i.e. diesal engine turns generator powering traction motors.
At the same time, I have also seen "steam turbine" power mentioned, which I expect is not the orginal "steam engine" propulsion used, for example, at the turn of the previous century powering the Great White Fleet ships etc, which would be analogous to the steam locomotive engine using boilers and steam pistons etc.
At the same time, I have also seen "steam turbine" power mentioned, which I expect is not the orginal "steam engine" propulsion used, for example, at the turn of the previous century powering the Great White Fleet ships etc, which would be analogous to the steam locomotive engine using boilers and steam pistons etc.
I may be way off base here but I don't think they had Deisel engines. Rather they generated steam that turned a turbine that powered the electric generators which ran the electric motors.
Like I say, I was a bit divorced from ships company. The air group is only guests of ships company and never get involved. We miss out on fun things like chipping paint and mess cooking.
Like I say, I was a bit divorced from ships company. The air group is only guests of ships company and never get involved. We miss out on fun things like chipping paint and mess cooking.
A
ARDVARK
Guest
HellDiver your posts are excellent and insightful, were you a Pilot in WW2?
michael davies
Charter Member 2012
As far as I can ascertain, all US carriers use steam turbines, these turbines are then direct connected to the prop shafts. It'd be some motor that could produce 37,000 HP, its hard to do that today with modern 3phase synronous motors but back in the 40's, it'd be a DC motor and thats one very big DC motor ! LOL, for a start it'd be too big and way to heavy, turbine is lighter and smaller by a vast margin and in a warship, size and weight are critical. Steam can produce vast amounts of power so it'd be crazy to change its format more than you had to before you had an output, ie steam/mechanical or steam/mechanincal/electric/mechanical, you just loose too much energy in each conversion.
So no, there are no steam/nuke-turbine-generator-electric motor propelled US carriers. There are ancillary turbines with generators for other ships supplies, but not propulsion. Traditionally power plants are split into main propulsion and ancillaries and that still holds true in todays modern vessels.
I will keep checking though, as I have a niggle that an electric motor was in the drive train somewhere and was maybe used for minimum steerage or maneuvering power, as y'all full well know, the Essex class could go almost as fast backwards as they could forwards, that'd be from the main turbines, but running turbines in brown water applications would be costly so its plausabe that electric was used in and near port.
Anyway, some turbine data for you.
Essex class, four turbines at 37,000 SHP each
Midway class, four turbines at 53,000 SHP each
Forrestal class, four turbines at 65,000 SHP each
Nimitz class, four turbines at 65,000 SHP each
What is a steam turbine ?, well its like a jet engine in reverse, though the blades are much shorter and a much larger piece of equipment, you'd not want one strapped to your wing LOL, typically their weight is in tons, lots of them, several hundred on large turbines in electricity generating stations.
Steam is generated by large boilers and then passed through the turbine, the output shaft is then connected to the prop shaft. Steam turbines are also the favored power plant for large merchant tanker vessels, typically VLCC and ULCC super tankers, the oil used here is cheap thick stuff so requires heating all the time to make it fluid, not only to burn in the boilers but to transfer from the vessel.
Attached a few pictures of a single reduction HP/LP turbine use in a marine application, pictures of naval installations are as you might image 'not easy to procure' so for this tutorial I'll use a merchant application, but the theory is the same and probably looks pretty much the same.The images are from the worlds largest super tanker the M/V Batillus 275,000 GRT, however the layout and set up is pretty similar for US carriers or other steam turbine powered vessels, though the Batillus is single reduction, Essex class is double reduction. On the Batillus each turbine is rated at 32,000SHP so pretty close to an Essex sized turbine.
There are two shafts connected to the main flywheel, each shaft houses two turbines, though technically the whole arrangement is called a turbine even though theres two 'actual' turbines inside. The smallest turbine is the High Pressure (HP) one, steam enters here at very high pressure, on the Essex class at 565psi and 850F, this passes through the blade sand makes them rotate, the exhaust steam still has an awful lot of energy left so it is trunked across the turbine (see the connecting tube) and into the Low Pressure (LP) turbine where more work is extracted from it, due to the LP side steam being much cooler and lower pressure, the blades are much larger to get as much energy from the steam. The large bell housing affair at the back end of the LP turbine is the exhaust, the prop shaft is connected to the large gear in the center of the box.
There does appear to be what looks like a radially fitted piston engine on the end of the LP shaft, this could be the reverse engine or some sort of pump off the LP shaft, though most pumps and ancillaries are fed from other parts of the vessel, so I suspect on first inspection that this is the reverse engine, but for a vessel this size I'd have expected something larger, the Essex class had an additional reverse turbine added to the other end of the LP shaft. I dont ahve the full spec for the Batillus so cannot be 100% sure where reverse is fed into the drive train.
Hope thats of some interest to someone LOL.
Best
Michael
Addendum, it would appear that turbo electric was used on the previous class of carriers, ie the Lexington class, this is new information to me and a class I'm not really up to speed on so will need to dig out more info, an interesting concept for such a large vessel and I suspect rather than one motor per shaft theres going to be quite a few to keep the size down. This class being derived from a battle cruiser hull and as such this form of propulsion seemed to be in vogue in the 20s as its also fitted to USS New Mexico and the Tennessee and Colorado class Battleships, now information on those I do have
.
Ok here we go, Tennessee class uses Turbo electric drive, featuring four electric motors, each motor is three phase, makes sense to keep size and weight down, but quite rare in the 20's as sycronous motors were not the norm. Supply to the motors is 6,800 volts, thats an awful lot of electricity LOL, each rated at 4,300Kw each which is equivalent to about 6,800SHP. Initial reading shows Lexington to have eight motors with a total of 212,000SHP, thats 26,000SHP per motor or 16,450kw / 16.5Mw now that is one huge motor by anyones standards LOL, and theres eight of them !.
So no, there are no steam/nuke-turbine-generator-electric motor propelled US carriers. There are ancillary turbines with generators for other ships supplies, but not propulsion. Traditionally power plants are split into main propulsion and ancillaries and that still holds true in todays modern vessels.
I will keep checking though, as I have a niggle that an electric motor was in the drive train somewhere and was maybe used for minimum steerage or maneuvering power, as y'all full well know, the Essex class could go almost as fast backwards as they could forwards, that'd be from the main turbines, but running turbines in brown water applications would be costly so its plausabe that electric was used in and near port.
Anyway, some turbine data for you.
Essex class, four turbines at 37,000 SHP each
Midway class, four turbines at 53,000 SHP each
Forrestal class, four turbines at 65,000 SHP each
Nimitz class, four turbines at 65,000 SHP each
What is a steam turbine ?, well its like a jet engine in reverse, though the blades are much shorter and a much larger piece of equipment, you'd not want one strapped to your wing LOL, typically their weight is in tons, lots of them, several hundred on large turbines in electricity generating stations.
Steam is generated by large boilers and then passed through the turbine, the output shaft is then connected to the prop shaft. Steam turbines are also the favored power plant for large merchant tanker vessels, typically VLCC and ULCC super tankers, the oil used here is cheap thick stuff so requires heating all the time to make it fluid, not only to burn in the boilers but to transfer from the vessel.
Attached a few pictures of a single reduction HP/LP turbine use in a marine application, pictures of naval installations are as you might image 'not easy to procure' so for this tutorial I'll use a merchant application, but the theory is the same and probably looks pretty much the same.The images are from the worlds largest super tanker the M/V Batillus 275,000 GRT, however the layout and set up is pretty similar for US carriers or other steam turbine powered vessels, though the Batillus is single reduction, Essex class is double reduction. On the Batillus each turbine is rated at 32,000SHP so pretty close to an Essex sized turbine.
There are two shafts connected to the main flywheel, each shaft houses two turbines, though technically the whole arrangement is called a turbine even though theres two 'actual' turbines inside. The smallest turbine is the High Pressure (HP) one, steam enters here at very high pressure, on the Essex class at 565psi and 850F, this passes through the blade sand makes them rotate, the exhaust steam still has an awful lot of energy left so it is trunked across the turbine (see the connecting tube) and into the Low Pressure (LP) turbine where more work is extracted from it, due to the LP side steam being much cooler and lower pressure, the blades are much larger to get as much energy from the steam. The large bell housing affair at the back end of the LP turbine is the exhaust, the prop shaft is connected to the large gear in the center of the box.
There does appear to be what looks like a radially fitted piston engine on the end of the LP shaft, this could be the reverse engine or some sort of pump off the LP shaft, though most pumps and ancillaries are fed from other parts of the vessel, so I suspect on first inspection that this is the reverse engine, but for a vessel this size I'd have expected something larger, the Essex class had an additional reverse turbine added to the other end of the LP shaft. I dont ahve the full spec for the Batillus so cannot be 100% sure where reverse is fed into the drive train.
Hope thats of some interest to someone LOL.
Best
Michael
Addendum, it would appear that turbo electric was used on the previous class of carriers, ie the Lexington class, this is new information to me and a class I'm not really up to speed on so will need to dig out more info, an interesting concept for such a large vessel and I suspect rather than one motor per shaft theres going to be quite a few to keep the size down. This class being derived from a battle cruiser hull and as such this form of propulsion seemed to be in vogue in the 20s as its also fitted to USS New Mexico and the Tennessee and Colorado class Battleships, now information on those I do have
.Ok here we go, Tennessee class uses Turbo electric drive, featuring four electric motors, each motor is three phase, makes sense to keep size and weight down, but quite rare in the 20's as sycronous motors were not the norm. Supply to the motors is 6,800 volts, thats an awful lot of electricity LOL, each rated at 4,300Kw each which is equivalent to about 6,800SHP. Initial reading shows Lexington to have eight motors with a total of 212,000SHP, thats 26,000SHP per motor or 16,450kw / 16.5Mw now that is one huge motor by anyones standards LOL, and theres eight of them !.
That make sense. Though this suggests that the turbines turned the propellors directly, via reduction gear.
http://en.wikipedia.org/wiki/Template:Essex_class_aircraft_carrier_propulsion
http://webcache.googleusercontent.c...am+turbine+reduction&cd=7&hl=en&ct=clnk&gl=uk
vora
Charter Member
Very interesting indeed, thank you.
I agree that the reverse drive is most probably propelled by the radial piston engine at the LP section. In pic#2 you see that both turbine shafts are connected to the gear shafts by couplings (LP is decoupled). So for reverse drive they probably decouple both shafts, let the rotation of the gears die down and use the piston engine in reverse direction.
I agree that the reverse drive is most probably propelled by the radial piston engine at the LP section. In pic#2 you see that both turbine shafts are connected to the gear shafts by couplings (LP is decoupled). So for reverse drive they probably decouple both shafts, let the rotation of the gears die down and use the piston engine in reverse direction.
michael davies
Charter Member 2012
Yup, that'd make sense, note also the two large discs on each shaft opposite the two turbines, one presumes they will be brake discs to stop the shafts turning before reverse is selected and once the main turbines are disconnected.
Best
Michael
Best
Michael
michael davies
Charter Member 2012
You'll like these then, OT but shows a 2500T crane being winched sideways off a 30,000GRT vessel across bridging flaps and onto the quay, and an overall view from further back and the other side showing the seaside legs just coming over.
Best
Michael
Best
Michael
Indeed, brake discs and brake shoes of gargantuan dimensions... I just love such pictures
vora
Charter Member
Was this monster crane installed temporarily on that vessel? What for? You know, no matter if you love planes or vehicles or something, it's the naval sector where the huge forces are handled with. A Nimitz with ca. 100,000 t displacement at a speed of 30 kn... just think of the kinetic energy of this! And the technology to control this comes directly out of an engineer's wet dream.
Guys love BIG forces, some the chaotic way (blow things up), some the more controlled way (turn a house-size wrench).
At the end of the day it comes down to this: :d
View attachment 15266
michael davies
Charter Member 2012
The vessel is a converted tanker, she has had most of the oil holds cut down to near water level, some of these vessels are semi submersible to allow floating loads to be loaded, but this one isn't. The cranes are made fully built in China, loaded onto the vessel and shipped all around the world to the terminal where they are destined, where upon they are unloaded complete and onto the quay.
Yup, have to confess to having a love or large dynamics and there forces, be it nautical or rail.
Best
Michael
Yup, have to confess to having a love or large dynamics and there forces, be it nautical or rail.
Best
Michael
You know, no matter if you love planes or vehicles or something, it's the naval sector where the huge forces are handled with. A Nimitz with ca. 100,000 t displacement at a speed of 30 kn... just think of the kinetic energy of this! And the technology to control this comes directly out of an engineer's wet dream.
Guys love BIG forces, some the chaotic way (blow things up), some the more controlled way (turn a house-size wrench).
At the end of the day it comes down to this: :d
View attachment 15266
michael davies
Charter Member 2012
HD, the Essex as does quiet a few other warships, have very long prop shafts, the engine room being almost midships, modern ships have the engine room as far back as possible and thus much shorter prop shafts.
The low RPM does of course mean that less 'technical' bearings can be used LOL, and during war time many specialized metals that normally make up bearings would be in short supply. Interesting info there, must look up Lignam Vitae LOL, being a youngster nearly everything I know is needle or roller bearing.
As an aside, large steam turbines don't actually have bearings in the normal sense, they float on a bed of oil, when cold they are highly pressurized to 'jack' them up, as they rotate the oil is dispersed evenly around the bearing and the shaft becomes naturally centered, not sure about Marine turbines but the Electricity ones we have here in many UK power stations have that bearing, due to the size of these turbines, pressures and temps they take nearly a week to get up to speed and temperature before they are put on line and loaded up, and then they run for months non stop. One of the down sides of there size is that the shafts bend when cold, thus when running up they wobble and as they are slowly heated they become centrifugally straight, very clever technology and quite frankly kind of scary, big bits of metal do very strange things when heated and cooled LOL.
I suspect marine turbines are much more robust and looking at the Batillus arrangement the gear box shafts look encased in roller bearings, but the turbine shafts have semi circular shells, probably oil pressure assisted, much as you'd expect due to the higher RPM involved.
Best
Michael
The low RPM does of course mean that less 'technical' bearings can be used LOL, and during war time many specialized metals that normally make up bearings would be in short supply. Interesting info there, must look up Lignam Vitae LOL, being a youngster nearly everything I know is needle or roller bearing
.As an aside, large steam turbines don't actually have bearings in the normal sense, they float on a bed of oil, when cold they are highly pressurized to 'jack' them up, as they rotate the oil is dispersed evenly around the bearing and the shaft becomes naturally centered, not sure about Marine turbines but the Electricity ones we have here in many UK power stations have that bearing, due to the size of these turbines, pressures and temps they take nearly a week to get up to speed and temperature before they are put on line and loaded up, and then they run for months non stop. One of the down sides of there size is that the shafts bend when cold, thus when running up they wobble and as they are slowly heated they become centrifugally straight, very clever technology and quite frankly kind of scary, big bits of metal do very strange things when heated and cooled LOL.
I suspect marine turbines are much more robust and looking at the Batillus arrangement the gear box shafts look encased in roller bearings, but the turbine shafts have semi circular shells, probably oil pressure assisted, much as you'd expect due to the higher RPM involved.
Best
Michael
The lignam vitae have a natural lubricity to them. Perhaps they vacuum impregnate them with additional oil. They were segmented, about 6 or 8 inches long and six inches deep. It's the hardest wood known and they told us that it would outlast most mechanical bearings. I don't remember how many bearing stations there were. I know the engine room as being very clean, well lighted and hotter than hell. This is in the days when air conditioning wasn't used by the services. It was a time for men to be men and woman to be double breasted.
I would like to know more about the running gear about an Essex class carrier. Got any blue hats out there? Like what did they use as a packing gland to withstand so much pressure? How do the maintain extra steam when the ship goes from being still to flank speed?
I would like to know more about the running gear about an Essex class carrier. Got any blue hats out there? Like what did they use as a packing gland to withstand so much pressure? How do the maintain extra steam when the ship goes from being still to flank speed?