S-18 prop shaft issue

[Geo_08]

Why is it that sometimes one of the prop shafts just stops limiting my speed? Am I doing something wrong? If so please can you tell me how to avoid this?

[Daniel Prates]

Could it be that batteries are being reloaded? When the diesel engines are set to reload the batteries, some of the power generated does not go into propulson, but instead it runs a dynamo that recharges the batteries. Now, I do not know it that implied only one shaft remaining spinning. Check to see if that happens only when you have surfaced and batteries are reloading. Try also un-checking the "reload batteries" option.

[Geo_08]

it makes sense as there are only two engines on that sub

[Stealhead]

You are correct in the S-boats there are only two engines so if you are charging the batteries one of them will be off line and therefore one of the boats screws will not be moving reducing your speed.Of course this happens in all boats while charging the batteries it is just more obvious in the S-boat because it loses a screw and is notably slower while the other boats both screws are still on line the boat will be a couple knots slower than it normally would be at a given telegraph setting.

[CCIP]

Actually it's not the number of engines - none of the diesels in the more modern Fleet Boats drive the shafts at all, but rather just generate power for the electric motors. The S-boats, however, do indeed have the more traditional direct drive.

Don't know about the S-Class subs, but the German two-engine boats had a gear that allowed one diesel to run both shafts. I believe the lack of spinning of one prop (though not the loss of speed) for recharging on those is also inaccurate... But as for the S-boats, I'm not sure! But that is why it stops in the game like that.

[Daniel Prates]

none of the diesels in the more modern Fleet Boats drive the shafts at all, but rather just generate power for the electric motors.

Wait wait wait, just to be clear about this: fleetboats were like destroyers, where the burning of fuel (in DDs case, in boilers as to generate steam, whereas in subs there were piston engines) was intended to provide electrical power at all times - meaning that the prop would always be driven by electric engines ? I was under the impression that fleetboats, as U-boats, directly transmited mechanical power generated by the piston engines to the shaft, and that propulsion was geared to the electric engines only when submerged. Isn't that so?

[Sailor Steve]

Wait wait wait, just to be clear about this: fleetboats were like destroyers, where the burning of fuel (in DDs case, in boilers as to generate steam, whereas in subs there were piston engines) was intended to provide electrical power at all times - meaning that the prop would always be driven by electric engines ? I was under the impression that fleetboats, as U-boats, directly transmited mechanical power generated by the piston engines to the shaft, and that propulsion was geared to the electric engines only when submerged. Isn't that so?
Nope. Fleet boats were diesel-electric. Just as with modern locomotives, the diesels provide power to the generators.
http://www.maritime.org/fleetsub/diesel/chap1.htm#1D
http://www.maritime.org/fleetsub/elect/chap2.htm#2A

[Stealhead]

The mighty diesel-electric I bet many people dont know that most of our trains in US run on them much less our fleetboats. Nice post Steve.

Another great source for info about diesel-electrics and how they developed in the US Navy is: The Fleet Submarine in the U.S. Navy A design and construction history. http://www.amazon.com/Fleet-Submarine-United-States-Navy/dp/0870211870

I don't think you can find any on the book on the web for free but it has been out of print for years so a good copy is gonna be pricey.But it is very interesting I read through it all the time.Some how the copy I received from Amazon or whoever the sub contractor was they listed mine as used good condition and somehow they also missed that it is signed by the author!

[Daniel Prates]

We learn something new everyday. I could swear that when surfaced, all 1940s subs would be gearing the shaft direcly into the diesel engine.

I knew of this diesel-electric arrangement concerning trains, and once I actually had the chance of speaking to a machinist. I asked him why this arrangement is used in trains. He gave me several reasons:

1 - In a machine as large as a train, mechanic transmission, gearing, cranks and etc would only add up to mantainance, size, wear and etc. Having the final engine axis to propel nothing but a dynamo reduces the entire compexity of the whole engine;

2 - Torque control and precision is much easier when the final power is delivered by an electric engine. It is hard for a big-sized diesel engine to deliver fine control inyo the whell - say, for instance, in departure, when you want the wheels to start rotating slowly and stedly to avoid loss of atriction;

3 - Electric transmission allows easy foward/reverse shift.

4 - There is no need for transmission shifting, cranking or anything of a sort.

Come to think of it, all of those apply to warships.

[TorpX]

I'm not an expert, but I believe there are a few additional reasons:

1. Fewer problems in case of engine casualties.

2. Greater flexability in recharging batteries.

[Stealhead]

Actually one downside to a more complex set up would be that it is going to be more work to get it fixed which is why some like the H.O.Rs and early GM units had a lot of trouble early war but this was due to the complexity of making the engines lighter for submarine use. also the set up is similar in subs but not exactly the same as in locos.

I guess in a direct drive set up it could mean trouble as well.But with multiple engines you can deal with it better still it is an instant RTB in either case.
You would have better battery recharge abilities for sure.

Ah found a good link with some diagrams of the set up you'd have to look up a given class to see its exact set up there was some variation on the set up before the Seadragon class(not in game as a separate class) set the diesel-electric with reduction gear setup which was refined with each class so variation afterwords as well.I dont know how accurately the composite drives are in game which would be the Porpoise,Salmon,and Sargo class which in the game includes the Seadrgon class even though they had different drive systems in real life and where treated as separate classes.

http://www.fleetsubmarine.com/propulsion.html

This is good just for basic reference though as it says that Gato was the first class to have 4 diesels which is incorrect.

[Dogfish40]

Actually one downside to a more complex set up would be that it is going to be more work to get it fixed which is why some like the H.O.Rs and early GM units had a lot of trouble early war but this was due to the complexity of making the engines lighter for submarine use. also the set up is similar in subs but not exactly the same as in locos.

I guess in a direct drive set up it could mean trouble as well.But with multiple engines you can deal with it better still it is an instant RTB in either case.
You would have better battery recharge abilities for sure.

Ah found a good link with some diagrams of the set up you'd have to look up a given class to see its exact set up there was some variation on the set up before the Seadragon class(not in game as a separate class) set the diesel-electric with reduction gear setup which was refined with each class so variation afterwords as well.I dont know how accurately the composite drives are in game which would be the Porpoise,Salmon,and Sargo class which in the game includes the Seadrgon class even though they had different drive systems in real life and where treated as separate classes.

http://www.fleetsubmarine.com/propulsion.html

This is good just for basic reference though as it says that Gato was the first class to have 4 diesels which is incorrect.

Absolutly, on the nailhead! Which is why some of the Salmon fleetboats with GM motors needed complete overhauls after just two patrols at the wars start. The engine/powerhouse design is actually quite ingenious. As someone here mentioned, the engines were able to start and stop with great precision and without a great deal of jerking about and noise ect....but,... reducing the size of these great engines along with a few other things meant a lot of overheating, parts wearing out quickly and seizing up, the crews were constantly fixing the engines while on patrol.
A great mod for the game would be periodic/random mechanical failures just enough to annoy the heck out of you but stuff that could be repaired at sea. I don't know if that would be too weird but it would certainly be true.
D40:salute:

[Daniel Prates]

reducing the size of these great engines along with a few other things meant a lot of overheating,

Internal heating was a serious problem, as constant sweating, engine heat, and CO2 emissions would turn the boat to be constantly dripping due to damp, and thus damaging electric instruments and making the boat generaly unhealthy and unconfortable.

It turns out that the problem was properly solved with the adition of a complete air-conditioning system, which not only was 100% efficient, but also made fleetboats to be very cool and breezy. For what we hear, other countries's counterparts did not share the same confort.

[Stealhead]

The later 1943 and after GM units where actually quite good in fact according to the submarine design book I mentioned(by the way the author was a 30s 40s submariner himself) they where equally as reliable as the Fairbanks units in fact I believe that the GMs where a little easier to work on than the Fairbanks where.Interestingly GM had and still has much success with their diesel locos Fairbanks Morse on the other did not and eventually went under some time in the 60s the main reason being the much more complex design of the Banks more costy maintenance than GMs.

Actually the A/C system would have little to no effect on the diesels internal workings that is why early Tambour,Gar,and Gato fleetboats still had troubles even though they had full A/C systems.It was the way that the engine blocks where designed to be thinner to save weight that was part of the issue parts where breaking because they could not handle the strain and had to be redesigned others also had poor internal engine cooling the cure was to design stronger parts and ensure that the engines internal cooling system as more effective.

The primary benefit of the A/C systems was a reduction in moisture thanks to the evaporators absorbing it this helped reduce with corrosion and making the air less humid.Dont think of your homes A/C it would not have made the boat anywhere near that cozy with the A/C on it would still have been 85 degrees or so at best in stead of over 100 it pulled the air down enough to be less unbearable it still would have been stale air and you'd rather be top side in the open air any day.Systems back in those days where vastly different from a modern A/C but they where better than nothing but it was not like staying at a Hyatt with the number of crewmen on a submarine and all the heat being given off by machinery and the like the evaps would have been loaded to the max these where industrial machines designed to make working conditions more efficient and lower high humidity levels not to make a person cozy.

I work as a commercial refrigeration tech so I know some about commercial A/C systems which is what the fleetboats had with the technology in those days there is no way as far as I can tell that those systems would have been able to handle the heat load generated inside for very long(not to make the boat feel like say you house with the A/C set to 75 anyway) though they would have been able to pull down the humidity level enough to prevent the inside hull form sweating based on what I have read in various technical books on subs and books by submariners it seems that they normally only ran the A/C evaporators when they needed to pull down the humidity level such as upon surfacing after being submerged things like this and they also opened every hatch to the topside when they did this which suggests that they did this to aid the A/C system and to get some fresh air inside the boat.So far as I can tell they only ran the A/C system on an as needed basis not 24/7 which would have been the case for the storage coolers which would have had separate evaporators and compressors from the A/C.There does not seem to be alot about the HVAC/R systems inside an old WWII sub so you'd have to look at the old technical manuals or ask an old machinists mate that worked on them to know for sure but that's my educated guess.

Found this will digest it now:http://www.hnsa.org/doc/fleetsub/refrig/index.htm

[Dogfish40]

The later 1943 and after GM units where actually quite good in fact according to the submarine design book I mentioned(by the way the author was a 30s 40s submariner himself) they where equally as reliable as the Fairbanks units in fact I believe that the GMs where a little easier to work on than the Fairbanks where.Interestingly GM had and still has much success with their diesel locos Fairbanks Morse on the other did not and eventually went under some time in the 60s the main reason being the much more complex design of the Banks more costy maintenance than GMs.

Roger that,
I was specific to mention the motors at the start of the war because that was when they were at a time when the fleetboats were really being tested at war. Because we had the biggest and best manufacturing, these problems were generally short lived. A lot of fleetboats were going back to the east coast mid-war for complete overhauls, they got new motors, conning tower cutdowns, everything they could put in, but our motor design was always (I believe) the best.
By not having any direct diesel power it cut a host of potential problems. I'm still studying this subject from the patrol reports so I'll end my comment here, but your totally correct in that the GM motors functionality was fine by the mid war and the design was always brilliant, or at least better than any of the other subs that I've read about.
D40:salute:

[Stealhead]

According to that old TM it seems that they could run the A/C while submerged unless under attack of course Im sure they'd run it only some of the time any time they are trying to conserve batteries.Also it they can have only turned on the fans and not the compressors for ventilation.

Form what I can see I doubt that the air temp would have been what we would consider cozy but it would have been bearable at least and you are getting some air movement as well so from a working comfort point of view it seems that it would have done its job If you where in a sub around Japan or that part of the Pacific it would have been better down south I doubt it would have been as comfortable but again better than nothing.

It states as well that the goal was for operational comfort and to remove humidity and cycle the air which makes it better than truly stale air.

Also here is the propulsion TM:http://www.hnsa.org/doc/fleetsub/diesel/index.htm