Looking for Procedure used to Reverse Titanic's Engines

[Robert Peloski]

Hello

I apologize if this has been covered, I've done my best to familiarize myself with some of the various posts and articles on the site but don't recall seeing this exact information posted.

Reading on Titanic's engines (and reciprocating engines in general) I've learned that the direction is controlled by the stephenson linkage. As per the diagram in the article https://www.encyclopedia-titanica.org/titanic_prime_mover.html it shows a reversing linkage to shift the system over from forward to reverse. I'm also under the impression that this linkage is controlled via a switch that actuates a steam cylinder (which also redirects the flow of the engine exhaust to bypass the turbine engine).

So initially, my thoughts are that they would close or reduce the throttle to slow the engines, flip the switch which would shift the linkage over than open the throttle back up.

However, I recall reading that it was not necessary to reduce the throttle. How then can they shift an engine from forward to reverse without putting massive stress on the cranks and shafts from an abrupt shift? Is there actually some mechanism that lets them gradually shift the engine into reverse as opposed to the sudden jolt that is often discussed?

Thanks in advance!
Rob

 

[Brent Holt]

The sudden jolt may never have happened. It is likely that the engines were not reversed during the maneuvers to attempt to dodge the iceberg. Some sources say it could take 2 minutes to reverse the engines especially since there was no one in the engine room expecting a full astern order. (Which may not have been given)

 

[Robert Peloski]

No need to convince me on that.

I'm more interested in the general operation of reciprocating engines than of the events up to the collision.

 

[Samuel Halpern]

Robert.

With engineers at the ready, it would take from 10 to 20 seconds to get the engines to start backing and about 50 to 60 seconds for them to start backing hard.

 

[Robert Peloski]

Sweet, I have the author of the article in the thread.

Perhaps I should rephrase my question, what stops the engines/shafts from "blowing up" when they shift the linkage that fast without first reducing the power via the throttle?

Surely the stress of shifting a huge engine like that from 75rpm forward to...well anything in reverse has to put a huge amount of stress on the parts.

Does the reversing rod gradually shift the linkage from forward to reverse over a period of 20 seconds as opposed to instantly shunting it over?

 

[Samuel Halpern]

Hi Robert.

The reversal of the engines would have to done smartly. I'm pretty sure they didn't have to close the throttle valve, but I don't believe they would simply throw the reversing lever from ahead into full reverse instantaneously. Perhaps Steffen Reichel, if he sees this, can explain it since he has had experience with large reciprocating steam engines.

 

[Robert Peloski]

Thanks for the quick reply. I will wait for further responses from some of the others.

As a side note, I think it's just amazing that they were able to engineer technology of this scale and precision back then.

 

[Joe Burgard]

Hello Rob,

I don't have any hands on experience with really large marine reciprocating steam engines, but I do have experience with steam engines in general (like steam tractors and so forth). So maybe I can answer some of your curiosity. I saw your post earlier and was trying to find some old manuals online to see if they offer the reversing procedure you're looking for. I'm still working on a thermodynamic analysis of Titanic's engines as well, so I'd like to think I know something about steam engines ;-)

"Operation and Maintenance of Main Propelling Machinery" Section III: Reciprocating Steam Engines from the US Navy probably has what we are looking for but I haven't been able to track down a copy. On Google books you can download "Handbook for the Care and Operation of Naval Machinery" by Henry Charles Dinger from 1908, which has some good info that I conferred with.

To clarify do you mean reversing the engine while maneuvering (ie at slow speeds) or an emergency reversal from full ahead to full astern? The two situations would be quite different, since as you mentioned from full ahead to full astern puts considerable stress on the engine parts with the danger of breakage. A friend of mine who was part of the engine crew on an US aircraft carrier said that when they did a full ahead to full astern exercise the whole ship was shaking due to the propeller turbulence.

Now to the procedure of reversing. In terms of the throttle Dinger says:
"The throttle must not be suddenly opened or closed, but the engine, especially if a large one, should be allowed to work up to full power gradually."
With regards to reversing:
"When reversing, the throttle should first be closed, and engine then reversed; but when the emergency signal is received (that is, a signal to back full speed when going ahead), the engine should be immediately reversed, even at a risk of breaking something. This signal should never be given from deck unless it is an emergency signal."

1. Upon receiving the signal to reverse the engines, the throttle would be almost closed or closed completely to let the engines slow down. (In Titanic the by valve to bypass the turbine would be thrown as well.)

2. The engineers would have to watch to make sure that the HP cylinder was not stopped while it was at top or bottom dead center, but stopped near the middle of the stroke. This is so that when the reverse linkage is thrown over, the engine will self-start. If the HP cylinder is at top or bottom dead center, then pass-over valves would be used to inject steam into the other cylinders to get the engine moving. (See page 6 of Dinger's book.)

3. The reversing engine (Brown's engine) would now be used to move the linkage over from the ahead eccentric to astern eccentric (in the Stephenson linkage).

4. The throttle is now opened up slowly, and the engines will now be in reverse.

Some thoughts I have. I assume that at full speed the moving water would still want to keep the propellers rotating, so the engines would not completely be able to stop rotating? Could someone clarify this. The time it takes to do the procedure I'll defer to Sam's artilce.

If you watch the Titanic movie, the scene where they reverse the engine gives you a pretty good impression of the procedure involved (The movie used a working Liberty ship triple expansion engine to film). As mentioned before the engineer orders the reversing engine engaged at a specific point, so that the engine will self-start upon reversal. Also notice the sudden jerk (which to me shows that the throttle was not completely closed), then he opens the throttle up again.

Hope that helps and any clarifications or additional info from others is welcomed.

Joe

 

[Samuel Halpern]

Joe, thanks for posting that procedure. The Dinger info is very interesting. I believe the question at hand is an emergency reversal from full ahead to full astern. The numbers I gave in my post above came from US Navy Engineer in Chief, H. Cone, and was from backing data for USS Delaware, a reciprocating engine battleship making about 21 knots when the signal to back was received. See HERE.

 

[Brent Holt]

You can find the book Joe mentions here as a free download:
http://tinyurl.com/d5wxf3

 

[Robert Peloski]

Do you have the exact link to download that book? I can't seem to find it on that link.

 

[Brent Holt]

I double checked the link and it takes me to the correct page.
Just go to the right of the screen and click download by the arrow. You can then download it as a pdf.

 

[Robert Peloski]

I have tried Firefox and IE and all I get are links to purchase the book or look for a library.

Would it be ok if I take this to a PM with you as not to clutter the thread? I'd really like to give this one a read.

Thanks!

 

[Kelly Anderson]

There are two types of reversing engines predominantly used on marine engines. The direct type has a single long stroke cylinder attached to a crank arm on the reversing shaft via a connecting rod. One end of this cylinder’s stroke puts the Stephenson gear of the main engine into forward motion, the other end of this cylinder’s stroke puts the main engine into reverse. The speed at which the reversing engine’s piston could move was usually restricted by adding a hydraulic cylinder similar to a shock absorber to the reversing engine to resist sudden moves by the reversing engine. Without doing research, I believe that this is the system used by Titanic. There is also a worm gear type where a small donkey engine with a worm on its crankshaft engages a worm gear equipped with a crankpin, attached to the connecting rod to the reversing shaft. In this type the donkey engine is run to turn the worm gear one half a revolution, to shift the main engine from forward to reverse. The Liberty Ship John W. Brown uses this system. Both would take perhaps three to five seconds to shift the Stephenson links.

In the Titanic movie, as I recall, the Stephenson links slam over to astern motion very quickly (less than one second?), surprising the oiler standing on the grating nearby. That struck me as odd at the time, in that the potential for damage of the valve gear itself would be likely in normal maneuvering if that parts moved that fast.

With regard to having the throttle open or closed, if reversing is attempted with the throttle open, the added resistance caused by the steam pressure on the valves can be enough to overwhelm the reversing engine, causing it to stall at some point between full forward and full reverse, leaving the main engines stopped until that pressure is reduced. Even though they are known as “balanced” and are theoretically unaffected by steam pressure, I can assure you that piston valves do have more resistance when under pressure, the same as slide valves, though to a lesser extant.

With regard to the main engine’s power train, from the pistons to the propeller blades, in a well designed plant, there really is little added strain in performing a full power reversal. The steam in the cylinders is elastic, and has give. The cylinders are equipped with pressure relief valves that prevent dangerous over pressure from developing. All of the power train parts are designed to safely carry the loads that those maximum cylinder pressures impose. The propeller itself is incapable of transmitting damaging torque back to the engine it that once a certain PSI of blade loading is exceeded it will simply slip in the water. If the propeller begins to actively cavitate, then potentially damaging vibration will develop, the engines will race, and the wise engineer will reduce throttle until the cavitation stops.

If the throttle is closed with the ship traveling at high speed, the propeller will “windmill” in the water and keep the engine turning over forward until the throttle is reopened to “back her down”. In my opinion, this was shown accurately in the movie. The one detail I loved in that sequence was at the point that the throttle was reopened and the engine came to a stop, all was quiet except for a slight creaking noise as the engine loaded up with torque in the opposite direction. That was a wonderful detail. My thanks to the sound department.

 

[Samuel Halpern]

Thanks for the very informative post Kelly.