Time for reversing

Doug Criner

Member
There have been earlier posts about the time required to reverse a reciprocating marine steam engine. It seems like a couple of minutes, depending upon various factors, but several more minutes to bring the ship to a dead stop.

What do we know about the time between when the bridge watch realized that Titanic was on a collision course with the iceberg and when the collision occurred? If that time interval is longer than necessary to reverse the engines, then it seems like this issue is moot?
 
What do we know about the time between when the bridge watch realized that Titanic was on a collision course with the iceberg and when the collision occurred? If that time interval is longer than necessary to reverse the engines, then it seems like this issue is moot?
Mistake - I should have said "shorter than necessary." Sorry.
 
As someone once said, engine orders had to be sent to the engine room by way of the engine room telegraph and then whoever was on watch had to work all of the controls to stop the flow of steam to the engines by closing the stop valve, engage the reversing gears, then start the flow of steam to the engines all over again by opening the stop valves. If you didn't have everyone on station at standby ready to act in an instant (and out in the middle of the Atlantic there was no reason to) this all is going to take some time. From reports of several people, the engines on Titanic did not come to a stop until about 2 minutes after the impact with the berg.
 
Sam is dead right about how long it would have taken in mid-ocean to accomplish reversing a steam engine. This fact should not be confused with the necessity of trying, however. It was Murdoch's sworn duty to do everything in his power to conduct a safe voyage. It might have been that a man just happened to be on the operating platform in the engine room and just might have accomplished the task soon enough to have made a difference. Not that this was the case, just that it might have been. So, because it was possible to issue an engine order even though the likelihood of it being accomplished was slim to nil Murdoch did the prudent thing.

There is something else to consider. It is not necessary to actually reverse an engine to aid in maneuvering a twin-screw vessel. The bow always falls toward the side of the weak screw. This is true even if you just reduce the R's on one slightly. Murdoch may have been hoping that reaction by the engineers would have been quick enough just to aid in his attempt to mitigate damage during contact on the iceberg. If so, he may have been somewhat successful even if the actual stopping of the engines did not happen for the two minutes or so mentioned by Sam.

The last possibility was just an attempt to warn the engine room something bad was coming their way. Snipes have no port holes. They can't see what's coming. But an emergency engine order in mid-ocean would surely indicate something important was happening topsides and it probably wasn't going to be good.

-- David G. Brown


PS -- although not in Titanic's time, during both World Wars deck officers often arranged a telegraph code for the impending arrival of an enemy torpedo. It was usually something nonsensical like "Finished With Engines." When that rang down everybody below knew it was time to leave.
 
But what about the time to just stop the engines? Murdoch's initial engine order was not "astern", it was "stop". The "astern" order came about 30 seconds later, after the ship came off the iceberg.
3720. Was anything done to the engines? Did they stop or did they go on? A: - They stopped.

3722. Did they continue stopped or did they go on again after that? A: - They went slow astern.''


3723. How long were they stopped for before they began to go slow astern? A. - About half a minute.

-- Paddy Dillon, trimmer
 
The reciprocating engines of Titanic were direct coupled to their propeller shafts. There was no clutch or reversing gear. So, to revers an engine it was first necessary to stop it from rotating in forward and then upset the valve train so that the whole drive system -- engine and propeller -- would rotate in the opposite directions. Slowing, stopping, and reversing all required appropriate application of steam power.

-- David G. Brown
 
>> But what about the time to just stop the engines?<<

If everyone was at the standby and read y to act when an order to stop comes down, then an engineer would close the stop valve, which was a large wheel that was turned by using both hands to cut off the steam from an engine, and then wait for the engine to come to a stop. All of that would take about 30-45 seconds, or thereabouts, depending how quickly the stop valve can be closed. If I recall correctly from how things were done in Olympic, at full ahead, the stop valve is opened 8 to 10 turns. Again, all of that assumes everyone was at the ready to begin with. Dillon thought the engines came to a stop about a minute and a half after the impact which was more or less about what other people recalled.
 
Even today with a marine diesel engine, it takes some time to stop the propeller(s) turning. I would imagine that the engineers on Titanic would have used a similar method to a diesel engine. I have had a few emergency rings astern in my time at sea, and it means bringing the fuel lever back to stop, which will shut the fuel off the engine. However, at 15knots and well below the speed of the Titanic at the time, the windage from the propellers means that you have to apply astern air to the engine in order to overcome this windage. A lot of air can be used in this manoeuvre (slower than a steam engine as you have to open all the valves on the air system first) and even so, when turning the engine astern and putting the fuel on, the engine could still come back from astern to ahead but with the gear in the astern position. In this case the "Wrong Way" alarm rings and you know the engine is running ahead in the astern position. Translating this to a steam reciprocating engine, and bearing in mind that Titanic's engineers had first to move the changeover valve for the lp turbine to direct the main engine exhausts direct to the condenser, astern steam would have to be applied in order to bring the engines to a stop, then keep applying the steam until the engines went astern. I would think that they would have to keep applying astern steam for some time (as with the air on a diesel engine) to bring her to a stop at the speed she was running. Around 2 minutes seems about right - that's a long time when you are heading for imminent disaster!
 
Thanks for the interesting comparison to marine diesels. I cut my teeth on steam-turbine propulsion. My first ship, was an ancient twin-screw destroyer. Of course, turbines, like Titanic's, can't be reversed. But, our main turbines had a separate astern section built into the low-pressure casing. When cruising ahead, if an unexpected astern bell was rung down, it was treated as an emergency, The procedure in each of the engine rooms was to shut off the main ahead steam, crack open the throttle to the astern section to help stop way, and then give full astern throttle.

In the boiler rooms (a.k.a. fire rooms), the simultaneous procedure was to cut in all the oil burners - because the astern turbines were very inefficient, they needed maximum steam flow.

I don't know for sure, but I think it maybe took 2-3 minutes to start driving the props hard astern, including the time for the snipes to come to attention and get on the ball.
 
Hello codad1946. My early experience was with triple expansion steam then more and more with motor ships and even an EGTV (exhaust Gas Turbine Vessel). and an old T2 Tanker. My memory is getting a wee bit disobedient but I seem to remember Chiefs going 'ape' when we rang down Full Ahead to Full Astern without a pause. Perhaps it was just a few crankie (no pun intended) old Chiefs? Did you ever experience that oil and water argument?
 
Any Skipper who goes from full ahead to full astern on a warship ends up buying a crate of ale for the on watch stokers. Full ahead is only ever given in an emergency. All orders on RN warships are given as half ahead and then in engine revaluations only. If a skipper is in trouble he will order full ahead which is the signal to the ships control centre to start shedding power to shove every ounce into the engines (they are diesel electric drive). If the skipper has really lost it and after all of that has to throw the throttles full astern, it's beers in time. I've only seen it happen once and the skipper really did loose it. He's an Admiral now.
 
David Brown,
I am not convinced what Murdoch would have understood as the best thing to do. Presumably knowing there was a berg rather close, that it took a considerable time to stop the ship, probably he could have seen it would be far too long, having chosen to try to turn her away, I dont see why he would have cut propulsion which would have reduced his limited ability to turn away. Yes, ordering stop on the relevant outer propellor to help with a turn, but ordering stop on the other propellor would presumably make matter worse. So I half agree, half disagree, that he might have chosen to stop one engine, not both. The central turbine ran off exhaust steam from the piston engines, so presumably would have lost half its power if one side engine was stopped (I'm guessing more than half allowing for inefficiencies), which might also have impacted on the performance of the rudder, situated behind the flow from the centre propellor.

The other problem I see, is that Murdoch if he understood his job might already have anticipated he would need to immediately turn in the opposite direction to cancel the rotation of the ship. Maybe he was hoping that the ship would swing gracefully away from the ice in one smooth curve, but presumably familiar with difficulties coming into docks with land closeby, he must have been well aware of the necessary reaction to cancel a full turn in one direction by reversing the controls.

It sounds like the sort of question which needs to be adressed to someone experienced with handling a big ship, faced with making the best of a no win situation where he decides to try to avoid collision but knows this will be very tight if it works at all. The basic physics of getting large masses of metal to stop moving and then start again in an opposite direction hasnt changed.

I understand Murdoch was probably one of the very most experienced people in the world at that time with handling such large ships. Of course, not least because this was the biggest ship in the world. I'm not sure if that is an impressive qualification, or a big risk because no one was really experiencd with such situations. I think it must have hampered official understanding of what had happened that there would be hardly anyone impartial with real experience who could have been called upon to analyse what took place. From what I have read, I think he must have understood this was a situation where he probably could not miss the berg and could not stop, and would therefore have planned what he would do on that basis to minimise damage.

I am also not clear whether he would have known that ramming the berg was probably safer than grazing it. He might have, which might then itself imply he thought he had a chance to avoid collision completely. But even if he felt grazing was better than colliding, obviously avoiding was better than grazing, he must have been thinking about the best way to do it given the limited control he had on engines or rudder.

How good was he at his job?

By the way, its great to see posts from people who have had some actual experience with such machinery.
 
Recently Watchmojo.com posted a video about shocking "what have I done" scenes in movies. And the 1997 film scene where "William Murdoch loses it" is featured on #4.


(skip to 7 minutes 51 seconds in)

Just 2 hours ago, some commented this:
Certainly, there's nothing wrong to be said with about decision to turn the ship hard a starboard to dodge the iceberg, I'm sure any other officer would have done the same in the circumstances. Interestingly, he was the only one of the Titanic's officers (IIRC) to have passed all his navigational certificates - which were notoriously very hard - on his first attempt.

And he's to be commended for his work on the lifeboats too, especially for letting men on when there weren't any women or children around. There have been some snippets of reports from passengers years later of an unnamed officer shooting a man and then himself, but it's doubtful that they've been substantiated. Regardless, his actions on the night were doubtless heroic.
 
There have been earlier posts about the time required to reverse a reciprocating marine steam engine. It seems like a couple of minutes, depending upon various factors, but several more minutes to bring the ship to a dead stop.

What do we know about the time between when the bridge watch realized that Titanic was on a collision course with the iceberg and when the collision occurred? If that time interval is longer than necessary to reverse the engines, then it seems like this issue is moot?
have you ever worked on a ship with Reciprocating Engines, Mr. Criner? Please forgive me, I can't remember if the Olympic class were the only ones with a triple expansion engine. What were Navy ship's engines like?
 
have you ever worked on a ship with Reciprocating Engines, Mr. Criner? Please forgive me, I can't remember if the Olympic class were the only ones with a triple expansion engine. What were Navy ship's engines like?

With any conventional or nuclear steam plant, it would be much the same. The issue in this case isn't the type of engine as it is the means by which they were operated.


We seem to take it for granted that it's possible to run the engines by direct control from the bridge, but this is far from case,. Rudders...yes....engines, not so much. This is why you have an engine room telegraph: The bridge signals it's orders, but it's the snipes down in The Hole who work the controls to stop, go ahead, reverse, of run one shaft ahead with the other being run full astern and so on.

To imagine what this would be like on a car: You operate the steering wheel, but it's the person in the back seat who has his foot on the gas pedel and the brakes, and you tell him what you need him to stomp on, then hope he reacts in time to avoid hitting that telephone pole.
 
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