The steering gears for the Titanic were built by the machine shops at Harland & Wolff and were of the Wilson-Pirrie Type and were situated on C Deck under the after end of the Poop Deck.
The steering engines were roughly about ten feet tall and about twenty feet long with a width of about ten feet.
The steering gear consists of a spring quadrant and tiller on the rudder shaft that was operated through wheel and pinion bevel gearing on two sets of three crank vertical steam engines. Only one of these steering gears would be in operation at any one time while the other served as a standby.
The engines feature three pistons a piece, with a bore of seventeen inches with an eighteen inch stroke operating under 100 psi. Piston steam valves were used on these engines which were operated from the crankshaft.
Each engine is arranged on a sliding bed with adjusting screws that allow for one engine to be quickly engaged or disengaged from the quadrant when it is desired to change operation from one engine to the other.
The crankshafts of these engines were fitted with a spur pinion which operates a spur wheel on the intermediate shaft on the back columns of each engine.
These intermediate shafts are connected with bevel gears into a quadrant with a pinion installed above the bevel gearing. The special arrangement of these gears eliminates back lash and allows for the noiseless operation of the steering gear.
That pretty well explains how the engines were built and the particulars of their operation, I have also attached a photo of the steering engine for the Olympic in the machine shop at Harland & Wolff from “The Shipbuilder.”
Yes there were two steering engines, one that would be online and in use and one off, so that the offline engine could be used in the case the other should fail, or need repairs.
To sum it up, the steering engines were steam powered and activated with a hydraulic piston which responded from the action of the main telemotor and using hydraulic fluid translated the movement of the wheel into the movement of the rudder.
Colin I have a detailed plan of the steering gear i would send it to you if you would like that. I would like to talk to you about ships so what is your yahoo name so we can talk on there. I have tons of other plans of ships and other stuff i could send you. Tom
Taking the ratios of all the gearing, I get a total leverage advantage of about 168-to-1 (4.83x2.89x12) for the steering engine working on the quadrant. To turn the rudder 40 deg to its hard over position, the steering engine only has to turn about 19 revolutions. Given the size of the steering engine with three 17 inch direct acting cylinders of 18 inch stroke, and steam at 100 psi, I would guess it could easily make 19 revs in under 7 seconds starting from zero. Anybody out there with better data?
Methinks your calculations are a bit out and I will have to go and study the steering set-up to check this. Ships I have personal experience with that have steam steering gear take many revolutions to go from midships to hard a port - it has to be this way to get fine control!
Sorry to post and run, but here is reply that I made to the Titanic newsgroup way back when that is on point, hope this helps:
>> "otn" wrote:
>>> Just out of curiosity, can anyone tell me the time required to get the
>>> rudder from hard port to hard stbd for this ship?
There are two things that affect the time: the power of the steering engine and its top speed. If we know the top speed and the gearing we can estimate the minimum time involved; that is the no-load time. We know the gearing, but the top speed of the engine is up for grabs.
"The Shipbuilder" lists the gearing for the Olympic class. There are three pairs of gears involved:
1. engine crank shaft to secondary shaft, 19 teeth to 55 teeth
2. secondary shaft to pinion input gear, 18 teeth to 87
3. pinion to quadrant, 31 teeth on half the quadrant, 14 on the pinion
2.89 revs of crankshaft for one rev of the secondary
4.83 revs of secondary for one rev of the pinion
2.21 revs of pinion to turn quadrant to the stop.
2.21*4.83*2.89 = 30.8 revs of crankshaft turns quadrant from amidships to limit
Tom's speed of 100 RPM for the steering engine crankshaft is probably too low. I have several reference for similar engines running as quickly as 400 RPM; Titanic's electric light engines ran at 325 RPM. I have timed the speed of the steam steering engine on SS Jeremiah O'Brien and it is in the neighborhood of 200 RPM.
at 100 RPM I get 18.5 sec to slew
at 200 RPM I get 9.2 sec to slew
at 400 RPM I get 4.6 sec to slew
(ignoring start up time and lots of other relevant stuff)
The start up time is probably negligible. The steering engines had three 17x18" pistons, all taking 100PSI steam and exhausting to the powerful vacuum of the main condensers. They were built for speed! The O'Brien's steering engine changes directions very quickly. There is less than a one second pause when it changes directions with no perceptible time required for it to get up to speed.
> ... I had two different outbound ships tonight, when I went
> aboard I timed each (electric steering). The older reefer, was 24 sec. The newer
> Car Carrier was 18 sec. ( watching this rudder, I considered it fast). ...
The O'Brien has a quadrant-type steam steering engine that is similar to Titanic's. It takes about 20 seconds, lock-to-lock, while sitting alongside the pier.
One thing to realize is that the time to move the rudder over when running full ahead is going to be greater than the time to return amidships. At some point the engine will begin to feel the force of the sea against the rudder and slow down. As the rudder angle increases, so does the force of the sea against the rudder, so it's the power of the engine that limits the speed. Returning amidships, the force of the sea is working with the steering engine, so it's the top speed of the engine that determines the time. My guess (and it's just that) is that it would take about 15 seconds to swing the rudder hard over; maybe as little as 5 to bring it back.
Another question is how long would it take the helmsman to turn the wheel hard over? Working from a diagram of a Brown's telemotor sending unit, I estimate that it took about 6 revolutions of the wheel to turn it hard over. Unlike some modern ships, the helmsman was working against the large return spring on the receiving telemotor, so he couldn't just give the wheel a spin.
> My problem with the "port around" scenario versus the 37 sec from time of sighting
> to time of impact (is this the correct approximation of time?) ...
That's the "accepted" time, but it's pretty suspect if you ask me. At the American Inquiry, Fleet testified that Titanic turned one to two points to port prior to striking, but that was after refusing to give any estimates as to time or distance. During some of that time he was on the phone to the bridge, so how he was able to provide ANY meaningful estimate of change in heading is beyond me. (Lee would have been in a better position to give an estimate, but I don't think they asked him.) As far as I know there was no compass in the crows nest. Hichens, the only guy who did have a compass, did not provide an estimate of the change of heading at the American Inquiry. By the time of the British Inquiry, both Hichens and Fleet were testifying that the change in heading was two points. The 37 seconds was determined by running Olympic full ahead, putting the rudder hard over and measuring the time it took for her to swing two points to port. The engines WERE NOT run astern, which is odd, since they had adopted Boxhall's version of events, which included running the engines astern. [see Wilding: http://www.titanicinquiry.org/BOTInq/BOTInq27Wilding01.html] I think we have to consider the fact that White Star had a motive to prove that the iceberg was sighted an acceptable distance ahead; Wilding's experiment with Olympic, based on the testimony of Hichens and Fleet certainly gave them that, but how reliable is Hichens' estimate?
>... I find it
> hard to believe there was time to go from a "hard left" turn, shift rudder, check
> swing and start a right turn, in the time allowed.
> Course, without the correct numbers for the rudder and time of impact, everything
> is speculation.