Quoting Michael Askin <[EMAIL PROTECTED]>: > > With both engines still going full speed (one ahead, another astern) > there should have been enough waste steam to drive the turbine. Of > course, going forwards is what is needed to get the prop wash across > the rudder. > > It is, however, interesting to note that: > > "There was no throttle control for the turbine engine. The turbine > simply responded proportionally to the amount of exhaust steam being > received from the reciprocating engines." > Source: http://www.encyclopedia-titanica.org/titanic_prime_mover.html > > There was a regulator, but the web page intimates that this is just to > limit maximum revs, though this may have been brought down to a lower > level during the manoeuvre. So was the center prop still turning then? > Hmmmm.....
It wasn't a regulator (which is what the 'throttle' is called on a steam engine!). It was a set of bypass valves operated by a Browns engine which could be manually engaged and which was also linked to the governor on the turbine. If the turbine revs exceeded the maximum limit, the valves would be operated to divert steam away from the turbine until the revs dropped again. A key point is contained in the above web page. As I suspected, the turbine was bypassed during maneouvering and when going astern by the operation of bypass valves which directed the exhaust steam from the main engines straight to the condensers. The page also states that the turbine was only engaged at speeds above half ahead. Another source notes that the turbine could not be engaged until the exhaust steam from the LP cylinders was absolutely dry. The 'Encyclopedia Titanica' web page is quite complimentary about Titanics' engine arrangement which is more than most other sources I've read! There it is suggested that it was a more powerful and efficient arrangement than the all turbine setup already in use by Cunard. Pretty well every other source is less complimentary on the subject suggesting the White Star were forced to resort to a less efficient lash up of old and new technology due to Harland & Wolf's lack of technical expertise in turbine technology. (Cunard having had Government support both financially and technically from the Royal Navy experience with turbines). The turbine on Titanic probably shouldn't be thought of as a seperate third engine as it operated effectively as a fourth stage extra low pressure 'cylinder'. Titanic's engine arrangement was in effect a quadruple expansion engine. The only effective control over the turbine was 'on' or 'off' and whilst I cannot work out for certain whether engaging the reversing gear on the main engines automatically engaged the turbine bypass valves, if it didn't it would seem clear that it would have been routine practice for the turbine to be disengaged manually before reversing the main engines as the turbine was never used other than when going ahead at cruising speeds. Bru
