Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!purdue!decwrl!ucbvax!tut.cis.ohio-state.edu!att!cbnews!jrll@Portia.stanford.edu From: jrll@Portia.stanford.edu (john ralls) Newsgroups: sci.military Subject: Iowa Manueverability Message-ID: <6348@cbnews.ATT.COM> Date: 8 May 89 01:49:12 GMT Sender: military@cbnews.ATT.COM Lines: 23 Approved: military@att.att.com From: john ralls Jeff Medcalf writes: >[stuff deleted] >counterclockwise. On most 2-screw ships, this cannot be done because both >shafts are linked to the same powerplant or gearbox. This would be difficult at best, and would eliminate some of the reasons for having multiple shafts. The separation required between shafts to prevent the propellors from hitting and the large size of the bull gear (the one that the shaft is attached to) mean that it would require rather complex gearing to carry the energy from one engine (or turbine) to two shafts. The main reasons for having multiple shafts are: 1) more power - and you'd have less if you drove two shafts off one engine; 2)redundancy - shafts seldom fail, engines often do. 3)maneuverability - the ability to twist the ship, by going ahead on one side and back on the other, is extremely useful in close quarters maneuvering (eg, alongside the pier). I doubt any surface ships have been built with multiple shafts on a single engine or gear set. (I know of one submarine -- but the details are classified, so I won't discuss that here). John