jrll@Portia.stanford.edu (john ralls) (05/08/89)
From: john ralls <jrll@Portia.stanford.edu> Jeff Medcalf <jkmedcal%uokmax@uokmax.uucp> 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
royf@roxanne.StPaul.GOV (Roy Forsstrom) (05/10/89)
From: royf@roxanne.StPaul.GOV (Roy Forsstrom) In article <6348@cbnews.ATT.COM> jrll@Portia.stanford.edu (john ralls) writes: > > >From: john ralls <jrll@Portia.stanford.edu> 1 >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 Each shaft/propellor combination is rated at a certain horsepower. Two shafts with two engines can give you more power with less draft than with one large prop. Nuclear-powered ships, at 10,000 tons, draw over 30 feet as it is. =============================================================================== Roy Forsstrom uucp: pwcs!royf Public Works Computer Services internet: royf@pwcs.StPaul.GOV 25 W. 4th Street rboc: 612-298-5569 St. Paul, MN 56102 ===============================================================================
greg%ncelvax.UUCP@nosc.mil (Greg Ramsey) (05/16/89)
From: greg%ncelvax.UUCP@nosc.mil (Greg Ramsey) In article <6348@cbnews.ATT.COM>, jrll@Portia.stanford.edu (john ralls) writes: > I doubt any surface ships have been built with multiple shafts on a > single engine or gear set. I can think of at least one class of US Navy ships that had one engine driving both ships, at least part of the time. PG's (Asheville class I think) had two diesels driving two shafts for slow speed crusing, and one Gas turbine which drove both shafts through a huge gearbox. The propellers were controllable pitch though, so it could still vary (or reverse) the thrust of the screws independently. Greg -- ___ Greg Ramsey _n_n_n____i_i ________ Naval Civil Engineering Lab (____________I I______I Code L54 805/ /ooOOOO OOOOoo oo oooo Port Hueneme, CA 93043 982-4619