[BITList] Meccano?

[HUGH]

Colin,

I sailed on Chakdara, Chilka and Chinkoa, and all three had controls on the stbd side, guides on the port side. Dilwara, twin screw, had controls facing each other.  The two Clan boats I sailed on were single screw 6-cyl Doxfords, unsettlingly like the Cs down below, and both had controls on the stbd side.  Each B&W I helped to build in Kincaids, and each Sulzer or Doxford   I was involved with in Scotts, was single screw ditto.  Such engine were port engines (port in a twin screw pair) - they are set up for clockwise turning, looking for'd.  This means the main guide faces for the bottom pistons take the astern running forces, and those for the top pistons take the ahead, and vice versa, but that's the way they are set up. Note that Dilwara and Dunera (I can't speak about any other BI Ds) had outward turning propellers - inward turning was the more usual style, at least for turbines or other prime movers with gearboxes.

Where possisble, the guides were on the stbd side for clockwise ahead running, so that the ahead guide forces should be taken by the main guide faces, and the controls were mostly ditto. This wasn't possible with any opposed piston engine I've seen or read about. The following is from an email I wrote during my BIShip days, but didn't send.

Hugh.
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"Someone asked why anyone would design a ship with inward turning props.

Ship design, per se, only takes place for the first of a class, and it may well be an amalgam of ideas from owners, builders, and people who didn't get the contract.  I worked on one vessel that went the rounds for a number of years before the hull contract was awarded to Lithgows in Port Glasgow and the machinery contract to Kincaids in Greenock.  Some years before that I did some work on the project while I was with Scotts of Greenock.

It is quite possible that consideration of the handling characteristics of a vessel never gets a proper airing, unless someone with a bee in his bonnet makes an input early enough and loud enough.  At all design stages it's every man for himself - someone who stubbed a toe on a Weir's pump will try to veto Weir's pumps, etc. "The last ship we worked on" syndrome can operate a lot, as can cost.  I have worked on ships from blank sheet stage onwards, and once papers are signed things get set in concrete pretty fast, otherwise the process can go on for ever.  That said, it seems pretty certain every twin screw turbine or diesel electric vessel had/has outward turning screws via gearboxes, but that could easily be down to tradition (the way the last one was built, for convenience), as with the clockwise turning single screw.

Anomalous twin screw ships would seem to be represented by Dilwara and Dunera, both propelled by Doxfords, direct drive. The only reasons I can put forward for a shipowner (BI) having accepted the inward turning configuration in this instance (always supposing the matter was ever discussed) are (a) any problems foreseen were thought trivial, and/or (b) the cost of producing a pair of Doxfords for outward turning was thought prohibitive.  Most probably it was (b).

The least modification to a standard clockwise Doxford (installed as port engine on Dilwara) for service on the stbd side would be the transfer of the controls and gauge board to the other (inbd) side, with a suitable linkage back to the "camshaft". Unless the piston cooling return hoppers and thermometers were also moved, these would be on the wrong side of the engine for efficient monitoring when manoeuvring.  There could also be other changes. We are now lacking a port engine. This would have its guide bars on the inb'd side, hence its PC return hoppers, etc, would also be on the "wrong" side. The PC returns could in theory be rerouted to the other side, but that would cost money and might be impractical once looked at in detail."
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