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"That's always been my opinion because there are only 4 ways to increase the power of a reciprocating engine:"

Duncan
There is a fifth way, increase the revs.
 

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As Demodocus has written at least one of the immediate post war S class ships built for China Navigation was a three legged Doxford. This was the Soochow built by A & J Inglis Ltd Glasgow in 1947 using an engine recovered from a vessel sunk in the Mersey. This was the story accepted by all onboard in the late fifties, including myself. The other three ships were four cyl. Doxfords.
Sailed on the Soochow in 1965 when CNCo sold it to a Singapore company.
Had cam driven LO and FW pumps and was difficult to start but easy to run. The ship was built in 1945 and the engine was a salvage job from world war 2.
We all could the "Doxford Dance"
 

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Doxford Three Legged

Teb advised of the Carronpark and Lylepark of Denholms, in addition
managed by them were:
Arisaig
Clarkavon
Clarkeden
Craigallian
Crinan
Naess Trader
Wellpark
All operated satisfactory and gave good service over their respective
lifes.
Served on a few of them from J/E TO 2E.

Archie
 

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3 Cyl Doxford

I Sailed On The Cyprian Prince As A Junior Engineer Back In 1967 She Did Have A 3 Cylinder Doxford And Steam Auxillaries A More Reliable Engine Would Be Hard To Find
 

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A little off topic as it relates to later engines:-
I sailed as 2nd Mate and Chief Officer on 5 ships operated by Ellerman City Liners from 1981 though to 1988 that had the last Doxford 3 legged engines built. They were supplied to the City of Plymouth Class 300TEU "paragraph" ships built at A&P Addpledore in devon - a 6th Engine was also built but never fitted to a ship and the last I heard had been donated by Ellermans to the Glasgow Museum of Transport. The first engine was supposed to run on a homogenised coal dust/ oil slurry but it didn't work............... the engines were way too powerful for the ships giving a Dead Slow speed of 7.5knots and really should have been mated to a contollable pitch prop. They weren't terribly reliable but once started they ran beautifully smoothly. The unreliablity was on the starting and stopping but this was resolved with some major redesigning of the liners and piston crowns of the City of Oxford that transformed the engine's manoeuvrability. Part of the starting problem was a "dead band" detector that soemtime didn't detect that all 3 units were "in line" and the start assister didn't engage to give the engine a half a turn by hydraulic ram............. IIRC the City of Plymouth had the start assister detect a dead band start situation while the engine was turning at 220rpm, which didn't do it or the rest of the engineroom a lot of good. I left Ellerman's in 1988 to join P&O Containers and remember seeing the City of Oxford trading in the Malacca Straits in 1992/3 as the Hyundai Malacca. Prince Line also had two vessel fitted with the same engine - Crown Prince and Royal Prince I think. They were handed over to OOCL when Furness was taken over by C Y Tung Group. I am now in command of some of the Maersk Line ships at the other end of the size/ power scale.
 

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They weren't terribly reliable but once started they ran beautifully smoothly. The unreliability was on the starting and stopping but this was resolved with some major redesigning of the liners and piston crowns of the City of Oxford that transformed the engine's maneuverability. Part of the starting problem was a "dead band" detector that sometime didn't detect that all 3 units were "in line" and the start assister didn't engage to give the engine a half a turn by hydraulic ram............. IIRC the City of Plymouth had the start assister detect a dead band start situation while the engine was turning at 220 rpm, which didn't do it or the rest of the engine room a lot of good.
L.S.
The STARTING ASSISTER (JS3 DOXFORD ENGINES)

The S.A. consist of 2 pneumatic power cylinders (1) , on for ahead and one for astern
They are mounted vertically at the forward end of the engine and pivoted at the top so that the roller at the end of the piston rod can be engaged to a wheel (2) at the forward end of the crankshaft to turn the shaft the required amount.
Each power cylinder is brought in engagement by means of an engagement cylinder (3) acting through a lever mechanism (4)
They are disengaged at the end of the stroke and brought back to their storage positions by means of return springs (5)

These springs (5) will keep the power cylinders firmly away from the wheel (2) while the engine is running.
Special plates on the wheel prevent the ahead power cylinder from engaging in the astern grooves, and vice versa.

According the above story from "XFullFatTim" was the starting assister not ALWAYS a big success?
(Perhaps the spring 5 was broken in the above mentioned accident?)
Who can tell more about his experience with the starting assister?

Kind Regards
Alfons
 

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"That's always been my opinion because there are only 4 ways to increase the power of a reciprocating engine:"

Duncan
There is a fifth way, increase the revs.
Hmmmmm! Increasing RPM does not necessarily increase power as fuel burn time (cetane index), scavenging efficiency and gas flow rates are all going to compromise power output after passing through the "sweet spot" where max power and torque are produced.
 

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I was going to let that one slide, but as well as the issues that you raise Ian as the rpm increase the propellor efficiency starts to fall due to the effects of cavitation etc, whilst these can be alleviated by the use of tandem propellors the overall efficiency of conversion of potential chemical energy in the fuel to propulsive effort will fall. For most shipowners (warships being a notable exception) the overall plant efficiency for a given service speed is a prime concern. Also increasing RPM markedly will have considerable inertial effects which can be overcome by reducing cylinder diameter and increasing cylinder numbers which quite nicely brings us back where we started.
 

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I have served on a Post War 3 cy unit which was in the Egton, however, the pre War 3cy was (barring for the Scott-Still) one of the most highly rated Marine Engine's available at a mechanical efficiency at about 82% other's being around 73%
EGTON'38 SR(RUNSWICK/GLAISDALE Doxford "Economy")
 

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I sailed as 2nd Mate and Chief Officer on 5 ships operated by Ellerman City Liners from 1981 though to 1988 that had the last Doxford 3 legged engines built. They weren't terribly reliable but once started they ran beautifully smoothly. The unreliablity was on the starting and stopping but this was resolved with some major redesigning of the liners and piston crowns of the City of Oxford that transformed the engine's manoeuvrability. Part of the starting problem was a "dead band" detector that soemtime didn't detect that all 3 units were "in line" and the start assister didn't engage to give the engine a half a turn by hydraulic ram............. IIRC
L.S (XFullFatTim;624748)
I am curious to know, what means exact the major redesigning of liners and pistons crowns which transformed in better manoeuvrability?
According DOXFORD the starting assiter was only necessary 1 in 100 times starting?
This was find out on the testbed, perhaps in reality it was different?
Awaiting your answer
Kind regards
ALFONS
 

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L.S (XFullFatTim;624748)
I am curious to know, what means exact the major redesigning of liners and pistons crowns which transformed in better manoeuvrability?
According DOXFORD the starting assiter was only necessary 1 in 100 times starting?
This was find out on the testbed, perhaps in reality it was different?
Awaiting your answer
Kind regards
ALFONS
The piston and liner mods were to improve the compression, particularly when starting astern as there was a lead on the exhaust piston which made starting sometime a bit of a lottery with a bit of liner and piston ring wear!
I think the starting assister may have eventually been removed after a particularly exciting moment when it engaged on one ship when the engine was running at full speed (Applause)
I seem to recally that the frequency of "dead band" stops was much reduced when we changed the phasing of the propeller in relation to the crankshaft
 

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There is lots of interesting general Doxford stuff at www.doxford-engine.com
They have sent me lots of pics and meeting notes - quite poignant for me having been involved with the Js, JSs and, for my sins, the LBs. I must have been a very bad boy in my youth(Pint)
 

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L.S.
I never sailed with a 3-Legged, so I like to know, was that normal on a 3-Legged Doxford that you had 2 Spare Cylinder Liners on board?
That look much to me.

A HAPY NEW YEAR TO ALL THE DOXFORD LOVERS

Alfons
Certainly on the 58JS3s we only designed the ships to carry 1 spare liner but I seem to recall City of Bristol (2 x 60[?]LB3) that there were "quite a few" although I' not sure why as she ran on diesel and the wear rates were very low. However I think in her early days she had a few liners crack.
Someone was asking about the 58JS3s having the starting assister when the old LB3 didn't - I think that was 'cos the LBs had side cranks at 180 degrees to the main crank but all the turbo charged engines had the side cranks leading by about 8 degrees
B R
Tim G
 

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I sailed on a four cyl Doxford which carried four spare liners, which did not inspire confidence.
Curiously, it carried only one of each top and bottom pistons.
I think that some companies used their ships as a sort of a spare gear store.

The picture in #58 does not appear to be a three legger. Looks suspiciously like a centre scavenge at top of picture.

Happy New Year

Derek
 
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