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Joe,
One of the things that made me leave SMT was the time I was called into the Works Managers office, a 700kg brass bush went missing over the weekend previously when I was in carrying out repairs to a machine. They were asking me because I had a means of transport, I told them that my 90cc Honda step-through wasn't very well suited to doing wheelies along the Broomielaw.

It was discovered later that the part had actually been lifted 2 weeks earlier and taken away for machining.
 

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What were the advantages/disadvantages of the opposed piston marine diesel engines? I never sailed on a ship with one.

Frank
Not sure about efficiency. Main differences : no cylinder head; no big camshaft driving exhaust valves. Uniflow exhaust without an exhaust valve, although it could be argued that the top piston was effectively an exhaust valve. Easy to access cylinder for inspection /cleaning by 2 nuts on top piston. Drawback was a crankcase like a jungle with all the extra bearings.
 

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What were the advantages/disadvantages of the opposed piston marine diesel engines? I never sailed on a ship with one.

Frank
Mechanically, the Doxford LB design was complex; a four cylinder engine had one or two scavenge pumps, two camshafts, eight pistons, eight mechanically operated fuel injectors and 41 bearings, 17 of which were in spherical housings and 12 were steel on steel. However, being virtually vibration free, uniflow scavenging and common rail fuel system giving good fuel consumption and its fabricated steel construction resulting in a relatively light weigh , for a time it became the most popular engine with shipowners around the world
 

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Mechanically, the Doxford LB design was complex; a four cylinder engine had one or two scavenge pumps, two camshafts, eight pistons, eight mechanically operated fuel injectors and 41 bearings, 17 of which were in spherical housings and 12 were steel on steel. However, being virtually vibration free, uniflow scavenging and common rail fuel system giving good fuel consumption and its fabricated steel construction resulting in a relatively light weigh , for a time it became the most popular engine with shipowners around the world
Thanks,
 

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There's a nice little model of Taikoo made 4-legger in the Hong Kong Maritime Museum.
Only sailed on one Doxford, built under licence by Commonwealth Engine Works, Port Melbourne. No trouble with it at all, ran like a top. However, two other ships with CEW-built engines, Mount Kembla & Mount Keira, had no end of trouble with main and bottom ends. As an apprentice at State Dockyard, Newcastle, had regular overtime scraping and fitting new bearings. The cause of the trouble was never identified, to the best of my knowledge, but there was a strong suggestion that it was somehow a result of insufficient scantlings around the ER......
Those bearing problems could well have been cause by "locked " spherical bearings. If the ship was flexing together with the flexing of the crankshaft, the sphericals had to work hard to keep the bearing and pin surfaces aligned.
 

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Those bearing problems could well have been cause by "locked " spherical bearings. If the ship was flexing together with the flexing of the crankshaft, the sphericals had to work hard to keep the bearing and pin surfaces aligned.
Those bearing problems could well have been cause by "locked " spherical bearings. If the ship was flexing together with the flexing of the crankshaft, the sphericals had to work hard to keep the bearing and pin surfaces aligned.
Have just remembered a "spherical" story from > 50 years ago;
A 20 year old 67LB6 had been running without any problems when the company decided! to check the alignment. It was horrible! So they rechocked the engine and on the following voyage we had lots of bearing failures.. The problem was that the bearing sphericals had, over time, slowly settled into their required positions but with the realignment they were being forced into positions where ridges has formed so preventing the sphericals moving to positions to allow the bearing surfaces to run parallel. Many (un)happy hours were spent removing the bearings and grinding the ridges down.
 

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During a period of 60 years, over 1750 engines were built by Doxford and the licensees until [production ended in 1980 when the government of the day withdrew support of the industry. After resolving the initial centre crosshead and the more intractable combustion belt issues, the J-type was a successful design with 103 engines being produced and would have been much more successful if the directors had allowed licences to be issues. They had this stupid idea that in doing so the "foreigners" would be competing against British Shipbuilders and kill our industry. Well, we managed to do that very well without help from abroad! There was a nonsense at the end with the short- stroke 58JS3 engine; Doxford convinced the two shopowners, and themselves, that this engine was but a short development step away from the 58G4, Seahorse, engine but it was too late when the truth dawned. The crazy thing was that they had already successfully delivered a couple of standard stroke 58J4 engines and that would have been a much better route to use that as a basis for the 58JS3. However, maybe it had something to do with a new Technical Director wishing to make his own mark in the business. If that was the case, it was a black mark!
 

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I keep a little note of the interesting propulsion systems that I would have liked to sail with for the 'not dull' experience. Reading this thread I suppose I should add Doxford. I have only seen the single cylinder demonstrator that was at Saudi Shields and never 'in motion' as the poet might have it.

That does not mean I would have enjoyed a long trip. The short leg (well, one short anyway) from Lisbon to Las Palmas with a Grandi Motori filled that gap without overegging the cake.
 

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I keep a little note of the interesting propulsion systems that I would have liked to sail with for the 'not dull' experience. Reading this thread I suppose I should add Doxford. I have only seen the single cylinder demonstrator that was at Saudi Shields and never 'in motion' as the poet might have it.

That does not mean I would have enjoyed a long trip. The short leg (well, one short anyway) from Lisbon to Las Palmas with a Grandi Motori filled that gap without overegging the cake.
You can have a virtual Doxford experience by checking into YouTube. The twin screw one indicates how each cylinder makes a different noise. When a noise stopped it was not necessarily good news - often the prelude to something very bad happening ?
 

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The single cylinder at Shields had been Doxfords test bed and prototype, many variations over the years. Cadets got the change to see if we could start it right at the end of 4th year, spent time during the year renewing bits, installing new cooling systems etc. Then the go on the levers - most of us managed to get a short run out of her, you only got one chance.
 

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Hi
All but 1 of the Frank C Strick ships built from the end of WW2 had Doxfords. Ranging from 4 Cylinder LB`s to the J and P Types. The one exception was Aramanistan, bought from Bank Line as Elysia. (Workspoor? I think). I either sailed on or coasted most if not all, over a 9 year period. When I eventually went to Harrisons, they sent me to Adverturer, Guess What?, Another Doxford!.
 

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Lead - an interesting concept - on Bank Lines 76J6 Corabank Class the lead on the cranks was 9 degrees 28' but because of the differential stroke of the upper and lower pistons this translated to a difference of just under 2 degrees between IDC (Least combustion space volume) and TDC on the lower piston.

The 76J4C Fish class had zero lead - the engine would not stop naturally at a dead spot, but if it was left in one position after maintenance it wouldn't kick on air and had to be turned to a more suitable position.
They had to have the side crank lead to give early opening and early closing of the exhaust ports to get efficient scavenging on the earlier pulse turbocharged engines . However, they found with the constant pressure turbocharging on the later engines much more air was delivered, negated the need to open and close the exhaust ports early. They blamed BBC for not recommending the change earlier ?
 

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A nice model, how long did id it take you to build ........
Frank, Wheatking took about 6 months if I recall correctly.
Most of it was figuring out how to do a certain aspect.
Like the open cargo hold. This was decided upon after the hull was made and primed.
Ended up cutting the bottom completely off with a table saw. Ground out the hold(s) space, finished the inside of the holds and then glued a shim for the width of the table saw blade and the previously cut off bottom back to the hull and repainted it.
A bit of head scratching.
The rest was fairly straightforward ship model building.

Frank
 

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The first stern trawler/factory ship FAIRTRY had a Lewis/Doxford 480SB4.
Worth a read "The Fairtry Experiment" by Jack Campbell the story of how the Rusky's stole the idea
This is about a completly different Doxford. When I sailed on the British Escort March 1958 she had an experimental
Engine ,Three Cylinder Doxford with a Brown Boveray Turbine Supercharger, No Main Engine Pumps And all Auxiliary
MACHINERY were electrically powered ,the power was generated by two Large Mann Diesel Generators we still had to put the engine exhaust gasses through the boiler room furnace when we were full away
 

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I sailed on the Romanby with 67LB5 & 2 scavenge pumps, Wandby with 70LBDS4 & 2 scavenge pumps & 2 T/C, Thirlby with 65LBD6 & 2 T/C. The top X-heads were slackened and tightened with a 28lb sledge. On the Wandby the third and myself in the crankcase trying to slacken the piston rod nut failed with a 28lb and had to revert to a 56lb. In a later career as a surveyor ashore I only saw one other 56lb sledge (half an anvil) and wondered who tightened it and whether he had ever heard of metallurgy. I easily rang the bell at the Tivoli Gardens in Copenhagen with exercise like that.
 
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