# Hawthorn-Doxford Seahorse medium speed engine



## Steve Hodges (Feb 12, 2007)

I'm posting this under Ship Research because I would be interested to know if the Hawthorn/Doxford Seahorse ever got as far as a real ship!
When I was doing my workshop training with BP they sent me for six months in 1971 to Hawthorn Leslies engine works at the bottom of Byker Hill. Hawthorns were building Sulzer RNDs under licence, mainly for SD14s, but while I was there they started assembly of the prototype Seahorse. This fearsome device was ( as I understood it) a joint venture between Hawthorn's and Doxford, who I think were still building the "J" engine at that time. The Seahorse was an opposed piston medium speed engine designed to run at around 300rpm, if I remember correctly. The prototype was a four cylinder unit that was supposed to be capable of up to 10,000 hp, although it was considerably smaller than the SD14 engines. The main thing that I remember was that the crankshaft could be lifted out through one side of the crankcase/entablature assembly, so the whole cylinder" block" was overhung from one side with removeable struts on the other. The upper cylinders were driven by eccentrics of large diameter and narrow width, not cranks, which made the crankshaft a thing of wonder. There were lots of other weird innovations as I remember, but I will have to go and hunt out my Engineer Cadet's Logbook to see if noted any more details of the brute. All the lads in the erection shop were intrigued by the thing, we were all trying to imagine those upper pistons flying up and down five times a second. When I left to go to sea it was about 75% complete.
I know that the concept was reported in the technical press at the time, but I would like to know if it ever actually ran, and if it got any further than Hawthorn's test bed - does anyone know? The idea was to get the power and small size of a medium speed engine from a design with the robustness and reliability of a slow speed engine. Clearly it didn't take the shipping world by storm, and it probably had far too many innovations in the design. Many people have accused me of dreaming the whole thing after a bad curry, but it really did exist. Did anyone else see the Seahorse "in the flesh"?

Steve


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## gasman (Jan 28, 2007)

Steve,

I think this is the engine in the Beamish museum store, in County Durham.
Look up the Doxford Friends website.

The single cylinder Doxford prototype ex South Shields Marine and Technical college is at the Anson Museum , Stockport.

Regards,

gasman


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## R58484956 (Apr 19, 2004)

See http://www.doxford-engine.com/engines.htm. All details on Seahorse. No engines built commercialy.


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## fred henderson (Jun 13, 2005)

*Seahorse*

The Seahorse saga took place after I left Hawthorn Leslie, but as far as I can gather from my contacts, this was the history of the project: -

After preliminary studies costing £48,000, a joint company called Doxford Hawthorn Research Services Ltd was formed in June 1970 to build and develop a new marine / electrical power generation diesel engine, to be called Seahorse. (A stylised seahorse was the Hawthorn Leslie logo) The budget for the project was £260,000. 

Difficulties were experienced in securing Government financial support beyond the investment grant payable to development areas. This grant subsidised the construction of the prototype, but not the considerable development and testing costs. By the summer of 1973 expenditure had reached £414,000 and running trials were continuing. Financial assistance was provided for 18 months under the Science and Technology Act, but the three day week, labour disputes and the liquidity problems of Court Line (who by then were the owners of Doxford’s) halted testing for long periods. 

Testing did continue however and by mid 1976 the design was felt to be sufficiently mature to begin marketing the engine. By this stage Hawthorn Leslie had spent £784,000 on the project. Unfortunately the engine became a marketable product at a period of depression in both the shipbuilding and electricity generating industries. The following year the nationalisation of the industry took place and I understand that the project became a victim of the dead hand of British Shipbuilders.

Fred


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## Jim S (Jan 21, 2006)

As far as I know the development of the Doxford Seahorse engine was never completed mainly because of problems encountered with piston rings that were never solved. To limit production costs the engine was designed with a bore of 580 mm across the intended power ranges of from 10,000 bhp to 17,500 bhp with a range of cylinders from 4 to 7. and a speed of 300 rpm.
I believe the engine's demise was simply due to the competition being just too great.


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## Steve Hodges (Feb 12, 2007)

Thanks to all those replying. So it looks like the Seahorse never made it to the sea - somehow I can't help but suspect that this was a blessing to sea-going engineers. Still, it must have been a sight to see "in action", unless they chickened out and enclosed the top end completely!
Thanks again,
Steve


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## JKB (Jul 6, 2007)

I did the builders' sea trials on an Appledore-built container vessel years ago, this one, I think:
http://www.shipphotos.co.uk/pages/cervantes76.htm and I was sure it was powered by a Seahorse. It was certainly a small three-cylinder Doxford, new on the market and quite troublesome on trials.
From the posts so far on this thread, it seems I must be mistaken. Can anyone hazard a guess what it might have been?

Regards,
JKB, ex-Mirrlees Blackstone Service Department.


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## JKB (Jul 6, 2007)

I know it's bad form to reply to your own posts but a bit more digging reveals that the engine in question must have been an 58JS3.
What I definitely remember is the dead-band gear which automatically barred the engine round to a viable start position if it was in a dead band. For some reason it decided to join in when the engine was already running at one point, which did the job no good at all.

Regards,
JKB.


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## Jim S (Jan 21, 2006)

Hi JKB,
The engine that you refer to in the Appledore container ships was probably the Doxford 58JS3 - This was a 3 cylinder 580mm bore J type engine that was basically a slow speed version of the Seahorse. Hence the designation 
58JS3. These container ships were built around 1979 for Ellerman and Prince Line (possibly others). This basically marked the end of the once renowned Doxford.
See also the Doxford section in "Engines & Ship Mechanics"


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## 760J9 (Jul 22, 2007)

tom scott.
Have a lot of test data and Doxford Engine works reports on Seahorse. The info you have is correct. Seahorse never entered service. Container ships fitted with 580JS3 engines, ten built, one is at Beamish. If you want further info please say


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## Tim Gibbs (Apr 4, 2012)

Jim S said:


> Hi JKB,
> The engine that you refer to in the Appledore container ships was probably the Doxford 58JS3 - This was a 3 cylinder 580mm bore J type engine that was basically a slow speed version of the Seahorse. Hence the designation
> 58JS3. These container ships were built around 1979 for Ellerman and Prince Line (possibly others). This basically marked the end of the once renowned Doxford.
> See also the Doxford section in "Engines & Ship Mechanics"


I was project engineer for the 5 Ellerman 300 TEU container vessels. The 58JS3 was fairly bad news from the start. We were severely misled by British Shipbuilders/Doxfords by telling us that it was basically a 220 rpm version of the Seahorse when in fact it was VERY different . For example the Seahorse had 4 injectors /cylinder when the 58JS3 initially had only two . They eventually admitted after trying for 2 months on the test bed to get it to run, that they would have to redesign it with 4 injectors. Also, the Seahorse was designed as a unidirectional engine whereas the 58JS3 was to be direct reversing and there were problems running astern because of the large lead on the top piston stroke. And so it went on ....
It's over 40 years ago now but I think the first engine was nearly 9 months late. It was but a very few years later I was fitting Wartsila 9R32s developing the same power and weighing 60% less and they ran and ran.... !


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