43096
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37292 (I think it was) was experimentally uprated to 2000hp in the early 1980s. It reverted to standard after it went through Crewe Works for HGR and renumbering as 37425.
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Hastings units Class 201 to 207 : 500hp to 600hp ?
- Thread starter Justin Smith
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Indeed. I never had one fail. They were most impressive when the heaters were on because the engine would idle at a higher speed. When they took power the revs would die away briefly before it erupted!
It's usually the oil seals on the shaft bearings that fail. The lubricating oil then gets sucked into the compressor housing and mixed with the charge air, so when it reaches the cylinder and further fuel is added you end up with an overfuelled condition (i.e. too rich a mixture) and on a diesel that will mean a lot of black smoke. This is is a sign of incomplete combustion and the fuel-rich exhaust gas can end up combusting when it reaches the hot turbine wheel or exhaust components (hence the flames from the exhaust). This can lead to over temperature of the turbine wheel, which can cause further damage and possibly even complete failure.of the turbine or bearings.
The other issue with the engine's lubricating oil being drawn into the inlet via failed turbo oil seals is that when the fuel supply is shut off, the engine can potentially 'run on' using it's own oil as the fuel (i.e. a runaway), and if not promply stopped by cutting off the inlet air supply as well it will lead to destruction of the engine.
Intercooling has a much bigger effect as the engine capacity increases, due to the increased volume of air that needs to pass through the turbo and inlet tract and therefore the amount of heat that air can lose before reaching the cylinders. The EE 4SRKT was only 4 cylinders and at 15.4 litres per cylinder that gives 61.6 litres, less than a quarter of the size of the Sulzer 12 cylinders. At 600hp for the MS200-equipped version it roughly matches the hp-per-litre figure for the non-intercooled Sulzer 12 cylinder.
The rule of thumb regarding turbocharging is that for non-intercooled applications the maximum possible power gain is around 65% before detonation becomes a hazard due to the heat of the charge air in the cylinders before the piston starts it's compression stroke. The original non-turbocharged EE '4K' engines were rated between 170 to 400hp. If we were to pick a conservative downrating to 300hp, then the addition of the MS100 turbo gave a power increase of about 65%. The upgrade to the MS200 turbo would give an increase of 100% from 300hp which breaks the rule of thumb, so the increase to 600hp was most likely a combination of the higher boost pressure from the uprated turbo and the unboosted engine power rating also being increased (likely to around 360hp, to get to the 65% rule of thumb figure). This is exactly what you would expect, of course - higher charge pressure will require more fuel to be injected into the cylinders to maintain the required fuel/air ratio.
Up until the mid-1980s it was common for turbocharged road cars not to be fitted with intercoolers either. though models built as 'homologation specials' to be used for racing and rallying would usually be fitted with them from the factory to allow for increased boost levels to be used in competition.
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That sounds like an issue with the boost pressure level that the wastegate is activating at (there is probably a boost pressure leak in the line between the inlet and the wastegate actuator). The wastegate is used to regulate the turbo boost pressure - if the boost pressure in the inlet exceeds the preset maximum value (which is usually set by the pressure of a spring that acts against the diaphragm of the wastegate actuator), the wastegate will open to allow exhaust gas to bypass the turbo, which causes the boost pressure to drop and the wastegate will then close. This can be seen by the cloud of black smoke from the exhaust after each 'chirp' is heard - the wastegate is opening, causing the boost pressure to drop which then causes an overfuelling condition in the cylinders, and hence the black smoke which reduces when the boost pressure climbs again.
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This is some great technical information @Prime586, thanks for taking the time to write it out.
I worked in an HGV garage when I was young for a few years and a lot of this is a little hazy now but what you’ve said is ringing a few bells in the recesses of my brain…
Strathclyder
Established Member
That definitely explains why the turbo scream is still audible. I was on the right track (ha) at least when I said that it was turbo-related or at least adjacent. Cheers for the detailed explanation.
Justin Smith
Established Member
Just doing a bit of casual research and discovered the 500HP version of the EE 4SRKT mkII (turbo & 4 valve head) gave 8.1hp/litre at 850rpm, which is exactly the same as the (turbo charged but non intercooled) EE SVT, as fitted to the C20, C31 and C40 in 8, 12 & 16 cyl versions respectively.
The 600hp version produces 9.7hp/litre at 850rpm which is exactly the same as the (turbo charged and intercooled) EE CSVT, as fitted to the C37 in its 12 cyl version.
One wonders why they used intercooling to achieve this in the locos, but only a bigger turbo in the Hastings units ?
As an aside, the next version on (the CSVT mkII) as fitted to the NI class 101 and C50 (in 8 and 16 cyl versions respectively) produced 11.0hp/litre, again still at 850rpm.
The engine then became the Ruston Paxman 16RK3CT (as fitted to the C56) and produced 13.2hp/litre at 900rpm this time.
Later still it became the 12RK3ACT which was fitted to the C58s (in 12cyl form) and was producing 17.8hp/litre but now at 1000rpm.
Finally, in 1980, the bore was increased from 10" (254mm) to 270mm and it became the RK270. As far as I am aware this engine was only ever fitted to two locomotives (37905 and 37906) ?
The 600hp version produces 9.7hp/litre at 850rpm which is exactly the same as the (turbo charged and intercooled) EE CSVT, as fitted to the C37 in its 12 cyl version.
One wonders why they used intercooling to achieve this in the locos, but only a bigger turbo in the Hastings units ?
As an aside, the next version on (the CSVT mkII) as fitted to the NI class 101 and C50 (in 8 and 16 cyl versions respectively) produced 11.0hp/litre, again still at 850rpm.
The engine then became the Ruston Paxman 16RK3CT (as fitted to the C56) and produced 13.2hp/litre at 900rpm this time.
Later still it became the 12RK3ACT which was fitted to the C58s (in 12cyl form) and was producing 17.8hp/litre but now at 1000rpm.
Finally, in 1980, the bore was increased from 10" (254mm) to 270mm and it became the RK270. As far as I am aware this engine was only ever fitted to two locomotives (37905 and 37906) ?
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I’m not sure of answer to this but could it have been that fitting a larger turbo would have been a simple and fairly cheap way to gain some extra power, whereas to retro fit an intercooler would have involved substantial alterations to pipe work in a limited space that wasn’t originally designed for one?
I'm pretty sure that was exactly it. Unlike the engine installation in a locomotive, where generally staff would not need to travel through the engine room while it is in service, on the Hastings units provsion was required for access between the cab and the guard's compartment, and as such the radiator was built into the body side with the coolant pipes routed around the roof and cantrail, and air was drawn through it via the crank-driven roof mounted fan.
As mentioned in my previous post, intercoolers are required when higher levels of boost pressure are used. Retaining the MS100 turbo but fitting an intercooler would provide very little performance benefit as it was already running at it's boost limit. Fitting an intercooler along with the upgrade to the MS200 turbo would have provided the ability to go past 600hp, but to use that excess power the generator and traction motors would have also needed to be upgraded as well (as would the cooling system - the extra plumbing to the intercooler and a bigger or second radiator would have been required to cool the intercooler and the now hotter-running engine). Increasing the boost to go past 600hp would also increase fuel consumption (you can't use the extra air without adding fuel) and increase stress and wear on the engine. At that point instead of increasing boost pressure you would start looking at increasing the engine capacity to get the same power output by upgrading to a 6-cylinder engine, which would be under less stress.
It was therefore presumably far simpler and cheaper to slightly uprate the engine and have a modest increase in boost pressure by fitting a bigger turbo when building the subsequent classes for routes where a bit more power would be required.
As an extreme example of the engine stresses at high boost levels, the Ford Sierra RS500 Cosworth in road spec produced 224bhp from a 2-litre engine at 0.7bar boost pressure, and was expected to undergo normal road car servicing intervals and have a life of over 100k miles. In Group A racing trim the boost pressure was increased to between 2.0 and 2.9 bar and power output increased to between 500 and 600bhp. It was not unusual that after the longer races (such as the 3000-mile RAC Tourist Trophy held at Silverstone) the engines would essentially be scrap due to the blocks and heads being cracked and warped by the extreme heat and cylinder pressures.
The Hastings units were narrower that the rest. Maybe that was a factor? The pair of EE507 motors are rated at 500hp. So the extra 100hp in the uprated engines was useful to offset transmission losses and hopefully have some power left for light and heat, whilst still delivering full power to the motors.
Justin Smith
Established Member
Ahh so the Hastings units were electrically heated, which is obvious I suppose but did they use any of the excess heat from the engine cooling system at all ? It would be very efficient if they did!
I'm fairly sure that all the DEMUs had electric heaters throughout. As I mentioned in an earlier post, the engine ran faster when the train stopped in cold weather, compared with summer.
Wasn't the main reason for the engine uprating due to the lines the later classes operated on having steeper gradients? The 600hp modification initially came about when the 2-car Hampshire units were extended to 3 cars, and at the same time they were fitted with new bogies with 90mph expresss gearing. This proved to be a bad combination for the gradients on the line, especially in winter when the heating load was on maximum or when wheelslip was encountered in autumn. The temporary solution was to go back to 2 car formations, and the units were subsequently converted back to 75mph gearing which allowed the third coach to be returned. All subsequent units were built with the 600hp engines and suburban gearing.
A ETH Mk1 coach drew about 28A at 800V from the loco supply when the heating was on. The Hastings DEMUs were fitted with a main generator capable of up to 600A at 550V, and two traction motors each rated at approximately 240A, so that gave about 100A excess generator capacity at full engine speed to cover the heating load for 3 carriages. At low speed and while coasting the heating output was reduced however, so initially the Hastings units were fitted with a switch so the driver could raise the RPM while stationary. The control system was subsequently modified to automatically raise the engine RPM when the heating was on and the speed controller was moved to the idle position.
That would have required lots of extra pipework, flexible couplings and joints, all of which would become opportunities for leaks. A bit of leaking from steam heating pipework is acceptable, but you can't afford to lose any of your engine's coolant. Also, the radiator for the engine was not that large (diesel engines work most efficientkly when there is some heat in the combustion chambers, hence the use of glow plugs when cold) and I suspect it would struggle to provide sufficient heat output for two and a half carriages.
Besides that, it was right on the cusp of ETH being introduced, and as the DEMUs were based on standard carriage designs and components for cost reasons it would have been sensible to standardise on what was going to become the new standard heating system rather than design something bespoke. The Blue Pullman sets, designed and built in the same period, also used electric heating, supplied by auxilliary diesel generators fitted to the underframes of some of the trailer cars.
ac6000cw
Established Member
As the "Advantage" mods include fitting modern high pressure common-rail electronic fuel injection, I'd assume so. But GE locos have long had a reputation for slow 'loading' anyway - it's not accidental that older/rebuilt EMD locos are still favoured for yard and local freight work.
I don't know. Perhaps the Hastings units were found to be rather slow? The Hastings line is not flat. There are stiff climbs out of Tonbridge in both directions. I think it more or less climbs to Wadhurst in both directions. I'm no expert on that line. Others will know better.
Gloster
Veteran Member
I think that the original uprating was because overcrowding on the Hampshire units when new resulted in the construction and insertion of a Trailer Second. As 500 h.p. wasn’t enough for a three-car set, this was the solution. (It still wasn’t enough for Alton trains ‘over the Alps’ and they were usually two-car sets.)
The Hastings line crosses the Kent/Sussex Weald so yes it is hilly.
Southbound the main climbs are Hither Green-Knockholt and Tonbridge-Frant.
Northbound the main climbs are Etchingham-Wadhurst and Tonbridge-Sevenoaks.
The original Hastings units were 6 car sets with two motor cars with 500hp engines, so 500hp for 3 cars was considerd adequate for the Hastings line. BR presumably thought that 500hp would have been enough for the Hampshire units with only 2 cars, but with the addition of the extra car more power would be required. I still can't fathom the thought process behind fitting them with express gearing at the same time though, if speed ascending gradients was already a problem.
The usual rough rule for a diesel engine is that a third of the energy comes out as work, a third of it as coolant heat, and a third of it as exhaust heat. All very approximate and variable of course but if the engine can put out enough work for you to tap a bit off for heating then it can definitely put out more than enough heat.
DMU power cars used a coolant-powered heater in the driver's cab, and I think something or other once made a feeble attempt at using the exhaust heat which leaked fumes through the heat exchanger, but overall the record of making any use of all that waste heat is pretty appallingly empty. Shame the Kitson-Still was never properly developed.
Reopened for @Justin Smith
Justin Smith
Established Member
I do not think we have discussed the Northern Ireland DEMUs (the class 70s, 80s and 450s).
As I understand it they have the same engine but that gives out 550hp, i.e. different from the 500hp or 600hp of the aforementioned English units !
As far as I can tell the NI units develop max power at the same rpm as the English engines (namely 850rpm), so does anyone know what is different about their tuning to produce a different max output ?
As I understand it they have the same engine but that gives out 550hp, i.e. different from the 500hp or 600hp of the aforementioned English units !
As far as I can tell the NI units develop max power at the same rpm as the English engines (namely 850rpm), so does anyone know what is different about their tuning to produce a different max output ?
I read somewhere the 37s were kept at 1750hp because BR only had been budgeted to purchase type 3 locos, not type 4 (and anything rated between 1750-2000hp wouldn't fit either category). Though it does seem that one was experimentally uprated to 2000
hexagon789
Veteran Member
70 Class were set at 550bhp, so the 450s (bar one unit) were the same.
The 80 Class were set at 560bhp gross, 530bhp traction with traction motors quoted as 265bhp maximum, 235bhp continuous - these had additional ventilation added as the power cars were originally intended to be used as back-to-back pairs on freight duties.
As to what produced these different ratings, I have some books that might explain it but I won't be able to get my hands on them until Friday evening.
Easiest way to think of it is that basically any internal combustion engine is a big air pump, and the more air it pumps the greater it's power output in the sense that more air pumped means more fuel burnt means more power developed. All a supercharger/turbocharger/blower does is increase the air mass pumped by the engine - and that isn't necessarily dependent on engine speed.
Don't get hung up on the Max RPM figure. The strength of the engine's internals decide what the rev limit is (usually the crankshaft, pistons, conrods, big end bolts and main bearing bolts). The Max RPM for the whole EE 'RK' MkII engine family was 850rpm. The power output in these engines is a function of displacement (bore x stroke and number of cylinders), turbo boost curve and fuel delivery curve.
Diesels generate power through torque (due to the high compression ratio required to get the fuel to ignite) rather than revs.
I imagine as they came after the Class 205s they used the same 4SRKT Mk2 engine and Napier MS200 turbocharger, but with the maximum boost pressure turned down and fuel cam reprofiled to match.
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Romsey
Member
The Hastings units and later Hampshire and Oxted units were restricted to 75mph which in the 1950's was reasonable for keeping up with steam hauled passenger services. In their latter years the Hampshire units would only reach 75mph down hill with a following wind.
All the Southern DEMU's were electrically heated which caused problems at times. To provide the heat the idling speed was higher and used to wander up and down every few seconds, perhaps coupled to the thermostats in the passenger accommodation. Eastleigh Train crew supervisors used to ask that units between workings at Eastleigh were turned so the power car wasn't next to their office. Once turned to power car was then outside the TOPS office at Eastleigh or the supervisors office at Portsmouth Harbour - which led to more requests to turn the unit. ( Control noted and normally did nothing and claimed "maintenance swap" if the same unit returned and hadn't been turned.) I think someone mentioned that the cab in the power car was heated by a radiator coupled to the engine cooling system. I think that the guard had a radiator as well.
hexagon789
Veteran Member
Further research reminded me that when new the 70 Class were rated at 600bhp, but were later derated to 540bhp.
Strathclyder
Established Member
The 12th 450 used a written off (accident damaged) 80 class unit's internals, I seem to recall? There were only 11 70 class units, so the 12th 450 had to have gotten it's internals from somewhere.
hexagon789
Veteran Member
Yes, one power unit came from a withdrawn 80 Class - 88, which was involved in the accident at Hilden in March 1983.
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The 1750hp rating was for reliability purposes. Additionally, EE had offered to uprate the later built 40s to 2400hp (assume with same turbos as the 205 units) but BR declined to ensure reliability. Certainly would have made the 40s a much better passenger loco giving a 45 a run for its money?
Strathclyder
Established Member
Cheers for the memory refresher. That's what I remember reading somewhere before, but just couldn't remember the specifics. The 450s truly were Frankenstein units in every sense, more so than any NI/Irish DMU built before or since imho.