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Restoration diary

Reports of restoration work on 50029 and 50030.

Work party reports 30th November 2015 and 17th January 2016

Work party reports 30th November 2015 and 17th January 2016
The reverser for 50030 with the air connection temporarily attached to the actuator. We successfully operated the air valves from an off board compressor to prove we had the correct connections.
On 15th November, Ian, Pete and Dave continued filling the power unit with the new oil, checking for leaks along the way, and blanking off pipes that cannot be fitted before the PU is lifted back into Repulse. Dom and I continued belling out the electrical cubicle wiring, and completed all the cables from the compressor, rad fan, ...
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Working party report 31st May 2015

Working party report 31st May 2015

Ian Kemp, Peter Carter and Dave Rolfe carried on fitting oil, water and fuel pipework to the ex-50008 power unit, but on the side facing Renown, so no photo opportunities were possible today.

In preparation for the open day on June 21st, I washed down the outside of the electrical cubicle frame in 50030 and undercoated it, as it had become dirty from repeated handling since it was originally painted about five or six years ago. I also cleaned and undercoated the two cubicle doors from the fuse and MCB compartment. I brought three more cubicle doors home to clean.

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Just a reminder that we are having our Open Day on the afternoon of Sunday June 21st where RRRG members will be on hand to give guided tours of the project and discuss progress. We hope to see you there!

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Working party report 24th May 2015

Working party report 24th May 2015

Ian Kemp, Peter Carter and Wes Needle continued fitting coolant and oil pipework to the power unit, while Dave Rolfe carried on painting the other side of the power unit.


I removed the battery charge contactor so I could clean and undercoat the compartment where the CU2 and CU7 go, then did the same for the compartment underneath where the CU1 sits, in readiness for having them temporarily fitted for the open day. Topcoat will be applied next workparty. I also cleaned the dirtiest two of the cubicle doors ready for painting.

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Electrical restoration: Class 50 control units

Electronic Control Units

One of the major talking points when RRRG first acquired 50029 and 50030 was the availability, or otherwise, of the various electrical control units. The Class 50 has a reputation for being electrically complex – some would say needlessly so.  Pre-refurbishment they were even worse as EE (with assistance from BR) had tried to produce a jack-of-all-trades locomotive.  Many of the features were either rarely used or prone to faults, and most were removed by BR during refurbishment.  The electronic control units are mostly unique to the 50 although some are common to other late-build English Electric locomotives.  Unsurprisingly, all the control units had been removed from 29 and 30 before we bought them and so we had to obtain replacements.  We also felt that it would be worth trying to update the electronics to modern specifications where possible, because the 1960s designs either use completely obsolete components for which no modern equivalents exist, or incorporate design faults, or both.

This is a list of the various control units in a Class 50 and how we have obtained them or can obtain them if we still need them.

CU1 – The main control unit CU1 is the central “brains” and obtains information from a number of different sources, namely from the cab controls, engine load condition (from the load limiting potentiometer) and from the traction currents.  This information is passed to the CU3 and in turn the engine governor.  We have one complete, tested unit, one complete and untested unit and the parts to make up another.


CU2 – the field divert unit, the electrical equivalent of the gearbox of the locomotive.  It controls the three stages of field weakening which occur at approximately 25, 40 and 60 mph depending on trailing load and ruling gradient.  We were missing this item from both our locomotives and the former owners of 50021 kindly loaned us an example which we took to an electronics specialist company who “cloned” it and built us two copies to modern standards.  Ironically, shortly after this, we were able to purchase an original Class 50 unit, though this has yet to be tested, however the original EE unit is known to be very reliable in service.




CU3 and CU6 – also known by its EE designation KV10. The CU3 sets the field current from the main generator as a summation of all the input signals and the CU6 similarly controls the ETH generator output. The main body of the unit is identical but is turned into a CU3 or CU6 by adding a CU3A or CU6A daughter card. Originally we had no KV10s but we adopted a policy of buying them whenever they came on the market in the intervening years and we built up quite a collection. However the KV10 is a classic case of obsolete and temperamental electronics and a respected locomotive electronics expert brought a rebuilt version to market some years ago with completely modernised components. We felt that ordering two each of the rebuilt CU3 and CU6 units for 50029 and 50030 was money well spent. The owner of 50008 Thunderer has also chosen to fit these modernised KV10s and is gaining operational experience with them which will prove invaluable to RRRG.  The new design incorporates the electronics of the CU3A or CU6A into the main unit and eliminates the need for a daughter card.

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CU4 – coolant control unit.  This unit is designed to monitor the temperature of the cooling water in the two coolant circuits and open/close valves to route the flow of water correctly.  It also sends signals to the CU5.  We have none but the Class 50 Alliance has developed a modernised unit which will be made available to us in due course.  It would have been possible to recreate the original CU4, which was built for EE by Hawker Siddeley, but the new design employs proven marine technology which would be acceptable to Network Rail (an important consideration for the C50A) and, together with a C50A-planned CU5 rebuild would eliminate "bugs" in the system which can cause the engine to be over-cooled in some circumstances.


CU5 – radiator fan control unit, it receives the signals from the temperature probes via the CU4 and controls the speed of the radiator fan accordingly.  We had none but again we were able to borrow one from another Class 50 owner.  Adrian Spencer of Cotswold Mainline Diesel Group, another noted locomotive electronics expert, was again able to copy this circuit and build a copy using modern electronic components.  We have also taken the opportunity to have a batch of the temperature probes remanufactured, in partnership with other Class 50 owners.

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CU6 – Regulates the output of the ETH generator. This is basically the same as the CU3, but adjusts the ETH generator field strength to suit varying load demands according the number of coaches requiring electrical heating.

CU7 – ETH field detector unit.  Basically it sees if there is a feed from the coaches which allows the ETH generator to electrically heat them.  It also detects if an ETH fault occurs in a coach, and if one does, in conjunction with Heating Over Volts Relay, it switches off the ETH feed to the coaches and returns the power unit to idling.  It also detects voltage from two 50s in multiple and prevents “doubling” of the ETH supply if this is the case.  This is a fairly simple circuit which I was able to rebuild and install in 50030.  I also obtained the parts to build one for 50029 in due course.  It was a CU7/HOVR fault which caused 50050 Fearless to shut down during the "Fifty Terminator" railtour of March 1994 as for some reason the engine was shut down instead of being returned to idle.

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The CU8 designation was never used, for reasons lost in the mists of time, so isn't relevant to our restoration project.

The CU9 is the automatic voltage regulator, or AVR, and basically maintains the output from the auxiliary generator at 110v DC so the compressors, exhausters and motor blowers do not overspeed.  There are two types: electronic (CU9A) and carbon pile (CU9B), both types are compatible and there is one per locomotive.  The majority of Class 50s were fitted with the original ‘Carbon Pile’ unit, and ten 50s were fitted with an electronic version, but because the electronic types additionally controlled battery charging and also contained gas-sensing equipment, their complexity apparently made them unreliable and were replaced with carbon pile units, which are slower reacting but more reliable.  We have an overhauled CU9B for use in 50030 plus two untested CU9Bs.  We may decide to commission new build versions as this unit can also be improved upon with modern electronics, effectively producing an updated CU9A.  We are currently unaware of anyone who could test our CU9Bs and this is also something we need to consider.

The CU10 is the speed control unit.  It's also known as the ‘AEI’ unit after its manufacturer, the Birmingham company Associated Electrical Industries.  It is a complex device that receives signals from the axle driven transmitter unit, and sends signals to the cab speedometers.  It can be adjusted to take into account wheel-wear.  Six card slots but not all these are used on a 50.  One CU10 per locomotive.  We have two units plus some of the control cards, but as the Class 50 Alliance have designed a modern version, we will probably obtain one in due course.

CU11 was the slow speed control unit which was removed at refurbishment.

The CU12 is the lighting delay timer.  It turns off unnecessary lighting 15 minutes after engine shutdown, such as internal lighting and marker lights, should they be left on and the main battery isolation switch be left in the ‘ON’ position. One per locomotive.  It's questionable whether this unit is really necessary for preserved line use, as it was really designed for times when a 50 might finish its BR duties and then be disposed of on depot by a driver with other things on his mind, so that he might forget to turn the lights off and the batteries would be drained and the locomotive subsequently failed the next morning.  This unit is actually still present in 50029 so we could use this as a template to make one for 50030, if we feel we need to.

Things Still To Do

We still have to tackle the difficult, and probably expensive, issue of the severed traction and ETH cabling under the cubicle.  I have been advised not to through-crimp traction cabling, so it will need replacing with new cable at some point.  We may have to use the services of a specialist contractor for their replacement.

The brake frame needs rewiring once the exhauster underneath it has been changed for an overhauled one.  The Driver’s Safety Device (DSD) relay box needs new cabling laying in as the original cables have long gone, likewise for the DSD speed switch in the cupboard underneath the hotplate in No.2 cab.  The comprises several pieces of equipment, including relays plus hand and foot operated switches, which automatically shuts off power and initiates a full brake application after 5-7 seconds if the driver becomes incapacitated and removes his foot from the pedal in the cab.


All the cab desks need the cable crimps cleaning, the lampholders behind where the instrument panels go will need either cleaning or replacing, we still have to source or make the switch panels that go in the ceiling above the driver, and the master controllers need freeing off much more than they are now.  The traction motors will need removing for overhaul, and the traction cable connection boxes under the locomotive will need refurbishing.  The overhauled exhausters and compressors will need reconnecting once fitted.

The engine governor and the load limiting potentiometer, or vane motor, need overhauling.  The electrical rebuild of 50030 has been challenging yet very satisfying.  Anyone fancy helping with 50029?

We still have to tackle the difficult, and probably expensive, issue of the severed traction and ETH cabling under the cubicle. I have been advised not to through-crimp traction cabling, so it will need replacing with new cable at some point. We may have to use the services of a specialist contractor for their replacement.


The brake frame needs rewiring once the exhauster underneath it has been changed for an overhauled one. The Driver’s Safety Device (DSD) relay box needs new cabling laying in as the original cables have long gone, likewise for the DSD speed switch in the cupboard underneath the hotplate in No.2 cab.


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All the cab desks need the cable crimps cleaning, the lampholders behind where the instrument panels go will need either cleaning or replacing, we still have to source or make the switch panels that go in the ceiling above the driver, and the master controllers need freeing off much more than they are now. The traction motors will need removing for overhaul, and the traction cable connection boxes under the loco will need refurbishing. The overhauled exhausters and compressors will need reconnecting once fitted.


The engine governor and the load limiting potentiometer, or vane motor, need overhauling.

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Electrical restoration of 50030: what we've done, how we've done it and what's still to do

Electrical restoration of 50030: what we've done, how we've done it and what's still to do

This article came about after a discussion between myself and Dom Jackson, and is intended to give an idea of the difficulties and problems faced during rebuilding of the electrical cubicle in 50030 Repulse.

When we acquired The Twins, I had already discussed with our original Chairman Paul Taylor where my skills and interests lay, and as such, at the first work party in November 2002, he asked me to go through both locos to see which had the most complete electrical system, which would give him an idea which locomotive would be the most viable to begin work on.  Having never been inside a 50 before, I didn't really have any idea what to expect, but I was shocked at how little remained of the electrical systems of both locomotives. After inspections by various people, the consensus was Repulse was in better overall condition, and so it was decided she was to be restored first.

The electrical cubicles of both locomotives were totally stripped, with the exception of nine of the 18 NR28 relays left in Renown, and I soon realised these had only survived because they were at the far end of the Thin Man's passage, in the most difficult compartment to get at. Both locomotives had various terminal bars missing, and there were cables hanging and lying everywhere.


Paul asked me to be his electrical officer, but I remember telling him that unless he could obtain detailed wiring manuals, there would be little chance of me being able to rewire the cubicle as I knew little about 50s at the time. He assured me he was getting copies of the manuals, so I gave him the benefit of the doubt and agreed to come to the next few work parties to start clearing the debris from in and around the cubicle.

One of the first tasks was to install fluorescent lighting in both locomotives so we could see what we were doing, and a few weeks later Paul made good on his promise and presented Mark Tinker and myself with copies of the wiring manuals, and I duly accepted the role of electrical officer. Mark Tinker was actually a qualified electrician, but decided the formal post of electrical officer wasn’t for him. One of the manuals showed the positions of the various electrical items in the cubicle, and the other gave details about what each piece of equipment was connected to, and with what cables.  There then followed several weeks of poring over these manuals, and I began to have an inkling of what went where, though at that time we had no electrical equipment, so I didn't know what most of the items looked like.  Mark and I began by trying to read and identify those cables that still had readable markers on them, adding our own labels written on masking tape. We were helped somewhat by many of the cables still being tied in bunches, so we were able to start placing them in approximately their correct positions.

We visited MoD Bicester to see the work Paul Spracklen was doing on 50026, and he agreed to sell us some of his spare electrical equipment. However, once I was able to examine it in more detail back at Rowsley, it quickly became apparent most of it was really only useful for spare parts. It was heavily corroded, with many missing or broken parts. We had also by then managed to obtain a quantity of NR28 control relays, so I decided to start cleaning and installing them. Shortly after this I found a supplier in Birmingham for the correct BR-spec cables. The actual manufacturer was still Brandrex, the distributor now is Anixter. Fortunately, all the cable sizes we needed are still used in the railway industry so, whilst expensive, they were readily available. To date I've installed just over 900 metres of control cabling into the electrical cubicle in 50030.  A short while after this, we managed to obtain much of the electrical equipment we needed when the owner of 50023 Howe decided to sell up. This time the equipment was in much better condition, and after stripping and cleaning, was ready to be installed. I attached all the control cables from each piece of equipment as it was fitted, and laid them in to their approximate destinations, carefully marking each cable with masking tape. In this way, by the time the last piece of equipment was fitted, all it's control cables were already there. On the occasions when Mark was not there, Neil Favell gave me much appreciated help.


Cable lengths vary from less than a metre, to six or seven metres depending on how far apart the items to be connected are, and the route you have to take through the cubicle. This means that on the days I had help, we were often able to install up to 20 cables, whereas on days when I was on my own, I'd be lucky to do half that.


A further visit to where 50026 was based after it left MoD Bicester revealed their spare electrical cubicle retained all the compressor, exhauster, earthing and neutral cabling, and many of the required insulators. A deal was struck and we purchased the cubicle frame, which I stripped of all the cables and insulators and fitted them into Repulse.


Part of the haul from Howe gave us the missing cubicle terminal bars which, after cleaning, were fitted into Repulse. This allowed many of the original control cables that we had identified to be reconnected, and all of them have now been done. Refitting and reconnecting these terminal bars however in the Thin Man's passage, takes a terrible toll on the knees, with the combination of very restricted space and the chequerplate flooring.


Wiring the NR28 relays with the new cabling also presented its difficulties at the far end of the Thin Man's, as the compartment is small, dark, at shoulder height, and the relays are quite close together. In contrast, the other nine NR28s behind the cubicle switch door are much easier to get at, as the floor level is higher and there is a much wider passage to work in.


The cubicle switch door we obtained from Paul Spracklen was missing all four of the rotary switches, and only retained the ammeter, fuel priming and local start push buttons. I enquired with several 50 owning groups, but they either had no spares or were unwilling to part with any spares they had, which was quite understandable. Fortunately, one elec manual showed the manufacturers of each electrical item, and I saw the rotary switches had been made by a company called Santon, who I was already familiar with from when I worked for an industrial electrical manufacturer, as they were the Midlands distributor for Santon. And yes, it's the same company that makes electric showers!


I contacted Santon and asked if there were modern equivalents for the four we needed, and to my surprise, when I gave them the part numbers, they told me all were still current stock items! Just goes to show that if you have a good robust design, why change it?


These four switches were not cheap by any standards, the largest one costing almost £200 itself, but we needed them so their purchase was agreed and they duly arrived. After fitting them I laid in all the cables from them, no less than 57 separate cables.


By the time it came to fit the compressor and radiator fan contactors, the larger cabling we had obtained from 50026 was already there and just needed connecting up. Obtaining the large curly ballast resistors on top of the cubicle took some time, and when we finally got them, it took both Mark and I with our heads up against the roof to fit them and connect the cables.


In front of the large field divert resistors on top of the cubicle are the 18 smaller green resistors which are mostly to operate the various cab warning lights. These lights are always on dimly, and glow bright if a fault occurs. This also ensures that if a fault light is not lit at all, the lamp has blown and needs changing. After we obtained these green resistors I then had to attach all 76 cables to them which, as with the rotary switches, took several work parties


When we went to fit the first of the three main field divert contactors, it wouldn't fit through the front of the cubicle frame however we tried to manoeuvre it. In the end I had to take off the small metal block where the air pipes are connected and re-attach it after fitting the contactor. I then had to repeat this for the other two.


Attaching the auxiliary control wiring to the front of these contactors was relatively easy. However, when it came time to install the 12 large cables on the rear of these boards, it was a different matter. We had purchased these cables from Paul Spracklen and they had lain in storage for some time. As we were fitting them in the middle of winter, not only were they stiff from the cold, they had become accustomed to their prone positions and were very difficult to get into place. In the end it took both Ian Kemp and Chris Thorn to help me get them installed, and again took multiple work parties.


Fitting the traction motor contactors was equally difficult as they are large and heavy. In one case, I had to drill out the mounting holes in the cubicle frame to a larger size, as they didn't line up with the mounting holes on the contactor itself! These six contactors have large 'Faraday-cage' type arc chutes, of which we initially had none. We did subsequently manage to obtain several, and a large box of parts from which Steve Tripp and I were able to make several more. Putting them together was somewhat difficult, as you need multiple hands, and one slip and it all falls apart and you have to start all over again. Wiring the auxiliaries on these contactors requires you to lie down in front of them as they are located very low down in the cubicle frame, almost at floor level, as trying to do it by kneeling and reaching down almost cripples you.


On the board that houses the fuses and circuit breakers, the rotary Motor Control Switch was missing. This enables pairs of traction motors to be switched out in the event of a motor failure. We obtained one as part of the haul from Howe, but some of the contacts at the rear were found to be broken, so it was wrapped up and laid aside. A couple years later during a discussion with Steve Tripp, he decided to see if there was any way the broken contacts could be repaired. As we had just been fitting motor contactors, he realised what I hadn't; that the contact blocks were the same kind as the motor contactors used. We were therefore able to take parts from a spare contact block and repair the switch, which was subsequently fitted and wired. On the fuseboard itself, all the fuses were missing, but all the MCB's were present. We have since obtained all the fuses that we need for Repulse, and have a few spares. Re-connecting the cables on the back of the fuseboard was not particularly difficult, as that is one of the few areas where there is plenty of space.

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The two large main starting contactors were obtained as part of the Howe equipment, and they were relatively easy to fit and wire. However, we have no spares or any for future use in Renown. These differ from the other contactors in the cubicle in that they have much bigger coils than any of the others and have connections for the large power cables from the batteries.


Of the boards that go in the Thin Man's passage, one is very heavy, having seven contactors on it, and it took both Mark and I to fit it. Once fitted, the contactors are very close to each other, and wiring them was very fiddly as access is very limited. The other four were relatively easy to fit and wire. The board that fits behind the fuseboard was somewhat difficult to connect up, as it's difficult to connect the cables when the board is actually bolted in place. Mark had to hold the board at an angle in front of its position, while I reached over to connect the cables, then it could be mounted on the bolts and fixed in place.  On the board that houses the field divert relay, there is a long green resistor mounted above it. We didn't have one, but the 50021 Loco Association kindly gave me one of their spares. However, this turned out to be open circuit, and I was not able to source one from anywhere else. We did have various other similar resistors we had got from 37s at Booths, so my father suggested I make what is known as a 'ladder network' of smaller ones that come to the same total value. I did this and mounted it on a board in the redundant space next to the start contactors.

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A couple of years ago we were fortunate in obtaining a spare electrical cubicle from the 50021 group, which had some equipment and much of the larger exhauster and compressor cabling still in it. It has all been removed and stored for possible future use in Renown.  We also obtained a genuine 50 reverser from the owner of Howe, but by that time we had temporarily fitted an ex-37 example, so I could get the six large cables from the divert contactors, three from motor contactors 1, 2 and 3, one from the field divert relay and one from one of the start contactors, into their proper positions. While the main cam mechanism is identical, the auxiliary contacts are completely different on a 37, and were incompatible. Chris Thorn offered to make a second set of auxiliary contacts, copied from the original, for future use in Renown, so we left the 37 reverser in Repulse until he had done this. As a result, the 'proper' one was only fitted into Repulse and connected up in 2014. However, these reversers are large and very heavy, and it took four of us to remove the 37 one and fit the proper one. We have two spare reversers in total, one of which now has the duplicate set of correct aux contacts Chris made.

I am at present re-installing the plastic control air pipes between various equipment in the cubicle. As soon as I started it became very clear I should have done it before much of the wiring was installed, as I'm now having to work in very restricted spaces around and in-between bunches of cables, and trying to get spanners in is extremely difficult.  I have also set about identifying the remaining severed cables under the floor around the electrical cubicle and generator room of 50030.  The second part of this article will describe our work in sourcing the electronic control units used in a Class 50, as well as the remaining work required to complete 50030 in electrical terms.

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Cab restoration and electricals update

Cab restoration and electricals update

Recent work in the cabs of 50030 has been concentrating on freeing off the power controllers.  Ian Kemp and Dave Rolfe have sprayed them liberally with WD40 and worked them backwards and forwards.  As a result they move for the first time since 1992, albeit rather stiffly in the case of no 2 end controller at the moment.  Andy Rowlands fitted, tightened up and reconnected the cables on the replacement set of contacts Dave had removed from one of our spare power controllers, to replace the set found to be broken during our freeing-off of the controllers. To achieve this you need to unbolt the plate that holds the sets of contacts so it swings away from the cams, and refitting the bolts that hold the plate is difficult as the contact springs keep pushing the plate away from the cams, which makes it not the easiest job when hunched up under the driver's desk and you need three hands!

The controller in no 2 cab is still quite stiff despite repeated applications of various lubricants, but the one in no 1 cab is much easier to move. If we cannot make them easier to rotate, we may have to look at removing the entire controller pedestals and dis-assembling them totally to see if the nylon bearings need replacing.




Ian and Peter Carter oiled the main big end bearings and barred the engine round.  Andy Rowlands has also been working to refit the reverser air piston in the electrical cubicle of 50030.


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Work party report 5th October 2014

Work party report 5th October 2014

Ian, Pete and Dave spent the day unfastening the bolts to allow the main generator fan to be removed.  The fan is between the generator and power unit (but bolted to the main generator itself) and is normally hidden by the surrounding cowling. It sucks in cold air from under the body to help cool the gen and the cowling keeps the air circulating round the gen rather than blowing it all round the engine compartment. It has to come out to give access to the next layer of bolts that actually connect the engine to the generator. This proved to be a very fiddly task in the limited space between the fan and engine block.  Ian is seen proudly displaying his dirty hands after the day's work!

I continued cutting and fitting the cubicle air circuit, with the same difficulties as before, today was the turn of the field divert contactors. The pipe itself is easy to bend and the olives go on fine, it's getting my hands and a spanner to the connections round all the cables that's the problem. I should have done these pipes first before cabling, but as ever, wise after the event.
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Work party report 21st September 2014

Work party report 21st September 2014
Dave, Pete and Ian disconnected and removed the four sections of airshaft round the power unit flywheel and bolted up the second intercooler, which Dave then painted. I continued cutting and fitting cubicle air pipes, removed the Z23 resistor and a now-redundant cable from it to the CU6, in preparation for fitting an electronic device in its place as part of the CU6 upgrade.
As we were packing up we were greeted by the sound of eight Rolls Royce Merlins as both the preserved airworthy Lancasters flew over Rowsley.
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Work party reports 29th June and 14th July

Work party reports 29th June and 14th July

On 29th June a long-running sub-project within the electrical restoration of 50030 took a substantial step forward. I got the proper reverser (Class 50 specification) fitted into Repulse, with help from Dave Rolfe, Peter Carter and Ian Kemp as it's so damned heavy. We had to jiggle it about to get it to fit properly, but did it in the end. I attached the divert cables at the rear, but didn't have time to do the auxilaries at the front as I showed two visitors round Repulse. We are always happy to show enthusiasts around our project so if you want to take a look inside our locomotives then get in touch with us either via the website or our Facebook pages and we will do our best to accommodate you.



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Also on this date Dave, Ian and Pete also continued sorting fuel and water pipework recovered from 50030's power unit to replace damaged sections on the ex-50008 unit.  This unit is destined for use in 50030 when complete - the existing power unit in Repulse was in acceptable condition when we acquired the loco, but has high engine hours and as part of our policy of overhauling our 50s to a very high standard in order to give them a long and trouble-free career in preservation we decided to overhaul one power unit totally.  The existing unit in Repulse will be re-used inside 50029 because the engine in Renown has serious problems following the seizure which ended the loco's BR career.  We don't know for sure but are aware of the possibility that the unit in 50029 may only be usable as a source of spares.  Power unit work can be one of the most gruelling of the practical restoration projects as the same task often has to be done at least sixteen times, sometimes even 32 or 64 times!


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On 14th July I attached the reverser auxiliary contact wiring after showing another visitor round Repulse. Meanwhile, Ian, Pete and Dave fitted the fuel feed and return pipes to the ex-50008 power unit that they had previously salvaged from the power unit inside Repulse.


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Work party report 15th Jun

Work party report 15th Jun

As it rained almost all day yesterday, even though the forecast was for dry weather, I decided not to cart the reverser outside as I've cleaned it, so I test fitted the newly-made CU2 field divert and CU7 ETH detector units into 50030's elec cubicle. While the CU7 can go in its original position, the original position for the CU2 had the cable connections very close to the cubicle frame, so I drilled a couple more holes to put it in a better position.
Inbetween the heavier bursts of rain, Ian and Pete removed the fuel feed pipes from 008's power unit as they'd been bent during the lift at Crewe when we bought and moved the PU about 8 years ago. Dave was painting pipes taken from the PU inside Repulse to replace them.
I also took the opportunity to get some more pictures of Mark's work last weekend on the generator conduits.

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CU5 replacement under construction

CU5 replacement under construction

One of the electronic control units in a Class 50 locomotive is the CU5 radiator fan control unit.  It works together with the CU4 coolant flow control unit under the control of the CU1 main control unit to maintain the correct cooling water temperature by adjusting the speed of the radiator fan.  Both RRRG's locomotives are missing this unit.  The original was designed by Hawker-Siddeley for English Electric and utilises components that, by the standards of the 21st century, are thoroughly obsolete.

A good friend of RRRG, based at the Gloucestershire and Warwickshire Railway, offered his services to construct a compatible replacement unit using modern electronics - needless to say, we were and are extremely grateful for this offer!  Shown here is the item which is now nearly complete.  The main circuit board has been deliberately left unattached to the case at this stage, as the next step is to test the unit by connecting to a suitable 110 volts DC source in order to ensure it performs correctly.

An original unit was borrowed from the 50021 Loco Association, and this new unit has been produced to resemble it physically, while using greatly-simplified circuits (as the original was over-complex for what it needed to do), modern components and utilising a small programmable microprocessor to replicate many of the functions of the original.  We will provide more updates on this sub-project when they become available.


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Rebuilt CU2s are delivered!

Rebuilt CU2s are delivered!

Following on from news and developments earlier this year on the work we have commissioned to build two CU2 field divert units for use in 50029 and 50030, we can report with great pleasure that this project reached a successful conclusion today.  Our contractors invited 50030 Electrical Officer Andy Rowlands to view the rebuilt units, and demonstrated as the relay in each unit was energised and gave output to the correct terminals.  Each unit was tested multiple times with no problems arising.  We were pleased to note that our contractors have managed to replicate the original solder tracks from the sample unit supplied as the template.  Now that we have taken delivery, the units can be taken on site for trial fitting and cabling up, before being stored securely off site until such time as they are needed.  Photos courtesy of Mark Brown at IES.  This work has not been cheap and we would greatly appreciate the support of Class 50 enthusiasts either by joining RRRG and buying shares or supporting us via our online shop.

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Radiator louvre slats and mechanism finished, donor electrical cubicle wiring loom progress

Radiator louvre slats and mechanism finished, donor electrical cubicle wiring loom progress

Work on site over the weekend of 13-14 June comprised efforts by Dave Rolfe to finish off the last set of radiator grille louvre frames and slats.  These have now been sanded and painted ready to reinstall into 50030 and will mean the locomotive has a fully overhauled set of radiator slats, together with the mechanisms for actuating and moving the temperature-dependent sets fully overhauled and operational for the first time in many a year!

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Also on site were electrical officers Andy Rowlands and Steve Tripp, together with Sarah McCall the membership secretary.  They carried on with the donor electrical cubicle. Following recent progress with removing the control units, attention turned to the wiring loom which we also intend to salvage in order to replace the damaged wiring in 50029.  Initially the complexity of the loom and its many tentacles proved frustrating but Steve and Andy have devised methods for transferring it into Renown. All the cabling in all the side sections of the cubicle, namely that for KV10s, relays and control units, has been pulled out of the frame or into the middle section where it is more accessible.  One more visit should have the whole wiring loom out and hopefully soon into its new home in 50029.  We can then consider our options for the bulky frame of the donor cubicle which is taking up valuable space on site.

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Rebuilt ETH KV10 completed

Rebuilt ETH KV10 completed


We are pleased to announce that the first of our rebuilt KV10 electronic units has been completed.  As we reported in April, we placed an order for four rebuilt KV10 units, two per locomotive using modern electronic components as opposed to the obsolete 1960s versions of the original.  This picture shows a rebuilt CU6 ETH KV10; we have ordered two of these plus two rebuilt CU3 main generator units (the originals are identical to each other and are transformed into CU3 main generator or CU6 ETH generator KV10s by addition of a CU3A or CU6A daughter card but the rebuilt versions incorporate the electronics of the daughter cards into the main unit and so differ from each other).  The two photos above show both sides of the rebuilt unit's circuitry.  By way of a comparison, below is a view of the original 1960s vintage circuitry in the KV10.


The completion of the first rebuilt KV10 marks a further important stage in the restoration of 50029 Renown and 50030 Repulse.  The cost is just over £1000 per unit and we need the help of the enthusiast community to help us fund future stages in the restoration project.  Can you buy something from our online shop or consider joining RRRG and buying shares to become part of this exciting locomotive rebuild project?  We are keenly aware of the anticipation in the enthusiast community for 50029 and 50030 to haul trains once again but we are going to need your help to achieve this.

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Order placed for rebuilt KV10s and CU1 testing

Renown Repulse Restoration Group has placed an order with a noted locomotive electronics expert for testing of a CU1 main control units and the rebuild of KV10 load regulators using modern components.  The CU1 acts as the "central brain" of a Class 50, receiving and sending signals from and to all the other electronic control units in the locomotive.  There are two KV10 load regulators in a Class 50, one is denoted CU3 and controls the main generator output.  The other is denoted CU6 and controls the ETH generator.  A KV10 is transformed into a CU3 or a CU6 by means of pairing with a control card CU3A or CU6A.

As with many electronic components of the Class 50, the KV10 design is full of obsolete components and with an eye to the future we feel this work is essential to our goal of "future proofing" 50029 and 50030 and ensuring them a long and secure future in preservation.  The original design suffers from a tendency to "lock on", whereby faulty circuitry causes the CU3 to lock in the full position even if the power controller is at its minimum position.  The only real solution is to repair the faulty circuitry but that repair knowledge gets ever more scarce with the passing of time.  As a result, we feel that the decision to purchase four rebuilt units (one main and one ETH generator control unit for each of 50029 and 50030) is money well spent.

There are actually two sub-types of KV10, denoted B1 and B2 with slight differences in component types.  RRRG has over twice as many B1s as we do B2s but our stock of CU3A and CU6A cards are only confirmed to work with B2 type KV10s.  The rebuild process uses only the case, heat sink and thyristor from the original KV10 and as a result the control cards become obsolete as the components they contain are now integrated into the main unit.  We intend to supply type B1 KV10s for the rebuild project with a decision on disposal of the type B2 units and control cards to be taken at a later date.

The following two shots show a rebuilt CU6-type KV10 installed in 50008 Thunderer.  The first shot is taken from the Thin Man's side and the second is opposite the exhauster.  Click on either to enlarge (opens in new window).

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Needless to say, this work will not be cheap and we really need the support of the preservation community.  Perhaps you could donate to our project, or become a member of RRRG and buy shares, or browse our online shop for items of interest?  Your support is what has got us this far already and it is much appreciated.

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CU2 rebuild update

As long-term followers of RRRG will know, for some time now we have been investigating the remanufacture of CU2 field divert units to replace the ones missing from our locomotives.  Our contractors for the job, Industrial Electronic Services Ltd, had analysed a genuine CU2 kindly loaned to us by another Class 50 owner and were confident they could reproduce the circuitry and components in the unit, using modern equivalents where possible/necessary.  They had however hit quite a snag when it came to replacing the little relay in the original unit.  The CU2 is a really amazingly compact piece of equipment for mid-1960s electronics as seen in the photo of the loaned unit below.  The relay in question is the small black box seen in the centre of the picture.  It switches at the operating voltage of Class 50 auxiliaries, namely 110v DC which brings about the problem of how to find a modern equivalent.  Electronics is obviously one area where technology has progressed leaps and bounds in the near-half century since the Class 50 was constructed by English Electric and relays to operate at such high DC voltage, let alone such compact ones (it appears the original was custom-made for EE by ITT) are almost completely obsolete these days.  Most modern relays, even of a size too big to fit the case, would burn out very quickly if asked to switch 110v DC.



We thought about various ways to overcome the problem.  Inverting the current to AC, using an AC relay and then rectifying it back to DC was suggested but dismissed as impractical.  50030 Electrical Officer Andy Rowlands suggested using a spare NR28 relay, as used elsewhere in the locomotive to switch 110v DC.  It wouldn't fit in the box for the CU2 (and the CU2 is deliberately designed to be compact as it fits into a very tight space in the cubicle) but Andy reasoned it could be mounted externally and wired in.  We supplied IES with a couple of NR28s to test the theory and they agreed it would work but felt the new divert unit would need some circuit modification if it were to be used.  IES decided to have another look at the relay market and managed to source a relay from the US which has a 24v coil and can switch up to 220v DC.  IES ordered a number of these relays on our behalf and have now advised us that they have arrived and appear to work fine in our 110v DC application.

We now expect progress to be rapid on the rebuild of these electronic units.  IES have invited Andy to inspect the new relays in person the first week in March and if approved by us, IES expect to finalise the design within the next couple of weeks with production of the two units requested following imminently thereafter.

A full description of the electronic units in a Class 50, and how many of each type RRRG has, can be found in RRRG newsletter Issue 23 (Autumn 2011).  Since that article was written, we have acquired one original CU2 from another Class 50 owning group however we still intend to have two units built by IES to cover for possible future failures.

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Recovering parts acquired from Rodney Group

A large amount of heavy boulders blocking the path to the container where our purchased spares were.

On Friday 29th June 2012, Sarah and myself set off together with our trusty hound Toby to meet up with the contacted transport company at a site near Worcester to collect electrical items we had purchased from 50021 Rodney Group, this also included a Radiator Fan Motor and Traction Motor Blower for the D400 Fund.

When we arrived at site, we introduced ourselves to the Lorry Driver Nigel Chapman. The first problem we encountered was that due to the heavy deluge the day before, a delivery of large boulders had been delivered and dumped in front of the grounded curtain-sided truck body that our items were being stored in.

After a little head scratching it was decided we could get into the other side of the body if we removed the site security fencing. When we obtained access to the other side of body, the next obstacle was to release the tensioning mechanism, which through the passage of time had sunk into the ground, and after some digging with spades and persuasion with the site dumper truck which lifted the sunk body out of the ground we gained access.

We moved some fencing to gain access to the other side of the container.

With the transport lorry manoeuvred into position and stabiliser legs down the next problem encountered was a temperamental hydraulic hi-ab which with the technical know-how of Nigel, eventually played ball. The first two items strapped up and lifted out were the Cubicle and Rad Fan Motor. The two compressors and traction motor followed soon after. The items were secured down and we then drove to where the traction motor blowers and spare power unit (ex-50045) were stored. One blower motor was lifted and secured down.

We needed the site dumper truck to force our way in...

RRRG's main purchase, the electrical cubicle, safely loaded onto the lorry.

Once everything was checked to be secure we set off on our journey North, up the M5, M42 etc heading for Derbyshire with Bowers Electrical being our first port of call. We had anticipated the journey to be difficult with the usual Friday afternoon traffic, however also had the added problem of road closures along the A6 between Derby and Rowsley due to the Olympic Torch relay, fortunately the journey went without delay or incident. At Bowers we had the assistance of a forklift and very quickly off-loaded D400 Fund's Rad Fan Motor and Blower Motor together with our two compressors.

RRRG's haul included two genuine Class 50 compressors, ex-50011, seen being guided onto the lorry.

We then set off for Rowsley, arriving at site about 4:45pm, where we were met by local “BG” resident Dave Rolfe. Once on site we discovered one of our ETH generators (in worse condition than the others, which is why it was never sent for overhaul) was obstructing the route of the lorry to our storage shed, incidentally we also needed this moving, so with the Hi-ab on site we took advantage and relocated it dropping it near Renown together with the Traction Motor.

A further spare traction motor was also included in the deal.

A short break was had whilst we retired to the BG for a brew. Once refreshed we returned to our storage shed to off-load the electrical cubicle although this was not without problems as the hi-ab could not manoeuvre the cubicle all the way into the shed so with a solid steel bar and some brute force we pushed the cubicle in. Space in the shed being what it was, we had to man-handle the cubicle in at an angle until the doors could be closed and locked.  Everything was then sheeted up, secured and we eventually left for site calling at Frankie & Bennies for a very well earned bite to eat and pint, eventually getting back home some 15 hours after starting out earlier that morning.

After some manhandling to make it fit the available space inside RRRG's designated facility, the newly-purchased cubicle was safely stored awaiting future work. With this final act, a long and satisfying day finally came to an end!

A big thank you to Nigel Chapman the jovial lorry driver, who was a tremendous help on the day, enjoy your retirement!!  Photos by Sarah McCall.

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Purchase from Rodney Group

RRRG has just purchased a traction motor, two compressors and an electrical cubicle (all ex-50011 Centurion) from the 50021 Rodney group/ owners . The items will be collected, together with items bought by the D400 fund, and transported to Bowers Electricals Ltd. at Heanor for assessment and any work that may be needed.

The  electrical cubicle that has quite a few re-usable components will be dropped off at Rowsley where the parts will be stripped for future use or spares.

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Another CU1

Back in 2002 when RRRG successfully bid and secured Renown and Repulse together with various spares David Phillips was a volunteer at Pontypool & Blaenavon Railway and safely stored a CU1 on our behalf. As Sarah & I were travelling down to Swanage diesel gala this weekend to enjoy recently restored 50026 it was decided to call in to David's home in Trowbridge to collect the CU1 en-route. Whilst there I received a bonus in the form of an Ammeter for one of the cabs. I would like to thank David for safely storing the parts and also for the hospitality he and his wife offered us.


CU1 collected from David Phillips CU1 Wiring Loom and Plugs Cab Ammeter



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Work Party 28th April 2012

Sarah and I attended site and again met on site by Dave who I now think lives on site full-time as he is always there :-)

Dave continued with clearing and tidying the container a job that when he started thought would take a morning ended up taking three days. Once this was completed he continued with the refurbishment of the radiator grilles. The process takes such a long take as each element is being stripped back to bare metal, prior to priming and painting, and as BR's policy appears to have been apply new paint onto the old there are numerous layers of paint and a rainbow of colours.

Sarah & I continued with the  assessments of the KV10's. Starting with the best we are checking and cleaning contacts and replacing unserviceable parts. We have finished one complete unit having to re-terminate a couple of broken cables connections and replace a couple of components. The next best KV10 selected had sound looking components but the cable terminations at the top of the unit looked a little rusted and three of them sheared off when attempts were made to loosen them even after liberal application of WD40 (other lubricants are available lol). Therefore we had to loosen of the paxolin board from the body of the KV10 and using recovered termination studs from other scraped units these were replaced but this is not easy as unless you disconnect cables going from one side of the unit to the other side the board only gives finger width space.

Our next visit to site to continue with work on the KV10's will be in a few weeks as we will be participating in a railtour with EE Type1's and a couple of galas where it's hoped to sample a certain Mr Spracklen's 50026.

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