We left you last time having moved from our accommodation at Neville Hill depot in Leeds to the Great Central Railway (North) at Ruddington. We’d left Neville Hill with a vast amount of work complete but without any way for 41001 to usefully turn Valenta power into useful electrical energy due to the fact that we had “the wrong alternator” – which will now be for ever more called “Grommet” for what I hope are obvious reasons!
Shortly after arriving at Ruddington, Gary, Tony and myself managed to get an audience with Dave Moore, BRUSH Traction design supremo who’s had a hand in the electrical side of things ever since the Class 60’s. We had an excellent 3 ½ hours with him discussing our various options, using the power sled for the Autocar project he is working on (www.electricautocar.co.uk and well worth a look) to illustrate the various issues of power regulation and control.
There were basically two options we had; a) we adopt the system that was used on the refurbished Class 37’s, which in itself is very similar to that used on the late Class 47 ETH conversions (ACR2), or b) we use the Class 57 traction control system plus an Automatic Voltage Regulator (AVR) for the aux and ETH. The Class 37 system is electrically very simple and one could probably obtain the various modules from scrap yards, although knowing how they operate these days they wouldn’t come cheap. The thorn in the Class 37 system is that it relies on a vane motor to regulate load power. Vane motors are quite different to LVDT regulation which is what a Valenta has and we’d have to get our governor modified to make it compatible with the Class 37 system. All 3 of us immediately had alarm bells going in our heads as if there is one bit on a Valenta that goes wrong occasionally it’s the governor, so having something non-standard was going to be very awkward.
We then came onto the subject of the Class 57 traction control system. Dave commented that it fitted our purposes 100% with just the addition of an engine speed probe required. We stopped him after about 5 minutes into this discussion and went “hang on….where the hell do we get a Class 57 rack and cards from??” being the bright spark I am noting that they are all still working and may miss the control system. Dave then walked over to his car and came out clutching his phone; he then handed the phone to Gary with a picture of a rack sitting on a concrete floor. It was a Class 57 rack plus associated cards which were sitting at BRUSH and had been a spare system built when they did the conversions but as the system is so reliable have never needed to call on it.
The Class 57 system is leagues ahead of what went before and is the basis for what the non FGW HST power cars now have fitted. All nice and straight forward analogue electronics, all readily available and all tried and tested technology. The AVR would be something we would have to procure separately along with the aux and ETH rectifiers. We thought this was the best way to go and Dave was very confident in our abilities in integrating the system into 41001. But there was a hurdle to jump over; we had to obtain permission from “On high” at Wabtec to acquire the rack and cards. Fortunately this is where 125 Group has real connections as Alex happens to know Chris Weatherall, MD of Wabtec UK, very well. So a meeting was arranged between Alex and Chris at Ruddington so we could show him what we had been doing – Chris was extremely impressed with the work on 41001 and as the two headed to the pub, Chris opened his car boot in which was a large box with a Class 57 rack and cards in. They were only too happy to help.
So now we had the pieces of the puzzle but we had a way to go before the jigsaw would be complete. We now had all the Class 57 schematics so we could work out what was what in the rack as there was some repair work to do on the alternator power module – it was the original prototype – and we were missing an input board. But before any of that we needed to get the auxiliary supply working from the alternator.
As I described last time, 41001 has a dual wound aux/train supply alternator. That means there is one exciter which drives both alternators, but we only regulate the aux side; the ETS will “move about” but that really doesn’t matter when you have a load of heaters connected across the output. But how does one regulate the output? On the old HST electronics you’d use a TDAVR which uses a thyristor to regulate the output. That’s all a bit “old school” these days and a like a sledge hammer opening a nut. But prior to the HST, the aux systems on locos used to be handled by a Newton Pile AVR, which is an antiquated electromechanical system where a mechanism crushes a pile of carbon to regulate the output. Fortunately there is a modern way of doing this with MOSFET transistors. BRUSH have a design that has evolved through the years, originally called the FK2 after its designer (F Kevin Thompson) and which is still in production using IGBT devices today. We couldn’t ask BRUSH for one of them as they are NOT cheap and they also don’t have them lying about. We could try the scrap market but that has its own issues as they are “sold as seen” and there would be considerable work trying to get it working – it being bad enough that we had an alternator that hadn’t worked for 30+ years, the last thing we want is two things that were unknown.
So we bit the bullet and contacted Noel Craigen to ask him to build us a new FK2 style AVR. Noel is ex Tinsley RfD Tech Office and originally designed the AVR to get rid of the aging Carbon Pile AVR’s that were causing more failures on the 47’s than anything else. After leaving RfD he has continued making AVR’s, updating the design as he goes, and they have been used by preservationist & the industry alike. When we ordered it we were 4th in a queue, showing its popularity and after Noel fitted one to another dual wound alternator loco – his first, so he wanted to check it worked ok before shipping ours. So at the beginning of November a shiny new AVR arrived.
In principle the AVR is simple, but as ever the execution isn’t quite that easy! It has only 5 electrical terminals; a “loop” which has the charging feed to the battery connected (in and out); +110V from the rectifier (output of the aux alternator effectively); the aux exciter field connection; and 0V. That’s it. What the AVR does in simple terms is to charge the batteries and ensure that the charge rate is kept within a specific envelope for lead acid batteries. The looping connection to the batteries is so it can monitor the current to and voltage on the batteries. It controls the power using the exciter output – more excitation equals more output. The added bonus with this type of AVR is that you can hook very high powered kit, like a compressor, straight over the output of the rectifier (NOT the batteries, which are isolated by a diode) & when the motor of the machine turns on the AVR will see a drop in volts and current to the battery & adjust back to where it should be – it auto compensates. But you’ll notice part of the puzzle is missing to get this up and running – a rectifier.
Speaking to Dave he recommended something like the Class 47 ACR2 rectifier which is very manly and the basic design would be suitable for aux and the ETH. For the time being we only needed to do the aux design as the ETH could wait until we had the power car moving under its own power again. Fortunately for us Dave had saved a box load of HST main rectifier diodes from the re-power on East Coast and kindly donated 12 diodes to us, 6 for each rectifier. We then set about obtaining an enclosure, heatsinks, copper bar, insulating material, resistors and capacitors and had the whole lot delivered to Tony who then put on “The A Team” music and started construction across a 9 day period. What we have ended up with is a thing of beauty and very much “belt and braces” both electrically and mechanically – it weighs in excess of 60kg. The function of the rectifier is actually very simple; to take the 3 phase alternating current (ac) out of the alternator and turn it into direct current (dc) suitable for the batteries and dc machinery. The 3 phase bridge rectifier consists of 6 diodes, each leg of a phase having two diodes; one pointing to positive the other pointing away from negative. Each diode has a capacitor across it for efficient operation. There are 4 resistors plus a brace of capacitors across the output to ensure stability and finally a dummy load resistor to give the alternator something to chew on in case the load suddenly disappears. The heatsinks are live as is common on railway electrics.
Fitting the AVR and rectifier was carried out over two working sessions, one in November and one at the end of December. The AVR really needed to go close to the cubicle as that is where all the wiring associated with the auxiliaries are. By luck, or was it serendipity, the AVR fits perfectly on top of the cubicle next to the short circuiter box – the short circuiter cover needed moving over about 30mm to give the AVR enough room to sit flush with the outside of the cubicle metalwork. Once Stuart and Mike had mounted the AVR in position, I then set about modifying the cubicle to take the AVR. Gary and Tony had already made a start on this back in October and stripped out most of the 3 phase wiring we would no longer need. To aid wiring we had already started drawing up the power car electrics on a CAD system so we had a permanent record of how the “new” 41001 was wired and could modify as required as we went along. We had specifically re-worked the way the AVR would interconnect into the power car such that it would require only minimal modification from what we had already done; it is subtly different from a Class 57 installation but electrically identical.
Christmas at Ruddington
We had a longer working party at the end of December between Christmas and New Year in an attempt to install the now completed rectifier and finalise the auxiliary system before testing it. The rectifier box is both heavy and a rather awkward shape so physically getting it into the power car was a challenge; Gary and I commandeered some platform steps at Ruddington so we could walk the rectifier enclosure up to the power car cab door and then in through it. We decided we would wait until the following day to get it into the clean air compartment as both Alex and Stu would be attending along with Gary, James and I – more muscles would be better for this job. But before the rectifier could go on top of the alternator we had to make a platform for it to sit on. We had thought long and hard about the problem and it was Stu that eventually came up with the simple solution of two sheets of ¾” plywood. Metalwork would be too heavy and cumbersome and using something like Tufnol would be expensive. I managed to get the plywood for free from my brother in law and as we all agreed, if the plywood ever caught fire the fact it was on fire wasn’t you primary concern at that point! (i.e. the thing that made it catch fire might be more of a concern!) We used two sheets of plywood so that the first was bolted securely to the alternator and then the second provided a level surface for the box to be bolted to.
The following day we humped the rectifier through the clean air compartment and then up onto the top of the rectifier. It was a perfect fit and certainly looked the part, with cabling entering/exiting on A side and cooling air being blown B side to A side by 3 powerful fans. For Christmas I had requested some useful tools – a very large crimping tool and also a cable cutter that could go through insanely large cables. This made light work as we would have to re-work all the cabling to now suit the aux alternator. I then liberated one of the 3 cables between alternator and cubicle – we’d only need 2 now – so that could be used for the 3 short runs between the alternator and rectifier. The new cable cutter made light work of chopping the cable to the correct lengths using the new crimping tool to make off the massive 185mm crimps suitable for connecting to the alternator and rectifier. We had also obtained some large M40 cable glands to provide strain relief into the rectifier – Stu went for a trip to the workshop to drill and cut the holes and then fitted the glands which worked a treat and look very smart. One problem we did have with installing this large cabling was trying to get it to bend to where it had to go. Tony had put some copper bars for us to take power off the heatsinks but we couldn’t get the cable into the right place to use it – so time for a plan B where Stu and I hacked off the corner of each heatsink so that the crimp could bolt straight to the aluminium whilst not fouling the lid. That worked well but will require tidying next visit as it needs some work with some power tools I have at home plus some smaller heatshrink.
We then turned our attention to the bottom of the cubicle and I started to re-arrange the cabling so we could get the two large cables from the rectifier installed. We already had a copper bus-bar from 41001’s previous life but needed another, so I commandeered one of Tony’s now redundant bus-bars from the rectifier plus a couple of bits of plywood and fashioned another isolated bus-bar for the main positive connection. After some swearing we eventually managed to get the large cables hooked up before finishing off and then checking all the connections.
Time to Test
We were then in a position to test the aux supply system and there is only one way to do that – start the Valenta up! The weather was cold but not freezing so we did our usual pre-flight checks, including changing the injector on cylinder B1 which had been making noises suggesting over/under fuelling since day one. To start with we would pull the fuse out on the AVR as we didn’t want to have problems with that showing up whilst battling a cold Valenta at the same time. The Valenta started firing on two cylinders with a lot of chugging and banging going on. After a while I ventured into the engine room and tried feathering the fuel rack which actually made the engine speed increase. After about 30 seconds of fuel rack jiggling the engine then raced up to 750rpm and settled down. I then selected Notch 2 to try and clear the exhaust out and we let the engine start to warm up a bit. After 20 minutes we shut the engine down and put the AVR fuse back in.
I started the engine again with Gary watching the battery charge meter and AVR volt meter. After a few seconds once the engine started the volts ramped up to around 113V and the battery charge meter showed around 100A being stuffed into the cells. It worked!! After around a minute the charge dropped to around 20-30 amps and the voltage was holding stable at 112-113V – lots of hard work coming to a perfect conclusion.
After shutting the engine down after around 20 minutes I checked the heatsinks and they were stone cold – only the dummy load resistor was hot as it is supposed to.
We can hear you knocking
We then had one mechanical problem to sort before leaving – the injector change had made matters worse as that cylinder wasn’t even firing now. I first did a compression test on B1 which showed a good 300psi – much better than the original 200psi on July 1st, showing that the engine was now in better health with regular run ups. It didn’t seem the injector was at fault, either so all eyes focused onto the fuel pump which appeared to be very weak. John Zab and Gary had a trip to our storage facility to pick up a spare pump whilst James and myself “argued” with the pump to release it from the engine. After a little persuasion the pump came off and then set about fitting the replacement pump and original injector.
We then started the Valenta again and things sounded a lot better – at least the cylinder was firing again. There was still a slight over-fuel knock, so we shut down the engine again and I tweaked the rack slightly to back off the pump. Re starting the Valenta and all was sweet – the best it had sounded since we installed the engine. Running was smooth without any knocking sounds. We may be over critical with the engine but it pays to be so in preservation as we don’t have the luxury of main line operations with massive budgets.
So there you go; the power car is now self-sufficient at supplying power both from the engine and to the batteries – the circle is complete. Next is the more complex and daunting prospect of making 41001 move on its own. That will almost certainly take more than the next update to resolve but as ever we will be working diligently to work towards this target.
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