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Aster's Bulleid Light Pacific / "Spam Can"


Aster's 30th Anniversary Model


Southern Railway - British Railway / Battle of Britain class 4-6-2


an assembly review and photos by Robert Youngjohns


Aster's BR 34051 "Winston Churchill" and the SR 21C166 "Spitfire" utilize the same mechanism. The difference is in the paint scheme and tender detail.  The Southern Railway version in Malachite Green - 21C166 "Spitfire" -  has a high sided tender.  While the British Railway livery - 34051 "Winston Churchill" - has a cut down tender representing the locomotive as preserved at the National Railway Museum, York.   I selected the British Railway - "Winston Churchill" - Bulleid Light Pacific KIT to assemble.


Start by reading the instructions! Easy to say but difficult to do for someone whose instinct in life is to act first and ask questions later - but in this case an obvious pre-requisite to building the complex and very beautiful model of the Oliver Bullied classic steam engine that Aster have produced to celebrate 30 years.


A study of the drawings quickly reveals that the valve gear will be the most difficult part of the assembly and will require considerable patience if they are to work reliably. Other than that, things seem to follow the pattern of other Aster kits and didn't seem to offer any  particular problems.


Lapping the surfaces of the steam chest and the slide valves is very therapeutic and I was pleased with the finish I was able to get with 2000 grade paper. The pistons are shipped inside the cylinders and I assumed are matched so I took the precaution of marking them to ensure they stayed together as the assembly progressed.



The frame goes together quickly and both inner and center cylinders are easy to fit. Don't forget the blanking screw on the center cylinder – I did and fitting it later was very difficult!



Close-ups of the front frame from underneath and from the side show the fitting of the push rods for the outer cylinder valves. These run in a slot between the cylinder and the frame and it took some fiddling to ensure that they moved freely. I added a small smear of lithium grease to help matters along.....




The valve gear was every bit as difficult as I had expected! The drawings are hard to follow and have some obvious mistakes. Assembling the expansion links and connecting the radius rods is just plain fiddly and  the side pieces of the expansion link need to be smoothed carefully if the die block is to run freely. The reversing rod and the lifting link had me gently cursing under my breath but eventually lined up and moved freely and evenly. The eccentric straps are neatly color coded to ensure that the right pieces stay together but, even so, they need to be installed the right way round if the bearings driving the return cranks are to fit properly.


The finished article should look a bit like this.....



Next the valve gear is fitted inside the frame. At this point it becomes very clear that that once fitted, it will be almost impossible to make adjustments or tighten loose fittings later so it is worth going through every part and using a judicious drop of Loctite 222 to ensure that everything stays put!


The main driving wheels are fitted next and the eccentric straps carefully fitted using a PTFE strip as a bearing surface. With the valve gear in place and the inner piston rod fitted, it starts to look like the real thing!



The nice thing about the valve gear is that the timing is essentially 'hard wired' from the driving wheels. The only adjustment required is to ensure that the slide valves open evenly on each side as the valve gear moves. Once in place tighten the set screws with a drop of Loctite 222 and tighten down the steam chest covers.



 The remaining wheels and the connector rods come next. The drive for the water pump is curiously taken from the front wheels via a bent crank – it would have more elegant to drive it from the back wheel but I guess that to do this would have required a new pump design – essentially a mirror reflection of the pump used on earlier Aster models.


Some detailed views of the underside of the frame with everything in place. It's obvious how difficult this will be to adjust or repair later so once again a check that everything is tight and secure would be worthwhile!






The air test is next and, much my relief, went without a hitch. I doused the cylinders in machine oil and added oil to the airway before starting the test to ensure that everything stayed lubricated under the drying impact of the compressor. (Actually, I lie – the first air test revealed that I had forgotten to fit the blanking screw for the inner cylinder and this took some time to put right as the push rods for the side valves had to be removed first which, in turn, upset the alignment of the valves....)


Boiler assembly was straightforward. The only issue was that the pipe for the pressure gauge has to bend very sharply where it fits to the boiler and care needs to be taken to ensure that it doesn't kink. The smoke box needs the careful application of packing compound to give an airtight seal.



A quick second air test at this point by removing one of the safety valves allows a final leak check before carrying out the hydraulic test which I was able to do using the pump on the tender of another Aster model.


At this point assembly seemed to accelerate and after a couple of longish evenings, it was done! I found that the paint surface on the smoke deflectors was very poor but Aster USA shipped replacements very quickly.



The big test – what would she be like under steam........


A warm, sunny California afternoon seemed like as good a time as any to try her out. The burners lit quickly and she came up to pressure very quickly under the chimney fan. With the blower slightly open, pressure continued to rise and the first safety blew. I held down the first safety and the second blew a few seconds later.


Getting her to move took a little patience as it took a while to clear the cylinders and vent some of the excess water in the boiler – which I had over-filled as a result of an inconvenient air bubble in the sight glass. Once underway, she picked up quickly and became very sensitive to the regulator.



A few circuits with no load to settle things down, then I attached a short rake of BR 'Blood and Custard' coaches.



She pulled well – my track suffers from an unintentional slight gradient in a couple of places and it was good to hear her working hard with a very characteristic sound as she pulled away from standstill. On this first test, she ran for about 15 minutes before I had to add water, about 30 minutes before she was out of fuel. A very impressive first outing!


My general impressions so far are very good. She is clearly a powerful locomotive and the design has been well thought through. There are a number of small positive design changes compared to my previous Aster kit (“Duchess of Montrose”). The oil reservoir is easy to access at the front of the locomotive rather than under the blow-down valve in the cab; the controls for the blower and the axle pump are easier to use and the self contained smoke box creates a much better draft. Possible issues are that the water reservoir seems small for an engine of this size and that the sight glass is very difficult to see.


My biggest worry remains the valve gear! Did I really use Loctite on every fitting or will the terrible day come when I have to strip the engine right back to basics to tighten a wayward screw! Only time will tell but knowing my luck it will be not in the gentle anonymity of my yard, but at the next big steam up with a cast of thousands in attendance!




I've now run the "Sir Winston Churchill" a few times and the following are some tuning notes that might be useful.


The sight glass for the boiler water level is difficult to see and it is easy to over-fill the boiler as the axle pump seems very efficient. I've found that opening up the bypass valve for the water feed by about an 1/8th of a turn seems to keep the water level reasonably constant under moderate load.


Purists might like to skip what follows but a crude way to ensure you don't over-fill the boiler when using the hand pump on the tender is to leave the blower open with the regulator closed. The blower intake is located just above the 7/8ths water level on the sight glass and water will start to spurt out of the smoke stack if you leave the blower open and try to fill above this level.


The water reservoir in the tender is, as I suspected, rather small for a locomotive of this type and needs to be topped up fairly frequently. The alcohol reservoir seems to be good for about 25 minutes under moderate load. Being removable, it is easy to re-fill it without fear of causing a fire!


The draught is very good and the burners light quickly. The Aster suction pump doesn't fit very well - I added a couple of elastic bands around the base and that improved things immensely! I've trimmed the wicks back a bit from the height recommended by Aster to try and get a better balance between heat applied and steam used as the safety seemed to be blowing constantly even with a heavy load.


The blower is very sensitive and only needs to opened very slightly to maintain a draught when the engine is stationary. I've never needed to open the blower when the locomotive is pulling even with a heavy load.


It is important not to over-fill the lubricator otherwise the displacement process won't start and the cylinders could be deprived of proper lubrication. About 2/3rds full seems to be about right. (Thanks to Andrew Pullen for this tip!)


My only outstanding issue is to control wheel slip. Soft chalk and a clean track are a good starting point but I wonder whether the locomotive really needs to be a little heavier given the power it is capable of putting down onto the track.


All in all, Aster's Bulleid Light Pacific / "Spam Can" is my best Aster British locomotive yet. Powerful, well designed and easy to use.


Southern Steam Trains expresses our genuine gratitude to Robert Youngjohns for writing this comprehensive review  and providing photographs to illustrate the assembly process for posting on our website.   We are confident that this will be a supportive resource for all who are building an Aster Bulleid Light Pacific "Spam Can."




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