To most British steam locomotive enthusiasts the LMS Princes Coronation Pacifics represent the ultimate development of the pre nationalised railway in Britain. Developed under William Stanier’s leadership these locomotives were designed by his left hand man Robert Riddles assisted by Chief Locomotive Draftsman T F Coleman. The lessons learned from the earlier Princess Royal class were well learned and a magnificent design resulted. The first batch were all streamlined and were in direct competition with the LNER A4 class in the race to the North, a battle between the two companies for the business of getting passengers and freight to Scotland as quickly as possible. It wasn’t until 1938 that the first un-streamlined version arrived on the scene and it is on one of these that Aster have based their latest very beautiful British outline.
Anyone who has built an Aster kit will understand the excitement I felt when Ted Chatfield, South West Agent for Aster UK, contacted me a few months ago to announce the arrival of my new Duchess kit. A hastened to his house to collect it and we discussed its attributes over a completed example and a nice cup of coffee. At home I began unpacking the large carrying case and began the essential first step of completing an inventory check to ensure everything was in the boxes. The construction manual that comes with the kit has a large inventory at the front and it is an easy [if lengthy] task to check off everything in the boxes against it. I regard this as an essential.
The next task is to study the extensive drawing manual to get a general idea of the construction and the tools necessary to make a good job of fitting and assembly. Having examined this together with the construction manual, I would add to the list of tools suggested M2 and M5 X 0.5 taps and dies and a bottle of thread lock such as Loctite 243. The smaller tap will be needed to clean out paint from some of the many tapped holes in the various components and in my kit, to tap one of the valve crossheads that unusually had got through Aster’s quality control process. The M5 is the size used for the banjo bolts and also the safety valves and will be useful for making a pressure test unions and blanks for boiler certification. The thread lock is essential to prevent the loss of nuts and bolts due to vibration during running but care should be taken to avoid locking up running surfaces by using only a tiny amount.
Unusually for Aster the construction manual is disappointing in that though it takes the builder through the fitting and assembly stage by stage from Drawing 1 through to 16, several times it fails to identify the assembly of some parts. It should therefore be used as a guide to the order of construction but continual reference to the drawings will ensure nothing is forgotten. I find it advantageous to check off each part on the drawing as it is added. The drawings include ‘balloons’ around the edges showing more detailed views and dimensions of some of the similar parts and enable the correct selection to be made.
Assembly begins with the cylinders and here and throughout the design, the assembly process uses the well tried, developed and tested Aster methods. The application of these is one of the significant advantages to Aster ownership as lessons learned are incorporated into later models. Lapping of the port face and the valves is achieved using very fine emery paper provided in the kit and on to which a small amount of water is placed. Having achieved a fine overall ‘mat’ surface indicating no high spots, the surface is then polished on a piece of plate glass using Brasso or any fine metal polish alternative. The assembly of all four cylinders is similar and not difficult. However, care should be taken to apply only a thin even coat of the silicone ‘bath sealant’ to both sides of the cylinder gaskets if a good seal is to be achieved and none is allowed to get in the ports at the cylinder ends. Don’t forget to use a tiny dab of thread locking fluid on the crossheads for both piston and valve and a spot on the gland nuts wouldn’t go amiss to!
Next comes the assembly of the chassis frames and here a sheet of glass of perhaps 6” X 24” is recommended and is essential to get the frames absolutely true. There are no particular difficulties with this assembly which includes the installation of the axle pump. Don’t forget to bed the clack balls in by tapping an old ball of the right size, kept for the purpose, onto the seat using a short piece of brass rod. DON’T use the balls intended for use in the pump.
The next assembly is a bit of a fiddle and consists of fitting the wheels and the outside rods and a steady hand is definitely required. I suggest that you might like to keep this job for when you are fresh and that you have a glass of your favourite tipple before starting. On reflection perhaps the latter should be taken after!
Fitting the balance weights isn’t too difficult but getting the axle boxes into their horns in the chassis with the coil springs above them AND fitting the dummy suspension springs all in the same operation is! Make sure that before assembly you ensure the dummy springs aren’t distorted. Mine were a little out of line and needed gently teasing back. This mal-alignment is uncommon in Aster kits which are made using precision processes. But there are occasions when, perhaps due to a packing deficiency, a small distortion may take place. Check all parts as you go. I found that a little spot of the silicone glue in the top of the axle box helped keep the coil spring in place. A tiny dab of super glue helps hold the inner and outer dummy spring parts in place on the chassis whilst you thread the tiny M2-4 screws through the spokes and into place. Dip the end of the screw driver into the silicone sealer so that a little is trapped in the X and this will help hold the screw on the driver whilst you are putting it into place.
The next assembly is that of the outer cylinders and valve gear to the chassis. Once again, this is a fiddly job and great care is needed if you are going to have a sweet running engine. The weight shaft levers will be set up with the next stage of assembly but get things as close to correct angular position as possible now. Work methodically through the assembly in the order suggested and you will have no problems but don’t forget the sparing use of the thread lock fluid. Be particularly careful assembling the expansion link and remember that they are handed. I used a tiny spot of superglue to aid assembly of these tiny parts avoiding any on running surfaces. Again I can’t over emphasis the need to check off every part as assembly proceeds.
Next the middle cylinder block is mounted and the rocking levers connected to the valve gear. Mine matched up exactly and proved to me what an absolutely magic job Aster have done with their design and manufacturing. I was less happy with the reverser however. When completed I discovered there was considerable backlash in the whole reverser stand and this was all down to very much oversize bearings. I machined up new bushes and this problem disappeared completely giving a very accurate valve setting.
The lubricator is assembled at this stage and when hooked up later to the super heater hot header will enable an air test to be conducted after valve setting. This new lubricator is a great improvement over that used for example on the Aster King. It is mounted on the footplate and is fed with a steam supply to charge the long oil delivery pipe to the front end. The operating valve handle is opened briefly prior on starting and ensures oil reaches the cylinders as the loco moves off. After closing the valve and opening the regulator the oil system operates as a normal displacement lubricator.
Aster go to great lengths to explain the method for setting up the valves in the construction manual and the drawings are very helpful. The only tip I would add is that it is useful to make a small setting angle out of card to use for setting the return crank at 32.6 degrees. You’ve got micrometer eyes of course! Put the chassis on the glass plate and place your angle next to the return crank with the outside cylinder being worked on at forward dead centre. Nip up the bolts holding the return crank when you feel it is correctly set against your angle and then proceed as instructed in the manual. I was able to get extremely good results with equal opening at both ends in full forward and reverse and on both sides. This again shows the great manufacturing precision achieved by Aster.
The next stage includes hooking up much of the chassis pipe work including axle pump, inside and outside cylinders and the bypass valve. Don’t forget to thoroughly oil the valve chests before fitting the chest covers. We don’t want to damage those beautifully lapped port faces and valves! No difficulties in this stage and the outside steam pipes and smoke box saddle go on precisely as per drawing. But be careful to align the lubricator feed pipe along the inside of the right hand chassis frame and make sure it doesn’t foul the axle boxes.
Next comes the air test and requires the mounting of the superheater and an air test plug provided in the kit. An air supply is fed to the lubricator reservoir via the valve and the engine allowed to run for a short period in both forward and reverse gear. Correct any air leaks you might find though if you have worked carefully there should be none.
Next stage is the assembly of the boiler, backhead and combustion chamber and there are one or two tips here. Apply a thin coat of silicone sealant all over one side of each of the ceramic sheet parts you cut out. Carefully assemble them in the combustion chamber ensuring complete adhesion. This will ensure a good seal between the top edges and the bottom of the boiler. When installing the regulator and before screwing it right home in the boiler fit the restrictor 8-5 to the 8-19 regulator outer tube through the steam dome hole in the top of the boiler. If you screw the assembly all the way before this you may not be able to get the restrictor in. Be VERY careful you don’t drop the restrictor inside the boiler!
Because both the regulator and blower assemblies enter at the backhead and exit at the front tube plate you will be working blind at the front. I find it advantageous to insert a piece of 1/16th piano wire from the front and out through the backhead. This is easier to align and the assemblies can then be threaded over the wire and will be guided through the boiler. When assembling the water gauge and blow down make sure that before you fit the glass and tighten the lock nuts, you align the top and bottom fittings using a piece of rod of the same or very nearly same size as the glass. I usually use a suitable Number/letter drill tail.
The regulator handle is totally unsuitable if you intend to drive the loco! The cab roof overhang is considerable thanks to the Sir William Stanier’s concern for his crew’s health and safety. Access to the silly Aster regulator handle when on the move is virtually impossible. I made up a new handle to my favourite design and cranked a handle out to the left of the roof recess. It works just fine and with a suitable black tube insulator over it, avoids burns to the fingers.
The assembly of the boiler into the wrapper was accomplished without difficulties but do be careful when screwing the hand rail stanchions in. The threads will probably need a tap running through to clear the paint. Care is necessary to ensure a good seal between the boiler at the tube plate and the wrapper and a ceramic wrapper is utilised. I finished this off with a bead of silicone sealant neatly made at the front outer junction of the boiler tube plate and the wrapper. Apply sealant to the steam banjos on the chassis and to the superheater header faces prior to mounting the completed boiler as it is easier to get at them now. Mount the assembly to the chassis being careful to get the superheater header aligned with the banjos before entering the banjo bolts 7-12 and 7-14 being very careful not to get the sealant into any of the banjo holes. One of my banjo bolts was damaged by an imperfect thread entry in the superheater header and I ran an M5 X 0.5p tap in to clean this up. Andrew Pullen provided me with a replacement bolt by return of post and I can’t thank him and Ted Chatfield enough for their support throughout. Super job guys.
When assembling the blower nozzle assembly I applied sealant around the 9-11 nozzle holder to seal the bottom of the smoke box around the blast pipes. It is important not to have any air leaks into the smoke box. Next comes the completion of the smoke box assembly which is very straight forward. When completed push a suitable size of straight brass wire into the double blast nozzles to ensure they are aligned perfectly with the middle of the petticoat pipe and chimney. Repeat this with the blower nozzles though this will require a finer piece of wire. It is absolutely essential that these blower nozzles are aimed inside the petticoat pipe at around mid point to the top of the chimney. Try to make as neat a job as you can of fitting the ceramic sheet liner to the smoke box wall as this is also contributes to the integrity of the seal.
Fitting the running boards comes next but before they go on you have to fit all the ‘twiddly’ bits. Be very careful fitting these as several are secured using M1.4 and M1.7 screws and it would be very easy to cross-thread these or even worse. If you have no M1.4/1.7 taps to clean out the paint from the thread then at least dip the screws in a little lubricant before fitting. You will notice there is a small error on the drawing for this stage. The dummy snifter valves are shown the wrong way around. The drawing identifies the error with a cross through the part numbers 11-18 and 25 and shows them the correct way around in the top left hand corner of the drawing. There are no difficulties in fitting the bedecked running boards to the chassis.
Fitting the cab, smoke deflectors and hand rails offer no challenges but please note that the ‘glass’ in the two windshields are very vulnerable, particularly during servicing of the engine. Care should be taken to protect them when the loco is laid on its side for lubricating axle boxes and inside valve gear.
Last job on the engine is fitting the bogie and truck and the burner. These are quite straight forward and the only tip here is that when you are assembling the side control spring, ensure that the leaves 13-4 of the spring are adjusted so that all four ends are in contact with the frames.
The burner you will find is at least 2 mm too deep! If you want to avoid problems with turn outs and possibly stud contacts [yes, some people still have them!], you will need to cut off the plugs in the bottom to just below the feed tube. I did this with a jeweller’s saw and silver soldered a new plug in each tube base using small discs of brass plate filed to shape after soldering. After this I had no trouble whatever.
Aster is now supplying ceramic yarn for burner wicks and this works beautifully. They recommend 30-35 strands in each tube cut so that 12 mm stand proud of the tube. Thirty worked for me and was free enough to allow meths to wick freely but not flood and when the burner was turned upside down and tapped on the bottom the wicks didn’t drop out. Because I had finished the tender when I came to this stage I tested the burner by mounting it on a fire brick with the supply tube from the tender absolutely horizontal. This test served the dual purpose of checking the fuel tank and burner for good flow and no leaks and enabled me to light the burner to ensure a good healthy flame. Because air has unrestricted access to the wick you aren’t quite able to simulate conditions when mounted in the combustion chamber. However, providing the flame burns blue around the wick and the flame is about 3” high you should be fine.
The tender is a no brainier with nothing difficult in assembly. The only tips I would add are to be careful to seal the fuel reservoir properly under the tender floor and to make sure you seat the hand pump balls correctly on their seats as you did for the axle pump. It saves a good deal of hassle if you assemble the tender coupling pin 15-24 to the footplate 15-23 before you fit the plate to the chassis. Anyone who has built an Aster before will remember this little trick!
Fit the Fox water transfers as per the instructions on the packing and you will have no trouble. I haven’t sealed mine because I can’t stand seeing the unsightly mess the clear varnish recommended to seal them, leaves on the paintwork. I have never sealed those on my King and have not suffered any consequences. If one comes off in the future I will replace it.
I conducted several tests at suitable stages in assembly. These included leak checks on tender tanks, air tests on the chassis to ensure no air leaks in the steam lines and that the valve timing was the best I could achieve, pressure tests on the boiler prior to mounting on the chassis and a final pressure test after assembly before it was first steamed. For the latter test I used an adaptor in the steam dome tapping. If you do these tests at the appropriate time you can avoid having to strip significant assemblies down again to rectify any errors.
All was now ready for the first steam test which I conducted on my rolling road test bed. Because there is a double blast pipe one exhaust has to be blanked off with a suitable disc of rubber or metal and the blower inserted in the other. Steam was raised to 2 Bars in about 2 minutes and the blower and disc removed and the loco blower opened slightly. The burner roared in approval and within 5 minutes. Full pressure of 4.5 Bars was reached and the safety valve blew off. I held it closed with a pair of needle nosed pincers to check that the second safety valve would blow off too which it did at very little greater pressure rise. Then the lubricator control valve was opened very briefly to charge the oil gallery to the cylinders. The throttle was cracked open and the drivers eased around carefully by hand to discharge any condensate from the cylinders. After a few revolutions and a small fountain from the chimney the throttle was opened a small amount more. The engine immediately responded and the wheel began to whirl around. I closed the blower and almost immediately the safety valve blew off again. The water sight glass had been showing three quarters full at start up and so I now closed the by pass valve to allow the axle pump to top the boiler up again and quieten the safety valve. After a successful run of about half an hour I shut down and allowed the engine to cool. Later a very detailed examination of the engine showed nothing coming undone and only the cylinder gland nuts on one cylinder slightly in need of adjustment.
After completing my examination and a thorough lubrication of all bearings and mechanism, replenishing the water, oil and fuel, the engine was run on a friend’s track with complete success. The axle pump requires careful management initially and its performance characteristics learned and understood, but thanks to a very good hand pump this is not a worry. Andrew advises me that one or two people have reported initial short comings with it but that it soon settles down. After some 20 hours of operation I can attest to this though I have chosen to enlarge the diameter of the hole in the union connection between the loco and the tender for the following reason. The pipe bore for almost the whole run from tender to axle pump is around 3 mm bore but at the connector between the loco and tender that at the union is only 1.5mm! This I felt was certain to cause a restriction on the suction side of the axle pump with consequential possibility of cavitation. I tried opening the union out to the maximum possible of around 0.08" but there was little improvement. So, there was nothing for it but to modify the arrangement to allow a 1/8” bore through the connector.
This was achieved using a short piece of 5/32” copper pipe to the end of which was silver soldered the appropriate nipple with a 1/8” bore. The Aster connector was drilled out to 5/32” to allow this assembly to pass through and protrude about ¾” from the tender side of the connector. This was cut off at that length and a small ring of 3/16” tube, 1/8” wide, was silver soldered to the end. The assembly was cleaned up and the neoprene pipe from the tender hand pump was then pushed over this end and wire-locked in place. No problems with water delivery have been experienced since fitting the modification.
After completing my examination and a thorough lubrication of all bearings and mechanism, replenishing the water, oil and fuel, the engine was run on a friend’s track with complete success. The axle pump needs careful management initially and needs to be understood, but thanks to a very good hand pump this is not a worry. Andrew advises me that one or two people have reported initial short comings with it but that it soon settles down. After some 20 hours of operation I can attest to this though I have chosen to enlarge the diameter of the hole in the union connection between the loco and the tender. The pipe bore for almost the whole run from tender to axle pump is around 3 mm but at the connector between the loco and tender the bore of the union is only 1.5mm! This I felt was certain to cause a major restriction on the suction side of the axle pump. I tried opening this out to the maximum possible but this showed little improvement. So, there was nothing for it but to modify the arrangement to allow a 1/8” bore through the connector.
This was achieved very easily using easily obtainable material and I used a short piece of 5/32” copper pipe to the end of which was silver soldered the appropriate nipple that has a 1/8” bore. The Aster connector was drilled out to 5/32” to allow this assembly to pass through and protrude about ¾” from the tender side of the connector. This was cut off at that length and a small ring of 3/16” tube, 1/8” wide, was silver soldered to the end. The assembly was cleaned up and the neoprene pipe from the tender hand pump was then pushed over this end and wire-locked in place. No problems with water delivery have been experienced since fitting the modification.
So, now when you have finished assembly you can sit back and admire your beautiful model, the result of some 100 hrs of your handy work. It’s a magnificent model and was the magnum opus of our dear friend the late David Jenkinson who was Aster’s consultant for this engine. This was his favourite and it’s very sad that he never got to see the results of all his work with Aster. All I can say is that as a GWR enthusiast I’m proud to have an LMS engine in my stable of locos. After all Stanier was a GWR man through and through and he never forgot his heritage or singing its praises. I like to think that had the GWR Board done the right thing and promoted him instead of Collett this would have been a GWR engine with a copper capped chimney!
A version of this article first appeared in the Summer 2005 issue of the G1MRA Newsletter and Journal. Permission to reproduce it and the photographs here on SouthernSteamTrains.com was given by Dave Stick.