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(Part 2)

by David Stick

Aster's C62-2. The massive proportions of this magnificent engine can be seen in this view.




The Aster kit comes in a large reinforced cardboard box containing all the parts in separate smaller boxes and packages. Included is a large format manual of superb isometric drawings of your locomotive, each one covering a different stage of the building process. The drawings show all the part numbers required at a particular stage of construction and the numbering system for the parts follow the assembly order. The original number is retained where parts like unions and special nuts are used in more that one stage. Also included is an instruction manual with a detailed ‘blow-by-blow’ account of what to assemble and when. It has to be said that, although the order in which things are put together is clearly indicated, the English is sometimes a little odd, but then, how is your Japanese?  Occasionally, the assembly of a part might be missed but if you are reading the drawings as you go (as you should), you will quickly pick this up.


The JNR C62–3 has a new type of manual that includes the drawings, part numbers and assembly instructions all in one. Each drawing addresses the assembly of a particular section or sub section starting with an ‘exploded’ view and then progressing to the fully assembled section. I’m as yet undecided as to whether I prefer this method or not.


Also included in the kit are some essential tools. Those not included are usually found in every modeller’s toolbox. Most kits have always include cross head screw drivers, Allen keys, silicone sealant, paint touch up, fine emery paper and at one time, even a pair of gloves! To these tools I would add some really good tweezers of two or three sizes, a set of metric nut drivers, a pair of side cutters, two or three sorts of pliers including a square ended and needle nosed pair, 2mm and 5mm taps and dies used for cleaning up the occasional paint filled thread, small slot head screw drivers, a set of fine Swiss files, a small tube of screw-lock and a sheet of glass perhaps 12ins. by 4ins. I’ve probably forgotten something – but you get the message I’m sure.


Back in 1984


Before assembly of the locomotive begins it is very important to read and digest the instructions right through. Then as you begin each section read these again in advance. Always remember that it is essential to assemble the engine in the order recommended by Aster – failure to do so will almost certainly cause trouble. Of course, if you wish to ‘get your eye in’ you can always build the tender first, as this is a separate vehicle. I found this an advantage when I built my first Aster kit back in 1984 and it taught me about using the drawings and instructions to maximum advantage.


Normally when building the model, you will begin with the cylinders and, as for all assemblies, this first requires the removal of all the parts necessary for the assembly only from their packaging in preparation. This is the time to do an inventory check to make sure everything is included and it should be remembered at each and every stage. I have rarely had a problem with parts missing but you must check before starting. If things are missing, damaged or incorrectly machined you should contact your distributor immediately.


As you do this inspection, you should examine each part to ensure you understand how it will be used and to ensure that nothing is damaged. I would stress that this would be very unusual because everything is so well packaged. However, on one occasion when building a Nord 231E, I did find the steam drillings to one end of the inside cylinder casting to be missing. Since Aster use CAD/CAM and CNC machines it is difficult to understand how this could have happened but was obviously a very rare quality assurance problem.


To maximise the performance of your locomotive, the careful assembly of the cylinders is essential. The valve running surfaces must be very carefully lapped using the fine emery paper provided to ensure a good seal and no steam leaks. This is where your sheet of glass first comes into use. Lay the glass on a FLAT surface and tape enough 1000 grade emery to it to enable lapping to take place. Holding the piece to be lapped face down on the emery, and using short straight strokes away from you, lap the surface until all tool marks disappear. It usually takes about fifty to a hundred strokes per piece to achieve this. When all of the surfaces to be lapped have been treated, remove the emery from the glass. Polish all running surfaces using a lint free cloth and store safely to avoid ruining all your hard work.


The combustion chamber. Under the boiler is mounted the combustion chamber or firebox. This is a stainless steel box lined with insulation and into which will be mounted the burner assembly of three burner tubes with wicks installed. The extra insulation material thickness is one way of reducing the primary air access should it prove necessary to preclude cold air ingress.


The ‘Berkshire’ boiler back head. The enormous size of the Berkshire boiler may be seen in this view, which also shows the fire hole through which the burner wicks must be ignited. Note also the addition of a whistle valve and large whistle to this loco.


Berkshire’ front tube plate. The boiler is shown mounted inside the casing in this view. Note the sealing of the boiler to the cladding with a generous caulking of silicone sealant. The flue tubes will be fitted with a large superheater fed from a cold header attached to one of the two threaded unions mounted on the tube plate above.


Diametrically Opposed


The fitting of the Rulon piston rings is a simple task, but some people have expressed doubts about the effectiveness of these seals. Every one of the thirty or so Aster locos I have built have these seals fitted and I have never had a failure yet. It is important to ensure that the gap in each piston ring is not in line with the second ring and is simple task to ensure they are diametrically opposed before carefully pushing the pistons into the cylinders. A dribble of steam oil helps with sliding them into place and should also be applied to all ‘0’ ring seals on piston and valve rods. The rest of the assembly is straightforward so long as care is taken not to use too much silicon sealant on gaskets. For some while now I have been soaking cylinder gaskets in machine oil for five minutes before assembly and have found this to be entirely adequate. If you decide to use sealant, be particularly careful not to allow any into steam passages or port faces.


Ensure that when fitting the slide bars the rear cylinder end cover bolts are loose. Slide the piston in and out to ensure free sliding movement and nip the bolts up. Check free movement again after.


When you attach the crosshead I recommend a little nut-lock be applied to the piston rod thread to ensure that there is no movement here. I once had a nasty experience of a piston rod slowly working its way out until eventually the piston struck the front cylinder cover! Luckily it did little damage but had I not noticed the ticking sound it might have been a different story!


Assembly of the main frames and stretchers should be completed without difficulty but be sure to do this on your glass sheet to ensure the frame is straight and true. Failure to do this may result in sticking axle-boxes and an engine prone to derailment. Assembly of the wheels to the frames is straightforward as the axle-boxes are already mounted. Turn the frame upside down and make sure that the spring pockets in the axle-boxes are uppermost. Put a little grease into them to hold the springs in place as you slide the axle down the horns.


Pump Performance


The horn keeps are usually held in place with two counter sunk bolts that have to be fitted through the spokes of the wheels. Now, the axle-box springs are trying to push the axles out as you fit the keeps and you really need another hand growing out of your chest to hold everything in place! I manage by putting a little silicon sealant on the end of the screwdriver to hold the screw and, whilst holding the keep down in place, thread the screw through both the spokes and the keep and into the frame. When all are in place turn right way up and ensure that the axle-boxes move up and down smoothly in the horns without binding.


The axle pump is normally fitted at about this stage and is pretty straightforward. When assembling the pump, care should be taken to seat the clacks correctly. Measure the diameter of the ball to be fitted and obtain a spare ball of the same size. Place the spare ball on the valve seat and using an alloy or brass rod against the ball, strike it once or twice with a light hammer. This should form a nice seat for the balls in the kit and prevent any leaks. Pump efficiency is greatly affected by this, the lift on the ball allowed and the diameter of the inlet pipe to the pump. The lift on the ball is usually controlled physically by a stop and should allow approx. 0.30in lift. This is important and can usually be arranged by careful adjustment of washers under the seat. For a few years I have been replacing the balls provided in the kit with ones made of Nitrile rubber. This has the advantage of conforming to the seat perfectly and providing more reliable long-term pump performance.


The inlet pipe inside diameter should be approx. 1/8ins. or the metric equivalent. Check to make sure that there are no fittings between the pump inlet and the tender that have a bore significantly less. If there are they should be drilled out as far as possible or the fitting changed for a larger one.


When assembling the pump into the main frame make sure that the pump ram end and the matching fork end on the pump eccentric are in alignment and that the screw hole faces down. The eccentric is held onto the axle with a setscrew and this can be slacked off to allow side movement of the eccentric. Fitting the attachment between eccentric and pump ram will be much easier if you face the hole downward. However, remember that when all is in place the ram must be rotated through 90 degrees to allow the fork end vertical movement as the axle-boxes move in their horns.


Fine Swiss Files


Assembling the cylinder and motion to the frames is usually a comparatively simple task, although there is quite a lot to do and, once again, I can’t over emphasis the need to build in the order shown. Take your time and do things in order and there should be no problems. Probably the most difficult task is assembling the expansion links. It is imperative here that the trunnion slides in the slots of the links without any resistance. However, it is equally important that there is no fore and aft slop – which will make for poor reverser performance. The parts are laser cut and only require careful use of fine Swiss files to ensure a good smooth fit.


The assembly of the ‘sandwich’ of parts is a fiddle and once again the use of some assistance is of benefit. Make sure you have the correctly handed parts available and separate the right and left hand expansion link sets. I then take the outer link face and position all four of the corner screws through the holes, holding them in place with a touch of superglue. Add the tiny spacers and other parts including the radius rod and the trunnion, and then fit the inner link face. Lock the nuts on the inside using a tiny dab of screw-lock. This is highly recommended as there is a great deal of vibration here and lose nuts will soon result in an expansion link assembly coming to pieces. Not a happy prospect.


When assembling the weight shaft it is very important to make sure that the crank that will be attached to the reverser stand is at right angles to the cranks that provides the drive to the radius rods. With the reverser stand screw in the mid position the radius rod must be in the mid pint of the expansion link, usually right behind the link support bearing. This will ensure that when you are setting up the valve timing using the eccentric crank in both forward and reverse, you will have equal movement.


Setting the valve gear of a loco is not a difficult task if taken slowly and methodically. You set one side up first and then move to the other. In a three or four cylinder engine the same applies except that since in most cases the inside cylinders have valve actuation derived from the outer, the outer left and right are completed first.


In Walschaerts’ gear the angle of the eccentric crank to the horizontal is about 34 degrees and to aid setting it’s a good plane to make your self a little angle gauge out of a stiff piece of card. Position this gauge by the crank and set it by locking the screws.


Set the reverser on the stand to mid gear. Rotate the wheels and watch the movement in the left hand valve chest. As you will have seen during assembly, there are three ports in each valve chest. The two outer are inlet ports to each end of the cylinder and the one in the middle is the exhaust. With rotation, we are looking for equal valve movement on either side of the mid position of the ports. This is achieved by adjusting the position of the valve by releasing the setscrews holding the valve to the valve rod. In mid gear no ports should open. If they do, and you are sure that the valve rod movement is equal either side of mid position, you must adjust the crank eccentric a little. It will not be much so move it a degree or two and try again.


A Good Dose of Steam Oil


When you are happy that this is set properly, reset the reverser to the full forward gear position. This is set when the radius rod is near the bottom of the expansion link. Rotate the wheels through 360 degrees whilst watching the valve movement and the ports being opened as the valve moves. Position the left hand piston at forward dead centre and see where the left hand valve is with respect to the front edge of the forward port. We are aiming for a ‘line for line’ position for the valve and if you don’t have it, reset the valve with the setscrews so that this is achieved. Now, rotate the wheels until the piston is at back dead centre and check that the rear edge of the valve is line for line on the back edge. Small adjustments must be made between the crank eccentric and valve position on the piston rod until you reach the optimum position. When you are happy that you have the best possible setting, repeat the process for the right side.


The inside cylinder[s] are next examined but here only the valve may be adjusted but if the geometry hasn’t been altered, this should be all that is necessary anyway.


With the valve chest covers in place and connections made to an air supply such as an air compressor you can now test your handiwork. The last few Aster kits I have built have all been provided with the necessary test connections to make this easy.


Before putting the chest covers on give the chest a good dose of steam oil and rotate the wheels to get plenty down through the ports to the cylinders. Also you should oil all the axle and motion bearings thoroughly using good quality machine oil. Although the air test will be but a brief one, we don’t want to damage the bores or valves and running on air is potentially damaging if you run too long without proper oil feed facilities. The first test is static and should be run at an air pressure of around 10psi with the reverser set in mid gear. You are looking for any leakage and rectifying where necessary. This test should be followed by rotating the wheels by hand in mid gear to ensure that is no airflow through the ports. Then you should follow up by tests at full forward and reverse gear position.


If you have been careful with your setting procedure you should get good results. If the run isn’t successful you will need to remove the steam chest covers and repeat the valve setting procedure again. It is an iterative process in which you narrow down the errors in setting the eccentric crank angle and the slide valve position and a patient approach pays huge dividends.


Dummy Backhead


Fitting out the Boiler. The boilers developed by Aster have already been described and by far the most common is the C type designed by our old friend and mentor in G1MRA, John Van Riemsdijk. There have been some detail refinements to this in the past few years the most important of which is the inclusion of a dummy backhead. The A4, ‘King’ and one or two German locos didn’t have this but a rather ugly footplate resulted! The hot gas flow was reversed from the top of the burner via a box mounted on the back of the combustion chamber in which is located the burner. This box then sits on the back of the boiler and protrudes onto the footplate. In the later examples after the mid 1990s this is disguised by a dummy backhead simulating the prototype and including details such as the firedoor and surrounds. This has provided for a much-improved appearance. The combustion chamber is lined with insulation material and should be mounted carefully as at the top edges it provides a seal against the boiler.


There are very few wrinkles in finishing the boiler and its mountings. The fittings are very straightforward and only fitting the regulator and blower assemblies through the boiler backhead and front tube plate is likely to cause any problems. The easy method is to take a piece of piano wire and push it through both holes and then push one end into first the regulator. This can be pushed down the wire until it gets to the forward tube plate where it can be carefully guided through and fixed in position at the backhead. Before you have assembled it in its final position you will need to fit the steam flow restrictor in the top of the regulator tube under the dummy steam dome. Great care is needed here as you can easily drop it into the boiler and getting it out would be tedious! The safe way is to thread it on to a short piece of wire and then push the wire into the regulator hole with the boiler horizontal and the dummy dome hole on the side. The restrictor can be teased into place and the slot in its top used to engage the thread. Once started, the wire can be removed and a screwdriver used to drive the restrictor home. Remember that the restrictor must be positioned at the top when the regulator body is finally screwed home and the lock nut tightened.


Fitting the water sight glass sometimes causes people strife though it shouldn’t. Don’t put the glass tube anywhere near the assembly until you are quite sure the top and bottom fittings are in perfect alignment. You can use the pump handle provided in the kit to do this and it should be a nice sliding fit before you fit the glass.


Bulleid ‘Pacific’ smokebox. This view shows the unusually shaped smoke box with its chimney. Mounted on the boiler tube plate behind can be seen the cold header for the superheater. This fits over the end of the regulator steam pipe and steam passes through the flues in the superheater tubes and back to the hot header which can be seen in front of the smoke box. Here the lubricating oil is injected through the U shaped pipes from the reservoir mounted below the front footplate the filler for which can be seen on top. Steam delivery pipes to the outside cylinders can be seen fitted to the end of the hot header. The steam connection under the smoke box is the exhaust from the middle cylinder.


Bulleid ‘Pacific’ backhead. The reverser can be seen on the left of the footplate and the open copper pipe on the right is the blow down. This will be fitted with a length of neoprene pipe and will project water down to the track. Black lever is the blower and the red the regulator.


The Bulleid ‘Pacific’


Next the boiler is mounted in its cladding, with or without insulation material. I always used to fit this without fail, but have discovered that for some locomotives, where a good cladding exists right around the boiler, this isn’t essential. There is no difference in the steaming qualities of the C type boiler with and without the insulation on, for example, the ‘Duchess’. Take your choice. However, there is one place where it must be fitted and that is at the front end of the boiler where it acts as a seal with the smoke-box. Usually two or three rings about one inch wide are required and should by glued on using the silicon sealant provide in the kit. The boiler should be a nice push fit at the front end when installing in the cladding.


Whilst not seemingly of any advantage in some boiler casing, the Bulleid ‘Pacific’ being an exception, in the smoke-box the addition of inside insulation is imperative. It acts as a very effective seal to all the joints around the inner wall and the joint with the smoke-box door surround. Great care should be taken over fitting the insulation in this assembly, as more steam locos fail first time out because of leaking smoke-boxes than probably anything else – other than badly fitted wicks and blast pipes not properly adjusted. More of which anon!


As the whole loco is constructed from parts machined using CAD/CAM, the build up of tolerances is carefully controlled. It needs to be – particularly at the front end, as the position of the blast pipe relative to the chimney centreline is extremely important. It is imperative that they are exactly concentric and that the height of the blast pipe nozzle, relative to the throat of the chimney, is also spot-on. Since, in most Aster locos, there is no method of adjustment other than re-machining or shimming, the kit must be manufactured very accurately. Make yourself a small gauge made like a very long equilateral triangle so the taper is 1:6. With this resting in the top of the chimney the tip should sit in the blast nozzle. As yet I have never found one to be out of alignment if assembled correctly.


Unlike the blast nozzle, the blower however can be adjusted if the nozzle[s] is (are) not quite right. The method of checking alignment of both is to insert a fine brass wire into the hole in the nozzle and see where it passes in the chimney. In both cases it should pass through the centre of the chimney venturi. This is possible for the blower as it is offset in the smoke-box with the nozzles pointing at the middle of the chimney throat. However it should not encroach into a cone of 1:3 between the blast nozzle and the petticoat at the base of the chimney.


A3 cab. The very compact cab is shown and in the bottom left hand corner of the footplate can be seen the oil reservoir. Below almost at track level is the bypass valve.


Aster Japanese C62-2 cab.  This view shows the very complicated footplate of this loco. This loco may be gas or coal fired and in this view is shown set up for gas. Included in the controls are cylinder drain cock operating lever mounted above the reverser, gas control, blower control, regulator, pressure gauge, whistle and water gauge glass. The end of the gas burner may be seen just above the footplate.


Pipes are Pre-Annealed


Final assembly. If there is one area that causes some tooth sucking it is probably the fitting of the boiler to the chassis. I have heard several people say how they have had to file away the bottom of the firebox of for example, the ‘Flying Scotsman’, to get the boiler to fit. Well, all I can say is I have never had to modify any of the boiler cases I have assembled. They aren’t easy to assemble but usually careful study will reveal where a little ‘springing’ of the case with the loco held vertically will get you out of trouble. Force should NEVER be applied for any reason at all. It will fit, believe me!


Pipe bending should be done with a set of small pipe benders or carefully and gently in the fingers. Again, for both the ‘Duchess’ and the ‘Flying Scotsman’ the backhead pipe-work needs to be bent quite acutely in order to clear the cab walls and roof. The copper pipes are pre-annealed and should bend easily with care. Just take it slowly and carefully to avoid a kink.


Now to the burner and, as I have alluded before, this needs to be assembled to the drawings to ensure a good performance. Most have a three-tube arrangement and each tube needs to have the wicks loaded so that there is 10-12 mm of wick sticking out of the tube top. Carefully measure the distance from the top of the burner wick tube to the top of the fuel tube in the bottom of each burner and add 10-12 mm. Take the hank of wick material provide and measure off this distance so that you have about 30-35 strands of wick for each tube and a nice sliding fit in the tube. Carefully push the wicks into the tubes avoiding any curling up at the bottom by stopping when there is the required 10-12 mm at the top. Turn the burner assembly upside down and tap the tube base closure and the wicks shouldn’t fall out. Put the burner on one side until the tender is completed. Because the wicks tend to swell in use there may be a need to remove a few after some running. Also, hot or cold weather may require adjustment of a few strands.


Good steaming qualities are a blend of tuning the front end and the wicks, plus the need to minimise the primary air access to the burner. Some locos need more insulation material added to the inside walls of the combustion chamber to decrease this air and prevent ingress of cold air to the boiler. Be careful to seal the top edge of the joint between the combustion chamber and the boiler to avoid any possibility of flame getting through and a possible fire if meths ‘wicks’ through to the insulation. This has reportedly occurred to one Bulleid ‘Pacific’.


Silicon Sealant


The tender is an assembly job and little needs to be said about it other than in the supplied instructions. Tenders are usually fitted with a hand pump these days and the clack valves need to be treated as you did for the axle pump. Joints in the water tank need to be carefully sealed by running a neat bead of silicon sealant around them but be careful not to get any sealant in the pipe work or feed problems will result. When the assembly is complete fill the water tank with water to check for leaks and rectify where necessary. Also check the fuel tank for leaks though this is very unlikely.


When you are satisfied, fit the tubes that connect the tender to the engine and couple the burner to the meths tube. Mount the burner at the same height as it will be in the engine and put some meths in the fuel tank. Turn the fuel tap about one turn open and allow the burner to prime with meths. After two to three minutes, light the burner and check that you have a nice blue flame with an orange tip about four to five inches high. Extinguish the flame if the test is satisfactory and turn the tap off. Drain out the remaining spirit and make the final assembly of the tender to the engine after fitting the burner.


The ‘Berkshire’ front end. Another even bigger engine capable of massive haulage.



 part 1 < part 2 > part 3


Appreciation is expressed to Dave Stick for sharing this series along with other articles and photographs for posting to SouthernSteamTrains. com.    


Dave Stick spent all of his working life as an aeronautical engineer.  His hobby has always been model steam locomotive building.  He built his first Aster locomotive, a New York Central Hudson in 1984.  Having graduated from college and served an engineering apprenticeship, he was employed as a development engineer in the gas turbine industry. Dave later joined the Royal Air Force as an engineer officer and retired after 20 years service and immigrated to Canada. There he worked for Boeing Canada retiring for a second time from the post of system director.  Returning to his beloved home in Cornwall, England in 1999, Dave Stick has spent the past decade building and running his collection of Asters.




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