Building the Aster Bulleid Battle of Britain
By David Stick
The eagerly awaited arrival of a new Aster is always an exciting time and this was especially true after Andrew Pullen of Aster UK announced the plan to produce a Bulleid Battle of Britain class locomotive. The first kits arrived in UK in June since which time they have been flying off the shelves at the distributors and agents.
The choice of the B of B, of course, doesnít inhibit those of us with a preference for the West Country variety from exercising our prerogative of choosing a name from the long list of possibilities. Your favourite plate manufacturer will no doubt oblige as he/she has for me. Whether you choose a BR or Southern Railway version of the kit it will have suitable transfers for numbering any of the 110 in the whole class. Just remember to get a good photo or better still a good book on the class and you can make your chosen loco an accurate replica of the original. Donít forget that the smoke box door mounted plate on the Southern version has the year of the locos manufacture on it and so this may need changing.
Love them or hate them [whatís to hate!], Oliver Bulleidís new breed of engine and his very innovative approach to their detail design in the war years has certainly got the attention of railway enthusiasts down the ensuing years! Of course, he learned at the knee of another master loco designer and innovator, Sir Nigel Gresley for whom he was the technical assistant. However, it wasnít until he left the LNER to take up the position of Chief Mechanical Engineer to the Southern Railway that he was able to spread his wings and we discovered his true genius.
Richard Derry in his wonderful book on West Country and Battle of Britain Pacifics, reiterates Bulleidís views on what he considered the ĎDirections for Improvementsí for the steam locomotive. This is a real eye opener as it clearly shows his knowledge of operating steam locos and the problems experienced since the invention of the steam loco. Anyone who doesnít have this book should make it top of their shopping list as essential reading for anyone building the kit.
Whether Bulleid achieved his aims to improve loco design with his Merchant Navy and B of B/WC I leave you to decide. But his approach was extremely innovative and far more successful than some would have us believe. Look at the results of the interchange trials in 1948 for a view of their actual and potential performance had they been owned by a development organization with the money to spend post Nationalization and a desire to look further than what came out of Crewe!
Once again Aster has been very successful in capturing the essence of the loco chosen with their latest offering. Whatís more they are a delight to build yet including a nice challenge. Whether you chose a Southern or BR version you will be delighted with the quality of the finished product. Aster has followed the same general well tried and tested design approach as usual except for one major deviation, the valve gear. Because the full size loco has three cylinders and inside gear the model also had to have three sets inboard mounted. They have come up with a derived Walschaert gear which whilst far from the Bulleid chain driven gear, is none the less innovative and brilliantly executed. In this, Aster somehow reflects the innovation Bulleid showed with his design.
This assembly is a complete, self contained unit and is built as a subassembly in its own frame. It has generous bearing surfaces and incorporates laser cut and well finished components yet retaining motion entirely in proportion to the scale. Subsequent to assembly the complete gear is placed between the loco chassis frames and coupled to the valve rods, reverser and eccentric drives. Other than centralizing the valves, no further valve setting is necessary. Job done! I suspect we shall have far less trouble with this gear than Bulleid did with his!
In what follows here I will not repeat the list of tools required as this can be found in my introduction to previous articles on the subject of building Aster kits. Suffice it to say that there are no new requirements and most modellers will have what is needed or can obtain them easily. One thing I will re-emphasize however though I know not all agree, but I recommend that the valve gear bearing pins and lock nuts should be given a touch of locking fluid to avoid loosening in service. Only a tiny dab is necessary and it can be easily Ďbrokení with the application of a little heat in the unlikely event of need to disassemble parts. Failure to do this may well result in a disconnections and possible breakage.
The one failing with this kit that I would warn kit builders about up front is the paucity of detailed instructions in certain areas of the instruction manual. However, anyone who can read the engineering drawings that also accompany the kit will have no difficulty providing a detailed check is made at each step. Use the manual as a rough guide to what order to assemble parts. Thatís not to say that there arenít unfortunate errors in the drawings and I will try and draw your attention to these as we go.
As usual with Aster kits we start with the cylinders. Because of the quality of the CNC tooling used in the manufacture there is an excellent finish on the port faces of the cylinder castings and hence little work is necessary using the abrasive paper. Only about 30 or so strokes was necessary on each of the cylinder port faces and valves to remove any residual tool marks. Assembly of this section then follows as per drawing and no errors have been detected.
When assembling the cylinder sets do be careful not to put too much sealant on the gaskets. Lay each gasket on a piece of kitchen paper and then spread a VERY thin smear of silicone sealant on both sides of the gasket. Pick the gasket up with tweezers and place in position to avoid handling the faces with sealant on them! It is particularly important to take great care of the port faces during this process as any sealant escaping onto these will almost inevitably result in fouling of the slide valves. I have found that instead of using sealant for the steam chest gaskets soaking them in machine oil for 10 mins. and then putting them in place is very effective in providing a seal and there is no risk of fouling.
I suggest that before inserting the pistons fitted with rings [which you did make sure had the ring gaps opposite to one another circumferentially didnít you?] in the cylinder bore, you pour in a little steam oil rather than machine oil as Aster suggest. Using this type of oil I have never had any problem demonstrating a good ring seal. With a finger placed over the port face and the end covers in place it should be possible to pull/push the piston rod to full stroke and have it fly back to the original position.
Section 2 assembles the frames and mounts the axle pump, bypass valve and cylinders. There are no drawing errors here that I have yet detected; however, there are a few tips on getting it together easily and with smooth operation of the rocking levers and valve rods. Prior to installing the middle cylinder, file or face off 0.020Ē from the head of the 3-4 bolt used to close the drilling in the side of the middle cylinder [refer to Drawing 1]. Failure to do so will usually result in the link 2-9 joining the rocking levers on the left side, fouling the boltís head. Whilst this isnít fatal it does increase friction loads in the valve gear and these should always be minimized. Donít bend the lever to clear, use the proper engineering solution!
The next tip is to ensure that when assembling the axle pump [and eventually the tender pump] not to forget to seat the ball valves properly. To do this you should ideally take a spare ball and place it on the seat with the seating facing vertically. Take a small piece of alloy rod or perhaps a piece of dowel and strike the ball against its seat once or twice with a small hammer. This will take the edge off the seat and make it conform to the ball radius thereby improving the seal. Also check that the ball lift is correct by measuring the distance from the top of the ball on its seat to the end of the housing. Then take the cap bolt and measure from the underside of the head to its end. Subtract the smaller measurement from the larger and the difference will be the clearance or ball lift which should be around 0.035 ins. The tolerance is about +/- 0.003 and degraded pump performance will result if the ball lift isnít in range. There has been a good deal of criticism of Aster pump performance in the past and I believe some is due to this clearance being incorrect. It is often found to be too small and the solution is to take off the appropriate amount from the cap bold face. In the unlikely event of it being too big, material will need removing from under the head of the cap bolt or the bolting face.
The next tip concerns the multiple blast nozzle housing 6-5 and its mating with the branch pipe 2-5 and is best considered with respect to both Drawings 2 and 6. I believe that the 2-5 pipe has been manufactured poorly. On each of the kits I have assembled so far when trying to fit the multiple blast nozzle 6-5 and its associated support frame 6-6 to the branch pipe 2-5 in Section 6, it has subsequently been impossible to fit the support frame to the loco chassis without considerable frame distortion. Even with a distorted frame it has proved impossible to get the nozzles to point directly upward, essential for good steaming! I believe that the bend in the 2-5 copper pipe has been made incorrectly and though it is possible to re-form it to regain the height, the process may crush the pipe unless great care is exercised and the pipe annealed properly. On only one kit have I been able to reform the pipe and get it to fit properly and on that one there was no evidence of previous crushing during its initial manufacture. If you can reform it great care should be exercised to keep a clearance between the pipe and the front top edge of the middle cylinder block or future damage may result.
There is an alternative and relatively simple solution and a little time spent making a 1/8th ins. spacer in brass to fit on top of the multiple blast nozzle will cure the problem. This will lower the nozzles and re-align the pipe so that the flange will rest against the nozzle housing. Make the spacer with a D shaped hole to provide clearance for the blast and blower nozzles and two holes for the locating screws. Cut this D hole out by chain drilling, a then cutting using a watch makerís fret saw and clean up with fine files. It only took me about 30 mins. of extra work. There has been no degradation in performance resulting from the lower blast nozzle position relative to the chimney venturi.
Step 3 is the valve gear assembly and is shown in Drawing 3. Unfortunately, brilliant as the valve gear is the Aster draftsman did a less than perfect job on Drawing 3! The drawing shows the valve gear upside down for assembly purposes and hence when the completed assembly is placed into the chassis the right way up, left becomes right. A good idea but this appears to have confused our friend a little as some components are shown assembled on the wrong side of their mating part. For example, the pin 2-25 on the centre gear connecting the 3-15 link to the vertical part of 3-4 should be entered from the opposite side to that shown as the thread and clearance holes are cut in the opposite part. Also, the three bushes 3-7 and their accompanying bolts M1.7-5 are assembled from the opposite side of the link side cheeks 3-1 and 3-6. This is because 3-6 has the thread machined in it and 3-1 has the clearance hole. Assembly as I have described is completely successful and there are no resulting clearance/foul problems.
I would advise that you are very careful to identify all the parts for each set of valve gear prior to starting work, being particularly careful to note that there are two 3-4 assemblies but only one 3-10. I set out all the parts on the drawing to make each of the three sets of gear. Make sure that the set that will be assembled on the left side of the assembly [looking from forward to aft in the upside down configuration] has the 3-10 link. This will become the left side valve gear when the assembly is fitted into the chassis.
Note that the sheaves have been painted at one of the joint flanges. I suggest that the red painted eccentric sheave be mounted on the right side with the white painted sheave in the middle leaving the green on the left.
Another point to pay close attention to is that it is possible to assemble the eccentric sheaves upside down! Please note that the mounting of the sheave to the link side cheeks is made through the lug with the biggest gap between the lug and the joint flange of the two sheave halves. Also when assembling the sheaves to the mating parts 3-1, 3-6 and 3-14 it may be necessary to broach or ream the bushes 3-7 and 3-15 as they should be a push fit on their bolts.
When assembling the lifting links 3-18, the associated pin and bushes 3-17 must be able to slide in the slots of 3-4 and 3-10. A polish with a fine Swiss file is recommended. Note that one of the supports 3-16 [the one between the closest pair of motion] must be bolted to the floor of the frame with M2-2.5 bolts and not M2-4 bolts as are the others. This will allow clearance for the expansion link to swing without fouling the end of the bolts.
Before tightening the set screws and bolts in the 3-17 lifting links make sure that they are all in EXACT alignment. When complete the assembly should be free to Ďreverseí and the parts move nicely without any force but also without any lost motion. Care taken here will ensure that perfect valve events are achieved.
Section 4 assembles the valve gear frame into the chassis and attaches the centre driving wheels and eccentric sheaves and valve links. There is only one drawing error and it is that 4-4 is shown as a mirror image. It all becomes self evident on assembly. Make quite sure that when you make the connection between the two 3-11 and 3-12 links and the 2-12 rockers on their shafts that the rockers are in EXACT alignment across the chassis before locking the set screws. This is imperative.
An interesting and innovative idea adopted on this loco is the fitting of PTFE bearing material into the eccentrics. This is best fitted to the lower sheaves as the eccentrics are assembled. The lower sheave halves are fitted under the matching eccentric and the strip of PTFE is then fed into the gap. To ease the assembly I found it a good plan to rap the strip around a piece of ľĒ bar first as this helps to put a curve into the strip and enables the top of the sheave to be fitted in place without to much fiddling. Be careful to ensure that the strip is fully engaged in the grove as you do up the bolts. Failure to do so will result in seizure. I used a little light machine oil on the sheave surfaces to aid assembly. After rotating the assembly for two or three turns the initial stiffness reduces. By the time you have completed your air test later the assembly will be as sweet as a nut!
Section 5 follows and completes the wheel and motion assembly. The tip here is that when mounting the slide bar brackets make sure to leave the numerous bolts just slack until you are ready to position the crosshead under the centre of the slide bar. Then pinch them up in turn carefully constantly checking as each bolt is tightened to make sure that the crosshead slides full travel without any restriction.
The reverser stand is quite easy; just make sure you have the reversing arm on the weight shaft exactly vertical with the reverser on the footplate in mid position. See the drawings for correct setting.
Section 6 assembles a number of parts temporarily to enable the chassis to be air tested. Because you will have addressed the multi blast pipe issue already this section should prove an easy assembly though you should be careful to oil all bearing surfaces as you go. Setting the valves is a piece of cake because all that is necessary is to centralize the valves in the valve chest. Pour a little steam oil into the valve chest before fitting the cover plates. All other adjustments were made during the valve gear assembly in Section 3. I have yet to assemble one of these kits without it working perfectly the first time air was applied and with only about 10 psi. Wonderful!
Section 7 assembles the boiler and is very easy exercise. I believe it essential before starting on the assembly to use as much insulation as you can on the boiler barrel as the lower part of the boiler is open to fresh air under the casing. There should be just enough insulating material to cover the barrel from the combustion chamber front to the front tube plate. Leave yourself enough to make a disc to fit over the tube plate too for easier and better sealing of the smoke box later. Be careful to check that the dimensions shown for each of the backhead fittings is as shown in the lower left drawing. This ensures you have adequate clearance for all controls and proper alignment of pipes.
Section 8 completes the inner boiler assembly by attaching the smoke box and the assembly of the boiler to the chassis. It is fairly straight forward but great care must be taken to seal the smoke box which is a fiddle. Wangling the top cover, both front 7-24 and back 7-25, to fit whilst easing the superheater into place in the lower smoke box is not easy! It is important to apply sealant to all mating surfaces at this stage to seal all of top and bottom joints and to fit insulating material on the front inner face of the smoke box. Sealing up around the superheater tube in the bottom front of the smoke box should be done carefully to prevent air being drawn in and hence the vacuum being destroyed when running. Hold the completed assembly close to a strong light and look into the hole where the chimney will be fitted to see if you can see any holes. If you can it must be sealed up.
When this is all assembled to your satisfaction the mounting of the boiler can be completed and the oil system fitted. The rest of this section is then straight forward.
Next comes Section 9 and fitting the air smoothed casing. Now you begin to see what a very beautiful engine you are building. There are no difficulties here though fitting the dummy lighting conduit around the smoke box door is a bit of a fiddle. Make sure you cut off the lower ends to allow clearance for the front cover over the oil tank to fit later.
Section 10 assembles the front bogie and the pony truck, the cylinder covers and dummy drain cocks and the burner. No problems here but I do recommend that you stick to Aster advice and assemble the burner with between 30 and 35 wicks in each tube. Make them protrude from the top edge of each tube by 11 mm only as suggested and things will be fine. During this Summer, I have found that from cold the boiler comes up to safety valve blow off in 4 to 5 mins. every time and rough handling of both regulator and blower has failed to blow the burner flame out.
No need for any special attention to be paid to Sections 11 and 12 on building the tender which is straight forward and there are no drawing errors. Just note that the tender plate 11-12 is assembled with the countersunk holes at the front and on top. Assembly of the rear right steps is a fiddle because they have to be assembled over the buffer beam ends whilst also lining up with the brake arm 11-23 on one side. It took several attempts before I did this first time. Also fit the lamps and their conduits to the rear of the tender body BEFORE you put the assembly onto the tender chassis. Itís much easier to bend the tags over then than trying to do it down the back of the water tank!
So at this stage you will now have a beautiful loco with great pulling power and looking and sounding very sweet. What more could you ask for. If you havenít got a kit yet or are still trying to make up your mind, donít delay, get one before they are all sold out! You will enjoy every moment of ownership as I do re-living childhood memories around the Padstow / Wadebridge area!
Although I have described a number of challenges building this kit, they are all relatively easy to overcome. Help is always available from Aster Hobbies (UK) LLP and their team of experienced accredited kit builders, of which I am pleased to be one.
Permission to post this article by Dave Stick on the Southern Steam Trains website has been graciously granted by the author, Dave Stick. Also, we express our thanks to Nick Rudoe and Peter Trinder, Editors, Gauge 1 Model Railway Associationís Newsletter and Journal. Originally published in the G1MRA Newsletter and Journal (Issue 211) Autumn 2006. Also, our gratitude to Andrew Pullen, Aster Hobbies (UK) LLP for facilitating our communication.