|
|
9mm`N'gauge Minitrix B.R. `9F' locomotive,
Modifications and Improvements.
NOTE: Click on a photo to load the full size image, You can then return to this page using the Back button on Your browser.
The Minitrix `9F' is a RTR model of B.R's 2-10-0 steam locomotive 92220 Evening Star. It is suitable for use on 9mm gauge trackwork and can be used on British N gauge layouts, But there is a word of caution, The loco will not pass platforms set to the correct distance from the running rails for British N gauge, the gap has to be widened slightly to allow the overscale motion gear on the 9F to pass without fouling the platform edge. The motion gear cannot be moved within the British Ngauge loading gauge as the clearance between motion gear and wheels is already minimal on tight curves, if the motion gear was to be moved in this would limit the route availability of the locomotive due to its inability to traverse the sharp 9in radius curves on most Ngauge continuous run or loopback layouts. (Stoneybridge West being one of them!) The motion gear could be moved within the loading gauge if used only on relatively straight out and back layouts. I had to remove thin slices from platform edging on Stoneybridge to ensure clear passage. The loco is an excellent performer but is visually wrong in many aspects and would really require body replacement to make it completely correct. With a few modifications it can be brought a bit closer to the prototype correcting some of the obvious major differences. The 9F chassis needs modifications to overall length, motion gear mountings and shortening of leading bogie. The adhesion weight inside the boiler needs some material removed to allow the motion gear bracket to be raised. The RTR supplied Minitrix body (based on their existing Britannia body) can be brought closer to scale and aesthetically improved with a few carefull modifications. Of course the body could be used to produce a very nice Britannia by replacing the chassis, but I have opted to make it into a filthy, hard worked 2-10-0 freight locomotive that may have worked the gradients on the S&DJR.
The following modifications are not reccommended as a first loco mod project. I would advise doing some easier mods and detailing on other models before tackling something the size of a 9F. The gear meshing alone has been known to halt 9F overhauls and that's without sawing chunks out of it ;)
Set One
Image 1: The loco body is measured and marked with a sharp scalpel from the back edge of the first boilerband to a point 4.5mm back along the first wrapped boiler barrel section, these marks are carried on down across the footplate and are only lightly scored. The body is then fixed to a piece of wood with two nylon cable ties, this gives a firm hold on the body to ensure it doesn't move when cutting. Warning! Take care not to over tighten the cable ties as the plastic body can be easily damaged, even the thick plastic on Minitrix locos can be warped by applying excessive pressure making the cab sides and footplate spread out sideways. Once happy that the body is held safely, the wooden block complete with marked up loco body is then clamped tightly in the bench vice. It's time for the razor saw, or if You don't have a razor saw, a junior hacksaw with new blade and extra care. I use only hand tools to cut & shape plastic bodies reserving the powered tools for chassis modifications and scratch building of metal models.
Image 2: Two slots are cut in boiler, one just behind the first marking at the back of the first boiler band, the second cut is 4.3mm further along the boiler, these cuts are not made ON the marked lines, but beside the score lines into the scrap section leaving enough between marking and cut to allow the face to be filed, sanded back to the marked line.
Image 3: The cuts continue right through the boiler down to footplate level where they stop without cutting through the footplate!. If it gets slightly chewed up it's not a problem as that section of footplate will be discarded later but it is best to keep the footplate holding the boiler and smokebox sections until they are finished sanded to size. (The measured gap is exactly to size) It is much easier to measure the gap accurately and to ensure the faces that are be joined are parallel. The finished edges must be at exactly 90 deg to the footplate edges with the scrap section of footplate holding the pieces in place whilst the mating faces are worked to size.
Image 4: The scrap section is easily removed with a scalpel giving access to the new footplate faces that need filing back, the filing is quite time consuming on both boiler and footplate but the more time spent getting the cut faces right the easier it is to join the faces accurately.
Image 5: Boiler & Smokebox faces filed back close to markings, will be finished as parallel faces with 1200 grit abrasive paper fixed to a small flat block of metal.
Image 6: Chassis with cylinders horizontal (as per RTR model)
Image 7: Arial view of chassis showing how far out the motion gear is set!. This is the chief cause of selective route/layout availability for this model as it simply won't run on layouts built correctly to British N gauge dimentions and clearances as it will strike the platforms, often with disasterous results. This view also shows the front end (left) of the chassis which has been shortened by 4.3mm to allow clearance for the shortened body and internal adhesion weight.
Image 8: Once the boiler and smokebox joining faces are just right carefully cut away the scrap section of footplate leaving a little bit to file off as done with the boiler. Ensure the footplate faces are sanded back to the measured markings and finished at exactly 90 deg to the footplate edge/side to enable easy joining. Once the sections are joined together, no matter how well they are joined, there will be a tell-tale mark on the footplate from the solvent, I initially tacked it in position with three spots of slow setting cyanoacrylate (superglue thick) then used a liquid plastic glue (liquid Poly) and applied *light* pressure on the mating faces for a few seconds, once dry I added a little extra cyano to the inner edge of the join and under the footplate to ensure strength. A tiny amount of plastic/glue formed a bead along the join, this was removed with the scalpel. If You think it looks bad, don't worry, gaps can be filled and high spots can be sanded to give a good surface which after a quick wash and degrease will be ready for painting.
Chassis & valve gear modifications.
The chassis block was shortened by removing 4.3mm from the front end to allow the shortened body to fit. The motion gear and cylinders are held in place with a bracket that runs across the loco chassis, this is fixed in place on the chassis block with a small screw. The screw is removed and the bracket is raised up from the chassis block by approx 0.8mm, this space can be filled with plastic or any other non-conductive material that is relatively rigid (I used two 0.4mm thick patches cut out of an old rubber gasket). The screw is replaced but is carefully tightened so as not to bend the top motion slide bars which are formed as part of the plastic motion bracket. The cylinders are now be angled upwards in the manner of the prototype 9F, The tops of the cylinders have to be removed where they would foul the body. Everything above the underside of the footplate has to be removed, the plastic the cyclinders are moulded from is best worked carefully with a new sharp scalpel blade and small files, finishing off with wet & dry emery paper. The metal traction weight inside the boiler has to be cut away to shorten it to match the short body and a small vee notch must be cut in the underside of the weight to clear the raised motion gear bracket without fouling on it.
Body and Chassis reunited for test running & detailing.
The body was rubbed down with fine emery paper (1200grit wet & dry) and given an all over coat of a mid tan (reddish brown) with a thin coat of various shades of brown (rust coat) followed by a very thin mix of the brown paints with black added in stages. This allows the paint layer to be built up leaving patches where the rust is starting to show through. There are still several layers of weathering to go on, the next being light coats picking out water leaks with their associated trails of limescale and steam scalding marks on the locomotive.
Handrails ,smoke deflectors and front bufferbeam details will then be added along with some fine pipework made from strands of copper wire. These final detailing items will then be weathered to match the hard worked appearance of the loco. The whole model will then be given a couple more coats of dirt & grime, some ash/dirt on the front bufferbeam & scorch marks on the smokebox door. The finished model will be sealed with a matt varnish topcoat applied with an airbrush.
Going a little bit farther.
If this locomotive proves to be a good runner I will fit it with fibre optic running lamps and a few other fine details before releasing it into traffic.
The full scale prototype.
British Railways. `9F' locomotives.
The Standard class `9' 2-10-0 tender locomotive was introduced in 1954 as a British Railways Standard Freight engine designed to handle heavy mineral workings. The class had two main types with Nos:92000-92019 being built to the original single chimney design, whilst Nos:92030-92250 were fitted with double chimneys, there were also several variants to the `standard' design.
Nos:92020-92029 were variants of the `Standard 9' design fitted with Franco-Crosti double-barrelled boilers, the smaller `economiser' sections were removed leaving a single main boiler barrel smaller in diameter than those fitted to the rest of the `Standard 9' class, .
Nos:92060-92066 and 92097-92099 were fitted with Westinghouse air pumps for working the power-operated doors of the wagons used on iron-ore trains between Tyne docks and Consett iron works.
Nos:92165-92167 of the double chimney variant were also fitted with mechanical stokers.
No:92220 was the last steam locomotive built for British Railways, it left Swindon works on 18th March 1960 named `Evening Star' and was the only member of its class to be fitted with the Swindon design of copper capped chimney, it was also painted in G.W.R. Green with brass and copper fittings, all other locomotives of this class were painted black with standard fittings.
No:92250 was fitted with a Giesl ejector, this is a specially designed blast-pipe in order to reduce coal consumpion. (The Giesl ejector was widely used by many railways outside Britain)
Copyright Notes
