SEmG

Modelling Notes:
Golden Arrow Productions W Class Body Kit
 
by Graham R 'Muz' Muspratt

Almost broadside view of the model
For information on the prototype please visit our W Class section.
 
This kit is designed to fit on a slightly modified Bachmann N class chassis (see notes below). A very basic single-sided A5 instruction leaflet is supplied which gives details, but no diagrams, on fitting the chassis (basic method without other modification) and then suggests that prototype photographs are used to identify other body detailing.

The Kit, as supplied:

  • Cast resin one piece body
  • Cast resin rear bogie
  • Cast resin cab interior (this needs  to be glued in place permanently on the finished model as it also the rear fixing point for the chassis to the body)
  • Cast resin front, rear and middle step
  • Cast white metal buffers
Chassis Differences between W Class and N class:

The N class chassis is fitted by carefully removing the tender dragbox area at the rear of the chassis (ensuring that the two rivets which are part of the current collection systems are not damaged) and shortening the front by a few millimetres.

The motion components and the cylinders on the N class, however, are not quite correct for the W class.

  • The W class outside cylinders have a smaller valve chest and so the sides slope inwards towards the top unlike the vertical arrangement on the N class.
  • The radius bar is fixed at the expansion link end too high on the N class chassis to cope with the slightly lowered running plate on the W class.
  • The bracket to support the pivot of the radius bar, valve stem and combination lever is supported off the frames on the W class and not the cylinder block as per the N class.

To be fair to Golden Arrow the instructions supplied do mention the incorrect shape of the cylinders and suggest either filing to shape or removing the cylinders from the bracket and re fixing at the correct angle. They have obviously not tried the latter as the motion assembly would not then work!

Chassis modifications:

Cylinder Block -
I removed the cylinder and cut off the front and back mouldings of the valve chest flush with the main body of the cylinder block. These were saved and added back to the cylinders later. The cylinder block was then filed to approximately the correct shape. As the block is hollow you are then left with a hole where the valve chest should be. I then filled this with Milliput® and when hard filed to the finished shape.

The front mouldings for the valve chest were then re-affixed. The rear valve chest mouldings were re-affixed once the brackets to support the pivot of the radius bar were removed.

Before re-assembling the valve gear I simply re-drilled the piston rod hole in each cylinder to ensure that no Milliput® impeded the movement of the rod. (Note from Colin Duff: an alternative would be to purchase W class cylinders as spares from South Eastern Finecast, though we have not yet devised instructions of how to do this particular modification.)

Radius Arm -
On the Bachmann N class chassis the radius arm is fixed at the expansion link end by a small screw and interferes with the lower running plate as on the W class. At the combination lever end it has a 90-degree turn downwards. With slight modification to the expansion link end bracket, involving removing a small amount of plastic from the bracket (I used a small drill as an end mill), the radius rods can be fitted on opposite sides with the 90 degree turn now facing upwards and located at the expansion link end. This has the effect of lowering the arm whilst maintaining the correct centres.

Support bracket -
New brackets were made from 1/32" x 1/16" brass bar glued to a 60 thou plasticard mount held by a nut on the top of the chassis located on an extended 8BA bolt replacing the Bachmann chassis screw. This bracket can not be made in one piece brass otherwise it will directly short circuit across each side of the chassis.

The vertical part of the bracket was made with a U shape piece of 10 thou brass. The rear of this was drilled to accept the pin on the back of the combination lever. I soldered these vertical brackets to the horizontal bracket, both of which were drilled to take a short length of 0.5mm brass rod to strengthen the joint and act as a representation of the pivot rod on the outside.

Rear Bogie -
This is simply held by a screw to the underside of the cab interior moulding although I chose to add a small spring and two 8BA washers in between the bogie and the screw fixing point in the underside of the cab interior moulding. It then took a little time on the layout to get the spring tension correct to ensure that the bogie did not't either derail or lift the outer end off the rails sufficiently for the leading wheel not to rotate.

Rear of Bachmann chassis-
With the tender drag box carefully removed (ensuring that the two rivets on the chassis keep-plate which are part of the current collection systems are not damaged) this leaves a gap between the plastic chassis keep plate and the metal chassis block. I filled this gap with a piece of rectangular plastic section cut to shape, and a slot cut to allow for the current collection wires, and then fitted new side plates extending to the rear of the engine over the bogie, shaped to ensure bogie clearance.

 
Left hand side of 
the model
 
Body modifications:
The body that I received had a number of small cast blemishes which required a small out of care and filling at the paint stage and a couple of larger problems such as a slightly warped tank side and the fact that the running plate from the front of the cab, under the tanks up to the turn up by the cylinders was of varying thickness and broken under the tank cut out on one side and was easily damaged when removing the cast temporary strengthening ribs under the tank cut out. (Note from Colin Duff: these faults are not exclusive to the casting Graham Muz bought because several other SEmG members have castings with identical problems.)

The warped tank side was corrected by gently heating in a oven with the tank sides gently clamped between two flat metal bars (my bending bars, in fact), once warm slightly tightening them until I was happy with the flatness of the tank side and then letting it cool gently. Once cold the resin body held its new shape.

To correct the running plate I decided to remove the damaged section completely and replaced it with a length of 30 thou x ╝" brass. This needs to be drilled and filed to allow the expansion link (bearing in mind that this oscillates) and lifting links to protrude through. This once glued into position also adds strength to the base of the tank sides following their straightening in the oven.

I also fitted to the brass running plate turned brass splashers for the front driving wheels that can be seen through the tank cut out.

A small length of ¾" copper tube was glued in place in line with the tank cut outs to represent the underside of the boiler and then the surrounding areas in filled with Milliput« to form the underside of the tanks etc. This also has the added advantage of providing extra weight at the front end.

To add additional weight at the rear I glued lead in the space under the coalbunker.

Brass sprung buffers (Gibson), hand rail knobs and rails (refer to prototype photographs as some had additional grab handles located on the tank sides above the middle set of steps), lamp irons (Bambi staples), brass safety valves (Westwood) and sniffing vales (if correct to your period, not in my case), front, middle and rear cap steps, bunker steps, vacuum and steam heating hoses were added to complete the body.

Note: Numbers (3)1911 to (3)1915 were built at Eastleigh and were right hand drive and originally painted in black with dark green lining until approx. 1931 then unlined black prevailed as per the rest of the class. The remaining ten were built at Ashford and were left hand drive. The main visible external difference between the versions was the pipe running from the cab along the side of the boiler to the smokebox which is only on the drivers side.

Overall:
The cast resin body is not of the highest quality when compared to some other kit manufacturers utilising cast resin components but care taken during assembly and painting will still make for a good model. The kit as designed to fit on a standard Bachmann N class chassis is of course a compromise, which some people I am sure will be more than happy with. The chassis modifications that I made generally took more time to think out, than to do and have resulted in my mind in a nice model.

I do feel that the instructions lacked detail and would rather have had some diagrams showing handrail positions, as well as greater detail on where to cut the chassis, etc. Some background on the prototype would also have been welcome.

General notes on working with cast resin:
Cast resin is by nature quite a soft medium and files / drills quickly and easily with very little effort. I would suggest avoiding self-tapping screws and ensure that you use the correct tapping drill for the thread that you require otherwise threads can be easily stripped. Also avoid over-tightening screws.

Prior to painting clean the resin body thoroughly and I then suggest the use of a plastic primer. I use an aerosol from Halfords.

It is a common practice with white metal or brass kits, once a model body is washed prior to painting gently heat the body, in an oven, to ensure it is totally dry first and also to give a warm surface for the paint to adhere to. I must note here that extreme care must be taken with cast resign bodies with this practice otherwise warping could occur.

 
Right hand side of 
the model

all photographs are copyright.

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This page was created 3 January 2004

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