KMCE Posted October 26, 2018 Share Posted October 26, 2018 Class 423 Build: Another project on the workbench at the moment. I know the 458 is nearing completion, and the 495 is sitting there awaiting some attention, but a new toy has prompted me to try out a new loco. This time, another DSER tank in GSR guise. Class 423 a 2-4-0T used on the commuter line however they were not highly regarded by the GSR, their comment being "these engines being obsolete in every way. They are slow and high in coal consumption". Not withstanding these comments they ran from 1891 to 1955, so they can't have been all that bad. They also saw service on the Cork - Bandon line, so conceivably could be seen on any Irish layout. Photo credit to Mike_Morant Collection Nice tank engine with good proportions and large driving wheels for their size and proposed use on the commuter network. The difference with this loco is that it has been designed for cutting on the CNC Mill. I mentioned toy above, but this cannot really be considered a toy - the learning curve is quite steep and the software requirements are considerable. 2/3D design Package (AutoCad or similar), Conversion software to generate G-Code (MeshCAM in this instance) and something to drive the servos on the mill (Mach 3 for this mill). Each element has a hefty learning curve, and I have only scratched the surface! Anyway, where we have got to is a drawing kindly supplied by the good people at the IRRS (and they are genuinely a very help group of people), was developed as a CAD drawing. From this drawing parts were extracted into a cutting plan - sample below of the frames. So from CAD drawing to G-Code and through the mill using 0.5mm Brass Sheet we get this. I'm really impressed at how good the CNC cuts and how precise the detail is. Frame spaces were also cut out using the mill which helps to ensure accurate spacing. If you looked at my Class 458 build I go through the installation of hornblocks and setting the axle spacing, so rather than repeating that here I will jump to the rolling chassis point. On this model as a simple three axle loco, the rear axle is fixed for the motor and the two front axles are compensated. Rather than building the complex bar and spacer arrangement as per the 458, I decided to simply bend some 1.5mm tube to the relevant shape to set the level of the chassis while allowing both axles to flex. Much easier to tweak the frame levels this way. Next up, brakes and gearbox. Again brake blocks and hangars were cut using the CNC. I need to tidy up the brake rods at the rear and tie them into a faux crank assembly. Next up, footplate. This was constructed in the same way as the 458. All of this brings us to a rather nice rolling chassis. Gearbox is a High Level Roadrunner +. Levels will need to be set for the motor once I get a boiler in place. Next up was the body, so back to the drawing to create a cut sheet for the CNC. Once again translated to G-Code and we start milling. The brass sheet is stuck down to the MDF with spray adhesive. The tabs between pieces are needed to keep everything in place while cutting. An earlier attempt resulted in smaller bits flying around the workshop - not so good, and impossible to find. Once we are finished the cut parts are separated from the MDF to arrive at this: This leaves the parts in a fret arrangement similar to etches, however the tabs are full thickness so they need to be cut out and filed back to sharpen the edges. That's all for now. Off to the Raheny show tomorrow! 3 2 Quote Link to comment Share on other sites More sharing options...
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