Design process and current status as at May 2020

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All contents (including photos and drawings) - ©  2020 Derek Mackenzie

Design process and current status as at May 2020


 

For those wanting to know more, the following may be of interest.


Designs always start off with works GA drawings (and more) wherever possible.

The works drawings are checked off against my own photo surveys and photos of the locos in service.

       Caveats - the works drawings are not always right and neither are all the preserved locos.

General arrangement drawings are then done in TurboCAD at full size. This is by far the most time consuming process as everything needs to be continually checked.

The next stage is re-scaling the GA drawings to the model scale. Easy!

From there all the sheet metal parts are derived for the etches.

3D solid models are created in Solidworks (used to be Rhino, but Solidworks is much easier) for all cast and non-sheet parts.

From 2014 all parts have then been written out as dxf or dwg (AutoCAD exchange formats) file for import into Solidworks.

The parts then have to be built in 3D in Solidworks. This enables me to check the fit and operation of parts.

From there the parts are built into assemblies and Solidworks exploded drawings are produced.

The parts all have assembly instructions added so they appear on the exploded drawings.

The exploded drawings are for each assembly level and I try to keep these small enough so they generally fit on 2 (preferably 1) pages.

The exploded drawings are then saved as pdfs and joined together into assembly instructions separately for loco, tender and common parts.

When all seems OK I create the etch layouts to send off to the etchers.

I now have a 3D printer (high resolution SLA resin printer) and print my own masters for all the castings. These are sent off to my tame caster (very good).

DXF files for parts to be 2D (or 2.5D) machined on my CNC lathe and mill are then imported into Dolphin Partmaster and the cnc parts and files created.

The prototype CNC files are then passed to the CNC controller PC and machined using LinuxCNC

I then solder up the silver soldered parts.

The prototype model is then assembled and tested once the etched sheets have arrived

 

The introduction of Solidworks into the process in 2014 came with an enormous learning curve and quadrupled the number of files created.

As an example - the LSWR T9 (including tender) created 1550 files (and up to 670 standard parts, though not all of those are used).

The tender accounts for about 1/4 of that. Many of the standard parts are driven by Excel tables which means that 1 file can create many variations.

This is approximately 4 times the number of files per loco in pre Solidworks days.

 

Ignoring the previous 2 generations of locos that I no longer make - the current position is:-

    3 new locos ready for production before July 2020 - subject to my etchers being back at work.

    1 new loco ready later in 2020 (ditto).

     19 locos with the TurboCAD GA drawings done, so about to go into the 3D modelling cycle.

     20 locos partially started in TurboCAD - I have the works drawings and my own photo surveys done for these.

     7 locos waiting for me to do photo surveys of which 5 still need the works GA drawings.

     1 breakdown crane about 80% complete in the TurboCAD cycle.

      8 LSWR wagons fully drawn up in TurboCAD including a very complex (intended to be fully working) horse box

      1 SR/RCH wagon chassis etched

      about 24 carriages have completed the TurboCAD cycle (plus the ones already etched in 10mm scale for earlier locos)

      I have lost count of the other carriages that I have suitable drawings for - some of these still need photo surveys done.