Research and Links page.
Gear ratiosThis spreadsheet takes the driver diameter, and works out the driver rpm to achieve a target mph for both for the prototype and model. The next input is the top speed you want your model to achieve.
|Green - motor revs below 75% of no load speed||Yellow - motor revs between 75% and 100% of no load speed||Red - motor revs above no load speed, so not feasible.|
Frame spacingThe top part of this spreadsheet is set up for P4; for other gauges you will need to amend the initial wheel tyre back to back measurement accordingly. It works by prompting for the dimensions of all the items I can think of that may exist around the axle between the back of the wheel and the inside of the frame. If any aren't applicable, e.g. shorting strips, then put a zero in that row. The dimensions are then applied to both sides with the resulting figure being the required distance between the frames.
Pipework conversionThe General Arrangement (GA) or Pipe Run drawings that may be available from the NRM or similar, or included in books such as the Wild Swan Locomotive Profile series, include dimensions for much of the pipework specified for the locos as built. Whilst this may not be exactly what the loco actually had in service, the only alternative is measuring a preserved loco, but this may have more modern pipework so can't be relied on either.
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