... . posted: 22 Jul 2018 05:54 from: Martin Wynne Hi Andy, Here is a DXF file for you to experiment on. 2_220019_450000001.png 2_220019_460000002.png A bog-standard Left-Hand B-6, and a RH A-4.5 with negative curving and equalized timbering. EM gauge. So far there are only 4 blocks defined in the file: S1L and S1R are identical mirror-image blocks, for ordinary REA S1 chairs. L and R versions allow the replacement blocks to have keys driven in opposite directions: 2_220019_450000000.png L1L and L1R are ditto for L1 bridge chairs. These are longer blocks, to match the wider L1 chairs. The switch chairs are temporarily set to S1 for the stock rails. The switch rails are left empty for now. The datum X,Y location is the intersection of the centre-line of the chair with the rail gauge-face. Z=0 is on the rail top (so all Z dimensions are negative). The seat level is 1.75" scale above the timbers. Here is the ...