Coupling Rods.

Modelling the Kerr-Stuart Brazil Class 0-4-2ST locomotive in 16mm scale. - Keith Bucklitch

1. Coupling Rods.



The drawing shows these as a sandwich of bronze or gun-metal, between cheeks of steel. Alternatively, you could simply solder some bronze to silver steel bar for easier construction. I chose to cut some 1 mm x 3 mm mild steel strip, into 8 lengths. Make these slightly oversize and trim the whole boss to size after assembly. Cut some 3 mm silver steel rod to 52 mm long and turn down each end to 2.5 mm diameter for a length of 1 mm. Drill a 2.5 mm hole centrally into four pieces of the steel strips. Silver solder the rod and the bosses together taking care to ensure they lie in the same plane. Mark the position of the crankpin holes and drill and ream to size. (There are a number of ways of ensuring that the holes in the rods match the wheelbase. I prefer to make a jig from some mild steel strip which can be adjusted to the crankpin spacing and locked to length. This can then be aligned on the rods and the holes drilled through this. If two jigs are made you can check the wheels rotate without binding, before you make the rods.)


2. Connecting Rods.



The bosses for these can be made similarly to the coupling rod bosses. The main length of the rod is 2.4 (3/32") silver steel. The fork at the crosshead end is machined from mild steel. Before cutting the main rod, check the travel of the crosshead, place the piston in mid-travel position and take a measurement from the axle centre to the crosshead pivot hole. Cut the rod to length and silver solder the assembly. Drill the crankpin hole, and the hole for the pivot bolt. Make a pivot bolt from some hexagonal mild steel, with an 8 BA thread. Check that it doesn't protrude too far through the crosshead to foul the crank. Before placing on the crankpins, make a spacer from some 4 mm brass about 2 mm long to separate the coupling and connecting rods.



If you have any questions, or comments or find any errors in these notes please contact me by email. Email Keith Bucklitch.

Copyright © 1998, Keith Bucklitch
Last Edited - November 1998