g gauge Ruston Hornby class 16/20hp from around 1934 time very near 7/8 scale model

grabcad

Made in 1933 and beyond, roughly 7/8 scale, this 2-foot gauge locomotive runs on 45 mm track. The prototype is equipped with radio control and sound features. Files are available for both two-slot and three-slot buffers; however, the exhaust was not modeled as the locos had different engines to suit each customer's requirements. The forward and reverse lever were bent after printing flat using a hot iron. The gear change lever was crafted from a steel bar, while the seat spring was made from a brass strip. A meccano chain is used for the chain drive; the motor worm is 1/4 inch in diameter with 16 threads per inch of Whitworth form, cut deep to accommodate the worm wheel gear, utilizing a narrow spur gear. The wheels and axle are sprung between frames before being secured by brass bearing bushes pressed into place from outside the frames using super glue. These bushes are 5 mm in diameter by 7 mm long with a stepped larger diameter on the exterior of the frame for 1.5 mm, bored to suit the axle diameter. The wheels and sprocket were also bored to match the axle diameter. This model was printed in PLA and later sprayed. Printer settings included first layers at 0.2 mm thickness and the rest at 0.1 mm with no support used. A small amount of filler was applied to the fuel tank to restore its round shape, particularly on the bulkhead side. Plans for cab print files will be made available soon; the cab was an optional extra provided for customers who required driver weather protection.