Following the Pulborough team’s recent success in 3D printing a new set of copper-style window catches based on reverse engineered CAD models of the original components, we decided to take things one step further…
The 1875 London to Brighton South Coast Railway carriages were fitted with two styles of bespoke copper handles, one with a ‘T-shaped’ section and one with a ‘loop-shaped’ section including the inscribed ‘LB & SCRY’ lettering. Unfortunately, as with the copper catches discussed in the previous blog, only a single pair of handles out of the 8 original sets remained all these years later, leaving 7 of the carriage doors sadly lacking. Also much like the window catches, reproducing these handles in copper would be very expensive and due to the complex shape, would otherwise involve production of a home-scale metal casting forge which does not offer a time or cost-effective solution.
Figure 1: The only remaining original loop and T handles were made from copper and now show significant discolouration due to ageing.
Instead, we opted to follow the same approach as last time, using rulers and callipers to establish the dimensions of the original handles for replication in CAD followed by rendering for visual confirmation and then 3D printing. As you can see, the printing process didn’t always go to plan with the large size of the handles presenting a number of challenges. After a few tweaks were made including coating the print bed in Pritt-stick glue to improve adhesion, installing a secondary fan for cooling the molten extrudate and playing around with print speeds to prevent flinging the part across the room (which, trust us, happened once or twice!), we were able to churn out ‘loop’ handles and ‘T’ handles, with the inscribed lettering included! Following a few hours of sanding and polishing the handles were looking like the real thing.
Figure 2: Design progression from full-scale plastic prototype to copper-filled PLA components… with a few learning curves along the way.
Unlike the window catches, the T handles need to be installed outside the carriage, meaning exposure to the elements, the most concerning of which being rain and sun. If left, these handles would be as brittle as a set of old plastic plant pots left out all summer and would need replacing very frequently! To overcome this, a UV-resistant clear matt spray paint was applied to the T handles to give a waterproof protective coating.
Figure 3: The finished loop and T handles were installed on the carriage doors with a working lock mechanism to allow for full operation.
Once the handles themselves were made, it was time to attach them to the doors. A set of square steel bars were cut to length, turned at the end and tapped with a thread before being slid into the recess printed into the T handles and glued in place using an epoxy resin. To allow for locking and unlocking, a rectangular catch was printed and attached to the steel bar before the final addition of the loop handle and a brass hex nut. As shown in the photographs, these finishing touches really brought the carriage to life, restoring both form and function to this elegant piece of rail history.