For the spring I use a length of carbon fibre obtained from Crossgates Model Centre [ See TRADERS for the a website ] This comes in various diameters. I used 1.2mm.

There is a fixed point at one end on a sleeper and the other end is attached to the tie bar between the point blades. For this connection, mine is a sliding fit using either a handrail knob or something similar I made. The middle of the spring is connected to the point switch.

In my setup the spring is weighted to the centre as I primarily wanted to prevent damage to the blades if an engine ran through the point with the blades set against the direction of travel. But this does enable the point to be sprung in either direction. If the object is to have it permanently sprung in one direction only, then the point switch could be replaced by another fixed point. (Sorry about using two different meanings for point!).

A certain amount of experimenting took place before deciding on the best length of spring.

If three link couplings are used it’s probably better not to put the spring between the running rails but to one side (as in the first photo) as a coupling left trailing on a coupling hook could get caught.