You slip it onto a 10mm square wooden rod and stick a 3mm fibreglass or carbon fibre rod in it. Use to pull a string wrapped round a car axleI am developing this as part of my STEM projects for schools. It takes a bit too long to print solid but eventually I hope to have a semi hollow version to use with clients. The big problem with building torsion rod cars is how to securely and safely fix the rod to the car quickly. Its easy enough to fashion a little bracket but this idea just slips on a car created with Jelutong square section timber, built with cardboard corners, wooden axles and MDF wheels. Could print the whole thing but then it would be seriously uneconomic and slow for schools. This design combines traditional craft with 3D printing to speed up and ensure a quality outcome for students... www.ajbooker.co.uk