Complete hardware kits are available that include all non-printed parts. Kit includes, spring, bearings, fasteners, electronics, DC motor, etc. Everything needed to build the model except the printed parts. https://www.makerrx.com/collections/projectkits/products/mrx5 This model is fully functioning – belts, pistons and other engine parts move and work just like the real engine, but without the fuel, oil and combustion. Some previous experience printing and assembling complex 3D printed designs is recommended prior to printing this. https://www.youtube.com/watch?v=hRUQLCHZcgg&t=3s