Hi there, I found this forum via a websearch of racing simulators.
I have attached a photo of my own racing sim frame.One pic before adding the monitor frame, the other complete. It is made from scrap aluminium that I found, but could be built from mild steel box.
On it is a driving force GT wheel. The seat I found on the side of the road.
It has Logitech 5.1 surround speakers with the sub screwed underneath the monitor stand at the front. I calculated that steel cost for the frame less the monitor stand would cost about $50 (6m overall length of steel used). The monitor frame uses about another 4 m materials plus MDF sheet.
I will do a sketch of measurements if people would like.
It serves me well for my PC racing games.
Cheers, David.