We built this rack for 4 bikes. It's easy to grab any bike and takes the same floor space as 4 bikes if they were all leaning against the wall on top of each other. The difference is, when they're all leaning against the wall you always seem to want the bike at the back!
Its dimensions are 190 cm high 135 cm wide. Feet make it 120 cm deep. The centre of the vertical beams is 30 cm away from the back end of the feet. The diagonal supports that keep it upright are 150 cm long.
It's intended to stand against a wall as shown in the picture. The wheel nearest the ground actually rests against the wall.
Materials: Dimensions of the wood used in the feet, virticals and horizontal beam 35 mm x 70mm. Can't remember what it's called in the hardware store but it's strong stuff. The diagonals are spare slats from a futon base. The bikes are hanging by general purpose plastic-coated screw-in hooks. Shelf brackets hold the basic structure together at the joints but the diagonal supports are the main strength. Wood screws attach the diagonals and shelf brackets.
Improvements:
It's pretty solid and has been in use for years without problems. You could add some extra diagonal bracing supports at the top corners to give it a bit more strength. I was going to do this but it works fine with no problems, so left it as it is.
