Years ago, I made a simalar rack from recycled wood, but it was not steady enough. So, time to build a better one, this time in iron.

Step 1: All Parts Preparing

Photo #1 : Major and additional parts
Left : rectangular tube (145x10x5) for vertical strut
Top right : 4 plates (10x8x1) for mounting the wheels on
Middle center : additional end cap (10x5x0,4 thickness not important)
Middle center : additional end cap (5x5x0,4 thickness not important)
Bottom center : square tube (80x5x5) for H-frame
Bottom right : square tube (50x5x5) for H-frame

Photo #2 : The 4 plates for mounting the wheels on. Everey plate represents one step.
Step 1 : marking where the holes need to be drilled.
Step 2 : 3,5 mm diameter drilled holes
Step 3 : 6,5 mm diameter drilled holes
Step 4 : M8 tapped threat

Step 2: Construction of the H-frame

Photo #1: Welding the additional end caps on the two short square tubes.

Photo #2 : Result after welding on and grinding up the additional end caps on the two short square tubes.

Photo #3 : Detailed upside down view after welding and grinding two plates for mounting the wheels on, also notice the connecting square tube on the left side.

Photo #4 : Detailed normal position after welding and grinding two plates for mounting the wheels on, also notice the connecting square tube on the left side.

Photo #5 : Complete view in normal position of the finished H-frame.

Step 3: Vertical Strut

Photo #1 : For the easiest way, first set the H-frame fully level.
Then you could weld on the vertical strut. Here is the strut spotted on, just in the four corners, to the H-frame.
Also notice the two bolts (M10, 10 cm long). It depends on the size of the wheels on what height the bolts need to be fixed. I welded them on 40 and 115 cm.

Photo #2 : Complete overview, after ending the welding and grinding.

Step 4: Painting

For painting, I used two spray cans (400 ml) of acrylic paint (Ral #3020).
Before painting, I taped the for M10 bolts.

Photo #1 : Detailed view after of the lower two bolts after painting. On the left bolt, the tape is already removed.

Photo #2 : Complete overview, after painting.

Step 5: Wheels Mount

Photo #1 : The four (8 cm diameter) wheels I recuperated. Notice that two of them are equipped with a brake.

Photo #2 : The car wheels rack on its side for mounting the wheels on. I needed 16 M8 bolts of 1,5 cm and washers.

Photo #3 : One wheel already mounted.

Photo #4 : All four wheels mounted. Notice the two wheels with brakes below.

Step 6: Finally

Photo #1 : Finished empty car wheels rack.

Photo #2, 3, 4 : Different views of the car wheels rack, equipped with for wheels.

Photo #1 : Detailed view, how the wheels are screwed on.