How do the wheels attach on this trike design?
Here are the design drawings. If you go to the section titled Steering Bridge Components you can see were it should attach.
However it does not show the actual way it is attached.
Here is picture from the drawings of the steering bridge:
and here is the finished product:
The wheels are 24 inches with reinforced axels.
Here is an interesting look at wicycle using this type of wheel.
They have an "attacher piece as seen in the kit. One axel, one wheel, and the attacher pieces.