Structurally this trike has held up quite well into its sixth year of use. Building it out of square-tube mild steel was not the lightest way to go, but it certainly has been strong.
The one area that has always been suspect is the bar that connects to the frame and holds the "steering" arms that I hold onto while the front end pivots below me. When we built it the plan was to bolt it to the frame like a handlebar using a BMX-style 4-bolt stem. But the threads in the the bottom part of the stem plate got damaged by the heat, so we said heck with it and welded the plate to the frame and the bar to the plate.
(Yes, the bar has a bend in from when some accidentally dropped the frame right after the weld.)
As you can imagine, this bar sees a lot of flex, and while I did insert a wooden dowel into it as well as put braces where the upright bars meet it, we figured the main joint at the frame might start to fail some day. And it did - last last year I saw a crack developing, and finally this Spring I took it over to Johnson Welding for repair (my friend and co-builder Juergen having gotten too busy with his new business for welding projects).
The guy at Johnson asked me to remove all the paint:
and take out the dowel, then he would try and tap in a thicker steel insert tube, then weld the crack. I decided to also add a pair of braces from the bar back to the frame for some triangulation, which is what should've been done when the trike was built. I fashioned them from the chainstays of a dead 10-speed bike from the scrap pile at the re-Cycles shop:
The welder got those in place, fixed the crack, and was able to add the sleeve. The work is a little rough and the braces are not perfectly centred, but hey it only cost me $40.
I then applied primer and gold paint and it looks fab. And the repair should hold for the rest of the trike's life.