Being a weldor and metal fabricator most of my life I have a keen interest in “homemade trikes”. I made my first tadpole trike as I did my first recumbent bicycle. Here are some videos of others who made their own trikes. I will say this … it is very important to “do your homework” before building a trike. It is imperative that you build it correctly so that it is safe to ride. The complex geometry (angles) of the front end must be correct and the rider’s weight distribution is quite important so that the trike handles properly.
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Tadpole Rider 
As much as I admire, and encourage self made tadpole trikes by those who have the appropriate skills in which are necessary to complete the build.. I also hope they take into account the needs in which are necessary to build and ride it safely as well..! I wish you good luck and happy riding upon completion of your trikes…!