There is lots of information about building a tadpole trike available online besides what I have written myself. I am not really adding anything new here. Rather I am simply posting this one article with links to all that I have written about the subject before making it a bit easier to find it.
Here is one of them: https://tadpolerider2.wordpress.com/2015/01/30/gotta-do-your-homework/
Here is another one: https://tadpolerider2.wordpress.com/2014/05/11/tadpole-trike-construction-the-science-of-tadpole-trike-steering/
Here another one: https://tadpolerider2.wordpress.com/2014/05/11/home-built-recumbent-trike-detailed-plans-and-construction-steps/
And here are a bunch more postings on my blog about custom built trikes: https://tadpolerider2.wordpress.com/category/homemade-tadpole-trikes/
For anyone wanting to build their own tadpole trike Atomic Zombie has plans they sell to use to make the task smoother sailing. When I built my tadpole trike I did so entirely on my own. I designed my trike and all went well even though it was a learning experience and there were a couple of things I would do differently if I were to build another one. One thing about using plans is that you can know what you are going to end up with before you start and choose what you want from what is offered. As long as you follow the instructions it should all go well and you should not end up with wasted material, etc. which can happen if you aren’t following a set of plans with everything laid out for you including a materials list and cutting instructions.
Do It Yourself Plans … $18 for one set of plans … more than 36 plans available … occasionally they offer specials where you can buy a few sets of plans for a low price (example: 6 for about $30)
Here are some photo examples of what they offer:
the very popular Warrior
the Street Fox with rear suspension
the River electric motorized
and they also offer tandem trike plans