This takes time and guesswork. Measure things like your legs, a bit of giggling.
Made up a 2" pine mock up and chopped up some junk bikes... MTB for the rear - and a kids's bike with 18" wheel for the front.
Step 3: Steel yourself
Actually Julian did this for me. I'm a bit wooden. He copied my pine pattern behind in 2" square section steel. V solid. the clamps are trying to guess the chain runs with Juriaan Bol's chain runners (www.dutchspeedbikes.com) he does recumbent bits.
Step 4: Back up
This has to be very strong.
Step 5: Full frontal nerdity
I just guessed rake angle - the human eye is a wonderful thing. In the end I can almost ride it no hands...
Step 6: Chained up
Yep, it works. Two and half old chains....
Step 7: Screwed
Together, so I can take into two for easy transport.
Step 8: And screwd again
No huge precision required. It just has to work, be strong and look pretty on top.
Step 9: Three point linkage
So the thing doesn't wobble... and goes together / comes apart quick.
Step 10: Skid row
Castors are a very very bad idea. But the leather takes a scraping - ask any biker. So here's a bit of scrap oak. The fuel line is a tilt device - it works to some extent but by the time I hear it I'm probably wobbling in a tight corner and in trouble enough.
Step 11: Skid stops
Can pull them out or replace..
Step 12: Strong stuff
The 18" was replaced by 20" front end with v-pull brakes. This improves ride height and helps pull up. You have to pay for real comfort, and this saddle is sooooooh heavy.
Step 13: This is it
Armchair or bike - you decide.
Step 14: Does my bum look big in this?
41" inches wide. For less than a Double-sprung Gel Comfort saddle.