He wants to build something that is different and all his own design (despite urgings from several members that he find a production handcycle he likes and then copy shamelessly!) and, he needs it to be much cheaper than the $2,500 or so a decent production one would cost.
Paul (Anybody know his last name?) from Coon Rapids showed his first effort at building a handcycle, based on a wheelchair plus an added arm powered front end. Using a the front fork and drive pieces from a rather cheap donor bike.
This version is nearly unridable. We gave him several suggestions; steeper head angle, more fork rake, 20" front wheel. Several of us offered him used parts. Nothing fancy, but much better than he is using now. MS
Another area for improvement might be the chain management idler ? Dennis volunteered a set of roller blade wheels and Mark said he could turn them down with a center groove for the chain to run in. This kind of idler is generally quite efficient and quiet.