So, while i'm looking for materials I might as well start planning some of the other stuff I need to figure out.
1) Chassis design,
LIGHTWEIGHT AND SIMPLE RECTANGULAR SQUARE BOX SECTION WITH DIAGONAL BRACE WILL WORK - KISS. I'M ASSUMING THE WHOLE RIG WILL BE A FEATHERWEIGHT LIKE ERSKINE'S PLOT ?
2) What is the best way to figure out toe in. Should I make the chassis square and make the toe in out at the wheel or at the point where it attaches to the bike.
DUE TO YOUR ANGLE STEEL CONNECTOR [ VERY GOOD BTW ] AND THE FACT YOU'RE GOING WITH A SWING ARM, IT MAKES SOUND ENGINEERING SENSE TO MAKE ALL THE ADJUSTMENT AT THE WHEEL. MUCH SIMPLER AND EASIER TO ADJUST. KEEP THE SWING ARM AS SHORT AS POSSIBLE - EVEN THOUGH YOU MAY REQUIRE MORE SUSPENSION MOVEMENT THAN WITH A PURE ROAD MACHINE [ I'M ASSUMING THE ODD OFF ROAD EXCURSION ? ]
3) Since I am using a swing arm setup for the wheel/suspension, should I use both shocks or just one.
ONE SHOCK IS GOING TO BE MORE THAN ENOUGH ON SUCH A LIGHWEIGHT OUTFIT, BUT MAYBE FIT A HOOP BRACE AT THE WHEEL SPINDLE END - LIKE A LARGE MUDGUARD MOUNT - IN FACT IT COULD DOUBLE UP FOR JUST THAT.
4) any ideas for a tub(body)? I would like something somewhat enclosed because my 3.5yo son will be riding in it from time to time.
AS FAR AS DESIGN IS CONCERNED - THAT'S VERY SUBJECTIVE - HOWEVER, WITH YOUR MOST PRECIOUS CARGO RIDING IN THE CHAIR, I'D INSTALL SOME KIND OF INNER PROTECTION BY WAY OF A STEEL LOOP ACROSS THE LEG AREA AND ANOTHER BEHIND THE SEAT INCORPORATING A CAR TYPE ROLL BAR. MAYBE EVEN A BELT HARNESS. DOESN'T HAVE TO BE HUMUNGOUS IF IT'S SUITABLY BRACED.
AS YOU'RE LOOKING AT A SWING ARM MOUNT FOR THE CHAIR WHEEL, YOU COULD VERY EASILY INCORPORATE THE ADJUSTMENT FOR THE TOE.