Take one of the remaining C-Channels and place a 7" 3/8 axle bolt through each of the outer most axle holes and then center dropped hole.
Place a 1.86" spacer on each of the axle bolts.
Place one of the wheel assemblies on each of the axle bolts, sprocket side away from the C-Channels. Single sprocket wheels should be on the outer axles, while the center axles should hold a double sprocket wheel.
Place one 2.50" spacer on each of the axle bolts.
Take a Corner Connect and attach them in the end holes of the C-Channels.
(Note: ensure the end of the Corner Connects with 3 holes are connected to the full length C-Channels.)
Slide each of these rails (C-Channel with axles, wheels and Corner Connects), into the previously assembled frame (from Part 1), with the axles going through their opposite holes.
(Note: ensure the all of the C-Channel's center holes are downwards while assembling)
Attach the Corner Connects into the 2nd and 3rd holes of the cut C-Channels.
Apply 3/8-16 nylock nuts to the ends of all of the axle bolts. Tighten them enough for the wheels to spin freely, with little to no lateral movement of the axle.