Step 5: The Frame part B
We now need to see how far down to mount the drive axle to make the frame level. So raise the rear of the frame up until the top of the frame is level with the ground (use your level). Now measure the distance from the top-rear of the frame to the ground, this is the frame height.
Now we need to take into account the height that the wheels will raise the axle off the ground. So measure the distance from the center of the rear drive wheel to the ground (the wheel's radius). Subtract the wheel radius from the frame height and we will have the correct distance from the top of the frame to the drive axle, which we will call the frame-riser height (we need to cut these pieces next). They are going to connect the rear of the frame down to the axle which the wheels will be mounted on.
6. We are going to add 2" to the frame-riser measurement (so we have a little to work with) and cut the 2 frame risers (mine were about 10-12" long).
7. Now drill (2) 5/8" holes, 1 at the bottom of each frame riser (about 1" from the bottom), this is where the drive axle will go through.
8. Drill 2 holes at the top and bolt the frame risers to the rear of the main-rectangular frame with the frame-risers pointed down.
9. Now feed the threaded-rod through the bottom holes of the frame risers and use 4 nuts to secure the frame risers to the drive axle (1 nut on each side of each frame riser, tightened down).
10. put the rear wheels on the axle and use 1 more nut on each wheel to secure them to the axle (these wheels have built in bearings). The sprockets should face inward toward the frame.
Now we should have a frame that stands on it's own with 4 wheels. However, the rear axle is not completely secure yet. We will need to add 2 braces from the bottom of the frame risers (near the axle) to the main part of the frame in order to keep the frame risers positioned properly. These braces can be flat steel and do not need to be very thick, they are just keeping the frame risers from moving.
Measure about 2" above each axle and drill a hole, then measure how far down that hole is from the top-rear of the frame and measure the same distance from the rear of the frame toward the front. Drill another hole on each side at this measurement. The support braces will need to be measured to be bolted in through these holes on each side (see pictures). The placement of the support braces is less important, meaning you can bolt them in wherever is convenient, as long as they are present.