Tim--
Thanks for your interest. Here are the instructions:
(Measurements are in inches; use hardwood wherever possible; use deck screws; consider replacing the original
rocker box with maple)
- Starting from the ground up, construct a 33 x 7/8 circular base fitted with castor wheels. On the upper surface draw a perimeter ring whose inner radius is 25½ and outer radius 28½. Important: mark the exact center of the circular base (you will see why, later).
- Next, construct the 33 x 7/8 lower ring having an inside radius of 12½ and an outside radius of 16½ Screw this ring to the circular base.
- Next, construct a 33 x 7/8 upper ring having an inside radius of 13½ and an outside radius of 16½. This ring’s greater inside radius provides for a one-inch “shelf” upon which is laid the azimuth ring (described below). Screw the upper ring to the lower ring.
- Make three 3x3x3 disk support blocks (disks explained below) and equally space them around the perimeter ring on the circular base. These blocks are then screwed to the circular base from below.
- Construct two 22 x 3/8 outer fixed disks (Important: mark the exact center of both disks).
Construct one 21¼ x 3/8
inner fixed disk. (
Mark center!)
Construct one 22 x 1
movable disk (
Mark center!)
Drill a 7/16 hole through the disks centers
Fitting the Bicycle Chain
Buy a
bicycle chain long enough (66.75713 inches to be exact) to fit
tightly (not snugly) around the perimeter of the
inner fixed disk. If you come up short you can sand or trim the perimeter (be accurate!). Sandwich the
inner fixed disk (replete with chain) between the two
outer fixed disks, insert a 7/16 three-inch threadless bolt through the centers, and screw the three disks to each other (screw holes must be at least 1½ inches from edge of the
outer fixed disks so as not to interfere with the
furniture sliders (described below).
Attaching Furniture Sliders
Buy a pack of ¾ x 3/16
furniture sliders and screw at least six of them near the perimeter of one of the
outer fixed disks.
Joining the Rocker Box to the movable disk
Place the
movable disk on a flat surface and shim it until it is
perfectly level. Remove the original three-piece
rocker box from its base and place it on the
movable disk. Take a rigid rod and lay it across the
rocker box’s semi-circular axle cutouts. Measure the distance between the inside faces of the
rocker box’s side boards. Locate the middle point, drop a plumb line and move the
rocker box until the plumb lies precisely over the hole in the
movable disk. Drill the
rocker box to the
movable disk.
The Azimuth Drive Shaft & Sprocket
Place the
circular base (along with its outer & inner
fixed disks) on a flat surface. Place the moveable disk (along with its attached rocker box) on the
circular base and insert the three-inch bolt.
Weld or hammer jam a 2½" bicycle
sprocket onto a 24 x ½ steel rod. Slide the wooden
lower rod support down the rod. Slide the ¾" locking pulley-wheel down the rod. Slide the wooden
upper rod support down the rod. Screw the
lower rod support to the
left sideboard. Engage the sprocket teeth with the imbedded bicycle chain. Make vertical adjustments using the locking pulley wheel. Finally, screw the
upper rod support to the
sideboard.
The Elevation Drive Shaft
The support framework for the drive shaft is 1½ x ¾ maple: Cut two 27" pieces which are then attached to the sideboards using bolts and wing nuts, and cut one 14½" cross-piece that freely rotates between the two (see photo #5). Drill a 3/8" hole in the middle of the cross-piece.
Obtain a 3/8" x 30" threaded rod, a 3/8" threaded knob, and a swivel bracket (see photo #6). (I’ll get the nomenclature for that bracket and its related parts ASAP.)
Locate a balance point for the swivel bracket (mine is located 12" from the lower end of the tube) and firmly bolt it to the tube.
Slide the rod down thru the cross piece and thread it into the swivel bracket. Drill a small hole thru the rod where it joins the swivel bracket and insert a pin (to keep the rod from un-threading during use). Drop a nylon washer down the rod followed by the threaded knob. You will probably need to trim the 3/8" rod by a few inches.
Balance: You will need a bungee cord long enough to reach from a wing nut on the left side board, pass over the tube, and connect to a wing nut on the other side.