Usage:
Excessive heat input in the spokes and the rim and/or uneven cooling of the hub and rim can cause stress concentrations and will eventually result in cracks in the rim and the weld. These undesirable conditions can be controlled effectively by using the following procedure which supersedes all previously published welding and trimming procedures.
Procedure For Hand Welding
(1) Cut off the material shown in Figure 1 from the stub spokes on the replacement rim so the chamfer is slightly less than one-half the thickness of the spoke.
(2) Cut the spokes at a location about .25" (6.4) less in diameter than the rim. This will leave a separation of .12" (3.0) as shown in Figure 1.
FIGURE 1
(3) Chamfer the side of the spoke adjacent to the rim chamfer at 30° so the resulting fit will be a 60° joint as shown.
(4) Cut a 45° chamfer on the opposite side of the spoke. The spoke chamfers should be located to provide about .12" (3.0) flat as shown.
(5) Remove all slag or other imperfections from the joints and position the hub and rim for welding. Number the spokes clockwise in a sequence of 1, 9, 6, 3, 8, 5, 2, 7 and 4.
NOTE: Before welding be sure the rim and hub are the same temperature (room temperature is suitable) and weld in an area free from drafts. Use dry low hydrogen electrodes conforming to AWS Specification E-7018. Do not use any electrodes exposed to the atmosphere for more than a maximum of 4 hours.
(6) Using .12" (3.0) electrodes with a current setting of 120-145 amperes DC reverse polarity, weld one pass on spokes numbered 1, 2 and 3. Clean the weld and weld one pass on the same spokes with .19" (5.0) electrodes at 230-250 amperes.
(7) Use .12" (3.0) electrodes at 120-145 amperes and weld one pass on spokes 4, 5, 6, 7, 8 and 9 in that order.
(8) Invert the sprocket and clean the weld joint. If the gap is too small to clean, scarf out with Arcair equipment.
(9) Weld spokes 1 through 9 in numerical order using .12" (3.0) electrodes at 120-145 amperes for one pass. Clean and weld 1 through 9 again using .19" (5.0) electrodes at 230-250 amperes.
(10) Continue with .19" (5.0) electrodes, putting one pass at a time on each spoke in numerical order until the weld is flush.
NOTE: To reduce heat concentrations, do not weave the welds or completely fill one spoke at a time.
(11) Invert the sprocket and continue to weld one stringer with .19" (5.0) electrodes at 230-250 amperes on each spoke 4 through 9 in numerical order.
(12) Weld one pass to each of all the spokes in numerical order until each weld is flush.
(13) Turn the sprocket on edge and weld the ends of each joint, rotating the sprocket each time so each joint is in a flat position. This connects the ends of the stringer beads and makes a smoother transition from the spokes to the rim.
(14) Keep the sprocket off the floor in a draft-free area during the cooling period. Although cracks are not likely to occur, any found can be repaired by veeing out and welding with a .19" (5.0) electrode.
Procedure For Automatic Welding
Automatic or semi-automatic welding equipment using the submerged arc method can be utilized for sprocket rim welding if provisions are made for a continuous weld (Figure 2).
FIGURE 2
FIGURE 3
(1) Cut the new rim around through the flange area so a 360° continuous cut is made. Be sure the rim is at room temperature before starting the cut or any welding. Cut the old sprocket in a similar manner (Figure 2), so the hub and spoke portion is .12" (3.0) less in diameter than the trimmed diameter of the new rim. (Figure 3).
(2) Chamfer the hub and spoke portion 45° on each side, leaving a .12" (3.0) flat shoulder as shown in Figure 3. Note that no chamfer is necessary on the rim.
(3) Prepare for welding in the same manner as for hand welding. Use reverse polarity. Use mild steel wire and neutral flux at a current setting of 30 volts and 400 amperes to make a continuous (360°) weld on one side at a speed of 50" to 60" (1270-1525) per minutes.
(4) Invert the sprocket, clean the weld and make a continuous weld at 6" (152) per minute with a current setting of 33 volts and 500 amperes.
(5) Invert the sprocket and finish welding on this side at 6" (152) per minute with the same current setting.
(6) Refer to Step 14 of the Procedure for Hand Welding.