Chapter Eight - The Rear Triangle

FIGURE 8-19: Reducing the diameter of the seat stay plug with a file in a milling machine collet.

VFIGURE 8-20: Measuring how much to cut the seat stays

 The next part can be tricky. Measure the distance from where the tips of the seat stay plugs presently are to where you would like them to be. That amount is how much you want to cut off the seat stays. If in doubt, cut less than necessary; it is always easy to cut more later, but adding material back again is much harder. Figure 8-20 shows how this measurement is made. After the necessary amount has been cut off the tops of the seat stays, square the ends of the seat stays with a flat file and then use the deburring tool to remove the burr from the inside of the top of the seat stays. Do not deburr the outside; that will only leave a groove that will need filling during brazing. Clean the seat stays and seat stay plugs for silver brazing and flux all of the mating pieces generously for silver brazing. Reassemble the seat stays and seat stay plugs onto the dropout tabs and rest them against the seat stay rest. IMPORTANT: The seat stay plugs will be brazed to the seat stays now. Nothing else will be brazed at this time. Do not braze the seat stay plugs to the seat lug at this time! Do not braze the seat stays to the dropouts at this time! Figure 8-21 shows the assembled pieces ready for brazing. Notice that there is no flux between the seat stay plugs and the seat lug. It is important at this time to make sure the plugs are in the correct rotation to fit against the lug. Sight in the plugs from at least two angles to make sure they appear to match each other's rotation.

 The next part can be tricky. Measure the distance from where the tips of the seat stay plugs presently are to where you would like them to be. That amount is how much you want to cut off the seat stays. If in doubt, cut less than necessary; it is always easy to cut more later, but adding material back again is much harder. Figure 8-20 shows how this measurement is made. After the necessary amount has been cut off the tops of the seat stays, square the ends of the seat stays with a flat file and then use the deburring tool to remove the burr from the inside of the top of the seat stays. Do not deburr the outside; that will only leave a groove that will need filling during brazing. Clean the seat stays and seat stay plugs for silver brazing and flux all of the mating pieces generously for silver brazing. Reassemble the seat stays and seat stay plugs onto the dropout tabs and rest them against the seat stay rest. IMPORTANT: The seat stay plugs will be brazed to the seat stays now. Nothing else will be brazed at this time. Do not braze the seat stay plugs to the seat lug at this time! Do not braze the seat stays to the dropouts at this time! Figure 8-21 shows the assembled pieces ready for brazing. Notice that there is no flux between the seat stay plugs and the seat lug. It is important at this time to make sure the plugs are in the correct rotation to fit against the lug. Sight in the plugs from at least two angles to make sure they appear to match each other's rotation.

FIGURE 8-21: Seat stays and plugs ready for brazing

FIGURE 8-22: Filing stay/plug joints

Silver braze the seat stay plugs to the seat stays. It would be easiest to tack them while they are assembled onto the back of the frame, then remove them and finish up in the vise. After the pieces have cooled to room temperature, soak off the flux in hot water. There will, more than likely, be a seam around the circumference of the seat stays where they meet the seat stay plugs. This must be filed away with a fine flat file (A 6" Nicholson will do the trick.) Figure 8-22 shows this being done.

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