1974 Kabuki Skway lug

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1974 Kabuki Skway lug 1974 Kabuki Skway, aluminum die cast lug cross-section: In the early 1970~s Bridgestone developed a proprietary process for die casting aluminum lugs around tubing. The process did not use welding or brazing. It allowed joining of dissimilar or difficult to join materials such as stainless steel and aluminum alloy. The process reportedly did not affect tube strength, unlike conventionally welded and brazed tubes, as the casting was done below the annealing temperature of the tubing. However due to the low ductility of the lug material, a compression slot could not be cut in the seat lug and the bicycles used an expander bolt to fasten the seatposts to the frame. The process was used on all Kabuki models with plain gauge tubes, including steel frames. The double butted, steel framesets used conventional brazed lugs. The photo shows the extra thick walls and how plugs were placed in the ends of the tubes to prevent the casting media from filling the tubes. Also note how the ends of the tubes are flared to prevent the tubes from withdrawing. The bearing housing also appears to have an internal sleeve. T-Mar