Sunday, June 5, 2011

Bridge Assembly

When the base is complete the tower construction can begin. I found it handy to cut the pieces and lay them out and drill all the bolt holes (slightly oversized on the horizontal beam for easy fit) prior to welding. The tower and bridge are joined by bolts rather than being welded. This allows disassembly so transporting is easier.

Cutting/Purchase List:

B1. Horizontal Frame Beam. (1), 21” of 3” x 3” Square Tube.
B2L & B2R Vertical Frame Posts (2), 25.5” of 3” x 3” Square Tube.
B3. Pillow Block Bearings, (2), (Purchased) McMaster-Carr Part Number 6244K62; Length 7 9/64”, Shaft duimeter 1.5”, width 2 11/64”.
B4. Base Bearing Plates, (2), 1/4” x 6” x 8”
B5. Bearing Base Plate Hex Bolts, (4), 1/2” x 2.5”, (Purchased)
B6. Bearing Base Plate Hex Nuts, (4), 1/2”, (Purchased)


1. Cut two pieces of 25.5” of 3” x 3” Square Tube for the Vertical Posts (B2).
2. Cut 21” of 3” x 3” Square tube for the Horizontal Beam (B1).
3. Drill the two 1/2” Top/Bottom bolt holes and the 1/2” Front/Back bolt hole.
4. Carefully Square and weld the Vertical Posts (B2R & B2L) to the Bridge Post Base Plates (BF6R and BF6L) on the base frame (or optionally omit the plates and weld directly to the side rails).
5. Weld the Horizontal Beam to the two Upright Beams.
6. Cut two 8” pieces of 1/4” x 5” flat bar for the Bearing Base Plates (B4R & B4L.
7. Gang Drill the two 3/8” bolt holes (in proper position).
8. Attach the Pillow Block Bearings (B3) to the Bearing Base Plates (B4R & L) with Hex bolts (B5) and Hex Nuts (B6).
9. Align the bearings and clamp in place. Insert a temporary shaft and weld the plates to their posts in proper position.

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