Walking Beam and Connecting Rod

A cast iron walking beam, pivoting on trunnions atop the A-frame, transferred power from the engine to the paddle shaft. The piston rod provided a reciprocating, or up and down, motion to the forward end of the beam. This motion was transferred to the paddle shaft connecting rod on the aft end of the beam, which in turn rotated the cranks on the paddle shaft. This rotary motion caused the paddle wheels to turn.

A fragment of the walking beam remains articulated with the paddle shaft connecting rod and paddle cranks (Figure 16). Apparently, Ross's demolition caused the beam to break and fall aft, pivoting on the crank pin, carrying the connecting rod with it. Now the connecting rod rests horizontally and the walking beam fragment hangs vertically below it. The fragment is 8.7 feet long and broken near a connecting rod pin used to power a boiler feed water pump.

The beam is solid cast iron. It had a long, narrow elliptical shape. Cross sectional views of the walking beam in Figure 16 show a center web with a flange around the circumference and another longitudinally down the center. The flange stiffens and strengthens the central web. A wrought iron band placed around the circumference of the beam provided additional strength and reinforcement. The band has been removed but four U-shaped guides cast into the beam held the band in place. They are paired on opposite sides of the beam.

The beam fragment operated two connecting rods that powered important operating equipment. These rods were centered 7.2 feet apart. The first is indicated by a pin near the broken end of the beam which drove a boiler feed water pump. The connecting rod strap has been dismantled and the rod removed leaving the 2 1/2 inch diameter pin intact.

The second rod is the much larger paddle shaft connecting rod at the end of the walking beam. It attaches to a 5 inch diameter pin on the walking beam. The pin flares on the end to help hold the bearing blocks in place. The journal assembly connecting the rod and the beam is intact on the starboard side but has been taken apart on the port side. This is illustrated in Figure 16. The profile shows the intact assembly while the plan view illustrates both the intact and disassembled sides. Apparently, this was an unsuccessful attempt to disconnect the rod and probably occurred before the beam was broken and fell into the river. The intact journal on the starboard side is a typical 19th-century example (Figure 16). The connecting rod forks to meet the pin extending from each side of the walking beam. A two piece brass bearing, one pair for each side of the beam, fits around the pin and rests on top of the fork. Next, a pin strap fits over the pin and bearing. Slots on each end of the strap align with a slot in the connecting rod below the bearing. The assembly is secured by placing a tapered key and gib through the aligned slots. A locking bolt holds the key in place. An oiling cup, normally found on top of the journal to lubricate the bearing, is missing.

The wrought iron paddle shaft connecting rod lies on the centerline of the ship approximately 3 feet below the river bottom. The six inch diameter rod measures 18 feet 5 inches between the crank pin and the walking beam pin. On the lower end, the rod is still connected to the crank pin with a pin strap. A portion of the strap is broken off but the gib and key remain in place. Damage apparently occurred when the paddle cranks were pulled apart.