Another type of water wheel commonly used at the Harpers Ferry Armory was the tub wheel. At the new Tilt-Hammer & Barrel Welding Shop, erected between 1834-1839, a separate water wheel and gearing was installed for each of the workshop’s eight hammers. Six of the eight wheels were tub wheels. [Learn more about the Harpers Ferry Armory].

Tub wheel illustration

Tub wheels were comprised of wooden paddles or "floats" mortised tightly into the lower end a vertical wheel shaft. They were commonly between 3-6 feet in diameter, with an estimated efficiency of only about 10 percent. As described in The Young Mill-wright & Miller’s Guide, by Oliver Evans, a "tub-mill has a horizontal water-wheel, that is acted upon by the percussion of the water altogether; the shaft is vertical; the water is shot on the upper side of the wheel, in the direction of a tangent with its circumference."

Although not very efficient, they were nonetheless favored by Armory managers – both at Springfield and Harpers Ferry – for their cheapness, simplicity, ease of maintenance, and regularity of motion. Additionally, because of the severe shaking and sudden stresses attending the use of trip hammers, pairing each hammer with a single tub wheel proved operationally superior to providing common power from less durable general purpose line shafting.

The only serious complaint Armory workmen had with the tub wheel, besides its relative lack of power, was the fact that it was "rendered useless by back-water rising only to the top of the floats." In December 1847, Armory Superintendent John Symington reported, for example, that during the previous year "the loss of time to the barrel welders from high water and its consequences, was fifty two days."