The main house of Tillotson Construction’s elevator at Dike, Iowa, built in 1946 (annex, left, 1949), is crowned by a rectilinear headhouse. 

In this post, Charles J. Tillotson explains how his father, Reginald Tillotson, president of Tillotson Construction Company, developed the curved headhouse design.

It would be nice to say that the curved walls were created by Dad for aesthetic reasons and leave it at that.

However, a number of factors actually influenced the design, those being:

1. Re-use of the curved yokes (the horizontal framework supporting the vertical forms used during slip-form construction of the storage bins).
2. Building square corners into concrete slip-form construction proved to be more difficult than curved corners.
3. Placing horizontal reinforcing steel for square corners entailed bending it at a ninety-degree angle and then manhandling it into position, whereas with the curved forms, the horizontal reinforcing steel could be inserted much easier by sliding it into position.

Tillotson’s Aurora, Neb., elevator, built in 1950, has a curved headhouse.

For numbers two and three above, keep in mind that all horizontal reinforcing steel, or rebar, was placed by hand (anywhere from twelve to sixteen inches) during the slip-form process, all while the forms were being slipped vertically by screw jacks.

The horizontal steel had to be placed rather quickly throughout the entire structure, so that the steel bars were approximately in alignment from the beginning of placement throughout the structure and back to the beginning point.

On large projects, steel placement was divided into segments with a team captain in charge of each, and all captains would then synchronize their start times for installing the rebar.

Slip-form construction involves a great deal of detailed labor to carry out specific functions while the forms are being jacked vertically in constant motion. It used to be about five to six inches per hour.

Related articles

• In 1946, Tillotson Construction built a mighty elevator in Kingfisher, Oklahoma (ourgrandfathersgrainelevators.com)
• Elevator work included a quick and painful education in the use of a chain fall (ourgrandfathersgrainelevators.com)