Picking up the thread on screw jacks unravels some elevator fundamentals

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By Ronald Ahrens

These plans found in the Tillotson Construction Company archives show details of jack screw assembly and formwork, which were essential in the continuous pour method of building elevators, and they contain the key to unlocking the story of how screw jacks came into use.


This key in is in the all-caps lettering “FOWELL SINKS JACK AND FORM.” A Web search reveals that “Fowell” is misspelled. Russell H. Folwell and William R. Sinks were Chicagoans who were granted patent 855452 for Apparatus for Raising Concrete Forms.

The patent application, filed with drawings (seen right) on Feb. 7, 1907, and awarded on June 4, 1907, stated,  “The invention relates to means for erecting concrete structures, and more particularly to apparatus for supporting and raising the forms or molds and the staging employed in building vertical concrete walls.”

The next year, the Canadian Stewart Company Ltd., of Montreal, started building the Grand Trunk Pacific Railway’s 3.5-million-bushel terminal elevator in Thunder Bay, Ont. Folwell was chief design engineer; Sinks supervised the construction. Work was finished in 1910.


Docomomo Canada-Ontario, which is part of Docomomo International, the organization that advocates for the documentation and conservation of buildings, sites, and neighborhoods of the Modern Movement, says this:

“Folwell and Sinks experimented with their lifting device for concrete forms … in 1903-04. By the time the Grand Trunk was constructed, they had perfected their jackscrew lifting device, increased the amount of steel reinforcing and developed mechanical means for delivering the wet concrete to the construction site.”

Additionally: “The device allowed for speed in construction and resulted in smooth wall surfaces.”

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The Official Gazette of the United States Patent Office, Volume 128, characterized the jack screw apparatus in a nine-point description.

Before perfecting the jack screw method, Sinks had been a proponent of tile construction for elevators, according to his grandson John Sinks, a genealogical researcher. He says his grandfather joined James Stewart & Company in 1905. For 108 years, between 1845 and 1953 (the company had come from Canada to the U.S. after the Civil War), Stewart was “one of North America’s most accomplished and longest-standing contractors,” the site of the National Building Museum tells us.  

Meanwhile, Nelson Machine Company, of Waukegan, Ill., appears to have been a manufacturer not only of screw jacks but also of pressing machines and irons.

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The elevator and its Tillotson annex preside in sleepy Dike, Iowa

The old elevator sits beside its wooden predecessor, as it did in 1946

The old elevator sits beside a wooden elevator, as it did in 1946

Story and photos by Kristen Cart

We took a number of elevator detours on our return home from a Nebraska trip, where we delivered our daughter to her summer veterinary camp. During the four-day program presented by Oxbow Animal Health, she learned the inner workings of a cow, and lovingly operated on and sutured a stuffed bunny. Apparently there is no such experience offered to children in Illinois.

The trip home was a meandering route with a number of switchbacks, with elevators built by Tillotson Construction, of Omaha, spaced every few miles. One elevator stop on our sojourn was Dike, Iowa, in the central part of the state. This fascinating site was the last one we saw before the light failed. We were racing a line of weather, and as the sun sank the clouds built and made for very flat light.

DSC_0721It is enlightening to see an elevator complex in person and compare it with an early photograph. The changes wrought in almost seventy years can be surprising, but even more unexpected can be the features that remain the same.

At Dike, you immediately notice a wooden structure behind the main structure. Strangely, it does not appear to be the same elevator that appears in the old photograph. Why would the co-op replace a wooden elevator with another one? The obvious answer would be a fire, but if wood was obsolete, why continue to build with that material?

In my travels, I have rarely come across a wooden elevator that was built before the 1940s and still in use today. Technology rendered the old ones obsolete, and wear and tear made them difficult to operate. Fire also took many of them. Now, wooden elevators built as late as the 1970s are coming down as more valuable uses are found for their wood, and as regulations make them harder to license.

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

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

Dike’s concrete elevator was built in 1946, and it came with an unusual (for Tillotson) headhouse. In the one place where we found a similar example, at St. Francis, Kan., the elevator built by J. H. Tillotson, Contractor, sported a rectilinear headhouse. Though it was replaced much later, early pictures show that the St. Francis headhouse was built in that style.

Both the old Omaha company and its later offshoots preferred curved architecture because it was more economical to build.

So the Dike elevator was a non-typical construction, and we know from its early photo that it started out that way. Since we have no record of it in our Tillotson company records, we have to assume it was built by another company. But the Omaha company led by Reginald Tillotson built the annex.

DSC_0702Tillotson Construction arrived on scene in 1949 to add the annex just three years after the main house was built. In the late 1940s, when elevators were filled just as fast as they could be built, annexes sprung up almost before the concrete cured on the original elevators.

The Dike, Iowa, annex specifications

Capacity per plans (with pack): 200,700 bushels

Capacity per foot of height: 1,859

Reinforced concrete per plans (total): 1,255 cubic yards

Plain concrete (hoppers): 3 cubic yards

Reinforcing steel (including jack rods): 73.56 tons

Average steel per cubic yard of concrete: 117.2 pounds

Steel and reinforced concrete per plans:

Below main slab: None

Main slab: 23,665 pounds steel and 218 cubic yards concrete

Drawform walls: 94,152 pounds steel and 880 cubic yards concrete

Work and drying floor: None

Deep bin bottoms: None

Overhead bin bottoms: 18,156 pounds steel and 56 cubic yards concrete

Bin roof: 4,223 pounds steel and 32 cubic yards concrete

Scale floor: None

Distributor floor: 3,570 pounds steel and 30 cubic yards concrete

Cupola roof: Steel included in above amount, and 21 cubic yards concrete

Misc. (Boot, leg, head, track sink, steps, etc.): 500 pounds steel and 4 cubic yards concrete

Attached driveway (for Dike plans, lower tunnel indicated here): 363 pounds steel and 14 cubic yards concrete

Construction details

Main slab dimensions: 46 1/2′ x 68′

Main slab area (actual outside on ground): 2,955 square feet

Weight reinforced (total) Concrete (4000 pounds per cubic yard) plus steel: 2,583 tons

Weight plain concrete (hoppers 4000 pounds per cubic yard): 6 tons

Weight hopper fill sand (3000 pounds per cubic yard): 25 tons

Weight of grain (60 pounds per bushel): 6,021 tons

Weight of structural steel and machinery: 5 tons

Gross weight loaded: 8,640 tons

Bearing pressure: 2.93 tons per square inch

Main slab thickness: 24″

Main slab steel (size and spacing): 1″ diameter,  5 1/2″ o. c.

Tank steel and bottom–round tanks (size and spacing): 5/8″ diameter, 9″ o. c.

Lineal feet of drawform walls: 400′ (no drive)

Height of drawform walls: 120′

Pit depth below main slab: None

Cupola dimensions (outside width x length x height): 13′ x 93′ x 8′

Pulley centers: None

Number of legs: None

Distributor Floor: None

Track sink: None

Full Basement: Yes

Electrical room: In elevator

Driveway width: None

Dump grate size: None

Columns under tanks: 4 columns 16″ square

Boot Leg and Head: None

Machinery details

Top conveyor: 30″ belt at 500 bushels per minute; 7,800 bushels per hour; 10 horsepower drive; Howell tripper.

Bottom Conveyor: 24″ belt at 600 bushels per minute; 5,800 bushels per hour; 7 1/2 horsepower drive


Also built: Extended driveway on elevator