Story and photos by Kristen Cart
The Tillotson elevator at Pocahontas, Iowa, first came to our attention as the site of a tragic accident where a young construction worker lost his life. Larry Ryan fell to his death because he tripped while crossing from the elevator to the annex on a makeshift wooden walkway, according to fellow workers. He wore brand new work boots and some speculated that they contributed to the accident. The young hoist operator was twenty years old when he fell 130 feet to his death from the top of the nearly completed annex in 1954.
I finally had the opportunity to see the site for myself this past summer. We took a wide detour north of our regular route from Nebraska to Illinois–it added a good four hours driving time, not counting the stops. My young cheering section (the kids) were not cheering about the extra road time.
Upon our arrival in Pocahontas, a town along Lizard Creek in north central Iowa miles away from any major state thoroughfares, we immediately noticed the Tillotson elevator and its trademark rounded headhouse. The annex stood beside the original elevator, rising higher (by 10 feet) than its 120 foot companion, and gleaming with clean whitewashed concrete. It showed no sign of its sorrowful beginnings.
Later additions, including an elevator with headhouse, a flat storage shed, old steel hoppers, and modern steel bins with external legs, surrounded the two concrete structures.
The Tillotson elevator and annex were flanked on one side by a quiet street with an old church and ancient maple trees. The bustle of grain trucks was absent on the Sunday afternoon of our visit, and the co-op office was closed. Only the elevator exhaust fans pierced the silence.
We circled the complex, taking a number of photographic views, before going on our way.
We have the specifications for both the 1949 elevator and its 1954 annex. The annex construction record is detailed here.
The Pocahontas annex was built with six 18-foot diameter, 10-foot spread by 130-foot high bins; with a basement; the bins were flat bottomed, built with 30-inch belt conveyors and tripper.
Planned capacity (with pack) was 222,440 bushels; translating to 1,863 bushels of capacity per foot of height. The total reinforced concrete, per plans, was 1,366 cubic yards. Plain concrete for hoppers, per plans, was 9.5 cubic yards, and reinforcing steel used, including jack rods, was 69.59 tons.
The design specified the average quantity of reinforcing steel used for the whole annex, which was 101.89 pounds per cubic yard of concrete. Actual planned amounts were then itemized for various components of the structure:
Main slab: 27,017 lbs. steel/219 c.y. concrete
Drawform walls: 30,708 lbs. steel/990 c.y. concrete
Overhead bin bottoms: 9,957 lbs. steel/70.5 c.y. concrete
Bin roof and extension roofs: 6,740 lbs. steel/44 c.y. concrete
Cupola walls: 3,747 lbs. steel/33 c.y. concrete
Cupola roof: included in walls
Bridge/Tunnel: 1,020 lbs. steel/9.5 c.y. concrete
Dimensions and weight of the annex and its components were laid out also. The main slab was 52′ x 60′, for an actual outside area on the ground of 2,946 square feet.
The weight of reinforced concrete, calculated at 4,000 pounds per cubic yard of concrete plus steel, was 2,801 tons. The plain concrete was also calculated at 4,000 pounds per cubic yard and totaled 19 tons. The weight of the hopper fill sand was 177 tons.
When the weight of grain was added to the specifications, at 60 pounds per bushel (for Pocahontas, the grain load would total 6,660 tons), the planned gross weight of the annex could be predicted. Twelve tons of steel and machinery were added to the total, for a planned gross weight, loaded, of 9,669 tons.
From these figures, bearing pressure was calculated to be 3.28 tons per square foot.
To handle all of that pressure, the main slab was made 24 inches thick. It was built with #8 steel, placed at 6″ c.c. spacing. Tank steel and bottoms (for round tanks) used #4 steel at 9″ c.c. spacing.
The drawform walls, with extension, measured 411 linear feet, and 130 feet in height. Cupola dimensions were 16′ x 56′ x 8 1/3′.
Since this was an annex, distribution of grain was accomplished through the main elevator leg and thence by belt conveyors and a tripper. Many of the items expected for elevator specifications were absent for an annex. For machinery, the annex had top and bottom belts, rated at 600’/min or 3,000 bushels per hour. 7 1/2 horsepower drives were used for a total load rate of 9,000 bushels per hour.
Loading rates are key for grain storage operations, since they determine how quickly trucks or rail cars can unload and be on their way. Slow elevators become obsolete. The Pocahontas operation was at the leading edge of technology with its shiny new 1954 annex, and to this day it provides quick, efficient service.