‘A Tillotson unique feature: the end of the headhouse is round’

Neil Lieb Collection

Commentary by Neil A. Lieb, photo from his archive

The concrete work is finished. You see those windows up there? The end of the headhouse is round because it’s hard to lay steel on a square corner. When you’re laying rebar, you have long straight sticks. Corners are hard to do. The is a Tillotson unique feature, as far as I know. It looks good because it matches the contours of the rest of the building. It was functional because the steel of the tank comes in about four pieces, and you lay them and they overlap. It was pretty exacting. You worked on your knees all night, up and down. You got the steel off the rack and you had to get down under neath and run it under all that stuff. And you did that over and over. The day that we were going to put the glass in the windows, those were steel-frame windows. There’s a little metal clip that holds the glass. You put the putty on the outside and you’re all done. The day we were doing that, the wind was blowing so hard, it was breaking the glass as we were put it in. We had to quit because of the danger of flying glass. They bought some different glass that was stronger, double-strength glass. It was just one of those things. All of a sudden, boom, this flying glass comes across the room at you.

Filled with concrete, a nail keg counterbalanced the rooftop crane

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Commentary by Neil A. Lieb, with photo from his archive

See the little cornice atop the tank? Those are forms for the cornice, the overhang. They call them eaves on a house.

The roof was poured before the headhouse went up.

That crane is a concrete-hoisting crane.

The headhouse is quite an operation because you had to hoist the concrete up to the top of the tank. And then they had a deck crane, and you had to hoist it [the concrete] to the top.

Every job I worked on, they used a nail keg that had been filled with concrete as a counterbalance weight. When you went up and down on the cable to go to work, that’s what you stood on—two guys, one foot each. That’s all there was room for.

It didn’t take that long, about fifteen or twenty seconds.

The motor and cable were down on the ground.

The operator had a shed to keep him out of the rain and sun.

 

Summer 1950: All finished with the main house in Alta, Iowa

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Commentary by Neil A. Lieb and photo from his archive

From a telephone interview on July 22, 2014

It’s all done. It looks like they’re putting scaffolding up for painting. The main hoist is on the left. That’s a Georgia buggy hanging on the hoist. The guy that’s standing there is going to push it as soon as it hits the deck. They might be just starting on the headhouse. I can’t figure that scaffolding out. It’s a rigid scaffolding.

Memories of cranes and pushing the Georgia buggy in Alta, Iowa

The formwork is clearly seen at the Alta elevator rises. The catwalk around the bottom was for the concrete finisher, who smoothed and patched the freshly formed surface. Photo from the Neil A. Lieb Archive.

Commentary by Neil A. Lieb, photo from his archive.

From a telephone interview on July 22, 2014

On the upper left-hand corner, there’s a crane. That crane we used to haul the steel up to the top, the rebar, the jackrods. That’s all we used it for. You didn’t tie up the other hoist, you used that one. I think it’s called a jack crane. It was an electrically operated crane. The railroad tracks are on the bottom, that’s the end of a box car in the lower right. That doorway—that’s used when you’re loading grain after the thing was all over with.

When I first started, I pushed the Georgia buggy.  It’s probably the worst job in the world because it’s very physical. They weighed 1000 pounds. At Alta, I progressed to laying steel. All the new hires always got to push the concrete because that was the hardest work. There was a big turnover when you started out because pushing Georgia buggies wasn’t very much fun.

Night and day in 1950, Tillotson’s grain elevator rose in Alta, Iowa

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Commentary by Neil A. Lieb, photos from his archive

From a telephone interview on July 22, 2014:

It was commercial power for the lamps. The only thing that was noisy was the mixer and the hoist. Once you got about 40 feet off the ground, all that anybody heard was people talking to each other. That’s the top of the driveway (seen in the photo), about 16 feet, so they’re about 25 or 30 feet off the ground. On a construction site, there’s lumber all over everywhere. Today they keep track of it very carefully because people steal it. But when we were building these, nobody stole lumber. People in Iowa and the Midwest, they didn’t steal lumber from a construction site like they do out here (California.) See the scaffolding below the forms? A cement finisher finished the concrete as it came out of the forms. That’s all he did, all night long.

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Those cars…I didn’t have a car at Alta. Those shacks were probably, lower right, the office, and the other was where we kept the tools. We built a lot of those things and then we tore them down. Slip-form construction was a major engineering feat. They built concrete grain elevators before slip-forms. They had steel forms they’d fill with concrete.

 

 

 

The gun fired, and continuous action of many processes began in Alta, Iowa

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In this post, Charles J. Tillotson elaborates on Neil A. Lieb’s previous comments, describing the above photo from his archive. The jack rods referred to in the text are the tall, slender steel poles seen throughout the photo.  

They often say, a picture is worth a thousand words and this one fits the bill perfectly. The photo is truly an aid to describing the method of slipform construction that was used in grain elevator construction. Neil mentions the one-handed placement of the jack rod, so I’ll start with that.
 
Slipform construction is made up of many complex disciplines which have to all work together in order to provide the final poured-in-place concrete product.

As mentioned prior to this, the slipping of the formwork used in this type of construction was provided by a series of screw jacks placed apart by an engineered calculation sufficient to lift each jack’s portion of the formwork assembly.

Each screw jack was supported by a wooden, U-shaped yoke, the legs of which were attached to the vertical concrete formwork. Inserted in the top (or horizontal) portion of each yoke was a screw jack (similar to that used in jacking building foundations). A smooth one-inch jack rod was then inserted into the top head of the jack and threaded down through it until stopping at the foundation slab. 

The formwork is clearly seen at the Alta elevator rises. The catwalk around the bottom was for the concrete finisher, who smoothed and patched the freshly formed surface. Photo from the Neil A. Lieb Archive.

The wooden formwork is clearly seen at the Alta elevator rises. The scaffolding around the bottom was for the cement finishers, who smoothed and patched the freshly formed surface. Photo from the Neil A. Lieb Archive. 

A series of horizontal wooden rails at about waist height (looks like a railroad track) were then built directly above the open formwork, the “ties” of which were placed at prescribed intervals and used as a template spacer for inserting the actual vertical reinforcing steel. (See the small, half-inch rebar rods extending vertically out of the open bin forms at each cross tie). The vertical rebar was staggered slightly in an alternating fashion so as to allow the half-inch horizontal rebar to be threaded through the vertical rebar. On the vertical 2x4s that are attached to the exterior side of the formwork and rise above the entire deck assembly, so-called targets placed on their tops were used in leveling the deck in order to provide a final elevator that rose plumb and straight above the foundation.

As the screw jacks were turned (each jack was turned the same amount), the foreman on deck used a leveling instrument and sighted on each target to insure that the formwork was rising true plumb and level. If any of the targets did not align with true level, the portion of the deck out of plumb was corrected by extra turns of the screw jack or jacks as necessary to bring that portion of the deck up level with the rest of the formwork. 

Not shown in the photo is the horizontal rebar that was required to form a steel reinforced grid integrally cast in the concrete to form a reinforced concrete structure. Initially, the horizontal steel was wire-tied in place to the vertical rebar prior to one side of the forms being installed.  This placement occurred only to the height of the wood bin forms. Once the form-lifting began, the horizontal steel was placed by hand by pushing and threading the rebar horizontally through the vertical rebar. Because of the vertical movement of the formwork, close attention was required as to the spacing between horizontal rebar. 

Now, try to imagine: the start gun is fired and the continuous action of the many processes begins, never to stop until the wooden forms and finished structure reaches the prescribed vertical height (some 120 feet) eight days later. Manual labor is involved in each discipline. Personnel changes occur, but each position is filled by a replacement. The gun is fired, cement is mixed and lifted to the deck of the formwork via a Georgia buggy, and the content is dumped into the open form. The pouring of the cement into the formwork is continued in a circular fashion around the entire deck until it reaches a prescribed height in the form. 

The finished elevator. Photo from the Neil A. Lieb Archive.

The finished elevator. Photo from the Neil A. Lieb Archive.

Once the cement is allowed to solidify in the forms on the foundation slab, the jacking operation begins and the formwork starts its vertical lifting and slipping process. The jacks are turned, the cement is poured, the vertical rebar and jackrods are placed and spliced, and all the while the horizontal rebar is positioned at the proper height and spacing. Pour cement, turn jacks, place rebar, check deck level, and on and on through night and day until the construction reaches final height. The most problematic aspect of this system is the placing of the horizontal steel at the correct spacing, the placement of formed openings in the bins, keeping the hoist in operation, mixing the cement, and obtaining enough set time of the cement mixture so that as the finished concrete walls do not fall apart or slough off.     

Also, hanging beneath the formwork structure is the scaffolding for the cement finishers who dutifully serve to patch and smoothly finish the concrete surfaces appearing at the bottom of the vertically slipping formwork. 

 

 

Building a grain elevator required a whole boxcar of lumber

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Commentary by Neil A. Lieb, photos from his archive

From a telephone interview on July 22, 2014:

Decks for the formwork are stacked at upper-right corner of the foundation. Piles of sand and gravel are for concrete. It took one complete boxcar-load of lumber to build most elevators. Everything came by rail in those days.

One thing you did, you re-used all that lumber many, many times. The inside walls of forms were all taken down, taken apart, and the lumber was all reused. We always had a crew of two or three guys cleaning lumber, taking the nails out and cleaning the concrete off of it. Slip-form lumber was seldom reused. By the time you stripped the forms out at the top, that lumber fell 120 feet to a concrete slab and by the time it got there, it was moving. So when it hit, it pretty well disintegrated.

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This is probably the third or fourth day. They went about six inches an hour. The boxes were put in the forms to leave holes where they wanted a hole. On the inside, they’d want a hole to put a spout or something. They’re all pre-made and numbered. The shift foreman’s responsibility is to make sure they’re put in where they’re supposed to be. They have a given height and given location.

You always knew how high you were because in the elevator’s water shaft there was a continuous measuring stick so you knew exactly how high off the ground you were. It was important that these boxes be put in at a certain height.

You also had a continuous ladder. We used to race up and down.

You see the jacks are on the outside. The guys looking over the rails, this is the back side. Way on the other side is where the cement is coming up. You can’t see a hoist.