Refer to the following link for the home page of all CN Tower construction anniversary collages: well publicized and publicly known aspect of the CN Tower’s construction was the “raising of the restaurant level bracketsâ€. Interviews, photo scanning, photo cleanup, research & writing, Photoshop layout and media communications + relations by RC Lansdale. This collage took many months of preparation and execution, including the interviews of Doug Sumner (the tower's primary engineer, who provided most of the photos seen in this collage), Bryan Hunt (the tower's purchasing manager, who kindly provided the photo of the Topping Off Ceremony - scanning by Jack Hayward) and Graham Bezant (who took the iconic shot of the tower from a bucket hanging from the crane). The middle part of the slip form, used to create the "hexagonal core" remained unchanged from the ground level all the way up to the completed 1464ft Space Deck level. As the slipform became more narrow, the steel and wood would be cut off from the ends and lowered to the ground by crane, such that most of the slipform was gone by the time the legs were completed at the 1464ft level. In total there were about 50 hydraulic jacks used on the main slipform. Special jacks would be used to pull the ends of the slipform structure inward (to make the legs taper) and also to squeeze the concrete forms narrower to make for walls that got narrower as the tower raised up. Note: as a common myth and misconception, the entire shaft was not poured in one continuous run until completed – strikes by workers and weekends would bring the work to a halt. Work was done in rain, sleet and snow, regardless of the weather. No work was done on weekends due to the cost of overtime. There were 3 shifts per day allowing for continuous concrete pouring for 14 months, except for several weeks due to strikes. Upwards of 50 men would work in each shift, both on the slipform and on the ground as support personnel. The lower-level outside and inside decks were where the cured concrete was manually finished off with troweling. The mid-level deck was where the concrete dropped down via a chute into the wooden forms (as seen in the lower-left image above). The slipform had 3 main levels: the top level deck was where the workers carted the concrete via wheel barrels to the holes in the upper desk.
Concrete is lifted from trucks on the ground to the slipform using a fairly simple and effective cable-hoist system, transferred to human transported wheel barrels on the top platform, and then poured into holes located on the top platform which route the concrete down flexible and moveable "funnels" to the second level where workers hand pour the concrete into the wooden forms. The entire slipform structure, and its jacking mechanism, sat on steel rods placed within the curing concrete walls. Construction workers cross-tied rebar into the empty portion of the form, poured concrete into the wooden form, jacked the form upward, and repeated until the entire shaft was completed. The slipform is a wooden form of 2 parallel walls using 4ft high plywood. The slipform was designed, engineered and put into operation by Doug Sumner, P.Eng. The slipform was used to create the concrete shaft from the foundation all the way to the 1464ft level, being jacked up one inch every 5mins. Deck supervisors were Mike Burr, Keith Solomon and Mark Varey.įor the record, the following are the height of the slipform over its upwards travels: Aug 21 - 340ft, Aug 28 - 430ft, Sept 4 - 505ft, Sept 18 - 680ft, Sept 24 - 785ft, Oct 3 - 875ft, Oct 15 - 1002ft, Oct 24 - 1078ft, Nov 14 - 1122ft, Nov 29 - 1168ft, = 1201ft, 1245ft and 1464ft.Īs some trivia for old CN Tower personnel, the name "Susie" (of the wooden pin-up girl bolted to the side of the tower's main crane) came about from a lady called Susan at Sika Chemicals who held an interest with asking questions about the CN Tower. The process had started on J(please refer to the previous pictorial collages).Īmong those on hand at the 1464ft level, of the last remaining portions of the wood & steel slipform, were Sir Norman MacMillan (Chairman & President of CN Rail), Donald Macdonald (Minister of Energy, Mines and Resources), Bud Andrews (CN Tower Project Manager), Malachy Grant (Director of Design and Construction), Andre Jordan (Project Manager), Len Varey (Project Superintendent), Wally Kolodziej (Field Engineer), Maurice Grandmont, George Wilkes (safety boss), Marc Cummins (hoist engineer foreman) and Bob Feltman. CN Tower: Slipform Rising - Jto final completion on February 22 1974įebrumarks the 40th anniversary of the last bucket of concrete poured to complete the CN Tower's main shaft on Februat 7:32am in pea-soup fog after a night of cold and driving rain.
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