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Concrete toboggans take the plunge

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The 40th anniversary of the Great Northern Concrete Toboggan Race (GNCTR) featured innovative engineering from some of the top university students in the country.
Concrete toboggans take the plunge

The 40th anniversary of the Great Northern Concrete Toboggan Race (GNCTR) featured innovative engineering from some of the top university students in the country.

The race challenges engineering students to design and create a five-passenger toboggan with concrete running surfaces that can hold its own in a downhill race.

Students compete on a straight track that varies in length year to year — this year’s was 400 feet.

Unloaded, toboggans must weigh 136 kg or less.

They must utilize a roll bar or cage, as well as operable brake and steering systems.

Matt Johnson, the vice-president of communications for the 2014 event said the sleds have to be designed to withstand an 80 km/h roll-out crash.

“We have witnessed teams reaching close to these speeds, though the past two years committees have chosen lighter graded hills,” he said.

The sleds’ frames are typically made of aluminum or steel with a focus on keeping the overall toboggans within the weight limit. 

“Teams use fiberglass, mainly for aesthetics, though this year a team had a boat-shaped sled,” Johnson said.

The technical judging of these sleds takes place prior to the racing and is based on students’ technical presentation and report. 

Teams are encouraged to “push the envelope” with their concrete designs. 

The running surfaces must be constructed entirely of concrete with cementitious materials consisting of a minimum 30 per cent Portland cement.

GNCTR concrete design specifications define the running surface as any part of the toboggan that comes into constant contact with the snow for the duration of the run.

Ski wax is the only permissible coating for the running surface.

The type used and method of application must be indicated in each team’s technical report.

The type of concrete has not historically shown to drastically affect the short-term required performance of the ski, said Johnson. 

“Typically we notice the ski design, including shape, size and profile, to be a much more substantial contributor to the sled performance on the hill,” he said. 

“The ski design and snow conditions play hand in hand as to what design proves to be the most slick on the hill.”

The University of Alberta took home the cup at the race, which was held earlier this year at Western University in London, Ontario.

Steering systems are tested by the Giant Slalom Race, which narrows the track width by half to 10 feet, forcing competitors to weave around gates as they traverse down the hill.

Construction, education and engineering professionals judge the contestants in several categories including fastest race time, best overall design, best team spirit, and best overall.

This year’s corporate awards included one Association of Canadian Industries Recycling Coal Ash’s (CIRCA) Most Effective Use of Fly Ash Award.

Criteria include highest fly ash percentage, ultimate strength at 28 days, low water to cementitious materials ratio, economy and cement efficiency at 28 days.

Ledcor presented a Construction Safety award and Holcim handed out the Sustainable Concrete Toboggan Prize.

The four-day event included opening ceremonies, a competitors’ interaction day, a technical exhibition, race day and closing ceremonies.

Students begin forming teams as early as September, with construction following the design and exploration phases, where various concrete mixes are tested.

The GNCTR originated in 1972 when the Alberta chapter of the American Concrete Institute recognized a need for a Canadianized, winter version of the popular Concrete Canoe Race, which is held annually throughout the U.S.

The ACI’s inaugural event was deemed a failure before it even began, the association cancelling it after citing safety concerns.

Disappointed engineering students from Universities of Alberta and Calgary came together to reorganize and plan a student-run event, which took place in 1975 in Red Deer.

Students at the University of Alberta, University of Calgary, Northern Alberta Institute of Technology (NAIT) and Southern Alberta Institute of Technology (SAIT) were given three chances to race the clock at the 1975 event.

One of four teams sent by SAIT took home the trophy after achieving top running speeds exceeding 50 km/h and a race time of just more than 10 seconds.

The race was held on and off during the 80s and early 90s, but has been held annually since 1993.

The event has remained a student-run competition and is hosted by a different Canadian university each year.

It is open to universities anywhere in the world.

The official 2014 trophies were made from white Portland cement, quartz sand, water and genuine Amethysts, donated by Amethyst Mine Panorama in Thunder Bay, Ontario. This year, 21 teams competed. The 2015 event will be held at University of British Columbia — Okanagan Campus in Kelowna, B.C.

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by Jessica Krippendorf

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