1978 was a big year, with three rides capturing records for the world’s tallest roller coaster.
In 1978, Arrow Development opened two large roller coaster projects; the first was the Loch Ness Monster at Busch Gardens Williamsburg (Williamsburg, VA). The ride had the largest drop at 114.2 feet (at a record breaking 55° for a full circuit steel coaster) for a few days until Gemini at Cedar Point opened; the lift structure made it the world’s tallest full circuit roller coaster: 130 feet tall. The ride signature element is the incredible interlocking loops, the last one of its kind today. The ride opened with the rare possibility of having trains crossing each other in the Interlocking Loops, which was possible when ride operators dispatched trains as soon as they were able to. Alas, throughout the years, the ride was reprogrammed so that the first lift motor runs slower than before, forever removing interlocking trains’ visual. The ride initially had a lighted-up Loch Ness Monster mural in the cave portion of the attraction, but this was removed in the 1990’s.
The train dropping down into the second drop, which has speed controlling brakes to adjust the forces in the vertical loop. 
The train about to enter the first vertical loop. 
Approaching the first drop. 
A look at the ride from one of the park’s bridge.
In 2018 for its 40th anniversary, the park had S&S-Sansei (who purchased Arrow in 2002 and now support their rides) build new classic cars for the Loch Ness Monster, preserving the traditional appearance of the attraction. In addition, lights and fog returned to the cave.
Gemini at Cedar Point (Sandusky, OH) opened in June 1978 and uses a mine train style track from Arrow Development mounted on a large wooden structure. The park claimed it was the world’s tallest roller coaster when it opened, but at 125.3 feet tall, it was shorter than the Loch Ness Monster. It did have the largest drop, at 118 feet, but the Screamin’ Eagle at Six Flags St. Louis remained the fastest roller coaster at 62 mph.
A look at the station of Gemini. The ride initially had two entrances to feed enough guests for its massive 3000 + riders capacity per hour. 
The cars are a mix of old and new, as Arrow designed new individual lap bars for riders while reusing the original Runaway Mine Train chassis and track. 
The trains leaving the station. 
http://www.negative-g.com provided us with this photo of the first drop.
Magic Mountain (Valencia, CA) hired the International Amusement Device (IAD) Inc to build the world’s largest wooden roller coaster for that category of record. At that point, IAD was the new name of the famed National Amusement Device (NAD) Inc. that had built notably La Montana Rusa at La Feria de Chapultepec in Mexico City. In 1973, Aurel Vaszin, owner of NAD until that point, sold the company to Bill Roose, son of George Roose, who happened to be one of Cedar Point owners (Sandusky, OH) at that time. Aurel Vaszin remained a consultant, but the company transitioned into park design and brokering attractions, only designing one roller coaster between 1973 and 1978, the High Roller at Valleyfair (Shakopee, MN) in 1976. IAD designed the ride and provided the trains and components like the lift and brakes. The Rauenhorst Construction Company (now known as the Opus Group or Opus Development) was the park developer, and they constructed most of the park themselves, including the High Roller.
Model of Colossus that was on display at the park.
At that point, IAD was not in a good position to design roller coasters, especially such a massive attraction. Colossus was to be 125 feet tall with a massive 115 feet curved drop to the ground. To that end, IAD acted as a broker for the ride, hiring Bernard Brothers Construction for the construction, Continental Consultants for the mechanical systems, and Lorenz & Williams for the structural engineering and electronic systems. La Montana Rusa in Mexico City was studied and was the base of the new bigger design: they went to a standard dual-track layout, not featuring the Moebius loop feature of the Mexican roller coaster.
High Roller at Valleyfair. 
High Roller still use the original NAD/IAD braking system.
www.negative-g.com provided us with those two pictures of Valleyfair! High Roller.
The ride opened on June 29th, 1978, and the experience was incredible. It featured a massive 105 feet tall, straight second drop, the first roller coaster to feature two drops at least 100 feet tall. Unfortunately, the design was too extreme. In December 1978, a rider was ejected on the small hill after the second drop due to the rider individual lap bar not securing the person correctly and the out of control forces. William H. Cobb, who designed roller coasters and was noted for his understanding of forces on roller coasters, was brought in to analyze Colossus and provide solutions to its issues.
The ride initial profile. 
The original 5 car trains going down the first drops. 
After replacement, the original trains were stored in the park boneyard area. 
An IAD/NAD train leaving the station. 
It was noted that the ride was built solidly and made to withstand its forces and the many earthquakes in the area. On the other hand, the hill mentioned above and a few other segments had negative G forces outside of the accepted range. The IAD trains were not adapted to the ride, and the braking system could not effectively control train speed. To implement changes to those issues, the ride closed for ten months and reopened with the following fixes:
- New trains from the Philadelphia Toboggan Company. Equipped with handrail lap bars, seat dividers, seatbelts, and headrests,
- Long sections of skid friction brakes replaced original pinch brakes that grabbed fins under the cars.
- Reprofile the hills, so they don’t provide excessive forces.
Skid friction brakes, still used on Monstre. 
The replacement cars from Philadelphia Toboggan Company had this configuration, seen here on the Yankee Cannonball at Canobie Lake Park.
The changes worked, and the ride reopened in 1980. In 1988, to minimize the forces on the track and implement individual adjustable restraints, new trains from D.H. Morgan were purchased. Consisting of six four-passenger cars, the new trains were lightweight, and at the same time, the park removed the 1980 skid brakes and replaced them with robust new pneumatic pinch brakes. In 1991, the camelback hills next to the parking lot were covered in new track, a gentle downward slope equipped with brakes. During the Halloween season, the park took trains from the Psyclone roller coaster and ran them backward on one track of the attraction. The Bolliger & Mabillard trains had headrests and were more adapted to running backward than the trailered Morgan cars.
The ride’s last profile before it was changed dramatically. 
The first and last turnaround of the ride, with Goliath looming above.
Throughout the years, the park kept changing the ride, changing a lot of the wooden track bed to i-beam steel track, a precursor to what happened in 2014 to the attraction. On August 16th, 2014, Six Flags closed the original Colossus. They had the Rocky Mountain Construction (RMC) company drastically change it, turning it into a Moebius loop roller coaster with a single station. The lift was rebuilt a few feet shorter (121 feet tall) to reflect its shorter track: 4990 feet for both tracks, compared to 4325 feet for each track before. Twisted Colossus opened with three trains, with the park purchasing a fourth later so it can always run three with one train in annual maintenance.
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