NCL Free At Sea

Interview With Colossus’ Structural Engineer, Tim McCrate

By on 08/03/2014

Not that long ago, a reader of this site contacted me and said she was friends with the guy who did the structural design work for the Colossus roller coaster at Magic Mountain back in the 70’s, and would I like to meet him? Well that was a no brainer, of course I would! She put us in touch with each other and I ended up interviewing him over the phone. We talked about how it all started, what the challenges were, and how/why the ride has changed over time.

I have a full ride profile for Colossus, so I’ll try not to duplicate too much of that information here. Magic Mountain (it wasn’t yet a Six Flags park) contracted with the International Amusement Device (IAD) company back in 1976, just after the opening of The Great American Revolution roller coaster, to build their next big roller coaster, Colossus. IAD then hired an engineer from the recently downsized National Cash Register (NCR) to pull the entire project together. Some of the sub-contractors they hired included Bernards Brothers Construction to build the structure, Continental Consultants for all of the mechanical systems, and Lorenz & Williams to handle the structural engineering and electronic systems. Timothy “Tim” McCrate was the structural engineer at Lorenz & Williams who was assigned the Magic Mountain project. He currently resides in Dayton, OH and was gracious enough to grant me this interview.

TCG: What’s your current title and what is it you do today?

TM: “I am a Sr. Structural Engineer, licensed in Ohio and Missouri. At the time I did the roller coaster, my boss was licensed in CA, and at the time the law in CA said that you didn’t need to be a structural engineer if the structure wasn’t taller than 130′ or so.

TCG: What does a structural engineer do?

TM: “In this case, we set the geometry for the coaster, in plan and in profile, and then we calculated all of the elevations of all of the bents. Those are the frames that support it. They are 9′ on center, and there are 504 bents on that roller coaster, giving it a length of 4,536′ long.”

TCG: When did you first hear about Colossus and start working on it?

TM: “We started designing it in January 1977, with laying out the vertical and horizontal geometry. A friend of mine was the project manager and laid out the vertical and horizontal geometry based on the recommendations of the older people who had previously been with National Amusement Device (NAD – this was the previous name of IAD). I took over from there and calculated all of the specific geometry. The contract said the vertical geometry was to hyperbolic in the dips. We used spirals turned on their side because that mimics hyperbolic and it’s just mathematics. Nobody could tell the difference between the acceleration change in a hyperbola, or a spiral turned on its side. Spirals are typically used in surveying highways for horizontal curves. In parabolas, they’re used for vertical curves. Parabolas would’ve been a whole lot easier to use, but because the contract said hyperbolic we went to spirals instead of the parabola. We finished the design in May and construction started in August.”

TCG: Did the contract specify exactly what to design, or did the park leave it to you?

TM: “We did the layout and the park had the site. They told us where they wanted it and we laid one out that would fit in there and they approved it. The figure-8 design came from us. When you do a figure-8 on a racing coaster, you’ll always have one side that’s a loser. The train on the inside will always get ahead on the first curve, get tied up on the second curve, then lose on the third curve. There was a coaster built called the Montaña Rusa, which means Russian Mountain, down in the La Feria Chapultepec Mágico Park in Mexico City. That was the world’s largest roller coaster from 1964 to 1978, and the park wanted to beat that record. Through the 1950’s, there was not a lot of engineering involved with coaster building. It was more of an art form than a science. I believe Philadelphia Toboggan Company (PTC) had an engineer that coached people on building coasters. As a matter of fact, the coaster that eclipsed Colossus was The Beast (built by PTC) here at King’s Island, and that opened in 1979. The carpenters were the ones who gave us the knowledge on how to design a wood coaster. I went down to  Mexico City and spent a week studying that coaster and how they had detailed it. The Beast was very much built like that coaster, but we didn’t design Colossus like that. With Colossus being built in Los Angeles, and reviewed by the Los Angeles building code department with seismic standards and the Santa Ana wind loads, it took different connections and details than your typical coaster was built with. Much, much more robust connections. We also didn’t use a deadman in the center of the curves with the guy cables going out to hold it. We had the batter braces on the outside of the curves because the park wanted to have picnic tables on the inside of those two curves. They were going to develop that as a picnic spot. I don’t think they ever did that, but that’s why you see roadways under the coaster leading into the middle of the coaster.”

TCG: What was your company’s specific role with regards to Colossus?

TM: “Lorenz & Williams was contracted to do the structural engineering and all the electronic controls. It was originally designed to run 10 trains, five per track. There would be one in the station, one on the lift, two out on the track, and one on the final brake run. We designed it so that the four trains on the track would be passing each other. But, I don’t think they ever ran more than three. They had block brakes and restart motors at the top of either end, and anti-rollbacks on each of the hills. When you stop a train at the top, you take all of the kinetic energy out of it. If you release the brake and let it start rolling, there wouldn’t be enough energy to get the train home and it would end up stuck in a dip. The restart motors used tires to get the train back up to the speed it was at when you stopped it. Since they never ran five trains on a side, they did eventually take these out. They asked me about it and I said if they never intended on using them, then I would not leave them up on the top of the coaster. It’s just basic math and if you have an earthquake, it’s just that much more to rattle around.

TCG: Speaking of kinetic energy, what are some of the other forces you have to take into consideration when designing a coaster?

TM: “The design of the dips were controlled by the dynamic forces of the car. The contract said that it was to pull up to 3 1/2 Gs and have a negative G hill. They put an accelerometer on it after it was built to make sure it conformed to the contract. They had limits for lateral and vertical Gs, and even the negative G hill, which has since been removed after a fatality. That lawsuit was settled immediately and is probably why it is a Six Flags park today. There were three fatalities in the same calendar year and Newhall was self-insured. Our company had two other roller coaster proposals we were working on at the time, one in Gurnee, IL and another in Tokyo, Japan. After the accident, we went to our liability insurer who told us that our policy covered the normal stuff that we did, which was pretty much anything but amusement rides. If we wanted to do amusement rides, they would have to write a special policy for each and every ride we did. That dissuaded the partners in the firm from pursuing the business of roller coaster design. That was the first and last roller coaster we ever designed.”


Accelerometer on Colossus – Photo: © Six Flags

TCG: Tell me about some of the control systems used on the coaster.

TM: “The electronics were all Numa-Logic controls, the exact same system that the Bay Area Rapid Transit system was using at the time. This was long before PCs were used. Underneath the station was an entire wall lined up with electrical switches that controlled all five areas of blocking. All of the mechanical systems were designed by a company called Continental Consultants. This was all new to the coaster industry. The lift was the most stout in the whole world. The other equipment was all unproven and the brakes were short, so they only caught one car at a time. Most coasters at the time had a long brake that squeezed all of the knife blades on each car at once. This system would only squeeze one blade at a time. The cars were new and heavy, and there was a coupler between each car with a damper and a spring. These cars were a lot heavier than the PTC cars of the day. The original cars were a maintenance problem for them and I don’t think they kept them more than a year before switching to PTC cars. The train would shoot the brakes and it would look like a Slinky spring expanding and contracting, like an accordion. The springs and dampers were supposed to balance all this dynamic motion out, but it didn’t. The brakes wouldn’t always stop the train and you couldn’t rely on them. They didn’t last 60 days before they replaced them. Jim Blackie (Magic Mountain’s Dir of Maintenance) had to redesign the entire brake system in the conventional form.”

TCG: What’s the biggest thing to consider when designing a roller coaster?

TM: “The primary design consideration was the wind load, the Santa Ana winds on the lift and the tall parts, and dynamic loads in the dips. The seismic load is a function of mass, or the dead weight of the structure, and a wood coaster is very light, so the problem was getting the forces from one member to the other. That’s why we used steel hardware and connections. Wood is very strong and good for short-term over stress situations. For a short duration loads it can handle up to twice the stress for long duration loads. A seismic event is a very short duration load. When the Northridge earthquake hit in 1994, the maintenance crews were performing their morning inspection. They said it was swaying like a graceful old lady. When the county inspectors came through after, there were only about 20 boards that needed to be replaced, but that was from normal drying and shrinking, and had absolutely nothing to do with the earthquake. They had Colossus back open in just a few days.”

TCG: Why did Colossus survive the earthquake but Psyclone, their other wood coaster at the time, didn’t?

TM: “I heard that the other wooden roller coaster broke about 50 columns during the quake. The reason for that is because on Colossus we took the transverse bracing all the way down to the foundations and hooked it into the steel strap that is cast into the drilled shafts (footers) that support it. In the longitudinal direction we took the bracing down and scotched it against the column so the seismic forces go straight into the foundations, where they need to go. In the typical details used here on The Beast and every other roller coaster built up until that time, they stop about 18-24″ above the foundation. That 18-24″ of column can support the weight of the coaster, but any horizontal forces are just going to snap it, and that’s what happened. I remember the Colossus construction crew asking me why they needed to do that and I said it was for earthquakes. They laughed at me. You have got to provide a continuous load path. If you stop short, that’s going to become your weakest link, and nature will find the weakest link to cause a failure.”

TCG: I bet they weren’t laughing at you after it survived the Northridge earthquake.

TM: <laughs> “No, I don’t suspect they were.”

TCG: Any stories on the actual construction of the structure?

TM: “Dick Foster was the project superintendent. He was a master carpenter and did all of the shop drawings for all of that timber framing in his trailer on-site with a Texas Instruments calculator. At the time, the park was still owned by Newhall Land, and it cost them $6M to build the coaster. At that time parks had a lot bigger hand in developing rides than they do today because of liability. Dick and his crew had a big assembly line setup to prepare the lumber. Pieces were rolled down from one end to the other, which included a chop saw and a drilling line. They had steel connectors in it. When there’s a steel to wood connection it’s a sheer plate. When it’s wood to wood, it’s a split ring and then bolted together. Then they had a big table where they bolted it together, raised it with a crane, and they set it. They then put temporary bracing between the frames as they went along, and came in with profile bracing later on.”

TCG: I’ve heard stories of the coaster toppling over during construction. True?

TM: “That winter was a particularly bad winter for storms coming in off of the Pacific. There were two collapses during construction where they would get a number of bents up with temporary braces, but they didn’t have enough of the cross braces in and the winds would get high enough that it would pull the nails out of the temporary cross braces and they would go down like dominoes. Nothing but toothpicks were left and they would have to scrap that and refabricate it. That happened twice. I told them both times they needed to brace it stronger.”

TCG: Where did all the lumber come from?

TM: “The park was basically acting as their own General Contractor back then. They would buy all of the materials themselves and even concocted their own special paint for the coaster. All of the timber for that framing was dense select Douglas Fir that came out of Oregon. It had a cupric arsenic preservative treatment to keep it from being attacked by fungus or insects. That isn’t permitted anymore because it’s considered too toxic, but for it’s intended purpose it was an excellent treatment. The rails are Long Leaf Yellow Pine, and they are seven plies tall on the straightaways, and if I remember correctly they are six plies set vertically on the horizontal curves. They reverse the direction of the wood in the curves so that they can bend it. The corners are also super elevated to 3/4 of equilibrium so you still lean in a little bit. It’s not throwing you to the outside. The angle of the slope varies at the different ends of the coaster because it’s a function of the velocity.”

TCG: How do you know how high you can make each hill?

TM: “The wood coasters have to have a 3% fall from the top of the lift in order to keep running. That’s how much you lose in wind friction and rolling friction, the wheels rolling and the wind blowing on the train. Any hill that you put in needs to be lower than a 3% slope gradient from the top of the lift. On steel coasters it’s about 7% because they use rubber wheels that eat up a lot more energy, so they need a much more steeper gradient in order to keep that energy going.”

TCG: What were some of the unique challenges while building Colossus?

TM: “Anything that could go wrong, did go wrong. You get to see a lot of sparks if there’s an extension cord hanging over the track when a train goes by. When the train wouldn’t make it over a hill, it would hang up in a dip. We’d have to setup a block fall on top of the hill and get a crane to pull it up to where you could push it over. Then you’d do that again on the next hill, all the way around the track until you got it home.

Note: I did not realize this, but without the kinetic energy of the moving train, gravity alone wasn’t enough to complete the course when pushing it over a hill by hand.

TCG:  Had you ever worked on a roller coaster before?

TM: “There was an older coaster up in Waukesha, WI we did some modification s to, but this was the first one we designed from the ground up.”

TCG: Tell me about your first ride on Colossus?

TM: “Well now that is a story to tell! OSHA would not have been happy if they existed at the time. Once we got it built, more or less, me and another guy spent three days trying to get the train to go over the lift and all the way back to the station. After three days we finally got a train to come into the station after dark, around 9:00 pm. The guys were really whooping it up. Park management was there, the Bernard’s were there, everyone was there. The park manager, Larry Frack, told the maintenance guys to take a Cushman over to the maintenance shed and get some cushions because we were going to take a ride. They hadn’t even finished putting all the bracing down in the dips. I was just leery as hell. They duct taped the cushions into the first car of the train. Five guys hoped in and said get in, this is your seat. I said that they were too enthusiastic, and that we should finish putting in the bracing. They said “We’re going, do you want your seat or not?” I tell ya, I was truly frightened of that first dip. When it didn’t come apart, I really enjoyed the rest of the ride. It was a wild ride. That negative G hill was just terrifying. There was significant force trying to throw you out and you were literally just being held in by the lap bar. After that accident happened (the fatality was a woman being thrown out on the negative G hill), the county said they did not want to see any negative G forces on the coaster anywhere. You could go down to zero, but you couldn’t go negative. The radius on several of the hills was increased, usually by raising the height of some bents, to eliminate all negative G forces.

TCG: Any other funny stories to share from the project?

TM: “An interesting turn of events happened with that coaster. Colossus opened in 1978 at Magic Mountain, and the Gemini, which is a wood coaster with steel rails, opened at Cedar Point in 1978. At the time, Cedar Point was owned by George Roose. The Gemini ride at Cedar Point was designed by Arrow, out of California, and Colossus was contracted to IAD, which was owned by Bill Roose, the son of George Roose, and based out of Sandusky, OH, the home of Cedar Point.”

TCG: What’s your favorite memory from the Colossus project?

TM: “That first ride! In retrospect. At the time it was very concerning because I knew how many braces were missing on that first dip.”

TCG: Have you ever worked on another roller coaster since Colossus?

TM: “No, like I said the company I worked for wasn’t insured for amusement rides, so we steered clear of them. The firm I work for now also does not work on amusement rides.”

TCG: What would you like to see them do with Colossus?

TM: “I don’t know what they’re going to do with it, but I hope they are able to keep it in some fashion.

TCG: Do you ride roller coasters? If so, what’s your favorite?

TM: “I sure do! I’m 65 now but I was in my 20’s when I designed Colossus, so I can’t ride them as much as I did. They shake me up a little more than they used to. My favorite roller coaster is Colossus, because that’s my baby.”

I’d like to thank Tim for taking the time out of his busy schedule to meet with me. This was highly educational and extremely interesting. It definitely gives me more insight as to why Colossus seems so tame today compared to the stories I hear from people that rode it when it first opened. It wasn’t the park that neutered it, but rather the the state/county. I’d also like to thank Susan Dowty for introducing me to Tim. I’m very appreciative of both of you.


  1. steve austin

    08/03/2014 at 2:43 pm

    That was an awesome interview Kurt..but then again anything you do is always top notch an professional….i was interested in every bit of it.

  2. Henry

    08/03/2014 at 3:14 pm

    I believe that The Beast at Kings Island was built by Kings Island themselves back then, not PTC. That’s a common misconception, but PTC made the trains and that’s what is still used today on The Beast.

    • The Coaster Guy

      08/03/2014 at 3:40 pm

      I think somebody should probably tell PTC that then, because they have it listed as one of their coasters on their web site.

      • Henry

        08/04/2014 at 6:35 am

        I have a feeling that PTC needs to fix that. They have a bunch of coasters on there site that were never made by them, but the trains were supplied by them. For example, they list American Eagle at SFGAm as a coaster made by them, but Intamin made it.

  3. Ryan O'Neill

    08/03/2014 at 4:49 pm

    Roller coaster design and construction has changed so much in just 36 years. That was a fascinating look into what the job was like back then. It makes me even more excited to hopefully start working in roller coaster design someday.

    How long was the negative-G hill intact before they had to tame it?

    • The Coaster Guy

      08/03/2014 at 6:15 pm

      The ride opened in June and the accident was that December, so roughly six months.

  4. James

    08/03/2014 at 5:53 pm

    My mom was the one that contacted you haha! Awesome interview though I learned a lot!

  5. Eric

    08/03/2014 at 9:04 pm

    Excellent interview. I remember my first rides on Colossus in the summer of 1978. That was one heck of a ride, filled with the most insane airtime that I’ve experienced even to this day.

    In just a few weeks, we’ll know what SFMM has in store for this ride.

  6. Paul Lord

    08/04/2014 at 11:41 pm

    I hired on at Magic Mountain in 1978 sometime around the time that Colossus opened. I trained as a ride operator on Colossus the day before the fatal accident. The ride was closed for reprofiling & I transferred to the Gold Rusher. I was on the re-opening crew for Colossus & operated it for 2 years.

    We often ran 4 trains per side & occasionally 5 trains per side. When running 5 trains, everyone had to be on their best game to keep from setting up the ride. We had 2 lines painted the platform approximately 12″ apart & would sometimes have contests to see who would stay on the main panel by stopping the trains between the lines. I held the record for staying on panel for 2.5 hours while running 5 trains. I didn’t lose the panel by missing the stop, I was required to take a lunch break. When the trains did get stuck on the block brakes, we would push them off & they could make it to the station on their own, although I did hear stories about having to winch the original trains out of the valleys occasionally.

    I was also the first operator to run a train backwards on the Colossus – It had sand bags for ballast & instruments for measuring the G-forces.

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