Every so often you hear about a coaster train valleying, meaning that it fails to resch the top of a hill and rolls back. How often does that happen, what causes this to happen, and how is the train lifted out of the awkward position that it ends up in?
RWB use to valley every so often during the fall frightfest. They said it was a combination of cold weather , (makes the grease thick) and not enough people on the ride to create enough momentum to overcome the difference.
It some cases, they unhitch the trains and manually push them up the hills. (they use to do this at Euclid Beach.) *** Edited 6/30/2008 1:02:48 PM UTC by FLYINGSCOOTER***
It happens when some factor causes it to lose more of it's energy than it was designed for. This can be cold weather (this causes the axle grease to be 'thicker' and less 'flowy'. Therefore, the train loses more energy to heat from friction, which means less energy in the form of motion, so it slows down more than if the axle grease were warm.
Other causes are gusts of wind, damaged wheels etc.
Some coasters are more susceptible than others. If a coaster has hills that it goes slowly over (like Gemini's turns), as opposed to a coaster that goes fast over it's hills (Millenium Force's 3rd hill), it's more likely to happen.
As for what they do about it... I've seen them use a front-loaded and a chain to pull Blue Streak up to the turnaround and then literally push it, jump in when it started moving, then get out and push if it stopped again.
Other times, they remove the upstops, and pick the cars off one by one with a crane.
It all depends on which ride valley's and where. A few years ago when we were at Americanna, their Galaxy valleyed. After unloading the people from the car, they winched the car up the hill by hand and let it go to run the rest of the course. With a coaster train I'm sure the process is more complex.
Rollbacks typically occur a. early in the season and b. early in the morning, but are not limited to those times. in the morning, the grease is a bit thicker and therefore, friction may be a bit larger. In the spring, the coaster has yet to be "worked in" and may have the same general issues.
As a sidenote, a couple of years ago I was at Martin's Fantasy Island. Sitting on the floor of the coaster train was a set of sand bags. Why? To help increase the weight of the coaster train to avoid rollbacks. Talk about an interesting experience riding with a sand bag between your feet.
I know that SFOT's Mr. Freeze has valleyed on a few occasions because the LIMS on the spike didn't energize. They removed the upstops and used a crane to lift the cars off the track.
When it was new, Krypton valleyed before the cobra roll on a cold windy morning test run. Fiesta Texas made a call to B&M and were told to pull the train through, rather than try to remove the upstops.
When I worked at Carowinds on cold days maintainance would stand at the exits to the tunnels of the Goldrusher and give the train a hand as it climbed out while we cycled it to warm it up.
One day when they weren't doing this a cycling train dropped back into the last tunnel. The used a cable under the brake run track to pull it back up the hill and into the station.
I also heard that if the old White Lightnin' shuttle loop misfired and valleyed after the loop then it would take 20 minutes to stop rolling back and forth. I never witnessed this however. *** Edited 6/30/2008 3:35:24 PM UTC by john13601***
One thing I do find interesting. When you think of the older, classic coasters (i.e. Conneaut Lake Blue Streak, Geauga Lake Big Dipper, Phoenix at Knobels, etc.) there always was a set of anti-rollbacks on the way up hills where a rollback might be prevalent. Yet the newer coasters do not seem to have this designed into them... Maybe coaster designers should take a lesson from past history...
Walt S., right on. The idea that a coaster does NOT have an anti-rollback mechanism shocks the crap out of me. I mean, sure, if you have LIM's instead of a chain lift, an anti-rollback might be more difficlt, but what are the prevention measures that ARE on these newer coaster?
"Look at us spinning out in the madness of a roller coaster" - Dave Matthews Band
As my understanding of LIMs goes, they are only magnets when electricity is going through them and that is why the impulse coasters like Wicked Twister have magnets that drop down to slow the train in the event of an E-Stop since E-stops cut the power to the ride *** Edited 6/30/2008 5:40:00 PM UTC by Goliath Freak***
Another reason having me think they are electromagnest is look at the V2's, Voodoo, and the others. The LIMs on the back spike don't affect the train unless the electricity is on (to hold the train). The first time up the back spike, it is as if the LIMs are not even present. The second trip up the back spike, the electricity is on and the LIMs are able to hold the train in place. Also, the last time forwards through the station, the LIMs are off and it just coasts through the station, the LIMs do not slow the train down at all. *** Edited 6/30/2008 6:02:55 PM UTC by Goliath Freak***
Spinout said: Boomerangs valley because of releasing early, wind, not enough weight, rain, and so on. Sometimes, the brakes aren't applied, and the train gets stuck in the cobra roll.
Vekoma Boomerangs always amazed me. There's a whole sequence of events (mostly brakes opening and closing) that take place that are supposed to keep the train from valleying in the boomerang element, yet it happens relatively frequently.
When I was at Cliff's in New Mexico, The Rattler had "valleyed" at the top of the butterfly turn around. So I guess some coasters still do have antirollbacks at the tops of hills, but since there is a tunnel under a walkway at the bottom of the hill, stopping at the top is probably preferred.
I was really impressed with them, they used winches that attached to the handrails and moved the train forward literally inch by inch. It took the 5 hours to get the train over the hill. They were able to get it open for the last half hour the park was open, which I thought was first class.
Walt S said: Some do. There are anti-rollbacks on Boardwalk Bullet, and I'm pretty sure they're on Ravine Flyer II as well.
I was unaware RFII had them; guess I didn't notice them on my ride last week. But in general, there has been a move away from anti-rollbacks other than the first hill. Whether that is because coasters are generally running a bit faster than they used to through their courses, or better engineering, I can not say.