Unfortunatly, I have no idea what the specifics of the system are, but hopefully those pictures will help you a little. *** Edited 12/12/2004 3:03:10 AM UTC by Coaster Lover***
The hoisting rope, a large wire rope, runs vertically from the winding drum, up to the end of the catchwagon track, over a series of sheaves so that it doesn't drag on the catchwagon track, and it attaches to the front of the catchwagon.
The catchwagon is a segmented train of metal blocks, with whels positioned between the segments. The catchwagon is slightly longer than half the length of the train. At the back end of the catchwagon there is an opening with a rod across the back which approximates a single link in a standard coaster chain. On the train, there is a single hoisting clutch positioned near the center of the train; I think it's on the back of Car #5. This clutch is similar in design and function to the standard chain clutches found on most coasters.
A return rope is attached to the front of the catchwagon. The return rope is routed down the lift hill and through the track just downtrack of the station. That rope goes from there forward to the winding drum and attaches to the same winding drum as the hoisting rope. The assembly in CoasterBuzz photo 731 is a tensioner assembly to take up any slack in the return rope.
In the station, the train engages with the catchwagon. The winding drum is put into motion, and it pulls in the hoisting rope, pulling the catchwagon (and thus the train) up the lift. The return rope pays out from the winding drum and follows the catchwagon up the lift hill. Once the train's center of mass passes the peak of the hill, it over-runs the catchwagon and keeps going down the hill. The problem with this is that nearly the full length of the catchwagon is now past the hill peak, so gravity isn't going to bring it back. That's why there is a return cable: to pull the catchwagon back over the peak of the hill so that it can return to the station. Once the catchwagon is over the top, the rope paying out from the winding drum regulates the speed of the catchwagon as it returns to the station.
The reason the catchwagon is so long is that it has to connect with the middle of the train in order to get the train far enough past the hill peak for gravity to pull it down the other side. The reason they use a long catchwagon instead of a short one as on Top Thrill Dragster is so that the hoisting rope does not drag against the front of the train through the curve at the bottom of the lift. As Top Thrill Dragster's train is disconnected from its catchwagon before the train hits the upward curve, that long segmented catchwagon is not necessary.
There's the thousand words to go with the photos. :)
--Dave Althoff, Jr.
I also have one of the lift evac. car.
As for the anti-rollback system...there are anti-rollback dogs on the train. I don't know the details of how THAT system works because it is hidden beneath the cover panels, but in general, there is an idler wheel that rides up the outboard side of the catchwagon track. As long as that wheel is rolling *forward*, a mechanism lifts the anti-rollback dogs away from the holes in the track. I don't know exactly how it works; there are several methods they could use: It could be a rotating cam, spring-loaded to drop the dogs, as was used on Drachen Fire and as is used on the Mack Wild Mice. It could be a miniature generator that generates an electrical current to drive an electromagnet to lift the dog. That's similar to what Intamin did on the Superman coasters; that is described in great detail in United States Patent #5,947,030...do a patent number search at http://www.uspto/gov for details.
Anyway, what is known is that the action of the anti-rollback silencer is related to the train speed, and to something rolling on the catchwagon track. That's why there is an anti-slip black grit coating on the surface; early on the wheels were slipping, and on one train they still do at the top of the lift. If you've ever stopped on the lift, then you know that on re-start, the anti-rollbacks are really noisy until the train is moving quite fast.
--Dave Althoff, Jr.
You can see a woman leaving the station who, by my guess, is too big to ride. Ahh, this brings back memories.
As for the anti-rollbacks I believe, as said earlier, that they are magnetic. The rolling wheels keep the dog from "clicking" up the hill. When the train goes too slow, or gets restarted on the hill, you can hear the drag before the train gets up to speed. Also at times the wheels either deflate or wear out and that causes the rollbacks to drag up the entire hill. It's really quite loud when you expect a quiet ride up the hill.
1) The anti-rollback wheels on MF are actually inflated tires similar to those on TA2K. When they lose enough air pressure (or deflate slightly) the wheels will no longer get enough traction and the rollbacks will make noise. Although uncommon, it was reason to transfer a train off for repair on occassion.
2) As for how they actually work, I will do my best to explain. There is a piece of brass (or perhaps copper?) that sits next to the wheels. The one end of this piece bends over the wheel's axle when the wheel is not rotating. As it picks up enough speed, the wheel's rotation creates a magnetic field that causes the metal piece to rise vertically (toward the bottom of the train). The other end of this piece is attached to the rollbacks themselves so that as it lifts up, it brings the rollbacks with it.
Another thing about the anti-rollback tire, besides the loss of air, is that water on the lift can cause the tires to slide and not spin. I'm sure anyone who's been around when the ride starts running after a heavy rain has heard the racket from the rollbacks dropping.
But there are a few advantages to hydraulic motors that would make one well suited to this particular application...
A hydraulic motor can provide full torque at any speed, can be easily controlled, and can be very easily reversed. Furthermore, I understand that the ride can operate (that is, the train can be hauled to the top of the lift) using a backup gas engine instead of the electric drive. With only a pair of clutches, it would be simple to connect the pump to both the electric motor and the gas engine.
Remember on most coasters, the lift runs continuously, perhaps slowed between cycles if there is a VFD in place...but the motor usually runs at full speed (and full torque) from before the train engages until the train goes over the hill. On Millennium Force, the lift drive has to start the train from a dead stop every time. If you have ever watched a conventional lift start up, especially with a train on the lift, you can see that the standard electric motor is not necessarily well suited to that operation.
That said, there are electric motors and electric motor configurations out there that can apply huge loads at startup. But that is a bit more complex than is really required for a fairly simple rope hoist.
--Dave Althoff, Jr.
Drum, transmission and motor (looks like hydraulic hoses coming out of it to me)
--Dave Althoff, Jr.
(Craig: You mean you bothered to count?!)
Yah, good point...those lift starts are pretty violently.
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