Question РRegarding braking, usually how big is a fin brake and is it usually in the middle or toward the sides?

A1: This is certainly determined by the forces involved, but a typical brakes that we work with is by a company called Coastasur, or is it Costasur? Anyway, the brass (?) pinching surfaces are about 2 inches high by maybe 4 feet long. Multiple units are used to slow the train in fast areas. Almost never is a single brake used (although often one would do it, such as for simple holding applications) because of the “single point of failure” issue. The fin is usually tall enough to well over-penetrate the pinching surface of the brake. Fins generally run nearly the full length of the car, and usually every car in the train will have a fin.

As I remember from school, it is not so much the contact area but the force normal to the braking surface that determines the braking force. It comes down to the amount of time that the fin is in a brake with a certain pinching force. But don’t quote me on that. I’m an EE.

In our business, we are told how many brakes of what type there will be. Our job is to control them. Often we will note problems with brake failure scenarios, and therefore require that the ME give us more brakes for that reason, or we may tell him that for train logic reasons he doesn’t need certain brakes, but the brake’s ability to be a brake is not our business.

Q2: How is the section of the bogie or the underside of the car designed to allow the track mounted booster wheels to do their job?

A2: Not my area of expertise, but I’ve seen two general types. A flat platen under the vehicle upon which a single rubber tire with a horizontal axis bites. The reaction forces are a problem with this design (holding the vehicle down on top of the drive wheel) so more often pinch rollers (vertical axis of wheel rotation) are used, operating on the brake fin. The roller draws the fin in and pushes it out. Either arrangement can also be used as a brake, but the motor drive must be properly selected so that the motor can absorb the energy under control (dynamic or regenerative braking, where the motor becomes a generator.) With all of these arrangements, tire wear is an issue. They (MEs) work hard to reduce the slip. They often ask us to do things with motor control to help. For example we can detect or predict the vehicle’s entry speed, set the motor speed accordingly, then after we have “caught” the vehicle apply the accelerating or decelerating forces.

Then there are the rides we do with LIMs, which have no frictions points.

I know that was not what you were looking for in an answer, but maybe useful.

Q3: Where are the tanks or reservoirs for the hydraulic fluids used in the restraining system located?

A3: If you mean the on-board restraints, like lap bars and the like, there are never (that I recall) any on-board energy sources or reservoirs. The on-board device usually works against a spring, usually with a ratchet mechanism. An off-board actuator in the load area is often used to press a button, lever, cam or something that releases the restrain. Our job is often to position the train in the load and unload areas with enough accuracy that the actuator can hit the mark to release the restraints. Sometimes they make it easy for us by making the releasing actuator run the length of the area so it hits all the release points with ease. The actuators are generally pneumatic, and operated from “house” air pressure of about 80 PSI. We control a solenoid to actuate the release.

Q4: If electric signals are used to activate/deactivate the hydraulics in the station, what type of material is used for the receiver and would that receiver still be located on the side of the ride down toward the bottom?

A4: By “receiver” do you mean a device that receives the electrical signals that control things like brakes and release platens? If so, the generic name would be “transducer” and since your brakes are usually pneumatic, your transducer is either going to be a solenoid operated valve (that is either open or closed to air) or a proportional valve (that can carefully meter air flow).

Either way, this valve can be mounted most anywhere as long as the air lines between the valve and the actuator (cylinder or bellows, or whatever) don’t get too long (because of the delay to fill the lines with air). In practice I notice that they try not to go much over about 20 feet, and for some applications requiring fast action or tight speed regulation they will keep the distances to a couple off feet. The valves are usually located in a water tight box under or adjacent to the track. This box also serves as a termination point for the pressure sensors that we use to monitor the proper operation of the brakes.

Q5: In the last e-mail you sent to me you told me that the on-board restraints are usually only springs with a ratchet mechanism. My simple question then is how are the on-board restraints actuated and held in position? For example, the restraints which require no rider involvement and are self positioning or which are free to move about until the operator locks them into place. What positions or activates the spring and ratchet which makes up the lock?

A5: Imagine a lap-bar or what ever kind of restraint. The train is sitting in the load area. Let’s say the release mechanism is actuated, and remains actuated. (Some are maintained, others only momentary to release, it depends on the park’s preference.) In this configuration, the lap bar can be pulled down onto the lab of a seated rider, but when you let go it will move by spring action back to the up position. Now, imagine that we deactivate the release mechanism. The ratchet comes into play now. When the rider or operator pulls the lap bar down (against the spring) the lap bar stays there because the ratchet holds it in place. The ratchet has many detents to account for the various sizes of riders. The rider (usually) or the operator (if the rider didn’t do it) pulls or pushes the lap bar down until it is snug and the lap bar stays there until the train enters the unload area where the trackside release mechanism pushes the “button” to release the ratchet. While on the ride the rider can always tighten the lap bar, but never loosen it. The release mechanism, operated from trackside by levers under the train, just pulls the dog out of the detent in the ratchet. (I’m not sure I’m using the mechanical terms correctly, remember, I’m an EE.)

Does that help?

Q6: Do hydraulics within the station (loading area) activate these mechanisms then retract? I presently feel comfortable in my understanding of the unlocking process, but its converse is really bothering me in my sleep.

A6: Yes, it could be hydraulics but I’ve always seen it as pneumatics. Save the messy hydraulics for the places where you really need the uncompressible nature of hydraulic fluid. A air operated pneumatic cylinder with a plate on the end of the rod can push the “button” on the side of the train, down low, to operate the mechanism, by levers, that pulls the dog out of the detent so that the lap bar will go up under force of the spring. That sure beats trying to figure out how to get some form of energy on board the vehicle.

Q7: Also, in my question about the design of the underside of the car and how it allows for the booster wheels to do their jobs you mentioned the absence of friction points with LIM systems. Could you please go into depth about how that effects the design, or how the LIM is used in contrast to booster wheels?

A7: Are you familiar with Linear Induction Motors? They do not need mechanical bearings. They are like a motor (which is a round thing) laid out flat! Instead of spinning a shaft, the magnetic field that is created by what was the stator of the motor now pushes a flat metal plate along the flat surface of the motor. Attach that plate to the vehicle, and line up a bunch of these stators and you have a vehicle propelled by a moving magnetic field. There are lots of trade-offs here. Linear Induction motors are neat but very inefficient. They will also burn up if you run them for more than about a second with out a plate to push on. But they do eliminate all that squealing and chaffing that occurs when the booster wheel (spinning at a preset speed) encounters a vehicle moving at a different speed.

I expect that there is info on the Internet somewhere about how LIMs work, although they are not very common. I expect that only maybe 10 rides in the world use them. We have done three and I know of only two other coasters that use them, one ride at Disney, and a People Mover in Houston. I’m sure there are others, but they are uncommon. Roller coasters mostly use friction drives (your booster wheel, I think), chain lifts, or in the case of water type rides often lift belts are used.

There are a few that use a sling arrangement. Imagine lifting a big weight, hooking it to the vehicle by a cable with a hook at the end, then take the brakes off the vehicle and drop the weight.