Home : Technical : Detachable Lifts : Terminals/Stations : Cadence Systems

Some terms:

Passive cadencing: More commonly known as the chain system, this consists of a chain with a specifically spaced set of teeth on one end of the lift, and a conveyor with teeth on every link on the other end. Both chains run at a constant speed. The cadence chain captures the chair, carries it around the contour, and puts it into the acceleration tyre bank for the trip up (or down) the hill. The conveyor chain does the same, except it does not space the chair. The speed of both chains can be varied to suit several conditions: the conveyor can be sped up or slowed down depending upon temperature, and the cadence can be adjusted for different chair spacing. Both should match as closely as possible, else chair spacing gets out of sync. More on this in a bit.

Active cadencing: The current standard, this is where there are one or two clutches attached to parts of the tyre bank which can very the speed of that set of tyres. The PLC uses the zone switches inside the terminal to turn the clutch(es) on or off depending upon the space of the chair.

Problems with both types:
Chain systems are highly susceptible to temperature. For example, on a very cold day, the haul rope shrinks, bringing the carriage forward. Because of this, the position of the rope in relation to the chain changes (in this case, the rope literally moves further from the chain) causing the chairs to 'come in late'. The opposite occurs on a warm day. The problem can be solved by speeding up or slowing down the conveyor on the opposite end of the lift; if you speed it up you overcome the late issue by placing the chairs 'ahead' on the rope. Of course, when it warms up the chairs then stall out at the end of the tyre bank while waiting for the teeth, so you then have to slow the conveyor chain down.

Active systems eliminate the problems associated with chains, but have a few of their own. In a chain system, if a chair is out of whack it is easy to respace (simply move the chair forward or backward into the teeth). In an active tyre system, it may take several laps to respace as the clutch can only advance or retard a carrier by a few feet at one time. If the clutch goes out (usually an electrical problem) there is no spacing going on at all and it is nearly impossible to fix this.

Zones and anticollision faults:
The lifts PLC monitors the spacing of carriers in the terminals by a system of sensors located at intervals around the rail. Each zone has a time value associated with it; if a carrier is in the zone longer than that value the lift will shut down. This prevents phisical collisions between chairs. If a chair were to stall at the end of the tyre bank, it would cause a zone fault. This is why one needs to monitor where the chairs are arriving in relation to the chain teeth, on that type of system.

I hope this answers some questions. Feel free to post any others in the forum that you may you may have.

Older style Gondolas with human conveying systems used steeper sloped deceleration/acceleration tracks (gravity never sleeps) as a design element. The sloped tracks were set to work best in the upper speed ranges. Of course there were a few tiny things the operator had to be aware of.

At slow speeds the carrier never quite made it up the deceleration ramp, this required a push from the operator or the car rolled back to the haulrope detaching area.

At full speed with a full load the car had enough momentum to make the 180 degree turn after detaching, which was ok unless there was a car in the turn.

The anti-collision system was an operator who stood between the cabins and pushed or pulled as necessary, they also doubled as the power for "conveying" the carrier to the launch area. The spacing system was an operator who adjusted cabins by referencing "match marks" painted on the track for proper distance.

The acceleration area track sloped down to help assist the launching operator push the carrier toward the up-line haul rope. Carrier spacing for attachment was more of an art than science… push sorta hard after the loaded car passes the bent I-beam unless we're on slow speed then wait until it passes the red angle iron.

Needless to say, if grip speed and rope speed often didn't match this would impart a large jerk to the carrier, which caused grip wear, which helped to employ lift mechanics.