It’s Alive! Roped Hydraulic Elevators Explained

Trickortreat
Trick or Treat has come a long way from Frankenstein to fairy princesses.

Halloween has definitely changed over the years from monsters and scary masks to fairy princesses. When I was a child it all seemed more frightening. I remember going door to door and then watching the old black and white Frankenstein movie after getting back from trick or treating. It was petrifying as Doctor Frankenstein creates a creature out of various body parts and then sends some electricity through a couple of bolts in its neck. As lightening cracks and thunder roars, the monster slowly moves its hand as the good doctor, clearly insane, starts screaming “It’s alive”.

It all seems logical enough. Take various parts, sew them all together, add some power and voila you have a functioning creature.

At first blush this is the impression you can get when you think about a roped hydraulic elevator. A strange amalgamation of a hydraulic elevator system, sheaves and ropes. Just turn on the juice and “It’s alive!” On the surface it makes no sense. Hydraulic elevatorswork just fine and so do traction elevators with all their ropes. The pairing of cables with pistons however, is not the creation of a mad scientist in a castle somewhere in pastoral Germany. It is a system that has some benefits to consider when determining the best option when replacing or installing an elevator.

A simple diagram of a roped hydraulic elevator produced by Phoenix Modular Elevator. How does it work?  Instead of the top of the piston or pistons being directly connected to the sling (the frame that holds the elevator car), it has a sheave or pulley wheel mounted at the top of the jack, above the car. As the jack is raised and lowered the sheave goes up and down. A rope or heavy braided cable attaches to the car, goes over the sheave and then is anchored to the hoistway below the lowest level of the piston.

There are clear benefits to this type of elevator, the most important being the 2:1 ratio of car to jack movement created by the use of sheaves and ropes. The 2:1 ratio gives a greater range of travel and allows for a shorter jack. Because the jack(s) can be shorter, greater travel distance can be achieved without going to an in-ground jack with its associated drilling costs.

The travel speed is comparable to a hydraulic elevator at 200 feet per minute, but the travel distance can easily be over 80 feet as the ropes double the effective length of the jacks.

The downside includes the obvious: with both a hydraulic unit and ropes to attend to, they are more costly to maintain and as there are more parts, including sheaves, ropes and guiderails, they can be more costly to install than direct hydraulic elevators.  However, they are still less complex and less expensive than traction elevators.

The decision as with all elevator types is, does it make most sense based upon the use of the building, the total travel needed and the overall budget for the project. This unnatural creature seems to have a limited niche, typically installed in mid-rise buildings (7-10 stories).  And in this travel range most of the bigger elevator companies are moving away from this type of conveyance and pushing machine roomless elevators instead.

However, just because Bigg Elevator doesn’t offer roped hydraulic elevators doesn’t mean that they shouldn’t be considered and they will likely be around for quite a long time to come. After all, as Frankenstein taught us, it’s hard to kill a monster.

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