As an aside, I think you are confusing the slowing down method, and the safety brake method. They are seperate and distinct. One is used as a damper, the other is for when the everything including the damper FAILS.
The safety brake is a LOCK. You don't want to do that with PVC.
I have actually seen a design for an elevator using plastic tubing for the raising and lowering mechanism(pneumatics)

Clay


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