Our two post lifts (as well as most of those on the market) employ one of two different methods of cylinder configuration. All of our two post above ground lifts have a power unit (220 volt single phase) located on one of the columns. The columns are symmetrical so the column with the mounting fixture for the power unit may be located on either side.
The power unit supplies pressurized hydraulic fluid to the cylinders (located in both columns) through hydraulic hoses that run between the columns. Each of these cylinders have a piston that is moved (actuated by hydraulic pressure) and "lifts" the carriages and arms, which in turn "lift" the vehicle. There are also two sets of equalization cables that connect the carriages located in each column. These equalization cables (high strength aircraft cable) provide tension on the carriages to make sure that both sides go up at the same speed. The cables do not do the lifting! The pressurized hydraulic fluid powering the cylinder/piston combination provides all the lifting power.
The hydraulic hose and cables for two post lifts need to run from the powered column to the slave column; either on the floor or through an overhead bar.
Baseplate (Floor Plate/Low Ceiling/Low Clearance) Above Ground Lifts:
The hydraulic hose and equalization cables run across the floor and are covered by a beveled diamond plate steel floor plate approximately 1" tall in the Baseplate Lift (Floor Plate). Most baseplate lifts have a locking mechanism that is operated with the dual point release system.OR
Overhead Lift (Clear Floor):
The hydraulic hose and equalization cables run across the top of the lift through a metal bar (conduit) that connects both columns in the Overhead lift. The metal bar (conduit) is there to guide the hose and cables and is not designed to support any vertical weight. There is a cut-off cable (connected to the power unit) located just below the metal overhead conduit which "kills" power to the motor preventing damage to the top of the car, if the lift operator was not paying attention.
Benefits of an Overhead Lift:
An overhead lift has nothing on the floor between the two columns; this design makes it much easier to roll jacks, oil drains, etc, through the middle area of the lift.
Overhead lifts can accommodate asymmetric or symmetric arm configurations. The baseplate lift can only accommodate a symmetric arm configuration (if you have been advised differently, call us for the facts).
Overhead vs. Baseplate (Lifting stability):
The basic design of the overhead two post lift offers more lifting stability than the same rated capacity lift that has a baseplate design. The overhead bar (located between the two columns) provides a measure of stability by exerting pressure to the top part of both columns.
The bases of the columns (anchored firmly in the concrete) provide the ONLY foundation of support for the base plate lift columns. When a vehicle is placed on the extended lift arms (between the anchored columns) and lifted, there is a great amount of pressure applied to the rear anchor bolts of the column's bases.
Imagine two people facing each other (like our symmetrical columns) extending their arms out in front of them (like either our asymmetric arms or symmetric arms). Place a heavy weight (evenly distributed) on the hands (lift pads) of these individuals. Gravity, exerting an enormous downward pressure on their outstretched arms, would force their heels to try and lift off the ground. Their bodies (our columns) would try to "lean forward" to compensate for this load positioned on their hands. However, if the two individuals had a bar between their foreheads (like the overhead lift design), then this bar would exert a certain pressure to keep their "heels on the ground".