A bottle jack is a small hydraulic cell composed of an oil reservoir, a piston, valves controlling the flow of hydraulic oil and a lever to pump hydraulic pressure. You can think of most jacks, lifts or levers as having a mechanical ratio expressed in the amount of energy exerted on the jack relative to the amount of energy exerted by the jack. It can also be expressed in the distance of the input motion relative to the distance of the output motion. Bottle jacks allow you to make many pumping motions that translate into a much smaller lift of the jack's piston. As a result, you can lift extremely heavy objects with the jack, essentially by dividing the lift into many extremely small increments. When designing and building heavy-duty lifts, consider heavy equipment. You can use a bottle jack to actuate any armature you want, much like a backhoe or scissor lift.
Using affordable hydraulic jacks, you can make all kinds of lifts. Early lifts used mechanical advantage to allow human exertion to lift heavy objects. For example, with a block-and-tackle pulley system, you may be able to lift cargo weighing a ton. With the strength of hydraulics handling that function, the lift designs can use the jacks' strength to do the opposite: mechanically translating relatively small inputs into large lifting motions.
A scissor lift is an accordion-like armature actuated by a screw or hydraulic input. Scissor lifts come in many scales. Businesses ranging from builders, window washers and aviation maintenance companies use scissor lifts as a mobile scaffolding with a work platform sitting atop the lift. On a smaller scale, many auto jacks are scissor lifts, requiring you to spin a screw laboriously to fix your flat tire. You can modify such scissor jacks, incorporating a bottle jack to make the process easier. You can also borrow the concept and fabricate your own scissor lift capable of lifting a person, car engine or anything else you need to lift.
A service lift is another design commonly seen in auto jacks. Service lifts are sometimes called "speed jacks" because race car teams use them to raise the corner of a car quickly. A service lift, like most lifts, uses a lever design; think of the design as one portion of a scissor lift's design because it only has one pivot point. A service lift has an ideal design for lifting a car or anything analogous, such as lifting the corner of heavy furniture. A key difference between a speed jack design and a scissor lift design lies in the fact that a scissor lift raises straight up and a speed jack rocks back toward you slightly as you lift. Like a scissor lift, it can incorporate square channel, a round hinge pin and a bottle jack.
A transmission lift combines design elements of both the scissor lift and the speed jack. Like the speed jack, it slides underneath objects to lift them up rather than providing a platform to give you access to high places. It shares the scissor lift's accordion-style lift-mechanism, which lifts straight up, rather than rocking back on a pivot point. When cutting and welding steel armatures, linked by hinge pins and actuated by bottle jacks, you have few limitations in the kinds of lifts you can design and build yourself.
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