# Linear force multiplication (or division) without hydraulics

Gears are used to transfer power between two rotating shafts, either by increasing or decreasing the angular speed, with a corresponding inverse change in the torque. If I want to do the same for linear motion, I see only two options in front of me:

1. Use Pascals law for liquids and connect pipe of varying diameters to multiply (or divide ) the force, as is done in car jacks, or,

2. Connect the input linear drive to a rotating shaft, connect it to a step-up or step down gear, and then convert rotary motion back to linear.

Hydraulic cylinders are kind of costly and keeping the fluid at a higher pressure is not quite convenient. Also using a linear-rotary-linear power transfer is easy to build but quite inefficient. Is there another way to do this?

• Special case of the rotating shaft : the lever. No gearing required, infinitely adjustable ratio, and only a simple connecting rod (with fixed guides or Watt linkage) to convert back to linear motion. Jan 17, 2017 at 10:11
• I will look into it. Jan 17, 2017 at 10:36
• Pulleys are a traditional way to get mechanical advantage. Try looking up 'block and fall.' Jan 17, 2017 at 14:27

## 1 Answer

Take into a count what you want to do. Hydraulics is used for a reason: it can transmit huge power. The idea of using gears and then using a linear one is good, but you need to know if it is going to be able to handle the weight and internal reactions on the gears. Also, take into a count the size of the gears, if they already exist inside a catalog and you can buy them easily, because if you have to manufacture them you will find it is really expensive.