Pulleys are a very useful element that has been used since ancient times for handling heavy loads, both in construction and transport. It is a mechanism that we use in Airpes for our weighing systems, as well as in overload controllers for the cranes we manufacture. But how does a pulley work? What can it be used for?
Everybody knows that somehow a pulley will give you a mechanical advantage but people don’t really understand it.
We all pretend like we understand how pulleys work but we only make it when the clever person shows up and makes things work.
When you use a pulley to try to pick something up from the floor, the pulley changes the direction of the force so you can use your own body weight to help you pick something up.
But you can always add more pulleys or a snatch block into the system to multiply the force you are doing. This applies as well when there’s an engine lifting the load.
Multiply the force for free
Adding more ropes we can multiply the force we are applying on the edge of the rope:
- One more pulley will multiply the force by two.
- Two pulleys will multiply it per 4.
At the same time, every time you double the pulling force of the mechanism you will need more pulleys, but it will allow you, or the engine you have installed in your crane, to lift a considerably heavy weight using the mechanical advantage that the pulleys give to the system.
Archimedes was the first modern scientist to realise how pulleys and snatch blocks can give you mechanical advantage. In fact it is attributed to Archimedes the invention of the pulley and the multipulley system (based on the knowledge he had about the lever).
Plutarch mentions a conversation between Archimedes and Hieron the king of Syracuse where Archimedes proves that he could lift a whole warship using just his own force and a custom designed system of pulleys and snatch blocks.
Archimedes later was the man who designed many machinery for stopping the roman invasion of Syracuse.
Biggest difference between being on Earth and being in space is that in space you’re weightless and when you’re floating around weightless like on the space shuttle it’s really hard to get leverage:
- You can’t dig your feet
- You can’t use the weight of things to hold them in place
So having a way to hook on one end and hook on the other end and apply a steadily increasing force is really important for daily works in space.
And that’s why on board the space shuttle the astronauts have pulleys and snatch blocks: they’re part of normal equipment.
In fact there’s a special storage box for them inside the International Space station. That box contains a couple and they can be used use pretty regularly both inside the ship and even outside during a spacewalk.
In Airpes we have wide experience in the design and installation of many types of lifting systems, including blocks, snatch blocks and hook blocks, combining them with the lifting equipment the client would need.