Is that a pneumatic pump driving that arm?

[PrudensOptimus]

Hi...


I've seen a lot of tractors, they seem to have a shiny aluminum on their arms.. Are those pumps?? What are the advantages of using them? And how to configure them, do they power by motor?

Please explain in details, thank you.

 

[FredGarvin]

If you are referring to bulldozers, front end loaders and such, then those are hydraulic actuators. The benefits of hydraulic are many, as are the drawbacks. Do a google search on hydraulics and hydraulic systems. You will find plenty of information out there. You can also check the "How Things Work" website that was given to you in a previous post.

 

[PrudensOptimus]

Thanks a lot friend.

 

[PrudensOptimus]

In a brief, what are the common uses of hydraughtics? and pros and cons?

 

[Cliff_J]

Hydraulics offer an incredible amount of force in a very small package, used anywhere something big needs to move from aircraft or earthmoving all the way down to the hydraulic brakes on a car or motorcycle.

http://science.howstuffworks.com/backhoe-loader3.htm

Its all about the piston in a 3" cylinder and applying 3000 lbs/in^2 over that surface area. Do the math and you see that small package yields just over 10.6 tons of force.

Just like gear trains though, force and speed are factors in power, so the increase in force comes at the expense of speed (in this case quantity of fluid).

For small scale robotics, air cylinders are used and compressed air or CO2 make for less mess in case of leaks and eliminate the need for a pump.

 

[Integral]

I believe that if you investigate closer you will find that the "shiny cylinders" are not aluminum, but are steel. I do not think that aluminum would handle the stresses very well.

There are 2, similar but separate, fields mentioned here. Hydraulic system have a fluid, generally some form of oil ( I deal with some water hydraulic systems) which is mechanically pumped to a high pressure then used to move pistons (That is the "shiny cylinder" you see) which are connected to gain large mechanical advantage. This is what you see in the heavy equipment doing road work (etc.).

There are also pneumatic devices which use air or some other gas (Nitrogen is not uncommon) to activate cylinders similar to, but generally MUCH smaller, then the hydraulic cylinders you normally see. Pneumatics are used intensively in places like wafer fabs, to hold and move product (wafers) as they pass through the various tools used to create solid state circuits.

 

[PrudensOptimus]

fluids? They use water?

I thought they pump air...

 

[FredGarvin]

Pneumatic systems use air as the driving fluid. Hydraulics use liquids. The brakes on your car is an example of a hydraulic system. Take a look at the small plastic reservoir filled with an oil looking type of fluid. It is most likely a reddish color. That is the hydraulic fluid used to provide your power brakes.

 

[PrudensOptimus]

do different types of fluids offer different amount of force?

 

[brewnog]

do different types of fluids offer different amount of force?

No.

Instead, hydraulic fluid is designed to perform well under pressure and heat. In some cases, it needs to be able to provide a good seal, and viscosity is important.

 

[Cliff_J]

No, the force is based on the pressure. Oil or water would work equally well since they are both treated as incompressible (they don't compress) except water leads to rust on steel parts and freezes easily.

Air is compressible making the force the same for the same pressure BUT reducing the range of pressures available and has other side effects making it impractical for earthmoving or large applications requiring large forces (where the piston needs to be very big to offset the low pressure).

For semi-trucks, air brakes are used instead of the hydraulic brakes on a car but this has to do with the trailer and ability to reconnect/disconnect the trailer. With hydraulic brakes a very bad thing is to introduce air into the system - its compressibility can effectively reduce the hydraulic pressure to nearly nothing as far as the application is concerned. So to avoid a problem with air getting into a hydraulic setup the trucks use air and have giant brake systems that would be very impractical on a car.

On a car's hydraulic braking system, the term "bleeding the brakes" means to remove air from the system and old fluid. The fliuid is hydroscopic (absorbs water) and this water can form steam under heating and this creates a pocket of a gas (which is compressible and ruins the hydraulic pressure).