I was reading through The Unofficial LEGO Technic Builder's Guide By: Paweł "Sariel" Kmieć and on "page 113" he mentions converting the pneumatic cylinders to hydraulics ones by replacing the air with liquid "mineral oil to be exact". It is a small section on the thought on hydraulic cylinders and I feel it can be achievable. If you have the book read the section. Do you think it is possible? and if not why?

Now here is some information about the basic principles of the hydraulic systems and the components that make up the hydraulic system. Now there are two type of hydraulic systems open-center and closed-center systems. The LEGO pneumatic system is naturally working as a closed-center system begin the pump/compressor is able to rest and stop pumping air/fluid in to the system. A open-center system has the fluid flowing all the time and uses a valve to revert the fluid back in to the reservoir.

If you were to put pressurized liquid in the pneumatic system

to the "valves with the control lever" every time you move the control lever side to side. This would be the only option to put the fluid back in the reservoir if you were to use the official valves. Now the old distribution block could be used as a possible return to the reservoir if you connected the middle up to the left or right on the "valves with the control lever" and use the center as a return to the reservoir the left side on the old distribution block will be the main pump and the right will be the pressure side. (Note: your going haft to runs the new valves backwards if you don't want a fountain.

The reservoir would definitely be not official LEGO construction. You will need a outlet to the pump at the bottom and a inlet at the top so the fluid can return back to the reservoir. Also the reservoir will need a vent to release pressure that could be created inside.

The accumulator would be probably not be needed for the Unofficial hydraulic system because were not using very much energy to work with and smoothing the system out is not critical here. Now what the accumulator does is it acts as a backup for the pump in the event of a pump failure. The accumulator stores energy and release the energy back in to the hydraulic system to keep the pressure up on hydraulicassisted devices in events of an emergency.

There are many types of hydraulic pumps. Most of them are positive displacement vane or gear style pumps that can also be driven as a motor when fluid is forced through it; However, The plunger pump style that LEGO has developed is not often used in hydraulic systems but it still could work here.

There are many types of valves also. Hydraulic pressure control valves are important to limit the maximum working specific pressure in the system or in a specific section. Hydraulic pressure relief valves which drops the pressure in the system. Then directional control valves that direct the flow of the fluid in the system.

The Hydraulic Line is probably the most involving and challenging part to do. For starts couplings would need to be required on the hydraulic lines to secure them on the fittings to prevent hose separation.

-BL

It is quite possible. But it wouldn't be leak-free, and cause one big mess. Since fluids have more density, it should leak less than an air-filled system though.

Edited May 6, 201311 yr by Lost_In_Noise

This is all possible using 100% Lego. take a boat hull or something similar, fill it with fluid and submerge the motor pump (not the motor!) in it along with all the valves. Have levers or shafts going to all the valves and the pump so you can operate them. The motor pump will suck in fluid from the outside just as it sucks in air and the valve will vent the fluid back into the tank in which they are submerged. I have done some testing with this and have yet to be able to brake of damage anything doing this. The only problem is that sometimes fluid can leak from the top end of a pneumatic cylinder, if that happens swap it for another, some cylinders leak, others don't. I love the hydraulic system, you cannot get much more authentic. This isn't any more powerful than pneumatics tho as in both cases you are limited to what pressure the hoses will pop off at. I highly recommend a built in pressure limiter to prevent the hoses popping off. Still it's very powerful tho. You do get instant movements and presice control but a well designed pneumatic system can do that pretty well anyway. Hydraulics are better on the whole and not that difficult really, but so far I haven't had pneumatics not do what I want so haven't yet needed to risk soaking the carpet in oil in a MOC. But we have the technology, hydraulics are not only possible, but not that difficult and works as well as if the parts were designed to work with a water like fluid.

If you do some searching you will find some older threads on this very topic. It has been discussed in detail and there are even examples from people who have tried it.

I've actually made my own custom hydraulic actuator out of standard bricks. It was cool, but also kind of worthless.

2 years ago I have tried to build a hydraulic system as well. You can see my results here:

http://www.eurobrick...439#entry913070

Sadly I'm not MOCing anymore as my new job doesn't give me enough free time for yet another activity.

So I come here every few months to see what great new MOCs have been created while I was working.

Let's see what you can do with these Lego hydraulics!