Making this spool valve on the Lego Scale is the main challenge for hydraulic control. My goal is to use only Lego parts and see where it goes from there. Once the spool valve can be made the hydraulic system will almost be complete, but for now this spool valve is the main hurdle and it will be down hill from there.

Edited November 2, 201311 yr by Boxerlego

What about internal and external leakage?

The real valves has few microns space between spool and body (sleeve) to prevent leakage between chambers. There is also a big problem with external leakage thru gaps on the shaft for control signal transfer into body to valve spool.

2 Lego valves, working together it’s a good solution, for making the same function… but the main problem - they need double force on lever, to switch it :/

Great point. I been thinking about this from the start and I came up with a idea that is based entirely on lego parts as the sliding spool valve. In order to minimize leakage between valve body components I went and sought out a proper size brass tube that can fit over a pin connector . This is where things get tricky. In order to save space with the design, I saw the pin connector in half and join the two end a main bar with 1/2 pins like this . Now this is not some thrown together part to look like a spool valve there is precise measurements here going on. Right now I will say that the complete valve travel is 10mm. That was a great question I also want to say that I got a Idea to make the control lever return to neutral or center position and hopefully the lever function wont be stiff as the pneumatic switch.

Edited November 2, 201311 yr by Boxerlego

a think a proper travel of spool is about 1 mm, maybe less, depends on whole range of dimensions, of course flow rate depends on pressure drop on valve (in simplification - supply presure).

I think this can help:

http://www.meccanotec.com/hydraulics.htm

What shear forces Lego pins/axles can survy? This can be limit of pressure for avaliable pistons areas.

I have no idea the amount of shear force the Lego pins/axles can survive. In order for the spool valve to handle the pressure I plan to put some type of glue on the connections. Also the spool valve travel is based on the valve body I plan to use. Another idea I've been thinking is to use rubber O-rings around the spool to have a better seal with the cylinder but there is no guide for the O-rings to sit on so I'm not sure about using the rubber O-rings. The spool size and the cylinder are pretty close I did some calculation and if the spool is in the exact center of the cylinder there would be a .06mm gap between the two parts.

Here is a simple mockup of the hydraulic control valve in function. The pictures show the range of travel. The Idea with the hydraulic control valve lever is to make it of thin liftarms so it can incorporate several positions to function from. Recently I've manages to minimize the complete valve travel to 8mm now.

Is it full-lego or does it have cut-up parts in it? Great job anyways

@TwentyLeggedHen: Thanks! To clear things up the Hydraulic control valve will be made mostly out of Lego parts because the integral function will be much easier to be connected up the system. It is true I have made some modification to some Lego parts such as the 1/2 pins and pin connectors but not every Lego part will need modification for example the 4L Bar is left as is.

Edit:

Also I am going to use rubber O-rings to seal the 4L bar with the valve body. If the O-rings are installed correctly the hopefully the mineral oil wont leak out. I use the small pneumatic cylinder as an example as how the control rod function will be.

Edited November 6, 201311 yr by Boxerlego

Now the hydraulic control valve is starting to take shape. What you see here is a hollowed out 2x4 brick with a hole that has a rubber grommet inserted in it to seal against the 4L bar. The control valve still needs more work but it is looking great.

sweet

Guys, why not make a four-way valve, such as pneumatic like?

would be a disc with two grooves "Sulcos" and he would switch to rotate the A B entries with P R. Sorry for English and for drawing.

That is definitely possible NORAN. But I want to say that the Hydraulic system can be divided into two categories, open-center system or a closed-center system. It is critical to incorporate both style of systems and not just employ the methodology of one.

Edited January 12, 201411 yr by Boxerlego