How does 3 "liars" in Strandbeests work?

This does not make sense to me. As far as I got it, bottom pipe is isolated from top 2 and just controls valve of the top 2 pipes. So, when air from bottle goes into left "liar" trough top 2 tubes of the right one it should just stop there. There is no way air can get to the middle one and also return to the right one to close/open it.

I hope somebody can explain this to me, because I'm starting to loose my mind a bit over this.

Edit:

I used Transistor's schematic to illustrate my frustration better:

See, in the video it's clearly seen that input air pipe goes only into A cylinder's input pipe. B and C does not receive air at all! Also it seems that B and C are closed initially, while A is open. And I can't really see any springs that you mentioned either. This is what really frustrates me. How B and C can operate if they are not even connected to air supply?

Edit:

OK, I'm feeling really embarrassed now. Are this tubes actually fused together? The problem is, Theo holds his finger over it almost all the duration of operation and it really seems that this 2 tubes are separate... In this case, Transistor's schematic is correct and my problem is solved.

• Did you draw a pneumatic schematic for the circuit? Commented Apr 5, 2020 at 9:00
• "See, in the video it's clearly seen that input air pipe goes only into A cylinder's input pipe." Nothing is very clear in the video! Commented Apr 5, 2020 at 17:32
• Agreed. This was my pitfall I guess. I edited question again can you confirm that that there is really fuse between those tubes there? That would explain the situation. Commented Apr 5, 2020 at 17:37
• I think you've got it. I was looking for that and couldn't find it. See Figure 2 in my answer. Commented Apr 5, 2020 at 18:08

Draw the schematic!

Figure 1. (a) The circuit. (b) Step 1. (c) Step 2.

The circuit relies on slight differences in timing of the various components due to differences in friction and tolerance to get started. As shown in 1(a) the circuit is just three pilot operate valves. The springs push the spools into the position shown and all valves are "open" (they will pass air). Note that before air is connected each valve is feeding through to the pilot of the next valve.

• In 1b the air has been turned on. All three pilots were being given air but B has changed over first. This cuts the pilot air for C ensuring that it stays in the open position and supplies air to the pilot of A.
• When A turns on it cuts the supply to B. B returns to the open position turning on C and cutting the supply to A.
• A returns to open and turns on B again.

The sequence should run B - A - C - B - A - C - B - A ...

Figure 2. A more physical representation of the circuit.

• Note that the air pressure on top tends to drive the valves open. This replaces the springs in my Figure 1.
• The "pilot" actuators on the bottom have a larger diameter so they will always beat the top side and be able to close the valves.
• Thanks for very detailed schematic and explanation! My issue is, however, was not really the general principle, but rather very odd pipe connections. I will edit my question using your schematic to illustrate it better. Commented Apr 5, 2020 at 17:17
• Why larger diameter piston have more power than smaller one, although pressure is same? I vaguely remember that, but can't recall clearly... It's cos in bigger piston more air molecules are striking larger area with same force than in smaller one, right? So, actually, pressure per unit area (like per 1 cm^2) in bigger piston is larger than in smaller one, but because bigger piston has bigger volume overall pressure is same? Commented Apr 7, 2020 at 5:11
• Force is pressure per unit area. Since the pressure is the same in both the actuator and the valve pistons and the actuator has the larger surface area the actuator exerts the higher force. It has nothing to do with volume. The actuator could be 50 mm long or 7 m long and the force would be the same. This can be understood without knowing anything about molecular theory. Commented Apr 7, 2020 at 6:21

one of them (consider it randomly) will overcome the others in the initial relese of pressure. instead of thinking about it as input and output I fined it more comfertable to look at it as an electronic switch- the upper tube is "+", the middle is "-" and the bottom is "info/data" (kind of like a transistor). anyway, here's a picture that I hope will help:

• Thanks, cool schematic, but I guess I didn't explained my biggest point of frustration correctly. I edited my question using schematic, so maybe it will be more clear now. Commented Apr 5, 2020 at 17:24

o.k. i think you'r just confused because they have different tops, and the tubs are hard to follow, but they are just all connected to the bottle, as i draw in my first answer

• Add to your previous answer, not worth a second. Commented Apr 7, 2020 at 9:21
• Yea, true. I noticed it after very scrupulous observations. Commented Apr 10, 2020 at 9:55