[TC10] Pneumatic Walker

[trekman]

I present to you my effort in this competition. This will be a pneumatic walker, powered by a separate compressor. There will be a supply going to the pneumatic valves. These will create a sequence of eight movements at four cylinders, which should be enough to lift the legs and tilt the lower body.

This is very much at development stage and will be added to until the deadline. I have a nice selection of pneumatics, which makes this contest quite appealing.

[syclone]

I have seen an eight legs pneumatic walker, but never a two legged one, will be following this topic with great interest!

[BusterHaus]

I'm building a pneumatic biped for the contest as well, although my mechanism is quite different. Are you shifting the center of gravity on the body, or just on the legs?

[grum64]

Not seen a pneumatic walker before so am very much looking forward to seeing this.

[trekman]

Hopefully the pneumatic cylinder will shift each leg at the ankle, and then I may be able to straighten the top part of the torso with another cylinder at the waist. The grey foot is the improvement with the cylinder added.

[BusterHaus]

How's your project going? I built two prototypes and I think I'll switch projects. I am not sure if the cylinders have enough force to move a battery box, a motor and a compressor, all at a reasonable speed. I thought about transforming the large weak stroke to a stronger short stroke but it will just add weight and complexity and slow down the model considerably.

There is a short video of a biped that uses a bottle filled with compressed air that seems to work, but the compressor is not on the biped:

[Imanol BB]

Finally a walker, i was expecting for a long time to see one, i first saw bucket loaders, tracked excavators and some other things, but hadn't see a walker, yet, it looks good so far, and it must be a little hard to make it only with 2 legs, but i hope you can finish it, looks promising.

[jorgeopesi]

Very impressive and very fun to build, isn´t it .

[BusterHaus]

Just to clarify, the video of the biped is not mine. Someone else built it and used a compressed air bottle to power it. My prototypes looked quite different because my collection of pneumatic cylinders is rather limited, so I had it working with only 4 cylinders. The issue is that the pump provides barely enough pressure to move the cylinders. I don't know if this is caused by the huge length of hoses I used or because my cylinders are very new and don't slide super smoothly yet, so I'm going back to square one and will figure out what each cylinder is capable of doing. It's been about 25 years since I last played with Lego pneumatics so this is a bit of a learning curve.

[trekman]

My walker is walking, and I am just working on the weight shifting at the moment. I will try and post some photos. I actually wasn't even looking at videos of previous effort before I started mine.

[trekman]

Well, I just want to let you know that I am throwing in the towel in this one.  After many weeks of frustration, I have had to admit that I have not been able to get my walker walking as I would have liked.

The largest problem was the sequencing of the functions, due to the weight shifting ankle movement.  There should be about eight movements on the valves in a complete cycle.  Each movement piston movement triggered a switch, which then caused another movement.  But whilst this was easy in theory, in the original plan, the two ports on the switch did not actually work the two ports on a cylinder. There needed to be some crossing of circuits.   As a result the walker locked up within a cycle, as the exhaust air was not exhausting properly.

I then resorted the right leg switch operating the left leg, and then the left leg switch working the right leg.  The ankle movements were added later.  This did create a cycle which worked, but not in a constant action.

 It also took some time sorting out the ankle weight shifting.  This does work, but only a short powerful stroke was required, ideally a cylinder half opening, which was impossible to achieve.  There were other issues with cylinders having minor leaks, which caused irregularities in the cycle.

Needless to say, this is much easier to achieve using an NXT, or motors and switches.

I don't give up easily, but due to work commitments, and other time factors, I have to reluctantly pull out of this one.

Thanks for your encouragement in the early stages.

 

[jono rocky]

Sorry to read you wont be able to finish it. I hope you get to one day and post it back up cause it would be interesting to see it finished.