From Foot Pump Cylinders To Pneumatic Robot Fighting Arm

Halfords Essentials foot pump
Halfords Essentials foot pump

[James Bruton] is well known for making robots using electric motors but he’s decided to try his hand at using pneumatics in order to make a fighting robot. The pneumatic cylinders will be used to give it two powerful punching arms. In true [James Bruton] fashion, he’s started with some experiments first, using the pneumatic cylinders from foot pumps. The cylinders he’s tried so far are taken out of single cylinder foot pumps from Halfords Essentials, costing only £6.29, around $8.11 US. That’s far cheaper than a commercial pneumatic cylinder, and perfectly adequate for this first step.

He did have to hack the cylinder a little though, besides removing it from its mounting and moving it to a DIY frame. Normally when you step down on a foot pump’s lever, you compress the cylinder, forcing air out the hose and into whatever you’re inflating. But he wanted to push air in the other direction, into the hose and into the cylinder. That would make the cylinder expand and thereby extend a robot fighting arm. And preferably that would be done rapidly and forcefully. However, a check valve at the hose outlet prevented air from entering the cylinder from the hose. So he removed the check valve. Now all he needed was a way to forcefully, and rapidly, push air into the hose.

For that he bought a solenoid activated valve on eBay, and a compressor with a 24 liter reservoir and a decent air flow rate of 180 liters per minute. The compressor added £110 ($142) to the cost of his project but that was still cheaper than the batteries he normally buys for his electric motor robots.

After working his usual CAD and 3D printing magic, he came up with an arm for the cylinder and a body that could fit two more valve activated cylinders to act as a working shoulder. A little more 3D printing and electronics, and he had 3 switches, one for each valve and cylinder. He then had the very successful results his experiment. You can see the entire R&D process in the video below, along with demonstrations of the resulting punching robot arm. We think it’s fairly intimidating for a first step.

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Computer Controlled Water Show


After seeing our recent post on Laminar Flow Nozzles, [Richard] decided to share with us his family’s summer project — a computer controlled water show (translated)!

The setup uses a Raspberry Pi at its core and a set of USB relay boards to turn the valves and lights on and off to the music. They wrote the program in Python and have posted it on their website to share.

They used common household solenoid valves because they are easy to control by relay, but unfortunately they are on/off only, so variable flow is not possible. A challenge they encountered was equalizing the water pressure — one to make sure the pump didn’t over heat when the fountains were off, and two, to equalize the height of each fountain stream. To solve this they used a pressure regulator for the pump, and organized the plumbing in such a way with additional control valves that the pressure differences were minimal.

The setup doesn’t sound like it cost that much, and now the family has their own music activated water fountain in their garden — how awesome is that! Stick around after the break to see it in action.

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