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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A Home Made Air Pump From PVC Pipe

If you need a supply of low pressure air – let’s say enough pressure to ensure a constant supply but not enough to describe as “Compressed air” with a straight face – what do you do? Many people will reach for an aquarium pump, after all that represents a readily available and relatively inexpensive source of bubbles.

But not [truebassB], instead he built his own air pump from first principles (YouTube, embedded below) using PVC pipe. It’s a straightforward design in which the cylinder is a length of pipe with a disc of flat PVC glued to its end, and the piston is fabricated from a short piece of the same tube with a section cut out to reduce its diameter. An adequate seal is achieved using a piece of rubber cut from an inner tube, and the gudgeon pin is cut from a piece of wire. The connecting rod is another longer piece of wire, and the crank is a wooden disc with an offset hole. Power comes from a DC motor taken from a dead power tool. A couple of ball check valves are used for air input and output.

The resulting pump isn’t the prettiest of pumps, and it could probably do with a bit of balancing as it rattles somewhat. But it’s a pump, and it obviously cost next-to-nothing, so that in our eyes makes it a neat build. He’s posted a video of the build which we’ve placed below the break.

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