OWI Hydraulic Arm Edge


Basic hydraulic principles learned plus great fun for everyone involved. I’m actually very pleased with this Hydraulic Arm kit. My 8-yr. old grandson and I put it together in several hours over a period of four weeks. It actually worked, and is still working just fine! I really didn’t think something that cost around $35 was going to be any good. I thought it might work for an hour or two which would still be educational for him, but the thing still works! The only oil used is to prime each cylinder a little. The rest of the fluid is actually just water. It also has a suction cup function which can pick up a cell phone or something similar.

The instructions for this kit are the clearest I’ve ever seen. They have thought out all the mistakes people will probably make, and address them before you get into trouble. The instruction book is about 85 pages!


Huge score for doing something fun with him that also teaches him something.

I would have to give it 9 out of ten stars.

He insisted on shooting this video when we were done.

The Idea Of Hydraulics

“Pascal’s Principle”:  “A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid.”

This is why, when you stomp on your brakes, all four of your wheels lock up and bring you to a stop.

Pascal’s Principle applies to liquids and gases. A long train stops by using air brakes.

There was also a “barrel bursting” experiment where Pascal supposedly attached a very long tube to a barrel, climbed a high ladder, and added water to the tube filling the barrel. The weight of the water in the tube being added to the water already in the barrel was so great, it actually burst the wooden barrel apart!

This is why divers have to be careful. The deeper underwater you go, the more pressure there is on your body.

See Wikipedia for more.

The Edge Hydraulic Arm

This educational kit build utilizes pistons being pushed through cylinders. The force applied by the levers is transmitted through the cylinders, and the long tubes, and is strong enough to force the relatively large and heavy arm to move a long way from the lever without any loss of force.

I think the water molecules are connected which is why you can control the Arm by pushing as well as pulling. Any physicists out there want to help explain this thing?

We are working on “Snap Circuits” right now, and will be doing other educational projects in the future. Sign up for email updates if you like.

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