Vibratory Hammer: not a sex toy

by Tim Flanagan on April 20, 2009


Today, troche I learned what a vibratory hammer is. Brian Campbell of Campbell Maritime, right on Lake Union in Seattle, posted a video with accompanying explanation over on his blog. Very interesting.

So you’ll notice the big red thing hanging from the crane. That’s the hammer. You may remember from our recent video of the Horse using a drop hammer. A drop hammer is a very crude sort of technology. You basically pick up something really heavy, and drop it on top of the pile. If the pile doesn’t go, you have to either pick up something heavier, or pick the same thing up higher before you drop it. A three year old could grasp the workings of a drop hammer in about two seconds.

A vibratory hammer is another beast entirely. It’s driven by a great big hydraulic power pack, which for a hammer this big is roughly the size of a twenty foot cargo container. There’s a big hydraulic motor in the hammer, and it drives a rotor with an eccentric mass on attached, so that when it spins it shakes the bejesus out of the whole thing. At the bottom of the hammer there’s a big set of hydraulic jaws that clamp onto the pile, so that the vibration is transmitted right down the pile. There’s a lot more to it than this, and if you want I’m sure you could learn all you’d ever want to know online, but basically the vibration loosens the soil right around the pile, and the weight of the whole thing sends it sliding downwards. If you find just the right rpm to run the powerpack at you can sometimes hit the right frequency for the type of soil you’re working in, and then they really go flying down.

If you watch the video closely you’ll see the hammer revving up and down a little towards the beginning. That was me playing around to see if I couldn’t find the magic frequency. I kind of got it for a second there, I think. One other thing you may notice from the video, the pile is rotating as it goes into the ground. You can tell if you pay attention to which way the hammer’s facing as the pile drops. That’s due to the fins they welded on the tips of the pile, which you can see if you look at yesterday’s photo. The idea with those is that the pile sort of augurs it’s way into the ground, and I guess makes it a little less likely to come loose ever. And they look kind of cool too.

So that’s about all I know. I made at least half of it up too, so if it sounds fishy there’s a good reason. If you have any questions about any of this let me know and I’ll try and ask someone who might actually know something. Thanks, Brian

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1 Ross April 21, 2009 at 9:26 am

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