low tech concrete vibrator

[christo]

I made my own that seems to work pretty well.

Very low tech.

Took a piece of 2 foot rebar - slightly bent (aren't they all) and chucked it into my trusty old (very old) 120V plug in drill. That was trial one - it did not work well - more like an eggbeater.

Second try I cleaned up the rebar and stuck the rebar in to a 2 foot iron pipe (3/4 inch) and taped the bottom end shut.

Turn on the drill and it shakes the pipe like a mad thing. I saw lots of movement and lots of air.

Really shook me too as I had to hold on to the drill with one hand and the pipe with the other.

Wish I had that when I was filling my cores....

Christo

[Wiley]

Christo,

I'm all for DIY tools but for me in this case, one of my better purchases was one of the $79.00 Harbor Freight concrete vibrators. While not for those whose lifestyles do not include building as much of their homes, outbuildings and etc. as is practical themselves, it has proved it's worth to me and I wish I had bought one earlier. I never thought I would justify having the tool but it has removed the disapointment one has when pulling forms and finding a rock pocket where one had expected a smooth surface. To say nothing of saving the time trying to fill the pocket and make it look right.

And the price is cheap enough you can lend it to your neighbor when he's pouring his new patio slab or perhaps, after experiencing yours, his WFO.

Wiley

[james]

I just looked at the Harbor Freight web site -- how to these concrete vibrators work?
James

[Wiley]

James, Basically they work the same way Christo's home made one does: They have an eccentric or unbalanced shaft rotating inside a closed tube. The shaft is rotated /driven by a heavy duty cable (flexible shaft) connected to what is essentially a heavy duty drill motor. There's a bearing where the shaft connects to the eccentric shaft to keep it from self distructing. It's waterproof and the flexible shaft allows maneuvering the vibrating head into holes and corners.
Wiley

[james]

You stick the vibrating head into the concrete. I get it.

What about folks who are trying to cast their own vent piece. Does anyone have a strategy for vibrating concrete poured into a form?
James

[Wiley]

James, one could hold the vibrating head against the outside of the form and move it from the bottom to the top and probably get some effect. Or strap the head to the form using pipe clamp brackets in which case the effect would be to have the form and the head vibrate as one and that I expect would work better.

Paper joggers are no more than that, instead of a cylindrical head they have a flat plate. If one was going to do alot of them one could build a mold on top of such a jogger, some sand casting is done that way. A mold and a plug of styrofoam plastic; the sand is poured around the plug and vibrated. Then molten metal poured into the styrofoam. The styrofoam is vaporized and the metal fills the void. No more cope and drag boxes and ramming of sand by hand. But that's a digression.

The short answer is: Yes, I think if one is creative. Strongly affix the vibrating head to the bottom of a piece of plywood and build the mold on top of the "plate". Mount the whole on some springs or an innertube.
Wiley

[dmun]

A recent post advocated the use of a random orbit sander on the outside of the forms, maybe not as efficient, but you probably already have one.

[christo]

I think for countertops the sander is a good option. I've seen them used on the DIY tv shows that way.

My benches just did not seem to care about the sander - 450 llbs of concrete and one little sander....

Christo