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Homemade Internal Concrete Vibrator
This vibrator is little more than a die grinder which drives an off-centered weight.
It uses off-the-shelf router bearings to bracket the off-centered weight inside
a short piece of metal pipe (I used electrical conduit). To provide the necessary
flexibility in the center of the device, it employs a short piece of wire cable soldered
into the ends of two 1/4" rods (one solid, one threaded). The image to the right shows the
nearly completed vibrator. In it one can see the previously discussed
silicon-impregnated cloth sleeve.
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List of Required Items
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A pnuematic die grinder:
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if you don't already have one, these go for
roughly $20 and up; if you want to wait for something to go on sale, getting one
for < $20 is not unreasonable. I once picked one
up for only $10 at Harbor Freight
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1/4-inch rod (threaded & non-threaded) :
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You can pick this stuff
at a the local hardware store (big-box or small-box). You'll only need about 1 foot
of each. Strictly speaking, you can get by with only the threaded, but I had some
of each laying around so that is what I used. You could also get by with solid
rod too, but then you would need a 1/4" die in order to create the threads needed
for the nuts used to lock everything in place.
Finally, you don't have to use 1/4" all-thread for the off-centered weight. Any size
will do as long as you select the appropriate bearings and sleeve (see items 3 and 4)
for the size you choose.
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router bearings (two) :
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these come in lots of different combinations of outer
diameter (OD) and inner diameter (ID). For this project I used an OD of 5/8" and an
ID of 1/4". I'm lucky enough to have a Grizzly outlet just a few miles away, which is
where I picked up the ones I used.
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metal sleeve :
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Once you've assembled the off-centered weight on the threaded rod, it needs to be housed inside
a metal cylinder. I was trying to keep the O.D. as small as possible, so I used a piece of electrical
conduit from my scrap pile. A thicker wall would be safer, so if your application doesn't really
need a small O.D., you might try using a piece of galvanized pipe.
I put a plug of "5-minute" epoxy in the open end of the sleeve. To help guard
against it loosening over time, drill a series of holes around the perimeter
of the sleeve for the epoxy to fill.
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1/8th-inch steel cable :
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You'll need about 1 to 1½ inches. Drill a hole into each end of the rods big enough for the
cable to slip into relatively well, then fire up your torch and solder the cable into each rod.
Resist the temptation to use more than an inch or two of cable. This device will run
at several thousand rpm and anything other than the off-centered weight which
is "out-of-round" could have a tendency to undermine its operation.
- flexible sleeve :
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In order to maintain flexibility of the off-centered weight, it is recommended that
one make a water-tight, flexible sleeve using the technique outlined in the page which
shows how to make a silicon-impregnated cloth tube. There might be
other alternatives, but this is one approach that seems to work quite well.
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short-length of pipe :
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I used a 3-inch long 1/4" pipe nipple for the off-centered weight. Just grind away
about half of it, leaving it intact at each end. There is nothing sacrosanct about this.
You just need a hunk of something you can sandwich between the nuts and bearings
that is sufficiently heavy and off-center so that it will set up a nice vibration when
you give the die grinder plenty of "throttle".
TOP
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This vibrator is little more than a die grinder which drives an off-centered weight.
It uses off-the-shelf router bearings to bracket the off-centered weight inside
a short piece of metal pipe (I used electrical conduit). To provide the necessary
flexibility in the center of the device, it employs a short piece of wire cable soldered
into the ends of two 1/4" rods (one solid, one threaded). The image to the right shows the
nearly completed vibrator. In it one can see the previously discussed
silicon-impregnated cloth sleeve.
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