Making a vibrator to add to a Grit Blasting Cabinet

[Bazz4CQJ]

Mods please move elsewhere if appropriate.

I bought one of the cheapy grit blast cabinets that are around for ~£100.
The floor of it is like a "square funnel" shape, intended to get all the grit to fall down to the lowest point where the pickup tube for gun is located.

Perhaps the UK climate does not help this process; the grit may not be 100.0% dry! Some modification is required to make this work better.

I've seen suggestions that adding some kind of vibrator device underneath the floor is the answer and I'm playing with a small electric motor which has an off-centre lump of metal on its rotor (to be attached under the floor). Another possibility is to put some piezo electric elements on to the floor.

Any wise insights appreciated!

B

[barrymagrec]

I would think you might have trouble getting sufficient power from Piezo devices, a loudspeaker suitably driven would do it but it would have to be completely sealed.

The off centre weight is widely used in vibrators for industry but small motors not designed for such use will not have man enough bearings to last for any length of time.

[Cobaltblue]

You could use an old mains powered orbital sander

You can usually pick those up second hand for a couple of quid.

Cheers

Mike T

[G6Tanuki]

What about a bunch of the vibratey-things used in phones to provide 'silent' notifications of incoming calls/texts?

[Bazz4CQJ]

Thanks for those comments. Of course it needs to create vibration of some amplitude, and achieving resonance might be nice
As usual, it would be nice to find something in the junk box to do this task, and I found a 12VDC electric motor, which was salvaged from a tyre inflator, so has a little umph. I attached an off-centre lead weight on the rotor, and that's certainly got it vibrating, but not quite sure how to attach it under the floor; rubber grommets? I agree it will have a limited life, but I don't use the blaster much.

I'll keep an eye open for a sander or other suitable tool when I'm next in a junk shop. I wonder what a speaker running 50Hz might do?

B

[Restoration73]

I have seen a new Cobra marine VHF transceiver. It has a "Burp" feature. When
selected a low frequency is sent at high volume to the internal plastic cone speaker
to expel any ingress of water.

[Terry_VK5TM]

Another thing to look for is an old set of electric hair clippers.

The guts of the old ones were just an AC solenoid, pretty sure that would make the floor rattle enough to get things moving.

[G.Castle]

If you end up having to buy something, and you have compressed air on tap then a little ball vibrator would work well. Several pneumatics manufacturers do them.

[joebog1]

Your idea of an out of balance weight on a motor is the right way to go. It should be rigidly mounted to the side of the chute without grommets. In the middle of the largest side of the chute works best. Stand the whole kit n caboodle, meaning the whole sandblaster on SMALL castors. The type that used to be very common on arm chairs, little steel things about 1 1/4" diameter. Going for resonance might not please the neighbours though!! A little tin box will radiate considerable sound. I have done this for exactly the same reason!! The grit ( actually carborundum in Aus. ) tends to stick in the corners and won't fall down to the pickup pipe. The motor I used was from an electric scooter, where the batteries were continually flattened to become useless.

I used the speed controller and the throttle grip to control it. An old UPS power supply transformer run in reverse made the power supply. It won't take anywhere near the current the scooter ( or bicycle ) did.

Hope this helps

Joe

[fetteler]

Originally Posted by Bazz4CQJ

..... rubber grommets?

B

Rubber grommets would only serve to isolate/decouple the source of vibrations from the cabinet floor. Whatever source of vibration you decide on it should be rigidly fixed to the thing it is intended to shake!

Steve.

PS Mike's (Cobaltblue) suggestion of an old orbital sander is a good one.

[Bazz4CQJ]

Believe it or not, the engineering prototype (as attached) is looking most promising! It's a 12V motor (on a bit of sheet metal with 4 neodymium magnets). Sticking it on the side of a PSU, at about 3V (~1A) things begin to happen and at about 4V, everything on the same shelf is starting to move .

So, the trick seems to be to have a finely variable voltage and find a resonant speed. I'll wire it up through a foot switch and, at zero cost, see how long it lasts . Some (eventual) refinement of the structural elements may be needed.

B